Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs

Pull btrfs update from Chris Mason:
"A big set of fixes and features.

In terms of line count, most of the code comes from Stefan, who added
the ability to replace a single drive in place. This is different
from how btrfs normally replaces drives, and is much much much faster.

Josef is plowing through our synchronous write performance. This pull
request does not include the DIO_OWN_WAITING patch that was discussed
on the list, but it has a number of other improvements to cut down our
latencies and CPU time during fsync/O_DIRECT writes.

Miao Xie has a big series of fixes and is spreading out ordered
operations over more CPUs. This improves performance and reduces
contention.

I've put in fixes for error handling around hash collisions. These
are going back to individual stable kernels as I test against them.

Otherwise we have a lot of fixes and cleanups, thanks everyone!
raid5/6 is being rebased against the device replacement code. I'll
have it posted this Friday along with a nice series of benchmarks."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs: (115 commits)
Btrfs: fix a bug of per-file nocow
Btrfs: fix hash overflow handling
Btrfs: don't take inode delalloc mutex if we're a free space inode
Btrfs: fix autodefrag and umount lockup
Btrfs: fix permissions of empty files not affected by umask
Btrfs: put raid properties into global table
Btrfs: fix BUG() in scrub when first superblock reading gives EIO
Btrfs: do not call file_update_time in aio_write
Btrfs: only unlock and relock if we have to
Btrfs: use tokens where we can in the tree log
Btrfs: optimize leaf_space_used
Btrfs: don't memset new tokens
Btrfs: only clear dirty on the buffer if it is marked as dirty
Btrfs: move checks in set_page_dirty under DEBUG
Btrfs: log changed inodes based on the extent map tree
Btrfs: add path->really_keep_locks
Btrfs: do not mark ems as prealloc if we are writing to them
Btrfs: keep track of the extents original block length
Btrfs: inline csums if we're fsyncing
Btrfs: don't bother copying if we're only logging the inode
...

fs/btrfs/Makefile

···
 	   extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \
 	   export.o tree-log.o free-space-cache.o zlib.o lzo.o \
 	   compression.o delayed-ref.o relocation.o delayed-inode.o scrub.o \
-	   reada.o backref.o ulist.o qgroup.o send.o
+	   reada.o backref.o ulist.o qgroup.o send.o dev-replace.o
 
 btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
 btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o

fs/btrfs/acl.c

···
 			ret = posix_acl_equiv_mode(acl, &inode->i_mode);
 			if (ret < 0)
 				return ret;
+			if (ret == 0)
+				acl = NULL;
 		}
 		ret = 0;
 		break;

fs/btrfs/backref.c

···
 		     pos2 = n2, n2 = pos2->next) {
 			struct __prelim_ref *ref2;
 			struct __prelim_ref *xchg;
+			struct extent_inode_elem *eie;
 
 			ref2 = list_entry(pos2, struct __prelim_ref, list);
 
···
 					ref1 = ref2;
 					ref2 = xchg;
 				}
-				ref1->count += ref2->count;
 			} else {
 				if (ref1->parent != ref2->parent)
 					continue;
-				ref1->count += ref2->count;
 			}
+
+			eie = ref1->inode_list;
+			while (eie && eie->next)
+				eie = eie->next;
+			if (eie)
+				eie->next = ref2->inode_list;
+			else
+				ref1->inode_list = ref2->inode_list;
+			ref1->count += ref2->count;
+
 			list_del(&ref2->list);
 			kfree(ref2);
 		}
···
 	while (!list_empty(&prefs)) {
 		ref = list_first_entry(&prefs, struct __prelim_ref, list);
 		list_del(&ref->list);
-		if (ref->count < 0)
-			WARN_ON(1);
+		WARN_ON(ref->count < 0);
 		if (ref->count && ref->root_id && ref->parent == 0) {
 			/* no parent == root of tree */
 			ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);

fs/btrfs/btrfs_inode.h

···
 #define BTRFS_INODE_HAS_ORPHAN_ITEM		5
 #define BTRFS_INODE_HAS_ASYNC_EXTENT		6
 #define BTRFS_INODE_NEEDS_FULL_SYNC		7
+#define BTRFS_INODE_COPY_EVERYTHING		8
 
 /* in memory btrfs inode */
 struct btrfs_inode {
···
 	struct rb_node rb_node;
 
 	unsigned long runtime_flags;
+
+	/* Keep track of who's O_SYNC/fsycing currently */
+	atomic_t sync_writers;
 
 	/* full 64 bit generation number, struct vfs_inode doesn't have a big
 	 * enough field for this.

fs/btrfs/check-integrity.c

···
 	unsigned int never_written:1;	/* block was added because it was
 					 * referenced, not because it was
 					 * written */
-	unsigned int mirror_num:2;	/* large enough to hold
+	unsigned int mirror_num;	/* large enough to hold
 					 * BTRFS_SUPER_MIRROR_MAX */
 	struct btrfsic_dev_state *dev_state;
 	u64 dev_bytenr;		/* key, physical byte num on disk */
···
 		}
 
 		num_copies =
-		    btrfs_num_copies(&state->root->fs_info->mapping_tree,
+		    btrfs_num_copies(state->root->fs_info,
 				     next_bytenr, state->metablock_size);
 		if (state->print_mask & BTRFSIC_PRINT_MASK_NUM_COPIES)
 			printk(KERN_INFO "num_copies(log_bytenr=%llu) = %d\n",
···
 		}
 
 		num_copies =
-		    btrfs_num_copies(&state->root->fs_info->mapping_tree,
+		    btrfs_num_copies(state->root->fs_info,
 				     next_bytenr, state->metablock_size);
 		if (state->print_mask & BTRFSIC_PRINT_MASK_NUM_COPIES)
 			printk(KERN_INFO "num_copies(log_bytenr=%llu) = %d\n",
···
 	*next_blockp = NULL;
 	if (0 == *num_copiesp) {
 		*num_copiesp =
-		    btrfs_num_copies(&state->root->fs_info->mapping_tree,
+		    btrfs_num_copies(state->root->fs_info,
 				     next_bytenr, state->metablock_size);
 		if (state->print_mask & BTRFSIC_PRINT_MASK_NUM_COPIES)
 			printk(KERN_INFO "num_copies(log_bytenr=%llu) = %d\n",
···
 			chunk_len = num_bytes;
 
 		num_copies =
-		    btrfs_num_copies(&state->root->fs_info->mapping_tree,
+		    btrfs_num_copies(state->root->fs_info,
 				     next_bytenr, state->datablock_size);
 		if (state->print_mask & BTRFSIC_PRINT_MASK_NUM_COPIES)
 			printk(KERN_INFO "num_copies(log_bytenr=%llu) = %d\n",
···
 	struct btrfs_device *device;
 
 	length = len;
-	ret = btrfs_map_block(&state->root->fs_info->mapping_tree, READ,
+	ret = btrfs_map_block(state->root->fs_info, READ,
 			      bytenr, &length, &multi, mirror_num);
+
+	if (ret) {
+		block_ctx_out->start = 0;
+		block_ctx_out->dev_bytenr = 0;
+		block_ctx_out->len = 0;
+		block_ctx_out->dev = NULL;
+		block_ctx_out->datav = NULL;
+		block_ctx_out->pagev = NULL;
+		block_ctx_out->mem_to_free = NULL;
+
+		return ret;
+	}
 
 	device = multi->stripes[0].dev;
 	block_ctx_out->dev = btrfsic_dev_state_lookup(device->bdev);
···
 	block_ctx_out->pagev = NULL;
 	block_ctx_out->mem_to_free = NULL;
 
-	if (0 == ret)
-		kfree(multi);
+	kfree(multi);
 	if (NULL == block_ctx_out->dev) {
 		ret = -ENXIO;
 		printk(KERN_INFO "btrfsic: error, cannot lookup dev (#1)!\n");
···
 		}
 
 		num_copies =
-		    btrfs_num_copies(&state->root->fs_info->mapping_tree,
+		    btrfs_num_copies(state->root->fs_info,
 				     next_bytenr, BTRFS_SUPER_INFO_SIZE);
 		if (state->print_mask & BTRFSIC_PRINT_MASK_NUM_COPIES)
 			printk(KERN_INFO "num_copies(log_bytenr=%llu) = %d\n",
···
 	struct btrfsic_block_data_ctx block_ctx;
 	int match = 0;
 
-	num_copies = btrfs_num_copies(&state->root->fs_info->mapping_tree,
+	num_copies = btrfs_num_copies(state->root->fs_info,
 				      bytenr, state->metablock_size);
 
 	for (mirror_num = 1; mirror_num <= num_copies; mirror_num++) {

fs/btrfs/compression.c

···
 
 			ret = btrfs_map_bio(root, READ, comp_bio,
 					    mirror_num, 0);
-			BUG_ON(ret); /* -ENOMEM */
+			if (ret)
+				bio_endio(comp_bio, ret);
 
 			bio_put(comp_bio);
 
···
 	}
 
 	ret = btrfs_map_bio(root, READ, comp_bio, mirror_num, 0);
-	BUG_ON(ret); /* -ENOMEM */
+	if (ret)
+		bio_endio(comp_bio, ret);
 
 	bio_put(comp_bio);
 	return 0;

fs/btrfs/ctree.c

···
 			      struct extent_buffer *dst_buf,
 			      struct extent_buffer *src_buf);
 static void del_ptr(struct btrfs_trans_handle *trans, struct btrfs_root *root,
-		    struct btrfs_path *path, int level, int slot,
-		    int tree_mod_log);
+		    struct btrfs_path *path, int level, int slot);
 static void tree_mod_log_free_eb(struct btrfs_fs_info *fs_info,
 				 struct extent_buffer *eb);
 struct extent_buffer *read_old_tree_block(struct btrfs_root *root, u64 bytenr,
···
 
 static noinline void
 tree_mod_log_set_node_key(struct btrfs_fs_info *fs_info,
-			  struct extent_buffer *eb,
-			  struct btrfs_disk_key *disk_key, int slot, int atomic)
+			  struct extent_buffer *eb, int slot, int atomic)
 {
 	int ret;
 
···
 		switch (tm->op) {
 		case MOD_LOG_KEY_REMOVE_WHILE_FREEING:
 			BUG_ON(tm->slot < n);
-		case MOD_LOG_KEY_REMOVE_WHILE_MOVING:
 		case MOD_LOG_KEY_REMOVE:
+			n++;
+		case MOD_LOG_KEY_REMOVE_WHILE_MOVING:
 			btrfs_set_node_key(eb, &tm->key, tm->slot);
 			btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr);
 			btrfs_set_node_ptr_generation(eb, tm->slot,
 						      tm->generation);
-			n++;
 			break;
 		case MOD_LOG_KEY_REPLACE:
 			BUG_ON(tm->slot >= n);
···
 	u64 search_start;
 	int ret;
 
-	if (trans->transaction != root->fs_info->running_transaction) {
-		printk(KERN_CRIT "trans %llu running %llu\n",
+	if (trans->transaction != root->fs_info->running_transaction)
+		WARN(1, KERN_CRIT "trans %llu running %llu\n",
 		       (unsigned long long)trans->transid,
 		       (unsigned long long)
 		       root->fs_info->running_transaction->transid);
-		WARN_ON(1);
-	}
-	if (trans->transid != root->fs_info->generation) {
-		printk(KERN_CRIT "trans %llu running %llu\n",
+
+	if (trans->transid != root->fs_info->generation)
+		WARN(1, KERN_CRIT "trans %llu running %llu\n",
 		       (unsigned long long)trans->transid,
 		       (unsigned long long)root->fs_info->generation);
-		WARN_ON(1);
-	}
 
 	if (!should_cow_block(trans, root, buf)) {
 		*cow_ret = buf;
···
 	if (cache_only && parent_level != 1)
 		return 0;
 
-	if (trans->transaction != root->fs_info->running_transaction)
-		WARN_ON(1);
-	if (trans->transid != root->fs_info->generation)
-		WARN_ON(1);
+	WARN_ON(trans->transaction != root->fs_info->running_transaction);
+	WARN_ON(trans->transid != root->fs_info->generation);
 
 	parent_nritems = btrfs_header_nritems(parent);
 	blocksize = btrfs_level_size(root, parent_level - 1);
···
 		if (btrfs_header_nritems(right) == 0) {
 			clean_tree_block(trans, root, right);
 			btrfs_tree_unlock(right);
-			del_ptr(trans, root, path, level + 1, pslot + 1, 1);
+			del_ptr(trans, root, path, level + 1, pslot + 1);
 			root_sub_used(root, right->len);
 			btrfs_free_tree_block(trans, root, right, 0, 1);
 			free_extent_buffer_stale(right);
···
 			struct btrfs_disk_key right_key;
 			btrfs_node_key(right, &right_key, 0);
 			tree_mod_log_set_node_key(root->fs_info, parent,
-						  &right_key, pslot + 1, 0);
+						  pslot + 1, 0);
 			btrfs_set_node_key(parent, &right_key, pslot + 1);
 			btrfs_mark_buffer_dirty(parent);
 		}
···
 	if (btrfs_header_nritems(mid) == 0) {
 		clean_tree_block(trans, root, mid);
 		btrfs_tree_unlock(mid);
-		del_ptr(trans, root, path, level + 1, pslot, 1);
+		del_ptr(trans, root, path, level + 1, pslot);
 		root_sub_used(root, mid->len);
 		btrfs_free_tree_block(trans, root, mid, 0, 1);
 		free_extent_buffer_stale(mid);
···
 		/* update the parent key to reflect our changes */
 		struct btrfs_disk_key mid_key;
 		btrfs_node_key(mid, &mid_key, 0);
-		tree_mod_log_set_node_key(root->fs_info, parent, &mid_key,
+		tree_mod_log_set_node_key(root->fs_info, parent,
 					  pslot, 0);
 		btrfs_set_node_key(parent, &mid_key, pslot);
 		btrfs_mark_buffer_dirty(parent);
···
 			orig_slot += left_nr;
 			btrfs_node_key(mid, &disk_key, 0);
 			tree_mod_log_set_node_key(root->fs_info, parent,
-						  &disk_key, pslot, 0);
+						  pslot, 0);
 			btrfs_set_node_key(parent, &disk_key, pslot);
 			btrfs_mark_buffer_dirty(parent);
 			if (btrfs_header_nritems(left) > orig_slot) {
···
 
 			btrfs_node_key(right, &disk_key, 0);
 			tree_mod_log_set_node_key(root->fs_info, parent,
-						  &disk_key, pslot + 1, 0);
+						  pslot + 1, 0);
 			btrfs_set_node_key(parent, &disk_key, pslot + 1);
 			btrfs_mark_buffer_dirty(parent);
 
···
 	int no_skips = 0;
 	struct extent_buffer *t;
 
+	if (path->really_keep_locks)
+		return;
+
 	for (i = level; i < BTRFS_MAX_LEVEL; i++) {
 		if (!path->nodes[i])
 			break;
···
 {
 	int i;
 
-	if (path->keep_locks)
+	if (path->keep_locks || path->really_keep_locks)
 		return;
 
 	for (i = level; i < BTRFS_MAX_LEVEL; i++) {
···
 	if (!cow)
 		write_lock_level = -1;
 
-	if (cow && (p->keep_locks || p->lowest_level))
+	if (cow && (p->really_keep_locks || p->keep_locks || p->lowest_level))
 		write_lock_level = BTRFS_MAX_LEVEL;
 
 	min_write_lock_level = write_lock_level;
···
 			 * must have write locks on this node and the
 			 * parent
 			 */
-			if (level + 1 > write_lock_level) {
+			if (level > write_lock_level ||
+			    (level + 1 > write_lock_level &&
+			    level + 1 < BTRFS_MAX_LEVEL &&
+			    p->nodes[level + 1])) {
 				write_lock_level = level + 1;
 				btrfs_release_path(p);
 				goto again;
···
 		if (!path->nodes[i])
 			break;
 		t = path->nodes[i];
-		tree_mod_log_set_node_key(root->fs_info, t, key, tslot, 1);
+		tree_mod_log_set_node_key(root->fs_info, t, tslot, 1);
 		btrfs_set_node_key(t, key, tslot);
 		btrfs_mark_buffer_dirty(path->nodes[i]);
 		if (tslot != 0)
···
  */
 static int leaf_space_used(struct extent_buffer *l, int start, int nr)
 {
+	struct btrfs_item *start_item;
+	struct btrfs_item *end_item;
+	struct btrfs_map_token token;
 	int data_len;
 	int nritems = btrfs_header_nritems(l);
 	int end = min(nritems, start + nr) - 1;
 
 	if (!nr)
 		return 0;
-	data_len = btrfs_item_end_nr(l, start);
-	data_len = data_len - btrfs_item_offset_nr(l, end);
+	btrfs_init_map_token(&token);
+	start_item = btrfs_item_nr(l, start);
+	end_item = btrfs_item_nr(l, end);
+	data_len = btrfs_token_item_offset(l, start_item, &token) +
+		btrfs_token_item_size(l, start_item, &token);
+	data_len = data_len - btrfs_token_item_offset(l, end_item, &token);
 	data_len += sizeof(struct btrfs_item) * nr;
 	WARN_ON(data_len < 0);
 	return data_len;
···
 	if (push_items == 0)
 		goto out_unlock;
 
-	if (!empty && push_items == left_nritems)
-		WARN_ON(1);
+	WARN_ON(!empty && push_items == left_nritems);
 
 	/* push left to right */
 	right_nritems = btrfs_header_nritems(right);
···
 	btrfs_set_header_nritems(left, old_left_nritems + push_items);
 
 	/* fixup right node */
-	if (push_items > right_nritems) {
-		printk(KERN_CRIT "push items %d nr %u\n", push_items,
+	if (push_items > right_nritems)
+		WARN(1, KERN_CRIT "push items %d nr %u\n", push_items,
 		       right_nritems);
-		WARN_ON(1);
-	}
 
 	if (push_items < right_nritems) {
 		push_space = btrfs_item_offset_nr(right, push_items - 1) -
···
  * empty a node.
  */
 static void del_ptr(struct btrfs_trans_handle *trans, struct btrfs_root *root,
-		    struct btrfs_path *path, int level, int slot,
-		    int tree_mod_log)
+		    struct btrfs_path *path, int level, int slot)
 {
 	struct extent_buffer *parent = path->nodes[level];
 	u32 nritems;
 	int ret;
 
+	if (level) {
+		ret = tree_mod_log_insert_key(root->fs_info, parent, slot,
+					      MOD_LOG_KEY_REMOVE);
+		BUG_ON(ret < 0);
+	}
+
 	nritems = btrfs_header_nritems(parent);
 	if (slot != nritems - 1) {
-		if (tree_mod_log && level)
+		if (level)
 			tree_mod_log_eb_move(root->fs_info, parent, slot,
 					     slot + 1, nritems - slot - 1);
 		memmove_extent_buffer(parent,
···
 			      btrfs_node_key_ptr_offset(slot + 1),
 			      sizeof(struct btrfs_key_ptr) *
 			      (nritems - slot - 1));
-	} else if (tree_mod_log && level) {
-		ret = tree_mod_log_insert_key(root->fs_info, parent, slot,
-					      MOD_LOG_KEY_REMOVE);
-		BUG_ON(ret < 0);
 	}
 
 	nritems--;
···
 				    struct extent_buffer *leaf)
 {
 	WARN_ON(btrfs_header_generation(leaf) != trans->transid);
-	del_ptr(trans, root, path, 1, path->slots[1], 1);
+	del_ptr(trans, root, path, 1, path->slots[1]);
 
 	/*
 	 * btrfs_free_extent is expensive, we want to make sure we
···
 	right_path->search_commit_root = 1;
 	right_path->skip_locking = 1;
 
-	spin_lock(&left_root->root_times_lock);
+	spin_lock(&left_root->root_item_lock);
 	left_start_ctransid = btrfs_root_ctransid(&left_root->root_item);
-	spin_unlock(&left_root->root_times_lock);
+	spin_unlock(&left_root->root_item_lock);
 
-	spin_lock(&right_root->root_times_lock);
+	spin_lock(&right_root->root_item_lock);
 	right_start_ctransid = btrfs_root_ctransid(&right_root->root_item);
-	spin_unlock(&right_root->root_times_lock);
+	spin_unlock(&right_root->root_item_lock);
 
 	trans = btrfs_join_transaction(left_root);
 	if (IS_ERR(trans)) {
···
 				goto out;
 			}
 
-			spin_lock(&left_root->root_times_lock);
+			spin_lock(&left_root->root_item_lock);
 			ctransid = btrfs_root_ctransid(&left_root->root_item);
-			spin_unlock(&left_root->root_times_lock);
+			spin_unlock(&left_root->root_item_lock);
 			if (ctransid != left_start_ctransid)
 				left_start_ctransid = 0;
 
-			spin_lock(&right_root->root_times_lock);
+			spin_lock(&right_root->root_item_lock);
 			ctransid = btrfs_root_ctransid(&right_root->root_item);
-			spin_unlock(&right_root->root_times_lock);
+			spin_unlock(&right_root->root_item_lock);
 			if (ctransid != right_start_ctransid)
 				right_start_ctransid = 0;
 
···
 int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
 {
 	return btrfs_next_old_leaf(root, path, 0);
+}
+
+/* Release the path up to but not including the given level */
+static void btrfs_release_level(struct btrfs_path *path, int level)
+{
+	int i;
+
+	for (i = 0; i < level; i++) {
+		path->slots[i] = 0;
+		if (!path->nodes[i])
+			continue;
+		if (path->locks[i]) {
+			btrfs_tree_unlock_rw(path->nodes[i], path->locks[i]);
+			path->locks[i] = 0;
+		}
+		free_extent_buffer(path->nodes[i]);
+		path->nodes[i] = NULL;
+	}
+}
+
+/*
+ * This function assumes 2 things
+ *
+ * 1) You are using path->keep_locks
+ * 2) You are not inserting items.
+ *
+ * If either of these are not true do not use this function. If you need a next
+ * leaf with either of these not being true then this function can be easily
+ * adapted to do that, but at the moment these are the limitations.
+ */
+int btrfs_next_leaf_write(struct btrfs_trans_handle *trans,
+			  struct btrfs_root *root, struct btrfs_path *path,
+			  int del)
+{
+	struct extent_buffer *b;
+	struct btrfs_key key;
+	u32 nritems;
+	int level = 1;
+	int slot;
+	int ret = 1;
+	int write_lock_level = BTRFS_MAX_LEVEL;
+	int ins_len = del ? -1 : 0;
+
+	WARN_ON(!(path->keep_locks || path->really_keep_locks));
+
+	nritems = btrfs_header_nritems(path->nodes[0]);
+	btrfs_item_key_to_cpu(path->nodes[0], &key, nritems - 1);
+
+	while (path->nodes[level]) {
+		nritems = btrfs_header_nritems(path->nodes[level]);
+		if (!(path->locks[level] & BTRFS_WRITE_LOCK)) {
+search:
+			btrfs_release_path(path);
+			ret = btrfs_search_slot(trans, root, &key, path,
+						ins_len, 1);
+			if (ret < 0)
+				goto out;
+			level = 1;
+			continue;
+		}
+
+		if (path->slots[level] >= nritems - 1) {
+			level++;
+			continue;
+		}
+
+		btrfs_release_level(path, level);
+		break;
+	}
+
+	if (!path->nodes[level]) {
+		ret = 1;
+		goto out;
+	}
+
+	path->slots[level]++;
+	b = path->nodes[level];
+
+	while (b) {
+		level = btrfs_header_level(b);
+
+		if (!should_cow_block(trans, root, b))
+			goto cow_done;
+
+		btrfs_set_path_blocking(path);
+		ret = btrfs_cow_block(trans, root, b,
+				      path->nodes[level + 1],
+				      path->slots[level + 1], &b);
+		if (ret)
+			goto out;
+cow_done:
+		path->nodes[level] = b;
+		btrfs_clear_path_blocking(path, NULL, 0);
+		if (level != 0) {
+			ret = setup_nodes_for_search(trans, root, path, b,
+						     level, ins_len,
+						     &write_lock_level);
+			if (ret == -EAGAIN)
+				goto search;
+			if (ret)
+				goto out;
+
+			b = path->nodes[level];
+			slot = path->slots[level];
+
+			ret = read_block_for_search(trans, root, path,
+						    &b, level, slot, &key, 0);
+			if (ret == -EAGAIN)
+				goto search;
+			if (ret)
+				goto out;
+			level = btrfs_header_level(b);
+			if (!btrfs_try_tree_write_lock(b)) {
+				btrfs_set_path_blocking(path);
+				btrfs_tree_lock(b);
+				btrfs_clear_path_blocking(path, b,
+							  BTRFS_WRITE_LOCK);
+			}
+			path->locks[level] = BTRFS_WRITE_LOCK;
+			path->nodes[level] = b;
+			path->slots[level] = 0;
+		} else {
+			path->slots[level] = 0;
+			ret = 0;
+			break;
+		}
+	}
+
+out:
+	if (ret)
+		btrfs_release_path(path);
+
+	return ret;
 }
 
 int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path,

fs/btrfs/ctree.h

···
 
 #define BTRFS_MAGIC "_BHRfS_M"
 
-#define BTRFS_MAX_MIRRORS 2
+#define BTRFS_MAX_MIRRORS 3
 
 #define BTRFS_MAX_LEVEL 8
 
···
 
 #define BTRFS_EMPTY_SUBVOL_DIR_OBJECTID 2
 
+#define BTRFS_DEV_REPLACE_DEVID 0
+
 /*
  * the max metadata block size.  This limit is somewhat artificial,
  * but the memmove costs go through the roof for larger blocks.
···
 
 /* four bytes for CRC32 */
 #define BTRFS_EMPTY_DIR_SIZE 0
+
+/* spefic to btrfs_map_block(), therefore not in include/linux/blk_types.h */
+#define REQ_GET_READ_MIRRORS	(1 << 30)
 
 #define BTRFS_FT_UNKNOWN	0
 #define BTRFS_FT_REG_FILE	1
···
 	unsigned int skip_locking:1;
 	unsigned int leave_spinning:1;
 	unsigned int search_commit_root:1;
+	unsigned int really_keep_locks:1;
 };
 
 /*
···
 	 * the existing values unchanged
 	 */
 	__le64 values[BTRFS_DEV_STAT_VALUES_MAX];
+} __attribute__ ((__packed__));
+
+#define BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_ALWAYS	0
+#define BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_AVOID	1
+#define BTRFS_DEV_REPLACE_ITEM_STATE_NEVER_STARTED	0
+#define BTRFS_DEV_REPLACE_ITEM_STATE_STARTED		1
+#define BTRFS_DEV_REPLACE_ITEM_STATE_SUSPENDED		2
+#define BTRFS_DEV_REPLACE_ITEM_STATE_FINISHED		3
+#define BTRFS_DEV_REPLACE_ITEM_STATE_CANCELED		4
+
+struct btrfs_dev_replace {
+	u64 replace_state;	/* see #define above */
+	u64 time_started;	/* seconds since 1-Jan-1970 */
+	u64 time_stopped;	/* seconds since 1-Jan-1970 */
+	atomic64_t num_write_errors;
+	atomic64_t num_uncorrectable_read_errors;
+
+	u64 cursor_left;
+	u64 committed_cursor_left;
+	u64 cursor_left_last_write_of_item;
+	u64 cursor_right;
+
+	u64 cont_reading_from_srcdev_mode;	/* see #define above */
+
+	int is_valid;
+	int item_needs_writeback;
+	struct btrfs_device *srcdev;
+	struct btrfs_device *tgtdev;
+
+	pid_t lock_owner;
+	atomic_t nesting_level;
+	struct mutex lock_finishing_cancel_unmount;
+	struct mutex lock_management_lock;
+	struct mutex lock;
+
+	struct btrfs_scrub_progress scrub_progress;
+};
+
+struct btrfs_dev_replace_item {
+	/*
+	 * grow this item struct at the end for future enhancements and keep
+	 * the existing values unchanged
+	 */
+	__le64 src_devid;
+	__le64 cursor_left;
+	__le64 cursor_right;
+	__le64 cont_reading_from_srcdev_mode;
+
+	__le64 replace_state;
+	__le64 time_started;
+	__le64 time_stopped;
+	__le64 num_write_errors;
+	__le64 num_uncorrectable_read_errors;
 } __attribute__ ((__packed__));
 
 /* different types of block groups (and chunks) */
···
 	struct btrfs_workers generic_worker;
 	struct btrfs_workers workers;
 	struct btrfs_workers delalloc_workers;
+	struct btrfs_workers flush_workers;
 	struct btrfs_workers endio_workers;
 	struct btrfs_workers endio_meta_workers;
 	struct btrfs_workers endio_meta_write_workers;
···
 	struct rw_semaphore scrub_super_lock;
 	int scrub_workers_refcnt;
 	struct btrfs_workers scrub_workers;
+	struct btrfs_workers scrub_wr_completion_workers;
+	struct btrfs_workers scrub_nocow_workers;
 
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 	u32 check_integrity_print_mask;
···
 	int backup_root_index;
 
 	int num_tolerated_disk_barrier_failures;
+
+	/* device replace state */
+	struct btrfs_dev_replace dev_replace;
+
+	atomic_t mutually_exclusive_operation_running;
 };
 
 /*
···
 
 	int force_cow;
 
-	spinlock_t root_times_lock;
+	spinlock_t root_item_lock;
 };
 
 struct btrfs_ioctl_defrag_range_args {
···
 #define BTRFS_DEV_STATS_KEY	249
 
 /*
+ * Persistantly stores the device replace state in the device tree.
+ * The key is built like this: (0, BTRFS_DEV_REPLACE_KEY, 0).
+ */
+#define BTRFS_DEV_REPLACE_KEY	250
+
+/*
  * string items are for debugging.  They just store a short string of
  * data in the FS
  */
···
 
 static inline void btrfs_init_map_token (struct btrfs_map_token *token)
 {
-	memset(token, 0, sizeof(*token));
+	token->kaddr = NULL;
 }
 
 /* some macros to generate set/get funcs for the struct fields.  This
···
 BTRFS_SETGET_FUNCS(qgroup_limit_rsv_excl, struct btrfs_qgroup_limit_item,
 		   rsv_excl, 64);
 
+/* btrfs_dev_replace_item */
+BTRFS_SETGET_FUNCS(dev_replace_src_devid,
+		   struct btrfs_dev_replace_item, src_devid, 64);
+BTRFS_SETGET_FUNCS(dev_replace_cont_reading_from_srcdev_mode,
+		   struct btrfs_dev_replace_item, cont_reading_from_srcdev_mode,
+		   64);
+BTRFS_SETGET_FUNCS(dev_replace_replace_state, struct btrfs_dev_replace_item,
+		   replace_state, 64);
+BTRFS_SETGET_FUNCS(dev_replace_time_started, struct btrfs_dev_replace_item,
+		   time_started, 64);
+BTRFS_SETGET_FUNCS(dev_replace_time_stopped, struct btrfs_dev_replace_item,
+		   time_stopped, 64);
+BTRFS_SETGET_FUNCS(dev_replace_num_write_errors, struct btrfs_dev_replace_item,
+		   num_write_errors, 64);
+BTRFS_SETGET_FUNCS(dev_replace_num_uncorrectable_read_errors,
+		   struct btrfs_dev_replace_item, num_uncorrectable_read_errors,
+		   64);
+BTRFS_SETGET_FUNCS(dev_replace_cursor_left, struct btrfs_dev_replace_item,
+		   cursor_left, 64);
+BTRFS_SETGET_FUNCS(dev_replace_cursor_right, struct btrfs_dev_replace_item,
+		   cursor_right, 64);
+
+BTRFS_SETGET_STACK_FUNCS(stack_dev_replace_src_devid,
+			 struct btrfs_dev_replace_item, src_devid, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_dev_replace_cont_reading_from_srcdev_mode,
+			 struct btrfs_dev_replace_item,
+			 cont_reading_from_srcdev_mode, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_dev_replace_replace_state,
+			 struct btrfs_dev_replace_item, replace_state, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_dev_replace_time_started,
+			 struct btrfs_dev_replace_item, time_started, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_dev_replace_time_stopped,
+			 struct btrfs_dev_replace_item, time_stopped, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_dev_replace_num_write_errors,
+			 struct btrfs_dev_replace_item, num_write_errors, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_dev_replace_num_uncorrectable_read_errors,
+			 struct btrfs_dev_replace_item,
+			 num_uncorrectable_read_errors, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_dev_replace_cursor_left,
+			 struct btrfs_dev_replace_item, cursor_left, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_dev_replace_cursor_right,
+			 struct btrfs_dev_replace_item, cursor_right, 64);
+
 static inline struct btrfs_fs_info *btrfs_sb(struct super_block *sb)
 {
 	return sb->s_fs_info;
···
 u64 btrfs_reduce_alloc_profile(struct btrfs_root *root, u64 flags);
 u64 btrfs_get_alloc_profile(struct btrfs_root *root, int data);
 void btrfs_clear_space_info_full(struct btrfs_fs_info *info);
+
+enum btrfs_reserve_flush_enum {
+	/* If we are in the transaction, we can't flush anything.*/
+	BTRFS_RESERVE_NO_FLUSH,
+	/*
+	 * Flushing delalloc may cause deadlock somewhere, in this
+	 * case, use FLUSH LIMIT
+	 */
+	BTRFS_RESERVE_FLUSH_LIMIT,
+	BTRFS_RESERVE_FLUSH_ALL,
+};
+
 int btrfs_check_data_free_space(struct inode *inode, u64 bytes);
 void btrfs_free_reserved_data_space(struct inode *inode, u64 bytes);
 void btrfs_trans_release_metadata(struct btrfs_trans_handle *trans,
···
 void btrfs_free_block_rsv(struct btrfs_root *root,
 			  struct btrfs_block_rsv *rsv);
 int btrfs_block_rsv_add(struct btrfs_root *root,
-			struct btrfs_block_rsv *block_rsv,
-			u64 num_bytes);
-int btrfs_block_rsv_add_noflush(struct btrfs_root *root,
-				struct btrfs_block_rsv *block_rsv,
-				u64 num_bytes);
+			struct btrfs_block_rsv *block_rsv, u64 num_bytes,
+			enum btrfs_reserve_flush_enum flush);
 int btrfs_block_rsv_check(struct btrfs_root *root,
 			  struct btrfs_block_rsv *block_rsv, int min_factor);
 int btrfs_block_rsv_refill(struct btrfs_root *root,
-			  struct btrfs_block_rsv *block_rsv,
-			  u64 min_reserved);
-int btrfs_block_rsv_refill_noflush(struct btrfs_root *root,
-				   struct btrfs_block_rsv *block_rsv,
-				   u64 min_reserved);
+			   struct btrfs_block_rsv *block_rsv, u64 min_reserved,
+			   enum btrfs_reserve_flush_enum flush);
 int btrfs_block_rsv_migrate(struct btrfs_block_rsv *src_rsv,
 			    struct btrfs_block_rsv *dst_rsv,
 			    u64 num_bytes);
···
 int btrfs_init_space_info(struct btrfs_fs_info *fs_info);
 int btrfs_delayed_refs_qgroup_accounting(struct btrfs_trans_handle *trans,
 					 struct btrfs_fs_info *fs_info);
+int __get_raid_index(u64 flags);
 /* ctree.c */
 int btrfs_bin_search(struct extent_buffer *eb, struct btrfs_key *key,
 		     int level, int *slot);
···
 }
 
 int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path);
+int btrfs_next_leaf_write(struct btrfs_trans_handle *trans,
+			  struct btrfs_root *root, struct btrfs_path *path,
+			  int del);
 int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path,
 			u64 time_seq);
 static inline int btrfs_next_old_item(struct btrfs_root *root,
···
 			     struct btrfs_root *root);
 
 /* dir-item.c */
+int btrfs_check_dir_item_collision(struct btrfs_root *root, u64 dir,
+			  const char *name, int name_len);
 int btrfs_insert_dir_item(struct btrfs_trans_handle *trans,
 			  struct btrfs_root *root, const char *name,
 			  int name_len, struct inode *dir,
···
 			     struct btrfs_root *root,
 			     struct btrfs_path *path, u64 objectid,
 			     u64 bytenr, int mod);
+u64 btrfs_file_extent_length(struct btrfs_path *path);
 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 			   struct btrfs_root *root,
 			   struct btrfs_ordered_sum *sums);
···
 int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
 			     struct list_head *list, int search_commit);
 /* inode.c */
+struct btrfs_delalloc_work {
+	struct inode *inode;
+	int wait;
+	int delay_iput;
+	struct completion completion;
+	struct list_head list;
+	struct btrfs_work work;
+};
+
+struct btrfs_delalloc_work *btrfs_alloc_delalloc_work(struct inode *inode,
+						    int wait, int delay_iput);
+void btrfs_wait_and_free_delalloc_work(struct btrfs_delalloc_work *work);
+
 struct extent_map *btrfs_get_extent_fiemap(struct inode *inode, struct page *page,
 					   size_t pg_offset, u64 start, u64 len,
 					   int create);
···
 				struct btrfs_ioctl_space_info *space);
 
 /* file.c */
+int btrfs_auto_defrag_init(void);
+void btrfs_auto_defrag_exit(void);
 int btrfs_add_inode_defrag(struct btrfs_trans_handle *trans,
 			   struct inode *inode);
 int btrfs_run_defrag_inodes(struct btrfs_fs_info *fs_info);
+void btrfs_cleanup_defrag_inodes(struct btrfs_fs_info *fs_info);
 int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync);
 void btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end,
 			     int skip_pinned);
···
 			      struct btrfs_pending_snapshot *pending);
 
 /* scrub.c */
-int btrfs_scrub_dev(struct btrfs_root *root, u64 devid, u64 start, u64 end,
-		    struct btrfs_scrub_progress *progress, int readonly);
+int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
+		    u64 end, struct btrfs_scrub_progress *progress,
+		    int readonly, int is_dev_replace);
 void btrfs_scrub_pause(struct btrfs_root *root);
 void btrfs_scrub_pause_super(struct btrfs_root *root);
 void btrfs_scrub_continue(struct btrfs_root *root);
 void btrfs_scrub_continue_super(struct btrfs_root *root);
-int __btrfs_scrub_cancel(struct btrfs_fs_info *info);
-int btrfs_scrub_cancel(struct btrfs_root *root);
-int btrfs_scrub_cancel_dev(struct btrfs_root *root, struct btrfs_device *dev);
+int btrfs_scrub_cancel(struct btrfs_fs_info *info);
+int btrfs_scrub_cancel_dev(struct btrfs_fs_info *info,
+			   struct btrfs_device *dev);
 int btrfs_scrub_cancel_devid(struct btrfs_root *root, u64 devid);
 int btrfs_scrub_progress(struct btrfs_root *root, u64 devid,
 			 struct btrfs_scrub_progress *progress);

fs/btrfs/delayed-inode.c

···
 	 */
 	if (!src_rsv || (!trans->bytes_reserved &&
 			 src_rsv->type != BTRFS_BLOCK_RSV_DELALLOC)) {
-		ret = btrfs_block_rsv_add_noflush(root, dst_rsv, num_bytes);
+		ret = btrfs_block_rsv_add(root, dst_rsv, num_bytes,
+					  BTRFS_RESERVE_NO_FLUSH);
 		/*
 		 * Since we're under a transaction reserve_metadata_bytes could
 		 * try to commit the transaction which will make it return
···
 		 * reserve something strictly for us.  If not be a pain and try
 		 * to steal from the delalloc block rsv.
 		 */
-		ret = btrfs_block_rsv_add_noflush(root, dst_rsv, num_bytes);
+		ret = btrfs_block_rsv_add(root, dst_rsv, num_bytes,
+					  BTRFS_RESERVE_NO_FLUSH);
 		if (!ret)
 			goto out;
 
···
 	struct btrfs_delayed_node *delayed_node = NULL;
 	struct btrfs_root *root;
 	struct btrfs_block_rsv *block_rsv;
-	unsigned long nr = 0;
 	int need_requeue = 0;
 	int ret;
 
···
 					   delayed_node);
 	mutex_unlock(&delayed_node->mutex);
 
-	nr = trans->blocks_used;
-
 	trans->block_rsv = block_rsv;
 	btrfs_end_transaction_dmeta(trans, root);
-	__btrfs_btree_balance_dirty(root, nr);
+	btrfs_btree_balance_dirty_nodelay(root);
 free_path:
 	btrfs_free_path(path);
 out:

