[PATCH v3] fstests: btrfs/150 regression test for reading compressed data

Liu Bo
2017-09-27T17:39:13Z

We had a bug in btrfs compression code which could end up with a
kernel panic.

This is adding a regression test for the bug and I've also sent a
kernel patch to fix the bug.

The patch is "Btrfs: fix kernel oops while reading compressed data".

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
---
v3: - Enable task-filter in debugfs

v2: - Fix ambiguous copyright.
- Use /proc/$pid/make-it-fail to specify IO failure
- Use bash -c to run test only when pid is odd.
- Add test to dangerous group.

tests/btrfs/150 | 105 ++++++++++++++++++++++++++++++++++++++++++++++++++++
tests/btrfs/150.out | 3 ++
tests/btrfs/group | 1 +
3 files changed, 109 insertions(+)
create mode 100755 tests/btrfs/150
create mode 100644 tests/btrfs/150.out

diff --git a/tests/btrfs/150 b/tests/btrfs/150
new file mode 100755
index 0000000..97041b6
--- /dev/null
+++ b/tests/btrfs/150
@@ -0,0 +1,105 @@
+#! /bin/bash
+# FS QA Test btrfs/150
+#
+# This is a regression test which ends up with a kernel oops in btrfs.
+# It occurs when btrfs's read repair happens while reading a compressed
+# extent.
+# The patch to fix it is
+# Btrfs: fix kernel oops while reading compressed data
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2017 Oracle. All Rights Reserved.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it would be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write the Free Software Foundation,
+# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+#-----------------------------------------------------------------------
+#
+
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1 # failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+ cd /
+ rm -f $tmp.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs btrfs
+_supported_os Linux
+_require_scratch
+_require_fail_make_request
+_require_scratch_dev_pool 2
+
+SYSFS_BDEV=`_sysfs_dev $SCRATCH_DEV`
+enable_io_failure()
+{
+ echo 100 > $DEBUGFS_MNT/fail_make_request/probability
+ echo 1000 > $DEBUGFS_MNT/fail_make_request/times
+ echo 0 > $DEBUGFS_MNT/fail_make_request/verbose
+ echo 1 > $DEBUGFS_MNT/fail_make_request/task-filter
+ echo 1 > $SYSFS_BDEV/make-it-fail
+}
+
+disable_io_failure()
+{
+ 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
+}
+
+_scratch_pool_mkfs "-d raid1 -b 1G" >> $seqres.full 2>&1
+
+# It doesn't matter which compression algorithm we use.
+_scratch_mount -ocompress
+
+# Create a file with all data being compressed
+$XFS_IO_PROG -f -c "pwrite -W 0 8K" $SCRATCH_MNT/foobar | _filter_xfs_io
+
+# Raid1 consists of two copies and btrfs decides which copy to read by reader's
+# %pid. Now we inject errors to copy #1 and copy #0 is good. We want to read
+# the bad copy to trigger read-repair.
+while [[ -z $result ]]; do
+ # invalidate the page cache
+ $XFS_IO_PROG -f -c "fadvise -d 0 8K" $SCRATCH_MNT/foobar
+
+ enable_io_failure
+
+ result=$(bash -c "
+ if [ \$((\$\$ % 2)) == 1 ]; then
+ echo 1 > /proc/\$\$/make-it-fail
+ exec $XFS_IO_PROG -c \"pread 0 8K\" \$SCRATCH_MNT/foobar
+ fi")
+
+ disable_io_failure
+done
+
+# success, all done
+status=0
+exit
diff --git a/tests/btrfs/150.out b/tests/btrfs/150.out
new file mode 100644
index 0000000..c492c24
--- /dev/null
+++ b/tests/btrfs/150.out
@@ -0,0 +1,3 @@
+QA output created by 150
+wrote 8192/8192 bytes at offset 0
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
diff --git a/tests/btrfs/group b/tests/btrfs/group
index 70c3f05..e73bb1b 100644
--- a/tests/btrfs/group
+++ b/tests/btrfs/group
@@ -152,3 +152,4 @@
147 auto quick send
148 auto quick rw
149 auto quick send compress
+150 auto quick dangerous
--
2.9.4