Btrfs: add mount -o auto_defrag

This will detect small random writes into files and
queue the up for an auto defrag process. It isn't well suited to
database workloads yet, but works for smaller files such as rpm, sqlite
or bdb databases.

Signed-off-by: Chris Mason <[e-mail]>

fs/btrfs/btrfs_inode.h

···
 	unsigned ordered_data_close:1;
 	unsigned orphan_meta_reserved:1;
 	unsigned dummy_inode:1;
+	unsigned in_defrag:1;
 
 	/*
 	 * always compress this one file

fs/btrfs/ctree.h

···
 	/* all metadata allocations go through this cluster */
 	struct btrfs_free_cluster meta_alloc_cluster;
 
+	/* auto defrag inodes go here */
+	spinlock_t defrag_inodes_lock;
+	struct rb_root defrag_inodes;
+	atomic_t defrag_running;
+
 	spinlock_t ref_cache_lock;
 	u64 total_ref_cache_size;
 
···
 	struct super_block anon_super;
 };
 
+struct btrfs_ioctl_defrag_range_args {
+	/* start of the defrag operation */
+	__u64 start;
+
+	/* number of bytes to defrag, use (u64)-1 to say all */
+	__u64 len;
+
+	/*
+	 * flags for the operation, which can include turning
+	 * on compression for this one defrag
+	 */
+	__u64 flags;
+
+	/*
+	 * any extent bigger than this will be considered
+	 * already defragged.  Use 0 to take the kernel default
+	 * Use 1 to say every single extent must be rewritten
+	 */
+	__u32 extent_thresh;
+
+	/*
+	 * which compression method to use if turning on compression
+	 * for this defrag operation.  If unspecified, zlib will
+	 * be used
+	 */
+	__u32 compress_type;
+
+	/* spare for later */
+	__u32 unused[4];
+};
+
+
 /*
  * inode items have the data typically returned from stat and store other
  * info about object characteristics.  There is one for every file and dir in
···
 #define BTRFS_MOUNT_CLEAR_CACHE		(1 << 13)
 #define BTRFS_MOUNT_USER_SUBVOL_RM_ALLOWED (1 << 14)
 #define BTRFS_MOUNT_ENOSPC_DEBUG	 (1 << 15)
+#define BTRFS_MOUNT_AUTO_DEFRAG		(1 << 16)
 
 #define btrfs_clear_opt(o, opt)		((o) &= ~BTRFS_MOUNT_##opt)
 #define btrfs_set_opt(o, opt)		((o) |= BTRFS_MOUNT_##opt)
···
 long btrfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
 void btrfs_update_iflags(struct inode *inode);
 void btrfs_inherit_iflags(struct inode *inode, struct inode *dir);
-
+int btrfs_defrag_file(struct inode *inode, struct file *file,
+		      struct btrfs_ioctl_defrag_range_args *range,
+		      u64 newer_than, unsigned long max_pages);
 /* file.c */
+int btrfs_add_inode_defrag(struct btrfs_trans_handle *trans,
+			   struct inode *inode);
+int btrfs_run_defrag_inodes(struct btrfs_fs_info *fs_info);
 int btrfs_sync_file(struct file *file, int datasync);
 int btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end,
 			    int skip_pinned);

fs/btrfs/disk-io.c

···
 			btrfs_run_delayed_iputs(root);
 			btrfs_clean_old_snapshots(root);
 			mutex_unlock(&root->fs_info->cleaner_mutex);
+			btrfs_run_defrag_inodes(root->fs_info);
 		}
 
 		if (freezing(current)) {
···
 	spin_lock_init(&fs_info->ref_cache_lock);
 	spin_lock_init(&fs_info->fs_roots_radix_lock);
 	spin_lock_init(&fs_info->delayed_iput_lock);
+	spin_lock_init(&fs_info->defrag_inodes_lock);
 