fs/btrfs/dev-replace.c

···
+/*
+ * Copyright (C) STRATO AG 2012.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+#include <linux/sched.h>
+#include <linux/bio.h>
+#include <linux/slab.h>
+#include <linux/buffer_head.h>
+#include <linux/blkdev.h>
+#include <linux/random.h>
+#include <linux/iocontext.h>
+#include <linux/capability.h>
+#include <linux/kthread.h>
+#include <linux/math64.h>
+#include <asm/div64.h>
+#include "compat.h"
+#include "ctree.h"
+#include "extent_map.h"
+#include "disk-io.h"
+#include "transaction.h"
+#include "print-tree.h"
+#include "volumes.h"
+#include "async-thread.h"
+#include "check-integrity.h"
+#include "rcu-string.h"
+#include "dev-replace.h"
+
+static u64 btrfs_get_seconds_since_1970(void);
+static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
+				       int scrub_ret);
+static void btrfs_dev_replace_update_device_in_mapping_tree(
+						struct btrfs_fs_info *fs_info,
+						struct btrfs_device *srcdev,
+						struct btrfs_device *tgtdev);
+static int btrfs_dev_replace_find_srcdev(struct btrfs_root *root, u64 srcdevid,
+					 char *srcdev_name,
+					 struct btrfs_device **device);
+static u64 __btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info);
+static int btrfs_dev_replace_kthread(void *data);
+static int btrfs_dev_replace_continue_on_mount(struct btrfs_fs_info *fs_info);
+
+
+int btrfs_init_dev_replace(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_key key;
+	struct btrfs_root *dev_root = fs_info->dev_root;
+	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
+	struct extent_buffer *eb;
+	int slot;
+	int ret = 0;
+	struct btrfs_path *path = NULL;
+	int item_size;
+	struct btrfs_dev_replace_item *ptr;
+	u64 src_devid;
+
+	path = btrfs_alloc_path();
+	if (!path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	key.objectid = 0;
+	key.type = BTRFS_DEV_REPLACE_KEY;
+	key.offset = 0;
+	ret = btrfs_search_slot(NULL, dev_root, &key, path, 0, 0);
+	if (ret) {
+no_valid_dev_replace_entry_found:
+		ret = 0;
+		dev_replace->replace_state =
+			BTRFS_DEV_REPLACE_ITEM_STATE_NEVER_STARTED;
+		dev_replace->cont_reading_from_srcdev_mode =
+		    BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_ALWAYS;
+		dev_replace->replace_state = 0;
+		dev_replace->time_started = 0;
+		dev_replace->time_stopped = 0;
+		atomic64_set(&dev_replace->num_write_errors, 0);
+		atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
+		dev_replace->cursor_left = 0;
+		dev_replace->committed_cursor_left = 0;
+		dev_replace->cursor_left_last_write_of_item = 0;
+		dev_replace->cursor_right = 0;
+		dev_replace->srcdev = NULL;
+		dev_replace->tgtdev = NULL;
+		dev_replace->is_valid = 0;
+		dev_replace->item_needs_writeback = 0;
+		goto out;
+	}
+	slot = path->slots[0];
+	eb = path->nodes[0];
+	item_size = btrfs_item_size_nr(eb, slot);
+	ptr = btrfs_item_ptr(eb, slot, struct btrfs_dev_replace_item);
+
+	if (item_size != sizeof(struct btrfs_dev_replace_item)) {
+		pr_warn("btrfs: dev_replace entry found has unexpected size, ignore entry\n");
+		goto no_valid_dev_replace_entry_found;
+	}
+
+	src_devid = btrfs_dev_replace_src_devid(eb, ptr);
+	dev_replace->cont_reading_from_srcdev_mode =
+		btrfs_dev_replace_cont_reading_from_srcdev_mode(eb, ptr);
+	dev_replace->replace_state = btrfs_dev_replace_replace_state(eb, ptr);
+	dev_replace->time_started = btrfs_dev_replace_time_started(eb, ptr);
+	dev_replace->time_stopped =
+		btrfs_dev_replace_time_stopped(eb, ptr);
+	atomic64_set(&dev_replace->num_write_errors,
+		     btrfs_dev_replace_num_write_errors(eb, ptr));
+	atomic64_set(&dev_replace->num_uncorrectable_read_errors,
+		     btrfs_dev_replace_num_uncorrectable_read_errors(eb, ptr));
+	dev_replace->cursor_left = btrfs_dev_replace_cursor_left(eb, ptr);
+	dev_replace->committed_cursor_left = dev_replace->cursor_left;
+	dev_replace->cursor_left_last_write_of_item = dev_replace->cursor_left;
+	dev_replace->cursor_right = btrfs_dev_replace_cursor_right(eb, ptr);
+	dev_replace->is_valid = 1;
+
+	dev_replace->item_needs_writeback = 0;
+	switch (dev_replace->replace_state) {
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
+		dev_replace->srcdev = NULL;
+		dev_replace->tgtdev = NULL;
+		break;
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
+		dev_replace->srcdev = btrfs_find_device(fs_info, src_devid,
+							NULL, NULL);
+		dev_replace->tgtdev = btrfs_find_device(fs_info,
+							BTRFS_DEV_REPLACE_DEVID,
+							NULL, NULL);
+		/*
+		 * allow 'btrfs dev replace_cancel' if src/tgt device is
+		 * missing
+		 */
+		if (!dev_replace->srcdev &&
+		    !btrfs_test_opt(dev_root, DEGRADED)) {
+			ret = -EIO;
+			pr_warn("btrfs: cannot mount because device replace operation is ongoing and\n" "srcdev (devid %llu) is missing, need to run 'btrfs dev scan'?\n",
+				(unsigned long long)src_devid);
+		}
+		if (!dev_replace->tgtdev &&
+		    !btrfs_test_opt(dev_root, DEGRADED)) {
+			ret = -EIO;
+			pr_warn("btrfs: cannot mount because device replace operation is ongoing and\n" "tgtdev (devid %llu) is missing, need to run btrfs dev scan?\n",
+				(unsigned long long)BTRFS_DEV_REPLACE_DEVID);
+		}
+		if (dev_replace->tgtdev) {
+			if (dev_replace->srcdev) {
+				dev_replace->tgtdev->total_bytes =
+					dev_replace->srcdev->total_bytes;
+				dev_replace->tgtdev->disk_total_bytes =
+					dev_replace->srcdev->disk_total_bytes;
+				dev_replace->tgtdev->bytes_used =
+					dev_replace->srcdev->bytes_used;
+			}
+			dev_replace->tgtdev->is_tgtdev_for_dev_replace = 1;
+			btrfs_init_dev_replace_tgtdev_for_resume(fs_info,
+				dev_replace->tgtdev);
+		}
+		break;
+	}
+
+out:
+	if (path)
+		btrfs_free_path(path);
+	return ret;
+}
+
+/*
+ * called from commit_transaction. Writes changed device replace state to
+ * disk.
+ */
+int btrfs_run_dev_replace(struct btrfs_trans_handle *trans,
+			  struct btrfs_fs_info *fs_info)
+{
+	int ret;
+	struct btrfs_root *dev_root = fs_info->dev_root;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct extent_buffer *eb;
+	struct btrfs_dev_replace_item *ptr;
+	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
+
+	btrfs_dev_replace_lock(dev_replace);
+	if (!dev_replace->is_valid ||
+	    !dev_replace->item_needs_writeback) {
+		btrfs_dev_replace_unlock(dev_replace);
+		return 0;
+	}
+	btrfs_dev_replace_unlock(dev_replace);
+
+	key.objectid = 0;
+	key.type = BTRFS_DEV_REPLACE_KEY;
+	key.offset = 0;
+
+	path = btrfs_alloc_path();
+	if (!path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	ret = btrfs_search_slot(trans, dev_root, &key, path, -1, 1);
+	if (ret < 0) {
+		pr_warn("btrfs: error %d while searching for dev_replace item!\n",
+			ret);
+		goto out;
+	}
+
+	if (ret == 0 &&
+	    btrfs_item_size_nr(path->nodes[0], path->slots[0]) < sizeof(*ptr)) {
+		/*
+		 * need to delete old one and insert a new one.
+		 * Since no attempt is made to recover any old state, if the
+		 * dev_replace state is 'running', the data on the target
+		 * drive is lost.
+		 * It would be possible to recover the state: just make sure
+		 * that the beginning of the item is never changed and always
+		 * contains all the essential information. Then read this
+		 * minimal set of information and use it as a base for the
+		 * new state.
+		 */
+		ret = btrfs_del_item(trans, dev_root, path);
+		if (ret != 0) {
+			pr_warn("btrfs: delete too small dev_replace item failed %d!\n",
+				ret);
+			goto out;
+		}
+		ret = 1;
+	}
+
+	if (ret == 1) {
+		/* need to insert a new item */
+		btrfs_release_path(path);
+		ret = btrfs_insert_empty_item(trans, dev_root, path,
+					      &key, sizeof(*ptr));
+		if (ret < 0) {
+			pr_warn("btrfs: insert dev_replace item failed %d!\n",
+				ret);
+			goto out;
+		}
+	}
+
+	eb = path->nodes[0];
+	ptr = btrfs_item_ptr(eb, path->slots[0],
+			     struct btrfs_dev_replace_item);
+
+	btrfs_dev_replace_lock(dev_replace);
+	if (dev_replace->srcdev)
+		btrfs_set_dev_replace_src_devid(eb, ptr,
+			dev_replace->srcdev->devid);
+	else
+		btrfs_set_dev_replace_src_devid(eb, ptr, (u64)-1);
+	btrfs_set_dev_replace_cont_reading_from_srcdev_mode(eb, ptr,
+		dev_replace->cont_reading_from_srcdev_mode);
+	btrfs_set_dev_replace_replace_state(eb, ptr,
+		dev_replace->replace_state);
+	btrfs_set_dev_replace_time_started(eb, ptr, dev_replace->time_started);
+	btrfs_set_dev_replace_time_stopped(eb, ptr, dev_replace->time_stopped);
+	btrfs_set_dev_replace_num_write_errors(eb, ptr,
+		atomic64_read(&dev_replace->num_write_errors));
+	btrfs_set_dev_replace_num_uncorrectable_read_errors(eb, ptr,
+		atomic64_read(&dev_replace->num_uncorrectable_read_errors));
+	dev_replace->cursor_left_last_write_of_item =
+		dev_replace->cursor_left;
+	btrfs_set_dev_replace_cursor_left(eb, ptr,
+		dev_replace->cursor_left_last_write_of_item);
+	btrfs_set_dev_replace_cursor_right(eb, ptr,
+		dev_replace->cursor_right);
+	dev_replace->item_needs_writeback = 0;
+	btrfs_dev_replace_unlock(dev_replace);
+
+	btrfs_mark_buffer_dirty(eb);
+
+out:
+	btrfs_free_path(path);
+
+	return ret;
+}
+
+void btrfs_after_dev_replace_commit(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
+
+	dev_replace->committed_cursor_left =
+		dev_replace->cursor_left_last_write_of_item;
+}
+
+static u64 btrfs_get_seconds_since_1970(void)
+{
+	struct timespec t = CURRENT_TIME_SEC;
+
+	return t.tv_sec;
+}
+
+int btrfs_dev_replace_start(struct btrfs_root *root,
+			    struct btrfs_ioctl_dev_replace_args *args)
+{
+	struct btrfs_trans_handle *trans;
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
+	int ret;
+	struct btrfs_device *tgt_device = NULL;
+	struct btrfs_device *src_device = NULL;
+
+	switch (args->start.cont_reading_from_srcdev_mode) {
+	case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_ALWAYS:
+	case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_AVOID:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||
+	    args->start.tgtdev_name[0] == '\0')
+		return -EINVAL;
+
+	mutex_lock(&fs_info->volume_mutex);
+	ret = btrfs_init_dev_replace_tgtdev(root, args->start.tgtdev_name,
+					    &tgt_device);
+	if (ret) {
+		pr_err("btrfs: target device %s is invalid!\n",
+		       args->start.tgtdev_name);
+		mutex_unlock(&fs_info->volume_mutex);
+		return -EINVAL;
+	}
+
+	ret = btrfs_dev_replace_find_srcdev(root, args->start.srcdevid,
+					    args->start.srcdev_name,
+					    &src_device);
+	mutex_unlock(&fs_info->volume_mutex);
+	if (ret) {
+		ret = -EINVAL;
+		goto leave_no_lock;
+	}
+
+	if (tgt_device->total_bytes < src_device->total_bytes) {
+		pr_err("btrfs: target device is smaller than source device!\n");
+		ret = -EINVAL;
+		goto leave_no_lock;
+	}
+
+	btrfs_dev_replace_lock(dev_replace);
+	switch (dev_replace->replace_state) {
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
+		break;
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
+		args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_ALREADY_STARTED;
+		goto leave;
+	}
+
+	dev_replace->cont_reading_from_srcdev_mode =
+		args->start.cont_reading_from_srcdev_mode;
+	WARN_ON(!src_device);
+	dev_replace->srcdev = src_device;
+	WARN_ON(!tgt_device);
+	dev_replace->tgtdev = tgt_device;
+
+	printk_in_rcu(KERN_INFO
+		      "btrfs: dev_replace from %s (devid %llu) to %s) started\n",
+		      src_device->missing ? "<missing disk>" :
+		        rcu_str_deref(src_device->name),
+		      src_device->devid,
+		      rcu_str_deref(tgt_device->name));
+
+	tgt_device->total_bytes = src_device->total_bytes;
+	tgt_device->disk_total_bytes = src_device->disk_total_bytes;
+	tgt_device->bytes_used = src_device->bytes_used;
+
+	/*
+	 * from now on, the writes to the srcdev are all duplicated to
+	 * go to the tgtdev as well (refer to btrfs_map_block()).
+	 */
+	dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
+	dev_replace->time_started = btrfs_get_seconds_since_1970();
+	dev_replace->cursor_left = 0;
+	dev_replace->committed_cursor_left = 0;
+	dev_replace->cursor_left_last_write_of_item = 0;
+	dev_replace->cursor_right = 0;
+	dev_replace->is_valid = 1;
+	dev_replace->item_needs_writeback = 1;
+	args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
+	btrfs_dev_replace_unlock(dev_replace);
+
+	btrfs_wait_ordered_extents(root, 0);
+
+	/* force writing the updated state information to disk */
+	trans = btrfs_start_transaction(root, 0);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		btrfs_dev_replace_lock(dev_replace);
+		goto leave;
+	}
+
+	ret = btrfs_commit_transaction(trans, root);
+	WARN_ON(ret);
+
+	/* the disk copy procedure reuses the scrub code */
+	ret = btrfs_scrub_dev(fs_info, src_device->devid, 0,
+			      src_device->total_bytes,
+			      &dev_replace->scrub_progress, 0, 1);
+
+	ret = btrfs_dev_replace_finishing(root->fs_info, ret);
+	WARN_ON(ret);
+
+	return 0;
+
+leave:
+	dev_replace->srcdev = NULL;
+	dev_replace->tgtdev = NULL;
+	btrfs_dev_replace_unlock(dev_replace);
+leave_no_lock:
+	if (tgt_device)
+		btrfs_destroy_dev_replace_tgtdev(fs_info, tgt_device);
+	return ret;
+}
+
+static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
+				       int scrub_ret)
+{
+	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
+	struct btrfs_device *tgt_device;
+	struct btrfs_device *src_device;
+	struct btrfs_root *root = fs_info->tree_root;
+	u8 uuid_tmp[BTRFS_UUID_SIZE];
+	struct btrfs_trans_handle *trans;
+	int ret = 0;
+
+	/* don't allow cancel or unmount to disturb the finishing procedure */
+	mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
+
+	btrfs_dev_replace_lock(dev_replace);
+	/* was the operation canceled, or is it finished? */
+	if (dev_replace->replace_state !=
+	    BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED) {
+		btrfs_dev_replace_unlock(dev_replace);
+		mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
+		return 0;
+	}
+
+	tgt_device = dev_replace->tgtdev;
+	src_device = dev_replace->srcdev;
+	btrfs_dev_replace_unlock(dev_replace);
+
+	/* replace old device with new one in mapping tree */
+	if (!scrub_ret)
+		btrfs_dev_replace_update_device_in_mapping_tree(fs_info,
+								src_device,
+								tgt_device);
+
+	/*
+	 * flush all outstanding I/O and inode extent mappings before the
+	 * copy operation is declared as being finished
+	 */
+	btrfs_start_delalloc_inodes(root, 0);
+	btrfs_wait_ordered_extents(root, 0);
+
+	trans = btrfs_start_transaction(root, 0);
+	if (IS_ERR(trans)) {
+		mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
+		return PTR_ERR(trans);
+	}
+	ret = btrfs_commit_transaction(trans, root);
+	WARN_ON(ret);
+
+	/* keep away write_all_supers() during the finishing procedure */
+	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
+	btrfs_dev_replace_lock(dev_replace);
+	dev_replace->replace_state =
+		scrub_ret ? BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED
+			  : BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED;
+	dev_replace->tgtdev = NULL;
+	dev_replace->srcdev = NULL;
+	dev_replace->time_stopped = btrfs_get_seconds_since_1970();
+	dev_replace->item_needs_writeback = 1;
+
+	if (scrub_ret) {
+		printk_in_rcu(KERN_ERR
+			      "btrfs: btrfs_scrub_dev(%s, %llu, %s) failed %d\n",
+			      src_device->missing ? "<missing disk>" :
+			        rcu_str_deref(src_device->name),
+			      src_device->devid,
+			      rcu_str_deref(tgt_device->name), scrub_ret);
+		btrfs_dev_replace_unlock(dev_replace);
+		mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
+		if (tgt_device)
+			btrfs_destroy_dev_replace_tgtdev(fs_info, tgt_device);
+		mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
+
+		return 0;
+	}
+
+	printk_in_rcu(KERN_INFO
+		      "btrfs: dev_replace from %s (devid %llu) to %s) finished\n",
+		      src_device->missing ? "<missing disk>" :
+		        rcu_str_deref(src_device->name),
+		      src_device->devid,
+		      rcu_str_deref(tgt_device->name));
+	tgt_device->is_tgtdev_for_dev_replace = 0;
+	tgt_device->devid = src_device->devid;
+	src_device->devid = BTRFS_DEV_REPLACE_DEVID;
+	tgt_device->bytes_used = src_device->bytes_used;
+	memcpy(uuid_tmp, tgt_device->uuid, sizeof(uuid_tmp));
+	memcpy(tgt_device->uuid, src_device->uuid, sizeof(tgt_device->uuid));
+	memcpy(src_device->uuid, uuid_tmp, sizeof(src_device->uuid));
+	tgt_device->total_bytes = src_device->total_bytes;
+	tgt_device->disk_total_bytes = src_device->disk_total_bytes;
+	tgt_device->bytes_used = src_device->bytes_used;
+	if (fs_info->sb->s_bdev == src_device->bdev)
+		fs_info->sb->s_bdev = tgt_device->bdev;
+	if (fs_info->fs_devices->latest_bdev == src_device->bdev)
+		fs_info->fs_devices->latest_bdev = tgt_device->bdev;
+	list_add(&tgt_device->dev_alloc_list, &fs_info->fs_devices->alloc_list);
+
+	btrfs_rm_dev_replace_srcdev(fs_info, src_device);
+	if (src_device->bdev) {
+		/* zero out the old super */
+		btrfs_scratch_superblock(src_device);
+	}
+	/*
+	 * this is again a consistent state where no dev_replace procedure
+	 * is running, the target device is part of the filesystem, the
+	 * source device is not part of the filesystem anymore and its 1st
+	 * superblock is scratched out so that it is no longer marked to
+	 * belong to this filesystem.
+	 */
+	btrfs_dev_replace_unlock(dev_replace);
+	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
+
+	/* write back the superblocks */
+	trans = btrfs_start_transaction(root, 0);
+	if (!IS_ERR(trans))
+		btrfs_commit_transaction(trans, root);
+
+	mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
+
+	return 0;
+}
+
+static void btrfs_dev_replace_update_device_in_mapping_tree(
+						struct btrfs_fs_info *fs_info,
+						struct btrfs_device *srcdev,
+						struct btrfs_device *tgtdev)
+{
+	struct extent_map_tree *em_tree = &fs_info->mapping_tree.map_tree;
+	struct extent_map *em;
+	struct map_lookup *map;
+	u64 start = 0;
+	int i;
+
+	write_lock(&em_tree->lock);
+	do {
+		em = lookup_extent_mapping(em_tree, start, (u64)-1);
+		if (!em)
+			break;
+		map = (struct map_lookup *)em->bdev;
+		for (i = 0; i < map->num_stripes; i++)
+			if (srcdev == map->stripes[i].dev)
+				map->stripes[i].dev = tgtdev;
+		start = em->start + em->len;
+		free_extent_map(em);
+	} while (start);
+	write_unlock(&em_tree->lock);
+}
+
+static int btrfs_dev_replace_find_srcdev(struct btrfs_root *root, u64 srcdevid,
+					 char *srcdev_name,
+					 struct btrfs_device **device)
+{
+	int ret;
+
+	if (srcdevid) {
+		ret = 0;
+		*device = btrfs_find_device(root->fs_info, srcdevid, NULL,
+					    NULL);
+		if (!*device)
+			ret = -ENOENT;
+	} else {
+		ret = btrfs_find_device_missing_or_by_path(root, srcdev_name,
+							   device);
+	}
+	return ret;
+}
+
+void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info,
+			      struct btrfs_ioctl_dev_replace_args *args)
+{
+	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
+
+	btrfs_dev_replace_lock(dev_replace);
+	/* even if !dev_replace_is_valid, the values are good enough for
+	 * the replace_status ioctl */
+	args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
+	args->status.replace_state = dev_replace->replace_state;
+	args->status.time_started = dev_replace->time_started;
+	args->status.time_stopped = dev_replace->time_stopped;
+	args->status.num_write_errors =
+		atomic64_read(&dev_replace->num_write_errors);
+	args->status.num_uncorrectable_read_errors =
+		atomic64_read(&dev_replace->num_uncorrectable_read_errors);
+	switch (dev_replace->replace_state) {
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
+		args->status.progress_1000 = 0;
+		break;
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
+		args->status.progress_1000 = 1000;
+		break;
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
+		args->status.progress_1000 = div64_u64(dev_replace->cursor_left,
+			div64_u64(dev_replace->srcdev->total_bytes, 1000));
+		break;
+	}
+	btrfs_dev_replace_unlock(dev_replace);
+}
+
+int btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info,
+			     struct btrfs_ioctl_dev_replace_args *args)
+{
+	args->result = __btrfs_dev_replace_cancel(fs_info);
+	return 0;
+}
+
+static u64 __btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
+	struct btrfs_device *tgt_device = NULL;
+	struct btrfs_trans_handle *trans;
+	struct btrfs_root *root = fs_info->tree_root;
+	u64 result;
+	int ret;
+
+	mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
+	btrfs_dev_replace_lock(dev_replace);
+	switch (dev_replace->replace_state) {
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
+		result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
+		btrfs_dev_replace_unlock(dev_replace);
+		goto leave;
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
+		result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
+		tgt_device = dev_replace->tgtdev;
+		dev_replace->tgtdev = NULL;
+		dev_replace->srcdev = NULL;
+		break;
+	}
+	dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED;
+	dev_replace->time_stopped = btrfs_get_seconds_since_1970();
+	dev_replace->item_needs_writeback = 1;
+	btrfs_dev_replace_unlock(dev_replace);
+	btrfs_scrub_cancel(fs_info);
+
+	trans = btrfs_start_transaction(root, 0);
+	if (IS_ERR(trans)) {
+		mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
+		return PTR_ERR(trans);
+	}
+	ret = btrfs_commit_transaction(trans, root);
+	WARN_ON(ret);
+	if (tgt_device)
+		btrfs_destroy_dev_replace_tgtdev(fs_info, tgt_device);
+
+leave:
+	mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
+	return result;
+}
+
+void btrfs_dev_replace_suspend_for_unmount(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
+
+	mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
+	btrfs_dev_replace_lock(dev_replace);
+	switch (dev_replace->replace_state) {
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
+		break;
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
+		dev_replace->replace_state =
+			BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
+		dev_replace->time_stopped = btrfs_get_seconds_since_1970();
+		dev_replace->item_needs_writeback = 1;
+		pr_info("btrfs: suspending dev_replace for unmount\n");
+		break;
+	}
+
+	btrfs_dev_replace_unlock(dev_replace);
+	mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
+}
+
+/* resume dev_replace procedure that was interrupted by unmount */
+int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info)
+{
+	struct task_struct *task;
+	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
+
+	btrfs_dev_replace_lock(dev_replace);
+	switch (dev_replace->replace_state) {
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
+		btrfs_dev_replace_unlock(dev_replace);
+		return 0;
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
+		break;
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
+		dev_replace->replace_state =
+			BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
+		break;
+	}
+	if (!dev_replace->tgtdev || !dev_replace->tgtdev->bdev) {
+		pr_info("btrfs: cannot continue dev_replace, tgtdev is missing\n"
+			"btrfs: you may cancel the operation after 'mount -o degraded'\n");
+		btrfs_dev_replace_unlock(dev_replace);
+		return 0;
+	}
+	btrfs_dev_replace_unlock(dev_replace);
+
+	WARN_ON(atomic_xchg(
+		&fs_info->mutually_exclusive_operation_running, 1));
+	task = kthread_run(btrfs_dev_replace_kthread, fs_info, "btrfs-devrepl");
+	return PTR_RET(task);
+}
+
+static int btrfs_dev_replace_kthread(void *data)
+{
+	struct btrfs_fs_info *fs_info = data;
+	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
+	struct btrfs_ioctl_dev_replace_args *status_args;
+	u64 progress;
+
+	status_args = kzalloc(sizeof(*status_args), GFP_NOFS);
+	if (status_args) {
+		btrfs_dev_replace_status(fs_info, status_args);
+		progress = status_args->status.progress_1000;
+		kfree(status_args);
+		do_div(progress, 10);
+		printk_in_rcu(KERN_INFO
+			      "btrfs: continuing dev_replace from %s (devid %llu) to %s @%u%%\n",
+			      dev_replace->srcdev->missing ? "<missing disk>" :
+				rcu_str_deref(dev_replace->srcdev->name),
+			      dev_replace->srcdev->devid,
+			      dev_replace->tgtdev ?
+				rcu_str_deref(dev_replace->tgtdev->name) :
+				"<missing target disk>",
+			      (unsigned int)progress);
+	}
+	btrfs_dev_replace_continue_on_mount(fs_info);
+	atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
+
+	return 0;
+}
+
+static int btrfs_dev_replace_continue_on_mount(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
+	int ret;
+
+	ret = btrfs_scrub_dev(fs_info, dev_replace->srcdev->devid,
+			      dev_replace->committed_cursor_left,
+			      dev_replace->srcdev->total_bytes,
+			      &dev_replace->scrub_progress, 0, 1);
+	ret = btrfs_dev_replace_finishing(fs_info, ret);
+	WARN_ON(ret);
+	return 0;
+}
+
+int btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace)
+{
+	if (!dev_replace->is_valid)
+		return 0;
+
+	switch (dev_replace->replace_state) {
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
+		return 0;
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
+	case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
+		/*
+		 * return true even if tgtdev is missing (this is
+		 * something that can happen if the dev_replace
+		 * procedure is suspended by an umount and then
+		 * the tgtdev is missing (or "btrfs dev scan") was
+		 * not called and the the filesystem is remounted
+		 * in degraded state. This does not stop the
+		 * dev_replace procedure. It needs to be canceled
+		 * manually if the cancelation is wanted.
+		 */
+		break;
+	}
+	return 1;
+}
+
+void btrfs_dev_replace_lock(struct btrfs_dev_replace *dev_replace)
+{
+	/* the beginning is just an optimization for the typical case */
+	if (atomic_read(&dev_replace->nesting_level) == 0) {
+acquire_lock:
+		/* this is not a nested case where the same thread
+		 * is trying to acqurire the same lock twice */
+		mutex_lock(&dev_replace->lock);
+		mutex_lock(&dev_replace->lock_management_lock);
+		dev_replace->lock_owner = current->pid;
+		atomic_inc(&dev_replace->nesting_level);
+		mutex_unlock(&dev_replace->lock_management_lock);
+		return;
+	}
+
+	mutex_lock(&dev_replace->lock_management_lock);
+	if (atomic_read(&dev_replace->nesting_level) > 0 &&
+	    dev_replace->lock_owner == current->pid) {
+		WARN_ON(!mutex_is_locked(&dev_replace->lock));
+		atomic_inc(&dev_replace->nesting_level);
+		mutex_unlock(&dev_replace->lock_management_lock);
+		return;
+	}
+
+	mutex_unlock(&dev_replace->lock_management_lock);
+	goto acquire_lock;
+}
+
+void btrfs_dev_replace_unlock(struct btrfs_dev_replace *dev_replace)
+{
+	WARN_ON(!mutex_is_locked(&dev_replace->lock));
+	mutex_lock(&dev_replace->lock_management_lock);
+	WARN_ON(atomic_read(&dev_replace->nesting_level) < 1);
+	WARN_ON(dev_replace->lock_owner != current->pid);
+	atomic_dec(&dev_replace->nesting_level);
+	if (atomic_read(&dev_replace->nesting_level) == 0) {
+		dev_replace->lock_owner = 0;
+		mutex_unlock(&dev_replace->lock_management_lock);
+		mutex_unlock(&dev_replace->lock);
+	} else {
+		mutex_unlock(&dev_replace->lock_management_lock);
+	}
+}

fs/btrfs/dev-replace.h

···
+/*
+ * Copyright (C) STRATO AG 2012.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#if !defined(__BTRFS_DEV_REPLACE__)
+#define __BTRFS_DEV_REPLACE__
+
+struct btrfs_ioctl_dev_replace_args;
+
+int btrfs_init_dev_replace(struct btrfs_fs_info *fs_info);
+int btrfs_run_dev_replace(struct btrfs_trans_handle *trans,
+			  struct btrfs_fs_info *fs_info);
+void btrfs_after_dev_replace_commit(struct btrfs_fs_info *fs_info);
+int btrfs_dev_replace_start(struct btrfs_root *root,
+			    struct btrfs_ioctl_dev_replace_args *args);
+void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info,
+			      struct btrfs_ioctl_dev_replace_args *args);
+int btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info,
+			     struct btrfs_ioctl_dev_replace_args *args);
+void btrfs_dev_replace_suspend_for_unmount(struct btrfs_fs_info *fs_info);
+int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info);
+int btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace);
+void btrfs_dev_replace_lock(struct btrfs_dev_replace *dev_replace);
+void btrfs_dev_replace_unlock(struct btrfs_dev_replace *dev_replace);
+
+static inline void btrfs_dev_replace_stats_inc(atomic64_t *stat_value)
+{
+	atomic64_inc(stat_value);
+}
+#endif

fs/btrfs/dir-item.c

···
 	return btrfs_match_dir_item_name(root, path, name, name_len);
 }
 
+int btrfs_check_dir_item_collision(struct btrfs_root *root, u64 dir,
+				   const char *name, int name_len)
+{
+	int ret;
+	struct btrfs_key key;
+	struct btrfs_dir_item *di;
+	int data_size;
+	struct extent_buffer *leaf;
+	int slot;
+	struct btrfs_path *path;
+
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = dir;
+	btrfs_set_key_type(&key, BTRFS_DIR_ITEM_KEY);
+	key.offset = btrfs_name_hash(name, name_len);
+
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+
+	/* return back any errors */
+	if (ret < 0)
+		goto out;
+
+	/* nothing found, we're safe */
+	if (ret > 0) {
+		ret = 0;
+		goto out;
+	}
+
+	/* we found an item, look for our name in the item */
+	di = btrfs_match_dir_item_name(root, path, name, name_len);
+	if (di) {
+		/* our exact name was found */
+		ret = -EEXIST;
+		goto out;
+	}
+
+	/*
+	 * see if there is room in the item to insert this
+	 * name
+	 */
+	data_size = sizeof(*di) + name_len + sizeof(struct btrfs_item);
+	leaf = path->nodes[0];
+	slot = path->slots[0];
+	if (data_size + btrfs_item_size_nr(leaf, slot) +
+	    sizeof(struct btrfs_item) > BTRFS_LEAF_DATA_SIZE(root)) {
+		ret = -EOVERFLOW;
+	} else {
+		/* plenty of insertion room */
+		ret = 0;
+	}
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
 /*
  * lookup a directory item based on index.  'dir' is the objectid
  * we're searching in, and 'mod' tells us if you plan on deleting the

fs/btrfs/disk-io.c

···
 #include "inode-map.h"
 #include "check-integrity.h"
 #include "rcu-string.h"
+#include "dev-replace.h"
 
 #ifdef CONFIG_X86
 #include <asm/cpufeature.h>
···
 		if (test_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags))
 			break;
 
-		num_copies = btrfs_num_copies(&root->fs_info->mapping_tree,
+		num_copies = btrfs_num_copies(root->fs_info,
 					      eb->start, eb->len);
 		if (num_copies == 1)
 			break;
···
 				 int mirror_num, unsigned long bio_flags,
 				 u64 bio_offset)
 {
+	int ret;
+
 	/*
 	 * when we're called for a write, we're already in the async
 	 * submission context.  Just jump into btrfs_map_bio
 	 */
-	return btrfs_map_bio(BTRFS_I(inode)->root, rw, bio, mirror_num, 1);
+	ret = btrfs_map_bio(BTRFS_I(inode)->root, rw, bio, mirror_num, 1);
+	if (ret)
+		bio_endio(bio, ret);
+	return ret;
 }
 
 static int check_async_write(struct inode *inode, unsigned long bio_flags)
···
 	int ret;
 
 	if (!(rw & REQ_WRITE)) {
-
 		/*
 		 * called for a read, do the setup so that checksum validation
 		 * can happen in the async kernel threads
···
 		ret = btrfs_bio_wq_end_io(BTRFS_I(inode)->root->fs_info,
 					  bio, 1);
 		if (ret)
-			return ret;
-		return btrfs_map_bio(BTRFS_I(inode)->root, rw, bio,
-				     mirror_num, 0);
+			goto out_w_error;
+		ret = btrfs_map_bio(BTRFS_I(inode)->root, rw, bio,
+				    mirror_num, 0);
 	} else if (!async) {
 		ret = btree_csum_one_bio(bio);
 		if (ret)
-			return ret;
-		return btrfs_map_bio(BTRFS_I(inode)->root, rw, bio,
-				     mirror_num, 0);
+			goto out_w_error;
+		ret = btrfs_map_bio(BTRFS_I(inode)->root, rw, bio,
+				    mirror_num, 0);
+	} else {
+		/*
+		 * kthread helpers are used to submit writes so that
+		 * checksumming can happen in parallel across all CPUs
+		 */
+		ret = btrfs_wq_submit_bio(BTRFS_I(inode)->root->fs_info,
+					  inode, rw, bio, mirror_num, 0,
+					  bio_offset,
+					  __btree_submit_bio_start,
+					  __btree_submit_bio_done);
 	}
 
-	/*
-	 * kthread helpers are used to submit writes so that checksumming
-	 * can happen in parallel across all CPUs
-	 */
-	return btrfs_wq_submit_bio(BTRFS_I(inode)->root->fs_info,
-				   inode, rw, bio, mirror_num, 0,
-				   bio_offset,
-				   __btree_submit_bio_start,
-				   __btree_submit_bio_done);
+	if (ret) {
+out_w_error:
+		bio_endio(bio, ret);
+	}
+	return ret;
 }
 
 #ifdef CONFIG_MIGRATION
···
 
 static int btree_set_page_dirty(struct page *page)
 {
+#ifdef DEBUG
 	struct extent_buffer *eb;
 
 	BUG_ON(!PagePrivate(page));
···
 	BUG_ON(!test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
 	BUG_ON(!atomic_read(&eb->refs));
 	btrfs_assert_tree_locked(eb);
+#endif
 	return __set_page_dirty_nobuffers(page);
 }
 
···
 					  root->fs_info->dirty_metadata_bytes);
 			}
 			spin_unlock(&root->fs_info->delalloc_lock);
-		}
 
-		/* ugh, clear_extent_buffer_dirty needs to lock the page */
-		btrfs_set_lock_blocking(buf);
-		clear_extent_buffer_dirty(buf);
+			/* ugh, clear_extent_buffer_dirty needs to lock the page */
+			btrfs_set_lock_blocking(buf);
+			clear_extent_buffer_dirty(buf);
+		}
 	}
 }
 
···
 	root->root_key.objectid = objectid;
 	root->anon_dev = 0;
 
-	spin_lock_init(&root->root_times_lock);
+	spin_lock_init(&root->root_item_lock);
 }
 
 static int __must_check find_and_setup_root(struct btrfs_root *tree_root,
···
 	init_rwsem(&fs_info->extent_commit_sem);
 	init_rwsem(&fs_info->cleanup_work_sem);
 	init_rwsem(&fs_info->subvol_sem);
+	fs_info->dev_replace.lock_owner = 0;
+	atomic_set(&fs_info->dev_replace.nesting_level, 0);
+	mutex_init(&fs_info->dev_replace.lock_finishing_cancel_unmount);
+	mutex_init(&fs_info->dev_replace.lock_management_lock);
+	mutex_init(&fs_info->dev_replace.lock);
 
 	spin_lock_init(&fs_info->qgroup_lock);
 	fs_info->qgroup_tree = RB_ROOT;
···
 			   fs_info->thread_pool_size,
 			   &fs_info->generic_worker);
 
+	btrfs_init_workers(&fs_info->flush_workers, "flush_delalloc",
+			   fs_info->thread_pool_size,
+			   &fs_info->generic_worker);
+
 	btrfs_init_workers(&fs_info->submit_workers, "submit",
 			   min_t(u64, fs_devices->num_devices,
 			   fs_info->thread_pool_size),
···
 	ret |= btrfs_start_workers(&fs_info->delayed_workers);
 	ret |= btrfs_start_workers(&fs_info->caching_workers);
 	ret |= btrfs_start_workers(&fs_info->readahead_workers);
+	ret |= btrfs_start_workers(&fs_info->flush_workers);
 	if (ret) {
 		err = -ENOMEM;
 		goto fail_sb_buffer;
···
 		goto fail_tree_roots;
 	}
 
-	btrfs_close_extra_devices(fs_devices);
+	/*
+	 * keep the device that is marked to be the target device for the
+	 * dev_replace procedure
+	 */
+	btrfs_close_extra_devices(fs_info, fs_devices, 0);
 
 	if (!fs_devices->latest_bdev) {
 		printk(KERN_CRIT "btrfs: failed to read devices on %s\n",
···
 		goto fail_block_groups;
 	}
 
+	ret = btrfs_init_dev_replace(fs_info);
+	if (ret) {
+		pr_err("btrfs: failed to init dev_replace: %d\n", ret);
+		goto fail_block_groups;
+	}
+
+	btrfs_close_extra_devices(fs_info, fs_devices, 1);
+
 	ret = btrfs_init_space_info(fs_info);
 	if (ret) {
 		printk(KERN_ERR "Failed to initial space info: %d\n", ret);
···
 	}
 	fs_info->num_tolerated_disk_barrier_failures =
 		btrfs_calc_num_tolerated_disk_barrier_failures(fs_info);
+	if (fs_info->fs_devices->missing_devices >
+	     fs_info->num_tolerated_disk_barrier_failures &&
+	    !(sb->s_flags & MS_RDONLY)) {
+		printk(KERN_WARNING
+		       "Btrfs: too many missing devices, writeable mount is not allowed\n");
+		goto fail_block_groups;
+	}
 
 	fs_info->cleaner_kthread = kthread_run(cleaner_kthread, tree_root,
 					       "btrfs-cleaner");
···
 		return ret;
 	}
 
+	ret = btrfs_resume_dev_replace_async(fs_info);
+	if (ret) {
+		pr_warn("btrfs: failed to resume dev_replace\n");
+		close_ctree(tree_root);
+		return ret;
+	}
+
 	return 0;
 
 fail_qgroup:
···
 	btrfs_stop_workers(&fs_info->submit_workers);
 	btrfs_stop_workers(&fs_info->delayed_workers);
 	btrfs_stop_workers(&fs_info->caching_workers);
+	btrfs_stop_workers(&fs_info->flush_workers);
 fail_alloc:
 fail_iput:
 	btrfs_mapping_tree_free(&fs_info->mapping_tree);
···
 	smp_mb();
 
 	/* pause restriper - we want to resume on mount */
-	btrfs_pause_balance(root->fs_info);
+	btrfs_pause_balance(fs_info);
 
-	btrfs_scrub_cancel(root);
+	btrfs_dev_replace_suspend_for_unmount(fs_info);
+
+	btrfs_scrub_cancel(fs_info);
 
 	/* wait for any defraggers to finish */
 	wait_event(fs_info->transaction_wait,
 		   (atomic_read(&fs_info->defrag_running) == 0));
 
 	/* clear out the rbtree of defraggable inodes */
-	btrfs_run_defrag_inodes(fs_info);
+	btrfs_cleanup_defrag_inodes(fs_info);
 
 	if (!(fs_info->sb->s_flags & MS_RDONLY)) {
 		ret = btrfs_commit_super(root);
···
 	btrfs_stop_workers(&fs_info->delayed_workers);
 	btrfs_stop_workers(&fs_info->caching_workers);
 	btrfs_stop_workers(&fs_info->readahead_workers);
+	btrfs_stop_workers(&fs_info->flush_workers);
 
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 	if (btrfs_test_opt(root, CHECK_INTEGRITY))
···
 	int was_dirty;
 
 	btrfs_assert_tree_locked(buf);
-	if (transid != root->fs_info->generation) {
-		printk(KERN_CRIT "btrfs transid mismatch buffer %llu, "
+	if (transid != root->fs_info->generation)
+		WARN(1, KERN_CRIT "btrfs transid mismatch buffer %llu, "
 		       "found %llu running %llu\n",
 			(unsigned long long)buf->start,
 			(unsigned long long)transid,
 			(unsigned long long)root->fs_info->generation);
-		WARN_ON(1);
-	}
 	was_dirty = set_extent_buffer_dirty(buf);
 	if (!was_dirty) {
 		spin_lock(&root->fs_info->delalloc_lock);
···
 	}
 }
 
-void btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr)
+static void __btrfs_btree_balance_dirty(struct btrfs_root *root,
+					int flush_delayed)
 {
 	/*
 	 * looks as though older kernels can get into trouble with
···
 	if (current->flags & PF_MEMALLOC)
 		return;
 
-	btrfs_balance_delayed_items(root);
+	if (flush_delayed)
+		btrfs_balance_delayed_items(root);
 
 	num_dirty = root->fs_info->dirty_metadata_bytes;
 
···
 	return;
 }
 
-void __btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr)
+void btrfs_btree_balance_dirty(struct btrfs_root *root)
 {
-	/*
-	 * looks as though older kernels can get into trouble with
-	 * this code, they end up stuck in balance_dirty_pages forever
-	 */
-	u64 num_dirty;
-	unsigned long thresh = 32 * 1024 * 1024;
+	__btrfs_btree_balance_dirty(root, 1);
+}
 
-	if (current->flags & PF_MEMALLOC)
-		return;
-
-	num_dirty = root->fs_info->dirty_metadata_bytes;
-
-	if (num_dirty > thresh) {
-		balance_dirty_pages_ratelimited(
-				   root->fs_info->btree_inode->i_mapping);
-	}
-	return;
+void btrfs_btree_balance_dirty_nodelay(struct btrfs_root *root)
+{
+	__btrfs_btree_balance_dirty(root, 0);
 }
 
 int btrfs_read_buffer(struct extent_buffer *buf, u64 parent_transid)

fs/btrfs/disk-io.h

···
 struct btrfs_root *btrfs_read_fs_root_no_name(struct btrfs_fs_info *fs_info,
 					      struct btrfs_key *location);
 int btrfs_cleanup_fs_roots(struct btrfs_fs_info *fs_info);
-void btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr);
-void __btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr);
+void btrfs_btree_balance_dirty(struct btrfs_root *root);
+void btrfs_btree_balance_dirty_nodelay(struct btrfs_root *root);
 void btrfs_free_fs_root(struct btrfs_fs_info *fs_info, struct btrfs_root *root);
 void btrfs_mark_buffer_dirty(struct extent_buffer *buf);
 int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid,

fs/btrfs/extent-tree.c

···
 #include "volumes.h"
 #include "locking.h"
 #include "free-space-cache.h"
+#include "math.h"
 
 #undef SCRAMBLE_DELAYED_REFS
 
···
 	list_for_each_entry_rcu(found, head, list)
 		found->full = 0;
 	rcu_read_unlock();
-}
-
-static u64 div_factor(u64 num, int factor)
-{
-	if (factor == 10)
-		return num;
-	num *= factor;
-	do_div(num, 10);
-	return num;
-}
-
-static u64 div_factor_fine(u64 num, int factor)
-{
-	if (factor == 100)
-		return num;
-	num *= factor;
-	do_div(num, 100);
-	return num;
 }
 
 u64 btrfs_find_block_group(struct btrfs_root *root,
···
 
 
 	/* Tell the block device(s) that the sectors can be discarded */
-	ret = btrfs_map_block(&root->fs_info->mapping_tree, REQ_DISCARD,
+	ret = btrfs_map_block(root->fs_info, REQ_DISCARD,
 			      bytenr, &num_bytes, &bbio, 0);
 	/* Error condition is -ENOMEM */
 	if (!ret) {
···
 				kfree(extent_op);
 
 				if (ret) {
+					list_del_init(&locked_ref->cluster);
+					mutex_unlock(&locked_ref->mutex);
+
 					printk(KERN_DEBUG "btrfs: run_delayed_extent_op returned %d\n", ret);
 					spin_lock(&delayed_refs->lock);
 					return ret;
···
 		count++;
 
 		if (ret) {
+			if (locked_ref) {
+				list_del_init(&locked_ref->cluster);
+				mutex_unlock(&locked_ref->mutex);
+			}
 			printk(KERN_DEBUG "btrfs: run_one_delayed_ref returned %d\n", ret);
 			spin_lock(&delayed_refs->lock);
 			return ret;
···
 
 static int can_overcommit(struct btrfs_root *root,
 			  struct btrfs_space_info *space_info, u64 bytes,
-			  int flush)
+			  enum btrfs_reserve_flush_enum flush)
 {
 	u64 profile = btrfs_get_alloc_profile(root, 0);
 	u64 avail;
···
 		avail >>= 1;
 
 	/*
-	 * If we aren't flushing don't let us overcommit too much, say
-	 * 1/8th of the space.  If we can flush, let it overcommit up to
-	 * 1/2 of the space.
+	 * If we aren't flushing all things, let us overcommit up to
+	 * 1/2th of the space. If we can flush, don't let us overcommit
+	 * too much, let it overcommit up to 1/8 of the space.
 	 */
-	if (flush)
+	if (flush == BTRFS_RESERVE_FLUSH_ALL)
 		avail >>= 3;
 	else
 		avail >>= 1;
 
 	if (used + bytes < space_info->total_bytes + avail)
 		return 1;
+	return 0;
+}
+
+static int writeback_inodes_sb_nr_if_idle_safe(struct super_block *sb,
+					       unsigned long nr_pages,
+					       enum wb_reason reason)
+{
+	if (!writeback_in_progress(sb->s_bdi) &&
+	    down_read_trylock(&sb->s_umount)) {
+		writeback_inodes_sb_nr(sb, nr_pages, reason);
+		up_read(&sb->s_umount);
+		return 1;
+	}
+
 	return 0;
 }
 
···
 	long time_left;
 	unsigned long nr_pages = (2 * 1024 * 1024) >> PAGE_CACHE_SHIFT;
 	int loops = 0;
+	enum btrfs_reserve_flush_enum flush;
 
 	trans = (struct btrfs_trans_handle *)current->journal_info;
 	block_rsv = &root->fs_info->delalloc_block_rsv;
···
 	while (delalloc_bytes && loops < 3) {
 		max_reclaim = min(delalloc_bytes, to_reclaim);
 		nr_pages = max_reclaim >> PAGE_CACHE_SHIFT;
-		writeback_inodes_sb_nr_if_idle(root->fs_info->sb, nr_pages,
-					       WB_REASON_FS_FREE_SPACE);
+		writeback_inodes_sb_nr_if_idle_safe(root->fs_info->sb,
+						    nr_pages,
+						    WB_REASON_FS_FREE_SPACE);
 
 		/*
 		 * We need to wait for the async pages to actually start before
···
 		wait_event(root->fs_info->async_submit_wait,
 			   !atomic_read(&root->fs_info->async_delalloc_pages));
 
+		if (!trans)
+			flush = BTRFS_RESERVE_FLUSH_ALL;
+		else
+			flush = BTRFS_RESERVE_NO_FLUSH;
 		spin_lock(&space_info->lock);
-		if (can_overcommit(root, space_info, orig, !trans)) {
+		if (can_overcommit(root, space_info, orig, flush)) {
 			spin_unlock(&space_info->lock);
 			break;
 		}
···
  */
 static int reserve_metadata_bytes(struct btrfs_root *root,
 				  struct btrfs_block_rsv *block_rsv,
-				  u64 orig_bytes, int flush)
+				  u64 orig_bytes,
+				  enum btrfs_reserve_flush_enum flush)
 {
 	struct btrfs_space_info *space_info = block_rsv->space_info;
 	u64 used;
···
 	ret = 0;
 	spin_lock(&space_info->lock);
 	/*
-	 * We only want to wait if somebody other than us is flushing and we are
-	 * actually alloed to flush.
+	 * We only want to wait if somebody other than us is flushing and we
+	 * are actually allowed to flush all things.
 	 */
-	while (flush && !flushing && space_info->flush) {
+	while (flush == BTRFS_RESERVE_FLUSH_ALL && !flushing &&
+	       space_info->flush) {
 		spin_unlock(&space_info->lock);
 		/*
 		 * If we have a trans handle we can't wait because the flusher
···
 	 * Couldn't make our reservation, save our place so while we're trying
 	 * to reclaim space we can actually use it instead of somebody else
 	 * stealing it from us.
+	 *
+	 * We make the other tasks wait for the flush only when we can flush
+	 * all things.
 	 */
-	if (ret && flush) {
+	if (ret && flush == BTRFS_RESERVE_FLUSH_ALL) {
 		flushing = true;
 		space_info->flush = 1;
 	}
 
 	spin_unlock(&space_info->lock);
 
-	if (!ret || !flush)
+	if (!ret || flush == BTRFS_RESERVE_NO_FLUSH)
 		goto out;
 
 	ret = flush_space(root, space_info, num_bytes, orig_bytes,
 			  flush_state);
 	flush_state++;
+
+	/*
+	 * If we are FLUSH_LIMIT, we can not flush delalloc, or the deadlock
+	 * would happen. So skip delalloc flush.
+	 */
+	if (flush == BTRFS_RESERVE_FLUSH_LIMIT &&
+	    (flush_state == FLUSH_DELALLOC ||
+	     flush_state == FLUSH_DELALLOC_WAIT))
+		flush_state = ALLOC_CHUNK;
+
 	if (!ret)
 		goto again;
-	else if (flush_state <= COMMIT_TRANS)
+	else if (flush == BTRFS_RESERVE_FLUSH_LIMIT &&
+		 flush_state < COMMIT_TRANS)
+		goto again;
+	else if (flush == BTRFS_RESERVE_FLUSH_ALL &&
+		 flush_state <= COMMIT_TRANS)
 		goto again;
 
 out:
···
 	kfree(rsv);
 }
 
-static inline int __block_rsv_add(struct btrfs_root *root,
-				  struct btrfs_block_rsv *block_rsv,
-				  u64 num_bytes, int flush)
+int btrfs_block_rsv_add(struct btrfs_root *root,
+			struct btrfs_block_rsv *block_rsv, u64 num_bytes,
+			enum btrfs_reserve_flush_enum flush)
 {
 	int ret;
 
···
 	}
 
 	return ret;
-}
-
-int btrfs_block_rsv_add(struct btrfs_root *root,
-			struct btrfs_block_rsv *block_rsv,
-			u64 num_bytes)
-{
-	return __block_rsv_add(root, block_rsv, num_bytes, 1);
-}
-
-int btrfs_block_rsv_add_noflush(struct btrfs_root *root,
-				struct btrfs_block_rsv *block_rsv,
-				u64 num_bytes)
-{
-	return __block_rsv_add(root, block_rsv, num_bytes, 0);
 }
 
 int btrfs_block_rsv_check(struct btrfs_root *root,
···
 	return ret;
 }
 
-static inline int __btrfs_block_rsv_refill(struct btrfs_root *root,
-					   struct btrfs_block_rsv *block_rsv,
-					   u64 min_reserved, int flush)
+int btrfs_block_rsv_refill(struct btrfs_root *root,
+			   struct btrfs_block_rsv *block_rsv, u64 min_reserved,
+			   enum btrfs_reserve_flush_enum flush)
 {
 	u64 num_bytes = 0;
 	int ret = -ENOSPC;
···
 	}
 
 	return ret;
-}
-
-int btrfs_block_rsv_refill(struct btrfs_root *root,
-			   struct btrfs_block_rsv *block_rsv,
-			   u64 min_reserved)
-{
-	return __btrfs_block_rsv_refill(root, block_rsv, min_reserved, 1);
-}
-
-int btrfs_block_rsv_refill_noflush(struct btrfs_root *root,
-				   struct btrfs_block_rsv *block_rsv,
-				   u64 min_reserved)
-{
-	return __btrfs_block_rsv_refill(root, block_rsv, min_reserved, 0);
 }
 
 int btrfs_block_rsv_migrate(struct btrfs_block_rsv *src_rsv,
···
 	u64 csum_bytes;
 	unsigned nr_extents = 0;
 	int extra_reserve = 0;
-	int flush = 1;
+	enum btrfs_reserve_flush_enum flush = BTRFS_RESERVE_FLUSH_ALL;
 	int ret;
+	bool delalloc_lock = true;
 
-	/* Need to be holding the i_mutex here if we aren't free space cache */
-	if (btrfs_is_free_space_inode(inode))
-		flush = 0;
+	/* If we are a free space inode we need to not flush since we will be in
+	 * the middle of a transaction commit.  We also don't need the delalloc
+	 * mutex since we won't race with anybody.  We need this mostly to make
+	 * lockdep shut its filthy mouth.
+	 */
+	if (btrfs_is_free_space_inode(inode)) {
+		flush = BTRFS_RESERVE_NO_FLUSH;
+		delalloc_lock = false;
+	}
 
-	if (flush && btrfs_transaction_in_commit(root->fs_info))
+	if (flush != BTRFS_RESERVE_NO_FLUSH &&
+	    btrfs_transaction_in_commit(root->fs_info))
 		schedule_timeout(1);
 
-	mutex_lock(&BTRFS_I(inode)->delalloc_mutex);
+	if (delalloc_lock)
+		mutex_lock(&BTRFS_I(inode)->delalloc_mutex);
+
 	num_bytes = ALIGN(num_bytes, root->sectorsize);
 
 	spin_lock(&BTRFS_I(inode)->lock);
···
 		ret = btrfs_qgroup_reserve(root, num_bytes +
 					   nr_extents * root->leafsize);
 		if (ret) {
-			mutex_unlock(&BTRFS_I(inode)->delalloc_mutex);
+			spin_lock(&BTRFS_I(inode)->lock);
+			calc_csum_metadata_size(inode, num_bytes, 0);
+			spin_unlock(&BTRFS_I(inode)->lock);
+			if (delalloc_lock)
+				mutex_unlock(&BTRFS_I(inode)->delalloc_mutex);
 			return ret;
 		}
 	}
···
 						      btrfs_ino(inode),
 						      to_free, 0);
 		}
-		mutex_unlock(&BTRFS_I(inode)->delalloc_mutex);
+		if (root->fs_info->quota_enabled) {
+			btrfs_qgroup_free(root, num_bytes +
+						nr_extents * root->leafsize);
+		}
+		if (delalloc_lock)
+			mutex_unlock(&BTRFS_I(inode)->delalloc_mutex);
 		return ret;
 	}
 
···
 	}
 	BTRFS_I(inode)->reserved_extents += nr_extents;
 	spin_unlock(&BTRFS_I(inode)->lock);
-	mutex_unlock(&BTRFS_I(inode)->delalloc_mutex);
+
+	if (delalloc_lock)
+		mutex_unlock(&BTRFS_I(inode)->delalloc_mutex);
 
 	if (to_reserve)
 		trace_btrfs_space_reservation(root->fs_info,"delalloc",
···
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct btrfs_block_group_cache *cache = NULL;
+	struct btrfs_space_info *space_info;
+	struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
 	u64 len;
+	bool readonly;
 
 	while (start <= end) {
+		readonly = false;
 		if (!cache ||
 		    start >= cache->key.objectid + cache->key.offset) {
 			if (cache)
···
 		}
 
 		start += len;
+		space_info = cache->space_info;
 
-		spin_lock(&cache->space_info->lock);
+		spin_lock(&space_info->lock);
 		spin_lock(&cache->lock);
 		cache->pinned -= len;
-		cache->space_info->bytes_pinned -= len;
-		if (cache->ro)
-			cache->space_info->bytes_readonly += len;
+		space_info->bytes_pinned -= len;
+		if (cache->ro) {
+			space_info->bytes_readonly += len;
+			readonly = true;
+		}
 		spin_unlock(&cache->lock);
-		spin_unlock(&cache->space_info->lock);
+		if (!readonly && global_rsv->space_info == space_info) {
+			spin_lock(&global_rsv->lock);
+			if (!global_rsv->full) {
+				len = min(len, global_rsv->size -
+					  global_rsv->reserved);
+				global_rsv->reserved += len;
+				space_info->bytes_may_use += len;
+				if (global_rsv->reserved >= global_rsv->size)
+					global_rsv->full = 1;
+			}
+			spin_unlock(&global_rsv->lock);
+		}
+		spin_unlock(&space_info->lock);
 	}
 
 	if (cache)
···
 	return 0;
 }
 
-static int __get_block_group_index(u64 flags)
+int __get_raid_index(u64 flags)
 {
 	int index;
 
···
 
 static int get_block_group_index(struct btrfs_block_group_cache *cache)
 {
-	return __get_block_group_index(cache->flags);
+	return __get_raid_index(cache->flags);
 }
 
 enum btrfs_loop_type {
···
 	block_rsv = get_block_rsv(trans, root);
 
 	if (block_rsv->size == 0) {
-		ret = reserve_metadata_bytes(root, block_rsv, blocksize, 0);
+		ret = reserve_metadata_bytes(root, block_rsv, blocksize,
+					     BTRFS_RESERVE_NO_FLUSH);
 		/*
 		 * If we couldn't reserve metadata bytes try and use some from
 		 * the global reserve.
···
 		static DEFINE_RATELIMIT_STATE(_rs,
 				DEFAULT_RATELIMIT_INTERVAL,
 				/*DEFAULT_RATELIMIT_BURST*/ 2);
-		if (__ratelimit(&_rs)) {
-			printk(KERN_DEBUG "btrfs: block rsv returned %d\n", ret);
-			WARN_ON(1);
-		}
-		ret = reserve_metadata_bytes(root, block_rsv, blocksize, 0);
+		if (__ratelimit(&_rs))
+			WARN(1, KERN_DEBUG "btrfs: block rsv returned %d\n",
+			     ret);
+		ret = reserve_metadata_bytes(root, block_rsv, blocksize,
+					     BTRFS_RESERVE_NO_FLUSH);
 		if (!ret) {
 			return block_rsv;
 		} else if (ret && block_rsv != global_rsv) {
···
 	 */
 	target = get_restripe_target(root->fs_info, block_group->flags);
 	if (target) {
-		index = __get_block_group_index(extended_to_chunk(target));
+		index = __get_raid_index(extended_to_chunk(target));
 	} else {
 		/*
 		 * this is just a balance, so if we were marked as full
···
 		 * check to make sure we can actually find a chunk with enough
 		 * space to fit our block group in.
 		 */
-		if (device->total_bytes > device->bytes_used + min_free) {
+		if (device->total_bytes > device->bytes_used + min_free &&
+		    !device->is_tgtdev_for_dev_replace) {
 			ret = find_free_dev_extent(device, min_free,
 						   &dev_offset, NULL);
 			if (!ret)

fs/btrfs/extent_io.c

···
 {
 	struct rb_node *node;
 
-	if (end < start) {
-		printk(KERN_ERR "btrfs end < start %llu %llu\n",
+	if (end < start)
+		WARN(1, KERN_ERR "btrfs end < start %llu %llu\n",
 		       (unsigned long long)end,
 		       (unsigned long long)start);
-		WARN_ON(1);
-	}
 	state->start = start;
 	state->end = end;
 
···
  * the standard behavior is to write all copies in a raid setup. here we only
  * want to write the one bad copy. so we do the mapping for ourselves and issue
  * submit_bio directly.
- * to avoid any synchonization issues, wait for the data after writing, which
+ * to avoid any synchronization issues, wait for the data after writing, which
  * actually prevents the read that triggered the error from finishing.
  * currently, there can be no more than two copies of every data bit. thus,
  * exactly one rewrite is required.
  */
-int repair_io_failure(struct btrfs_mapping_tree *map_tree, u64 start,
+int repair_io_failure(struct btrfs_fs_info *fs_info, u64 start,
 			u64 length, u64 logical, struct page *page,
 			int mirror_num)
 {
···
 	bio->bi_size = 0;
 	map_length = length;
 
-	ret = btrfs_map_block(map_tree, WRITE, logical,
+	ret = btrfs_map_block(fs_info, WRITE, logical,
 			      &map_length, &bbio, mirror_num);
 	if (ret) {
 		bio_put(bio);
···
 int repair_eb_io_failure(struct btrfs_root *root, struct extent_buffer *eb,
 			 int mirror_num)
 {
-	struct btrfs_mapping_tree *map_tree = &root->fs_info->mapping_tree;
 	u64 start = eb->start;
 	unsigned long i, num_pages = num_extent_pages(eb->start, eb->len);
 	int ret = 0;
 
 	for (i = 0; i < num_pages; i++) {
 		struct page *p = extent_buffer_page(eb, i);
-		ret = repair_io_failure(map_tree, start, PAGE_CACHE_SIZE,
+		ret = repair_io_failure(root->fs_info, start, PAGE_CACHE_SIZE,
 					start, p, mirror_num);
 		if (ret)
 			break;
···
 	u64 private;
 	u64 private_failure;
 	struct io_failure_record *failrec;
-	struct btrfs_mapping_tree *map_tree;
+	struct btrfs_fs_info *fs_info;
 	struct extent_state *state;
 	int num_copies;
 	int did_repair = 0;
···
 	spin_unlock(&BTRFS_I(inode)->io_tree.lock);
 
 	if (state && state->start == failrec->start) {
-		map_tree = &BTRFS_I(inode)->root->fs_info->mapping_tree;
-		num_copies = btrfs_num_copies(map_tree, failrec->logical,
-						failrec->len);
+		fs_info = BTRFS_I(inode)->root->fs_info;
+		num_copies = btrfs_num_copies(fs_info, failrec->logical,
+					      failrec->len);
 		if (num_copies > 1)  {
-			ret = repair_io_failure(map_tree, start, failrec->len,
+			ret = repair_io_failure(fs_info, start, failrec->len,
 						failrec->logical, page,
 						failrec->failed_mirror);
 			did_repair = !ret;
···
 		 * clean_io_failure() clean all those errors at once.
 		 */
 	}
-	num_copies = btrfs_num_copies(
-			      &BTRFS_I(inode)->root->fs_info->mapping_tree,
-			      failrec->logical, failrec->len);
+	num_copies = btrfs_num_copies(BTRFS_I(inode)->root->fs_info,
+				      failrec->logical, failrec->len);
 	if (num_copies == 1) {
 		/*
 		 * we only have a single copy of the data, so don't bother with
···
 	return bio;
 }
 
-/*
- * Since writes are async, they will only return -ENOMEM.
- * Reads can return the full range of I/O error conditions.
- */
 static int __must_check submit_one_bio(int rw, struct bio *bio,
 				       int mirror_num, unsigned long bio_flags)
 {
···
 	}
 
 	if (start + min_len > eb->len) {
-		printk(KERN_ERR "btrfs bad mapping eb start %llu len %lu, "
+		WARN(1, KERN_ERR "btrfs bad mapping eb start %llu len %lu, "
 		       "wanted %lu %lu\n", (unsigned long long)eb->start,
 		       eb->len, start, min_len);
-		WARN_ON(1);
 		return -EINVAL;
 	}
 

fs/btrfs/extent_io.h

···
 btrfs_bio_alloc(struct block_device *bdev, u64 first_sector, int nr_vecs,
 		gfp_t gfp_flags);
 
-struct btrfs_mapping_tree;
+struct btrfs_fs_info;
 
