Btrfs: fix assertion on fsync of regular file when using no-holes feature

fdmanana · kdave · commit 7ed586d0a824 · 2018-10-17T17:44:53.000+02:00
When using the NO_HOLES feature and logging a regular file, we were expecting that if we find an inline extent, that either its size in RAM (uncompressed and unenconded) matches the size of the file or if it does not, that it matches the sector size and it represents compressed data. This assertion does not cover a case where the length of the inline extent is smaller than the sector size and also smaller the file's size, such case is possible through fallocate. Example: $ mkfs.btrfs -f -O no-holes /dev/sdb $ mount /dev/sdb /mnt $ xfs_io -f -c "pwrite -S 0xb60 0 21" /mnt/foobar $ xfs_io -c "falloc 40 40" /mnt/foobar $ xfs_io -c "fsync" /mnt/foobar In the above example we trigger the assertion because the inline extent's length is 21 bytes while the file size is 80 bytes. The fallocate() call merely updated the file's size and did not touch the existing inline extent, as expected. So fix this by adjusting the assertion so that an inline extent length smaller than the file size is valid if the file size is smaller than the filesystem's sector size. A test case for fstests follows soon. Reported-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com> Fixes: a89ca6f ("Btrfs: fix fsync after truncate when no_holes feature is enabled") CC: stable@vger.kernel.org # 4.14+ Link: https://lore.kernel.org/linux-btrfs/CAE5jQCfRSBC7n4pUTFJcmHh109=gwyT9mFkCOL+NKfzswmR=_Q@mail.gmail.com/ Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
@@ -4652,7 +4652,8 @@ static int btrfs_log_trailing_hole(struct btrfs_trans_handle *trans,
 			ASSERT(len == i_size ||
 			       (len == fs_info->sectorsize &&
 				btrfs_file_extent_compression(leaf, extent) !=
-				BTRFS_COMPRESS_NONE));
+				BTRFS_COMPRESS_NONE) ||
+			       (len < i_size && i_size < fs_info->sectorsize));
 			return 0;
 		}
 

Original file line number	Diff line number	Diff line change
`@@ -4652,7 +4652,8 @@ static int btrfs_log_trailing_hole(struct btrfs_trans_handle *trans,`
`4652`	`4652`	`ASSERT(len == i_size \|\|`
`4653`	`4653`	`(len == fs_info->sectorsize &&`
`4654`	`4654`	`btrfs_file_extent_compression(leaf, extent) !=`
`4655`		`- BTRFS_COMPRESS_NONE));`
	`4655`	`+ BTRFS_COMPRESS_NONE) \|\|`
	`4656`	`+ (len < i_size && i_size < fs_info->sectorsize));`
`4656`	`4657`	`return 0;`
`4657`	`4658`	`}`
`4658`	`4659`