| From foo@baz Thu Mar 22 14:57:32 CET 2018 |
| From: Filipe Manana <fdmanana@suse.com> |
| Date: Tue, 4 Apr 2017 20:31:00 +0100 |
| Subject: Btrfs: send, fix file hole not being preserved due to inline extent |
| |
| From: Filipe Manana <fdmanana@suse.com> |
| |
| |
| [ Upstream commit e1cbfd7bf6dabdac561c75d08357571f44040a45 ] |
| |
| Normally we don't have inline extents followed by regular extents, but |
| there's currently at least one harmless case where this happens. For |
| example, when the page size is 4Kb and compression is enabled: |
| |
| $ mkfs.btrfs -f /dev/sdb |
| $ mount -o compress /dev/sdb /mnt |
| $ xfs_io -f -c "pwrite -S 0xaa 0 4K" -c "fsync" /mnt/foobar |
| $ xfs_io -c "pwrite -S 0xbb 8K 4K" -c "fsync" /mnt/foobar |
| |
| In this case we get a compressed inline extent, representing 4Kb of |
| data, followed by a hole extent and then a regular data extent. The |
| inline extent was not expanded/converted to a regular extent exactly |
| because it represents 4Kb of data. This does not cause any apparent |
| problem (such as the issue solved by commit e1699d2d7bf6 |
| ("btrfs: add missing memset while reading compressed inline extents")) |
| except trigger an unexpected case in the incremental send code path |
| that makes us issue an operation to write a hole when it's not needed, |
| resulting in more writes at the receiver and wasting space at the |
| receiver. |
| |
| So teach the incremental send code to deal with this particular case. |
| |
| The issue can be currently triggered by running fstests btrfs/137 with |
| compression enabled (MOUNT_OPTIONS="-o compress" ./check btrfs/137). |
| |
| Signed-off-by: Filipe Manana <fdmanana@suse.com> |
| Reviewed-by: Liu Bo <bo.li.liu@oracle.com> |
| Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| fs/btrfs/send.c | 23 +++++++++++++++++++++-- |
| 1 file changed, 21 insertions(+), 2 deletions(-) |
| |
| --- a/fs/btrfs/send.c |
| +++ b/fs/btrfs/send.c |
| @@ -5008,13 +5008,19 @@ static int is_extent_unchanged(struct se |
| while (key.offset < ekey->offset + left_len) { |
| ei = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item); |
| right_type = btrfs_file_extent_type(eb, ei); |
| - if (right_type != BTRFS_FILE_EXTENT_REG) { |
| + if (right_type != BTRFS_FILE_EXTENT_REG && |
| + right_type != BTRFS_FILE_EXTENT_INLINE) { |
| ret = 0; |
| goto out; |
| } |
| |
| right_disknr = btrfs_file_extent_disk_bytenr(eb, ei); |
| - right_len = btrfs_file_extent_num_bytes(eb, ei); |
| + if (right_type == BTRFS_FILE_EXTENT_INLINE) { |
| + right_len = btrfs_file_extent_inline_len(eb, slot, ei); |
| + right_len = PAGE_ALIGN(right_len); |
| + } else { |
| + right_len = btrfs_file_extent_num_bytes(eb, ei); |
| + } |
| right_offset = btrfs_file_extent_offset(eb, ei); |
| right_gen = btrfs_file_extent_generation(eb, ei); |
| |
| @@ -5028,6 +5034,19 @@ static int is_extent_unchanged(struct se |
| goto out; |
| } |
| |
| + /* |
| + * We just wanted to see if when we have an inline extent, what |
| + * follows it is a regular extent (wanted to check the above |
| + * condition for inline extents too). This should normally not |
| + * happen but it's possible for example when we have an inline |
| + * compressed extent representing data with a size matching |
| + * the page size (currently the same as sector size). |
| + */ |
| + if (right_type == BTRFS_FILE_EXTENT_INLINE) { |
| + ret = 0; |
| + goto out; |
| + } |
| + |
| left_offset_fixed = left_offset; |
| if (key.offset < ekey->offset) { |
| /* Fix the right offset for 2a and 7. */ |