-int repair_io_failure(struct btrfs_mapping_tree *map_tree, u64 start,
+int repair_io_failure(struct btrfs_fs_info *fs_info, u64 start,
 			u64 length, u64 logical, struct page *page,
 			int mirror_num);
 int end_extent_writepage(struct page *page, int err, u64 start, u64 end);

fs/btrfs/extent_map.c

···
 struct extent_map *alloc_extent_map(void)
 {
 	struct extent_map *em;
-	em = kmem_cache_alloc(extent_map_cache, GFP_NOFS);
+	em = kmem_cache_zalloc(extent_map_cache, GFP_NOFS);
 	if (!em)
 		return NULL;
 	em->in_tree = 0;
···
 			merge = rb_entry(rb, struct extent_map, rb_node);
 		if (rb && mergable_maps(merge, em)) {
 			em->start = merge->start;
+			em->orig_start = merge->orig_start;
 			em->len += merge->len;
 			em->block_len += merge->block_len;
 			em->block_start = merge->block_start;
 			merge->in_tree = 0;
-			if (merge->generation > em->generation) {
-				em->mod_start = em->start;
-				em->mod_len = em->len;
-				em->generation = merge->generation;
-				list_move(&em->list, &tree->modified_extents);
-			}
+			em->mod_len = (em->mod_len + em->mod_start) - merge->mod_start;
+			em->mod_start = merge->mod_start;
+			em->generation = max(em->generation, merge->generation);
+			list_move(&em->list, &tree->modified_extents);
 
 			list_del_init(&merge->list);
 			rb_erase(&merge->rb_node, &tree->map);
···
 		em->block_len += merge->len;
 		rb_erase(&merge->rb_node, &tree->map);
 		merge->in_tree = 0;
-		if (merge->generation > em->generation) {
-			em->mod_len = em->len;
-			em->generation = merge->generation;
-			list_move(&em->list, &tree->modified_extents);
-		}
+		em->mod_len = (merge->mod_start + merge->mod_len) - em->mod_start;
+		em->generation = max(em->generation, merge->generation);
 		list_del_init(&merge->list);
 		free_extent_map(merge);
 	}
···
 	em->mod_start = em->start;
 	em->mod_len = em->len;
 
-	if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) {
+	if (test_bit(EXTENT_FLAG_FILLING, &em->flags)) {
 		prealloc = true;
-		clear_bit(EXTENT_FLAG_PREALLOC, &em->flags);
+		clear_bit(EXTENT_FLAG_FILLING, &em->flags);
 	}
 
 	try_merge_map(tree, em);

fs/btrfs/extent_map.h

···
 #define EXTENT_FLAG_VACANCY 2 /* no file extent item found */
 #define EXTENT_FLAG_PREALLOC 3 /* pre-allocated extent */
 #define EXTENT_FLAG_LOGGING 4 /* Logging this extent */
+#define EXTENT_FLAG_FILLING 5 /* Filling in a preallocated extent */
 
 struct extent_map {
 	struct rb_node rb_node;
···
 	u64 mod_start;
 	u64 mod_len;
 	u64 orig_start;
+	u64 orig_block_len;
 	u64 block_start;
 	u64 block_len;
 	u64 generation;

fs/btrfs/file-item.c

···
 	return ERR_PTR(ret);
 }
 
-
 int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root,
 			     struct btrfs_path *path, u64 objectid,
···
 	return ret;
 }
 
+u64 btrfs_file_extent_length(struct btrfs_path *path)
+{
+	int extent_type;
+	struct btrfs_file_extent_item *fi;
+	u64 len;
+
+	fi = btrfs_item_ptr(path->nodes[0], path->slots[0],
+			    struct btrfs_file_extent_item);
+	extent_type = btrfs_file_extent_type(path->nodes[0], fi);
+
+	if (extent_type == BTRFS_FILE_EXTENT_REG ||
+	    extent_type == BTRFS_FILE_EXTENT_PREALLOC)
+		len = btrfs_file_extent_num_bytes(path->nodes[0], fi);
+	else if (extent_type == BTRFS_FILE_EXTENT_INLINE)
+		len = btrfs_file_extent_inline_len(path->nodes[0], fi);
+	else
+		BUG();
+
+	return len;
+}
 
 static int __btrfs_lookup_bio_sums(struct btrfs_root *root,
 				   struct inode *inode, struct bio *bio,

fs/btrfs/file.c

···
 #include "compat.h"
 #include "volumes.h"
 
+static struct kmem_cache *btrfs_inode_defrag_cachep;
 /*
  * when auto defrag is enabled we
  * queue up these defrag structs to remember which
···
  * If an existing record is found the defrag item you
  * pass in is freed
  */
-static void __btrfs_add_inode_defrag(struct inode *inode,
+static int __btrfs_add_inode_defrag(struct inode *inode,
 				    struct inode_defrag *defrag)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
···
 				entry->transid = defrag->transid;
 			if (defrag->last_offset > entry->last_offset)
 				entry->last_offset = defrag->last_offset;
-			goto exists;
+			return -EEXIST;
 		}
 	}
 	set_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags);
 	rb_link_node(&defrag->rb_node, parent, p);
 	rb_insert_color(&defrag->rb_node, &root->fs_info->defrag_inodes);
-	return;
+	return 0;
+}
 
-exists:
-	kfree(defrag);
-	return;
+static inline int __need_auto_defrag(struct btrfs_root *root)
+{
+	if (!btrfs_test_opt(root, AUTO_DEFRAG))
+		return 0;
 
+	if (btrfs_fs_closing(root->fs_info))
+		return 0;
+
+	return 1;
 }
 
 /*
···
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct inode_defrag *defrag;
 	u64 transid;
+	int ret;
 
-	if (!btrfs_test_opt(root, AUTO_DEFRAG))
-		return 0;
-
-	if (btrfs_fs_closing(root->fs_info))
+	if (!__need_auto_defrag(root))
 		return 0;
 
 	if (test_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags))
···
 	else
 		transid = BTRFS_I(inode)->root->last_trans;
 
-	defrag = kzalloc(sizeof(*defrag), GFP_NOFS);
+	defrag = kmem_cache_zalloc(btrfs_inode_defrag_cachep, GFP_NOFS);
 	if (!defrag)
 		return -ENOMEM;
 
···
 	defrag->root = root->root_key.objectid;
 
 	spin_lock(&root->fs_info->defrag_inodes_lock);
-	if (!test_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags))
-		__btrfs_add_inode_defrag(inode, defrag);
-	else
-		kfree(defrag);
+	if (!test_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags)) {
+		/*
+		 * If we set IN_DEFRAG flag and evict the inode from memory,
+		 * and then re-read this inode, this new inode doesn't have
+		 * IN_DEFRAG flag. At the case, we may find the existed defrag.
+		 */
+		ret = __btrfs_add_inode_defrag(inode, defrag);
+		if (ret)
+			kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
+	} else {
+		kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
+	}
 	spin_unlock(&root->fs_info->defrag_inodes_lock);
 	return 0;
 }
 
 /*
- * must be called with the defrag_inodes lock held
+ * Requeue the defrag object. If there is a defrag object that points to
+ * the same inode in the tree, we will merge them together (by
+ * __btrfs_add_inode_defrag()) and free the one that we want to requeue.
  */
-struct inode_defrag *btrfs_find_defrag_inode(struct btrfs_fs_info *info,
-					     u64 root, u64 ino,
-					     struct rb_node **next)
+void btrfs_requeue_inode_defrag(struct inode *inode,
+				struct inode_defrag *defrag)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	int ret;
+
+	if (!__need_auto_defrag(root))
+		goto out;
+
+	/*
+	 * Here we don't check the IN_DEFRAG flag, because we need merge
+	 * them together.
+	 */
+	spin_lock(&root->fs_info->defrag_inodes_lock);
+	ret = __btrfs_add_inode_defrag(inode, defrag);
+	spin_unlock(&root->fs_info->defrag_inodes_lock);
+	if (ret)
+		goto out;
+	return;
+out:
+	kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
+}
+
+/*
+ * pick the defragable inode that we want, if it doesn't exist, we will get
+ * the next one.
+ */
+static struct inode_defrag *
+btrfs_pick_defrag_inode(struct btrfs_fs_info *fs_info, u64 root, u64 ino)
 {
 	struct inode_defrag *entry = NULL;
 	struct inode_defrag tmp;
···
 	tmp.ino = ino;
 	tmp.root = root;
 
-	p = info->defrag_inodes.rb_node;
+	spin_lock(&fs_info->defrag_inodes_lock);
+	p = fs_info->defrag_inodes.rb_node;
 	while (p) {
 		parent = p;
 		entry = rb_entry(parent, struct inode_defrag, rb_node);
···
 		else if (ret > 0)
 			p = parent->rb_right;
 		else
-			return entry;
+			goto out;
 	}
 
-	if (next) {
-		while (parent && __compare_inode_defrag(&tmp, entry) > 0) {
-			parent = rb_next(parent);
+	if (parent && __compare_inode_defrag(&tmp, entry) > 0) {
+		parent = rb_next(parent);
+		if (parent)
 			entry = rb_entry(parent, struct inode_defrag, rb_node);
-		}
-		*next = parent;
+		else
+			entry = NULL;
 	}
-	return NULL;
+out:
+	if (entry)
+		rb_erase(parent, &fs_info->defrag_inodes);
+	spin_unlock(&fs_info->defrag_inodes_lock);
+	return entry;
+}
+
+void btrfs_cleanup_defrag_inodes(struct btrfs_fs_info *fs_info)
+{
+	struct inode_defrag *defrag;
+	struct rb_node *node;
+
+	spin_lock(&fs_info->defrag_inodes_lock);
+	node = rb_first(&fs_info->defrag_inodes);
+	while (node) {
+		rb_erase(node, &fs_info->defrag_inodes);
+		defrag = rb_entry(node, struct inode_defrag, rb_node);
+		kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
+
+		if (need_resched()) {
+			spin_unlock(&fs_info->defrag_inodes_lock);
+			cond_resched();
+			spin_lock(&fs_info->defrag_inodes_lock);
+		}
+
+		node = rb_first(&fs_info->defrag_inodes);
+	}
+	spin_unlock(&fs_info->defrag_inodes_lock);
+}
+
+#define BTRFS_DEFRAG_BATCH	1024
+
+static int __btrfs_run_defrag_inode(struct btrfs_fs_info *fs_info,
+				    struct inode_defrag *defrag)
+{
+	struct btrfs_root *inode_root;
+	struct inode *inode;
+	struct btrfs_key key;
+	struct btrfs_ioctl_defrag_range_args range;
+	int num_defrag;
+
+	/* get the inode */
+	key.objectid = defrag->root;
+	btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);
+	key.offset = (u64)-1;
+	inode_root = btrfs_read_fs_root_no_name(fs_info, &key);
+	if (IS_ERR(inode_root)) {
+		kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
+		return PTR_ERR(inode_root);
+	}
+
+	key.objectid = defrag->ino;
+	btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
+	key.offset = 0;
+	inode = btrfs_iget(fs_info->sb, &key, inode_root, NULL);
+	if (IS_ERR(inode)) {
+		kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
+		return PTR_ERR(inode);
+	}
+
+	/* do a chunk of defrag */
+	clear_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags);
+	memset(&range, 0, sizeof(range));
+	range.len = (u64)-1;
+	range.start = defrag->last_offset;
+
+	sb_start_write(fs_info->sb);
+	num_defrag = btrfs_defrag_file(inode, NULL, &range, defrag->transid,
+				       BTRFS_DEFRAG_BATCH);
+	sb_end_write(fs_info->sb);
+	/*
+	 * if we filled the whole defrag batch, there
+	 * must be more work to do.  Queue this defrag
+	 * again
+	 */
+	if (num_defrag == BTRFS_DEFRAG_BATCH) {
+		defrag->last_offset = range.start;
+		btrfs_requeue_inode_defrag(inode, defrag);
+	} else if (defrag->last_offset && !defrag->cycled) {
+		/*
+		 * we didn't fill our defrag batch, but
+		 * we didn't start at zero.  Make sure we loop
+		 * around to the start of the file.
+		 */
+		defrag->last_offset = 0;
+		defrag->cycled = 1;
+		btrfs_requeue_inode_defrag(inode, defrag);
+	} else {
+		kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
+	}
+
+	iput(inode);
+	return 0;
 }
 
 /*
···
 int btrfs_run_defrag_inodes(struct btrfs_fs_info *fs_info)
 {
 	struct inode_defrag *defrag;
-	struct btrfs_root *inode_root;
-	struct inode *inode;
-	struct rb_node *n;
-	struct btrfs_key key;
-	struct btrfs_ioctl_defrag_range_args range;
 	u64 first_ino = 0;
 	u64 root_objectid = 0;
-	int num_defrag;
-	int defrag_batch = 1024;
-
-	memset(&range, 0, sizeof(range));
-	range.len = (u64)-1;
 
 	atomic_inc(&fs_info->defrag_running);
-	spin_lock(&fs_info->defrag_inodes_lock);
 	while(1) {
-		n = NULL;
+		if (!__need_auto_defrag(fs_info->tree_root))
+			break;
 
 		/* find an inode to defrag */
-		defrag = btrfs_find_defrag_inode(fs_info, root_objectid,
-						 first_ino, &n);
+		defrag = btrfs_pick_defrag_inode(fs_info, root_objectid,
+						 first_ino);
 		if (!defrag) {
-			if (n) {
-				defrag = rb_entry(n, struct inode_defrag,
-						  rb_node);
-			} else if (root_objectid || first_ino) {
+			if (root_objectid || first_ino) {
 				root_objectid = 0;
 				first_ino = 0;
 				continue;
···
 			}
 		}
 
-		/* remove it from the rbtree */
 		first_ino = defrag->ino + 1;
 		root_objectid = defrag->root;
-		rb_erase(&defrag->rb_node, &fs_info->defrag_inodes);
 
-		if (btrfs_fs_closing(fs_info))
-			goto next_free;
-
-		spin_unlock(&fs_info->defrag_inodes_lock);
-
-		/* get the inode */
-		key.objectid = defrag->root;
-		btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);
-		key.offset = (u64)-1;
-		inode_root = btrfs_read_fs_root_no_name(fs_info, &key);
-		if (IS_ERR(inode_root))
-			goto next;
-
-		key.objectid = defrag->ino;
-		btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
-		key.offset = 0;
-
-		inode = btrfs_iget(fs_info->sb, &key, inode_root, NULL);
-		if (IS_ERR(inode))
-			goto next;
-
-		/* do a chunk of defrag */
-		clear_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags);
-		range.start = defrag->last_offset;
-		num_defrag = btrfs_defrag_file(inode, NULL, &range, defrag->transid,
-					       defrag_batch);
-		/*
-		 * if we filled the whole defrag batch, there
-		 * must be more work to do.  Queue this defrag
-		 * again
-		 */
-		if (num_defrag == defrag_batch) {
-			defrag->last_offset = range.start;
-			__btrfs_add_inode_defrag(inode, defrag);
-			/*
-			 * we don't want to kfree defrag, we added it back to
-			 * the rbtree
-			 */
-			defrag = NULL;
-		} else if (defrag->last_offset && !defrag->cycled) {
-			/*
-			 * we didn't fill our defrag batch, but
-			 * we didn't start at zero.  Make sure we loop
-			 * around to the start of the file.
-			 */
-			defrag->last_offset = 0;
-			defrag->cycled = 1;
-			__btrfs_add_inode_defrag(inode, defrag);
-			defrag = NULL;
-		}
-
-		iput(inode);
-next:
-		spin_lock(&fs_info->defrag_inodes_lock);
-next_free:
-		kfree(defrag);
+		__btrfs_run_defrag_inode(fs_info, defrag);
 	}
-	spin_unlock(&fs_info->defrag_inodes_lock);
-
 	atomic_dec(&fs_info->defrag_running);
 
 	/*
···
 				split->block_len = em->block_len;
 			else
 				split->block_len = split->len;
+			split->orig_block_len = max(split->block_len,
+						    em->orig_block_len);
 			split->generation = gen;
 			split->bdev = em->bdev;
 			split->flags = flags;
···
 			split->flags = flags;
 			split->compress_type = em->compress_type;
 			split->generation = gen;
+			split->orig_block_len = max(em->block_len,
+						    em->orig_block_len);
 
 			if (compressed) {
 				split->block_len = em->block_len;
···
 			} else {
 				split->block_len = split->len;
 				split->block_start = em->block_start + diff;
-				split->orig_start = split->start;
+				split->orig_start = em->orig_start;
 			}
 
 			ret = add_extent_mapping(em_tree, split);
···
 
 		balance_dirty_pages_ratelimited(inode->i_mapping);
 		if (dirty_pages < (root->leafsize >> PAGE_CACHE_SHIFT) + 1)
-			btrfs_btree_balance_dirty(root, 1);
+			btrfs_btree_balance_dirty(root);
 
 		pos += copied;
 		num_written += copied;
···
 	return written ? written : err;
 }
 
+static void update_time_for_write(struct inode *inode)
+{
+	struct timespec now;
+
+	if (IS_NOCMTIME(inode))
+		return;
+
+	now = current_fs_time(inode->i_sb);
+	if (!timespec_equal(&inode->i_mtime, &now))
+		inode->i_mtime = now;
+
+	if (!timespec_equal(&inode->i_ctime, &now))
+		inode->i_ctime = now;
+
+	if (IS_I_VERSION(inode))
+		inode_inc_iversion(inode);
+}
+
 static ssize_t btrfs_file_aio_write(struct kiocb *iocb,
 				    const struct iovec *iov,
 				    unsigned long nr_segs, loff_t pos)
···
 	ssize_t num_written = 0;
 	ssize_t err = 0;
 	size_t count, ocount;
+	bool sync = (file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host);
 
 	sb_start_write(inode->i_sb);
 
···
 		goto out;
 	}
 
-	err = file_update_time(file);
-	if (err) {
-		mutex_unlock(&inode->i_mutex);
-		goto out;
-	}
+	/*
+	 * We reserve space for updating the inode when we reserve space for the
+	 * extent we are going to write, so we will enospc out there.  We don't
+	 * need to start yet another transaction to update the inode as we will
+	 * update the inode when we finish writing whatever data we write.
+	 */
+	update_time_for_write(inode);
 
 	start_pos = round_down(pos, root->sectorsize);
 	if (start_pos > i_size_read(inode)) {
···
 			goto out;
 		}
 	}
+
+	if (sync)
+		atomic_inc(&BTRFS_I(inode)->sync_writers);
 
 	if (unlikely(file->f_flags & O_DIRECT)) {
 		num_written = __btrfs_direct_write(iocb, iov, nr_segs,
···
 	 * this will either be one more than the running transaction
 	 * or the generation used for the next transaction if there isn't
 	 * one running right now.
+	 *
+	 * We also have to set last_sub_trans to the current log transid,
+	 * otherwise subsequent syncs to a file that's been synced in this
+	 * transaction will appear to have already occured.
 	 */
 	BTRFS_I(inode)->last_trans = root->fs_info->generation + 1;
+	BTRFS_I(inode)->last_sub_trans = root->log_transid;
 	if (num_written > 0 || num_written == -EIOCBQUEUED) {
 		err = generic_write_sync(file, pos, num_written);
 		if (err < 0 && num_written > 0)
 			num_written = err;
 	}
 out:
+	if (sync)
+		atomic_dec(&BTRFS_I(inode)->sync_writers);
 	sb_end_write(inode->i_sb);
 	current->backing_dev_info = NULL;
 	return num_written ? num_written : err;
···
 	 * out of the ->i_mutex. If so, we can flush the dirty pages by
 	 * multi-task, and make the performance up.
 	 */
+	atomic_inc(&BTRFS_I(inode)->sync_writers);
 	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	atomic_dec(&BTRFS_I(inode)->sync_writers);
 	if (ret)
 		return ret;
 
···
 	 * range being left.
 	 */
 	atomic_inc(&root->log_batch);
-	btrfs_wait_ordered_range(inode, start, end);
+	btrfs_wait_ordered_range(inode, start, end - start + 1);
 	atomic_inc(&root->log_batch);
 
 	/*
···
 
 		hole_em->block_start = EXTENT_MAP_HOLE;
 		hole_em->block_len = 0;
+		hole_em->orig_block_len = 0;
 		hole_em->bdev = root->fs_info->fs_devices->latest_bdev;
 		hole_em->compress_type = BTRFS_COMPRESS_NONE;
 		hole_em->generation = trans->transid;
···
 	struct btrfs_path *path;
 	struct btrfs_block_rsv *rsv;
 	struct btrfs_trans_handle *trans;
-	u64 mask = BTRFS_I(inode)->root->sectorsize - 1;
-	u64 lockstart = (offset + mask) & ~mask;
-	u64 lockend = ((offset + len) & ~mask) - 1;
+	u64 lockstart = round_up(offset, BTRFS_I(inode)->root->sectorsize);
+	u64 lockend = round_down(offset + len,
+				 BTRFS_I(inode)->root->sectorsize) - 1;
 	u64 cur_offset = lockstart;
 	u64 min_size = btrfs_calc_trunc_metadata_size(root, 1);
 	u64 drop_end;
-	unsigned long nr;
 	int ret = 0;
 	int err = 0;
-	bool same_page = (offset >> PAGE_CACHE_SHIFT) ==
-		((offset + len) >> PAGE_CACHE_SHIFT);
+	bool same_page = ((offset >> PAGE_CACHE_SHIFT) ==
+			  ((offset + len - 1) >> PAGE_CACHE_SHIFT));
 
 	btrfs_wait_ordered_range(inode, offset, len);
 
 	mutex_lock(&inode->i_mutex);
-	if (offset >= inode->i_size) {
-		mutex_unlock(&inode->i_mutex);
-		return 0;
-	}
-
+	/*
+	 * We needn't truncate any page which is beyond the end of the file
+	 * because we are sure there is no data there.
+	 */
 	/*
 	 * Only do this if we are in the same page and we aren't doing the
 	 * entire page.
 	 */
 	if (same_page && len < PAGE_CACHE_SIZE) {
-		ret = btrfs_truncate_page(inode, offset, len, 0);
+		if (offset < round_up(inode->i_size, PAGE_CACHE_SIZE))
+			ret = btrfs_truncate_page(inode, offset, len, 0);
 		mutex_unlock(&inode->i_mutex);
 		return ret;
 	}
 
 	/* zero back part of the first page */
-	ret = btrfs_truncate_page(inode, offset, 0, 0);
-	if (ret) {
-		mutex_unlock(&inode->i_mutex);
-		return ret;
+	if (offset < round_up(inode->i_size, PAGE_CACHE_SIZE)) {
+		ret = btrfs_truncate_page(inode, offset, 0, 0);
+		if (ret) {
+			mutex_unlock(&inode->i_mutex);
+			return ret;
+		}
 	}
 
 	/* zero the front end of the last page */
-	ret = btrfs_truncate_page(inode, offset + len, 0, 1);
-	if (ret) {
-		mutex_unlock(&inode->i_mutex);
-		return ret;
+	if (offset + len < round_up(inode->i_size, PAGE_CACHE_SIZE)) {
+		ret = btrfs_truncate_page(inode, offset + len, 0, 1);
+		if (ret) {
+			mutex_unlock(&inode->i_mutex);
+			return ret;
+		}
 	}
 
 	if (lockend < lockstart) {
···
 			break;
 		}
 
-		nr = trans->blocks_used;
 		btrfs_end_transaction(trans, root);
-		btrfs_btree_balance_dirty(root, nr);
+		btrfs_btree_balance_dirty(root);
 
 		trans = btrfs_start_transaction(root, 3);
 		if (IS_ERR(trans)) {
···
 	if (!trans)
 		goto out_free;
 
+	inode_inc_iversion(inode);
+	inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+
 	trans->block_rsv = &root->fs_info->trans_block_rsv;
 	ret = btrfs_update_inode(trans, root, inode);
-	nr = trans->blocks_used;
 	btrfs_end_transaction(trans, root);
-	btrfs_btree_balance_dirty(root, nr);
+	btrfs_btree_balance_dirty(root);
 out_free:
 	btrfs_free_path(path);
 	btrfs_free_block_rsv(root, rsv);
···
 	u64 alloc_end;
 	u64 alloc_hint = 0;
 	u64 locked_end;
-	u64 mask = BTRFS_I(inode)->root->sectorsize - 1;
 	struct extent_map *em;
+	int blocksize = BTRFS_I(inode)->root->sectorsize;
 	int ret;
 
-	alloc_start = offset & ~mask;
-	alloc_end =  (offset + len + mask) & ~mask;
+	alloc_start = round_down(offset, blocksize);
+	alloc_end = round_up(offset + len, blocksize);
 
 	/* Make sure we aren't being give some crap mode */
 	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
···
 	 * Make sure we have enough space before we do the
 	 * allocation.
 	 */
-	ret = btrfs_check_data_free_space(inode, alloc_end - alloc_start + 1);
+	ret = btrfs_check_data_free_space(inode, alloc_end - alloc_start);
 	if (ret)
 		return ret;
 
···
 		}
 		last_byte = min(extent_map_end(em), alloc_end);
 		actual_end = min_t(u64, extent_map_end(em), offset + len);
-		last_byte = (last_byte + mask) & ~mask;
+		last_byte = ALIGN(last_byte, blocksize);
 
 		if (em->block_start == EXTENT_MAP_HOLE ||
 		    (cur_offset >= inode->i_size &&
···
 out:
 	mutex_unlock(&inode->i_mutex);
 	/* Let go of our reservation. */
-	btrfs_free_reserved_data_space(inode, alloc_end - alloc_start + 1);
+	btrfs_free_reserved_data_space(inode, alloc_end - alloc_start);
 	return ret;
 }
 
···
 	.compat_ioctl	= btrfs_ioctl,
 #endif
 };
+
+void btrfs_auto_defrag_exit(void)
+{
+	if (btrfs_inode_defrag_cachep)
+		kmem_cache_destroy(btrfs_inode_defrag_cachep);
+}
+
+int btrfs_auto_defrag_init(void)
+{
+	btrfs_inode_defrag_cachep = kmem_cache_create("btrfs_inode_defrag",
+					sizeof(struct inode_defrag), 0,
+					SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
+					NULL);
+	if (!btrfs_inode_defrag_cachep)
+		return -ENOMEM;
+
+	return 0;
+}

fs/btrfs/free-space-cache.c

···
 
 static void io_ctl_map_page(struct io_ctl *io_ctl, int clear)
 {
-	WARN_ON(io_ctl->cur);
 	BUG_ON(io_ctl->index >= io_ctl->num_pages);
 	io_ctl->page = io_ctl->pages[io_ctl->index++];
 	io_ctl->cur = kmap(io_ctl->page);
···
 			 * if previous extent entry covers the offset,
 			 * we should return it instead of the bitmap entry
 			 */
-			n = &entry->offset_index;
-			while (1) {
-				n = rb_prev(n);
-				if (!n)
-					break;
+			n = rb_prev(&entry->offset_index);
+			if (n) {
 				prev = rb_entry(n, struct btrfs_free_space,
 						offset_index);
-				if (!prev->bitmap) {
-					if (prev->offset + prev->bytes > offset)
-						entry = prev;
-					break;
-				}
+				if (!prev->bitmap &&
+				    prev->offset + prev->bytes > offset)
+					entry = prev;
 			}
 		}
 		return entry;
···
 	}
 
 	if (entry->bitmap) {
-		n = &entry->offset_index;
-		while (1) {
-			n = rb_prev(n);
-			if (!n)
-				break;
+		n = rb_prev(&entry->offset_index);
+		if (n) {
 			prev = rb_entry(n, struct btrfs_free_space,
 					offset_index);
-			if (!prev->bitmap) {
-				if (prev->offset + prev->bytes > offset)
-					return prev;
-				break;
-			}
+			if (!prev->bitmap &&
+			    prev->offset + prev->bytes > offset)
+				return prev;
 		}
 		if (entry->offset + BITS_PER_BITMAP * ctl->unit > offset)
 			return entry;
···
 	u64 bitmap_bytes;
 	u64 extent_bytes;
 	u64 size = block_group->key.offset;
-	u64 bytes_per_bg = BITS_PER_BITMAP * block_group->sectorsize;
+	u64 bytes_per_bg = BITS_PER_BITMAP * ctl->unit;
 	int max_bitmaps = div64_u64(size + bytes_per_bg - 1, bytes_per_bg);
 
 	BUG_ON(ctl->total_bitmaps > max_bitmaps);
···
 	 * some block groups are so tiny they can't be enveloped by a bitmap, so
 	 * don't even bother to create a bitmap for this
 	 */
-	if (BITS_PER_BITMAP * block_group->sectorsize >
-	    block_group->key.offset)
+	if (BITS_PER_BITMAP * ctl->unit > block_group->key.offset)
 		return false;
 
 	return true;
···
 	unsigned long total_found = 0;
 	int ret;
 
-	i = offset_to_bit(entry->offset, block_group->sectorsize,
+	i = offset_to_bit(entry->offset, ctl->unit,
 			  max_t(u64, offset, entry->offset));
-	want_bits = bytes_to_bits(bytes, block_group->sectorsize);
-	min_bits = bytes_to_bits(min_bytes, block_group->sectorsize);
+	want_bits = bytes_to_bits(bytes, ctl->unit);
+	min_bits = bytes_to_bits(min_bytes, ctl->unit);
 
 again:
 	found_bits = 0;
···
 
 	total_found += found_bits;
 
-	if (cluster->max_size < found_bits * block_group->sectorsize)
-		cluster->max_size = found_bits * block_group->sectorsize;
+	if (cluster->max_size < found_bits * ctl->unit)
+		cluster->max_size = found_bits * ctl->unit;
 
 	if (total_found < want_bits || cluster->max_size < cont1_bytes) {
 		i = next_zero + 1;
 		goto again;
 	}
 
-	cluster->window_start = start * block_group->sectorsize +
-		entry->offset;
+	cluster->window_start = start * ctl->unit + entry->offset;
 	rb_erase(&entry->offset_index, &ctl->free_space_offset);
 	ret = tree_insert_offset(&cluster->root, entry->offset,
 				 &entry->offset_index, 1);
 	BUG_ON(ret); /* -EEXIST; Logic error */
 
 	trace_btrfs_setup_cluster(block_group, cluster,
-				  total_found * block_group->sectorsize, 1);
+				  total_found * ctl->unit, 1);
 	return 0;
 }
 

fs/btrfs/inode-map.c

···
 	 * 3 items for pre-allocation
 	 */
 	trans->bytes_reserved = btrfs_calc_trans_metadata_size(root, 8);
-	ret = btrfs_block_rsv_add_noflush(root, trans->block_rsv,
-					  trans->bytes_reserved);
+	ret = btrfs_block_rsv_add(root, trans->block_rsv,
+				  trans->bytes_reserved,
+				  BTRFS_RESERVE_NO_FLUSH);
 	if (ret)
 		goto out;
 	trace_btrfs_space_reservation(root->fs_info, "ino_cache",

fs/btrfs/inode.c

···
 static struct extent_io_ops btrfs_extent_io_ops;
 
 static struct kmem_cache *btrfs_inode_cachep;
+static struct kmem_cache *btrfs_delalloc_work_cachep;
 struct kmem_cache *btrfs_trans_handle_cachep;
 struct kmem_cache *btrfs_transaction_cachep;
 struct kmem_cache *btrfs_path_cachep;
···
 				   struct page *locked_page,
 				   u64 start, u64 end, int *page_started,
 				   unsigned long *nr_written, int unlock);
+static struct extent_map *create_pinned_em(struct inode *inode, u64 start,
+					   u64 len, u64 orig_start,
+					   u64 block_start, u64 block_len,
+					   u64 orig_block_len, int type);
 
 static int btrfs_init_inode_security(struct btrfs_trans_handle *trans,
 				     struct inode *inode,  struct inode *dir,
···
 
 		em->block_start = ins.objectid;
 		em->block_len = ins.offset;
+		em->orig_block_len = ins.offset;
 		em->bdev = root->fs_info->fs_devices->latest_bdev;
 		em->compress_type = async_extent->compress_type;
 		set_bit(EXTENT_FLAG_PINNED, &em->flags);
 		set_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
+		em->generation = -1;
 
 		while (1) {
 			write_lock(&em_tree->lock);
 			ret = add_extent_mapping(em_tree, em);
+			if (!ret)
+				list_move(&em->list,
+					  &em_tree->modified_extents);
 			write_unlock(&em_tree->lock);
 			if (ret != -EEXIST) {
 				free_extent_map(em);
···
  * required to start IO on it.  It may be clean and already done with
  * IO when we return.
  */
-static noinline int cow_file_range(struct inode *inode,
-				   struct page *locked_page,
-				   u64 start, u64 end, int *page_started,
-				   unsigned long *nr_written,
-				   int unlock)
+static noinline int __cow_file_range(struct btrfs_trans_handle *trans,
+				     struct inode *inode,
+				     struct btrfs_root *root,
+				     struct page *locked_page,
+				     u64 start, u64 end, int *page_started,
+				     unsigned long *nr_written,
+				     int unlock)
 {
-	struct btrfs_root *root = BTRFS_I(inode)->root;
-	struct btrfs_trans_handle *trans;
 	u64 alloc_hint = 0;
 	u64 num_bytes;
 	unsigned long ram_size;
···
 	int ret = 0;
 
 	BUG_ON(btrfs_is_free_space_inode(inode));
-	trans = btrfs_join_transaction(root);
-	if (IS_ERR(trans)) {
-		extent_clear_unlock_delalloc(inode,
-			     &BTRFS_I(inode)->io_tree,
-			     start, end, locked_page,
-			     EXTENT_CLEAR_UNLOCK_PAGE |
-			     EXTENT_CLEAR_UNLOCK |
-			     EXTENT_CLEAR_DELALLOC |
-			     EXTENT_CLEAR_DIRTY |
-			     EXTENT_SET_WRITEBACK |
-			     EXTENT_END_WRITEBACK);
-		return PTR_ERR(trans);
-	}
-	trans->block_rsv = &root->fs_info->delalloc_block_rsv;
 
 	num_bytes = (end - start + blocksize) & ~(blocksize - 1);
 	num_bytes = max(blocksize,  num_bytes);
 	disk_num_bytes = num_bytes;
-	ret = 0;
 
 	/* if this is a small write inside eof, kick off defrag */
 	if (num_bytes < 64 * 1024 &&
···
 
 		em->block_start = ins.objectid;
 		em->block_len = ins.offset;
+		em->orig_block_len = ins.offset;
 		em->bdev = root->fs_info->fs_devices->latest_bdev;
 		set_bit(EXTENT_FLAG_PINNED, &em->flags);
+		em->generation = -1;
 
 		while (1) {
 			write_lock(&em_tree->lock);
 			ret = add_extent_mapping(em_tree, em);
+			if (!ret)
+				list_move(&em->list,
+					  &em_tree->modified_extents);
 			write_unlock(&em_tree->lock);
 			if (ret != -EEXIST) {
 				free_extent_map(em);
···
 		alloc_hint = ins.objectid + ins.offset;
 		start += cur_alloc_size;
 	}
-	ret = 0;
 out:
-	btrfs_end_transaction(trans, root);
-
 	return ret;
+
 out_unlock:
 	extent_clear_unlock_delalloc(inode,
 		     &BTRFS_I(inode)->io_tree,
···
 		     EXTENT_END_WRITEBACK);
 
 	goto out;
+}
+
+static noinline int cow_file_range(struct inode *inode,
+				   struct page *locked_page,
+				   u64 start, u64 end, int *page_started,
+				   unsigned long *nr_written,
+				   int unlock)
+{
+	struct btrfs_trans_handle *trans;
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	int ret;
+
+	trans = btrfs_join_transaction(root);
+	if (IS_ERR(trans)) {
+		extent_clear_unlock_delalloc(inode,
+			     &BTRFS_I(inode)->io_tree,
+			     start, end, locked_page,
+			     EXTENT_CLEAR_UNLOCK_PAGE |
+			     EXTENT_CLEAR_UNLOCK |
+			     EXTENT_CLEAR_DELALLOC |
+			     EXTENT_CLEAR_DIRTY |
+			     EXTENT_SET_WRITEBACK |
+			     EXTENT_END_WRITEBACK);
+		return PTR_ERR(trans);
+	}
+	trans->block_rsv = &root->fs_info->delalloc_block_rsv;
+
+	ret = __cow_file_range(trans, inode, root, locked_page, start, end,
+			       page_started, nr_written, unlock);
+
+	btrfs_end_transaction(trans, root);
+
+	return ret;
 }
 
 /*
···
 	u64 extent_offset;
 	u64 disk_bytenr;
 	u64 num_bytes;
+	u64 disk_num_bytes;
 	int extent_type;
 	int ret, err;
 	int type;
···
 			extent_offset = btrfs_file_extent_offset(leaf, fi);
 			extent_end = found_key.offset +
 				btrfs_file_extent_num_bytes(leaf, fi);
+			disk_num_bytes =
+				btrfs_file_extent_disk_num_bytes(leaf, fi);
 			if (extent_end <= start) {
 				path->slots[0]++;
 				goto next_slot;
···
 
 		btrfs_release_path(path);
 		if (cow_start != (u64)-1) {
-			ret = cow_file_range(inode, locked_page, cow_start,
-					found_key.offset - 1, page_started,
-					nr_written, 1);
+			ret = __cow_file_range(trans, inode, root, locked_page,
+					       cow_start, found_key.offset - 1,
+					       page_started, nr_written, 1);
 			if (ret) {
 				btrfs_abort_transaction(trans, root, ret);
 				goto error;
···
 			em = alloc_extent_map();
 			BUG_ON(!em); /* -ENOMEM */
 			em->start = cur_offset;
-			em->orig_start = em->start;
+			em->orig_start = found_key.offset - extent_offset;
 			em->len = num_bytes;
 			em->block_len = num_bytes;
 			em->block_start = disk_bytenr;
+			em->orig_block_len = disk_num_bytes;
 			em->bdev = root->fs_info->fs_devices->latest_bdev;
 			set_bit(EXTENT_FLAG_PINNED, &em->flags);
-			set_bit(EXTENT_FLAG_PREALLOC, &em->flags);
+			set_bit(EXTENT_FLAG_FILLING, &em->flags);
+			em->generation = -1;
 			while (1) {
 				write_lock(&em_tree->lock);
 				ret = add_extent_mapping(em_tree, em);
+				if (!ret)
+					list_move(&em->list,
+						  &em_tree->modified_extents);
 				write_unlock(&em_tree->lock);
 				if (ret != -EEXIST) {
 					free_extent_map(em);
···
 	}
 
 	if (cow_start != (u64)-1) {
-		ret = cow_file_range(inode, locked_page, cow_start, end,
-				     page_started, nr_written, 1);
+		ret = __cow_file_range(trans, inode, root, locked_page,
+				       cow_start, end,
+				       page_started, nr_written, 1);
 		if (ret) {
 			btrfs_abort_transaction(trans, root, ret);
 			goto error;
···
 			 unsigned long bio_flags)
 {
 	struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
-	struct btrfs_mapping_tree *map_tree;
 	u64 logical = (u64)bio->bi_sector << 9;
 	u64 length = 0;
 	u64 map_length;
···
 		return 0;
 
 	length = bio->bi_size;
-	map_tree = &root->fs_info->mapping_tree;
 	map_length = length;
-	ret = btrfs_map_block(map_tree, READ, logical,
+	ret = btrfs_map_block(root->fs_info, READ, logical,
 			      &map_length, NULL, 0);
-	/* Will always return 0 or 1 with map_multi == NULL */
+	/* Will always return 0 with map_multi == NULL */
 	BUG_ON(ret < 0);
 	if (map_length < length + size)
 		return 1;
···
 			  u64 bio_offset)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
-	return btrfs_map_bio(root, rw, bio, mirror_num, 1);
+	int ret;
+
+	ret = btrfs_map_bio(root, rw, bio, mirror_num, 1);
+	if (ret)
+		bio_endio(bio, ret);
+	return ret;
 }
 
 /*
···
 	int ret = 0;
 	int skip_sum;
 	int metadata = 0;
+	int async = !atomic_read(&BTRFS_I(inode)->sync_writers);
 
 	skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
 
···
 	if (!(rw & REQ_WRITE)) {
 		ret = btrfs_bio_wq_end_io(root->fs_info, bio, metadata);
 		if (ret)
-			return ret;
+			goto out;
 
 		if (bio_flags & EXTENT_BIO_COMPRESSED) {
-			return btrfs_submit_compressed_read(inode, bio,
-						    mirror_num, bio_flags);
+			ret = btrfs_submit_compressed_read(inode, bio,
+							   mirror_num,
+							   bio_flags);
+			goto out;
 		} else if (!skip_sum) {
 			ret = btrfs_lookup_bio_sums(root, inode, bio, NULL);
 			if (ret)
-				return ret;
+				goto out;
 		}
 		goto mapit;
-	} else if (!skip_sum) {
+	} else if (async && !skip_sum) {
 		/* csum items have already been cloned */
 		if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID)
 			goto mapit;
 		/* we're doing a write, do the async checksumming */
-		return btrfs_wq_submit_bio(BTRFS_I(inode)->root->fs_info,
+		ret = btrfs_wq_submit_bio(BTRFS_I(inode)->root->fs_info,
 				   inode, rw, bio, mirror_num,
 				   bio_flags, bio_offset,
 				   __btrfs_submit_bio_start,
 				   __btrfs_submit_bio_done);
+		goto out;
+	} else if (!skip_sum) {
+		ret = btrfs_csum_one_bio(root, inode, bio, 0, 0);
+		if (ret)
+			goto out;
 	}
 
 mapit:
-	return btrfs_map_bio(root, rw, bio, mirror_num, 0);
+	ret = btrfs_map_bio(root, rw, bio, mirror_num, 0);
+
+out:
+	if (ret < 0)
+		bio_endio(bio, ret);
+	return ret;
 }
 
 /*
···
 int btrfs_set_extent_delalloc(struct inode *inode, u64 start, u64 end,
 			      struct extent_state **cached_state)
 {
-	if ((end & (PAGE_CACHE_SIZE - 1)) == 0)
-		WARN_ON(1);
+	WARN_ON((end & (PAGE_CACHE_SIZE - 1)) == 0);
 	return set_extent_delalloc(&BTRFS_I(inode)->io_tree, start, end,
 				   cached_state, GFP_NOFS);
 }
···
 
 	if (test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags)) {
 		BUG_ON(!list_empty(&ordered_extent->list)); /* Logic error */
-		ret = btrfs_ordered_update_i_size(inode, 0, ordered_extent);
-		if (!ret) {
-			if (nolock)
-				trans = btrfs_join_transaction_nolock(root);
-			else
-				trans = btrfs_join_transaction(root);
-			if (IS_ERR(trans)) {
-				ret = PTR_ERR(trans);
-				trans = NULL;
-				goto out;
-			}
-			trans->block_rsv = &root->fs_info->delalloc_block_rsv;
-			ret = btrfs_update_inode_fallback(trans, root, inode);
-			if (ret) /* -ENOMEM or corruption */
-				btrfs_abort_transaction(trans, root, ret);
+		btrfs_ordered_update_i_size(inode, 0, ordered_extent);
+		if (nolock)
+			trans = btrfs_join_transaction_nolock(root);
+		else
+			trans = btrfs_join_transaction(root);
+		if (IS_ERR(trans)) {
+			ret = PTR_ERR(trans);
+			trans = NULL;
+			goto out;
 		}
+		trans->block_rsv = &root->fs_info->delalloc_block_rsv;
+		ret = btrfs_update_inode_fallback(trans, root, inode);
+		if (ret) /* -ENOMEM or corruption */
+			btrfs_abort_transaction(trans, root, ret);
 		goto out;
 	}
 
···
 	add_pending_csums(trans, inode, ordered_extent->file_offset,
 			  &ordered_extent->list);
 
-	ret = btrfs_ordered_update_i_size(inode, 0, ordered_extent);
-	if (!ret || !test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags)) {
-		ret = btrfs_update_inode_fallback(trans, root, inode);
-		if (ret) { /* -ENOMEM or corruption */
-			btrfs_abort_transaction(trans, root, ret);
-			goto out_unlock;
-		}
-	} else {
-		btrfs_set_inode_last_trans(trans, inode);
+	btrfs_ordered_update_i_size(inode, 0, ordered_extent);
+	ret = btrfs_update_inode_fallback(trans, root, inode);
+	if (ret) { /* -ENOMEM or corruption */
+		btrfs_abort_transaction(trans, root, ret);
+		goto out_unlock;
 	}
 	ret = 0;
 out_unlock:
···
 	struct btrfs_trans_handle *trans;
 	struct inode *inode = dentry->d_inode;
 	int ret;
-	unsigned long nr = 0;
 
 	trans = __unlink_start_trans(dir, dentry);
 	if (IS_ERR(trans))
···
 	}
 
 out:
-	nr = trans->blocks_used;
 	__unlink_end_trans(trans, root);
-	btrfs_btree_balance_dirty(root, nr);
+	btrfs_btree_balance_dirty(root);
 	return ret;
 }
 
···
 	int err = 0;
 	struct btrfs_root *root = BTRFS_I(dir)->root;
 	struct btrfs_trans_handle *trans;
-	unsigned long nr = 0;
 
 	if (inode->i_size > BTRFS_EMPTY_DIR_SIZE)
 		return -ENOTEMPTY;
···
 	if (!err)
 		btrfs_i_size_write(inode, 0);
 out:
-	nr = trans->blocks_used;
 	__unlink_end_trans(trans, root);
-	btrfs_btree_balance_dirty(root, nr);
+	btrfs_btree_balance_dirty(root);
 
 	return err;
 }
···
 	if (ret)
 		goto out;
 
-	ret = -ENOMEM;
 again:
 	page = find_or_create_page(mapping, index, mask);
 	if (!page) {
 		btrfs_delalloc_release_space(inode, PAGE_CACHE_SIZE);
+		ret = -ENOMEM;
 		goto out;
 	}
 
···
 		goto out_unlock;
 	}
 
-	ret = 0;
 	if (offset != PAGE_CACHE_SIZE) {
 		if (!len)
 			len = PAGE_CACHE_SIZE - offset;
···
 
 			hole_em->block_start = EXTENT_MAP_HOLE;
 			hole_em->block_len = 0;
+			hole_em->orig_block_len = 0;
 			hole_em->bdev = root->fs_info->fs_devices->latest_bdev;
 			hole_em->compress_type = BTRFS_COMPRESS_NONE;
 			hole_em->generation = trans->transid;
···
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct btrfs_block_rsv *rsv, *global_rsv;
 	u64 min_size = btrfs_calc_trunc_metadata_size(root, 1);
-	unsigned long nr;
 	int ret;
 
 	trace_btrfs_inode_evict(inode);
···
 	 * inode item when doing the truncate.
 	 */
 	while (1) {
-		ret = btrfs_block_rsv_refill_noflush(root, rsv, min_size);
+		ret = btrfs_block_rsv_refill(root, rsv, min_size,
+					     BTRFS_RESERVE_FLUSH_LIMIT);
 
 		/*
 		 * Try and steal from the global reserve since we will
···
 			goto no_delete;
 		}
 
-		trans = btrfs_start_transaction_noflush(root, 1);
+		trans = btrfs_start_transaction_lflush(root, 1);
 		if (IS_ERR(trans)) {
 			btrfs_orphan_del(NULL, inode);
 			btrfs_free_block_rsv(root, rsv);
···
 		ret = btrfs_update_inode(trans, root, inode);
 		BUG_ON(ret);
 
-		nr = trans->blocks_used;
 		btrfs_end_transaction(trans, root);
 		trans = NULL;
-		btrfs_btree_balance_dirty(root, nr);
+		btrfs_btree_balance_dirty(root);
 	}
 
 	btrfs_free_block_rsv(root, rsv);
···
 	      root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID))
 		btrfs_return_ino(root, btrfs_ino(inode));
 
-	nr = trans->blocks_used;
 	btrfs_end_transaction(trans, root);
-	btrfs_btree_balance_dirty(root, nr);
+	btrfs_btree_balance_dirty(root);
 no_delete:
 	clear_inode(inode);
 	return;
···
 	if (S_ISREG(mode)) {
 		if (btrfs_test_opt(root, NODATASUM))
 			BTRFS_I(inode)->flags |= BTRFS_INODE_NODATASUM;
-		if (btrfs_test_opt(root, NODATACOW) ||
-		    (BTRFS_I(dir)->flags & BTRFS_INODE_NODATACOW))
+		if (btrfs_test_opt(root, NODATACOW))
 			BTRFS_I(inode)->flags |= BTRFS_INODE_NODATACOW;
 	}
 
···
 	ret = btrfs_insert_dir_item(trans, root, name, name_len,
 				    parent_inode, &key,
 				    btrfs_inode_type(inode), index);
-	if (ret == -EEXIST)
+	if (ret == -EEXIST || ret == -EOVERFLOW)
 		goto fail_dir_item;
 	else if (ret) {
 		btrfs_abort_transaction(trans, root, ret);
···
 	int err;
 	int drop_inode = 0;
 	u64 objectid;
-	unsigned long nr = 0;
 	u64 index = 0;
 
 	if (!new_valid_dev(rdev))
···
 		goto out_unlock;
 	}
 
+	err = btrfs_update_inode(trans, root, inode);
+	if (err) {
+		drop_inode = 1;
+		goto out_unlock;
+	}
+
 	/*
 	* If the active LSM wants to access the inode during
 	* d_instantiate it needs these. Smack checks to see
···
 		d_instantiate(dentry, inode);
 	}
 out_unlock:
-	nr = trans->blocks_used;
 	btrfs_end_transaction(trans, root);
-	btrfs_btree_balance_dirty(root, nr);
+	btrfs_btree_balance_dirty(root);
 	if (drop_inode) {
 		inode_dec_link_count(inode);
 		iput(inode);
···
 	struct btrfs_trans_handle *trans;
 	struct btrfs_root *root = BTRFS_I(dir)->root;
 	struct inode *inode = NULL;
-	int drop_inode = 0;
+	int drop_inode_on_err = 0;
 	int err;
-	unsigned long nr = 0;
 	u64 objectid;
 	u64 index = 0;
 
···
 		err = PTR_ERR(inode);
 		goto out_unlock;
 	}
+	drop_inode_on_err = 1;
 
 	err = btrfs_init_inode_security(trans, inode, dir, &dentry->d_name);
-	if (err) {
-		drop_inode = 1;
+	if (err)
 		goto out_unlock;
-	}
+
+	err = btrfs_update_inode(trans, root, inode);
+	if (err)
+		goto out_unlock;
 
 	/*
 	* If the active LSM wants to access the inode during
···
 
 	err = btrfs_add_nondir(trans, dir, dentry, inode, 0, index);
 	if (err)
-		drop_inode = 1;
-	else {
-		inode->i_mapping->a_ops = &btrfs_aops;
-		inode->i_mapping->backing_dev_info = &root->fs_info->bdi;
-		BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
-		d_instantiate(dentry, inode);
-	}
+		goto out_unlock;
+
+	inode->i_mapping->a_ops = &btrfs_aops;
+	inode->i_mapping->backing_dev_info = &root->fs_info->bdi;
+	BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
+	d_instantiate(dentry, inode);
+
 out_unlock:
-	nr = trans->blocks_used;
 	btrfs_end_transaction(trans, root);
-	if (drop_inode) {
+	if (err && drop_inode_on_err) {
 		inode_dec_link_count(inode);
 		iput(inode);
 	}
-	btrfs_btree_balance_dirty(root, nr);
+	btrfs_btree_balance_dirty(root);
 	return err;
 }
 
···
 	struct btrfs_root *root = BTRFS_I(dir)->root;
 	struct inode *inode = old_dentry->d_inode;
 	u64 index;
-	unsigned long nr = 0;
 	int err;
 	int drop_inode = 0;
 
···
 	inode_inc_iversion(inode);
 	inode->i_ctime = CURRENT_TIME;
 	ihold(inode);
+	set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
 
 	err = btrfs_add_nondir(trans, dir, dentry, inode, 1, index);
 
···
 		btrfs_log_new_name(trans, inode, NULL, parent);
 	}
 
-	nr = trans->blocks_used;
 	btrfs_end_transaction(trans, root);
 fail:
 	if (drop_inode) {
 		inode_dec_link_count(inode);
 		iput(inode);
 	}
-	btrfs_btree_balance_dirty(root, nr);
+	btrfs_btree_balance_dirty(root);
 	return err;
 }
 
···
 	int drop_on_err = 0;
 	u64 objectid = 0;
 	u64 index = 0;
-	unsigned long nr = 1;
 
 	/*
 	 * 2 items for inode and ref
···
 	drop_on_err = 0;
 
 out_fail:
-	nr = trans->blocks_used;
 	btrfs_end_transaction(trans, root);
 	if (drop_on_err)
 		iput(inode);
-	btrfs_btree_balance_dirty(root, nr);
+	btrfs_btree_balance_dirty(root);
 	return err;
 }
 