 	init_completion(&fs_info->kobj_unregister);
 	fs_info->tree_root = tree_root;
···
 	atomic_set(&fs_info->async_delalloc_pages, 0);
 	atomic_set(&fs_info->async_submit_draining, 0);
 	atomic_set(&fs_info->nr_async_bios, 0);
+	atomic_set(&fs_info->defrag_running, 0);
 	fs_info->sb = sb;
 	fs_info->max_inline = 8192 * 1024;
 	fs_info->metadata_ratio = 0;
+	fs_info->defrag_inodes = RB_ROOT;
 
 	fs_info->thread_pool_size = min_t(unsigned long,
 					  num_online_cpus() + 2, 8);
···
 	smp_mb();
 
 	btrfs_scrub_cancel(root);
+
+	/* 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(root->fs_info);
+
 	btrfs_put_block_group_cache(fs_info);
 
 	/*

fs/btrfs/file.c

···
 #include "locking.h"
 #include "compat.h"
 
+/*
+ * when auto defrag is enabled we
+ * queue up these defrag structs to remember which
+ * inodes need defragging passes
+ */
+struct inode_defrag {
+	struct rb_node rb_node;
+	/* objectid */
+	u64 ino;
+	/*
+	 * transid where the defrag was added, we search for
+	 * extents newer than this
+	 */
+	u64 transid;
+
+	/* root objectid */
+	u64 root;
+
+	/* last offset we were able to defrag */
+	u64 last_offset;
+
+	/* if we've wrapped around back to zero once already */
+	int cycled;
+};
+
+/* pop a record for an inode into the defrag tree.  The lock
+ * must be held already
+ *
+ * If you're inserting a record for an older transid than an
+ * existing record, the transid already in the tree is lowered
+ *
+ * If an existing record is found the defrag item you
+ * pass in is freed
+ */
+static int __btrfs_add_inode_defrag(struct inode *inode,
+				    struct inode_defrag *defrag)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct inode_defrag *entry;
+	struct rb_node **p;
+	struct rb_node *parent = NULL;
+
+	p = &root->fs_info->defrag_inodes.rb_node;
+	while (*p) {
+		parent = *p;
+		entry = rb_entry(parent, struct inode_defrag, rb_node);
+
+		if (defrag->ino < entry->ino)
+			p = &parent->rb_left;
+		else if (defrag->ino > entry->ino)
+			p = &parent->rb_right;
+		else {
+			/* if we're reinserting an entry for
+			 * an old defrag run, make sure to
+			 * lower the transid of our existing record
+			 */
+			if (defrag->transid < entry->transid)
+				entry->transid = defrag->transid;
+			if (defrag->last_offset > entry->last_offset)
+				entry->last_offset = defrag->last_offset;
+			goto exists;
+		}
+	}
+	BTRFS_I(inode)->in_defrag = 1;
+	rb_link_node(&defrag->rb_node, parent, p);
+	rb_insert_color(&defrag->rb_node, &root->fs_info->defrag_inodes);
+	return 0;
+
+exists:
+	kfree(defrag);
+	return 0;
+
+}
+
+/*
+ * insert a defrag record for this inode if auto defrag is
+ * enabled
+ */
+int btrfs_add_inode_defrag(struct btrfs_trans_handle *trans,
+			   struct inode *inode)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct inode_defrag *defrag;
+	int ret = 0;
+	u64 transid;
+
+	if (!btrfs_test_opt(root, AUTO_DEFRAG))
+		return 0;
+
+	if (root->fs_info->closing)
+		return 0;
+
+	if (BTRFS_I(inode)->in_defrag)
+		return 0;
+
+	if (trans)
+		transid = trans->transid;
+	else
+		transid = BTRFS_I(inode)->root->last_trans;
+
+	defrag = kzalloc(sizeof(*defrag), GFP_NOFS);
+	if (!defrag)
+		return -ENOMEM;
+
+	defrag->ino = inode->i_ino;
+	defrag->transid = transid;
+	defrag->root = root->root_key.objectid;
+
+	spin_lock(&root->fs_info->defrag_inodes_lock);
+	if (!BTRFS_I(inode)->in_defrag)
+		ret = __btrfs_add_inode_defrag(inode, defrag);
+	spin_unlock(&root->fs_info->defrag_inodes_lock);
+	return ret;
+}
+
+/*
+ * must be called with the defrag_inodes lock held
+ */
+struct inode_defrag *btrfs_find_defrag_inode(struct btrfs_fs_info *info, u64 ino,
+					     struct rb_node **next)
+{
+	struct inode_defrag *entry = NULL;
+	struct rb_node *p;
+	struct rb_node *parent = NULL;
+
+	p = info->defrag_inodes.rb_node;
+	while (p) {
+		parent = p;
+		entry = rb_entry(parent, struct inode_defrag, rb_node);
+
+		if (ino < entry->ino)
+			p = parent->rb_left;
+		else if (ino > entry->ino)
+			p = parent->rb_right;
+		else
+			return entry;
+	}
+
+	if (next) {
+		while (parent && ino > entry->ino) {
+			parent = rb_next(parent);
+			entry = rb_entry(parent, struct inode_defrag, rb_node);
+		}
+		*next = parent;
+	}
+	return NULL;
+}
+
+/*
+ * run through the list of inodes in the FS that need
+ * defragging
+ */
+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;
+	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;
+
+		/* find an inode to defrag */
+		defrag = btrfs_find_defrag_inode(fs_info, first_ino, &n);
+		if (!defrag) {
+			if (n)
+				defrag = rb_entry(n, struct inode_defrag, rb_node);
+			else if (first_ino) {
+				first_ino = 0;
+				continue;
+			} else {
+				break;
+			}
+		}
+
+		/* remove it from the rbtree */
+		first_ino = defrag->ino + 1;
+		rb_erase(&defrag->rb_node, &fs_info->defrag_inodes);
+
+		if (fs_info->closing)
+			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 */
+		BTRFS_I(inode)->in_defrag = 0;
+		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);
+	}
+	spin_unlock(&fs_info->defrag_inodes_lock);
+
+	atomic_dec(&fs_info->defrag_running);
+
+	/*
+	 * during unmount, we use the transaction_wait queue to
+	 * wait for the defragger to stop
+	 */
+	wake_up(&fs_info->transaction_wait);
+	return 0;
+}
 
