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authorEdmund Nadolski <enadolski@suse.com>2018-03-14 09:03:11 -0600
committerDavid Sterba <dsterba@suse.com>2018-03-14 22:26:46 +0100
commit18bf591ba9753e3e5ba91f38f756a800693408f4 (patch)
tree8468e0438cb96b0a9da970e8dce9b7040a3efa2f
parent047fdea6341966a0898e3b16c51f54d4f5ba030a (diff)
downloadlinux-sh-18bf591ba9753e3e5ba91f38f756a800693408f4.tar.gz
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.c1
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();
}