···
 		if (start + len <= found_key.offset)
 			goto not_found;
 		em->start = start;
+		em->orig_start = start;
 		em->len = found_key.offset - start;
 		goto not_found_em;
 	}
···
 		em->len = extent_end - extent_start;
 		em->orig_start = extent_start -
 				 btrfs_file_extent_offset(leaf, item);
+		em->orig_block_len = btrfs_file_extent_disk_num_bytes(leaf,
+								      item);
 		bytenr = btrfs_file_extent_disk_bytenr(leaf, item);
 		if (bytenr == 0) {
 			em->block_start = EXTENT_MAP_HOLE;
···
 			set_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
 			em->compress_type = compress_type;
 			em->block_start = bytenr;
-			em->block_len = btrfs_file_extent_disk_num_bytes(leaf,
-									 item);
+			em->block_len = em->orig_block_len;
 		} else {
 			bytenr += btrfs_file_extent_offset(leaf, item);
 			em->block_start = bytenr;
···
 		em->start = extent_start + extent_offset;
 		em->len = (copy_size + root->sectorsize - 1) &
 			~((u64)root->sectorsize - 1);
-		em->orig_start = EXTENT_MAP_INLINE;
+		em->orig_block_len = em->len;
+		em->orig_start = em->start;
 		if (compress_type) {
 			set_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
 			em->compress_type = compress_type;
···
 				    extent_map_end(em) - 1, NULL, GFP_NOFS);
 		goto insert;
 	} else {
-		printk(KERN_ERR "btrfs unknown found_type %d\n", found_type);
-		WARN_ON(1);
+		WARN(1, KERN_ERR "btrfs unknown found_type %d\n", found_type);
 	}
 not_found:
 	em->start = start;
+	em->orig_start = start;
 	em->len = len;
 not_found_em:
 	em->block_start = EXTENT_MAP_HOLE;
···
 }
 
 static struct extent_map *btrfs_new_extent_direct(struct inode *inode,
-						  struct extent_map *em,
 						  u64 start, u64 len)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct btrfs_trans_handle *trans;
-	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
+	struct extent_map *em;
 	struct btrfs_key ins;
 	u64 alloc_hint;
 	int ret;
-	bool insert = false;
-
-	/*
-	 * Ok if the extent map we looked up is a hole and is for the exact
-	 * range we want, there is no reason to allocate a new one, however if
-	 * it is not right then we need to free this one and drop the cache for
-	 * our range.
-	 */
-	if (em->block_start != EXTENT_MAP_HOLE || em->start != start ||
-	    em->len != len) {
-		free_extent_map(em);
-		em = NULL;
-		insert = true;
-		btrfs_drop_extent_cache(inode, start, start + len - 1, 0);
-	}
 
 	trans = btrfs_join_transaction(root);
 	if (IS_ERR(trans))
 		return ERR_CAST(trans);
-
-	if (start <= BTRFS_I(inode)->disk_i_size && len < 64 * 1024)
-		btrfs_add_inode_defrag(trans, inode);
 
 	trans->block_rsv = &root->fs_info->delalloc_block_rsv;
 
···
 		goto out;
 	}
 
-	if (!em) {
-		em = alloc_extent_map();
-		if (!em) {
-			em = ERR_PTR(-ENOMEM);
-			goto out;
-		}
-	}
-
-	em->start = start;
-	em->orig_start = em->start;
-	em->len = ins.offset;
-
-	em->block_start = ins.objectid;
-	em->block_len = ins.offset;
-	em->bdev = root->fs_info->fs_devices->latest_bdev;
-
-	/*
-	 * We need to do this because if we're using the original em we searched
-	 * for, we could have EXTENT_FLAG_VACANCY set, and we don't want that.
-	 */
-	em->flags = 0;
-	set_bit(EXTENT_FLAG_PINNED, &em->flags);
-
-	while (insert) {
-		write_lock(&em_tree->lock);
-		ret = add_extent_mapping(em_tree, em);
-		write_unlock(&em_tree->lock);
-		if (ret != -EEXIST)
-			break;
-		btrfs_drop_extent_cache(inode, start, start + em->len - 1, 0);
-	}
+	em = create_pinned_em(inode, start, ins.offset, start, ins.objectid,
+			      ins.offset, ins.offset, 0);
+	if (IS_ERR(em))
+		goto out;
 
 	ret = btrfs_add_ordered_extent_dio(inode, start, ins.objectid,
 					   ins.offset, ins.offset, 0);
···
 static struct extent_map *create_pinned_em(struct inode *inode, u64 start,
 					   u64 len, u64 orig_start,
 					   u64 block_start, u64 block_len,
-					   int type)
+					   u64 orig_block_len, int type)
 {
 	struct extent_map_tree *em_tree;
 	struct extent_map *em;
···
 	em->block_len = block_len;
 	em->block_start = block_start;
 	em->bdev = root->fs_info->fs_devices->latest_bdev;
+	em->orig_block_len = orig_block_len;
+	em->generation = -1;
 	set_bit(EXTENT_FLAG_PINNED, &em->flags);
 	if (type == BTRFS_ORDERED_PREALLOC)
-		set_bit(EXTENT_FLAG_PREALLOC, &em->flags);
+		set_bit(EXTENT_FLAG_FILLING, &em->flags);
 
 	do {
 		btrfs_drop_extent_cache(inode, em->start,
 				em->start + em->len - 1, 0);
 		write_lock(&em_tree->lock);
 		ret = add_extent_mapping(em_tree, em);
+		if (!ret)
+			list_move(&em->list,
+				  &em_tree->modified_extents);
 		write_unlock(&em_tree->lock);
 	} while (ret == -EEXIST);
 
···
 			goto must_cow;
 
 		if (can_nocow_odirect(trans, inode, start, len) == 1) {
-			u64 orig_start = em->start;
+			u64 orig_start = em->orig_start;
+			u64 orig_block_len = em->orig_block_len;
 
 			if (type == BTRFS_ORDERED_PREALLOC) {
 				free_extent_map(em);
 				em = create_pinned_em(inode, start, len,
 						       orig_start,
-						       block_start, len, type);
+						       block_start, len,
+						       orig_block_len, type);
 				if (IS_ERR(em)) {
 					btrfs_end_transaction(trans, root);
 					goto unlock_err;
···
 	 * it above
 	 */
 	len = bh_result->b_size;
-	em = btrfs_new_extent_direct(inode, em, start, len);
+	free_extent_map(em);
+	em = btrfs_new_extent_direct(inode, start, len);
 	if (IS_ERR(em)) {
 		ret = PTR_ERR(em);
 		goto unlock_err;
···
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	int ret;
 
+	if (async_submit)
+		async_submit = !atomic_read(&BTRFS_I(inode)->sync_writers);
+
 	bio_get(bio);
 
 	if (!write) {
···
 {
 	struct inode *inode = dip->inode;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
-	struct btrfs_mapping_tree *map_tree = &root->fs_info->mapping_tree;
 	struct bio *bio;
 	struct bio *orig_bio = dip->orig_bio;
 	struct bio_vec *bvec = orig_bio->bi_io_vec;
···
 	int async_submit = 0;
 
 	map_length = orig_bio->bi_size;
-	ret = btrfs_map_block(map_tree, READ, start_sector << 9,
+	ret = btrfs_map_block(root->fs_info, READ, start_sector << 9,
 			      &map_length, NULL, 0);
 	if (ret) {
 		bio_put(orig_bio);
···
 			bio->bi_end_io = btrfs_end_dio_bio;
 
 			map_length = orig_bio->bi_size;
-			ret = btrfs_map_block(map_tree, READ, start_sector << 9,
+			ret = btrfs_map_block(root->fs_info, READ,
+					      start_sector << 9,
 					      &map_length, NULL, 0);
 			if (ret) {
 				bio_put(bio);
···
 		   btrfs_submit_direct, 0);
 }
 
+#define BTRFS_FIEMAP_FLAGS	(FIEMAP_FLAG_SYNC)
+
 static int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		__u64 start, __u64 len)
 {
+	int	ret;
+
+	ret = fiemap_check_flags(fieinfo, BTRFS_FIEMAP_FLAGS);
+	if (ret)
+		return ret;
+
 	return extent_fiemap(inode, fieinfo, start, len, btrfs_get_extent_fiemap);
 }
 
···
 	int ret;
 	int err = 0;
 	struct btrfs_trans_handle *trans;
-	unsigned long nr;
 	u64 mask = root->sectorsize - 1;
 	u64 min_size = btrfs_calc_trunc_metadata_size(root, 1);
 
···
 			break;
 		}
 
-		nr = trans->blocks_used;
 		btrfs_end_transaction(trans, root);
-		btrfs_btree_balance_dirty(root, nr);
+		btrfs_btree_balance_dirty(root);
 
 		trans = btrfs_start_transaction(root, 2);
 		if (IS_ERR(trans)) {
···
 		if (ret && !err)
 			err = ret;
 
-		nr = trans->blocks_used;
 		ret = btrfs_end_transaction(trans, root);
-		btrfs_btree_balance_dirty(root, nr);
+		btrfs_btree_balance_dirty(root);
 	}
 
 out:
···
 	extent_io_tree_init(&ei->io_failure_tree, &inode->i_data);
 	ei->io_tree.track_uptodate = 1;
 	ei->io_failure_tree.track_uptodate = 1;
+	atomic_set(&ei->sync_writers, 0);
 	mutex_init(&ei->log_mutex);
 	mutex_init(&ei->delalloc_mutex);
 	btrfs_ordered_inode_tree_init(&ei->ordered_tree);
···
 		kmem_cache_destroy(btrfs_path_cachep);
 	if (btrfs_free_space_cachep)
 		kmem_cache_destroy(btrfs_free_space_cachep);
+	if (btrfs_delalloc_work_cachep)
+		kmem_cache_destroy(btrfs_delalloc_work_cachep);
 }
 
 int btrfs_init_cachep(void)
···
 			sizeof(struct btrfs_free_space), 0,
 			SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
 	if (!btrfs_free_space_cachep)
+		goto fail;
+
+	btrfs_delalloc_work_cachep = kmem_cache_create("btrfs_delalloc_work",
+			sizeof(struct btrfs_delalloc_work), 0,
+			SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
+			NULL);
+	if (!btrfs_delalloc_work_cachep)
 		goto fail;
 
 	return 0;
···
 	if (S_ISDIR(old_inode->i_mode) && new_inode &&
 	    new_inode->i_size > BTRFS_EMPTY_DIR_SIZE)
 		return -ENOTEMPTY;
+
+
+	/* check for collisions, even if the  name isn't there */
+	ret = btrfs_check_dir_item_collision(root, new_dir->i_ino,
+			     new_dentry->d_name.name,
+			     new_dentry->d_name.len);
+
+	if (ret) {
+		if (ret == -EEXIST) {
+			/* we shouldn't get
+			 * eexist without a new_inode */
+			if (!new_inode) {
+				WARN_ON(1);
+				return ret;
+			}
+		} else {
+			/* maybe -EOVERFLOW */
+			return ret;
+		}
+	}
+	ret = 0;
+
 	/*
 	 * we're using rename to replace one file with another.
 	 * and the replacement file is large.  Start IO on it now so
···
 	return ret;
 }
 
+static void btrfs_run_delalloc_work(struct btrfs_work *work)
+{
+	struct btrfs_delalloc_work *delalloc_work;
+
+	delalloc_work = container_of(work, struct btrfs_delalloc_work,
+				     work);
+	if (delalloc_work->wait)
+		btrfs_wait_ordered_range(delalloc_work->inode, 0, (u64)-1);
+	else
+		filemap_flush(delalloc_work->inode->i_mapping);
+
+	if (delalloc_work->delay_iput)
+		btrfs_add_delayed_iput(delalloc_work->inode);
+	else
+		iput(delalloc_work->inode);
+	complete(&delalloc_work->completion);
+}
+
+struct btrfs_delalloc_work *btrfs_alloc_delalloc_work(struct inode *inode,
+						    int wait, int delay_iput)
+{
+	struct btrfs_delalloc_work *work;
+
+	work = kmem_cache_zalloc(btrfs_delalloc_work_cachep, GFP_NOFS);
+	if (!work)
+		return NULL;
+
+	init_completion(&work->completion);
+	INIT_LIST_HEAD(&work->list);
+	work->inode = inode;
+	work->wait = wait;
+	work->delay_iput = delay_iput;
+	work->work.func = btrfs_run_delalloc_work;
+
+	return work;
+}
+
+void btrfs_wait_and_free_delalloc_work(struct btrfs_delalloc_work *work)
+{
+	wait_for_completion(&work->completion);
+	kmem_cache_free(btrfs_delalloc_work_cachep, work);
+}
+
 /*
  * some fairly slow code that needs optimization. This walks the list
  * of all the inodes with pending delalloc and forces them to disk.
···
 	struct list_head *head = &root->fs_info->delalloc_inodes;
 	struct btrfs_inode *binode;
 	struct inode *inode;
+	struct btrfs_delalloc_work *work, *next;
+	struct list_head works;
+	int ret = 0;
 
 	if (root->fs_info->sb->s_flags & MS_RDONLY)
 		return -EROFS;
+
+	INIT_LIST_HEAD(&works);
 
 	spin_lock(&root->fs_info->delalloc_lock);
 	while (!list_empty(head)) {
···
 			list_del_init(&binode->delalloc_inodes);
 		spin_unlock(&root->fs_info->delalloc_lock);
 		if (inode) {
-			filemap_flush(inode->i_mapping);
-			if (delay_iput)
-				btrfs_add_delayed_iput(inode);
-			else
-				iput(inode);
+			work = btrfs_alloc_delalloc_work(inode, 0, delay_iput);
+			if (!work) {
+				ret = -ENOMEM;
+				goto out;
+			}
+			list_add_tail(&work->list, &works);
+			btrfs_queue_worker(&root->fs_info->flush_workers,
+					   &work->work);
 		}
 		cond_resched();
 		spin_lock(&root->fs_info->delalloc_lock);
···
 		    atomic_read(&root->fs_info->async_delalloc_pages) == 0));
 	}
 	atomic_dec(&root->fs_info->async_submit_draining);
-	return 0;
+out:
+	list_for_each_entry_safe(work, next, &works, list) {
+		list_del_init(&work->list);
+		btrfs_wait_and_free_delalloc_work(work);
+	}
+	return ret;
 }
 
 static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
···
 	unsigned long ptr;
 	struct btrfs_file_extent_item *ei;
 	struct extent_buffer *leaf;
-	unsigned long nr = 0;
 
 	name_len = strlen(symname) + 1;
 	if (name_len > BTRFS_MAX_INLINE_DATA_SIZE(root))
···
 out_unlock:
 	if (!err)
 		d_instantiate(dentry, inode);
-	nr = trans->blocks_used;
 	btrfs_end_transaction(trans, root);
 	if (drop_inode) {
 		inode_dec_link_count(inode);
 		iput(inode);
 	}
-	btrfs_btree_balance_dirty(root, nr);
+	btrfs_btree_balance_dirty(root);
 	return err;
 }
 
···
 		em->len = ins.offset;
 		em->block_start = ins.objectid;
 		em->block_len = ins.offset;
+		em->orig_block_len = ins.offset;
 		em->bdev = root->fs_info->fs_devices->latest_bdev;
 		set_bit(EXTENT_FLAG_PREALLOC, &em->flags);
 		em->generation = trans->transid;

fs/btrfs/ioctl.c

···
 #include "backref.h"
 #include "rcu-string.h"
 #include "send.h"
+#include "dev-replace.h"
 
 /* Mask out flags that are inappropriate for the given type of inode. */
 static inline __u32 btrfs_mask_flags(umode_t mode, __u32 flags)
···
 		BTRFS_I(inode)->flags |= BTRFS_INODE_COMPRESS;
 	}
 
-	if (flags & BTRFS_INODE_NODATACOW)
+	if (flags & BTRFS_INODE_NODATACOW) {
 		BTRFS_I(inode)->flags |= BTRFS_INODE_NODATACOW;
+		if (S_ISREG(inode->i_mode))
+			BTRFS_I(inode)->flags |= BTRFS_INODE_NODATASUM;
+	}
 
 	btrfs_update_iflags(inode);
 }
···
 		ret = btrfs_commit_transaction(trans,
 					       root->fs_info->extent_root);
 	}
-	if (ret)
+	if (ret) {
+		/* cleanup_transaction has freed this for us */
+		if (trans->aborted)
+			pending_snapshot = NULL;
 		goto fail;
+	}
 
 	ret = pending_snapshot->error;
 	if (ret)
···
 		goto out_dput;
 
 	error = btrfs_may_create(dir, dentry);
+	if (error)
+		goto out_dput;
+
+	/*
+	 * even if this name doesn't exist, we may get hash collisions.
+	 * check for them now when we can safely fail
+	 */
+	error = btrfs_check_dir_item_collision(BTRFS_I(dir)->root,
+					       dir->i_ino, name,
+					       namelen);
 	if (error)
 		goto out_dput;
 
···
 	return ret;
 }
 
-static noinline int btrfs_ioctl_resize(struct btrfs_root *root,
+static noinline int btrfs_ioctl_resize(struct file *file,
 					void __user *arg)
 {
 	u64 new_size;
 	u64 old_size;
 	u64 devid = 1;
+	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
 	struct btrfs_ioctl_vol_args *vol_args;
 	struct btrfs_trans_handle *trans;
 	struct btrfs_device *device = NULL;
···
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	mutex_lock(&root->fs_info->volume_mutex);
-	if (root->fs_info->balance_ctl) {
-		printk(KERN_INFO "btrfs: balance in progress\n");
-		ret = -EINVAL;
-		goto out;
+	ret = mnt_want_write_file(file);
+	if (ret)
+		return ret;
+
+	if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,
+			1)) {
+		pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
+		return -EINPROGRESS;
 	}
 
+	mutex_lock(&root->fs_info->volume_mutex);
 	vol_args = memdup_user(arg, sizeof(*vol_args));
 	if (IS_ERR(vol_args)) {
 		ret = PTR_ERR(vol_args);
···
 		printk(KERN_INFO "btrfs: resizing devid %llu\n",
 		       (unsigned long long)devid);
 	}
-	device = btrfs_find_device(root, devid, NULL, NULL);
+	device = btrfs_find_device(root->fs_info, devid, NULL, NULL);
 	if (!device) {
 		printk(KERN_INFO "btrfs: resizer unable to find device %llu\n",
 		       (unsigned long long)devid);
···
 			ret = -EINVAL;
 			goto out_free;
 		}
+	}
+
+	if (device->is_tgtdev_for_dev_replace) {
+		ret = -EINVAL;
+		goto out_free;
 	}
 
 	old_size = device->total_bytes;
···
 		btrfs_commit_transaction(trans, root);
 	} else if (new_size < old_size) {
 		ret = btrfs_shrink_device(device, new_size);
-	}
+	} /* equal, nothing need to do */
 
 out_free:
 	kfree(vol_args);
 out:
 	mutex_unlock(&root->fs_info->volume_mutex);
+	mnt_drop_write_file(file);
+	atomic_set(&root->fs_info->mutually_exclusive_operation_running, 0);
 	return ret;
 }
 
···
 	if (btrfs_root_readonly(root))
 		return -EROFS;
 
+	if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,
+			1)) {
+		pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
+		return -EINPROGRESS;
+	}
 	ret = mnt_want_write_file(file);
-	if (ret)
+	if (ret) {
+		atomic_set(&root->fs_info->mutually_exclusive_operation_running,
+			   0);
 		return ret;
+	}
 
 	switch (inode->i_mode & S_IFMT) {
 	case S_IFDIR:
···
 	}
 out:
 	mnt_drop_write_file(file);
+	atomic_set(&root->fs_info->mutually_exclusive_operation_running, 0);
 	return ret;
 }
 
···
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	mutex_lock(&root->fs_info->volume_mutex);
-	if (root->fs_info->balance_ctl) {
-		printk(KERN_INFO "btrfs: balance in progress\n");
-		ret = -EINVAL;
-		goto out;
+	if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,
+			1)) {
+		pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
+		return -EINPROGRESS;
 	}
 
+	mutex_lock(&root->fs_info->volume_mutex);
 	vol_args = memdup_user(arg, sizeof(*vol_args));
 	if (IS_ERR(vol_args)) {
 		ret = PTR_ERR(vol_args);
···
 	kfree(vol_args);
 out:
 	mutex_unlock(&root->fs_info->volume_mutex);
+	atomic_set(&root->fs_info->mutually_exclusive_operation_running, 0);
 	return ret;
 }
 
-static long btrfs_ioctl_rm_dev(struct btrfs_root *root, void __user *arg)
+static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
 {
+	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
 	struct btrfs_ioctl_vol_args *vol_args;
 	int ret;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	if (root->fs_info->sb->s_flags & MS_RDONLY)
-		return -EROFS;
+	ret = mnt_want_write_file(file);
+	if (ret)
+		return ret;
 
-	mutex_lock(&root->fs_info->volume_mutex);
-	if (root->fs_info->balance_ctl) {
-		printk(KERN_INFO "btrfs: balance in progress\n");
-		ret = -EINVAL;
-		goto out;
+	if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,
+			1)) {
+		pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
+		mnt_drop_write_file(file);
+		return -EINPROGRESS;
 	}
 
+	mutex_lock(&root->fs_info->volume_mutex);
 	vol_args = memdup_user(arg, sizeof(*vol_args));
 	if (IS_ERR(vol_args)) {
 		ret = PTR_ERR(vol_args);
···
 	kfree(vol_args);
 out:
 	mutex_unlock(&root->fs_info->volume_mutex);
+	mnt_drop_write_file(file);
+	atomic_set(&root->fs_info->mutually_exclusive_operation_running, 0);
 	return ret;
 }
 
···
 		s_uuid = di_args->uuid;
 
 	mutex_lock(&fs_devices->device_list_mutex);
-	dev = btrfs_find_device(root, di_args->devid, s_uuid, NULL);
+	dev = btrfs_find_device(root->fs_info, di_args->devid, s_uuid, NULL);
 	mutex_unlock(&fs_devices->device_list_mutex);
 
 	if (!dev) {
···
 	struct btrfs_disk_key disk_key;
 	u64 objectid = 0;
 	u64 dir_id;
+	int ret;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	if (copy_from_user(&objectid, argp, sizeof(objectid)))
-		return -EFAULT;
+	ret = mnt_want_write_file(file);
+	if (ret)
+		return ret;
+
+	if (copy_from_user(&objectid, argp, sizeof(objectid))) {
+		ret = -EFAULT;
+		goto out;
+	}
 
 	if (!objectid)
 		objectid = root->root_key.objectid;
···
 	location.offset = (u64)-1;
 
 	new_root = btrfs_read_fs_root_no_name(root->fs_info, &location);
-	if (IS_ERR(new_root))
-		return PTR_ERR(new_root);
+	if (IS_ERR(new_root)) {
+		ret = PTR_ERR(new_root);
+		goto out;
+	}
 
-	if (btrfs_root_refs(&new_root->root_item) == 0)
-		return -ENOENT;
+	if (btrfs_root_refs(&new_root->root_item) == 0) {
+		ret = -ENOENT;
+		goto out;
+	}
 
 	path = btrfs_alloc_path();
-	if (!path)
-		return -ENOMEM;
+	if (!path) {
+		ret = -ENOMEM;
+		goto out;
+	}
 	path->leave_spinning = 1;
 
 	trans = btrfs_start_transaction(root, 1);
 	if (IS_ERR(trans)) {
 		btrfs_free_path(path);
-		return PTR_ERR(trans);
+		ret = PTR_ERR(trans);
+		goto out;
 	}
 
 	dir_id = btrfs_super_root_dir(root->fs_info->super_copy);
···
 		btrfs_end_transaction(trans, root);
 		printk(KERN_ERR "Umm, you don't have the default dir item, "
 		       "this isn't going to work\n");
-		return -ENOENT;
+		ret = -ENOENT;
+		goto out;
 	}
 
 	btrfs_cpu_key_to_disk(&disk_key, &new_root->root_key);
···
 
 	btrfs_set_fs_incompat(root->fs_info, DEFAULT_SUBVOL);
 	btrfs_end_transaction(trans, root);
-
-	return 0;
+out:
+	mnt_drop_write_file(file);
+	return ret;
 }
 
 void btrfs_get_block_group_info(struct list_head *groups_list,
···
 	return 0;
 }
 
-static noinline long btrfs_ioctl_start_sync(struct file *file, void __user *argp)
+static noinline long btrfs_ioctl_start_sync(struct btrfs_root *root,
+					    void __user *argp)
 {
-	struct btrfs_root *root = BTRFS_I(file->f_dentry->d_inode)->root;
 	struct btrfs_trans_handle *trans;
 	u64 transid;
 	int ret;
 
-	trans = btrfs_start_transaction(root, 0);
-	if (IS_ERR(trans))
-		return PTR_ERR(trans);
+	trans = btrfs_attach_transaction(root);
+	if (IS_ERR(trans)) {
+		if (PTR_ERR(trans) != -ENOENT)
+			return PTR_ERR(trans);
+
+		/* No running transaction, don't bother */
+		transid = root->fs_info->last_trans_committed;
+		goto out;
+	}
 	transid = trans->transid;
 	ret = btrfs_commit_transaction_async(trans, root, 0);
 	if (ret) {
 		btrfs_end_transaction(trans, root);
 		return ret;
 	}
-
+out:
 	if (argp)
 		if (copy_to_user(argp, &transid, sizeof(transid)))
 			return -EFAULT;
 	return 0;
 }
 
-static noinline long btrfs_ioctl_wait_sync(struct file *file, void __user *argp)
+static noinline long btrfs_ioctl_wait_sync(struct btrfs_root *root,
+					   void __user *argp)
 {
-	struct btrfs_root *root = BTRFS_I(file->f_dentry->d_inode)->root;
 	u64 transid;
 
 	if (argp) {
···
 	return btrfs_wait_for_commit(root, transid);
 }
 
-static long btrfs_ioctl_scrub(struct btrfs_root *root, void __user *arg)
+static long btrfs_ioctl_scrub(struct file *file, void __user *arg)
 {
-	int ret;
+	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
 	struct btrfs_ioctl_scrub_args *sa;
+	int ret;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
···
 	if (IS_ERR(sa))
 		return PTR_ERR(sa);
 
-	ret = btrfs_scrub_dev(root, sa->devid, sa->start, sa->end,
-			      &sa->progress, sa->flags & BTRFS_SCRUB_READONLY);
+	if (!(sa->flags & BTRFS_SCRUB_READONLY)) {
+		ret = mnt_want_write_file(file);
+		if (ret)
+			goto out;
+	}
+
+	ret = btrfs_scrub_dev(root->fs_info, sa->devid, sa->start, sa->end,
+			      &sa->progress, sa->flags & BTRFS_SCRUB_READONLY,
+			      0);
 
 	if (copy_to_user(arg, sa, sizeof(*sa)))
 		ret = -EFAULT;
 
+	if (!(sa->flags & BTRFS_SCRUB_READONLY))
+		mnt_drop_write_file(file);
+out:
 	kfree(sa);
 	return ret;
 }
···
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	return btrfs_scrub_cancel(root);
+	return btrfs_scrub_cancel(root->fs_info);
 }
 
 static long btrfs_ioctl_scrub_progress(struct btrfs_root *root,
···
 		ret = -EFAULT;
 
 	kfree(sa);
+	return ret;
+}
+
+static long btrfs_ioctl_dev_replace(struct btrfs_root *root, void __user *arg)
+{
+	struct btrfs_ioctl_dev_replace_args *p;
+	int ret;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	p = memdup_user(arg, sizeof(*p));
+	if (IS_ERR(p))
+		return PTR_ERR(p);
+
+	switch (p->cmd) {
+	case BTRFS_IOCTL_DEV_REPLACE_CMD_START:
+		if (atomic_xchg(
+			&root->fs_info->mutually_exclusive_operation_running,
+			1)) {
+			pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
+			ret = -EINPROGRESS;
+		} else {
+			ret = btrfs_dev_replace_start(root, p);
+			atomic_set(
+			 &root->fs_info->mutually_exclusive_operation_running,
+			 0);
+		}
+		break;
+	case BTRFS_IOCTL_DEV_REPLACE_CMD_STATUS:
+		btrfs_dev_replace_status(root->fs_info, p);
+		ret = 0;
+		break;
+	case BTRFS_IOCTL_DEV_REPLACE_CMD_CANCEL:
+		ret = btrfs_dev_replace_cancel(root->fs_info, p);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	if (copy_to_user(arg, p, sizeof(*p)))
+		ret = -EFAULT;
+
+	kfree(p);
 	return ret;
 }
 
···
 	struct btrfs_ioctl_balance_args *bargs;
 	struct btrfs_balance_control *bctl;
 	int ret;
+	int need_to_clear_lock = 0;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
···
 		bargs = NULL;
 	}
 
-	if (fs_info->balance_ctl) {
+	if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,
+			1)) {
+		pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
 		ret = -EINPROGRESS;
 		goto out_bargs;
 	}
+	need_to_clear_lock = 1;
 
 	bctl = kzalloc(sizeof(*bctl), GFP_NOFS);
 	if (!bctl) {
···
 out_bargs:
 	kfree(bargs);
 out:
+	if (need_to_clear_lock)
+		atomic_set(&root->fs_info->mutually_exclusive_operation_running,
+			   0);
 	mutex_unlock(&fs_info->balance_mutex);
 	mutex_unlock(&fs_info->volume_mutex);
 	mnt_drop_write_file(file);
···
 	return ret;
 }
 
-static long btrfs_ioctl_quota_ctl(struct btrfs_root *root, void __user *arg)
+static long btrfs_ioctl_quota_ctl(struct file *file, void __user *arg)
 {
+	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
 	struct btrfs_ioctl_quota_ctl_args *sa;
 	struct btrfs_trans_handle *trans = NULL;
 	int ret;
···
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	if (root->fs_info->sb->s_flags & MS_RDONLY)
-		return -EROFS;
+	ret = mnt_want_write_file(file);
+	if (ret)
+		return ret;
 
 	sa = memdup_user(arg, sizeof(*sa));
-	if (IS_ERR(sa))
-		return PTR_ERR(sa);
+	if (IS_ERR(sa)) {
+		ret = PTR_ERR(sa);
+		goto drop_write;
+	}
 
 	if (sa->cmd != BTRFS_QUOTA_CTL_RESCAN) {
 		trans = btrfs_start_transaction(root, 2);
···
 		if (err && !ret)
 			ret = err;
 	}
-
 out:
 	kfree(sa);
+drop_write:
+	mnt_drop_write_file(file);
 	return ret;
 }
 
-static long btrfs_ioctl_qgroup_assign(struct btrfs_root *root, void __user *arg)
+static long btrfs_ioctl_qgroup_assign(struct file *file, void __user *arg)
 {
+	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
 	struct btrfs_ioctl_qgroup_assign_args *sa;
 	struct btrfs_trans_handle *trans;
 	int ret;
···
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	if (root->fs_info->sb->s_flags & MS_RDONLY)
-		return -EROFS;
+	ret = mnt_want_write_file(file);
+	if (ret)
+		return ret;
 
 	sa = memdup_user(arg, sizeof(*sa));
-	if (IS_ERR(sa))
-		return PTR_ERR(sa);
+	if (IS_ERR(sa)) {
+		ret = PTR_ERR(sa);
+		goto drop_write;
+	}
 
 	trans = btrfs_join_transaction(root);
 	if (IS_ERR(trans)) {
···
 
 out:
 	kfree(sa);
+drop_write:
+	mnt_drop_write_file(file);
 	return ret;
 }
 
-static long btrfs_ioctl_qgroup_create(struct btrfs_root *root, void __user *arg)
+static long btrfs_ioctl_qgroup_create(struct file *file, void __user *arg)
 {
+	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
 	struct btrfs_ioctl_qgroup_create_args *sa;
 	struct btrfs_trans_handle *trans;
 	int ret;
···
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	if (root->fs_info->sb->s_flags & MS_RDONLY)
-		return -EROFS;
+	ret = mnt_want_write_file(file);
+	if (ret)
+		return ret;
 
 	sa = memdup_user(arg, sizeof(*sa));
-	if (IS_ERR(sa))
-		return PTR_ERR(sa);
+	if (IS_ERR(sa)) {
+		ret = PTR_ERR(sa);
+		goto drop_write;
+	}
 
 	trans = btrfs_join_transaction(root);
 	if (IS_ERR(trans)) {
···
 
 out:
 	kfree(sa);
+drop_write:
+	mnt_drop_write_file(file);
 	return ret;
 }
 
-static long btrfs_ioctl_qgroup_limit(struct btrfs_root *root, void __user *arg)
+static long btrfs_ioctl_qgroup_limit(struct file *file, void __user *arg)
 {
+	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
 	struct btrfs_ioctl_qgroup_limit_args *sa;
 	struct btrfs_trans_handle *trans;
 	int ret;
···
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	if (root->fs_info->sb->s_flags & MS_RDONLY)
-		return -EROFS;
+	ret = mnt_want_write_file(file);
+	if (ret)
+		return ret;
 
 	sa = memdup_user(arg, sizeof(*sa));
-	if (IS_ERR(sa))
-		return PTR_ERR(sa);
+	if (IS_ERR(sa)) {
+		ret = PTR_ERR(sa);
+		goto drop_write;
+	}
 
 	trans = btrfs_join_transaction(root);
 	if (IS_ERR(trans)) {
···
 
 out:
 	kfree(sa);
+drop_write:
+	mnt_drop_write_file(file);
 	return ret;
 }
 
···
 	case BTRFS_IOC_DEFRAG_RANGE:
 		return btrfs_ioctl_defrag(file, argp);
 	case BTRFS_IOC_RESIZE:
-		return btrfs_ioctl_resize(root, argp);
+		return btrfs_ioctl_resize(file, argp);
 	case BTRFS_IOC_ADD_DEV:
 		return btrfs_ioctl_add_dev(root, argp);
 	case BTRFS_IOC_RM_DEV:
-		return btrfs_ioctl_rm_dev(root, argp);
+		return btrfs_ioctl_rm_dev(file, argp);
 	case BTRFS_IOC_FS_INFO:
 		return btrfs_ioctl_fs_info(root, argp);
 	case BTRFS_IOC_DEV_INFO:
···
 		btrfs_sync_fs(file->f_dentry->d_sb, 1);
 		return 0;
 	case BTRFS_IOC_START_SYNC:
-		return btrfs_ioctl_start_sync(file, argp);
+		return btrfs_ioctl_start_sync(root, argp);
 	case BTRFS_IOC_WAIT_SYNC:
-		return btrfs_ioctl_wait_sync(file, argp);
+		return btrfs_ioctl_wait_sync(root, argp);
 	case BTRFS_IOC_SCRUB:
-		return btrfs_ioctl_scrub(root, argp);
+		return btrfs_ioctl_scrub(file, argp);
 	case BTRFS_IOC_SCRUB_CANCEL:
 		return btrfs_ioctl_scrub_cancel(root, argp);
 	case BTRFS_IOC_SCRUB_PROGRESS:
···
 	case BTRFS_IOC_GET_DEV_STATS:
 		return btrfs_ioctl_get_dev_stats(root, argp);
 	case BTRFS_IOC_QUOTA_CTL:
-		return btrfs_ioctl_quota_ctl(root, argp);
+		return btrfs_ioctl_quota_ctl(file, argp);
 	case BTRFS_IOC_QGROUP_ASSIGN:
-		return btrfs_ioctl_qgroup_assign(root, argp);
+		return btrfs_ioctl_qgroup_assign(file, argp);
 	case BTRFS_IOC_QGROUP_CREATE:
-		return btrfs_ioctl_qgroup_create(root, argp);
+		return btrfs_ioctl_qgroup_create(file, argp);
 	case BTRFS_IOC_QGROUP_LIMIT:
-		return btrfs_ioctl_qgroup_limit(root, argp);
+		return btrfs_ioctl_qgroup_limit(file, argp);
+	case BTRFS_IOC_DEV_REPLACE:
+		return btrfs_ioctl_dev_replace(root, argp);
 	}
 
 	return -ENOTTY;

fs/btrfs/ioctl.h

···
 	char name[BTRFS_PATH_NAME_MAX + 1];
 };
 
+#define BTRFS_DEVICE_PATH_NAME_MAX 1024
+
 #define BTRFS_SUBVOL_CREATE_ASYNC	(1ULL << 0)
 #define BTRFS_SUBVOL_RDONLY		(1ULL << 1)
 #define BTRFS_SUBVOL_QGROUP_INHERIT	(1ULL << 2)
···
 	__u64 unused[(1024-32-sizeof(struct btrfs_scrub_progress))/8];
 };
 
-#define BTRFS_DEVICE_PATH_NAME_MAX 1024
+#define BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_ALWAYS	0
+#define BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_AVOID	1
+struct btrfs_ioctl_dev_replace_start_params {
+	__u64 srcdevid;	/* in, if 0, use srcdev_name instead */
+	__u64 cont_reading_from_srcdev_mode;	/* in, see #define
+						 * above */
+	__u8 srcdev_name[BTRFS_DEVICE_PATH_NAME_MAX + 1];	/* in */
+	__u8 tgtdev_name[BTRFS_DEVICE_PATH_NAME_MAX + 1];	/* in */
+};
+
+#define BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED	0
+#define BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED		1
+#define BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED		2
+#define BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED		3
+#define BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED		4
+struct btrfs_ioctl_dev_replace_status_params {
+	__u64 replace_state;	/* out, see #define above */
+	__u64 progress_1000;	/* out, 0 <= x <= 1000 */
+	__u64 time_started;	/* out, seconds since 1-Jan-1970 */
+	__u64 time_stopped;	/* out, seconds since 1-Jan-1970 */
+	__u64 num_write_errors;	/* out */
+	__u64 num_uncorrectable_read_errors;	/* out */
+};
+
+#define BTRFS_IOCTL_DEV_REPLACE_CMD_START			0
+#define BTRFS_IOCTL_DEV_REPLACE_CMD_STATUS			1
+#define BTRFS_IOCTL_DEV_REPLACE_CMD_CANCEL			2
+#define BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR			0
+#define BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED		1
+#define BTRFS_IOCTL_DEV_REPLACE_RESULT_ALREADY_STARTED		2
+struct btrfs_ioctl_dev_replace_args {
+	__u64 cmd;	/* in */
+	__u64 result;	/* out */
+
+	union {
+		struct btrfs_ioctl_dev_replace_start_params start;
+		struct btrfs_ioctl_dev_replace_status_params status;
+	};	/* in/out */
+
+	__u64 spare[64];
+};
+
 struct btrfs_ioctl_dev_info_args {
 	__u64 devid;				/* in/out */
 	__u8 uuid[BTRFS_UUID_SIZE];		/* in/out */
···
 			       struct btrfs_ioctl_qgroup_limit_args)
 #define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
 				      struct btrfs_ioctl_get_dev_stats)
+#define BTRFS_IOC_DEV_REPLACE _IOWR(BTRFS_IOCTL_MAGIC, 53, \
+				    struct btrfs_ioctl_dev_replace_args)
+
 #endif

fs/btrfs/math.h

···
+
+/*
+ * Copyright (C) 2012 Fujitsu.  All rights reserved.
+ * Written by Miao Xie <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#ifndef __BTRFS_MATH_H
+#define __BTRFS_MATH_H
+
+#include <asm/div64.h>
+
+static inline u64 div_factor(u64 num, int factor)
+{
+	if (factor == 10)
+		return num;
+	num *= factor;
+	do_div(num, 10);
+	return num;
+}
+
+static inline u64 div_factor_fine(u64 num, int factor)
+{
+	if (factor == 100)
+		return num;
+	num *= factor;
+	do_div(num, 100);
+	return num;
+}
+
+#endif

fs/btrfs/ordered-data.c

···
 	init_waitqueue_head(&entry->wait);
 	INIT_LIST_HEAD(&entry->list);
 	INIT_LIST_HEAD(&entry->root_extent_list);
+	INIT_LIST_HEAD(&entry->work_list);
+	init_completion(&entry->completion);
 
 	trace_btrfs_ordered_extent_add(inode, entry);
 
···
 	wake_up(&entry->wait);
 }
 
+static void btrfs_run_ordered_extent_work(struct btrfs_work *work)
+{
+	struct btrfs_ordered_extent *ordered;
+
+	ordered = container_of(work, struct btrfs_ordered_extent, flush_work);
+	btrfs_start_ordered_extent(ordered->inode, ordered, 1);
+	complete(&ordered->completion);
+}
+
 /*
  * wait for all the ordered extents in a root.  This is done when balancing
  * space between drives.
  */
 void btrfs_wait_ordered_extents(struct btrfs_root *root, int delay_iput)
 {
-	struct list_head splice;
+	struct list_head splice, works;
 	struct list_head *cur;
-	struct btrfs_ordered_extent *ordered;
+	struct btrfs_ordered_extent *ordered, *next;
 	struct inode *inode;
 
 	INIT_LIST_HEAD(&splice);
+	INIT_LIST_HEAD(&works);
 
 	spin_lock(&root->fs_info->ordered_extent_lock);
 	list_splice_init(&root->fs_info->ordered_extents, &splice);
···
 		spin_unlock(&root->fs_info->ordered_extent_lock);
 
 		if (inode) {
-			btrfs_start_ordered_extent(inode, ordered, 1);
-			btrfs_put_ordered_extent(ordered);
-			if (delay_iput)
-				btrfs_add_delayed_iput(inode);
-			else
-				iput(inode);
+			ordered->flush_work.func = btrfs_run_ordered_extent_work;
+			list_add_tail(&ordered->work_list, &works);
+			btrfs_queue_worker(&root->fs_info->flush_workers,
+					   &ordered->flush_work);
 		} else {
 			btrfs_put_ordered_extent(ordered);
 		}
 
+		cond_resched();
 		spin_lock(&root->fs_info->ordered_extent_lock);
 	}
 	spin_unlock(&root->fs_info->ordered_extent_lock);
+
+	list_for_each_entry_safe(ordered, next, &works, work_list) {
+		list_del_init(&ordered->work_list);
+		wait_for_completion(&ordered->completion);
+
+		inode = ordered->inode;
+		btrfs_put_ordered_extent(ordered);
+		if (delay_iput)
+			btrfs_add_delayed_iput(inode);
+		else
+			iput(inode);
+
+		cond_resched();
+	}
 }
 
 /*
···
  * extra check to make sure the ordered operation list really is empty
  * before we return
  */
-void btrfs_run_ordered_operations(struct btrfs_root *root, int wait)
+int btrfs_run_ordered_operations(struct btrfs_root *root, int wait)
 {
 	struct btrfs_inode *btrfs_inode;
 	struct inode *inode;
 	struct list_head splice;
+	struct list_head works;
+	struct btrfs_delalloc_work *work, *next;
+	int ret = 0;
 
 	INIT_LIST_HEAD(&splice);
+	INIT_LIST_HEAD(&works);
 
 	mutex_lock(&root->fs_info->ordered_operations_mutex);
 	spin_lock(&root->fs_info->ordered_extent_lock);
···
 	list_splice_init(&root->fs_info->ordered_operations, &splice);
 
 	while (!list_empty(&splice)) {
+
 		btrfs_inode = list_entry(splice.next, struct btrfs_inode,
 				   ordered_operations);
 
···
 			list_add_tail(&BTRFS_I(inode)->ordered_operations,
 			      &root->fs_info->ordered_operations);
 		}
+
+		if (!inode)
+			continue;
 		spin_unlock(&root->fs_info->ordered_extent_lock);
 
-		if (inode) {
-			if (wait)
-				btrfs_wait_ordered_range(inode, 0, (u64)-1);
-			else
-				filemap_flush(inode->i_mapping);
-			btrfs_add_delayed_iput(inode);
+		work = btrfs_alloc_delalloc_work(inode, wait, 1);
+		if (!work) {
+			if (list_empty(&BTRFS_I(inode)->ordered_operations))
+				list_add_tail(&btrfs_inode->ordered_operations,
+					      &splice);
+			spin_lock(&root->fs_info->ordered_extent_lock);
+			list_splice_tail(&splice,
+					 &root->fs_info->ordered_operations);
+			spin_unlock(&root->fs_info->ordered_extent_lock);
+			ret = -ENOMEM;
+			goto out;
 		}
+		list_add_tail(&work->list, &works);
+		btrfs_queue_worker(&root->fs_info->flush_workers,
+				   &work->work);
 
 		cond_resched();
 		spin_lock(&root->fs_info->ordered_extent_lock);
···
 		goto again;
 
 	spin_unlock(&root->fs_info->ordered_extent_lock);
+out:
+	list_for_each_entry_safe(work, next, &works, list) {
+		list_del_init(&work->list);
+		btrfs_wait_and_free_delalloc_work(work);
+	}
 	mutex_unlock(&root->fs_info->ordered_operations_mutex);
+	return ret;
 }
 
 /*
···
 	u64 end;
 	u64 orig_end;
 	struct btrfs_ordered_extent *ordered;
-	int found;
 
 	if (start + len < start) {
 		orig_end = INT_LIMIT(loff_t);
···
 	filemap_fdatawait_range(inode->i_mapping, start, orig_end);
 
 	end = orig_end;
-	found = 0;
 	while (1) {
 		ordered = btrfs_lookup_first_ordered_extent(inode, end);
 		if (!ordered)
···
 			btrfs_put_ordered_extent(ordered);
 			break;
 		}
-		found++;
 		btrfs_start_ordered_extent(inode, ordered, 1);
 		end = ordered->file_offset;
 		btrfs_put_ordered_extent(ordered);
···
 	if (last_mod < root->fs_info->last_trans_committed)
 		return;
 
-	/*
-	 * the transaction is already committing.  Just start the IO and
-	 * don't bother with all of this list nonsense
-	 */
-	if (trans && root->fs_info->running_transaction->blocked) {
-		btrfs_wait_ordered_range(inode, 0, (u64)-1);
-		return;
-	}
-
 	spin_lock(&root->fs_info->ordered_extent_lock);
 	if (list_empty(&BTRFS_I(inode)->ordered_operations)) {
 		list_add_tail(&BTRFS_I(inode)->ordered_operations,
···
 				     NULL);
 	if (!btrfs_ordered_extent_cache)
 		return -ENOMEM;
+
 	return 0;
 }
 

fs/btrfs/ordered-data.h

···
 	struct list_head root_extent_list;
 
 	struct btrfs_work work;
-};
 
+	struct completion completion;
+	struct btrfs_work flush_work;
+	struct list_head work_list;
+};
 
 /*
  * calculates the total size you need to allocate for an ordered sum
···
 int btrfs_ordered_update_i_size(struct inode *inode, u64 offset,
 				struct btrfs_ordered_extent *ordered);
 int btrfs_find_ordered_sum(struct inode *inode, u64 offset, u64 disk_bytenr, u32 *sum);
-void btrfs_run_ordered_operations(struct btrfs_root *root, int wait);
+int btrfs_run_ordered_operations(struct btrfs_root *root, int wait);
 void btrfs_add_ordered_operation(struct btrfs_trans_handle *trans,
 				 struct btrfs_root *root,
 				 struct inode *inode);

fs/btrfs/print-tree.c

···
 		case BTRFS_DEV_STATS_KEY:
 			printk(KERN_INFO "\t\tdevice stats\n");
 			break;
+		case BTRFS_DEV_REPLACE_KEY:
+			printk(KERN_INFO "\t\tdev replace\n");
+			break;
 		};
 	}
 }

fs/btrfs/reada.c

···
 #include "volumes.h"
 #include "disk-io.h"
 #include "transaction.h"
+#include "dev-replace.h"
 
 #undef DEBUG
 
···
 	struct reada_extent *re = NULL;
 	struct reada_extent *re_exist = NULL;
 	struct btrfs_fs_info *fs_info = root->fs_info;
-	struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
 	struct btrfs_bio *bbio = NULL;
 	struct btrfs_device *dev;
 	struct btrfs_device *prev_dev;
···
 	int nzones = 0;
 	int i;
 	unsigned long index = logical >> PAGE_CACHE_SHIFT;
+	int dev_replace_is_ongoing;
 
 	spin_lock(&fs_info->reada_lock);
 	re = radix_tree_lookup(&fs_info->reada_tree, index);
···
 	 * map block
 	 */
 	length = blocksize;
-	ret = btrfs_map_block(map_tree, REQ_WRITE, logical, &length, &bbio, 0);
+	ret = btrfs_map_block(fs_info, REQ_GET_READ_MIRRORS, logical, &length,
+			      &bbio, 0);
 	if (ret || !bbio || length < blocksize)
 		goto error;
 
···
 	}
 
 	/* insert extent in reada_tree + all per-device trees, all or nothing */
+	btrfs_dev_replace_lock(&fs_info->dev_replace);
 	spin_lock(&fs_info->reada_lock);
 	ret = radix_tree_insert(&fs_info->reada_tree, index, re);
 	if (ret == -EEXIST) {
···
 		BUG_ON(!re_exist);
 		re_exist->refcnt++;
 		spin_unlock(&fs_info->reada_lock);
+		btrfs_dev_replace_unlock(&fs_info->dev_replace);
 		goto error;
 	}
 	if (ret) {
 		spin_unlock(&fs_info->reada_lock);
+		btrfs_dev_replace_unlock(&fs_info->dev_replace);
 		goto error;
 	}
 	prev_dev = NULL;
+	dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(
+			&fs_info->dev_replace);
 	for (i = 0; i < nzones; ++i) {
 		dev = bbio->stripes[i].dev;
 		if (dev == prev_dev) {
···
 			 */
 			continue;
 		}
+		if (!dev->bdev) {
+			/* cannot read ahead on missing device */
+			continue;
+		}
+		if (dev_replace_is_ongoing &&
+		    dev == fs_info->dev_replace.tgtdev) {
+			/*
+			 * as this device is selected for reading only as
+			 * a last resort, skip it for read ahead.
+			 */
+			continue;
+		}
 		prev_dev = dev;
 		ret = radix_tree_insert(&dev->reada_extents, index, re);
 		if (ret) {
 			while (--i >= 0) {
 				dev = bbio->stripes[i].dev;
 				BUG_ON(dev == NULL);
+				/* ignore whether the entry was inserted */
 				radix_tree_delete(&dev->reada_extents, index);
 			}
 			BUG_ON(fs_info == NULL);
 			radix_tree_delete(&fs_info->reada_tree, index);
 			spin_unlock(&fs_info->reada_lock);
+			btrfs_dev_replace_unlock(&fs_info->dev_replace);
 			goto error;
 		}
 	}
 	spin_unlock(&fs_info->reada_lock);
+	btrfs_dev_replace_unlock(&fs_info->dev_replace);
 
 	kfree(bbio);
 	return re;
···
 	generation = btrfs_header_generation(node);
 	free_extent_buffer(node);
 
-	reada_add_block(rc, start, &max_key, level, generation);
+	if (reada_add_block(rc, start, &max_key, level, generation)) {
+		kfree(rc);
+		return ERR_PTR(-ENOMEM);
+	}
 
 	reada_start_machine(root->fs_info);
 

fs/btrfs/relocation.c

···
 	struct btrfs_root_item *root_item;
 	struct btrfs_path *path;
 	struct extent_buffer *leaf;
-	unsigned long nr;
 	int level;
 	int max_level;
 	int replaced = 0;
···
 		BUG_ON(IS_ERR(trans));
 		trans->block_rsv = rc->block_rsv;
 
-		ret = btrfs_block_rsv_refill(root, rc->block_rsv, min_reserved);
+		ret = btrfs_block_rsv_refill(root, rc->block_rsv, min_reserved,
+					     BTRFS_RESERVE_FLUSH_ALL);
 		if (ret) {
 			BUG_ON(ret != -EAGAIN);
 			ret = btrfs_commit_transaction(trans, root);
···
 			       path->slots[level]);
 		root_item->drop_level = level;
 
-		nr = trans->blocks_used;
 		btrfs_end_transaction_throttle(trans, root);
 
-		btrfs_btree_balance_dirty(root, nr);
+		btrfs_btree_balance_dirty(root);
 
 		if (replaced && rc->stage == UPDATE_DATA_PTRS)
 			invalidate_extent_cache(root, &key, &next_key);
···
 		btrfs_update_reloc_root(trans, root);
 	}
 
-	nr = trans->blocks_used;
 	btrfs_end_transaction_throttle(trans, root);
 
-	btrfs_btree_balance_dirty(root, nr);
+	btrfs_btree_balance_dirty(root);
 
 	if (replaced && rc->stage == UPDATE_DATA_PTRS)
 		invalidate_extent_cache(root, &key, &next_key);
···
 again:
 	if (!err) {
 		num_bytes = rc->merging_rsv_size;
-		ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes);
+		ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes,
+					  BTRFS_RESERVE_FLUSH_ALL);
 		if (ret)
 			err = ret;
 	}
···
 	num_bytes = calcu_metadata_size(rc, node, 1) * 2;
 
 	trans->block_rsv = rc->block_rsv;
-	ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes);
+	ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes,
+				  BTRFS_RESERVE_FLUSH_ALL);
 	if (ret) {
 		if (ret == -EAGAIN)
 			rc->commit_transaction = 1;
···
 	struct btrfs_path *path;
 	struct btrfs_root *root = fs_info->tree_root;
 	struct btrfs_trans_handle *trans;
-	unsigned long nr;
 	int ret = 0;
 
 	if (inode)
···
 	ret = btrfs_truncate_free_space_cache(root, trans, path, inode);
 
 	btrfs_free_path(path);
-	nr = trans->blocks_used;
 	btrfs_end_transaction(trans, root);
-	btrfs_btree_balance_dirty(root, nr);
+	btrfs_btree_balance_dirty(root);
 out:
 	iput(inode);
 	return ret;
···
 	 * is no reservation in transaction handle.
 	 */
 	ret = btrfs_block_rsv_add(rc->extent_root, rc->block_rsv,
-				  rc->extent_root->nodesize * 256);
+				  rc->extent_root->nodesize * 256,
+				  BTRFS_RESERVE_FLUSH_ALL);
 	if (ret)
 		return ret;
 