 /* simple helper to fault in pages and copy.  This should go away
  * and be replaced with calls into generic code.

fs/btrfs/inode.c

···
 	int will_compress;
 	int compress_type = root->fs_info->compress_type;
 
+	/* if this is a small write inside eof, kick off a defragbot */
+	if (end <= BTRFS_I(inode)->disk_i_size && (end - start + 1) < 16 * 1024)
+		btrfs_add_inode_defrag(NULL, inode);
+
 	actual_end = min_t(u64, isize, end + 1);
 again:
 	will_compress = 0;
···
 	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 (end <= BTRFS_I(inode)->disk_i_size && num_bytes < 64 * 1024)
+		btrfs_add_inode_defrag(trans, inode);
 
 	if (start == 0) {
 		/* lets try to make an inline extent */
···
 	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;
 
 	alloc_hint = get_extent_allocation_hint(inode, start, len);
···
 	ei->ordered_data_close = 0;
 	ei->orphan_meta_reserved = 0;
 	ei->dummy_inode = 0;
+	ei->in_defrag = 0;
 	ei->force_compress = BTRFS_COMPRESS_NONE;
 
 	ei->delayed_node = NULL;

fs/btrfs/ioctl.c

···
 	return error;
 }
 
+/*
+ * When we're defragging a range, we don't want to kick it off again
+ * if it is really just waiting for delalloc to send it down.
+ * If we find a nice big extent or delalloc range for the bytes in the
+ * file you want to defrag, we return 0 to let you know to skip this
+ * part of the file
+ */
+static int check_defrag_in_cache(struct inode *inode, u64 offset, int thresh)
+{
+	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
+	struct extent_map *em = NULL;
+	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
+	u64 end;
+
+	read_lock(&em_tree->lock);
+	em = lookup_extent_mapping(em_tree, offset, PAGE_CACHE_SIZE);
+	read_unlock(&em_tree->lock);
+
+	if (em) {
+		end = extent_map_end(em);
+		free_extent_map(em);
+		if (end - offset > thresh)
+			return 0;
+	}
+	/* if we already have a nice delalloc here, just stop */
+	thresh /= 2;
+	end = count_range_bits(io_tree, &offset, offset + thresh,
+			       thresh, EXTENT_DELALLOC, 1);
+	if (end >= thresh)
+		return 0;
+	return 1;
+}
+
+/*
+ * helper function to walk through a file and find extents
+ * newer than a specific transid, and smaller than thresh.
+ *
+ * This is used by the defragging code to find new and small
+ * extents
+ */
+static int find_new_extents(struct btrfs_root *root,
+			    struct inode *inode, u64 newer_than,
+			    u64 *off, int thresh)
+{
+	struct btrfs_path *path;
+	struct btrfs_key min_key;
+	struct btrfs_key max_key;
+	struct extent_buffer *leaf;
+	struct btrfs_file_extent_item *extent;
+	int type;
+	int ret;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	min_key.objectid = inode->i_ino;
+	min_key.type = BTRFS_EXTENT_DATA_KEY;
+	min_key.offset = *off;
+
+	max_key.objectid = inode->i_ino;
+	max_key.type = (u8)-1;
+	max_key.offset = (u64)-1;
+
+	path->keep_locks = 1;
+
+	while(1) {
+		ret = btrfs_search_forward(root, &min_key, &max_key,
+					   path, 0, newer_than);
+		if (ret != 0)
+			goto none;
+		if (min_key.objectid != inode->i_ino)
+			goto none;
+		if (min_key.type != BTRFS_EXTENT_DATA_KEY)
+			goto none;
+
+		leaf = path->nodes[0];
+		extent = btrfs_item_ptr(leaf, path->slots[0],
+					struct btrfs_file_extent_item);
+
+		type = btrfs_file_extent_type(leaf, extent);
+		if (type == BTRFS_FILE_EXTENT_REG &&
+		    btrfs_file_extent_num_bytes(leaf, extent) < thresh &&
+		    check_defrag_in_cache(inode, min_key.offset, thresh)) {
+			*off = min_key.offset;
+			btrfs_free_path(path);
+			return 0;
+		}
+
+		if (min_key.offset == (u64)-1)
+			goto none;
+
+		min_key.offset++;
+		btrfs_release_path(path);
+	}
+none:
+	btrfs_free_path(path);
+	return -ENOENT;
+}
+
 static int should_defrag_range(struct inode *inode, u64 start, u64 len,
 			       int thresh, u64 *last_len, u64 *skip,
 			       u64 *defrag_end)
···
 	struct extent_map *em = NULL;
 	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
 	int ret = 1;
-
-
-	if (thresh == 0)
-		thresh = 256 * 1024;
 
 	/*
 	 * make sure that once we start defragging and extent, we keep on
···
 	return ret;
 }
 
