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| author | Edmund Nadolski <enadolski@suse.com> | 2018-03-14 09:03:11 -0600 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2018-03-14 22:26:46 +0100 |
| commit | 18bf591ba9753e3e5ba91f38f756a800693408f4 (patch) | |
| tree | 8468e0438cb96b0a9da970e8dce9b7040a3efa2f | |
| parent | 047fdea6341966a0898e3b16c51f54d4f5ba030a (diff) | |
| download | linux-18bf591ba9753e3e5ba91f38f756a800693408f4.tar.bz2 | |
btrfs: add missing initialization in btrfs_check_shared
This patch addresses an issue that causes fiemap to falsely
report a shared extent. The test case is as follows:
xfs_io -f -d -c "pwrite -b 16k 0 64k" -c "fiemap -v" /media/scratch/file5
sync
xfs_io -c "fiemap -v" /media/scratch/file5
which gives the resulting output:
wrote 65536/65536 bytes at offset 0
64 KiB, 4 ops; 0.0000 sec (121.359 MiB/sec and 7766.9903 ops/sec)
/media/scratch/file5:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..127]: 24576..24703 128 0x2001
/media/scratch/file5:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..127]: 24576..24703 128 0x1
This is because btrfs_check_shared calls find_parent_nodes
repeatedly in a loop, passing a share_check struct to report
the count of shared extent. But btrfs_check_shared does not
re-initialize the count value to zero for subsequent calls
from the loop, resulting in a false share count value. This
is a regressive behavior from 4.13.
With proper re-initialization the test result is as follows:
wrote 65536/65536 bytes at offset 0
64 KiB, 4 ops; 0.0000 sec (110.035 MiB/sec and 7042.2535 ops/sec)
/media/scratch/file5:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..127]: 24576..24703 128 0x1
/media/scratch/file5:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..127]: 24576..24703 128 0x1
which corrects the regression.
Fixes: 3ec4d3238ab ("btrfs: allow backref search checks for shared extents")
Signed-off-by: Edmund Nadolski <enadolski@suse.com>
[ add text from cover letter to changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
| -rw-r--r-- | fs/btrfs/backref.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c index f94b2d8c744a..26484648d090 100644 --- a/fs/btrfs/backref.c +++ b/fs/btrfs/backref.c @@ -1519,6 +1519,7 @@ int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr) if (!node) break; bytenr = node->val; + shared.share_count = 0; cond_resched(); } |