[PATCH] fstests: btrfs: enhance regression test for nocsum dio read's repair

[Lu Fengqi]

I catch this following error from dmesg when this testcase fails.

[17446.661127] Buffer I/O error on dev sdb1, logical block 64, async page read

We expect to inject disk IO errors on the device when xfs_io reads the
specific file, but other processes may trigger IO error earlier. So, we
can use task-filter to solve this problem.

Signed-off-by: Lu Fengqi <lufq.f...@cn.fujitsu.com>
---
 tests/btrfs/142 | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/tests/btrfs/142 b/tests/btrfs/142
index 414af1b2..5bd8b728 100755
--- a/tests/btrfs/142
+++ b/tests/btrfs/142
@@ -75,6 +75,7 @@ start_fail()
 {
        echo 100 > $DEBUGFS_MNT/fail_make_request/probability
        echo 2 > $DEBUGFS_MNT/fail_make_request/times
+       echo 1 > $DEBUGFS_MNT/fail_make_request/task-filter
        echo 0 > $DEBUGFS_MNT/fail_make_request/verbose
        echo 1 > $SYSFS_BDEV/make-it-fail
 }
@@ -83,6 +84,7 @@ stop_fail()
 {
        echo 0 > $DEBUGFS_MNT/fail_make_request/probability
        echo 0 > $DEBUGFS_MNT/fail_make_request/times
+       echo 0 > $DEBUGFS_MNT/fail_make_request/task-filter
        echo 0 > $SYSFS_BDEV/make-it-fail
 }
 
@@ -118,16 +120,17 @@ echo "step 3......repair the bad copy" >>$seqres.full
 # since raid1 consists of two copies, and the bad copy was put on stripe #1
 # while the good copy lies on stripe #0, the bad copy only gets access when the
 # reader's pid % 2 == 1 is true
-while true; do
-       # start_fail only fails the following dio read so the repair is
+start_fail
+while [[ -z ${result} ]]; do
+       # enable task-filter only fails the following dio read so the repair is
        # supposed to work.
-       start_fail
-       $XFS_IO_PROG -d -c "pread -b 128K 0 128K" "$SCRATCH_MNT/foobar" > 
/dev/null &
-       pid=$!
-       wait
-       stop_fail
-       [ $((pid % 2)) == 1 ] && break
+       result=$(bash -c "
+       if [[ \$((\$\$ % 2)) -eq 1 ]]; then
+               echo 1 > /proc/\$\$/make-it-fail
+               exec $XFS_IO_PROG -d -c \"pread -b 128K 0 128K\" 
\"$SCRATCH_MNT/foobar\"
+       fi");
 done
+stop_fail
 
 _scratch_unmount
 
-- 
2.14.1



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