-static int btrfs_defrag_file(struct file *file,
-			     struct btrfs_ioctl_defrag_range_args *range)
+/*
+ * it doesn't do much good to defrag one or two pages
+ * at a time.  This pulls in a nice chunk of pages
+ * to COW and defrag.
+ *
+ * It also makes sure the delalloc code has enough
+ * dirty data to avoid making new small extents as part
+ * of the defrag
+ *
+ * It's a good idea to start RA on this range
+ * before calling this.
+ */
+static int cluster_pages_for_defrag(struct inode *inode,
+				    struct page **pages,
+				    unsigned long start_index,
+				    int num_pages)
 {
-	struct inode *inode = fdentry(file)->d_inode;
-	struct btrfs_root *root = BTRFS_I(inode)->root;
-	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
-	struct btrfs_ordered_extent *ordered;
-	struct page *page;
-	struct btrfs_super_block *disk_super;
-	unsigned long last_index;
-	unsigned long ra_pages = root->fs_info->bdi.ra_pages;
-	unsigned long total_read = 0;
-	u64 features;
+	unsigned long file_end;
+	u64 isize = i_size_read(inode);
 	u64 page_start;
 	u64 page_end;
+	int ret;
+	int i;
+	int i_done;
+	struct btrfs_ordered_extent *ordered;
+	struct extent_state *cached_state = NULL;
+
+	if (isize == 0)
+		return 0;
+	file_end = (isize - 1) >> PAGE_CACHE_SHIFT;
+
+	ret = btrfs_delalloc_reserve_space(inode,
+					   num_pages << PAGE_CACHE_SHIFT);
+	if (ret)
+		return ret;
+again:
+	ret = 0;
+	i_done = 0;
+
+	/* step one, lock all the pages */
+	for (i = 0; i < num_pages; i++) {
+		struct page *page;
+		page = grab_cache_page(inode->i_mapping,
+					    start_index + i);
+		if (!page)
+			break;
+
+		if (!PageUptodate(page)) {
+			btrfs_readpage(NULL, page);
+			lock_page(page);
+			if (!PageUptodate(page)) {
+				unlock_page(page);
+				page_cache_release(page);
+				ret = -EIO;
+				break;
+			}
+		}
+		isize = i_size_read(inode);
+		file_end = (isize - 1) >> PAGE_CACHE_SHIFT;
+		if (!isize || page->index > file_end ||
+		    page->mapping != inode->i_mapping) {
+			/* whoops, we blew past eof, skip this page */
+			unlock_page(page);
+			page_cache_release(page);
+			break;
+		}
+		pages[i] = page;
+		i_done++;
+	}
+	if (!i_done || ret)
+		goto out;
+
+	if (!(inode->i_sb->s_flags & MS_ACTIVE))
+		goto out;
+
+	/*
+	 * so now we have a nice long stream of locked
+	 * and up to date pages, lets wait on them
+	 */
+	for (i = 0; i < i_done; i++)
+		wait_on_page_writeback(pages[i]);
+
+	page_start = page_offset(pages[0]);
+	page_end = page_offset(pages[i_done - 1]) + PAGE_CACHE_SIZE;