···
 	struct btrfs_trans_handle *trans = NULL;
 	struct btrfs_path *path;
 	struct btrfs_extent_item *ei;
-	unsigned long nr;
 	u64 flags;
 	u32 item_size;
 	int ret;
···
 			ret = btrfs_commit_transaction(trans, rc->extent_root);
 			BUG_ON(ret);
 		} else {
-			nr = trans->blocks_used;
 			btrfs_end_transaction_throttle(trans, rc->extent_root);
-			btrfs_btree_balance_dirty(rc->extent_root, nr);
+			btrfs_btree_balance_dirty(rc->extent_root);
 		}
 		trans = NULL;
 
···
 			  GFP_NOFS);
 
 	if (trans) {
-		nr = trans->blocks_used;
 		btrfs_end_transaction_throttle(trans, rc->extent_root);
-		btrfs_btree_balance_dirty(rc->extent_root, nr);
+		btrfs_btree_balance_dirty(rc->extent_root);
 	}
 
 	if (!err) {
···
 	struct btrfs_trans_handle *trans;
 	struct btrfs_root *root;
 	struct btrfs_key key;
-	unsigned long nr;
 	u64 objectid = BTRFS_FIRST_FREE_OBJECTID;
 	int err = 0;
 
···
 
 	err = btrfs_orphan_add(trans, inode);
 out:
-	nr = trans->blocks_used;
 	btrfs_end_transaction(trans, root);
-	btrfs_btree_balance_dirty(root, nr);
+	btrfs_btree_balance_dirty(root);
 	if (err) {
 		if (inode)
 			iput(inode);
···
 	       (unsigned long long)rc->block_group->key.objectid,
 	       (unsigned long long)rc->block_group->flags);
 
-	btrfs_start_delalloc_inodes(fs_info->tree_root, 0);
+	ret = btrfs_start_delalloc_inodes(fs_info->tree_root, 0);
+	if (ret < 0) {
+		err = ret;
+		goto out;
+	}
 	btrfs_wait_ordered_extents(fs_info->tree_root, 0);
 
 	while (1) {

fs/btrfs/root-tree.c

···
 	struct btrfs_root_item *item = &root->root_item;
 	struct timespec ct = CURRENT_TIME;
 
-	spin_lock(&root->root_times_lock);
+	spin_lock(&root->root_item_lock);
 	item->ctransid = cpu_to_le64(trans->transid);
 	item->ctime.sec = cpu_to_le64(ct.tv_sec);
 	item->ctime.nsec = cpu_to_le32(ct.tv_nsec);
-	spin_unlock(&root->root_times_lock);
+	spin_unlock(&root->root_item_lock);
 }

fs/btrfs/scrub.c

···
 /*
- * Copyright (C) 2011 STRATO.  All rights reserved.
+ * Copyright (C) 2011, 2012 STRATO.  All rights reserved.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public
···
 #include "transaction.h"
 #include "backref.h"
 #include "extent_io.h"
+#include "dev-replace.h"
 #include "check-integrity.h"
 #include "rcu-string.h"
 
···
  */
 
 struct scrub_block;
-struct scrub_dev;
+struct scrub_ctx;
 
-#define SCRUB_PAGES_PER_BIO	16	/* 64k per bio */
-#define SCRUB_BIOS_PER_DEV	16	/* 1 MB per device in flight */
+/*
+ * the following three values only influence the performance.
+ * The last one configures the number of parallel and outstanding I/O
+ * operations. The first two values configure an upper limit for the number
+ * of (dynamically allocated) pages that are added to a bio.
+ */
+#define SCRUB_PAGES_PER_RD_BIO	32	/* 128k per bio */
+#define SCRUB_PAGES_PER_WR_BIO	32	/* 128k per bio */
+#define SCRUB_BIOS_PER_SCTX	64	/* 8MB per device in flight */
+
+/*
+ * the following value times PAGE_SIZE needs to be large enough to match the
+ * largest node/leaf/sector size that shall be supported.
+ * Values larger than BTRFS_STRIPE_LEN are not supported.
+ */
 #define SCRUB_MAX_PAGES_PER_BLOCK	16	/* 64k per node/leaf/sector */
 
 struct scrub_page {
···
 	u64			generation;
 	u64			logical;
 	u64			physical;
+	u64			physical_for_dev_replace;
+	atomic_t		ref_count;
 	struct {
 		unsigned int	mirror_num:8;
 		unsigned int	have_csum:1;
···
 
 struct scrub_bio {
 	int			index;
-	struct scrub_dev	*sdev;
+	struct scrub_ctx	*sctx;
+	struct btrfs_device	*dev;
 	struct bio		*bio;
 	int			err;
 	u64			logical;
 	u64			physical;
-	struct scrub_page	*pagev[SCRUB_PAGES_PER_BIO];
+#if SCRUB_PAGES_PER_WR_BIO >= SCRUB_PAGES_PER_RD_BIO
+	struct scrub_page	*pagev[SCRUB_PAGES_PER_WR_BIO];
+#else
+	struct scrub_page	*pagev[SCRUB_PAGES_PER_RD_BIO];
+#endif
 	int			page_count;
 	int			next_free;
 	struct btrfs_work	work;
 };
 
 struct scrub_block {
-	struct scrub_page	pagev[SCRUB_MAX_PAGES_PER_BLOCK];
+	struct scrub_page	*pagev[SCRUB_MAX_PAGES_PER_BLOCK];
 	int			page_count;
 	atomic_t		outstanding_pages;
 	atomic_t		ref_count; /* free mem on transition to zero */
-	struct scrub_dev	*sdev;
+	struct scrub_ctx	*sctx;
 	struct {
 		unsigned int	header_error:1;
 		unsigned int	checksum_error:1;
···
 	};
 };
 
-struct scrub_dev {
-	struct scrub_bio	*bios[SCRUB_BIOS_PER_DEV];
-	struct btrfs_device	*dev;
+struct scrub_wr_ctx {
+	struct scrub_bio *wr_curr_bio;
+	struct btrfs_device *tgtdev;
+	int pages_per_wr_bio; /* <= SCRUB_PAGES_PER_WR_BIO */
+	atomic_t flush_all_writes;
+	struct mutex wr_lock;
+};
+
+struct scrub_ctx {
+	struct scrub_bio	*bios[SCRUB_BIOS_PER_SCTX];
+	struct btrfs_root	*dev_root;
 	int			first_free;
 	int			curr;
-	atomic_t		in_flight;
-	atomic_t		fixup_cnt;
+	atomic_t		bios_in_flight;
+	atomic_t		workers_pending;
 	spinlock_t		list_lock;
 	wait_queue_head_t	list_wait;
 	u16			csum_size;
 	struct list_head	csum_list;
 	atomic_t		cancel_req;
 	int			readonly;
-	int			pages_per_bio; /* <= SCRUB_PAGES_PER_BIO */
+	int			pages_per_rd_bio;
 	u32			sectorsize;
 	u32			nodesize;
 	u32			leafsize;
+
+	int			is_dev_replace;
+	struct scrub_wr_ctx	wr_ctx;
+
 	/*
 	 * statistics
 	 */
···
 };
 
 struct scrub_fixup_nodatasum {
-	struct scrub_dev	*sdev;
+	struct scrub_ctx	*sctx;
+	struct btrfs_device	*dev;
 	u64			logical;
 	struct btrfs_root	*root;
 	struct btrfs_work	work;
 	int			mirror_num;
+};
+
+struct scrub_copy_nocow_ctx {
+	struct scrub_ctx	*sctx;
+	u64			logical;
+	u64			len;
+	int			mirror_num;
+	u64			physical_for_dev_replace;
+	struct btrfs_work	work;
 };
 
 struct scrub_warning {
···
 };
 
 
+static void scrub_pending_bio_inc(struct scrub_ctx *sctx);
+static void scrub_pending_bio_dec(struct scrub_ctx *sctx);
+static void scrub_pending_trans_workers_inc(struct scrub_ctx *sctx);
+static void scrub_pending_trans_workers_dec(struct scrub_ctx *sctx);
 static int scrub_handle_errored_block(struct scrub_block *sblock_to_check);
-static int scrub_setup_recheck_block(struct scrub_dev *sdev,
-				     struct btrfs_mapping_tree *map_tree,
+static int scrub_setup_recheck_block(struct scrub_ctx *sctx,
+				     struct btrfs_fs_info *fs_info,
+				     struct scrub_block *original_sblock,
 				     u64 length, u64 logical,
-				     struct scrub_block *sblock);
-static int scrub_recheck_block(struct btrfs_fs_info *fs_info,
-			       struct scrub_block *sblock, int is_metadata,
-			       int have_csum, u8 *csum, u64 generation,
-			       u16 csum_size);
+				     struct scrub_block *sblocks_for_recheck);
+static void scrub_recheck_block(struct btrfs_fs_info *fs_info,
+				struct scrub_block *sblock, int is_metadata,
+				int have_csum, u8 *csum, u64 generation,
+				u16 csum_size);
 static void scrub_recheck_block_checksum(struct btrfs_fs_info *fs_info,
 					 struct scrub_block *sblock,
 					 int is_metadata, int have_csum,
···
 static int scrub_repair_page_from_good_copy(struct scrub_block *sblock_bad,
 					    struct scrub_block *sblock_good,
 					    int page_num, int force_write);
+static void scrub_write_block_to_dev_replace(struct scrub_block *sblock);
+static int scrub_write_page_to_dev_replace(struct scrub_block *sblock,
+					   int page_num);
 static int scrub_checksum_data(struct scrub_block *sblock);
 static int scrub_checksum_tree_block(struct scrub_block *sblock);
 static int scrub_checksum_super(struct scrub_block *sblock);
 static void scrub_block_get(struct scrub_block *sblock);
 static void scrub_block_put(struct scrub_block *sblock);
-static int scrub_add_page_to_bio(struct scrub_dev *sdev,
-				 struct scrub_page *spage);
-static int scrub_pages(struct scrub_dev *sdev, u64 logical, u64 len,
-		       u64 physical, u64 flags, u64 gen, int mirror_num,
-		       u8 *csum, int force);
+static void scrub_page_get(struct scrub_page *spage);
+static void scrub_page_put(struct scrub_page *spage);
+static int scrub_add_page_to_rd_bio(struct scrub_ctx *sctx,
+				    struct scrub_page *spage);
+static int scrub_pages(struct scrub_ctx *sctx, u64 logical, u64 len,
+		       u64 physical, struct btrfs_device *dev, u64 flags,
+		       u64 gen, int mirror_num, u8 *csum, int force,
+		       u64 physical_for_dev_replace);
 static void scrub_bio_end_io(struct bio *bio, int err);
 static void scrub_bio_end_io_worker(struct btrfs_work *work);
 static void scrub_block_complete(struct scrub_block *sblock);
+static void scrub_remap_extent(struct btrfs_fs_info *fs_info,
+			       u64 extent_logical, u64 extent_len,
+			       u64 *extent_physical,
+			       struct btrfs_device **extent_dev,
+			       int *extent_mirror_num);
+static int scrub_setup_wr_ctx(struct scrub_ctx *sctx,
+			      struct scrub_wr_ctx *wr_ctx,
+			      struct btrfs_fs_info *fs_info,
+			      struct btrfs_device *dev,
+			      int is_dev_replace);
+static void scrub_free_wr_ctx(struct scrub_wr_ctx *wr_ctx);
+static int scrub_add_page_to_wr_bio(struct scrub_ctx *sctx,
+				    struct scrub_page *spage);
+static void scrub_wr_submit(struct scrub_ctx *sctx);
+static void scrub_wr_bio_end_io(struct bio *bio, int err);
+static void scrub_wr_bio_end_io_worker(struct btrfs_work *work);
+static int write_page_nocow(struct scrub_ctx *sctx,
+			    u64 physical_for_dev_replace, struct page *page);
+static int copy_nocow_pages_for_inode(u64 inum, u64 offset, u64 root,
+				      void *ctx);
+static int copy_nocow_pages(struct scrub_ctx *sctx, u64 logical, u64 len,
+			    int mirror_num, u64 physical_for_dev_replace);
+static void copy_nocow_pages_worker(struct btrfs_work *work);
 
 
-static void scrub_free_csums(struct scrub_dev *sdev)
+static void scrub_pending_bio_inc(struct scrub_ctx *sctx)
 {
-	while (!list_empty(&sdev->csum_list)) {
+	atomic_inc(&sctx->bios_in_flight);
+}
+
+static void scrub_pending_bio_dec(struct scrub_ctx *sctx)
+{
+	atomic_dec(&sctx->bios_in_flight);
+	wake_up(&sctx->list_wait);
+}
+
+/*
+ * used for workers that require transaction commits (i.e., for the
+ * NOCOW case)
+ */
+static void scrub_pending_trans_workers_inc(struct scrub_ctx *sctx)
+{
+	struct btrfs_fs_info *fs_info = sctx->dev_root->fs_info;
+
+	/*
+	 * increment scrubs_running to prevent cancel requests from
+	 * completing as long as a worker is running. we must also
+	 * increment scrubs_paused to prevent deadlocking on pause
+	 * requests used for transactions commits (as the worker uses a
+	 * transaction context). it is safe to regard the worker
+	 * as paused for all matters practical. effectively, we only
+	 * avoid cancellation requests from completing.
+	 */
+	mutex_lock(&fs_info->scrub_lock);
+	atomic_inc(&fs_info->scrubs_running);
+	atomic_inc(&fs_info->scrubs_paused);
+	mutex_unlock(&fs_info->scrub_lock);
+	atomic_inc(&sctx->workers_pending);
+}
+
+/* used for workers that require transaction commits */
+static void scrub_pending_trans_workers_dec(struct scrub_ctx *sctx)
+{
+	struct btrfs_fs_info *fs_info = sctx->dev_root->fs_info;
+
+	/*
+	 * see scrub_pending_trans_workers_inc() why we're pretending
+	 * to be paused in the scrub counters
+	 */
+	mutex_lock(&fs_info->scrub_lock);
+	atomic_dec(&fs_info->scrubs_running);
+	atomic_dec(&fs_info->scrubs_paused);
+	mutex_unlock(&fs_info->scrub_lock);
+	atomic_dec(&sctx->workers_pending);
+	wake_up(&fs_info->scrub_pause_wait);
+	wake_up(&sctx->list_wait);
+}
+
+static void scrub_free_csums(struct scrub_ctx *sctx)
+{
+	while (!list_empty(&sctx->csum_list)) {
 		struct btrfs_ordered_sum *sum;
-		sum = list_first_entry(&sdev->csum_list,
+		sum = list_first_entry(&sctx->csum_list,
 				       struct btrfs_ordered_sum, list);
 		list_del(&sum->list);
 		kfree(sum);
 	}
 }
 
-static noinline_for_stack void scrub_free_dev(struct scrub_dev *sdev)
+static noinline_for_stack void scrub_free_ctx(struct scrub_ctx *sctx)
 {
 	int i;
 
-	if (!sdev)
+	if (!sctx)
 		return;
 
+	scrub_free_wr_ctx(&sctx->wr_ctx);
+
 	/* this can happen when scrub is cancelled */
-	if (sdev->curr != -1) {
-		struct scrub_bio *sbio = sdev->bios[sdev->curr];
+	if (sctx->curr != -1) {
+		struct scrub_bio *sbio = sctx->bios[sctx->curr];
 
 		for (i = 0; i < sbio->page_count; i++) {
-			BUG_ON(!sbio->pagev[i]);
-			BUG_ON(!sbio->pagev[i]->page);
+			WARN_ON(!sbio->pagev[i]->page);
 			scrub_block_put(sbio->pagev[i]->sblock);
 		}
 		bio_put(sbio->bio);
 	}
 
-	for (i = 0; i < SCRUB_BIOS_PER_DEV; ++i) {
-		struct scrub_bio *sbio = sdev->bios[i];
+	for (i = 0; i < SCRUB_BIOS_PER_SCTX; ++i) {
+		struct scrub_bio *sbio = sctx->bios[i];
 
 		if (!sbio)
 			break;
 		kfree(sbio);
 	}
 
-	scrub_free_csums(sdev);
-	kfree(sdev);
+	scrub_free_csums(sctx);
+	kfree(sctx);
 }
 
 static noinline_for_stack
-struct scrub_dev *scrub_setup_dev(struct btrfs_device *dev)
+struct scrub_ctx *scrub_setup_ctx(struct btrfs_device *dev, int is_dev_replace)
 {
-	struct scrub_dev *sdev;
+	struct scrub_ctx *sctx;
 	int		i;
 	struct btrfs_fs_info *fs_info = dev->dev_root->fs_info;
-	int pages_per_bio;
+	int pages_per_rd_bio;
+	int ret;
 
-	pages_per_bio = min_t(int, SCRUB_PAGES_PER_BIO,
-			      bio_get_nr_vecs(dev->bdev));
-	sdev = kzalloc(sizeof(*sdev), GFP_NOFS);
-	if (!sdev)
+	/*
+	 * the setting of pages_per_rd_bio is correct for scrub but might
+	 * be wrong for the dev_replace code where we might read from
+	 * different devices in the initial huge bios. However, that
+	 * code is able to correctly handle the case when adding a page
+	 * to a bio fails.
+	 */
+	if (dev->bdev)
+		pages_per_rd_bio = min_t(int, SCRUB_PAGES_PER_RD_BIO,
+					 bio_get_nr_vecs(dev->bdev));
+	else
+		pages_per_rd_bio = SCRUB_PAGES_PER_RD_BIO;
+	sctx = kzalloc(sizeof(*sctx), GFP_NOFS);
+	if (!sctx)
 		goto nomem;
-	sdev->dev = dev;
-	sdev->pages_per_bio = pages_per_bio;
-	sdev->curr = -1;
-	for (i = 0; i < SCRUB_BIOS_PER_DEV; ++i) {
+	sctx->is_dev_replace = is_dev_replace;
+	sctx->pages_per_rd_bio = pages_per_rd_bio;
+	sctx->curr = -1;
+	sctx->dev_root = dev->dev_root;
+	for (i = 0; i < SCRUB_BIOS_PER_SCTX; ++i) {
 		struct scrub_bio *sbio;
 
 		sbio = kzalloc(sizeof(*sbio), GFP_NOFS);
 		if (!sbio)
 			goto nomem;
-		sdev->bios[i] = sbio;
+		sctx->bios[i] = sbio;
 
 		sbio->index = i;
-		sbio->sdev = sdev;
+		sbio->sctx = sctx;
 		sbio->page_count = 0;
 		sbio->work.func = scrub_bio_end_io_worker;
 
-		if (i != SCRUB_BIOS_PER_DEV-1)
-			sdev->bios[i]->next_free = i + 1;
+		if (i != SCRUB_BIOS_PER_SCTX - 1)
+			sctx->bios[i]->next_free = i + 1;
 		else
-			sdev->bios[i]->next_free = -1;
+			sctx->bios[i]->next_free = -1;
 	}
-	sdev->first_free = 0;
-	sdev->nodesize = dev->dev_root->nodesize;
-	sdev->leafsize = dev->dev_root->leafsize;
-	sdev->sectorsize = dev->dev_root->sectorsize;
-	atomic_set(&sdev->in_flight, 0);
-	atomic_set(&sdev->fixup_cnt, 0);
-	atomic_set(&sdev->cancel_req, 0);
-	sdev->csum_size = btrfs_super_csum_size(fs_info->super_copy);
-	INIT_LIST_HEAD(&sdev->csum_list);
+	sctx->first_free = 0;
+	sctx->nodesize = dev->dev_root->nodesize;
+	sctx->leafsize = dev->dev_root->leafsize;
+	sctx->sectorsize = dev->dev_root->sectorsize;
+	atomic_set(&sctx->bios_in_flight, 0);
+	atomic_set(&sctx->workers_pending, 0);
+	atomic_set(&sctx->cancel_req, 0);
+	sctx->csum_size = btrfs_super_csum_size(fs_info->super_copy);
+	INIT_LIST_HEAD(&sctx->csum_list);
 
-	spin_lock_init(&sdev->list_lock);
-	spin_lock_init(&sdev->stat_lock);
-	init_waitqueue_head(&sdev->list_wait);
-	return sdev;
+	spin_lock_init(&sctx->list_lock);
+	spin_lock_init(&sctx->stat_lock);
+	init_waitqueue_head(&sctx->list_wait);
+
+	ret = scrub_setup_wr_ctx(sctx, &sctx->wr_ctx, fs_info,
+				 fs_info->dev_replace.tgtdev, is_dev_replace);
+	if (ret) {
+		scrub_free_ctx(sctx);
+		return ERR_PTR(ret);
+	}
+	return sctx;
 
 nomem:
-	scrub_free_dev(sdev);
+	scrub_free_ctx(sctx);
 	return ERR_PTR(-ENOMEM);
 }
 
-static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root, void *ctx)
+static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
+				     void *warn_ctx)
 {
 	u64 isize;
 	u32 nlink;
···
 	int i;
 	struct extent_buffer *eb;
 	struct btrfs_inode_item *inode_item;
-	struct scrub_warning *swarn = ctx;
+	struct scrub_warning *swarn = warn_ctx;
 	struct btrfs_fs_info *fs_info = swarn->dev->dev_root->fs_info;
 	struct inode_fs_paths *ipath = NULL;
 	struct btrfs_root *local_root;
···
 
 static void scrub_print_warning(const char *errstr, struct scrub_block *sblock)
 {
-	struct btrfs_device *dev = sblock->sdev->dev;
-	struct btrfs_fs_info *fs_info = dev->dev_root->fs_info;
+	struct btrfs_device *dev;
+	struct btrfs_fs_info *fs_info;
 	struct btrfs_path *path;
 	struct btrfs_key found_key;
 	struct extent_buffer *eb;
···
 	const int bufsize = 4096;
 	int ret;
 
+	WARN_ON(sblock->page_count < 1);
+	dev = sblock->pagev[0]->dev;
+	fs_info = sblock->sctx->dev_root->fs_info;
+
 	path = btrfs_alloc_path();
 
 	swarn.scratch_buf = kmalloc(bufsize, GFP_NOFS);
 	swarn.msg_buf = kmalloc(bufsize, GFP_NOFS);
-	BUG_ON(sblock->page_count < 1);
-	swarn.sector = (sblock->pagev[0].physical) >> 9;
-	swarn.logical = sblock->pagev[0].logical;
+	swarn.sector = (sblock->pagev[0]->physical) >> 9;
+	swarn.logical = sblock->pagev[0]->logical;
 	swarn.errstr = errstr;
-	swarn.dev = dev;
+	swarn.dev = NULL;
 	swarn.msg_bufsize = bufsize;
 	swarn.scratch_bufsize = bufsize;
 
···
 		} while (ret != 1);
 	} else {
 		swarn.path = path;
+		swarn.dev = dev;
 		iterate_extent_inodes(fs_info, found_key.objectid,
 					extent_item_pos, 1,
 					scrub_print_warning_inode, &swarn);
···
 	kfree(swarn.msg_buf);
 }
 
-static int scrub_fixup_readpage(u64 inum, u64 offset, u64 root, void *ctx)
+static int scrub_fixup_readpage(u64 inum, u64 offset, u64 root, void *fixup_ctx)
 {
 	struct page *page = NULL;
 	unsigned long index;
-	struct scrub_fixup_nodatasum *fixup = ctx;
+	struct scrub_fixup_nodatasum *fixup = fixup_ctx;
 	int ret;
 	int corrected = 0;
 	struct btrfs_key key;
···
 	}
 
 	if (PageUptodate(page)) {
-		struct btrfs_mapping_tree *map_tree;
+		struct btrfs_fs_info *fs_info;
 		if (PageDirty(page)) {
 			/*
 			 * we need to write the data to the defect sector. the
···
 			ret = -EIO;
 			goto out;
 		}
-		map_tree = &BTRFS_I(inode)->root->fs_info->mapping_tree;
-		ret = repair_io_failure(map_tree, offset, PAGE_SIZE,
+		fs_info = BTRFS_I(inode)->root->fs_info;
+		ret = repair_io_failure(fs_info, offset, PAGE_SIZE,
 					fixup->logical, page,
 					fixup->mirror_num);
 		unlock_page(page);
···
 {
 	int ret;
 	struct scrub_fixup_nodatasum *fixup;
-	struct scrub_dev *sdev;
+	struct scrub_ctx *sctx;
 	struct btrfs_trans_handle *trans = NULL;
 	struct btrfs_fs_info *fs_info;
 	struct btrfs_path *path;
 	int uncorrectable = 0;
 
 	fixup = container_of(work, struct scrub_fixup_nodatasum, work);
-	sdev = fixup->sdev;
+	sctx = fixup->sctx;
 	fs_info = fixup->root->fs_info;
 
 	path = btrfs_alloc_path();
 	if (!path) {
-		spin_lock(&sdev->stat_lock);
-		++sdev->stat.malloc_errors;
-		spin_unlock(&sdev->stat_lock);
+		spin_lock(&sctx->stat_lock);
+		++sctx->stat.malloc_errors;
+		spin_unlock(&sctx->stat_lock);
 		uncorrectable = 1;
 		goto out;
 	}
···
 	}
 	WARN_ON(ret != 1);
 
-	spin_lock(&sdev->stat_lock);
-	++sdev->stat.corrected_errors;
-	spin_unlock(&sdev->stat_lock);
+	spin_lock(&sctx->stat_lock);
+	++sctx->stat.corrected_errors;
+	spin_unlock(&sctx->stat_lock);
 
 out:
 	if (trans && !IS_ERR(trans))
 		btrfs_end_transaction(trans, fixup->root);
 	if (uncorrectable) {
-		spin_lock(&sdev->stat_lock);
-		++sdev->stat.uncorrectable_errors;
-		spin_unlock(&sdev->stat_lock);
-
+		spin_lock(&sctx->stat_lock);
+		++sctx->stat.uncorrectable_errors;
+		spin_unlock(&sctx->stat_lock);
+		btrfs_dev_replace_stats_inc(
+			&sctx->dev_root->fs_info->dev_replace.
+			num_uncorrectable_read_errors);
 		printk_ratelimited_in_rcu(KERN_ERR
 			"btrfs: unable to fixup (nodatasum) error at logical %llu on dev %s\n",
 			(unsigned long long)fixup->logical,
-			rcu_str_deref(sdev->dev->name));
+			rcu_str_deref(fixup->dev->name));
 	}
 
 	btrfs_free_path(path);
 	kfree(fixup);
 
-	/* see caller why we're pretending to be paused in the scrub counters */
-	mutex_lock(&fs_info->scrub_lock);
-	atomic_dec(&fs_info->scrubs_running);
-	atomic_dec(&fs_info->scrubs_paused);
-	mutex_unlock(&fs_info->scrub_lock);
-	atomic_dec(&sdev->fixup_cnt);
-	wake_up(&fs_info->scrub_pause_wait);
-	wake_up(&sdev->list_wait);
+	scrub_pending_trans_workers_dec(sctx);
 }
 
 /*
···
  */
 static int scrub_handle_errored_block(struct scrub_block *sblock_to_check)
 {
-	struct scrub_dev *sdev = sblock_to_check->sdev;
+	struct scrub_ctx *sctx = sblock_to_check->sctx;
+	struct btrfs_device *dev;
 	struct btrfs_fs_info *fs_info;
 	u64 length;
 	u64 logical;
···
 				      DEFAULT_RATELIMIT_BURST);
 
 	BUG_ON(sblock_to_check->page_count < 1);
-	fs_info = sdev->dev->dev_root->fs_info;
+	fs_info = sctx->dev_root->fs_info;
+	if (sblock_to_check->pagev[0]->flags & BTRFS_EXTENT_FLAG_SUPER) {
+		/*
+		 * if we find an error in a super block, we just report it.
+		 * They will get written with the next transaction commit
+		 * anyway
+		 */
+		spin_lock(&sctx->stat_lock);
+		++sctx->stat.super_errors;
+		spin_unlock(&sctx->stat_lock);
+		return 0;
+	}
 	length = sblock_to_check->page_count * PAGE_SIZE;
-	logical = sblock_to_check->pagev[0].logical;
-	generation = sblock_to_check->pagev[0].generation;
-	BUG_ON(sblock_to_check->pagev[0].mirror_num < 1);
-	failed_mirror_index = sblock_to_check->pagev[0].mirror_num - 1;
-	is_metadata = !(sblock_to_check->pagev[0].flags &
+	logical = sblock_to_check->pagev[0]->logical;
+	generation = sblock_to_check->pagev[0]->generation;
+	BUG_ON(sblock_to_check->pagev[0]->mirror_num < 1);
+	failed_mirror_index = sblock_to_check->pagev[0]->mirror_num - 1;
+	is_metadata = !(sblock_to_check->pagev[0]->flags &
 			BTRFS_EXTENT_FLAG_DATA);
-	have_csum = sblock_to_check->pagev[0].have_csum;
-	csum = sblock_to_check->pagev[0].csum;
+	have_csum = sblock_to_check->pagev[0]->have_csum;
+	csum = sblock_to_check->pagev[0]->csum;
+	dev = sblock_to_check->pagev[0]->dev;
+
+	if (sctx->is_dev_replace && !is_metadata && !have_csum) {
+		sblocks_for_recheck = NULL;
+		goto nodatasum_case;
+	}
 
 	/*
 	 * read all mirrors one after the other. This includes to
···
 				     sizeof(*sblocks_for_recheck),
 				     GFP_NOFS);
 	if (!sblocks_for_recheck) {
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.malloc_errors++;
-		sdev->stat.read_errors++;
-		sdev->stat.uncorrectable_errors++;
-		spin_unlock(&sdev->stat_lock);
-		btrfs_dev_stat_inc_and_print(sdev->dev,
-					     BTRFS_DEV_STAT_READ_ERRS);
+		spin_lock(&sctx->stat_lock);
+		sctx->stat.malloc_errors++;
+		sctx->stat.read_errors++;
+		sctx->stat.uncorrectable_errors++;
+		spin_unlock(&sctx->stat_lock);
+		btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_READ_ERRS);
 		goto out;
 	}
 
 	/* setup the context, map the logical blocks and alloc the pages */
-	ret = scrub_setup_recheck_block(sdev, &fs_info->mapping_tree, length,
+	ret = scrub_setup_recheck_block(sctx, fs_info, sblock_to_check, length,
 					logical, sblocks_for_recheck);
 	if (ret) {
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.read_errors++;
-		sdev->stat.uncorrectable_errors++;
-		spin_unlock(&sdev->stat_lock);
-		btrfs_dev_stat_inc_and_print(sdev->dev,
-					     BTRFS_DEV_STAT_READ_ERRS);
+		spin_lock(&sctx->stat_lock);
+		sctx->stat.read_errors++;
+		sctx->stat.uncorrectable_errors++;
+		spin_unlock(&sctx->stat_lock);
+		btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_READ_ERRS);
 		goto out;
 	}
 	BUG_ON(failed_mirror_index >= BTRFS_MAX_MIRRORS);
 	sblock_bad = sblocks_for_recheck + failed_mirror_index;
 
 	/* build and submit the bios for the failed mirror, check checksums */
-	ret = scrub_recheck_block(fs_info, sblock_bad, is_metadata, have_csum,
-				  csum, generation, sdev->csum_size);
-	if (ret) {
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.read_errors++;
-		sdev->stat.uncorrectable_errors++;
-		spin_unlock(&sdev->stat_lock);
-		btrfs_dev_stat_inc_and_print(sdev->dev,
-					     BTRFS_DEV_STAT_READ_ERRS);
-		goto out;
-	}
+	scrub_recheck_block(fs_info, sblock_bad, is_metadata, have_csum,
+			    csum, generation, sctx->csum_size);
 
 	if (!sblock_bad->header_error && !sblock_bad->checksum_error &&
 	    sblock_bad->no_io_error_seen) {
···
 		 * different bio (usually one of the two latter cases is
 		 * the cause)
 		 */
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.unverified_errors++;
-		spin_unlock(&sdev->stat_lock);
+		spin_lock(&sctx->stat_lock);
+		sctx->stat.unverified_errors++;
+		spin_unlock(&sctx->stat_lock);
 
+		if (sctx->is_dev_replace)
+			scrub_write_block_to_dev_replace(sblock_bad);
 		goto out;
 	}
 
 	if (!sblock_bad->no_io_error_seen) {
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.read_errors++;
-		spin_unlock(&sdev->stat_lock);
+		spin_lock(&sctx->stat_lock);
+		sctx->stat.read_errors++;
+		spin_unlock(&sctx->stat_lock);
 		if (__ratelimit(&_rs))
 			scrub_print_warning("i/o error", sblock_to_check);
-		btrfs_dev_stat_inc_and_print(sdev->dev,
-					     BTRFS_DEV_STAT_READ_ERRS);
+		btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_READ_ERRS);
 	} else if (sblock_bad->checksum_error) {
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.csum_errors++;
-		spin_unlock(&sdev->stat_lock);
+		spin_lock(&sctx->stat_lock);
+		sctx->stat.csum_errors++;
+		spin_unlock(&sctx->stat_lock);
 		if (__ratelimit(&_rs))
 			scrub_print_warning("checksum error", sblock_to_check);
-		btrfs_dev_stat_inc_and_print(sdev->dev,
+		btrfs_dev_stat_inc_and_print(dev,
 					     BTRFS_DEV_STAT_CORRUPTION_ERRS);
 	} else if (sblock_bad->header_error) {
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.verify_errors++;
-		spin_unlock(&sdev->stat_lock);
+		spin_lock(&sctx->stat_lock);
+		sctx->stat.verify_errors++;
+		spin_unlock(&sctx->stat_lock);
 		if (__ratelimit(&_rs))
 			scrub_print_warning("checksum/header error",
 					    sblock_to_check);
 		if (sblock_bad->generation_error)
-			btrfs_dev_stat_inc_and_print(sdev->dev,
+			btrfs_dev_stat_inc_and_print(dev,
 				BTRFS_DEV_STAT_GENERATION_ERRS);
 		else
-			btrfs_dev_stat_inc_and_print(sdev->dev,
+			btrfs_dev_stat_inc_and_print(dev,
 				BTRFS_DEV_STAT_CORRUPTION_ERRS);
 	}
 
-	if (sdev->readonly)
+	if (sctx->readonly && !sctx->is_dev_replace)
 		goto did_not_correct_error;
 
 	if (!is_metadata && !have_csum) {
 		struct scrub_fixup_nodatasum *fixup_nodatasum;
+
+nodatasum_case:
+		WARN_ON(sctx->is_dev_replace);
 
 		/*
 		 * !is_metadata and !have_csum, this means that the data
···
 		fixup_nodatasum = kzalloc(sizeof(*fixup_nodatasum), GFP_NOFS);
 		if (!fixup_nodatasum)
 			goto did_not_correct_error;
-		fixup_nodatasum->sdev = sdev;
+		fixup_nodatasum->sctx = sctx;
+		fixup_nodatasum->dev = dev;
 		fixup_nodatasum->logical = logical;
 		fixup_nodatasum->root = fs_info->extent_root;
 		fixup_nodatasum->mirror_num = failed_mirror_index + 1;
-		/*
-		 * increment scrubs_running to prevent cancel requests from
-		 * completing as long as a fixup worker is running. we must also
-		 * increment scrubs_paused to prevent deadlocking on pause
-		 * requests used for transactions commits (as the worker uses a
-		 * transaction context). it is safe to regard the fixup worker
-		 * as paused for all matters practical. effectively, we only
-		 * avoid cancellation requests from completing.
-		 */
-		mutex_lock(&fs_info->scrub_lock);
-		atomic_inc(&fs_info->scrubs_running);
-		atomic_inc(&fs_info->scrubs_paused);
-		mutex_unlock(&fs_info->scrub_lock);
-		atomic_inc(&sdev->fixup_cnt);
+		scrub_pending_trans_workers_inc(sctx);
 		fixup_nodatasum->work.func = scrub_fixup_nodatasum;
 		btrfs_queue_worker(&fs_info->scrub_workers,
 				   &fixup_nodatasum->work);
···
 
 	/*
 	 * now build and submit the bios for the other mirrors, check
-	 * checksums
-	 */
-	for (mirror_index = 0;
-	     mirror_index < BTRFS_MAX_MIRRORS &&
-	     sblocks_for_recheck[mirror_index].page_count > 0;
-	     mirror_index++) {
-		if (mirror_index == failed_mirror_index)
-			continue;
-
-		/* build and submit the bios, check checksums */
-		ret = scrub_recheck_block(fs_info,
-					  sblocks_for_recheck + mirror_index,
-					  is_metadata, have_csum, csum,
-					  generation, sdev->csum_size);
-		if (ret)
-			goto did_not_correct_error;
-	}
-
-	/*
-	 * first try to pick the mirror which is completely without I/O
+	 * checksums.
+	 * First try to pick the mirror which is completely without I/O
 	 * errors and also does not have a checksum error.
 	 * If one is found, and if a checksum is present, the full block
 	 * that is known to contain an error is rewritten. Afterwards
···
 	     mirror_index < BTRFS_MAX_MIRRORS &&
 	     sblocks_for_recheck[mirror_index].page_count > 0;
 	     mirror_index++) {
-		struct scrub_block *sblock_other = sblocks_for_recheck +
-						   mirror_index;
+		struct scrub_block *sblock_other;
+
+		if (mirror_index == failed_mirror_index)
+			continue;
+		sblock_other = sblocks_for_recheck + mirror_index;
+
+		/* build and submit the bios, check checksums */
+		scrub_recheck_block(fs_info, sblock_other, is_metadata,
+				    have_csum, csum, generation,
+				    sctx->csum_size);
 
 		if (!sblock_other->header_error &&
 		    !sblock_other->checksum_error &&
 		    sblock_other->no_io_error_seen) {
-			int force_write = is_metadata || have_csum;
+			if (sctx->is_dev_replace) {
+				scrub_write_block_to_dev_replace(sblock_other);
+			} else {
+				int force_write = is_metadata || have_csum;
 
-			ret = scrub_repair_block_from_good_copy(sblock_bad,
-								sblock_other,
-								force_write);
+				ret = scrub_repair_block_from_good_copy(
+						sblock_bad, sblock_other,
+						force_write);
+			}
 			if (0 == ret)
 				goto corrected_error;
 		}
 	}
 
 	/*
-	 * in case of I/O errors in the area that is supposed to be
+	 * for dev_replace, pick good pages and write to the target device.
+	 */
+	if (sctx->is_dev_replace) {
+		success = 1;
+		for (page_num = 0; page_num < sblock_bad->page_count;
+		     page_num++) {
+			int sub_success;
+
+			sub_success = 0;
+			for (mirror_index = 0;
+			     mirror_index < BTRFS_MAX_MIRRORS &&
+			     sblocks_for_recheck[mirror_index].page_count > 0;
+			     mirror_index++) {
+				struct scrub_block *sblock_other =
+					sblocks_for_recheck + mirror_index;
+				struct scrub_page *page_other =
+					sblock_other->pagev[page_num];
+
+				if (!page_other->io_error) {
+					ret = scrub_write_page_to_dev_replace(
+							sblock_other, page_num);
+					if (ret == 0) {
+						/* succeeded for this page */
+						sub_success = 1;
+						break;
+					} else {
+						btrfs_dev_replace_stats_inc(
+							&sctx->dev_root->
+							fs_info->dev_replace.
+							num_write_errors);
+					}
+				}
+			}
+
+			if (!sub_success) {
+				/*
+				 * did not find a mirror to fetch the page
+				 * from. scrub_write_page_to_dev_replace()
+				 * handles this case (page->io_error), by
+				 * filling the block with zeros before
+				 * submitting the write request
+				 */
+				success = 0;
+				ret = scrub_write_page_to_dev_replace(
+						sblock_bad, page_num);
+				if (ret)
+					btrfs_dev_replace_stats_inc(
+						&sctx->dev_root->fs_info->
+						dev_replace.num_write_errors);
+			}
+		}
+
+		goto out;
+	}
+
+	/*
+	 * for regular scrub, repair those pages that are errored.
+	 * In case of I/O errors in the area that is supposed to be
 	 * repaired, continue by picking good copies of those pages.
 	 * Select the good pages from mirrors to rewrite bad pages from
 	 * the area to fix. Afterwards verify the checksum of the block
···
 
 	success = 1;
 	for (page_num = 0; page_num < sblock_bad->page_count; page_num++) {
-		struct scrub_page *page_bad = sblock_bad->pagev + page_num;
+		struct scrub_page *page_bad = sblock_bad->pagev[page_num];
 
 		if (!page_bad->io_error)
 			continue;
···
 		     mirror_index++) {
 			struct scrub_block *sblock_other = sblocks_for_recheck +
 							   mirror_index;
-			struct scrub_page *page_other = sblock_other->pagev +
-							page_num;
+			struct scrub_page *page_other = sblock_other->pagev[
+							page_num];
 
 			if (!page_other->io_error) {
 				ret = scrub_repair_page_from_good_copy(
···
 			 * is verified, but most likely the data comes out
 			 * of the page cache.
 			 */
-			ret = scrub_recheck_block(fs_info, sblock_bad,
-						  is_metadata, have_csum, csum,
-						  generation, sdev->csum_size);
-			if (!ret && !sblock_bad->header_error &&
+			scrub_recheck_block(fs_info, sblock_bad,
+					    is_metadata, have_csum, csum,
+					    generation, sctx->csum_size);
+			if (!sblock_bad->header_error &&
 			    !sblock_bad->checksum_error &&
 			    sblock_bad->no_io_error_seen)
 				goto corrected_error;
···
 				goto did_not_correct_error;
 		} else {
 corrected_error:
-			spin_lock(&sdev->stat_lock);
-			sdev->stat.corrected_errors++;
-			spin_unlock(&sdev->stat_lock);
+			spin_lock(&sctx->stat_lock);
+			sctx->stat.corrected_errors++;
+			spin_unlock(&sctx->stat_lock);
 			printk_ratelimited_in_rcu(KERN_ERR
 				"btrfs: fixed up error at logical %llu on dev %s\n",
 				(unsigned long long)logical,
-				rcu_str_deref(sdev->dev->name));
+				rcu_str_deref(dev->name));
 		}
 	} else {
 did_not_correct_error:
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.uncorrectable_errors++;
-		spin_unlock(&sdev->stat_lock);
+		spin_lock(&sctx->stat_lock);
+		sctx->stat.uncorrectable_errors++;
+		spin_unlock(&sctx->stat_lock);
 		printk_ratelimited_in_rcu(KERN_ERR
 			"btrfs: unable to fixup (regular) error at logical %llu on dev %s\n",
 			(unsigned long long)logical,
-			rcu_str_deref(sdev->dev->name));
+			rcu_str_deref(dev->name));
 	}
 
 out:
···
 						     mirror_index;
 			int page_index;
 
-			for (page_index = 0; page_index < SCRUB_PAGES_PER_BIO;
-			     page_index++)
-				if (sblock->pagev[page_index].page)
-					__free_page(
-						sblock->pagev[page_index].page);
+			for (page_index = 0; page_index < sblock->page_count;
+			     page_index++) {
+				sblock->pagev[page_index]->sblock = NULL;
+				scrub_page_put(sblock->pagev[page_index]);
+			}
 		}
 		kfree(sblocks_for_recheck);
 	}
···
 	return 0;
 }
 
-static int scrub_setup_recheck_block(struct scrub_dev *sdev,
-				     struct btrfs_mapping_tree *map_tree,
+static int scrub_setup_recheck_block(struct scrub_ctx *sctx,
+				     struct btrfs_fs_info *fs_info,
+				     struct scrub_block *original_sblock,
 				     u64 length, u64 logical,
 				     struct scrub_block *sblocks_for_recheck)
 {
···
 	int ret;
 
 	/*
-	 * note: the three members sdev, ref_count and outstanding_pages
+	 * note: the two members ref_count and outstanding_pages
 	 * are not used (and not set) in the blocks that are used for
 	 * the recheck procedure
 	 */
···
 		 * with a length of PAGE_SIZE, each returned stripe
 		 * represents one mirror
 		 */
-		ret = btrfs_map_block(map_tree, WRITE, logical, &mapped_length,
-				      &bbio, 0);
+		ret = btrfs_map_block(fs_info, REQ_GET_READ_MIRRORS, logical,
+				      &mapped_length, &bbio, 0);
 		if (ret || !bbio || mapped_length < sublen) {
 			kfree(bbio);
 			return -EIO;
 		}
 
-		BUG_ON(page_index >= SCRUB_PAGES_PER_BIO);
+		BUG_ON(page_index >= SCRUB_PAGES_PER_RD_BIO);
 		for (mirror_index = 0; mirror_index < (int)bbio->num_stripes;
 		     mirror_index++) {
 			struct scrub_block *sblock;
···
 				continue;
 
 			sblock = sblocks_for_recheck + mirror_index;
-			page = sblock->pagev + page_index;
-			page->logical = logical;
-			page->physical = bbio->stripes[mirror_index].physical;
-			/* for missing devices, dev->bdev is NULL */
-			page->dev = bbio->stripes[mirror_index].dev;
-			page->mirror_num = mirror_index + 1;
-			page->page = alloc_page(GFP_NOFS);
-			if (!page->page) {
-				spin_lock(&sdev->stat_lock);
-				sdev->stat.malloc_errors++;
-				spin_unlock(&sdev->stat_lock);
+			sblock->sctx = sctx;
+			page = kzalloc(sizeof(*page), GFP_NOFS);
+			if (!page) {
+leave_nomem:
+				spin_lock(&sctx->stat_lock);
+				sctx->stat.malloc_errors++;
+				spin_unlock(&sctx->stat_lock);
 				kfree(bbio);
 				return -ENOMEM;
 			}
+			scrub_page_get(page);
+			sblock->pagev[page_index] = page;
+			page->logical = logical;
+			page->physical = bbio->stripes[mirror_index].physical;
+			BUG_ON(page_index >= original_sblock->page_count);
+			page->physical_for_dev_replace =
+				original_sblock->pagev[page_index]->
+				physical_for_dev_replace;
+			/* for missing devices, dev->bdev is NULL */
+			page->dev = bbio->stripes[mirror_index].dev;
+			page->mirror_num = mirror_index + 1;
 			sblock->page_count++;
+			page->page = alloc_page(GFP_NOFS);
+			if (!page->page)
+				goto leave_nomem;
 		}
 		kfree(bbio);
 		length -= sublen;
···
  * to take those pages that are not errored from all the mirrors so that
  * the pages that are errored in the just handled mirror can be repaired.
  */
-static int scrub_recheck_block(struct btrfs_fs_info *fs_info,
-			       struct scrub_block *sblock, int is_metadata,
-			       int have_csum, u8 *csum, u64 generation,
-			       u16 csum_size)
+static void scrub_recheck_block(struct btrfs_fs_info *fs_info,
+				struct scrub_block *sblock, int is_metadata,
+				int have_csum, u8 *csum, u64 generation,
+				u16 csum_size)
 {
 	int page_num;
 
···
 
 	for (page_num = 0; page_num < sblock->page_count; page_num++) {
 		struct bio *bio;
-		int ret;
-		struct scrub_page *page = sblock->pagev + page_num;
+		struct scrub_page *page = sblock->pagev[page_num];
 		DECLARE_COMPLETION_ONSTACK(complete);
 
 		if (page->dev->bdev == NULL) {
···
 			continue;
 		}
 
-		BUG_ON(!page->page);
+		WARN_ON(!page->page);
 		bio = bio_alloc(GFP_NOFS, 1);
-		if (!bio)
-			return -EIO;
+		if (!bio) {
+			page->io_error = 1;
+			sblock->no_io_error_seen = 0;
+			continue;
+		}
 		bio->bi_bdev = page->dev->bdev;
 		bio->bi_sector = page->physical >> 9;
 		bio->bi_end_io = scrub_complete_bio_end_io;
 		bio->bi_private = &complete;
 
-		ret = bio_add_page(bio, page->page, PAGE_SIZE, 0);
-		if (PAGE_SIZE != ret) {
-			bio_put(bio);
-			return -EIO;
-		}
+		bio_add_page(bio, page->page, PAGE_SIZE, 0);
 		btrfsic_submit_bio(READ, bio);
 
 		/* this will also unplug the queue */
···
 					     have_csum, csum, generation,
 					     csum_size);
 
-	return 0;
+	return;
 }
 
 static void scrub_recheck_block_checksum(struct btrfs_fs_info *fs_info,
···
 	struct btrfs_root *root = fs_info->extent_root;
 	void *mapped_buffer;
 
-	BUG_ON(!sblock->pagev[0].page);
+	WARN_ON(!sblock->pagev[0]->page);
 	if (is_metadata) {
 		struct btrfs_header *h;
 
-		mapped_buffer = kmap_atomic(sblock->pagev[0].page);
+		mapped_buffer = kmap_atomic(sblock->pagev[0]->page);
 		h = (struct btrfs_header *)mapped_buffer;
 
-		if (sblock->pagev[0].logical != le64_to_cpu(h->bytenr) ||
+		if (sblock->pagev[0]->logical != le64_to_cpu(h->bytenr) ||
 		    memcmp(h->fsid, fs_info->fsid, BTRFS_UUID_SIZE) ||
 		    memcmp(h->chunk_tree_uuid, fs_info->chunk_tree_uuid,
 			   BTRFS_UUID_SIZE)) {
···
 		if (!have_csum)
 			return;
 
-		mapped_buffer = kmap_atomic(sblock->pagev[0].page);
+		mapped_buffer = kmap_atomic(sblock->pagev[0]->page);
 	}
 
 	for (page_num = 0;;) {
···
 		page_num++;
 		if (page_num >= sblock->page_count)
 			break;
-		BUG_ON(!sblock->pagev[page_num].page);
+		WARN_ON(!sblock->pagev[page_num]->page);
 
-		mapped_buffer = kmap_atomic(sblock->pagev[page_num].page);
+		mapped_buffer = kmap_atomic(sblock->pagev[page_num]->page);
 	}
 
 	btrfs_csum_final(crc, calculated_csum);
···
 					    struct scrub_block *sblock_good,
 					    int page_num, int force_write)
 {
-	struct scrub_page *page_bad = sblock_bad->pagev + page_num;
-	struct scrub_page *page_good = sblock_good->pagev + page_num;
+	struct scrub_page *page_bad = sblock_bad->pagev[page_num];
+	struct scrub_page *page_good = sblock_good->pagev[page_num];
 
-	BUG_ON(sblock_bad->pagev[page_num].page == NULL);
-	BUG_ON(sblock_good->pagev[page_num].page == NULL);
+	BUG_ON(page_bad->page == NULL);
+	BUG_ON(page_good->page == NULL);
 	if (force_write || sblock_bad->header_error ||
 	    sblock_bad->checksum_error || page_bad->io_error) {
 		struct bio *bio;
 		int ret;
 		DECLARE_COMPLETION_ONSTACK(complete);
+
+		if (!page_bad->dev->bdev) {
+			printk_ratelimited(KERN_WARNING
+				"btrfs: scrub_repair_page_from_good_copy(bdev == NULL) is unexpected!\n");
+			return -EIO;
+		}
 
 		bio = bio_alloc(GFP_NOFS, 1);
 		if (!bio)
···
 		if (!bio_flagged(bio, BIO_UPTODATE)) {
 			btrfs_dev_stat_inc_and_print(page_bad->dev,
 				BTRFS_DEV_STAT_WRITE_ERRS);
+			btrfs_dev_replace_stats_inc(
+				&sblock_bad->sctx->dev_root->fs_info->
+				dev_replace.num_write_errors);
 			bio_put(bio);
 			return -EIO;
 		}
···
 	return 0;
 }
 
