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

[Lu Fengqi <lufq.fnst@cn.fujitsu.com>]

On Wed, Sep 20, 2017 at 05:52:43PM -0600, Liu Bo wrote:
>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>
>---
> tests/btrfs/150     | 102 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> tests/btrfs/150.out |   3 ++
> tests/btrfs/group   |   1 +
> 3 files changed, 106 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..834be51
>--- /dev/null
>+++ b/tests/btrfs/150
>@@ -0,0 +1,102 @@
>+#! /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 for this is 
>+# xxxxx
>+#
>+#-----------------------------------------------------------------------
>+# Copyright (c) 2017 Liu Bo.  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

What does 1000 mean? Enough failures?
Why not set times to -1?

>+        echo 0 > $DEBUGFS_MNT/fail_make_request/verbose
>+        echo 1 > $SYSFS_BDEV/make-it-fail
>+}
>+
>+disable_io_failure()
>+{
>+        echo 0 > $SYSFS_BDEV/make-it-fail
>+        echo 0 > $DEBUGFS_MNT/fail_make_request/probability
>+        echo 0 > $DEBUGFS_MNT/fail_make_request/times
>+}
>+
>+_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 true; do
>+	disable_io_failure
>+	# invalidate the page cache
>+	$XFS_IO_PROG -f -c "fadvise -d 0 128K" $SCRATCH_MNT/foobar | _filter_xfs_io
>+
>+	enable_io_failure
>+	od -x $SCRATCH_MNT/foobar > /dev/null &
>+	pid=$!
>+	wait
>+	[ $((pid % 2)) == 1 ] && break
>+done
>+
>+disable_io_failure
>+
>+# 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..b70a122 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
>-- 
>2.5.0
>
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>

-- 
Thanks,
Lu