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| author | Robbie Ko <robbieko@synology.com> | 2018-05-07 16:42:04 +0800 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2018-06-07 14:26:29 +0200 |
| commit | 9d311e11fc1f5581d5ec2df0f87ea5a0193c41ad (patch) | |
| tree | 9cc52c328a32674873defef5bfbb26ab3a8abfec /fs/btrfs | |
| parent | 3ca57bd620639eef8bae4adde2d58fc72109e7c8 (diff) | |
| download | linux-9d311e11fc1f5581d5ec2df0f87ea5a0193c41ad.tar.gz | |
Btrfs: fiemap: pass correct bytenr when fm_extent_count is zero
[BUG]
fm_mapped_extents is not correct when fm_extent_count is 0
Like:
# mount /dev/vdb5 /mnt/btrfs
# dd if=/dev/zero bs=16K count=4 oflag=dsync of=/mnt/btrfs/file
# xfs_io -c "fiemap -v" /mnt/btrfs/file
/mnt/btrfs/file:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..127]: 25088..25215 128 0x1
When user space wants to get the number of file extents,
set fm_extent_count to 0 to run fiemap and then read fm_mapped_extents.
In the above example, fiemap will return with fm_mapped_extents set to 4,
but it should be 1 since there's only one entry in the output.
[REASON]
The problem seems to be that disko is only set if
fieinfo->fi_extents_max is set. And this member is initialized, in the
generic ioctl_fiemap function, to the value of used-passed
fm_extent_count. So when the user passes 0 then fi_extent_max is also
set to zero and this causes btrfs to not initialize disko at all.
Eventually this leads emit_fiemap_extent being called with a bogus
'phys' argument preventing proper fiemap entries merging.
[FIX]
Move the disko initialization earlier in extent_fiemap making it
independent of user-passed arguments, allowing emit_fiemap_extent to
properly handle consecutive extent entries.
Signed-off-by: Robbie Ko <robbieko@synology.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs')
| -rw-r--r-- | fs/btrfs/extent_io.c | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index af2f0408c6e4..8e4a7cdbc9f5 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -4545,7 +4545,7 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, offset_in_extent = em_start - em->start; em_end = extent_map_end(em); em_len = em_end - em_start; - disko = 0; + disko = em->block_start + offset_in_extent; flags = 0; /* @@ -4568,8 +4568,6 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, u64 bytenr = em->block_start - (em->start - em->orig_start); - disko = em->block_start + offset_in_extent; - /* * As btrfs supports shared space, this information * can be exported to userspace tools via |