-static void scrub_checksum(struct scrub_block *sblock)
+static void scrub_write_block_to_dev_replace(struct scrub_block *sblock)
+{
+	int page_num;
+
+	for (page_num = 0; page_num < sblock->page_count; page_num++) {
+		int ret;
+
+		ret = scrub_write_page_to_dev_replace(sblock, page_num);
+		if (ret)
+			btrfs_dev_replace_stats_inc(
+				&sblock->sctx->dev_root->fs_info->dev_replace.
+				num_write_errors);
+	}
+}
+
+static int scrub_write_page_to_dev_replace(struct scrub_block *sblock,
+					   int page_num)
+{
+	struct scrub_page *spage = sblock->pagev[page_num];
+
+	BUG_ON(spage->page == NULL);
+	if (spage->io_error) {
+		void *mapped_buffer = kmap_atomic(spage->page);
+
+		memset(mapped_buffer, 0, PAGE_CACHE_SIZE);
+		flush_dcache_page(spage->page);
+		kunmap_atomic(mapped_buffer);
+	}
+	return scrub_add_page_to_wr_bio(sblock->sctx, spage);
+}
+
+static int scrub_add_page_to_wr_bio(struct scrub_ctx *sctx,
+				    struct scrub_page *spage)
+{
+	struct scrub_wr_ctx *wr_ctx = &sctx->wr_ctx;
+	struct scrub_bio *sbio;
+	int ret;
+
+	mutex_lock(&wr_ctx->wr_lock);
+again:
+	if (!wr_ctx->wr_curr_bio) {
+		wr_ctx->wr_curr_bio = kzalloc(sizeof(*wr_ctx->wr_curr_bio),
+					      GFP_NOFS);
+		if (!wr_ctx->wr_curr_bio) {
+			mutex_unlock(&wr_ctx->wr_lock);
+			return -ENOMEM;
+		}
+		wr_ctx->wr_curr_bio->sctx = sctx;
+		wr_ctx->wr_curr_bio->page_count = 0;
+	}
+	sbio = wr_ctx->wr_curr_bio;
+	if (sbio->page_count == 0) {
+		struct bio *bio;
+
+		sbio->physical = spage->physical_for_dev_replace;
+		sbio->logical = spage->logical;
+		sbio->dev = wr_ctx->tgtdev;
+		bio = sbio->bio;
+		if (!bio) {
+			bio = bio_alloc(GFP_NOFS, wr_ctx->pages_per_wr_bio);
+			if (!bio) {
+				mutex_unlock(&wr_ctx->wr_lock);
+				return -ENOMEM;
+			}
+			sbio->bio = bio;
+		}
+
+		bio->bi_private = sbio;
+		bio->bi_end_io = scrub_wr_bio_end_io;
+		bio->bi_bdev = sbio->dev->bdev;
+		bio->bi_sector = sbio->physical >> 9;
+		sbio->err = 0;
+	} else if (sbio->physical + sbio->page_count * PAGE_SIZE !=
+		   spage->physical_for_dev_replace ||
+		   sbio->logical + sbio->page_count * PAGE_SIZE !=
+		   spage->logical) {
+		scrub_wr_submit(sctx);
+		goto again;
+	}
+
+	ret = bio_add_page(sbio->bio, spage->page, PAGE_SIZE, 0);
+	if (ret != PAGE_SIZE) {
+		if (sbio->page_count < 1) {
+			bio_put(sbio->bio);
+			sbio->bio = NULL;
+			mutex_unlock(&wr_ctx->wr_lock);
+			return -EIO;
+		}
+		scrub_wr_submit(sctx);
+		goto again;
+	}
+
+	sbio->pagev[sbio->page_count] = spage;
+	scrub_page_get(spage);
+	sbio->page_count++;
+	if (sbio->page_count == wr_ctx->pages_per_wr_bio)
+		scrub_wr_submit(sctx);
+	mutex_unlock(&wr_ctx->wr_lock);
+
+	return 0;
+}
+
+static void scrub_wr_submit(struct scrub_ctx *sctx)
+{
+	struct scrub_wr_ctx *wr_ctx = &sctx->wr_ctx;
+	struct scrub_bio *sbio;
+
+	if (!wr_ctx->wr_curr_bio)
+		return;
+
+	sbio = wr_ctx->wr_curr_bio;
+	wr_ctx->wr_curr_bio = NULL;
+	WARN_ON(!sbio->bio->bi_bdev);
+	scrub_pending_bio_inc(sctx);
+	/* process all writes in a single worker thread. Then the block layer
+	 * orders the requests before sending them to the driver which
+	 * doubled the write performance on spinning disks when measured
+	 * with Linux 3.5 */
+	btrfsic_submit_bio(WRITE, sbio->bio);
+}
+
+static void scrub_wr_bio_end_io(struct bio *bio, int err)
+{
+	struct scrub_bio *sbio = bio->bi_private;
+	struct btrfs_fs_info *fs_info = sbio->dev->dev_root->fs_info;
+
+	sbio->err = err;
+	sbio->bio = bio;
+
+	sbio->work.func = scrub_wr_bio_end_io_worker;
+	btrfs_queue_worker(&fs_info->scrub_wr_completion_workers, &sbio->work);
+}
+
+static void scrub_wr_bio_end_io_worker(struct btrfs_work *work)
+{
+	struct scrub_bio *sbio = container_of(work, struct scrub_bio, work);
+	struct scrub_ctx *sctx = sbio->sctx;
+	int i;
+
+	WARN_ON(sbio->page_count > SCRUB_PAGES_PER_WR_BIO);
+	if (sbio->err) {
+		struct btrfs_dev_replace *dev_replace =
+			&sbio->sctx->dev_root->fs_info->dev_replace;
+
+		for (i = 0; i < sbio->page_count; i++) {
+			struct scrub_page *spage = sbio->pagev[i];
+
+			spage->io_error = 1;
+			btrfs_dev_replace_stats_inc(&dev_replace->
+						    num_write_errors);
+		}
+	}
+
+	for (i = 0; i < sbio->page_count; i++)
+		scrub_page_put(sbio->pagev[i]);
+
+	bio_put(sbio->bio);
+	kfree(sbio);
+	scrub_pending_bio_dec(sctx);
+}
+
+static int scrub_checksum(struct scrub_block *sblock)
 {
 	u64 flags;
 	int ret;
 
-	BUG_ON(sblock->page_count < 1);
-	flags = sblock->pagev[0].flags;
+	WARN_ON(sblock->page_count < 1);
+	flags = sblock->pagev[0]->flags;
 	ret = 0;
 	if (flags & BTRFS_EXTENT_FLAG_DATA)
 		ret = scrub_checksum_data(sblock);
···
 		WARN_ON(1);
 	if (ret)
 		scrub_handle_errored_block(sblock);
+
+	return ret;
 }
 
 static int scrub_checksum_data(struct scrub_block *sblock)
 {
-	struct scrub_dev *sdev = sblock->sdev;
+	struct scrub_ctx *sctx = sblock->sctx;
 	u8 csum[BTRFS_CSUM_SIZE];
 	u8 *on_disk_csum;
 	struct page *page;
 	void *buffer;
 	u32 crc = ~(u32)0;
 	int fail = 0;
-	struct btrfs_root *root = sdev->dev->dev_root;
+	struct btrfs_root *root = sctx->dev_root;
 	u64 len;
 	int index;
 
 	BUG_ON(sblock->page_count < 1);
-	if (!sblock->pagev[0].have_csum)
+	if (!sblock->pagev[0]->have_csum)
 		return 0;
 
-	on_disk_csum = sblock->pagev[0].csum;
-	page = sblock->pagev[0].page;
+	on_disk_csum = sblock->pagev[0]->csum;
+	page = sblock->pagev[0]->page;
 	buffer = kmap_atomic(page);
 
-	len = sdev->sectorsize;
+	len = sctx->sectorsize;
 	index = 0;
 	for (;;) {
 		u64 l = min_t(u64, len, PAGE_SIZE);
···
 			break;
 		index++;
 		BUG_ON(index >= sblock->page_count);
-		BUG_ON(!sblock->pagev[index].page);
-		page = sblock->pagev[index].page;
+		BUG_ON(!sblock->pagev[index]->page);
+		page = sblock->pagev[index]->page;
 		buffer = kmap_atomic(page);
 	}
 
 	btrfs_csum_final(crc, csum);
-	if (memcmp(csum, on_disk_csum, sdev->csum_size))
+	if (memcmp(csum, on_disk_csum, sctx->csum_size))
 		fail = 1;
 
 	return fail;
···
 
 static int scrub_checksum_tree_block(struct scrub_block *sblock)
 {
-	struct scrub_dev *sdev = sblock->sdev;
+	struct scrub_ctx *sctx = sblock->sctx;
 	struct btrfs_header *h;
-	struct btrfs_root *root = sdev->dev->dev_root;
+	struct btrfs_root *root = sctx->dev_root;
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	u8 calculated_csum[BTRFS_CSUM_SIZE];
 	u8 on_disk_csum[BTRFS_CSUM_SIZE];
···
 	int index;
 
 	BUG_ON(sblock->page_count < 1);
-	page = sblock->pagev[0].page;
+	page = sblock->pagev[0]->page;
 	mapped_buffer = kmap_atomic(page);
 	h = (struct btrfs_header *)mapped_buffer;
-	memcpy(on_disk_csum, h->csum, sdev->csum_size);
+	memcpy(on_disk_csum, h->csum, sctx->csum_size);
 
 	/*
 	 * we don't use the getter functions here, as we
···
 	 * b) the page is already kmapped
 	 */
 
-	if (sblock->pagev[0].logical != le64_to_cpu(h->bytenr))
+	if (sblock->pagev[0]->logical != le64_to_cpu(h->bytenr))
 		++fail;
 
-	if (sblock->pagev[0].generation != le64_to_cpu(h->generation))
+	if (sblock->pagev[0]->generation != le64_to_cpu(h->generation))
 		++fail;
 
 	if (memcmp(h->fsid, fs_info->fsid, BTRFS_UUID_SIZE))
···
 		   BTRFS_UUID_SIZE))
 		++fail;
 
-	BUG_ON(sdev->nodesize != sdev->leafsize);
-	len = sdev->nodesize - BTRFS_CSUM_SIZE;
+	WARN_ON(sctx->nodesize != sctx->leafsize);
+	len = sctx->nodesize - BTRFS_CSUM_SIZE;
 	mapped_size = PAGE_SIZE - BTRFS_CSUM_SIZE;
 	p = ((u8 *)mapped_buffer) + BTRFS_CSUM_SIZE;
 	index = 0;
···
 			break;
 		index++;
 		BUG_ON(index >= sblock->page_count);
-		BUG_ON(!sblock->pagev[index].page);
-		page = sblock->pagev[index].page;
+		BUG_ON(!sblock->pagev[index]->page);
+		page = sblock->pagev[index]->page;
 		mapped_buffer = kmap_atomic(page);
 		mapped_size = PAGE_SIZE;
 		p = mapped_buffer;
 	}
 
 	btrfs_csum_final(crc, calculated_csum);
-	if (memcmp(calculated_csum, on_disk_csum, sdev->csum_size))
+	if (memcmp(calculated_csum, on_disk_csum, sctx->csum_size))
 		++crc_fail;
 
 	return fail || crc_fail;
···
 static int scrub_checksum_super(struct scrub_block *sblock)
 {
 	struct btrfs_super_block *s;
-	struct scrub_dev *sdev = sblock->sdev;
-	struct btrfs_root *root = sdev->dev->dev_root;
+	struct scrub_ctx *sctx = sblock->sctx;
+	struct btrfs_root *root = sctx->dev_root;
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	u8 calculated_csum[BTRFS_CSUM_SIZE];
 	u8 on_disk_csum[BTRFS_CSUM_SIZE];
···
 	int index;
 
 	BUG_ON(sblock->page_count < 1);
-	page = sblock->pagev[0].page;
+	page = sblock->pagev[0]->page;
 	mapped_buffer = kmap_atomic(page);
 	s = (struct btrfs_super_block *)mapped_buffer;
-	memcpy(on_disk_csum, s->csum, sdev->csum_size);
+	memcpy(on_disk_csum, s->csum, sctx->csum_size);
 
-	if (sblock->pagev[0].logical != le64_to_cpu(s->bytenr))
+	if (sblock->pagev[0]->logical != le64_to_cpu(s->bytenr))
 		++fail_cor;
 
-	if (sblock->pagev[0].generation != le64_to_cpu(s->generation))
+	if (sblock->pagev[0]->generation != le64_to_cpu(s->generation))
 		++fail_gen;
 
 	if (memcmp(s->fsid, fs_info->fsid, BTRFS_UUID_SIZE))
···
 			break;
 		index++;
 		BUG_ON(index >= sblock->page_count);
-		BUG_ON(!sblock->pagev[index].page);
-		page = sblock->pagev[index].page;
+		BUG_ON(!sblock->pagev[index]->page);
+		page = sblock->pagev[index]->page;
 		mapped_buffer = kmap_atomic(page);
 		mapped_size = PAGE_SIZE;
 		p = mapped_buffer;
 	}
 
 	btrfs_csum_final(crc, calculated_csum);
-	if (memcmp(calculated_csum, on_disk_csum, sdev->csum_size))
+	if (memcmp(calculated_csum, on_disk_csum, sctx->csum_size))
 		++fail_cor;
 
 	if (fail_cor + fail_gen) {
···
 		 * They will get written with the next transaction commit
 		 * anyway
 		 */
-		spin_lock(&sdev->stat_lock);
-		++sdev->stat.super_errors;
-		spin_unlock(&sdev->stat_lock);
+		spin_lock(&sctx->stat_lock);
+		++sctx->stat.super_errors;
+		spin_unlock(&sctx->stat_lock);
 		if (fail_cor)
-			btrfs_dev_stat_inc_and_print(sdev->dev,
+			btrfs_dev_stat_inc_and_print(sblock->pagev[0]->dev,
 				BTRFS_DEV_STAT_CORRUPTION_ERRS);
 		else
-			btrfs_dev_stat_inc_and_print(sdev->dev,
+			btrfs_dev_stat_inc_and_print(sblock->pagev[0]->dev,
 				BTRFS_DEV_STAT_GENERATION_ERRS);
 	}
 
···
 		int i;
 
 		for (i = 0; i < sblock->page_count; i++)
-			if (sblock->pagev[i].page)
-				__free_page(sblock->pagev[i].page);
+			scrub_page_put(sblock->pagev[i]);
 		kfree(sblock);
 	}
 }
 
-static void scrub_submit(struct scrub_dev *sdev)
+static void scrub_page_get(struct scrub_page *spage)
+{
+	atomic_inc(&spage->ref_count);
+}
+
+static void scrub_page_put(struct scrub_page *spage)
+{
+	if (atomic_dec_and_test(&spage->ref_count)) {
+		if (spage->page)
+			__free_page(spage->page);
+		kfree(spage);
+	}
+}
+
+static void scrub_submit(struct scrub_ctx *sctx)
 {
 	struct scrub_bio *sbio;
 
-	if (sdev->curr == -1)
+	if (sctx->curr == -1)
 		return;
 
-	sbio = sdev->bios[sdev->curr];
-	sdev->curr = -1;
-	atomic_inc(&sdev->in_flight);
+	sbio = sctx->bios[sctx->curr];
+	sctx->curr = -1;
+	scrub_pending_bio_inc(sctx);
 
-	btrfsic_submit_bio(READ, sbio->bio);
+	if (!sbio->bio->bi_bdev) {
+		/*
+		 * this case should not happen. If btrfs_map_block() is
+		 * wrong, it could happen for dev-replace operations on
+		 * missing devices when no mirrors are available, but in
+		 * this case it should already fail the mount.
+		 * This case is handled correctly (but _very_ slowly).
+		 */
+		printk_ratelimited(KERN_WARNING
+			"btrfs: scrub_submit(bio bdev == NULL) is unexpected!\n");
+		bio_endio(sbio->bio, -EIO);
+	} else {
+		btrfsic_submit_bio(READ, sbio->bio);
+	}
 }
 
-static int scrub_add_page_to_bio(struct scrub_dev *sdev,
-				 struct scrub_page *spage)
+static int scrub_add_page_to_rd_bio(struct scrub_ctx *sctx,
+				    struct scrub_page *spage)
 {
 	struct scrub_block *sblock = spage->sblock;
 	struct scrub_bio *sbio;
···
 	/*
 	 * grab a fresh bio or wait for one to become available
 	 */
-	while (sdev->curr == -1) {
-		spin_lock(&sdev->list_lock);
-		sdev->curr = sdev->first_free;
-		if (sdev->curr != -1) {
-			sdev->first_free = sdev->bios[sdev->curr]->next_free;
-			sdev->bios[sdev->curr]->next_free = -1;
-			sdev->bios[sdev->curr]->page_count = 0;
-			spin_unlock(&sdev->list_lock);
+	while (sctx->curr == -1) {
+		spin_lock(&sctx->list_lock);
+		sctx->curr = sctx->first_free;
+		if (sctx->curr != -1) {
+			sctx->first_free = sctx->bios[sctx->curr]->next_free;
+			sctx->bios[sctx->curr]->next_free = -1;
+			sctx->bios[sctx->curr]->page_count = 0;
+			spin_unlock(&sctx->list_lock);
 		} else {
-			spin_unlock(&sdev->list_lock);
-			wait_event(sdev->list_wait, sdev->first_free != -1);
+			spin_unlock(&sctx->list_lock);
+			wait_event(sctx->list_wait, sctx->first_free != -1);
 		}
 	}
-	sbio = sdev->bios[sdev->curr];
+	sbio = sctx->bios[sctx->curr];
 	if (sbio->page_count == 0) {
 		struct bio *bio;
 
 		sbio->physical = spage->physical;
 		sbio->logical = spage->logical;
+		sbio->dev = spage->dev;
 		bio = sbio->bio;
 		if (!bio) {
-			bio = bio_alloc(GFP_NOFS, sdev->pages_per_bio);
+			bio = bio_alloc(GFP_NOFS, sctx->pages_per_rd_bio);
 			if (!bio)
 				return -ENOMEM;
 			sbio->bio = bio;
···
 
 		bio->bi_private = sbio;
 		bio->bi_end_io = scrub_bio_end_io;
-		bio->bi_bdev = sdev->dev->bdev;
-		bio->bi_sector = spage->physical >> 9;
+		bio->bi_bdev = sbio->dev->bdev;
+		bio->bi_sector = sbio->physical >> 9;
 		sbio->err = 0;
 	} else if (sbio->physical + sbio->page_count * PAGE_SIZE !=
 		   spage->physical ||
 		   sbio->logical + sbio->page_count * PAGE_SIZE !=
-		   spage->logical) {
-		scrub_submit(sdev);
+		   spage->logical ||
+		   sbio->dev != spage->dev) {
+		scrub_submit(sctx);
 		goto again;
 	}
 
···
 			sbio->bio = NULL;
 			return -EIO;
 		}
-		scrub_submit(sdev);
+		scrub_submit(sctx);
 		goto again;
 	}
 
-	scrub_block_get(sblock); /* one for the added page */
+	scrub_block_get(sblock); /* one for the page added to the bio */
 	atomic_inc(&sblock->outstanding_pages);
 	sbio->page_count++;
-	if (sbio->page_count == sdev->pages_per_bio)
-		scrub_submit(sdev);
+	if (sbio->page_count == sctx->pages_per_rd_bio)
+		scrub_submit(sctx);
 
 	return 0;
 }
 
-static int scrub_pages(struct scrub_dev *sdev, u64 logical, u64 len,
-		       u64 physical, u64 flags, u64 gen, int mirror_num,
-		       u8 *csum, int force)
+static int scrub_pages(struct scrub_ctx *sctx, u64 logical, u64 len,
+		       u64 physical, struct btrfs_device *dev, u64 flags,
+		       u64 gen, int mirror_num, u8 *csum, int force,
+		       u64 physical_for_dev_replace)
 {
 	struct scrub_block *sblock;
 	int index;
 
 	sblock = kzalloc(sizeof(*sblock), GFP_NOFS);
 	if (!sblock) {
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.malloc_errors++;
-		spin_unlock(&sdev->stat_lock);
+		spin_lock(&sctx->stat_lock);
+		sctx->stat.malloc_errors++;
+		spin_unlock(&sctx->stat_lock);
 		return -ENOMEM;
 	}
 
-	/* one ref inside this function, plus one for each page later on */
+	/* one ref inside this function, plus one for each page added to
+	 * a bio later on */
 	atomic_set(&sblock->ref_count, 1);
-	sblock->sdev = sdev;
+	sblock->sctx = sctx;
 	sblock->no_io_error_seen = 1;
 
 	for (index = 0; len > 0; index++) {
-		struct scrub_page *spage = sblock->pagev + index;
+		struct scrub_page *spage;
 		u64 l = min_t(u64, len, PAGE_SIZE);
 
-		BUG_ON(index >= SCRUB_MAX_PAGES_PER_BLOCK);
-		spage->page = alloc_page(GFP_NOFS);
-		if (!spage->page) {
-			spin_lock(&sdev->stat_lock);
-			sdev->stat.malloc_errors++;
-			spin_unlock(&sdev->stat_lock);
-			while (index > 0) {
-				index--;
-				__free_page(sblock->pagev[index].page);
-			}
-			kfree(sblock);
+		spage = kzalloc(sizeof(*spage), GFP_NOFS);
+		if (!spage) {
+leave_nomem:
+			spin_lock(&sctx->stat_lock);
+			sctx->stat.malloc_errors++;
+			spin_unlock(&sctx->stat_lock);
+			scrub_block_put(sblock);
 			return -ENOMEM;
 		}
+		BUG_ON(index >= SCRUB_MAX_PAGES_PER_BLOCK);
+		scrub_page_get(spage);
+		sblock->pagev[index] = spage;
 		spage->sblock = sblock;
-		spage->dev = sdev->dev;
+		spage->dev = dev;
 		spage->flags = flags;
 		spage->generation = gen;
 		spage->logical = logical;
 		spage->physical = physical;
+		spage->physical_for_dev_replace = physical_for_dev_replace;
 		spage->mirror_num = mirror_num;
 		if (csum) {
 			spage->have_csum = 1;
-			memcpy(spage->csum, csum, sdev->csum_size);
+			memcpy(spage->csum, csum, sctx->csum_size);
 		} else {
 			spage->have_csum = 0;
 		}
 		sblock->page_count++;
+		spage->page = alloc_page(GFP_NOFS);
+		if (!spage->page)
+			goto leave_nomem;
 		len -= l;
 		logical += l;
 		physical += l;
+		physical_for_dev_replace += l;
 	}
 
-	BUG_ON(sblock->page_count == 0);
+	WARN_ON(sblock->page_count == 0);
 	for (index = 0; index < sblock->page_count; index++) {
-		struct scrub_page *spage = sblock->pagev + index;
+		struct scrub_page *spage = sblock->pagev[index];
 		int ret;
 
-		ret = scrub_add_page_to_bio(sdev, spage);
+		ret = scrub_add_page_to_rd_bio(sctx, spage);
 		if (ret) {
 			scrub_block_put(sblock);
 			return ret;
···
 	}
 
 	if (force)
-		scrub_submit(sdev);
+		scrub_submit(sctx);
 
 	/* last one frees, either here or in bio completion for last page */
 	scrub_block_put(sblock);
···
 static void scrub_bio_end_io(struct bio *bio, int err)
 {
 	struct scrub_bio *sbio = bio->bi_private;
-	struct scrub_dev *sdev = sbio->sdev;
-	struct btrfs_fs_info *fs_info = sdev->dev->dev_root->fs_info;
+	struct btrfs_fs_info *fs_info = sbio->dev->dev_root->fs_info;
 
 	sbio->err = err;
 	sbio->bio = bio;
···
 static void scrub_bio_end_io_worker(struct btrfs_work *work)
 {
 	struct scrub_bio *sbio = container_of(work, struct scrub_bio, work);
-	struct scrub_dev *sdev = sbio->sdev;
+	struct scrub_ctx *sctx = sbio->sctx;
 	int i;
 
-	BUG_ON(sbio->page_count > SCRUB_PAGES_PER_BIO);
+	BUG_ON(sbio->page_count > SCRUB_PAGES_PER_RD_BIO);
 	if (sbio->err) {
 		for (i = 0; i < sbio->page_count; i++) {
 			struct scrub_page *spage = sbio->pagev[i];
···
 
 	bio_put(sbio->bio);
 	sbio->bio = NULL;
-	spin_lock(&sdev->list_lock);
-	sbio->next_free = sdev->first_free;
-	sdev->first_free = sbio->index;
-	spin_unlock(&sdev->list_lock);
-	atomic_dec(&sdev->in_flight);
-	wake_up(&sdev->list_wait);
+	spin_lock(&sctx->list_lock);
+	sbio->next_free = sctx->first_free;
+	sctx->first_free = sbio->index;
+	spin_unlock(&sctx->list_lock);
+
+	if (sctx->is_dev_replace &&
+	    atomic_read(&sctx->wr_ctx.flush_all_writes)) {
+		mutex_lock(&sctx->wr_ctx.wr_lock);
+		scrub_wr_submit(sctx);
+		mutex_unlock(&sctx->wr_ctx.wr_lock);
+	}
+
+	scrub_pending_bio_dec(sctx);
 }
 
 static void scrub_block_complete(struct scrub_block *sblock)
 {
-	if (!sblock->no_io_error_seen)
+	if (!sblock->no_io_error_seen) {
 		scrub_handle_errored_block(sblock);
-	else
-		scrub_checksum(sblock);
+	} else {
+		/*
+		 * if has checksum error, write via repair mechanism in
+		 * dev replace case, otherwise write here in dev replace
+		 * case.
+		 */
+		if (!scrub_checksum(sblock) && sblock->sctx->is_dev_replace)
+			scrub_write_block_to_dev_replace(sblock);
+	}
 }
 
-static int scrub_find_csum(struct scrub_dev *sdev, u64 logical, u64 len,
+static int scrub_find_csum(struct scrub_ctx *sctx, u64 logical, u64 len,
 			   u8 *csum)
 {
 	struct btrfs_ordered_sum *sum = NULL;
···
 	unsigned long i;
 	unsigned long num_sectors;
 
-	while (!list_empty(&sdev->csum_list)) {
-		sum = list_first_entry(&sdev->csum_list,
+	while (!list_empty(&sctx->csum_list)) {
+		sum = list_first_entry(&sctx->csum_list,
 				       struct btrfs_ordered_sum, list);
 		if (sum->bytenr > logical)
 			return 0;
 		if (sum->bytenr + sum->len > logical)
 			break;
 
-		++sdev->stat.csum_discards;
+		++sctx->stat.csum_discards;
 		list_del(&sum->list);
 		kfree(sum);
 		sum = NULL;
···
 	if (!sum)
 		return 0;
 
-	num_sectors = sum->len / sdev->sectorsize;
+	num_sectors = sum->len / sctx->sectorsize;
 	for (i = 0; i < num_sectors; ++i) {
 		if (sum->sums[i].bytenr == logical) {
-			memcpy(csum, &sum->sums[i].sum, sdev->csum_size);
+			memcpy(csum, &sum->sums[i].sum, sctx->csum_size);
 			ret = 1;
 			break;
 		}
···
 }
 
 /* scrub extent tries to collect up to 64 kB for each bio */
-static int scrub_extent(struct scrub_dev *sdev, u64 logical, u64 len,
-			u64 physical, u64 flags, u64 gen, int mirror_num)
+static int scrub_extent(struct scrub_ctx *sctx, u64 logical, u64 len,
+			u64 physical, struct btrfs_device *dev, u64 flags,
+			u64 gen, int mirror_num, u64 physical_for_dev_replace)
 {
 	int ret;
 	u8 csum[BTRFS_CSUM_SIZE];
 	u32 blocksize;
 
 	if (flags & BTRFS_EXTENT_FLAG_DATA) {
-		blocksize = sdev->sectorsize;
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.data_extents_scrubbed++;
-		sdev->stat.data_bytes_scrubbed += len;
-		spin_unlock(&sdev->stat_lock);
+		blocksize = sctx->sectorsize;
+		spin_lock(&sctx->stat_lock);
+		sctx->stat.data_extents_scrubbed++;
+		sctx->stat.data_bytes_scrubbed += len;
+		spin_unlock(&sctx->stat_lock);
 	} else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
-		BUG_ON(sdev->nodesize != sdev->leafsize);
-		blocksize = sdev->nodesize;
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.tree_extents_scrubbed++;
-		sdev->stat.tree_bytes_scrubbed += len;
-		spin_unlock(&sdev->stat_lock);
+		WARN_ON(sctx->nodesize != sctx->leafsize);
+		blocksize = sctx->nodesize;
+		spin_lock(&sctx->stat_lock);
+		sctx->stat.tree_extents_scrubbed++;
+		sctx->stat.tree_bytes_scrubbed += len;
+		spin_unlock(&sctx->stat_lock);
 	} else {
-		blocksize = sdev->sectorsize;
-		BUG_ON(1);
+		blocksize = sctx->sectorsize;
+		WARN_ON(1);
 	}
 
 	while (len) {
···
 
 		if (flags & BTRFS_EXTENT_FLAG_DATA) {
 			/* push csums to sbio */
-			have_csum = scrub_find_csum(sdev, logical, l, csum);
+			have_csum = scrub_find_csum(sctx, logical, l, csum);
 			if (have_csum == 0)
-				++sdev->stat.no_csum;
+				++sctx->stat.no_csum;
+			if (sctx->is_dev_replace && !have_csum) {
+				ret = copy_nocow_pages(sctx, logical, l,
+						       mirror_num,
+						      physical_for_dev_replace);
+				goto behind_scrub_pages;
+			}
 		}
-		ret = scrub_pages(sdev, logical, l, physical, flags, gen,
-				  mirror_num, have_csum ? csum : NULL, 0);
+		ret = scrub_pages(sctx, logical, l, physical, dev, flags, gen,
+				  mirror_num, have_csum ? csum : NULL, 0,
+				  physical_for_dev_replace);
+behind_scrub_pages:
 		if (ret)
 			return ret;
 		len -= l;
 		logical += l;
 		physical += l;
+		physical_for_dev_replace += l;
 	}
 	return 0;
 }
 
-static noinline_for_stack int scrub_stripe(struct scrub_dev *sdev,
-	struct map_lookup *map, int num, u64 base, u64 length)
+static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
+					   struct map_lookup *map,
+					   struct btrfs_device *scrub_dev,
+					   int num, u64 base, u64 length,
+					   int is_dev_replace)
 {
 	struct btrfs_path *path;
-	struct btrfs_fs_info *fs_info = sdev->dev->dev_root->fs_info;
+	struct btrfs_fs_info *fs_info = sctx->dev_root->fs_info;
 	struct btrfs_root *root = fs_info->extent_root;
 	struct btrfs_root *csum_root = fs_info->csum_root;
 	struct btrfs_extent_item *extent;
···
 	struct reada_control *reada2;
 	struct btrfs_key key_start;
 	struct btrfs_key key_end;
-
 	u64 increment = map->stripe_len;
 	u64 offset;
+	u64 extent_logical;
+	u64 extent_physical;
+	u64 extent_len;
+	struct btrfs_device *extent_dev;
+	int extent_mirror_num;
 
 	nstripes = length;
 	offset = 0;
···
 	 */
 	logical = base + offset;
 
-	wait_event(sdev->list_wait,
-		   atomic_read(&sdev->in_flight) == 0);
+	wait_event(sctx->list_wait,
+		   atomic_read(&sctx->bios_in_flight) == 0);
 	atomic_inc(&fs_info->scrubs_paused);
 	wake_up(&fs_info->scrub_pause_wait);
 
···
 		 * canceled?
 		 */
 		if (atomic_read(&fs_info->scrub_cancel_req) ||
-		    atomic_read(&sdev->cancel_req)) {
+		    atomic_read(&sctx->cancel_req)) {
 			ret = -ECANCELED;
 			goto out;
 		}
···
 		 */
 		if (atomic_read(&fs_info->scrub_pause_req)) {
 			/* push queued extents */
-			scrub_submit(sdev);
-			wait_event(sdev->list_wait,
-				   atomic_read(&sdev->in_flight) == 0);
+			atomic_set(&sctx->wr_ctx.flush_all_writes, 1);
+			scrub_submit(sctx);
+			mutex_lock(&sctx->wr_ctx.wr_lock);
+			scrub_wr_submit(sctx);
+			mutex_unlock(&sctx->wr_ctx.wr_lock);
+			wait_event(sctx->list_wait,
+				   atomic_read(&sctx->bios_in_flight) == 0);
+			atomic_set(&sctx->wr_ctx.flush_all_writes, 0);
 			atomic_inc(&fs_info->scrubs_paused);
 			wake_up(&fs_info->scrub_pause_wait);
 			mutex_lock(&fs_info->scrub_lock);
···
 
 		ret = btrfs_lookup_csums_range(csum_root, logical,
 					       logical + map->stripe_len - 1,
-					       &sdev->csum_list, 1);
+					       &sctx->csum_list, 1);
 		if (ret)
 			goto out;
 
···
 					     key.objectid;
 			}
 
-			ret = scrub_extent(sdev, key.objectid, key.offset,
-					   key.objectid - logical + physical,
-					   flags, generation, mirror_num);
+			extent_logical = key.objectid;
+			extent_physical = key.objectid - logical + physical;
+			extent_len = key.offset;
+			extent_dev = scrub_dev;
+			extent_mirror_num = mirror_num;
+			if (is_dev_replace)
+				scrub_remap_extent(fs_info, extent_logical,
+						   extent_len, &extent_physical,
+						   &extent_dev,
+						   &extent_mirror_num);
+			ret = scrub_extent(sctx, extent_logical, extent_len,
+					   extent_physical, extent_dev, flags,
+					   generation, extent_mirror_num,
+					   key.objectid - logical + physical);
 			if (ret)
 				goto out;
 
···
 		btrfs_release_path(path);
 		logical += increment;
 		physical += map->stripe_len;
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.last_physical = physical;
-		spin_unlock(&sdev->stat_lock);
+		spin_lock(&sctx->stat_lock);
+		sctx->stat.last_physical = physical;
+		spin_unlock(&sctx->stat_lock);
 	}
-	/* push queued extents */
-	scrub_submit(sdev);
-
 out:
+	/* push queued extents */
+	scrub_submit(sctx);
+	mutex_lock(&sctx->wr_ctx.wr_lock);
+	scrub_wr_submit(sctx);
+	mutex_unlock(&sctx->wr_ctx.wr_lock);
+
 	blk_finish_plug(&plug);
 	btrfs_free_path(path);
 	return ret < 0 ? ret : 0;
 }
 
-static noinline_for_stack int scrub_chunk(struct scrub_dev *sdev,
-	u64 chunk_tree, u64 chunk_objectid, u64 chunk_offset, u64 length,
-	u64 dev_offset)
+static noinline_for_stack int scrub_chunk(struct scrub_ctx *sctx,
+					  struct btrfs_device *scrub_dev,
+					  u64 chunk_tree, u64 chunk_objectid,
+					  u64 chunk_offset, u64 length,
+					  u64 dev_offset, int is_dev_replace)
 {
 	struct btrfs_mapping_tree *map_tree =
-		&sdev->dev->dev_root->fs_info->mapping_tree;
+		&sctx->dev_root->fs_info->mapping_tree;
 	struct map_lookup *map;
 	struct extent_map *em;
 	int i;
-	int ret = -EINVAL;
+	int ret = 0;
 
 	read_lock(&map_tree->map_tree.lock);
 	em = lookup_extent_mapping(&map_tree->map_tree, chunk_offset, 1);
···
 		goto out;
 
 	for (i = 0; i < map->num_stripes; ++i) {
-		if (map->stripes[i].dev == sdev->dev &&
+		if (map->stripes[i].dev->bdev == scrub_dev->bdev &&
 		    map->stripes[i].physical == dev_offset) {
-			ret = scrub_stripe(sdev, map, i, chunk_offset, length);
+			ret = scrub_stripe(sctx, map, scrub_dev, i,
+					   chunk_offset, length,
+					   is_dev_replace);
 			if (ret)
 				goto out;
 		}
···
 }
 
 static noinline_for_stack
-int scrub_enumerate_chunks(struct scrub_dev *sdev, u64 start, u64 end)
+int scrub_enumerate_chunks(struct scrub_ctx *sctx,
+			   struct btrfs_device *scrub_dev, u64 start, u64 end,
+			   int is_dev_replace)
 {
 	struct btrfs_dev_extent *dev_extent = NULL;
 	struct btrfs_path *path;
-	struct btrfs_root *root = sdev->dev->dev_root;
+	struct btrfs_root *root = sctx->dev_root;
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	u64 length;
 	u64 chunk_tree;
···
 	struct btrfs_key key;
 	struct btrfs_key found_key;
 	struct btrfs_block_group_cache *cache;
+	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 
 	path = btrfs_alloc_path();
 	if (!path)
···
 	path->search_commit_root = 1;
 	path->skip_locking = 1;
 
-	key.objectid = sdev->dev->devid;
+	key.objectid = scrub_dev->devid;
 	key.offset = 0ull;
 	key.type = BTRFS_DEV_EXTENT_KEY;
-
 
 	while (1) {
 		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
···
 
 		btrfs_item_key_to_cpu(l, &found_key, slot);
 
-		if (found_key.objectid != sdev->dev->devid)
+		if (found_key.objectid != scrub_dev->devid)
 			break;
 
 		if (btrfs_key_type(&found_key) != BTRFS_DEV_EXTENT_KEY)
···
 			ret = -ENOENT;
 			break;
 		}
-		ret = scrub_chunk(sdev, chunk_tree, chunk_objectid,
-				  chunk_offset, length, found_key.offset);
+		dev_replace->cursor_right = found_key.offset + length;
+		dev_replace->cursor_left = found_key.offset;
+		dev_replace->item_needs_writeback = 1;
+		ret = scrub_chunk(sctx, scrub_dev, chunk_tree, chunk_objectid,
+				  chunk_offset, length, found_key.offset,
+				  is_dev_replace);
+
+		/*
+		 * flush, submit all pending read and write bios, afterwards
+		 * wait for them.
+		 * Note that in the dev replace case, a read request causes
+		 * write requests that are submitted in the read completion
+		 * worker. Therefore in the current situation, it is required
+		 * that all write requests are flushed, so that all read and
+		 * write requests are really completed when bios_in_flight
+		 * changes to 0.
+		 */
+		atomic_set(&sctx->wr_ctx.flush_all_writes, 1);
+		scrub_submit(sctx);
+		mutex_lock(&sctx->wr_ctx.wr_lock);
+		scrub_wr_submit(sctx);
+		mutex_unlock(&sctx->wr_ctx.wr_lock);
+
+		wait_event(sctx->list_wait,
+			   atomic_read(&sctx->bios_in_flight) == 0);
+		atomic_set(&sctx->wr_ctx.flush_all_writes, 0);
+		atomic_inc(&fs_info->scrubs_paused);
+		wake_up(&fs_info->scrub_pause_wait);
+		wait_event(sctx->list_wait,
+			   atomic_read(&sctx->workers_pending) == 0);
+
+		mutex_lock(&fs_info->scrub_lock);
+		while (atomic_read(&fs_info->scrub_pause_req)) {
+			mutex_unlock(&fs_info->scrub_lock);
+			wait_event(fs_info->scrub_pause_wait,
+			   atomic_read(&fs_info->scrub_pause_req) == 0);
+			mutex_lock(&fs_info->scrub_lock);
+		}
+		atomic_dec(&fs_info->scrubs_paused);
+		mutex_unlock(&fs_info->scrub_lock);
+		wake_up(&fs_info->scrub_pause_wait);
+
+		dev_replace->cursor_left = dev_replace->cursor_right;
+		dev_replace->item_needs_writeback = 1;
 		btrfs_put_block_group(cache);
 		if (ret)
 			break;
+		if (is_dev_replace &&
+		    atomic64_read(&dev_replace->num_write_errors) > 0) {
+			ret = -EIO;
+			break;
+		}
+		if (sctx->stat.malloc_errors > 0) {
+			ret = -ENOMEM;
+			break;
+		}
 
 		key.offset = found_key.offset + length;
 		btrfs_release_path(path);
···
 	return ret < 0 ? ret : 0;
 }
 
-static noinline_for_stack int scrub_supers(struct scrub_dev *sdev)
+static noinline_for_stack int scrub_supers(struct scrub_ctx *sctx,
+					   struct btrfs_device *scrub_dev)
 {
 	int	i;
 	u64	bytenr;
 	u64	gen;
 	int	ret;
-	struct btrfs_device *device = sdev->dev;
-	struct btrfs_root *root = device->dev_root;
+	struct btrfs_root *root = sctx->dev_root;
 
 	if (root->fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR)
 		return -EIO;
···
 
 	for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
 		bytenr = btrfs_sb_offset(i);
-		if (bytenr + BTRFS_SUPER_INFO_SIZE > device->total_bytes)
+		if (bytenr + BTRFS_SUPER_INFO_SIZE > scrub_dev->total_bytes)
 			break;
 
-		ret = scrub_pages(sdev, bytenr, BTRFS_SUPER_INFO_SIZE, bytenr,
-				     BTRFS_EXTENT_FLAG_SUPER, gen, i, NULL, 1);
+		ret = scrub_pages(sctx, bytenr, BTRFS_SUPER_INFO_SIZE, bytenr,
+				  scrub_dev, BTRFS_EXTENT_FLAG_SUPER, gen, i,
+				  NULL, 1, bytenr);
 		if (ret)
 			return ret;
 	}
-	wait_event(sdev->list_wait, atomic_read(&sdev->in_flight) == 0);
+	wait_event(sctx->list_wait, atomic_read(&sctx->bios_in_flight) == 0);
 
 	return 0;
 }
···
 /*
  * get a reference count on fs_info->scrub_workers. start worker if necessary
  */
-static noinline_for_stack int scrub_workers_get(struct btrfs_root *root)
+static noinline_for_stack int scrub_workers_get(struct btrfs_fs_info *fs_info,
+						int is_dev_replace)
 {
-	struct btrfs_fs_info *fs_info = root->fs_info;
 	int ret = 0;
 
 	mutex_lock(&fs_info->scrub_lock);
 	if (fs_info->scrub_workers_refcnt == 0) {
-		btrfs_init_workers(&fs_info->scrub_workers, "scrub",
-			   fs_info->thread_pool_size, &fs_info->generic_worker);
+		if (is_dev_replace)
+			btrfs_init_workers(&fs_info->scrub_workers, "scrub", 1,
+					&fs_info->generic_worker);
+		else
+			btrfs_init_workers(&fs_info->scrub_workers, "scrub",
+					fs_info->thread_pool_size,
+					&fs_info->generic_worker);
 		fs_info->scrub_workers.idle_thresh = 4;
 		ret = btrfs_start_workers(&fs_info->scrub_workers);
+		if (ret)
+			goto out;
+		btrfs_init_workers(&fs_info->scrub_wr_completion_workers,
+				   "scrubwrc",
+				   fs_info->thread_pool_size,
+				   &fs_info->generic_worker);
+		fs_info->scrub_wr_completion_workers.idle_thresh = 2;
+		ret = btrfs_start_workers(
+				&fs_info->scrub_wr_completion_workers);
+		if (ret)
+			goto out;
+		btrfs_init_workers(&fs_info->scrub_nocow_workers, "scrubnc", 1,
+				   &fs_info->generic_worker);
+		ret = btrfs_start_workers(&fs_info->scrub_nocow_workers);
 		if (ret)
 			goto out;
 	}
···
 	return ret;
 }
 
-static noinline_for_stack void scrub_workers_put(struct btrfs_root *root)
+static noinline_for_stack void scrub_workers_put(struct btrfs_fs_info *fs_info)
 {
-	struct btrfs_fs_info *fs_info = root->fs_info;
-
 	mutex_lock(&fs_info->scrub_lock);
-	if (--fs_info->scrub_workers_refcnt == 0)
+	if (--fs_info->scrub_workers_refcnt == 0) {
 		btrfs_stop_workers(&fs_info->scrub_workers);
+		btrfs_stop_workers(&fs_info->scrub_wr_completion_workers);
+		btrfs_stop_workers(&fs_info->scrub_nocow_workers);
+	}
 	WARN_ON(fs_info->scrub_workers_refcnt < 0);
 	mutex_unlock(&fs_info->scrub_lock);
 }
 
-
-int btrfs_scrub_dev(struct btrfs_root *root, u64 devid, u64 start, u64 end,
-		    struct btrfs_scrub_progress *progress, int readonly)
+int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
+		    u64 end, struct btrfs_scrub_progress *progress,
+		    int readonly, int is_dev_replace)
 {
-	struct scrub_dev *sdev;
-	struct btrfs_fs_info *fs_info = root->fs_info;
+	struct scrub_ctx *sctx;
 	int ret;
 	struct btrfs_device *dev;
 
-	if (btrfs_fs_closing(root->fs_info))
+	if (btrfs_fs_closing(fs_info))
 		return -EINVAL;
 
 	/*
 	 * check some assumptions
 	 */
-	if (root->nodesize != root->leafsize) {
+	if (fs_info->chunk_root->nodesize != fs_info->chunk_root->leafsize) {
 		printk(KERN_ERR
 		       "btrfs_scrub: size assumption nodesize == leafsize (%d == %d) fails\n",
-		       root->nodesize, root->leafsize);
+		       fs_info->chunk_root->nodesize,
+		       fs_info->chunk_root->leafsize);
 		return -EINVAL;
 	}
 
-	if (root->nodesize > BTRFS_STRIPE_LEN) {
+	if (fs_info->chunk_root->nodesize > BTRFS_STRIPE_LEN) {
 		/*
 		 * in this case scrub is unable to calculate the checksum
 		 * the way scrub is implemented. Do not handle this
···
 		 */
 		printk(KERN_ERR
 		       "btrfs_scrub: size assumption nodesize <= BTRFS_STRIPE_LEN (%d <= %d) fails\n",
-		       root->nodesize, BTRFS_STRIPE_LEN);
+		       fs_info->chunk_root->nodesize, BTRFS_STRIPE_LEN);
 		return -EINVAL;
 	}
 
-	if (root->sectorsize != PAGE_SIZE) {
+	if (fs_info->chunk_root->sectorsize != PAGE_SIZE) {
 		/* not supported for data w/o checksums */
 		printk(KERN_ERR
 		       "btrfs_scrub: size assumption sectorsize != PAGE_SIZE (%d != %lld) fails\n",
-		       root->sectorsize, (unsigned long long)PAGE_SIZE);
+		       fs_info->chunk_root->sectorsize,
+		       (unsigned long long)PAGE_SIZE);
 		return -EINVAL;
 	}
 
-	ret = scrub_workers_get(root);
+	if (fs_info->chunk_root->nodesize >
+	    PAGE_SIZE * SCRUB_MAX_PAGES_PER_BLOCK ||
+	    fs_info->chunk_root->sectorsize >
+	    PAGE_SIZE * SCRUB_MAX_PAGES_PER_BLOCK) {
+		/*
+		 * would exhaust the array bounds of pagev member in
+		 * struct scrub_block
+		 */
+		pr_err("btrfs_scrub: size assumption nodesize and sectorsize <= SCRUB_MAX_PAGES_PER_BLOCK (%d <= %d && %d <= %d) fails\n",
+		       fs_info->chunk_root->nodesize,
+		       SCRUB_MAX_PAGES_PER_BLOCK,
+		       fs_info->chunk_root->sectorsize,
+		       SCRUB_MAX_PAGES_PER_BLOCK);
+		return -EINVAL;
+	}
+
+	ret = scrub_workers_get(fs_info, is_dev_replace);
 	if (ret)
 		return ret;
 
-	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
-	dev = btrfs_find_device(root, devid, NULL, NULL);
-	if (!dev || dev->missing) {
-		mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
-		scrub_workers_put(root);
+	mutex_lock(&fs_info->fs_devices->device_list_mutex);
+	dev = btrfs_find_device(fs_info, devid, NULL, NULL);
+	if (!dev || (dev->missing && !is_dev_replace)) {
+		mutex_unlock(&fs_info->fs_devices->device_list_mutex);
+		scrub_workers_put(fs_info);
 		return -ENODEV;
 	}
 	mutex_lock(&fs_info->scrub_lock);
 
-	if (!dev->in_fs_metadata) {
+	if (!dev->in_fs_metadata || dev->is_tgtdev_for_dev_replace) {
 		mutex_unlock(&fs_info->scrub_lock);
-		mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
-		scrub_workers_put(root);
-		return -ENODEV;
+		mutex_unlock(&fs_info->fs_devices->device_list_mutex);
+		scrub_workers_put(fs_info);
+		return -EIO;
 	}
 
-	if (dev->scrub_device) {
+	btrfs_dev_replace_lock(&fs_info->dev_replace);
+	if (dev->scrub_device ||
+	    (!is_dev_replace &&
+	     btrfs_dev_replace_is_ongoing(&fs_info->dev_replace))) {
+		btrfs_dev_replace_unlock(&fs_info->dev_replace);
 		mutex_unlock(&fs_info->scrub_lock);
-		mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
-		scrub_workers_put(root);
+		mutex_unlock(&fs_info->fs_devices->device_list_mutex);
+		scrub_workers_put(fs_info);
 		return -EINPROGRESS;
 	}
-	sdev = scrub_setup_dev(dev);
-	if (IS_ERR(sdev)) {
+	btrfs_dev_replace_unlock(&fs_info->dev_replace);
+	sctx = scrub_setup_ctx(dev, is_dev_replace);
+	if (IS_ERR(sctx)) {
 		mutex_unlock(&fs_info->scrub_lock);
-		mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
-		scrub_workers_put(root);
-		return PTR_ERR(sdev);
+		mutex_unlock(&fs_info->fs_devices->device_list_mutex);
+		scrub_workers_put(fs_info);
+		return PTR_ERR(sctx);
 	}
-	sdev->readonly = readonly;
-	dev->scrub_device = sdev;
+	sctx->readonly = readonly;
+	dev->scrub_device = sctx;
 
 	atomic_inc(&fs_info->scrubs_running);
 	mutex_unlock(&fs_info->scrub_lock);
-	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
+	mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 
-	down_read(&fs_info->scrub_super_lock);
-	ret = scrub_supers(sdev);
-	up_read(&fs_info->scrub_super_lock);
+	if (!is_dev_replace) {
+		down_read(&fs_info->scrub_super_lock);
+		ret = scrub_supers(sctx, dev);
+		up_read(&fs_info->scrub_super_lock);
+	}
 
 	if (!ret)
-		ret = scrub_enumerate_chunks(sdev, start, end);
+		ret = scrub_enumerate_chunks(sctx, dev, start, end,
+					     is_dev_replace);
 
-	wait_event(sdev->list_wait, atomic_read(&sdev->in_flight) == 0);
+	wait_event(sctx->list_wait, atomic_read(&sctx->bios_in_flight) == 0);
 	atomic_dec(&fs_info->scrubs_running);
 	wake_up(&fs_info->scrub_pause_wait);
 
-	wait_event(sdev->list_wait, atomic_read(&sdev->fixup_cnt) == 0);
+	wait_event(sctx->list_wait, atomic_read(&sctx->workers_pending) == 0);
 
 	if (progress)
-		memcpy(progress, &sdev->stat, sizeof(*progress));
+		memcpy(progress, &sctx->stat, sizeof(*progress));
 
 	mutex_lock(&fs_info->scrub_lock);
 	dev->scrub_device = NULL;
 	mutex_unlock(&fs_info->scrub_lock);
 
-	scrub_free_dev(sdev);
-	scrub_workers_put(root);
+	scrub_free_ctx(sctx);
+	scrub_workers_put(fs_info);
 
 	return ret;
 }
···
 	up_write(&root->fs_info->scrub_super_lock);
 }
 
-int __btrfs_scrub_cancel(struct btrfs_fs_info *fs_info)
+int btrfs_scrub_cancel(struct btrfs_fs_info *fs_info)
 {
-
 	mutex_lock(&fs_info->scrub_lock);
 	if (!atomic_read(&fs_info->scrubs_running)) {
 		mutex_unlock(&fs_info->scrub_lock);
···
 	return 0;
 }
 
-int btrfs_scrub_cancel(struct btrfs_root *root)
+int btrfs_scrub_cancel_dev(struct btrfs_fs_info *fs_info,
+			   struct btrfs_device *dev)
 {
-	return __btrfs_scrub_cancel(root->fs_info);
-}
-
-int btrfs_scrub_cancel_dev(struct btrfs_root *root, struct btrfs_device *dev)
-{
-	struct btrfs_fs_info *fs_info = root->fs_info;
-	struct scrub_dev *sdev;
+	struct scrub_ctx *sctx;
 
 	mutex_lock(&fs_info->scrub_lock);
-	sdev = dev->scrub_device;
-	if (!sdev) {
+	sctx = dev->scrub_device;
+	if (!sctx) {
 		mutex_unlock(&fs_info->scrub_lock);
 		return -ENOTCONN;
 	}
-	atomic_inc(&sdev->cancel_req);
+	atomic_inc(&sctx->cancel_req);
 	while (dev->scrub_device) {
 		mutex_unlock(&fs_info->scrub_lock);
 		wait_event(fs_info->scrub_pause_wait,
···
 	 * does not go away in cancel_dev. FIXME: find a better solution
 	 */
 	mutex_lock(&fs_info->fs_devices->device_list_mutex);
-	dev = btrfs_find_device(root, devid, NULL, NULL);
+	dev = btrfs_find_device(fs_info, devid, NULL, NULL);
 	if (!dev) {
 		mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 		return -ENODEV;
 	}
-	ret = btrfs_scrub_cancel_dev(root, dev);
+	ret = btrfs_scrub_cancel_dev(fs_info, dev);
 	mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 
 	return ret;
···
 			 struct btrfs_scrub_progress *progress)
 {
 	struct btrfs_device *dev;
-	struct scrub_dev *sdev = NULL;
+	struct scrub_ctx *sctx = NULL;
 
 	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
-	dev = btrfs_find_device(root, devid, NULL, NULL);
+	dev = btrfs_find_device(root->fs_info, devid, NULL, NULL);
 	if (dev)
-		sdev = dev->scrub_device;
-	if (sdev)
-		memcpy(progress, &sdev->stat, sizeof(*progress));
+		sctx = dev->scrub_device;
+	if (sctx)
+		memcpy(progress, &sctx->stat, sizeof(*progress));
 	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
 