+
+	lock_extent_bits(&BTRFS_I(inode)->io_tree,
+			 page_start, page_end - 1, 0, &cached_state,
+			 GFP_NOFS);
+	ordered = btrfs_lookup_first_ordered_extent(inode, page_end - 1);
+	if (ordered &&
+	    ordered->file_offset + ordered->len > page_start &&
+	    ordered->file_offset < page_end) {
+		btrfs_put_ordered_extent(ordered);
+		unlock_extent_cached(&BTRFS_I(inode)->io_tree,
+				     page_start, page_end - 1,
+				     &cached_state, GFP_NOFS);
+		for (i = 0; i < i_done; i++) {
+			unlock_page(pages[i]);
+			page_cache_release(pages[i]);
+		}
+		btrfs_wait_ordered_range(inode, page_start,
+					 page_end - page_start);
+		goto again;
+	}
+	if (ordered)
+		btrfs_put_ordered_extent(ordered);
+
+	clear_extent_bit(&BTRFS_I(inode)->io_tree, page_start,
+			  page_end - 1, EXTENT_DIRTY | EXTENT_DELALLOC |
+			  EXTENT_DO_ACCOUNTING, 0, 0, &cached_state,
+			  GFP_NOFS);
+
+	if (i_done != num_pages) {
+		atomic_inc(&BTRFS_I(inode)->outstanding_extents);
+		btrfs_delalloc_release_space(inode,
+				     (num_pages - i_done) << PAGE_CACHE_SHIFT);
+	}
+
+
+	btrfs_set_extent_delalloc(inode, page_start, page_end - 1,
+				  &cached_state);
+
+	unlock_extent_cached(&BTRFS_I(inode)->io_tree,
+			     page_start, page_end - 1, &cached_state,
+			     GFP_NOFS);
+
+	for (i = 0; i < i_done; i++) {
+		clear_page_dirty_for_io(pages[i]);
+		ClearPageChecked(pages[i]);
+		set_page_extent_mapped(pages[i]);
+		set_page_dirty(pages[i]);
+		unlock_page(pages[i]);
+		page_cache_release(pages[i]);
+	}
+	return i_done;
+out:
+	for (i = 0; i < i_done; i++) {
+		unlock_page(pages[i]);
+		page_cache_release(pages[i]);
+	}
+	btrfs_delalloc_release_space(inode, num_pages << PAGE_CACHE_SHIFT);
+	return ret;
+
+}
+
+int btrfs_defrag_file(struct inode *inode, struct file *file,
+		      struct btrfs_ioctl_defrag_range_args *range,
+		      u64 newer_than, unsigned long max_to_defrag)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct btrfs_super_block *disk_super;
+	struct file_ra_state *ra = NULL;
+	unsigned long last_index;
+	u64 features;
 	u64 last_len = 0;
 	u64 skip = 0;
 	u64 defrag_end = 0;
+	u64 newer_off = range->start;
+	int newer_left = 0;
 	unsigned long i;
 	int ret;
+	int defrag_count = 0;
 	int compress_type = BTRFS_COMPRESS_ZLIB;
+	int extent_thresh = range->extent_thresh;
+	int newer_cluster = (256 * 1024) >> PAGE_CACHE_SHIFT;
+	u64 new_align = ~((u64)128 * 1024 - 1);
+	struct page **pages = NULL;
+
+	if (extent_thresh == 0)
+		extent_thresh = 256 * 1024;
 
