[BUG] After commit ab41f0bddb73 ("common/btrfs: use _scratch_cycle_mount to ensure all page caches are dropped"), the test case btrfs/143 can fail like below: btrfs/143 6s ... [failed, exit status 1]- output mismatch (see ~/xfstests/results//btrfs/143.out.bad) --- tests/btrfs/143.out 2020-06-10 19:29:03.818519162 +0100 +++ ~/xfstests/results//btrfs/143.out.bad 2023-06-19 17:04:00.575033899 +0100 @@ -1,37 +1,6 @@ QA output created by 143 wrote 131072/131072 bytes XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) -XXXXXXXX: aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................ -XXXXXXXX: aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................ -XXXXXXXX: aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................ -XXXXXXXX: aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................ [CAUSE] Test case btrfs/143 uses dm-dust device to emulate read errors, this means we can not use _scratch_cycle_mount to cycle mount $SCRATCH_MNT. As it would go mount $SCRATCH_DEV, not the dm-dust device to $SCRATCH_MNT. This prevents us to trigger read-repair (since no error would be hit) thus fail the test. [FIX] Since we can mount whatever device at $SCRATCH_MNT, we can not use _scratch_cycle_mount in this case. Instead implement a small helper to grab the mounted device and its mount options, and use the same device and mount options to cycle $SCRATCH_MNT mount. This would fix btrfs/143 and hopefully future test cases which use dm devices. Reported-by: Filipe Manana <fdmanana@xxxxxxxx> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> --- common/btrfs | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/common/btrfs b/common/btrfs index 175b33ae..4a02b2cc 100644 --- a/common/btrfs +++ b/common/btrfs @@ -601,8 +601,18 @@ _btrfs_buffered_read_on_mirror() # The drop_caches doesn't seem to drop every pages on aarch64 with # 64K page size. # So here as another workaround, cycle mount the SCRATCH_MNT to ensure - # the cache are dropped. - _scratch_cycle_mount + # the cache are dropped, but we can not use _scratch_cycle_mount, as + # we may mount whatever dm device at SCRATCH_MNT. + # So here we grab the mounted block device and its mount options, then + # unmount and re-mount with the same device and options. + local mount_info=$(_mount | grep "$SCRATCH_MNT") + if [ -z "$mount_info" ]; then + _fail "failed to grab mount info of $SCRATCH_MNT" + fi + local dev=$(echo $mount_info | $AWK_PROG '{print $1}') + local opts=$(echo $mount_info | $AWK_PROG '{print $6}' | sed 's/[()]//g') + _scratch_unmount + _mount $dev -o $opts $SCRATCH_MNT while [[ -z $( (( BASHPID % nr_mirrors == mirror )) && exec $XFS_IO_PROG \ -c "pread -b $size $offset $size" $file) ]]; do -- 2.39.0