-	return dev ? (sdev ? 0 : -ENOTCONN) : -ENODEV;
+	return dev ? (sctx ? 0 : -ENOTCONN) : -ENODEV;
+}
+
+static void scrub_remap_extent(struct btrfs_fs_info *fs_info,
+			       u64 extent_logical, u64 extent_len,
+			       u64 *extent_physical,
+			       struct btrfs_device **extent_dev,
+			       int *extent_mirror_num)
+{
+	u64 mapped_length;
+	struct btrfs_bio *bbio = NULL;
+	int ret;
+
+	mapped_length = extent_len;
+	ret = btrfs_map_block(fs_info, READ, extent_logical,
+			      &mapped_length, &bbio, 0);
+	if (ret || !bbio || mapped_length < extent_len ||
+	    !bbio->stripes[0].dev->bdev) {
+		kfree(bbio);
+		return;
+	}
+
+	*extent_physical = bbio->stripes[0].physical;
+	*extent_mirror_num = bbio->mirror_num;
+	*extent_dev = bbio->stripes[0].dev;
+	kfree(bbio);
+}
+
+static int scrub_setup_wr_ctx(struct scrub_ctx *sctx,
+			      struct scrub_wr_ctx *wr_ctx,
+			      struct btrfs_fs_info *fs_info,
+			      struct btrfs_device *dev,
+			      int is_dev_replace)
+{
+	WARN_ON(wr_ctx->wr_curr_bio != NULL);
+
+	mutex_init(&wr_ctx->wr_lock);
+	wr_ctx->wr_curr_bio = NULL;
+	if (!is_dev_replace)
+		return 0;
+
+	WARN_ON(!dev->bdev);
+	wr_ctx->pages_per_wr_bio = min_t(int, SCRUB_PAGES_PER_WR_BIO,
+					 bio_get_nr_vecs(dev->bdev));
+	wr_ctx->tgtdev = dev;
+	atomic_set(&wr_ctx->flush_all_writes, 0);
+	return 0;
+}
+
+static void scrub_free_wr_ctx(struct scrub_wr_ctx *wr_ctx)
+{
+	mutex_lock(&wr_ctx->wr_lock);
+	kfree(wr_ctx->wr_curr_bio);
+	wr_ctx->wr_curr_bio = NULL;
+	mutex_unlock(&wr_ctx->wr_lock);
+}
+
+static int copy_nocow_pages(struct scrub_ctx *sctx, u64 logical, u64 len,
+			    int mirror_num, u64 physical_for_dev_replace)
+{
+	struct scrub_copy_nocow_ctx *nocow_ctx;
+	struct btrfs_fs_info *fs_info = sctx->dev_root->fs_info;
+
+	nocow_ctx = kzalloc(sizeof(*nocow_ctx), GFP_NOFS);
+	if (!nocow_ctx) {
+		spin_lock(&sctx->stat_lock);
+		sctx->stat.malloc_errors++;
+		spin_unlock(&sctx->stat_lock);
+		return -ENOMEM;
+	}
+
+	scrub_pending_trans_workers_inc(sctx);
+
+	nocow_ctx->sctx = sctx;
+	nocow_ctx->logical = logical;
+	nocow_ctx->len = len;
+	nocow_ctx->mirror_num = mirror_num;
+	nocow_ctx->physical_for_dev_replace = physical_for_dev_replace;
+	nocow_ctx->work.func = copy_nocow_pages_worker;
+	btrfs_queue_worker(&fs_info->scrub_nocow_workers,
+			   &nocow_ctx->work);
+
+	return 0;
+}
+
+static void copy_nocow_pages_worker(struct btrfs_work *work)
+{
+	struct scrub_copy_nocow_ctx *nocow_ctx =
+		container_of(work, struct scrub_copy_nocow_ctx, work);
+	struct scrub_ctx *sctx = nocow_ctx->sctx;
+	u64 logical = nocow_ctx->logical;
+	u64 len = nocow_ctx->len;
+	int mirror_num = nocow_ctx->mirror_num;
+	u64 physical_for_dev_replace = nocow_ctx->physical_for_dev_replace;
+	int ret;
+	struct btrfs_trans_handle *trans = NULL;
+	struct btrfs_fs_info *fs_info;
+	struct btrfs_path *path;
+	struct btrfs_root *root;
+	int not_written = 0;
+
+	fs_info = sctx->dev_root->fs_info;
+	root = fs_info->extent_root;
+
+	path = btrfs_alloc_path();
+	if (!path) {
+		spin_lock(&sctx->stat_lock);
+		sctx->stat.malloc_errors++;
+		spin_unlock(&sctx->stat_lock);
+		not_written = 1;
+		goto out;
+	}
+
+	trans = btrfs_join_transaction(root);
+	if (IS_ERR(trans)) {
+		not_written = 1;
+		goto out;
+	}
+
+	ret = iterate_inodes_from_logical(logical, fs_info, path,
+					  copy_nocow_pages_for_inode,
+					  nocow_ctx);
+	if (ret != 0 && ret != -ENOENT) {
+		pr_warn("iterate_inodes_from_logical() failed: log %llu, phys %llu, len %llu, mir %llu, ret %d\n",
+			(unsigned long long)logical,
+			(unsigned long long)physical_for_dev_replace,
+			(unsigned long long)len,
+			(unsigned long long)mirror_num, ret);
+		not_written = 1;
+		goto out;
+	}
+
+out:
+	if (trans && !IS_ERR(trans))
+		btrfs_end_transaction(trans, root);
+	if (not_written)
+		btrfs_dev_replace_stats_inc(&fs_info->dev_replace.
+					    num_uncorrectable_read_errors);
+
+	btrfs_free_path(path);
+	kfree(nocow_ctx);
+
+	scrub_pending_trans_workers_dec(sctx);
+}
+
+static int copy_nocow_pages_for_inode(u64 inum, u64 offset, u64 root, void *ctx)
+{
+	unsigned long index;
+	struct scrub_copy_nocow_ctx *nocow_ctx = ctx;
+	int ret = 0;
+	struct btrfs_key key;
+	struct inode *inode = NULL;
+	struct btrfs_root *local_root;
+	u64 physical_for_dev_replace;
+	u64 len;
+	struct btrfs_fs_info *fs_info = nocow_ctx->sctx->dev_root->fs_info;
+
+	key.objectid = root;
+	key.type = BTRFS_ROOT_ITEM_KEY;
+	key.offset = (u64)-1;
+	local_root = btrfs_read_fs_root_no_name(fs_info, &key);
+	if (IS_ERR(local_root))
+		return PTR_ERR(local_root);
+
+	key.type = BTRFS_INODE_ITEM_KEY;
+	key.objectid = inum;
+	key.offset = 0;
+	inode = btrfs_iget(fs_info->sb, &key, local_root, NULL);
+	if (IS_ERR(inode))
+		return PTR_ERR(inode);
+
+	physical_for_dev_replace = nocow_ctx->physical_for_dev_replace;
+	len = nocow_ctx->len;
+	while (len >= PAGE_CACHE_SIZE) {
+		struct page *page = NULL;
+		int ret_sub;
+
+		index = offset >> PAGE_CACHE_SHIFT;
+
+		page = find_or_create_page(inode->i_mapping, index, GFP_NOFS);
+		if (!page) {
+			pr_err("find_or_create_page() failed\n");
+			ret = -ENOMEM;
+			goto next_page;
+		}
+
+		if (PageUptodate(page)) {
+			if (PageDirty(page))
+				goto next_page;
+		} else {
+			ClearPageError(page);
+			ret_sub = extent_read_full_page(&BTRFS_I(inode)->
+							 io_tree,
+							page, btrfs_get_extent,
+							nocow_ctx->mirror_num);
+			if (ret_sub) {
+				ret = ret_sub;
+				goto next_page;
+			}
+			wait_on_page_locked(page);
+			if (!PageUptodate(page)) {
+				ret = -EIO;
+				goto next_page;
+			}
+		}
+		ret_sub = write_page_nocow(nocow_ctx->sctx,
+					   physical_for_dev_replace, page);
+		if (ret_sub) {
+			ret = ret_sub;
+			goto next_page;
+		}
+
+next_page:
+		if (page) {
+			unlock_page(page);
+			put_page(page);
+		}
+		offset += PAGE_CACHE_SIZE;
+		physical_for_dev_replace += PAGE_CACHE_SIZE;
+		len -= PAGE_CACHE_SIZE;
+	}
+
+	if (inode)
+		iput(inode);
+	return ret;
+}
+
+static int write_page_nocow(struct scrub_ctx *sctx,
+			    u64 physical_for_dev_replace, struct page *page)
+{
+	struct bio *bio;
+	struct btrfs_device *dev;
+	int ret;
+	DECLARE_COMPLETION_ONSTACK(compl);
+
+	dev = sctx->wr_ctx.tgtdev;
+	if (!dev)
+		return -EIO;
+	if (!dev->bdev) {
+		printk_ratelimited(KERN_WARNING
+			"btrfs: scrub write_page_nocow(bdev == NULL) is unexpected!\n");
+		return -EIO;
+	}
+	bio = bio_alloc(GFP_NOFS, 1);
+	if (!bio) {
+		spin_lock(&sctx->stat_lock);
+		sctx->stat.malloc_errors++;
+		spin_unlock(&sctx->stat_lock);
+		return -ENOMEM;
+	}
+	bio->bi_private = &compl;
+	bio->bi_end_io = scrub_complete_bio_end_io;
+	bio->bi_size = 0;
+	bio->bi_sector = physical_for_dev_replace >> 9;
+	bio->bi_bdev = dev->bdev;
+	ret = bio_add_page(bio, page, PAGE_CACHE_SIZE, 0);
+	if (ret != PAGE_CACHE_SIZE) {
+leave_with_eio:
+		bio_put(bio);
+		btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_WRITE_ERRS);
+		return -EIO;
+	}
+	btrfsic_submit_bio(WRITE_SYNC, bio);
+	wait_for_completion(&compl);
+
+	if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
+		goto leave_with_eio;
+
+	bio_put(bio);
+	return 0;
 }

fs/btrfs/send.c

···
 	if (!path)
 		return -ENOMEM;
 
-	spin_lock(&send_root->root_times_lock);
+	spin_lock(&send_root->root_item_lock);
 	start_ctransid = btrfs_root_ctransid(&send_root->root_item);
-	spin_unlock(&send_root->root_times_lock);
+	spin_unlock(&send_root->root_item_lock);
 
 	key.objectid = BTRFS_FIRST_FREE_OBJECTID;
 	key.type = BTRFS_INODE_ITEM_KEY;
···
 	 * Make sure the tree has not changed after re-joining. We detect this
 	 * by comparing start_ctransid and ctransid. They should always match.
 	 */
-	spin_lock(&send_root->root_times_lock);
+	spin_lock(&send_root->root_item_lock);
 	ctransid = btrfs_root_ctransid(&send_root->root_item);
-	spin_unlock(&send_root->root_times_lock);
+	spin_unlock(&send_root->root_item_lock);
 
 	if (ctransid != start_ctransid) {
 		WARN(1, KERN_WARNING "btrfs: the root that you're trying to "

fs/btrfs/super.c

···
 #include "export.h"
 #include "compression.h"
 #include "rcu-string.h"
+#include "dev-replace.h"
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/btrfs.h>
···
 	if (fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR) {
 		sb->s_flags |= MS_RDONLY;
 		printk(KERN_INFO "btrfs is forced readonly\n");
-		__btrfs_scrub_cancel(fs_info);
+		/*
+		 * Note that a running device replace operation is not
+		 * canceled here although there is no way to update
+		 * the progress. It would add the risk of a deadlock,
+		 * therefore the canceling is ommited. The only penalty
+		 * is that some I/O remains active until the procedure
+		 * completes. The next time when the filesystem is
+		 * mounted writeable again, the device replace
+		 * operation continues.
+		 */
 //		WARN_ON(1);
 	}
 }
···
 	btrfs_set_max_workers(&fs_info->endio_freespace_worker, new_pool_size);
 	btrfs_set_max_workers(&fs_info->delayed_workers, new_pool_size);
 	btrfs_set_max_workers(&fs_info->readahead_workers, new_pool_size);
-	btrfs_set_max_workers(&fs_info->scrub_workers, new_pool_size);
+	btrfs_set_max_workers(&fs_info->scrub_wr_completion_workers,
+			      new_pool_size);
 }
 
 static int btrfs_remount(struct super_block *sb, int *flags, char *data)
···
 		return 0;
 
 	if (*flags & MS_RDONLY) {
+		/*
+		 * this also happens on 'umount -rf' or on shutdown, when
+		 * the filesystem is busy.
+		 */
 		sb->s_flags |= MS_RDONLY;
+
+		btrfs_dev_replace_suspend_for_unmount(fs_info);
+		btrfs_scrub_cancel(fs_info);
 
 		ret = btrfs_commit_super(root);
 		if (ret)
 			goto restore;
 	} else {
 		if (fs_info->fs_devices->rw_devices == 0) {
+			ret = -EACCES;
+			goto restore;
+		}
+
+		if (fs_info->fs_devices->missing_devices >
+		     fs_info->num_tolerated_disk_barrier_failures &&
+		    !(*flags & MS_RDONLY)) {
+			printk(KERN_WARNING
+			       "Btrfs: too many missing devices, writeable remount is not allowed\n");
 			ret = -EACCES;
 			goto restore;
 		}
···
 		if (ret)
 			goto restore;
 
+		ret = btrfs_resume_dev_replace_async(fs_info);
+		if (ret) {
+			pr_warn("btrfs: failed to resume dev_replace\n");
+			goto restore;
+		}
 		sb->s_flags &= ~MS_RDONLY;
 	}
 
···
 		min_stripe_size = BTRFS_STRIPE_LEN;
 
 	list_for_each_entry(device, &fs_devices->devices, dev_list) {
-		if (!device->in_fs_metadata || !device->bdev)
+		if (!device->in_fs_metadata || !device->bdev ||
+		    device->is_tgtdev_for_dev_replace)
 			continue;
 
 		avail_space = device->total_bytes - device->bytes_used;
···
 	if (err)
 		goto free_ordered_data;
 
-	err = btrfs_interface_init();
+	err = btrfs_auto_defrag_init();
 	if (err)
 		goto free_delayed_inode;
+
+	err = btrfs_interface_init();
+	if (err)
+		goto free_auto_defrag;
 
 	err = register_filesystem(&btrfs_fs_type);
 	if (err)
···
 
 unregister_ioctl:
 	btrfs_interface_exit();
+free_auto_defrag:
+	btrfs_auto_defrag_exit();
 free_delayed_inode:
 	btrfs_delayed_inode_exit();
 free_ordered_data:
···
 static void __exit exit_btrfs_fs(void)
 {
 	btrfs_destroy_cachep();
+	btrfs_auto_defrag_exit();
 	btrfs_delayed_inode_exit();
 	ordered_data_exit();
 	extent_map_exit();

fs/btrfs/transaction.c

···
 #include "tree-log.h"
 #include "inode-map.h"
 #include "volumes.h"
+#include "dev-replace.h"
 
 #define BTRFS_ROOT_TRANS_TAG 0
 
···
 	 * the log must never go across transaction boundaries.
 	 */
 	smp_mb();
-	if (!list_empty(&fs_info->tree_mod_seq_list)) {
-		printk(KERN_ERR "btrfs: tree_mod_seq_list not empty when "
+	if (!list_empty(&fs_info->tree_mod_seq_list))
+		WARN(1, KERN_ERR "btrfs: tree_mod_seq_list not empty when "
 			"creating a fresh transaction\n");
-		WARN_ON(1);
-	}
-	if (!RB_EMPTY_ROOT(&fs_info->tree_mod_log)) {
-		printk(KERN_ERR "btrfs: tree_mod_log rb tree not empty when "
+	if (!RB_EMPTY_ROOT(&fs_info->tree_mod_log))
+		WARN(1, KERN_ERR "btrfs: tree_mod_log rb tree not empty when "
 			"creating a fresh transaction\n");
-		WARN_ON(1);
-	}
 	atomic_set(&fs_info->tree_mod_seq, 0);
 
 	spin_lock_init(&cur_trans->commit_lock);
···
 	return 0;
 }
 
-static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
-						    u64 num_items, int type,
-						    int noflush)
+static struct btrfs_trans_handle *
+start_transaction(struct btrfs_root *root, u64 num_items, int type,
+		  enum btrfs_reserve_flush_enum flush)
 {
 	struct btrfs_trans_handle *h;
 	struct btrfs_transaction *cur_trans;
···
 		WARN_ON(type != TRANS_JOIN && type != TRANS_JOIN_NOLOCK);
 		h = current->journal_info;
 		h->use_count++;
+		WARN_ON(h->use_count > 2);
 		h->orig_rsv = h->block_rsv;
 		h->block_rsv = NULL;
 		goto got_it;
···
 		}
 
 		num_bytes = btrfs_calc_trans_metadata_size(root, num_items);
-		if (noflush)
-			ret = btrfs_block_rsv_add_noflush(root,
-						&root->fs_info->trans_block_rsv,
-						num_bytes);
-		else
-			ret = btrfs_block_rsv_add(root,
-						&root->fs_info->trans_block_rsv,
-						num_bytes);
+		ret = btrfs_block_rsv_add(root,
+					  &root->fs_info->trans_block_rsv,
+					  num_bytes, flush);
 		if (ret)
 			return ERR_PTR(ret);
 	}
···
 struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
 						   int num_items)
 {
-	return start_transaction(root, num_items, TRANS_START, 0);
+	return start_transaction(root, num_items, TRANS_START,
+				 BTRFS_RESERVE_FLUSH_ALL);
 }
 
-struct btrfs_trans_handle *btrfs_start_transaction_noflush(
+struct btrfs_trans_handle *btrfs_start_transaction_lflush(
 					struct btrfs_root *root, int num_items)
 {
-	return start_transaction(root, num_items, TRANS_START, 1);
+	return start_transaction(root, num_items, TRANS_START,
+				 BTRFS_RESERVE_FLUSH_LIMIT);
 }
 
 struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root)
···
 int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid)
 {
 	struct btrfs_transaction *cur_trans = NULL, *t;
-	int ret;
+	int ret = 0;
 
-	ret = 0;
 	if (transid) {
 		if (transid <= root->fs_info->last_trans_committed)
 			goto out;
 
+		ret = -EINVAL;
 		/* find specified transaction */
 		spin_lock(&root->fs_info->trans_lock);
 		list_for_each_entry(t, &root->fs_info->trans_list, list) {
 			if (t->transid == transid) {
 				cur_trans = t;
 				atomic_inc(&cur_trans->use_count);
+				ret = 0;
 				break;
 			}
-			if (t->transid > transid)
+			if (t->transid > transid) {
+				ret = 0;
 				break;
+			}
 		}
 		spin_unlock(&root->fs_info->trans_lock);
-		ret = -EINVAL;
+		/* The specified transaction doesn't exist */
 		if (!cur_trans)
-			goto out;  /* bad transid */
+			goto out;
 	} else {
 		/* find newest transaction that is committing | committed */
 		spin_lock(&root->fs_info->trans_lock);
···
 	}
 
 	wait_for_commit(root, cur_trans);
-
 	put_transaction(cur_trans);
-	ret = 0;
 out:
 	return ret;
 }
···
 		return ret;
 
 	ret = btrfs_run_dev_stats(trans, root->fs_info);
-	BUG_ON(ret);
+	WARN_ON(ret);
+	ret = btrfs_run_dev_replace(trans, root->fs_info);
+	WARN_ON(ret);
 
 	ret = btrfs_run_qgroups(trans, root->fs_info);
 	BUG_ON(ret);
···
 	down_write(&fs_info->extent_commit_sem);
 	switch_commit_root(fs_info->extent_root);
 	up_write(&fs_info->extent_commit_sem);
+
+	btrfs_after_dev_replace_commit(fs_info);
 
 	return 0;
 }
···
 	struct btrfs_fs_info *info = root->fs_info;
 	struct btrfs_trans_handle *trans;
 	int ret;
-	unsigned long nr;
 
 	if (xchg(&root->defrag_running, 1))
 		return 0;
···
 
 		ret = btrfs_defrag_leaves(trans, root, cacheonly);
 
-		nr = trans->blocks_used;
 		btrfs_end_transaction(trans, root);
-		btrfs_btree_balance_dirty(info->tree_root, nr);
+		btrfs_btree_balance_dirty(info->tree_root);
 		cond_resched();
 
 		if (btrfs_fs_closing(root->fs_info) || ret != -EAGAIN)
···
 	btrfs_reloc_pre_snapshot(trans, pending, &to_reserve);
 
 	if (to_reserve > 0) {
-		ret = btrfs_block_rsv_add_noflush(root, &pending->block_rsv,
-						  to_reserve);
+		ret = btrfs_block_rsv_add(root, &pending->block_rsv,
+					  to_reserve,
+					  BTRFS_RESERVE_NO_FLUSH);
 		if (ret) {
 			pending->error = ret;
 			goto no_free_objectid;
···
 				    parent_inode, &key,
 				    BTRFS_FT_DIR, index);
 	/* We have check then name at the beginning, so it is impossible. */
-	BUG_ON(ret == -EEXIST);
+	BUG_ON(ret == -EEXIST || ret == -EOVERFLOW);
 	if (ret) {
 		btrfs_abort_transaction(trans, root, ret);
 		goto fail;
···
 	 * We've got freeze protection passed with the transaction.
 	 * Tell lockdep about it.
 	 */
-	rwsem_acquire_read(
-		&ac->root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
-		0, 1, _THIS_IP_);
+	if (ac->newtrans->type < TRANS_JOIN_NOLOCK)
+		rwsem_acquire_read(
+		     &ac->root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
+		     0, 1, _THIS_IP_);
 
 	current->journal_info = ac->newtrans;
 
···
 	 * Tell lockdep we've released the freeze rwsem, since the
 	 * async commit thread will be the one to unlock it.
 	 */
-	rwsem_release(&root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
-		      1, _THIS_IP_);
+	if (trans->type < TRANS_JOIN_NOLOCK)
+		rwsem_release(
+			&root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
+			1, _THIS_IP_);
 
 	schedule_delayed_work(&ac->work, 0);
 
···
 	kmem_cache_free(btrfs_trans_handle_cachep, trans);
 }
 
+static int btrfs_flush_all_pending_stuffs(struct btrfs_trans_handle *trans,
+					  struct btrfs_root *root)
+{
+	int flush_on_commit = btrfs_test_opt(root, FLUSHONCOMMIT);
+	int snap_pending = 0;
+	int ret;
+
+	if (!flush_on_commit) {
+		spin_lock(&root->fs_info->trans_lock);
+		if (!list_empty(&trans->transaction->pending_snapshots))
+			snap_pending = 1;
+		spin_unlock(&root->fs_info->trans_lock);
+	}
+
+	if (flush_on_commit || snap_pending) {
+		btrfs_start_delalloc_inodes(root, 1);
+		btrfs_wait_ordered_extents(root, 1);
+	}
+
+	ret = btrfs_run_delayed_items(trans, root);
+	if (ret)
+		return ret;
+
+	/*
+	 * running the delayed items may have added new refs. account
+	 * them now so that they hinder processing of more delayed refs
+	 * as little as possible.
+	 */
+	btrfs_delayed_refs_qgroup_accounting(trans, root->fs_info);
+
+	/*
+	 * rename don't use btrfs_join_transaction, so, once we
+	 * set the transaction to blocked above, we aren't going
+	 * to get any new ordered operations.  We can safely run
+	 * it here and no for sure that nothing new will be added
+	 * to the list
+	 */
+	btrfs_run_ordered_operations(root, 1);
+
+	return 0;
+}
+
 /*
  * btrfs_transaction state sequence:
  *    in_commit = 0, blocked = 0  (initial)
···
 	struct btrfs_transaction *cur_trans = trans->transaction;
 	struct btrfs_transaction *prev_trans = NULL;
 	DEFINE_WAIT(wait);
-	int ret = -EIO;
+	int ret;
 	int should_grow = 0;
 	unsigned long now = get_seconds();
-	int flush_on_commit = btrfs_test_opt(root, FLUSHONCOMMIT);
 
-	btrfs_run_ordered_operations(root, 0);
-
-	if (cur_trans->aborted)
+	ret = btrfs_run_ordered_operations(root, 0);
+	if (ret) {
+		btrfs_abort_transaction(trans, root, ret);
 		goto cleanup_transaction;
+	}
+
+	if (cur_trans->aborted) {
+		ret = cur_trans->aborted;
+		goto cleanup_transaction;
+	}
 
 	/* make a pass through all the delayed refs we have so far
 	 * any runnings procs may add more while we are here
···
 		should_grow = 1;
 
 	do {
-		int snap_pending = 0;
-
 		joined = cur_trans->num_joined;
-		if (!list_empty(&trans->transaction->pending_snapshots))
-			snap_pending = 1;
 
 		WARN_ON(cur_trans != trans->transaction);
 
-		if (flush_on_commit || snap_pending) {
-			btrfs_start_delalloc_inodes(root, 1);
-			btrfs_wait_ordered_extents(root, 1);
-		}
-
-		ret = btrfs_run_delayed_items(trans, root);
+		ret = btrfs_flush_all_pending_stuffs(trans, root);
 		if (ret)
 			goto cleanup_transaction;
-
-		/*
-		 * running the delayed items may have added new refs. account
-		 * them now so that they hinder processing of more delayed refs
-		 * as little as possible.
-		 */
-		btrfs_delayed_refs_qgroup_accounting(trans, root->fs_info);
-
-		/*
-		 * rename don't use btrfs_join_transaction, so, once we
-		 * set the transaction to blocked above, we aren't going
-		 * to get any new ordered operations.  We can safely run
-		 * it here and no for sure that nothing new will be added
-		 * to the list
-		 */
-		btrfs_run_ordered_operations(root, 1);
 
 		prepare_to_wait(&cur_trans->writer_wait, &wait,
 				TASK_UNINTERRUPTIBLE);
···
 		finish_wait(&cur_trans->writer_wait, &wait);
 	} while (atomic_read(&cur_trans->num_writers) > 1 ||
 		 (should_grow && cur_trans->num_joined != joined));
+
+	ret = btrfs_flush_all_pending_stuffs(trans, root);
+	if (ret)
+		goto cleanup_transaction;
 
 	/*
 	 * Ok now we need to make sure to block out any other joins while we

fs/btrfs/transaction.h

···
 			  struct btrfs_root *root);
 struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
 						   int num_items);
-struct btrfs_trans_handle *btrfs_start_transaction_noflush(
+struct btrfs_trans_handle *btrfs_start_transaction_lflush(
 					struct btrfs_root *root, int num_items);
 struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root);
 struct btrfs_trans_handle *btrfs_join_transaction_nolock(struct btrfs_root *root);

fs/btrfs/tree-log.c

···
 			    struct btrfs_inode_item *item,
 			    struct inode *inode, int log_inode_only)
 {
-	btrfs_set_inode_uid(leaf, item, i_uid_read(inode));
-	btrfs_set_inode_gid(leaf, item, i_gid_read(inode));
-	btrfs_set_inode_mode(leaf, item, inode->i_mode);
-	btrfs_set_inode_nlink(leaf, item, inode->i_nlink);
+	struct btrfs_map_token token;
 
-	btrfs_set_timespec_sec(leaf, btrfs_inode_atime(item),
-			       inode->i_atime.tv_sec);
-	btrfs_set_timespec_nsec(leaf, btrfs_inode_atime(item),
-				inode->i_atime.tv_nsec);
-
-	btrfs_set_timespec_sec(leaf, btrfs_inode_mtime(item),
-			       inode->i_mtime.tv_sec);
-	btrfs_set_timespec_nsec(leaf, btrfs_inode_mtime(item),
-				inode->i_mtime.tv_nsec);
-
-	btrfs_set_timespec_sec(leaf, btrfs_inode_ctime(item),
-			       inode->i_ctime.tv_sec);
-	btrfs_set_timespec_nsec(leaf, btrfs_inode_ctime(item),
-				inode->i_ctime.tv_nsec);
-
-	btrfs_set_inode_nbytes(leaf, item, inode_get_bytes(inode));
-
-	btrfs_set_inode_sequence(leaf, item, inode->i_version);
-	btrfs_set_inode_transid(leaf, item, trans->transid);
-	btrfs_set_inode_rdev(leaf, item, inode->i_rdev);
-	btrfs_set_inode_flags(leaf, item, BTRFS_I(inode)->flags);
-	btrfs_set_inode_block_group(leaf, item, 0);
+	btrfs_init_map_token(&token);
 
 	if (log_inode_only) {
 		/* set the generation to zero so the recover code
···
 		 * just to say 'this inode exists' and a logging
 		 * to say 'update this inode with these values'
 		 */
-		btrfs_set_inode_generation(leaf, item, 0);
-		btrfs_set_inode_size(leaf, item, 0);
+		btrfs_set_token_inode_generation(leaf, item, 0, &token);
+		btrfs_set_token_inode_size(leaf, item, 0, &token);
 	} else {
-		btrfs_set_inode_generation(leaf, item,
-					   BTRFS_I(inode)->generation);
-		btrfs_set_inode_size(leaf, item, inode->i_size);
+		btrfs_set_token_inode_generation(leaf, item,
+						 BTRFS_I(inode)->generation,
+						 &token);
+		btrfs_set_token_inode_size(leaf, item, inode->i_size, &token);
 	}
 
+	btrfs_set_token_inode_uid(leaf, item, i_uid_read(inode), &token);
+	btrfs_set_token_inode_gid(leaf, item, i_gid_read(inode), &token);
+	btrfs_set_token_inode_mode(leaf, item, inode->i_mode, &token);
+	btrfs_set_token_inode_nlink(leaf, item, inode->i_nlink, &token);
+
+	btrfs_set_token_timespec_sec(leaf, btrfs_inode_atime(item),
+				     inode->i_atime.tv_sec, &token);
+	btrfs_set_token_timespec_nsec(leaf, btrfs_inode_atime(item),
+				      inode->i_atime.tv_nsec, &token);
+
+	btrfs_set_token_timespec_sec(leaf, btrfs_inode_mtime(item),
+				     inode->i_mtime.tv_sec, &token);
+	btrfs_set_token_timespec_nsec(leaf, btrfs_inode_mtime(item),
+				      inode->i_mtime.tv_nsec, &token);
+
+	btrfs_set_token_timespec_sec(leaf, btrfs_inode_ctime(item),
+				     inode->i_ctime.tv_sec, &token);
+	btrfs_set_token_timespec_nsec(leaf, btrfs_inode_ctime(item),
+				      inode->i_ctime.tv_nsec, &token);
+
+	btrfs_set_token_inode_nbytes(leaf, item, inode_get_bytes(inode),
+				     &token);
+
+	btrfs_set_token_inode_sequence(leaf, item, inode->i_version, &token);
+	btrfs_set_token_inode_transid(leaf, item, trans->transid, &token);
+	btrfs_set_token_inode_rdev(leaf, item, inode->i_rdev, &token);
+	btrfs_set_token_inode_flags(leaf, item, BTRFS_I(inode)->flags, &token);
+	btrfs_set_token_inode_block_group(leaf, item, 0, &token);
+}
+
+static int log_inode_item(struct btrfs_trans_handle *trans,
+			  struct btrfs_root *log, struct btrfs_path *path,
+			  struct inode *inode)
+{
+	struct btrfs_inode_item *inode_item;
+	struct btrfs_key key;
+	int ret;
+
+	memcpy(&key, &BTRFS_I(inode)->location, sizeof(key));
+	ret = btrfs_insert_empty_item(trans, log, path, &key,
+				      sizeof(*inode_item));
+	if (ret && ret != -EEXIST)
+		return ret;
+	inode_item = btrfs_item_ptr(path->nodes[0], path->slots[0],
+				    struct btrfs_inode_item);
+	fill_inode_item(trans, path->nodes[0], inode_item, inode, 0);
+	btrfs_release_path(path);
+	return 0;
 }
 
 static noinline int copy_items(struct btrfs_trans_handle *trans,
···
 	return 0;
 }
 
-struct log_args {
-	struct extent_buffer *src;
-	u64 next_offset;
-	int start_slot;
-	int nr;
-};
+static int drop_adjacent_extents(struct btrfs_trans_handle *trans,
+				 struct btrfs_root *root, struct inode *inode,
+				 struct extent_map *em,
+				 struct btrfs_path *path)
+{
+	struct btrfs_file_extent_item *fi;
+	struct extent_buffer *leaf;
+	struct btrfs_key key, new_key;
+	struct btrfs_map_token token;
+	u64 extent_end;
+	u64 extent_offset = 0;
+	int extent_type;
+	int del_slot = 0;
+	int del_nr = 0;
+	int ret = 0;
+
+	while (1) {
+		btrfs_init_map_token(&token);
+		leaf = path->nodes[0];
+		path->slots[0]++;
+		if (path->slots[0] >= btrfs_header_nritems(leaf)) {
+			if (del_nr) {
+				ret = btrfs_del_items(trans, root, path,
+						      del_slot, del_nr);
+				if (ret)
+					return ret;
+				del_nr = 0;
+			}
+
+			ret = btrfs_next_leaf_write(trans, root, path, 1);
+			if (ret < 0)
+				return ret;
+			if (ret > 0)
+				return 0;
+			leaf = path->nodes[0];
+		}
+
+		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+		if (key.objectid != btrfs_ino(inode) ||
+		    key.type != BTRFS_EXTENT_DATA_KEY ||
+		    key.offset >= em->start + em->len)
+			break;
+
+		fi = btrfs_item_ptr(leaf, path->slots[0],
+				    struct btrfs_file_extent_item);
+		extent_type = btrfs_token_file_extent_type(leaf, fi, &token);
+		if (extent_type == BTRFS_FILE_EXTENT_REG ||
+		    extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
+			extent_offset = btrfs_token_file_extent_offset(leaf,
+								fi, &token);
+			extent_end = key.offset +
+				btrfs_token_file_extent_num_bytes(leaf, fi,
+								  &token);
+		} else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
+			extent_end = key.offset +
+				btrfs_file_extent_inline_len(leaf, fi);
+		} else {
+			BUG();
+		}
+
+		if (extent_end <= em->len + em->start) {
+			if (!del_nr) {
+				del_slot = path->slots[0];
+			}
+			del_nr++;
+			continue;
+		}
+
+		/*
+		 * Ok so we'll ignore previous items if we log a new extent,
+		 * which can lead to overlapping extents, so if we have an
+		 * existing extent we want to adjust we _have_ to check the next
+		 * guy to make sure we even need this extent anymore, this keeps
+		 * us from panicing in set_item_key_safe.
+		 */
+		if (path->slots[0] < btrfs_header_nritems(leaf) - 1) {
+			struct btrfs_key tmp_key;
+
+			btrfs_item_key_to_cpu(leaf, &tmp_key,
+					      path->slots[0] + 1);
+			if (tmp_key.objectid == btrfs_ino(inode) &&
+			    tmp_key.type == BTRFS_EXTENT_DATA_KEY &&
+			    tmp_key.offset <= em->start + em->len) {
+				if (!del_nr)
+					del_slot = path->slots[0];
+				del_nr++;
+				continue;
+			}
+		}
+
+		BUG_ON(extent_type == BTRFS_FILE_EXTENT_INLINE);
+		memcpy(&new_key, &key, sizeof(new_key));
+		new_key.offset = em->start + em->len;
+		btrfs_set_item_key_safe(trans, root, path, &new_key);
+		extent_offset += em->start + em->len - key.offset;
+		btrfs_set_token_file_extent_offset(leaf, fi, extent_offset,
+						   &token);
+		btrfs_set_token_file_extent_num_bytes(leaf, fi, extent_end -
+						      (em->start + em->len),
+						      &token);
+		btrfs_mark_buffer_dirty(leaf);
+	}
+
+	if (del_nr)
+		ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
+
+	return ret;
+}
 
 static int log_one_extent(struct btrfs_trans_handle *trans,
 			  struct inode *inode, struct btrfs_root *root,
-			  struct extent_map *em, struct btrfs_path *path,
-			  struct btrfs_path *dst_path, struct log_args *args)
+			  struct extent_map *em, struct btrfs_path *path)
 {
 	struct btrfs_root *log = root->log_root;
 	struct btrfs_file_extent_item *fi;
+	struct extent_buffer *leaf;
+	struct list_head ordered_sums;
+	struct btrfs_map_token token;
 	struct btrfs_key key;
-	u64 start = em->mod_start;
-	u64 search_start = start;
-	u64 len = em->mod_len;
-	u64 num_bytes;
-	int nritems;
+	u64 csum_offset = em->mod_start - em->start;
+	u64 csum_len = em->mod_len;
+	u64 extent_offset = em->start - em->orig_start;
+	u64 block_len;
 	int ret;
+	bool skip_csum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
 
-	if (BTRFS_I(inode)->logged_trans == trans->transid) {
-		ret = __btrfs_drop_extents(trans, log, inode, dst_path, start,
-					   start + len, NULL, 0);
-		if (ret)
-			return ret;
+	INIT_LIST_HEAD(&ordered_sums);
+	btrfs_init_map_token(&token);
+	key.objectid = btrfs_ino(inode);
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = em->start;
+	path->really_keep_locks = 1;
+
+	ret = btrfs_insert_empty_item(trans, log, path, &key, sizeof(*fi));
+	if (ret && ret != -EEXIST) {
+		path->really_keep_locks = 0;
+		return ret;
+	}
+	leaf = path->nodes[0];
+	fi = btrfs_item_ptr(leaf, path->slots[0],
+			    struct btrfs_file_extent_item);
+	btrfs_set_token_file_extent_generation(leaf, fi, em->generation,
+					       &token);
+	if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) {
+		skip_csum = true;
+		btrfs_set_token_file_extent_type(leaf, fi,
+						 BTRFS_FILE_EXTENT_PREALLOC,
+						 &token);
+	} else {
+		btrfs_set_token_file_extent_type(leaf, fi,
+						 BTRFS_FILE_EXTENT_REG,
+						 &token);
+		if (em->block_start == 0)
+			skip_csum = true;
 	}
 
-	while (len) {
-		if (args->nr)
-			goto next_slot;
-again:
-		key.objectid = btrfs_ino(inode);
-		key.type = BTRFS_EXTENT_DATA_KEY;
-		key.offset = search_start;
-
-		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-		if (ret < 0)
-			return ret;
-
-		if (ret) {
-			/*
-			 * A rare case were we can have an em for a section of a
-			 * larger extent so we need to make sure that this em
-			 * falls within the extent we've found.  If not we just
-			 * bail and go back to ye-olde way of doing things but
-			 * it happens often enough in testing that we need to do
-			 * this dance to make sure.
-			 */
-			do {
-				if (path->slots[0] == 0) {
-					btrfs_release_path(path);
-					if (search_start == 0)
-						return -ENOENT;
-					search_start--;
-					goto again;
-				}
-
-				path->slots[0]--;
-				btrfs_item_key_to_cpu(path->nodes[0], &key,
-						      path->slots[0]);
-				if (key.objectid != btrfs_ino(inode) ||
-				    key.type != BTRFS_EXTENT_DATA_KEY) {
-					btrfs_release_path(path);
-					return -ENOENT;
-				}
-			} while (key.offset > start);
-
-			fi = btrfs_item_ptr(path->nodes[0], path->slots[0],
-					    struct btrfs_file_extent_item);
-			num_bytes = btrfs_file_extent_num_bytes(path->nodes[0],
-								fi);
-			if (key.offset + num_bytes <= start) {
-				btrfs_release_path(path);
-				return -ENOENT;
-			}
-		}
-		args->src = path->nodes[0];
-next_slot:
-		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
-		fi = btrfs_item_ptr(args->src, path->slots[0],
-				    struct btrfs_file_extent_item);
-		if (args->nr &&
-		    args->start_slot + args->nr == path->slots[0]) {
-			args->nr++;
-		} else if (args->nr) {
-			ret = copy_items(trans, inode, dst_path, args->src,
-					 args->start_slot, args->nr,
-					 LOG_INODE_ALL);
-			if (ret)
-				return ret;
-			args->nr = 1;
-			args->start_slot = path->slots[0];
-		} else if (!args->nr) {
-			args->nr = 1;
-			args->start_slot = path->slots[0];
-		}
-		nritems = btrfs_header_nritems(path->nodes[0]);
-		path->slots[0]++;
-		num_bytes = btrfs_file_extent_num_bytes(args->src, fi);
-		if (len < num_bytes) {
-			/* I _think_ this is ok, envision we write to a
-			 * preallocated space that is adjacent to a previously
-			 * written preallocated space that gets merged when we
-			 * mark this preallocated space written.  If we do not
-			 * have the adjacent extent in cache then when we copy
-			 * this extent it could end up being larger than our EM
-			 * thinks it is, which is a-ok, so just set len to 0.
-			 */
-			len = 0;
-		} else {
-			len -= num_bytes;
-		}
-		start = key.offset + num_bytes;
-		args->next_offset = start;
-		search_start = start;
-
-		if (path->slots[0] < nritems) {
-			if (len)
-				goto next_slot;
-			break;
-		}
-
-		if (args->nr) {
-			ret = copy_items(trans, inode, dst_path, args->src,
-					 args->start_slot, args->nr,
-					 LOG_INODE_ALL);
-			if (ret)
-				return ret;
-			args->nr = 0;
-			btrfs_release_path(path);
-		}
+	block_len = max(em->block_len, em->orig_block_len);
+	if (em->compress_type != BTRFS_COMPRESS_NONE) {
+		btrfs_set_token_file_extent_disk_bytenr(leaf, fi,
+							em->block_start,
+							&token);
+		btrfs_set_token_file_extent_disk_num_bytes(leaf, fi, block_len,
+							   &token);
+	} else if (em->block_start < EXTENT_MAP_LAST_BYTE) {
+		btrfs_set_token_file_extent_disk_bytenr(leaf, fi,
+							em->block_start -
+							extent_offset, &token);
+		btrfs_set_token_file_extent_disk_num_bytes(leaf, fi, block_len,
+							   &token);
+	} else {
+		btrfs_set_token_file_extent_disk_bytenr(leaf, fi, 0, &token);
+		btrfs_set_token_file_extent_disk_num_bytes(leaf, fi, 0,
+							   &token);
 	}
 
-	return 0;
+	btrfs_set_token_file_extent_offset(leaf, fi,
+					   em->start - em->orig_start,
+					   &token);
+	btrfs_set_token_file_extent_num_bytes(leaf, fi, em->len, &token);
+	btrfs_set_token_file_extent_ram_bytes(leaf, fi, em->len, &token);
+	btrfs_set_token_file_extent_compression(leaf, fi, em->compress_type,
+						&token);
+	btrfs_set_token_file_extent_encryption(leaf, fi, 0, &token);
+	btrfs_set_token_file_extent_other_encoding(leaf, fi, 0, &token);
+	btrfs_mark_buffer_dirty(leaf);
+
+	/*
+	 * Have to check the extent to the right of us to make sure it doesn't
+	 * fall in our current range.  We're ok if the previous extent is in our
+	 * range since the recovery stuff will run us in key order and thus just
+	 * drop the part we overwrote.
+	 */
+	ret = drop_adjacent_extents(trans, log, inode, em, path);
+	btrfs_release_path(path);
+	path->really_keep_locks = 0;
+	if (ret) {
+		return ret;
+	}
+
+	if (skip_csum)
+		return 0;
+
+	/* block start is already adjusted for the file extent offset. */
+	ret = btrfs_lookup_csums_range(log->fs_info->csum_root,
+				       em->block_start + csum_offset,
+				       em->block_start + csum_offset +
+				       csum_len - 1, &ordered_sums, 0);
+	if (ret)
+		return ret;
+
+	while (!list_empty(&ordered_sums)) {
+		struct btrfs_ordered_sum *sums = list_entry(ordered_sums.next,
+						   struct btrfs_ordered_sum,
+						   list);
+		if (!ret)
+			ret = btrfs_csum_file_blocks(trans, log, sums);
+		list_del(&sums->list);
+		kfree(sums);
+	}
+
+	return ret;
 }
 
 static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans,
 				     struct btrfs_root *root,
 				     struct inode *inode,
-				     struct btrfs_path *path,
-				     struct btrfs_path *dst_path)
+				     struct btrfs_path *path)
 {
-	struct log_args args;
 	struct extent_map *em, *n;
 	struct list_head extents;
 	struct extent_map_tree *tree = &BTRFS_I(inode)->extent_tree;
···
 	int ret = 0;
 
 	INIT_LIST_HEAD(&extents);
-
-	memset(&args, 0, sizeof(args));
 
 	write_lock(&tree->lock);
 	test_gen = root->fs_info->last_trans_committed;
···
 
 		write_unlock(&tree->lock);
 
-		/*
-		 * If the previous EM and the last extent we left off on aren't
-		 * sequential then we need to copy the items we have and redo
-		 * our search
-		 */
-		if (args.nr && em->mod_start != args.next_offset) {
-			ret = copy_items(trans, inode, dst_path, args.src,
-					 args.start_slot, args.nr,
-					 LOG_INODE_ALL);
-			if (ret) {
-				free_extent_map(em);
-				write_lock(&tree->lock);
-				continue;
-			}
-			btrfs_release_path(path);
-			args.nr = 0;
-		}
-
-		ret = log_one_extent(trans, inode, root, em, path, dst_path, &args);
+		ret = log_one_extent(trans, inode, root, em, path);
 		free_extent_map(em);
 		write_lock(&tree->lock);
 	}
 	WARN_ON(!list_empty(&extents));
 	write_unlock(&tree->lock);
 
-	if (!ret && args.nr)
-		ret = copy_items(trans, inode, dst_path, args.src,
-				 args.start_slot, args.nr, LOG_INODE_ALL);
 	btrfs_release_path(path);
 	return ret;
 }
···
 
 
 	/* today the code can only do partial logging of directories */
-	if (inode_only == LOG_INODE_EXISTS || S_ISDIR(inode->i_mode))
+	if (S_ISDIR(inode->i_mode) ||
+	    (!test_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
+		       &BTRFS_I(inode)->runtime_flags) &&
+	     inode_only == LOG_INODE_EXISTS))
 		max_key.type = BTRFS_XATTR_ITEM_KEY;
 	else
 		max_key.type = (u8)-1;
···
 	} else {
 		if (test_and_clear_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
 				       &BTRFS_I(inode)->runtime_flags)) {
+			clear_bit(BTRFS_INODE_COPY_EVERYTHING,
+				  &BTRFS_I(inode)->runtime_flags);
 			ret = btrfs_truncate_inode_items(trans, log,
 							 inode, 0, 0);
-		} else {
-			fast_search = true;
+		} else if (test_and_clear_bit(BTRFS_INODE_COPY_EVERYTHING,
+					      &BTRFS_I(inode)->runtime_flags)) {
+			if (inode_only == LOG_INODE_ALL)
+				fast_search = true;
 			max_key.type = BTRFS_XATTR_ITEM_KEY;
 			ret = drop_objectid_items(trans, log, path, ino,
-						  BTRFS_XATTR_ITEM_KEY);
+						  max_key.type);
+		} else {
+			if (inode_only == LOG_INODE_ALL)
+				fast_search = true;
+			ret = log_inode_item(trans, log, dst_path, inode);
+			if (ret) {
+				err = ret;
+				goto out_unlock;
+			}
+			goto log_extents;
 		}
+
 	}
 	if (ret) {
 		err = ret;
···
 		ins_nr = 0;
 	}
 
+log_extents:
 	if (fast_search) {
-		btrfs_release_path(path);
 		btrfs_release_path(dst_path);
-		ret = btrfs_log_changed_extents(trans, root, inode, path,
-						dst_path);
+		ret = btrfs_log_changed_extents(trans, root, inode, dst_path);
 		if (ret) {
 			err = ret;
 			goto out_unlock;
···
 		struct extent_map_tree *tree = &BTRFS_I(inode)->extent_tree;
 		struct extent_map *em, *n;
 
+		write_lock(&tree->lock);
 		list_for_each_entry_safe(em, n, &tree->modified_extents, list)
 			list_del_init(&em->list);
+		write_unlock(&tree->lock);
 	}
 
 	if (inode_only == LOG_INODE_ALL && S_ISDIR(inode->i_mode)) {

fs/btrfs/volumes.c

···
 #include <linux/capability.h>
 #include <linux/ratelimit.h>
 #include <linux/kthread.h>
-#include <asm/div64.h>
 #include "compat.h"
 #include "ctree.h"
 #include "extent_map.h"
···
 #include "async-thread.h"
 #include "check-integrity.h"
 #include "rcu-string.h"
+#include "math.h"
+#include "dev-replace.h"
 
 static int init_first_rw_device(struct btrfs_trans_handle *trans,
 				struct btrfs_root *root,
···
 		kfree(device);
 	}
 	kfree(fs_devices);
+}
+
+static void btrfs_kobject_uevent(struct block_device *bdev,
+				 enum kobject_action action)
+{
+	int ret;
+
+	ret = kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, action);
+	if (ret)
+		pr_warn("Sending event '%d' to kobject: '%s' (%p): failed\n",
+			action,
+			kobject_name(&disk_to_dev(bdev->bd_disk)->kobj),
+			&disk_to_dev(bdev->bd_disk)->kobj);
 }
 
 void btrfs_cleanup_fs_uuids(void)
···
 			return fs_devices;
 	}
 	return NULL;
+}
+
+static int
+btrfs_get_bdev_and_sb(const char *device_path, fmode_t flags, void *holder,
+		      int flush, struct block_device **bdev,
+		      struct buffer_head **bh)
+{
+	int ret;
+
+	*bdev = blkdev_get_by_path(device_path, flags, holder);
+
+	if (IS_ERR(*bdev)) {
+		ret = PTR_ERR(*bdev);
+		printk(KERN_INFO "btrfs: open %s failed\n", device_path);
+		goto error;
+	}
+
+	if (flush)
+		filemap_write_and_wait((*bdev)->bd_inode->i_mapping);
+	ret = set_blocksize(*bdev, 4096);
+	if (ret) {
+		blkdev_put(*bdev, flags);
+		goto error;
+	}
+	invalidate_bdev(*bdev);
+	*bh = btrfs_read_dev_super(*bdev);
+	if (!*bh) {
+		ret = -EINVAL;
+		blkdev_put(*bdev, flags);
+		goto error;
+	}
+
+	return 0;
+
+error:
+	*bdev = NULL;
+	*bh = NULL;
+	return ret;
 }
 
 static void requeue_list(struct btrfs_pending_bios *pending_bios,
···
 	return ERR_PTR(-ENOMEM);
 }
 
-void btrfs_close_extra_devices(struct btrfs_fs_devices *fs_devices)
+void btrfs_close_extra_devices(struct btrfs_fs_info *fs_info,
+			       struct btrfs_fs_devices *fs_devices, int step)
 {
 	struct btrfs_device *device, *next;
 
···
 	/* This is the initialized path, it is safe to release the devices. */
 	list_for_each_entry_safe(device, next, &fs_devices->devices, dev_list) {
 		if (device->in_fs_metadata) {
-			if (!latest_transid ||
-			    device->generation > latest_transid) {
+			if (!device->is_tgtdev_for_dev_replace &&
+			    (!latest_transid ||
+			     device->generation > latest_transid)) {
 				latest_devid = device->devid;
 				latest_transid = device->generation;
 				latest_bdev = device->bdev;
···
 			continue;
 		}
 
+		if (device->devid == BTRFS_DEV_REPLACE_DEVID) {
+			/*
+			 * In the first step, keep the device which has
+			 * the correct fsid and the devid that is used
+			 * for the dev_replace procedure.
+			 * In the second step, the dev_replace state is
+			 * read from the device tree and it is known
+			 * whether the procedure is really active or
+			 * not, which means whether this device is
+			 * used or whether it should be removed.
+			 */
+			if (step == 0 || device->is_tgtdev_for_dev_replace) {
+				continue;
+			}
+		}
 		if (device->bdev) {
 			blkdev_put(device->bdev, device->mode);
 			device->bdev = NULL;
···
 		if (device->writeable) {
 			list_del_init(&device->dev_alloc_list);
 			device->writeable = 0;
-			fs_devices->rw_devices--;
+			if (!device->is_tgtdev_for_dev_replace)
+				fs_devices->rw_devices--;
 		}
 		list_del_init(&device->dev_list);
 		fs_devices->num_devices--;
···
 		if (device->bdev)
 			fs_devices->open_devices--;
 
-		if (device->writeable) {
+		if (device->writeable && !device->is_tgtdev_for_dev_replace) {
 			list_del_init(&device->dev_alloc_list);
 			fs_devices->rw_devices--;
 		}
···
 		if (!device->name)
 			continue;
 
