f2fs: avoid infinite GC loop due to stale atomic files

If committing atomic pages is failed when doing f2fs_do_sync_file(), we can
get commited pages but atomic_file being still set like:

- inmem: 0, atomic IO: 4 (Max. 10), volatile IO: 0 (Max. 0)

If GC selects this block, we can get an infinite loop like this:

f2fs_submit_page_bio: dev = (253,7), ino = 2, page_index = 0x2359a8, oldaddr = 0x2359a8, newaddr = 0x2359a8, rw = READ(), type = COLD_DATA
f2fs_submit_read_bio: dev = (253,7)/(253,7), rw = READ(), DATA, sector = 18533696, size = 4096
f2fs_get_victim: dev = (253,7), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 4355, cost = 1, ofs_unit = 1, pre_victim_secno = 4355, prefree = 0, free = 234
f2fs_iget: dev = (253,7), ino = 6247, pino = 5845, i_mode = 0x81b0, i_size = 319488, i_nlink = 1, i_blocks = 624, i_advise = 0x2c
f2fs_submit_page_bio: dev = (253,7), ino = 2, page_index = 0x2359a8, oldaddr = 0x2359a8, newaddr = 0x2359a8, rw = READ(), type = COLD_DATA
f2fs_submit_read_bio: dev = (253,7)/(253,7), rw = READ(), DATA, sector = 18533696, size = 4096
f2fs_get_victim: dev = (253,7), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 4355, cost = 1, ofs_unit = 1, pre_victim_secno = 4355, prefree = 0, free = 234
f2fs_iget: dev = (253,7), ino = 6247, pino = 5845, i_mode = 0x81b0, i_size = 319488, i_nlink = 1, i_blocks = 624, i_advise = 0x2c

In that moment, we can observe:

[Before]
Try to move 5084219 blocks (BG: 384508)
- data blocks : 4962373 (274483)
- node blocks : 121846 (110025)
Skipped : atomic write 4534686 (10)

[After]
Try to move 5088973 blocks (BG: 384508)
- data blocks : 4967127 (274483)
- node blocks : 121846 (110025)
Skipped : atomic write 4539440 (10)

So, refactor atomic_write flow like this:
1. start_atomic_write
- add inmem_list and set atomic_file

2. write()
- register it in inmem_pages

3. commit_atomic_write
- if no error, f2fs_drop_inmem_pages()
- f2fs_commit_inmme_pages() failed
: __revoked_inmem_pages() was done
- f2fs_do_sync_file failed
: abort_atomic_write later

4. abort_atomic_write
- f2fs_drop_inmem_pages

5. f2fs_drop_inmem_pages
- clear atomic_file
- remove inmem_list

Based on this change, when GC fails to move block in atomic_file,
f2fs_drop_inmem_pages_all() can call f2fs_drop_inmem_pages().

Reviewed-by: Chao Yu <[e-mail]>
Signed-off-by: Jaegeuk Kim <[e-mail]>

fs/f2fs/file.c

···
 static int f2fs_ioc_start_atomic_write(struct file *filp)
 {
 	struct inode *inode = file_inode(filp);
+	struct f2fs_inode_info *fi = F2FS_I(inode);
+	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	int ret;
 
 	if (!inode_owner_or_capable(inode))
···
 		goto out;
 	}
 
+	spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
+	if (list_empty(&fi->inmem_ilist))
+		list_add_tail(&fi->inmem_ilist, &sbi->inode_list[ATOMIC_FILE]);
+	spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
+
+	/* add inode in inmem_list first and set atomic_file */
 	set_inode_flag(inode, FI_ATOMIC_FILE);
 	clear_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST);
 	up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
···
 			goto err_out;
 
 		ret = f2fs_do_sync_file(filp, 0, LLONG_MAX, 0, true);
-		if (!ret) {
-			clear_inode_flag(inode, FI_ATOMIC_FILE);
-			F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC] = 0;
-			stat_dec_atomic_write(inode);
-		}
+		if (!ret)
+			f2fs_drop_inmem_pages(inode);
 	} else {
 		ret = f2fs_do_sync_file(filp, 0, LLONG_MAX, 1, false);
 	}

fs/f2fs/segment.c

···
 
 void f2fs_register_inmem_page(struct inode *inode, struct page *page)
 {
-	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
-	struct f2fs_inode_info *fi = F2FS_I(inode);
 	struct inmem_pages *new;
 
 	f2fs_trace_pid(page);
···
 	INIT_LIST_HEAD(&new->list);
 
 	/* increase reference count with clean state */
-	mutex_lock(&fi->inmem_lock);
 	get_page(page);
-	list_add_tail(&new->list, &fi->inmem_pages);
-	spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
-	if (list_empty(&fi->inmem_ilist))
-		list_add_tail(&fi->inmem_ilist, &sbi->inode_list[ATOMIC_FILE]);
-	spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
+	mutex_lock(&F2FS_I(inode)->inmem_lock);
+	list_add_tail(&new->list, &F2FS_I(inode)->inmem_pages);
 	inc_page_count(F2FS_I_SB(inode), F2FS_INMEM_PAGES);
-	mutex_unlock(&fi->inmem_lock);
+	mutex_unlock(&F2FS_I(inode)->inmem_lock);
 
 	trace_f2fs_register_inmem_page(page, INMEM);
 }
···
 		mutex_lock(&fi->inmem_lock);
 		__revoke_inmem_pages(inode, &fi->inmem_pages,
 						true, false, true);
-
-		if (list_empty(&fi->inmem_pages)) {
-			spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
-			if (!list_empty(&fi->inmem_ilist))
-				list_del_init(&fi->inmem_ilist);
-			spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
-		}
 		mutex_unlock(&fi->inmem_lock);
 	}
 
 	clear_inode_flag(inode, FI_ATOMIC_FILE);
 	fi->i_gc_failures[GC_FAILURE_ATOMIC] = 0;
 	stat_dec_atomic_write(inode);
+
+	spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
+	if (!list_empty(&fi->inmem_ilist))
+		list_del_init(&fi->inmem_ilist);
+	spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
 }
 
 void f2fs_drop_inmem_page(struct inode *inode, struct page *page)
···
 
 	mutex_lock(&fi->inmem_lock);
 	err = __f2fs_commit_inmem_pages(inode);
-
-	spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
-	if (!list_empty(&fi->inmem_ilist))
-		list_del_init(&fi->inmem_ilist);
-	spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
 	mutex_unlock(&fi->inmem_lock);
 
 	clear_inode_flag(inode, FI_ATOMIC_COMMIT);