 	if (range->flags & BTRFS_DEFRAG_RANGE_COMPRESS) {
 		if (range->compress_type > BTRFS_COMPRESS_TYPES)
···
 	if (inode->i_size == 0)
 		return 0;
 
+	/*
+	 * if we were not given a file, allocate a readahead
+	 * context
+	 */
+	if (!file) {
+		ra = kzalloc(sizeof(*ra), GFP_NOFS);
+		if (!ra)
+			return -ENOMEM;
+		file_ra_state_init(ra, inode->i_mapping);
+	} else {
+		ra = &file->f_ra;
+	}
+
+	pages = kmalloc(sizeof(struct page *) * newer_cluster,
+			GFP_NOFS);
+	if (!pages) {
+		ret = -ENOMEM;
+		goto out_ra;
+	}
+
+	/* find the last page to defrag */
 	if (range->start + range->len > range->start) {
 		last_index = min_t(u64, inode->i_size - 1,
 			 range->start + range->len - 1) >> PAGE_CACHE_SHIFT;
···
 		last_index = (inode->i_size - 1) >> PAGE_CACHE_SHIFT;
 	}
 
-	i = range->start >> PAGE_CACHE_SHIFT;
-	while (i <= last_index) {
-		if (!should_defrag_range(inode, (u64)i << PAGE_CACHE_SHIFT,
+	if (newer_than) {
+		ret = find_new_extents(root, inode, newer_than,
+				       &newer_off, 64 * 1024);
+		if (!ret) {
+			range->start = newer_off;
+			/*
+			 * we always align our defrag to help keep
+			 * the extents in the file evenly spaced
+			 */
+			i = (newer_off & new_align) >> PAGE_CACHE_SHIFT;
+			newer_left = newer_cluster;
+		} else
+			goto out_ra;
+	} else {
+		i = range->start >> PAGE_CACHE_SHIFT;
+	}
+	if (!max_to_defrag)
+		max_to_defrag = last_index - 1;
+
+	while (i <= last_index && defrag_count < max_to_defrag) {
+		/*
+		 * make sure we stop running if someone unmounts
+		 * the FS
+		 */
+		if (!(inode->i_sb->s_flags & MS_ACTIVE))
+			break;
+
+		if (!newer_than &&
+		    !should_defrag_range(inode, (u64)i << PAGE_CACHE_SHIFT,
 					PAGE_CACHE_SIZE,
-					range->extent_thresh,
+					extent_thresh,
 					&last_len, &skip,
 					&defrag_end)) {
 			unsigned long next;
···
 			i = max(i + 1, next);
 			continue;
 		}
-
-		if (total_read % ra_pages == 0) {
-			btrfs_force_ra(inode->i_mapping, &file->f_ra, file, i,
-				       min(last_index, i + ra_pages - 1));
-		}
-		total_read++;
-		mutex_lock(&inode->i_mutex);
 		if (range->flags & BTRFS_DEFRAG_RANGE_COMPRESS)
 			BTRFS_I(inode)->force_compress = compress_type;
 
-		ret  = btrfs_delalloc_reserve_space(inode, PAGE_CACHE_SIZE);
-		if (ret)
-			goto err_unlock;
-again:
-		if (inode->i_size == 0 ||
-		    i > ((inode->i_size - 1) >> PAGE_CACHE_SHIFT)) {
-			ret = 0;
-			goto err_reservations;
-		}