-		bdev = blkdev_get_by_path(device->name->str, flags, holder);
-		if (IS_ERR(bdev)) {
-			printk(KERN_INFO "btrfs: open %s failed\n", device->name->str);
-			goto error;
-		}
-		filemap_write_and_wait(bdev->bd_inode->i_mapping);
-		invalidate_bdev(bdev);
-		set_blocksize(bdev, 4096);
-
-		bh = btrfs_read_dev_super(bdev);
-		if (!bh)
-			goto error_close;
+		ret = btrfs_get_bdev_and_sb(device->name->str, flags, holder, 1,
+					    &bdev, &bh);
+		if (ret)
+			continue;
 
 		disk_super = (struct btrfs_super_block *)bh->b_data;
 		devid = btrfs_stack_device_id(&disk_super->dev_item);
···
 			fs_devices->rotating = 1;
 
 		fs_devices->open_devices++;
-		if (device->writeable) {
+		if (device->writeable && !device->is_tgtdev_for_dev_replace) {
 			fs_devices->rw_devices++;
 			list_add(&device->dev_alloc_list,
 				 &fs_devices->alloc_list);
···
 
 error_brelse:
 		brelse(bh);
-error_close:
 		blkdev_put(bdev, flags);
-error:
 		continue;
 	}
 	if (fs_devices->open_devices == 0) {
···
 	u64 total_devices;
 
 	flags |= FMODE_EXCL;
-	bdev = blkdev_get_by_path(path, flags, holder);
-
-	if (IS_ERR(bdev)) {
-		ret = PTR_ERR(bdev);
-		goto error;
-	}
-
 	mutex_lock(&uuid_mutex);
-	ret = set_blocksize(bdev, 4096);
+	ret = btrfs_get_bdev_and_sb(path, flags, holder, 0, &bdev, &bh);
 	if (ret)
-		goto error_close;
-	bh = btrfs_read_dev_super(bdev);
-	if (!bh) {
-		ret = -EINVAL;
-		goto error_close;
-	}
+		goto error;
 	disk_super = (struct btrfs_super_block *)bh->b_data;
 	devid = btrfs_stack_device_id(&disk_super->dev_item);
 	transid = btrfs_super_generation(disk_super);
 	total_devices = btrfs_super_num_devices(disk_super);
-	if (disk_super->label[0])
+	if (disk_super->label[0]) {
+		if (disk_super->label[BTRFS_LABEL_SIZE - 1])
+			disk_super->label[BTRFS_LABEL_SIZE - 1] = '\0';
 		printk(KERN_INFO "device label %s ", disk_super->label);
-	else
+	} else {
 		printk(KERN_INFO "device fsid %pU ", disk_super->fsid);
+	}
 	printk(KERN_CONT "devid %llu transid %llu %s\n",
 	       (unsigned long long)devid, (unsigned long long)transid, path);
 	ret = device_list_add(path, disk_super, devid, fs_devices_ret);
 	if (!ret && fs_devices_ret)
 		(*fs_devices_ret)->total_devices = total_devices;
 	brelse(bh);
-error_close:
-	mutex_unlock(&uuid_mutex);
 	blkdev_put(bdev, flags);
 error:
+	mutex_unlock(&uuid_mutex);
 	return ret;
 }
 
···
 
 	*length = 0;
 
-	if (start >= device->total_bytes)
+	if (start >= device->total_bytes || device->is_tgtdev_for_dev_replace)
 		return 0;
 
 	path = btrfs_alloc_path();
···
 	max_hole_size = 0;
 	hole_size = 0;
 
-	if (search_start >= search_end) {
+	if (search_start >= search_end || device->is_tgtdev_for_dev_replace) {
 		ret = -ENOSPC;
 		goto error;
 	}
···
 	struct btrfs_key key;
 
 	WARN_ON(!device->in_fs_metadata);
+	WARN_ON(device->is_tgtdev_for_dev_replace);
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
···
 		root->fs_info->avail_system_alloc_bits |
 		root->fs_info->avail_metadata_alloc_bits;
 
-	if ((all_avail & BTRFS_BLOCK_GROUP_RAID10) &&
-	    root->fs_info->fs_devices->num_devices <= 4) {
+	num_devices = root->fs_info->fs_devices->num_devices;
+	btrfs_dev_replace_lock(&root->fs_info->dev_replace);
+	if (btrfs_dev_replace_is_ongoing(&root->fs_info->dev_replace)) {
+		WARN_ON(num_devices < 1);
+		num_devices--;
+	}
+	btrfs_dev_replace_unlock(&root->fs_info->dev_replace);
+
+	if ((all_avail & BTRFS_BLOCK_GROUP_RAID10) && num_devices <= 4) {
 		printk(KERN_ERR "btrfs: unable to go below four devices "
 		       "on raid10\n");
 		ret = -EINVAL;
 		goto out;
 	}
 
-	if ((all_avail & BTRFS_BLOCK_GROUP_RAID1) &&
-	    root->fs_info->fs_devices->num_devices <= 2) {
+	if ((all_avail & BTRFS_BLOCK_GROUP_RAID1) && num_devices <= 2) {
 		printk(KERN_ERR "btrfs: unable to go below two "
 		       "devices on raid1\n");
 		ret = -EINVAL;
···
 		 * is held.
 		 */
 		list_for_each_entry(tmp, devices, dev_list) {
-			if (tmp->in_fs_metadata && !tmp->bdev) {
+			if (tmp->in_fs_metadata &&
+			    !tmp->is_tgtdev_for_dev_replace &&
+			    !tmp->bdev) {
 				device = tmp;
 				break;
 			}
···
 			goto out;
 		}
 	} else {
-		bdev = blkdev_get_by_path(device_path, FMODE_READ | FMODE_EXCL,
-					  root->fs_info->bdev_holder);
-		if (IS_ERR(bdev)) {
-			ret = PTR_ERR(bdev);
+		ret = btrfs_get_bdev_and_sb(device_path,
+					    FMODE_READ | FMODE_EXCL,
+					    root->fs_info->bdev_holder, 0,
+					    &bdev, &bh);
+		if (ret)
 			goto out;
-		}
-
-		set_blocksize(bdev, 4096);
-		invalidate_bdev(bdev);
-		bh = btrfs_read_dev_super(bdev);
-		if (!bh) {
-			ret = -EINVAL;
-			goto error_close;
-		}
 		disk_super = (struct btrfs_super_block *)bh->b_data;
 		devid = btrfs_stack_device_id(&disk_super->dev_item);
 		dev_uuid = disk_super->dev_item.uuid;
-		device = btrfs_find_device(root, devid, dev_uuid,
+		device = btrfs_find_device(root->fs_info, devid, dev_uuid,
 					   disk_super->fsid);
 		if (!device) {
 			ret = -ENOENT;
 			goto error_brelse;
 		}
+	}
+
+	if (device->is_tgtdev_for_dev_replace) {
+		pr_err("btrfs: unable to remove the dev_replace target dev\n");
+		ret = -EINVAL;
+		goto error_brelse;
 	}
 
 	if (device->writeable && root->fs_info->fs_devices->rw_devices == 1) {
···
 	if (ret)
 		goto error_undo;
 
+	/*
+	 * TODO: the superblock still includes this device in its num_devices
+	 * counter although write_all_supers() is not locked out. This
+	 * could give a filesystem state which requires a degraded mount.
+	 */
 	ret = btrfs_rm_dev_item(root->fs_info->chunk_root, device);
 	if (ret)
 		goto error_undo;
···
 	spin_unlock(&root->fs_info->free_chunk_lock);
 
 	device->in_fs_metadata = 0;
-	btrfs_scrub_cancel_dev(root, device);
+	btrfs_scrub_cancel_dev(root->fs_info, device);
 
 	/*
 	 * the device list mutex makes sure that we don't change
···
 	 * at this point, the device is zero sized.  We want to
 	 * remove it from the devices list and zero out the old super
 	 */
-	if (clear_super) {
+	if (clear_super && disk_super) {
 		/* make sure this device isn't detected as part of
 		 * the FS anymore
 		 */
···
 
 	ret = 0;
 
+	/* Notify udev that device has changed */
+	btrfs_kobject_uevent(bdev, KOBJ_CHANGE);
+
 error_brelse:
 	brelse(bh);
-error_close:
 	if (bdev)
 		blkdev_put(bdev, FMODE_READ | FMODE_EXCL);
 out:
···
 		root->fs_info->fs_devices->rw_devices++;
 	}
 	goto error_brelse;
+}
+
+void btrfs_rm_dev_replace_srcdev(struct btrfs_fs_info *fs_info,
+				 struct btrfs_device *srcdev)
+{
+	WARN_ON(!mutex_is_locked(&fs_info->fs_devices->device_list_mutex));
+	list_del_rcu(&srcdev->dev_list);
+	list_del_rcu(&srcdev->dev_alloc_list);
+	fs_info->fs_devices->num_devices--;
+	if (srcdev->missing) {
+		fs_info->fs_devices->missing_devices--;
+		fs_info->fs_devices->rw_devices++;
+	}
+	if (srcdev->can_discard)
+		fs_info->fs_devices->num_can_discard--;
+	if (srcdev->bdev)
+		fs_info->fs_devices->open_devices--;
+
+	call_rcu(&srcdev->rcu, free_device);
+}
+
+void btrfs_destroy_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
+				      struct btrfs_device *tgtdev)
+{
+	struct btrfs_device *next_device;
+
+	WARN_ON(!tgtdev);
+	mutex_lock(&fs_info->fs_devices->device_list_mutex);
+	if (tgtdev->bdev) {
+		btrfs_scratch_superblock(tgtdev);
+		fs_info->fs_devices->open_devices--;
+	}
+	fs_info->fs_devices->num_devices--;
+	if (tgtdev->can_discard)
+		fs_info->fs_devices->num_can_discard++;
+
+	next_device = list_entry(fs_info->fs_devices->devices.next,
+				 struct btrfs_device, dev_list);
+	if (tgtdev->bdev == fs_info->sb->s_bdev)
+		fs_info->sb->s_bdev = next_device->bdev;
+	if (tgtdev->bdev == fs_info->fs_devices->latest_bdev)
+		fs_info->fs_devices->latest_bdev = next_device->bdev;
+	list_del_rcu(&tgtdev->dev_list);
+
+	call_rcu(&tgtdev->rcu, free_device);
+
+	mutex_unlock(&fs_info->fs_devices->device_list_mutex);
+}
+
+int btrfs_find_device_by_path(struct btrfs_root *root, char *device_path,
+			      struct btrfs_device **device)
+{
+	int ret = 0;
+	struct btrfs_super_block *disk_super;
+	u64 devid;
+	u8 *dev_uuid;
+	struct block_device *bdev;
+	struct buffer_head *bh;
+
+	*device = NULL;
+	ret = btrfs_get_bdev_and_sb(device_path, FMODE_READ,
+				    root->fs_info->bdev_holder, 0, &bdev, &bh);
+	if (ret)
+		return ret;
+	disk_super = (struct btrfs_super_block *)bh->b_data;
+	devid = btrfs_stack_device_id(&disk_super->dev_item);
+	dev_uuid = disk_super->dev_item.uuid;
+	*device = btrfs_find_device(root->fs_info, devid, dev_uuid,
+				    disk_super->fsid);
+	brelse(bh);
+	if (!*device)
+		ret = -ENOENT;
+	blkdev_put(bdev, FMODE_READ);
+	return ret;
+}
+
+int btrfs_find_device_missing_or_by_path(struct btrfs_root *root,
+					 char *device_path,
+					 struct btrfs_device **device)
+{
+	*device = NULL;
+	if (strcmp(device_path, "missing") == 0) {
+		struct list_head *devices;
+		struct btrfs_device *tmp;
+
+		devices = &root->fs_info->fs_devices->devices;
+		/*
+		 * It is safe to read the devices since the volume_mutex
+		 * is held by the caller.
+		 */
+		list_for_each_entry(tmp, devices, dev_list) {
+			if (tmp->in_fs_metadata && !tmp->bdev) {
+				*device = tmp;
+				break;
+			}
+		}
+
+		if (!*device) {
+			pr_err("btrfs: no missing device found\n");
+			return -ENOENT;
+		}
+
+		return 0;
+	} else {
+		return btrfs_find_device_by_path(root, device_path, device);
+	}
 }
 
 /*
···
 		read_extent_buffer(leaf, fs_uuid,
 				   (unsigned long)btrfs_device_fsid(dev_item),
 				   BTRFS_UUID_SIZE);
-		device = btrfs_find_device(root, devid, dev_uuid, fs_uuid);
+		device = btrfs_find_device(root->fs_info, devid, dev_uuid,
+					   fs_uuid);
 		BUG_ON(!device); /* Logic error */
 
 		if (device->fs_devices->seeding) {
···
 	filemap_write_and_wait(bdev->bd_inode->i_mapping);
 
 	devices = &root->fs_info->fs_devices->devices;
-	/*
-	 * we have the volume lock, so we don't need the extra
-	 * device list mutex while reading the list here.
-	 */
+
+	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
 	list_for_each_entry(device, devices, dev_list) {
 		if (device->bdev == bdev) {
 			ret = -EEXIST;
+			mutex_unlock(
+				&root->fs_info->fs_devices->device_list_mutex);
 			goto error;
 		}
 	}
+	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
 
 	device = kzalloc(sizeof(*device), GFP_NOFS);
 	if (!device) {
···
 	device->dev_root = root->fs_info->dev_root;
 	device->bdev = bdev;
 	device->in_fs_metadata = 1;
+	device->is_tgtdev_for_dev_replace = 0;
 	device->mode = FMODE_EXCL;
 	set_blocksize(device->bdev, 4096);
 
···
 	return ret;
 }
 
+int btrfs_init_dev_replace_tgtdev(struct btrfs_root *root, char *device_path,
+				  struct btrfs_device **device_out)
+{
+	struct request_queue *q;
+	struct btrfs_device *device;
+	struct block_device *bdev;
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	struct list_head *devices;
+	struct rcu_string *name;
+	int ret = 0;
+
+	*device_out = NULL;
+	if (fs_info->fs_devices->seeding)
+		return -EINVAL;
+
+	bdev = blkdev_get_by_path(device_path, FMODE_WRITE | FMODE_EXCL,
+				  fs_info->bdev_holder);
+	if (IS_ERR(bdev))
+		return PTR_ERR(bdev);
+
+	filemap_write_and_wait(bdev->bd_inode->i_mapping);
+
+	devices = &fs_info->fs_devices->devices;
+	list_for_each_entry(device, devices, dev_list) {
+		if (device->bdev == bdev) {
+			ret = -EEXIST;
+			goto error;
+		}
+	}
+
+	device = kzalloc(sizeof(*device), GFP_NOFS);
+	if (!device) {
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	name = rcu_string_strdup(device_path, GFP_NOFS);
+	if (!name) {
+		kfree(device);
+		ret = -ENOMEM;
+		goto error;
+	}
+	rcu_assign_pointer(device->name, name);
+
+	q = bdev_get_queue(bdev);
+	if (blk_queue_discard(q))
+		device->can_discard = 1;
+	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
+	device->writeable = 1;
+	device->work.func = pending_bios_fn;
+	generate_random_uuid(device->uuid);
+	device->devid = BTRFS_DEV_REPLACE_DEVID;
+	spin_lock_init(&device->io_lock);
+	device->generation = 0;
+	device->io_width = root->sectorsize;
+	device->io_align = root->sectorsize;
+	device->sector_size = root->sectorsize;
+	device->total_bytes = i_size_read(bdev->bd_inode);
+	device->disk_total_bytes = device->total_bytes;
+	device->dev_root = fs_info->dev_root;
+	device->bdev = bdev;
+	device->in_fs_metadata = 1;
+	device->is_tgtdev_for_dev_replace = 1;
+	device->mode = FMODE_EXCL;
+	set_blocksize(device->bdev, 4096);
+	device->fs_devices = fs_info->fs_devices;
+	list_add(&device->dev_list, &fs_info->fs_devices->devices);
+	fs_info->fs_devices->num_devices++;
+	fs_info->fs_devices->open_devices++;
+	if (device->can_discard)
+		fs_info->fs_devices->num_can_discard++;
+	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
+
+	*device_out = device;
+	return ret;
+
+error:
+	blkdev_put(bdev, FMODE_EXCL);
+	return ret;
+}
+
+void btrfs_init_dev_replace_tgtdev_for_resume(struct btrfs_fs_info *fs_info,
+					      struct btrfs_device *tgtdev)
+{
+	WARN_ON(fs_info->fs_devices->rw_devices == 0);
+	tgtdev->io_width = fs_info->dev_root->sectorsize;
+	tgtdev->io_align = fs_info->dev_root->sectorsize;
+	tgtdev->sector_size = fs_info->dev_root->sectorsize;
+	tgtdev->dev_root = fs_info->dev_root;
+	tgtdev->in_fs_metadata = 1;
+}
+
 static noinline int btrfs_update_device(struct btrfs_trans_handle *trans,
 					struct btrfs_device *device)
 {
···
 
 	if (!device->writeable)
 		return -EACCES;
-	if (new_size <= device->total_bytes)
+	if (new_size <= device->total_bytes ||
+	    device->is_tgtdev_for_dev_replace)
 		return -EINVAL;
 
 	btrfs_set_super_total_bytes(super_copy, old_total + diff);
···
 	return 1;
 }
 
-static u64 div_factor_fine(u64 num, int factor)
-{
-	if (factor <= 0)
-		return 0;
-	if (factor >= 100)
-		return num;
-
-	num *= factor;
-	do_div(num, 100);
-	return num;
-}
-
 static int chunk_usage_filter(struct btrfs_fs_info *fs_info, u64 chunk_offset,
 			      struct btrfs_balance_args *bargs)
 {
···
 	return 1;
 }
 
-static u64 div_factor(u64 num, int factor)
-{
-	if (factor == 10)
-		return num;
-	num *= factor;
-	do_div(num, 10);
-	return num;
-}
-
 static int __btrfs_balance(struct btrfs_fs_info *fs_info)
 {
 	struct btrfs_balance_control *bctl = fs_info->balance_ctl;
···
 		size_to_free = div_factor(old_size, 1);
 		size_to_free = min(size_to_free, (u64)1 * 1024 * 1024);
 		if (!device->writeable ||
-		    device->total_bytes - device->bytes_used > size_to_free)
+		    device->total_bytes - device->bytes_used > size_to_free ||
+		    device->is_tgtdev_for_dev_replace)
 			continue;
 
 		ret = btrfs_shrink_device(device, old_size - size_to_free);
···
 	u64 allowed;
 	int mixed = 0;
 	int ret;
+	u64 num_devices;
 
 	if (btrfs_fs_closing(fs_info) ||
 	    atomic_read(&fs_info->balance_pause_req) ||
···
 		}
 	}
 
+	num_devices = fs_info->fs_devices->num_devices;
+	btrfs_dev_replace_lock(&fs_info->dev_replace);
+	if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace)) {
+		BUG_ON(num_devices < 1);
+		num_devices--;
+	}
+	btrfs_dev_replace_unlock(&fs_info->dev_replace);
 	allowed = BTRFS_AVAIL_ALLOC_BIT_SINGLE;
-	if (fs_info->fs_devices->num_devices == 1)
+	if (num_devices == 1)
 		allowed |= BTRFS_BLOCK_GROUP_DUP;
-	else if (fs_info->fs_devices->num_devices < 4)
+	else if (num_devices < 4)
 		allowed |= (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1);
 	else
 		allowed |= (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1 |
···
 		ret = btrfs_balance(fs_info->balance_ctl, NULL);
 	}
 
+	atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
 	mutex_unlock(&fs_info->balance_mutex);
 	mutex_unlock(&fs_info->volume_mutex);
 
···
 		return 0;
 	}
 
+	WARN_ON(atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1));
 	tsk = kthread_run(balance_kthread, fs_info, "btrfs-balance");
 	if (IS_ERR(tsk))
 		return PTR_ERR(tsk);
···
 	u64 old_size = device->total_bytes;
 	u64 diff = device->total_bytes - new_size;
 
-	if (new_size >= device->total_bytes)
+	if (device->is_tgtdev_for_dev_replace)
 		return -EINVAL;
 
 	path = btrfs_alloc_path();
···
 	return 0;
 }
 
+struct btrfs_raid_attr btrfs_raid_array[BTRFS_NR_RAID_TYPES] = {
+	{ 2, 1, 0, 4, 2, 2 /* raid10 */ },
+	{ 1, 1, 2, 2, 2, 2 /* raid1 */ },
+	{ 1, 2, 1, 1, 1, 2 /* dup */ },
+	{ 1, 1, 0, 2, 1, 1 /* raid0 */ },
+	{ 1, 1, 0, 1, 1, 1 /* single */ },
+};
+
 static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 			       struct btrfs_root *extent_root,
 			       struct map_lookup **map_ret,
···
 	int ndevs;
 	int i;
 	int j;
+	int index;
 
 	BUG_ON(!alloc_profile_is_valid(type, 0));
 
 	if (list_empty(&fs_devices->alloc_list))
 		return -ENOSPC;
 
-	sub_stripes = 1;
-	dev_stripes = 1;
-	devs_increment = 1;
-	ncopies = 1;
-	devs_max = 0;	/* 0 == as many as possible */
-	devs_min = 1;
+	index = __get_raid_index(type);
 
-	/*
-	 * define the properties of each RAID type.
-	 * FIXME: move this to a global table and use it in all RAID
-	 * calculation code
-	 */
-	if (type & (BTRFS_BLOCK_GROUP_DUP)) {
-		dev_stripes = 2;
-		ncopies = 2;
-		devs_max = 1;
-	} else if (type & (BTRFS_BLOCK_GROUP_RAID0)) {
-		devs_min = 2;
-	} else if (type & (BTRFS_BLOCK_GROUP_RAID1)) {
-		devs_increment = 2;
-		ncopies = 2;
-		devs_max = 2;
-		devs_min = 2;
-	} else if (type & (BTRFS_BLOCK_GROUP_RAID10)) {
-		sub_stripes = 2;
-		devs_increment = 2;
-		ncopies = 2;
-		devs_min = 4;
-	} else {
-		devs_max = 1;
-	}
+	sub_stripes = btrfs_raid_array[index].sub_stripes;
+	dev_stripes = btrfs_raid_array[index].dev_stripes;
+	devs_max = btrfs_raid_array[index].devs_max;
+	devs_min = btrfs_raid_array[index].devs_min;
+	devs_increment = btrfs_raid_array[index].devs_increment;
+	ncopies = btrfs_raid_array[index].ncopies;
 
 	if (type & BTRFS_BLOCK_GROUP_DATA) {
 		max_stripe_size = 1024 * 1024 * 1024;
···
 		cur = cur->next;
 
 		if (!device->writeable) {
-			printk(KERN_ERR
+			WARN(1, KERN_ERR
 			       "btrfs: read-only device in alloc_list\n");
-			WARN_ON(1);
 			continue;
 		}
 
-		if (!device->in_fs_metadata)
+		if (!device->in_fs_metadata ||
+		    device->is_tgtdev_for_dev_replace)
 			continue;
 
 		if (device->total_bytes > device->bytes_used)
···
 		devices_info[ndevs].total_avail = total_avail;
 		devices_info[ndevs].dev = device;
 		++ndevs;
+		WARN_ON(ndevs > fs_devices->rw_devices);
 	}
 
 	/*
···
 	}
 }
 
-int btrfs_num_copies(struct btrfs_mapping_tree *map_tree, u64 logical, u64 len)
+int btrfs_num_copies(struct btrfs_fs_info *fs_info, u64 logical, u64 len)
 {
+	struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
 	struct extent_map *em;
 	struct map_lookup *map;
 	struct extent_map_tree *em_tree = &map_tree->map_tree;
···
 	else
 		ret = 1;
 	free_extent_map(em);
+
+	btrfs_dev_replace_lock(&fs_info->dev_replace);
+	if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace))
+		ret++;
+	btrfs_dev_replace_unlock(&fs_info->dev_replace);
+
 	return ret;
 }
 
-static int find_live_mirror(struct map_lookup *map, int first, int num,
-			    int optimal)
+static int find_live_mirror(struct btrfs_fs_info *fs_info,
+			    struct map_lookup *map, int first, int num,
+			    int optimal, int dev_replace_is_ongoing)
 {
 	int i;
-	if (map->stripes[optimal].dev->bdev)
-		return optimal;
-	for (i = first; i < first + num; i++) {
-		if (map->stripes[i].dev->bdev)
-			return i;
+	int tolerance;
+	struct btrfs_device *srcdev;
+
+	if (dev_replace_is_ongoing &&
+	    fs_info->dev_replace.cont_reading_from_srcdev_mode ==
+	     BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_AVOID)
+		srcdev = fs_info->dev_replace.srcdev;
+	else
+		srcdev = NULL;
+
+	/*
+	 * try to avoid the drive that is the source drive for a
+	 * dev-replace procedure, only choose it if no other non-missing
+	 * mirror is available
+	 */
+	for (tolerance = 0; tolerance < 2; tolerance++) {
+		if (map->stripes[optimal].dev->bdev &&
+		    (tolerance || map->stripes[optimal].dev != srcdev))
+			return optimal;
+		for (i = first; i < first + num; i++) {
+			if (map->stripes[i].dev->bdev &&
+			    (tolerance || map->stripes[i].dev != srcdev))
+				return i;
+		}
 	}
+
 	/* we couldn't find one that doesn't fail.  Just return something
 	 * and the io error handling code will clean up eventually
 	 */
 	return optimal;
 }
 
-static int __btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,
+static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
 			     u64 logical, u64 *length,
 			     struct btrfs_bio **bbio_ret,
 			     int mirror_num)
 {
 	struct extent_map *em;
 	struct map_lookup *map;
+	struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
 	struct extent_map_tree *em_tree = &map_tree->map_tree;
 	u64 offset;
 	u64 stripe_offset;
···
 	int num_stripes;
 	int max_errors = 0;
 	struct btrfs_bio *bbio = NULL;
+	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
+	int dev_replace_is_ongoing = 0;
+	int num_alloc_stripes;
+	int patch_the_first_stripe_for_dev_replace = 0;
+	u64 physical_to_patch_in_first_stripe = 0;
 
 	read_lock(&em_tree->lock);
 	em = lookup_extent_mapping(em_tree, logical, *length);
···
 	BUG_ON(em->start > logical || em->start + em->len < logical);
 	map = (struct map_lookup *)em->bdev;
 	offset = logical - em->start;
-
-	if (mirror_num > map->num_stripes)
-		mirror_num = 0;
 
 	stripe_nr = offset;
 	/*
···
 	if (!bbio_ret)
 		goto out;
 
+	btrfs_dev_replace_lock(dev_replace);
+	dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(dev_replace);
+	if (!dev_replace_is_ongoing)
+		btrfs_dev_replace_unlock(dev_replace);
+
+	if (dev_replace_is_ongoing && mirror_num == map->num_stripes + 1 &&
+	    !(rw & (REQ_WRITE | REQ_DISCARD | REQ_GET_READ_MIRRORS)) &&
+	    dev_replace->tgtdev != NULL) {
+		/*
+		 * in dev-replace case, for repair case (that's the only
+		 * case where the mirror is selected explicitly when
+		 * calling btrfs_map_block), blocks left of the left cursor
+		 * can also be read from the target drive.
+		 * For REQ_GET_READ_MIRRORS, the target drive is added as
+		 * the last one to the array of stripes. For READ, it also
+		 * needs to be supported using the same mirror number.
+		 * If the requested block is not left of the left cursor,
+		 * EIO is returned. This can happen because btrfs_num_copies()
+		 * returns one more in the dev-replace case.
+		 */
+		u64 tmp_length = *length;
+		struct btrfs_bio *tmp_bbio = NULL;
+		int tmp_num_stripes;
+		u64 srcdev_devid = dev_replace->srcdev->devid;
+		int index_srcdev = 0;
+		int found = 0;
+		u64 physical_of_found = 0;
+
+		ret = __btrfs_map_block(fs_info, REQ_GET_READ_MIRRORS,
+			     logical, &tmp_length, &tmp_bbio, 0);
+		if (ret) {
+			WARN_ON(tmp_bbio != NULL);
+			goto out;
+		}
+
+		tmp_num_stripes = tmp_bbio->num_stripes;
+		if (mirror_num > tmp_num_stripes) {
+			/*
+			 * REQ_GET_READ_MIRRORS does not contain this
+			 * mirror, that means that the requested area
+			 * is not left of the left cursor
+			 */
+			ret = -EIO;
+			kfree(tmp_bbio);
+			goto out;
+		}
+
+		/*
+		 * process the rest of the function using the mirror_num
+		 * of the source drive. Therefore look it up first.
+		 * At the end, patch the device pointer to the one of the
+		 * target drive.
+		 */
+		for (i = 0; i < tmp_num_stripes; i++) {
+			if (tmp_bbio->stripes[i].dev->devid == srcdev_devid) {
+				/*
+				 * In case of DUP, in order to keep it
+				 * simple, only add the mirror with the
+				 * lowest physical address
+				 */
+				if (found &&
+				    physical_of_found <=
+				     tmp_bbio->stripes[i].physical)
+					continue;
+				index_srcdev = i;
+				found = 1;
+				physical_of_found =
+					tmp_bbio->stripes[i].physical;
+			}
+		}
+
+		if (found) {
+			mirror_num = index_srcdev + 1;
+			patch_the_first_stripe_for_dev_replace = 1;
+			physical_to_patch_in_first_stripe = physical_of_found;
+		} else {
+			WARN_ON(1);
+			ret = -EIO;
+			kfree(tmp_bbio);
+			goto out;
+		}
+
+		kfree(tmp_bbio);
+	} else if (mirror_num > map->num_stripes) {
+		mirror_num = 0;
+	}
+
 	num_stripes = 1;
 	stripe_index = 0;
 	stripe_nr_orig = stripe_nr;
···
 					    stripe_nr_end - stripe_nr_orig);
 		stripe_index = do_div(stripe_nr, map->num_stripes);
 	} else if (map->type & BTRFS_BLOCK_GROUP_RAID1) {
-		if (rw & (REQ_WRITE | REQ_DISCARD))
+		if (rw & (REQ_WRITE | REQ_DISCARD | REQ_GET_READ_MIRRORS))
 			num_stripes = map->num_stripes;
 		else if (mirror_num)
 			stripe_index = mirror_num - 1;
 		else {
-			stripe_index = find_live_mirror(map, 0,
+			stripe_index = find_live_mirror(fs_info, map, 0,
 					    map->num_stripes,
-					    current->pid % map->num_stripes);
+					    current->pid % map->num_stripes,
+					    dev_replace_is_ongoing);
 			mirror_num = stripe_index + 1;
 		}
 
 	} else if (map->type & BTRFS_BLOCK_GROUP_DUP) {
-		if (rw & (REQ_WRITE | REQ_DISCARD)) {
+		if (rw & (REQ_WRITE | REQ_DISCARD | REQ_GET_READ_MIRRORS)) {
 			num_stripes = map->num_stripes;
 		} else if (mirror_num) {
 			stripe_index = mirror_num - 1;
···
 		stripe_index = do_div(stripe_nr, factor);
 		stripe_index *= map->sub_stripes;
 
-		if (rw & REQ_WRITE)
+		if (rw & (REQ_WRITE | REQ_GET_READ_MIRRORS))
 			num_stripes = map->sub_stripes;
 		else if (rw & REQ_DISCARD)
 			num_stripes = min_t(u64, map->sub_stripes *
···
 			stripe_index += mirror_num - 1;
 		else {
 			int old_stripe_index = stripe_index;
-			stripe_index = find_live_mirror(map, stripe_index,
+			stripe_index = find_live_mirror(fs_info, map,
+					      stripe_index,
 					      map->sub_stripes, stripe_index +
-					      current->pid % map->sub_stripes);
+					      current->pid % map->sub_stripes,
+					      dev_replace_is_ongoing);
 			mirror_num = stripe_index - old_stripe_index + 1;
 		}
 	} else {
···
 	}
 	BUG_ON(stripe_index >= map->num_stripes);
 
-	bbio = kzalloc(btrfs_bio_size(num_stripes), GFP_NOFS);
+	num_alloc_stripes = num_stripes;
+	if (dev_replace_is_ongoing) {
+		if (rw & (REQ_WRITE | REQ_DISCARD))
+			num_alloc_stripes <<= 1;
+		if (rw & REQ_GET_READ_MIRRORS)
+			num_alloc_stripes++;
+	}
+	bbio = kzalloc(btrfs_bio_size(num_alloc_stripes), GFP_NOFS);
 	if (!bbio) {
 		ret = -ENOMEM;
 		goto out;
···
 		}
 	}
 
-	if (rw & REQ_WRITE) {
+	if (rw & (REQ_WRITE | REQ_GET_READ_MIRRORS)) {
 		if (map->type & (BTRFS_BLOCK_GROUP_RAID1 |
 				 BTRFS_BLOCK_GROUP_RAID10 |
 				 BTRFS_BLOCK_GROUP_DUP)) {
···
 		}
 	}
 
+	if (dev_replace_is_ongoing && (rw & (REQ_WRITE | REQ_DISCARD)) &&
+	    dev_replace->tgtdev != NULL) {
+		int index_where_to_add;
+		u64 srcdev_devid = dev_replace->srcdev->devid;
+
+		/*
+		 * duplicate the write operations while the dev replace
+		 * procedure is running. Since the copying of the old disk
+		 * to the new disk takes place at run time while the
+		 * filesystem is mounted writable, the regular write
+		 * operations to the old disk have to be duplicated to go
+		 * to the new disk as well.
+		 * Note that device->missing is handled by the caller, and
+		 * that the write to the old disk is already set up in the
+		 * stripes array.
+		 */
+		index_where_to_add = num_stripes;
+		for (i = 0; i < num_stripes; i++) {
+			if (bbio->stripes[i].dev->devid == srcdev_devid) {
+				/* write to new disk, too */
+				struct btrfs_bio_stripe *new =
+					bbio->stripes + index_where_to_add;
+				struct btrfs_bio_stripe *old =
+					bbio->stripes + i;
+
+				new->physical = old->physical;
+				new->length = old->length;
+				new->dev = dev_replace->tgtdev;
+				index_where_to_add++;
+				max_errors++;
+			}
+		}
+		num_stripes = index_where_to_add;
+	} else if (dev_replace_is_ongoing && (rw & REQ_GET_READ_MIRRORS) &&
+		   dev_replace->tgtdev != NULL) {
+		u64 srcdev_devid = dev_replace->srcdev->devid;
+		int index_srcdev = 0;
+		int found = 0;
+		u64 physical_of_found = 0;
+
+		/*
+		 * During the dev-replace procedure, the target drive can
+		 * also be used to read data in case it is needed to repair
+		 * a corrupt block elsewhere. This is possible if the
+		 * requested area is left of the left cursor. In this area,
+		 * the target drive is a full copy of the source drive.
+		 */
+		for (i = 0; i < num_stripes; i++) {
+			if (bbio->stripes[i].dev->devid == srcdev_devid) {
+				/*
+				 * In case of DUP, in order to keep it
+				 * simple, only add the mirror with the
+				 * lowest physical address
+				 */
+				if (found &&
+				    physical_of_found <=
+				     bbio->stripes[i].physical)
+					continue;
+				index_srcdev = i;
+				found = 1;
+				physical_of_found = bbio->stripes[i].physical;
+			}
+		}
+		if (found) {
+			u64 length = map->stripe_len;
+
+			if (physical_of_found + length <=
+			    dev_replace->cursor_left) {
+				struct btrfs_bio_stripe *tgtdev_stripe =
+					bbio->stripes + num_stripes;
+
+				tgtdev_stripe->physical = physical_of_found;
+				tgtdev_stripe->length =
+					bbio->stripes[index_srcdev].length;
+				tgtdev_stripe->dev = dev_replace->tgtdev;
+
+				num_stripes++;
+			}
+		}
+	}
+
 	*bbio_ret = bbio;
 	bbio->num_stripes = num_stripes;
 	bbio->max_errors = max_errors;
 	bbio->mirror_num = mirror_num;
+
+	/*
+	 * this is the case that REQ_READ && dev_replace_is_ongoing &&
+	 * mirror_num == num_stripes + 1 && dev_replace target drive is
+	 * available as a mirror
+	 */
+	if (patch_the_first_stripe_for_dev_replace && num_stripes > 0) {
+		WARN_ON(num_stripes > 1);
+		bbio->stripes[0].dev = dev_replace->tgtdev;
+		bbio->stripes[0].physical = physical_to_patch_in_first_stripe;
+		bbio->mirror_num = map->num_stripes + 1;
+	}
 out:
+	if (dev_replace_is_ongoing)
+		btrfs_dev_replace_unlock(dev_replace);
 	free_extent_map(em);
 	return ret;
 }
 
-int btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,
+int btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
 		      u64 logical, u64 *length,
 		      struct btrfs_bio **bbio_ret, int mirror_num)
 {
-	return __btrfs_map_block(map_tree, rw, logical, length, bbio_ret,
+	return __btrfs_map_block(fs_info, rw, logical, length, bbio_ret,
 				 mirror_num);
 }
 
···
 				   &device->work);
 }
 
+static int bio_size_ok(struct block_device *bdev, struct bio *bio,
+		       sector_t sector)
+{
+	struct bio_vec *prev;
+	struct request_queue *q = bdev_get_queue(bdev);
+	unsigned short max_sectors = queue_max_sectors(q);
+	struct bvec_merge_data bvm = {
+		.bi_bdev = bdev,
+		.bi_sector = sector,
+		.bi_rw = bio->bi_rw,
+	};
+
+	if (bio->bi_vcnt == 0) {
+		WARN_ON(1);
+		return 1;
+	}
+
+	prev = &bio->bi_io_vec[bio->bi_vcnt - 1];
+	if ((bio->bi_size >> 9) > max_sectors)
+		return 0;
+
+	if (!q->merge_bvec_fn)
+		return 1;
+
+	bvm.bi_size = bio->bi_size - prev->bv_len;
+	if (q->merge_bvec_fn(q, &bvm, prev) < prev->bv_len)
+		return 0;
+	return 1;
+}
+
+static void submit_stripe_bio(struct btrfs_root *root, struct btrfs_bio *bbio,
+			      struct bio *bio, u64 physical, int dev_nr,
+			      int rw, int async)
+{
+	struct btrfs_device *dev = bbio->stripes[dev_nr].dev;
+
+	bio->bi_private = bbio;
+	bio->bi_private = merge_stripe_index_into_bio_private(
+			bio->bi_private, (unsigned int)dev_nr);
+	bio->bi_end_io = btrfs_end_bio;
+	bio->bi_sector = physical >> 9;
+#ifdef DEBUG
+	{
+		struct rcu_string *name;
+
+		rcu_read_lock();
+		name = rcu_dereference(dev->name);
+		pr_debug("btrfs_map_bio: rw %d, sector=%llu, dev=%lu "
+			 "(%s id %llu), size=%u\n", rw,
+			 (u64)bio->bi_sector, (u_long)dev->bdev->bd_dev,
+			 name->str, dev->devid, bio->bi_size);
+		rcu_read_unlock();
+	}
+#endif
+	bio->bi_bdev = dev->bdev;
+	if (async)
+		schedule_bio(root, dev, rw, bio);
+	else
+		btrfsic_submit_bio(rw, bio);
+}
+
+static int breakup_stripe_bio(struct btrfs_root *root, struct btrfs_bio *bbio,
+			      struct bio *first_bio, struct btrfs_device *dev,
+			      int dev_nr, int rw, int async)
+{
+	struct bio_vec *bvec = first_bio->bi_io_vec;
+	struct bio *bio;
+	int nr_vecs = bio_get_nr_vecs(dev->bdev);
+	u64 physical = bbio->stripes[dev_nr].physical;
+
+again:
+	bio = btrfs_bio_alloc(dev->bdev, physical >> 9, nr_vecs, GFP_NOFS);
+	if (!bio)
+		return -ENOMEM;
+
+	while (bvec <= (first_bio->bi_io_vec + first_bio->bi_vcnt - 1)) {
+		if (bio_add_page(bio, bvec->bv_page, bvec->bv_len,
+				 bvec->bv_offset) < bvec->bv_len) {
+			u64 len = bio->bi_size;
+
+			atomic_inc(&bbio->stripes_pending);
+			submit_stripe_bio(root, bbio, bio, physical, dev_nr,
+					  rw, async);
+			physical += len;
+			goto again;
+		}
+		bvec++;
+	}
+
+	submit_stripe_bio(root, bbio, bio, physical, dev_nr, rw, async);
+	return 0;
+}
+
+static void bbio_error(struct btrfs_bio *bbio, struct bio *bio, u64 logical)
+{
+	atomic_inc(&bbio->error);
+	if (atomic_dec_and_test(&bbio->stripes_pending)) {
+		bio->bi_private = bbio->private;
+		bio->bi_end_io = bbio->end_io;
+		bio->bi_bdev = (struct block_device *)
+			(unsigned long)bbio->mirror_num;
+		bio->bi_sector = logical >> 9;
+		kfree(bbio);
+		bio_endio(bio, -EIO);
+	}
+}
+
 int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio,
 		  int mirror_num, int async_submit)
 {
-	struct btrfs_mapping_tree *map_tree;
 	struct btrfs_device *dev;
 	struct bio *first_bio = bio;
 	u64 logical = (u64)bio->bi_sector << 9;
···
 	struct btrfs_bio *bbio = NULL;
 
 	length = bio->bi_size;
-	map_tree = &root->fs_info->mapping_tree;
 	map_length = length;
 
-	ret = btrfs_map_block(map_tree, rw, logical, &map_length, &bbio,
+	ret = btrfs_map_block(root->fs_info, rw, logical, &map_length, &bbio,
 			      mirror_num);
-	if (ret) /* -ENOMEM */
+	if (ret)
 		return ret;
 
 	total_devs = bbio->num_stripes;
···
 	atomic_set(&bbio->stripes_pending, bbio->num_stripes);
 
 	while (dev_nr < total_devs) {
+		dev = bbio->stripes[dev_nr].dev;
+		if (!dev || !dev->bdev || (rw & WRITE && !dev->writeable)) {
+			bbio_error(bbio, first_bio, logical);
+			dev_nr++;
+			continue;
+		}
+
+		/*
+		 * Check and see if we're ok with this bio based on it's size
+		 * and offset with the given device.
+		 */
+		if (!bio_size_ok(dev->bdev, first_bio,
+				 bbio->stripes[dev_nr].physical >> 9)) {
+			ret = breakup_stripe_bio(root, bbio, first_bio, dev,
+						 dev_nr, rw, async_submit);
+			BUG_ON(ret);
+			dev_nr++;
+			continue;
+		}
+
 		if (dev_nr < total_devs - 1) {
 			bio = bio_clone(first_bio, GFP_NOFS);
 			BUG_ON(!bio); /* -ENOMEM */
 		} else {
 			bio = first_bio;
 		}
-		bio->bi_private = bbio;
-		bio->bi_private = merge_stripe_index_into_bio_private(
-				bio->bi_private, (unsigned int)dev_nr);
-		bio->bi_end_io = btrfs_end_bio;
-		bio->bi_sector = bbio->stripes[dev_nr].physical >> 9;
-		dev = bbio->stripes[dev_nr].dev;
-		if (dev && dev->bdev && (rw != WRITE || dev->writeable)) {
-#ifdef DEBUG
-			struct rcu_string *name;
 
-			rcu_read_lock();
-			name = rcu_dereference(dev->name);
-			pr_debug("btrfs_map_bio: rw %d, sector=%llu, dev=%lu "
-				 "(%s id %llu), size=%u\n", rw,
-				 (u64)bio->bi_sector, (u_long)dev->bdev->bd_dev,
-				 name->str, dev->devid, bio->bi_size);
-			rcu_read_unlock();
-#endif
-			bio->bi_bdev = dev->bdev;
-			if (async_submit)
-				schedule_bio(root, dev, rw, bio);
-			else
-				btrfsic_submit_bio(rw, bio);
-		} else {
-			bio->bi_bdev = root->fs_info->fs_devices->latest_bdev;
-			bio->bi_sector = logical >> 9;
-			bio_endio(bio, -EIO);
-		}
+		submit_stripe_bio(root, bbio, bio,
+				  bbio->stripes[dev_nr].physical, dev_nr, rw,
+				  async_submit);
 		dev_nr++;
 	}
 	return 0;
 }
 
-struct btrfs_device *btrfs_find_device(struct btrfs_root *root, u64 devid,
+struct btrfs_device *btrfs_find_device(struct btrfs_fs_info *fs_info, u64 devid,
 				       u8 *uuid, u8 *fsid)
 {
 	struct btrfs_device *device;
 	struct btrfs_fs_devices *cur_devices;
 
-	cur_devices = root->fs_info->fs_devices;
+	cur_devices = fs_info->fs_devices;
 	while (cur_devices) {
 		if (!fsid ||
 		    !memcmp(cur_devices->fsid, fsid, BTRFS_UUID_SIZE)) {
···
 	em->bdev = (struct block_device *)map;
 	em->start = logical;
 	em->len = length;
+	em->orig_start = 0;
 	em->block_start = 0;
 	em->block_len = em->len;
 
···
 		read_extent_buffer(leaf, uuid, (unsigned long)
 				   btrfs_stripe_dev_uuid_nr(chunk, i),
 				   BTRFS_UUID_SIZE);
-		map->stripes[i].dev = btrfs_find_device(root, devid, uuid,
-							NULL);
+		map->stripes[i].dev = btrfs_find_device(root->fs_info, devid,
+							uuid, NULL);
 		if (!map->stripes[i].dev && !btrfs_test_opt(root, DEGRADED)) {
 			kfree(map);
 			free_extent_map(em);
···
 	device->io_align = btrfs_device_io_align(leaf, dev_item);
 	device->io_width = btrfs_device_io_width(leaf, dev_item);
 	device->sector_size = btrfs_device_sector_size(leaf, dev_item);
+	WARN_ON(device->devid == BTRFS_DEV_REPLACE_DEVID);
+	device->is_tgtdev_for_dev_replace = 0;
 
 	ptr = (unsigned long)btrfs_device_uuid(dev_item);
 	read_extent_buffer(leaf, device->uuid, ptr, BTRFS_UUID_SIZE);
···
 			return ret;
 	}
 
-	device = btrfs_find_device(root, devid, dev_uuid, fs_uuid);
+	device = btrfs_find_device(root->fs_info, devid, dev_uuid, fs_uuid);
 	if (!device || !device->bdev) {
 		if (!btrfs_test_opt(root, DEGRADED))
 			return -EIO;
···
 	fill_device_from_item(leaf, dev_item, device);
 	device->dev_root = root->fs_info->dev_root;
 	device->in_fs_metadata = 1;
-	if (device->writeable) {
+	if (device->writeable && !device->is_tgtdev_for_dev_replace) {
 		device->fs_devices->total_rw_bytes += device->total_bytes;
 		spin_lock(&root->fs_info->free_chunk_lock);
 		root->fs_info->free_chunk_space += device->total_bytes -
···
 	int i;
 
 	mutex_lock(&fs_devices->device_list_mutex);
-	dev = btrfs_find_device(root, stats->devid, NULL, NULL);
+	dev = btrfs_find_device(root->fs_info, stats->devid, NULL, NULL);
 	mutex_unlock(&fs_devices->device_list_mutex);
 
 	if (!dev) {
···
 	}
 	if (stats->nr_items > BTRFS_DEV_STAT_VALUES_MAX)
 		stats->nr_items = BTRFS_DEV_STAT_VALUES_MAX;
+	return 0;
+}
+
+int btrfs_scratch_superblock(struct btrfs_device *device)
+{
+	struct buffer_head *bh;
+	struct btrfs_super_block *disk_super;
+
+	bh = btrfs_read_dev_super(device->bdev);
+	if (!bh)
+		return -EINVAL;
+	disk_super = (struct btrfs_super_block *)bh->b_data;
+
+	memset(&disk_super->magic, 0, sizeof(disk_super->magic));
+	set_buffer_dirty(bh);
+	sync_dirty_buffer(bh);
+	brelse(bh);
+
 	return 0;
 }

fs/btrfs/volumes.h

···
 	int in_fs_metadata;
 	int missing;
 	int can_discard;
+	int is_tgtdev_for_dev_replace;
 
 	spinlock_t io_lock;
 
···
 	u8 uuid[BTRFS_UUID_SIZE];
 
 	/* per-device scrub information */
-	struct scrub_dev *scrub_device;
+	struct scrub_ctx *scrub_device;
 
 	struct btrfs_work work;
 	struct rcu_head rcu;
···
 	u64 total_avail;
 };
 
+struct btrfs_raid_attr {
+	int sub_stripes;	/* sub_stripes info for map */
+	int dev_stripes;	/* stripes per dev */
+	int devs_max;		/* max devs to use */
+	int devs_min;		/* min devs needed */
+	int devs_increment;	/* ndevs has to be a multiple of this */
+	int ncopies;		/* how many copies to data has */
+};
+
 struct map_lookup {
 	u64 type;
 	int io_align;
···
 			   struct btrfs_device *device,
 			   u64 chunk_tree, u64 chunk_objectid,
 			   u64 chunk_offset, u64 start, u64 num_bytes);
-int btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,
+int btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
 		    u64 logical, u64 *length,
 		    struct btrfs_bio **bbio_ret, int mirror_num);
 int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree,
···
 int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
 			  struct btrfs_fs_devices **fs_devices_ret);
 int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
-void btrfs_close_extra_devices(struct btrfs_fs_devices *fs_devices);
+void btrfs_close_extra_devices(struct btrfs_fs_info *fs_info,
+			       struct btrfs_fs_devices *fs_devices, int step);
+int btrfs_find_device_missing_or_by_path(struct btrfs_root *root,
+					 char *device_path,
+					 struct btrfs_device **device);
+int btrfs_find_device_by_path(struct btrfs_root *root, char *device_path,
+			      struct btrfs_device **device);
 int btrfs_add_device(struct btrfs_trans_handle *trans,
 		     struct btrfs_root *root,
 		     struct btrfs_device *device);
 int btrfs_rm_device(struct btrfs_root *root, char *device_path);
 void btrfs_cleanup_fs_uuids(void);
-int btrfs_num_copies(struct btrfs_mapping_tree *map_tree, u64 logical, u64 len);
+int btrfs_num_copies(struct btrfs_fs_info *fs_info, u64 logical, u64 len);
 int btrfs_grow_device(struct btrfs_trans_handle *trans,
 		      struct btrfs_device *device, u64 new_size);
-struct btrfs_device *btrfs_find_device(struct btrfs_root *root, u64 devid,
+struct btrfs_device *btrfs_find_device(struct btrfs_fs_info *fs_info, u64 devid,
 				       u8 *uuid, u8 *fsid);
 int btrfs_shrink_device(struct btrfs_device *device, u64 new_size);
 int btrfs_init_new_device(struct btrfs_root *root, char *path);
+int btrfs_init_dev_replace_tgtdev(struct btrfs_root *root, char *device_path,
+				  struct btrfs_device **device_out);
 int btrfs_balance(struct btrfs_balance_control *bctl,
 		  struct btrfs_ioctl_balance_args *bargs);
 int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info);
···
 int btrfs_init_dev_stats(struct btrfs_fs_info *fs_info);
 int btrfs_run_dev_stats(struct btrfs_trans_handle *trans,
 			struct btrfs_fs_info *fs_info);
+void btrfs_rm_dev_replace_srcdev(struct btrfs_fs_info *fs_info,
+				 struct btrfs_device *srcdev);
+void btrfs_destroy_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
+				      struct btrfs_device *tgtdev);
+void btrfs_init_dev_replace_tgtdev_for_resume(struct btrfs_fs_info *fs_info,
+					      struct btrfs_device *tgtdev);
+int btrfs_scratch_superblock(struct btrfs_device *device);
 
 static inline void btrfs_dev_stat_inc(struct btrfs_device *dev,
 				      int index)

fs/btrfs/xattr.c

···
 		 */
 		if (!value)
 			goto out;
+	} else {
+		di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode),
+					name, name_len, 0);
+		if (IS_ERR(di)) {
+			ret = PTR_ERR(di);
+			goto out;
+		}
+		if (!di && !value)
+			goto out;
+		btrfs_release_path(path);
 	}
 
 again:
···
 
 	inode_inc_iversion(inode);
 	inode->i_ctime = CURRENT_TIME;
+	set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
 	ret = btrfs_update_inode(trans, root, inode);
 	BUG_ON(ret);
 out:
···
 
 		di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 		if (verify_dir_item(root, leaf, di))
-			continue;
+			goto next;
 
 		name_len = btrfs_dir_name_len(leaf, di);
 		total_size += name_len + 1;

include/trace/events/btrfs.h

···
 
 #define show_root_type(obj)						\
 	obj, ((obj >= BTRFS_DATA_RELOC_TREE_OBJECTID) ||		\
-	      (obj <= BTRFS_CSUM_TREE_OBJECTID )) ? __show_root_type(obj) : "-"
+	      (obj >= BTRFS_ROOT_TREE_OBJECTID &&			\
+	       obj <= BTRFS_CSUM_TREE_OBJECTID)) ? __show_root_type(obj) : "-"
 
 #define BTRFS_GROUP_FLAGS	\
 	{ BTRFS_BLOCK_GROUP_DATA,	"DATA"}, \