+		btrfs_force_ra(inode->i_mapping, ra, file, i, newer_cluster);
 
-		page = grab_cache_page(inode->i_mapping, i);
-		if (!page) {
-			ret = -ENOMEM;
-			goto err_reservations;
-		}
+		ret = cluster_pages_for_defrag(inode, pages, i, newer_cluster);
+		if (ret < 0)
+			goto out_ra;
 
-		if (!PageUptodate(page)) {
-			btrfs_readpage(NULL, page);
-			lock_page(page);
-			if (!PageUptodate(page)) {
-				unlock_page(page);
-				page_cache_release(page);
-				ret = -EIO;
-				goto err_reservations;
+		defrag_count += ret;
+		balance_dirty_pages_ratelimited_nr(inode->i_mapping, ret);
+		i += ret;
+
+		if (newer_than) {
+			if (newer_off == (u64)-1)
+				break;
+
+			newer_off = max(newer_off + 1,
+					(u64)i << PAGE_CACHE_SHIFT);
+
+			ret = find_new_extents(root, inode,
+					       newer_than, &newer_off,
+					       64 * 1024);
+			if (!ret) {
+				range->start = newer_off;
+				i = (newer_off & new_align) >> PAGE_CACHE_SHIFT;
+				newer_left = newer_cluster;
+			} else {
+				break;
 			}
+		} else {
+			i++;
 		}
-
-		if (page->mapping != inode->i_mapping) {
-			unlock_page(page);
-			page_cache_release(page);
-			goto again;
-		}
-
-		wait_on_page_writeback(page);
-
-		if (PageDirty(page)) {
-			btrfs_delalloc_release_space(inode, PAGE_CACHE_SIZE);
-			goto loop_unlock;
-		}
-
-		page_start = (u64)page->index << PAGE_CACHE_SHIFT;
-		page_end = page_start + PAGE_CACHE_SIZE - 1;
-		lock_extent(io_tree, page_start, page_end, GFP_NOFS);
-
-		ordered = btrfs_lookup_ordered_extent(inode, page_start);
-		if (ordered) {
-			unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
-			unlock_page(page);
-			page_cache_release(page);
-			btrfs_start_ordered_extent(inode, ordered, 1);
-			btrfs_put_ordered_extent(ordered);
-			goto again;
-		}
-		set_page_extent_mapped(page);
-
-		/*
-		 * this makes sure page_mkwrite is called on the
-		 * page if it is dirtied again later
-		 */
-		clear_page_dirty_for_io(page);
-		clear_extent_bits(&BTRFS_I(inode)->io_tree, page_start,
-				  page_end, EXTENT_DIRTY | EXTENT_DELALLOC |
-				  EXTENT_DO_ACCOUNTING, GFP_NOFS);
-
-		btrfs_set_extent_delalloc(inode, page_start, page_end, NULL);
-		ClearPageChecked(page);
-		set_page_dirty(page);
-		unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
-
-loop_unlock:
-		unlock_page(page);
-		page_cache_release(page);
-		mutex_unlock(&inode->i_mutex);
-
-		balance_dirty_pages_ratelimited_nr(inode->i_mapping, 1);
-		i++;
 	}
 
 	if ((range->flags & BTRFS_DEFRAG_RANGE_START_IO))
···
 		btrfs_set_super_incompat_flags(disk_super, features);
 	}
 
-	return 0;
+	if (!file)
+		kfree(ra);
+	return defrag_count;
 
-err_reservations:
-	btrfs_delalloc_release_space(inode, PAGE_CACHE_SIZE);
-err_unlock:
-	mutex_unlock(&inode->i_mutex);
+out_ra:
+	if (!file)
+		kfree(ra);
+	kfree(pages);
 	return ret;
 }
 
···
 			/* the rest are all set to zero by kzalloc */
 			range->len = (u64)-1;
 		}
-		ret = btrfs_defrag_file(file, range);
+		ret = btrfs_defrag_file(fdentry(file)->d_inode, file,
+					range, 0, 0);
+		if (ret > 0)
+			ret = 0;
 		kfree(range);
 		break;
 	default:

fs/btrfs/ioctl.h

···
 #define BTRFS_DEFRAG_RANGE_COMPRESS 1
 #define BTRFS_DEFRAG_RANGE_START_IO 2
 
-struct btrfs_ioctl_defrag_range_args {
-	/* start of the defrag operation */
-	__u64 start;
-
-	/* number of bytes to defrag, use (u64)-1 to say all */
-	__u64 len;
-
-	/*
-	 * flags for the operation, which can include turning
-	 * on compression for this one defrag
-	 */
-	__u64 flags;
-
-	/*
-	 * any extent bigger than this will be considered
-	 * already defragged.  Use 0 to take the kernel default
-	 * Use 1 to say every single extent must be rewritten
-	 */
-	__u32 extent_thresh;
-
-	/*
-	 * which compression method to use if turning on compression
-	 * for this defrag operation.  If unspecified, zlib will
-	 * be used
-	 */
-	__u32 compress_type;
-
-	/* spare for later */
-	__u32 unused[4];
-};
-
 struct btrfs_ioctl_space_info {
 	__u64 flags;
 	__u64 total_bytes;

fs/btrfs/super.c

···
 	Opt_compress_type, Opt_compress_force, Opt_compress_force_type,
 	Opt_notreelog, Opt_ratio, Opt_flushoncommit, Opt_discard,
 	Opt_space_cache, Opt_clear_cache, Opt_user_subvol_rm_allowed,
-	Opt_enospc_debug, Opt_subvolrootid, Opt_err,
+	Opt_enospc_debug, Opt_subvolrootid, Opt_defrag, Opt_err,
 };
 
 static match_table_t tokens = {
···
 	{Opt_user_subvol_rm_allowed, "user_subvol_rm_allowed"},
 	{Opt_enospc_debug, "enospc_debug"},
 	{Opt_subvolrootid, "subvolrootid=%d"},
+	{Opt_defrag, "autodefrag"},
 	{Opt_err, NULL},
 };
 
···
 			break;
 		case Opt_enospc_debug:
 			btrfs_set_opt(info->mount_opt, ENOSPC_DEBUG);
+			break;
+		case Opt_defrag:
+			printk(KERN_INFO "btrfs: enabling auto defrag");
+			btrfs_set_opt(info->mount_opt, AUTO_DEFRAG);
 			break;
 		case Opt_err:
 			printk(KERN_INFO "btrfs: unrecognized mount option "