Re: [RFC][PATCH] fstest: regression test for ext4 crash consistency bug

[Xiao Yang <yangx.jy@cn.fujitsu.com>]

On 2017/08/27 18:44, Amir Goldstein wrote:
> This test is motivated by a bug found in ext4 during random crash
> consistency tests.
>
> This test uses device mapper flakey target to demonstrate the bug
> found using device mapper log-writes target.
>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>
> Ted,
>
> While working on crash consistency xfstests [1], I stubmled on what
> appeared to be an ext4 crash consistency bug.
>
> The tests I used rely on the log-writes dm target code written
> by Josef Bacik, which had little exposure to the wide community
> as far as I know.  I wanted to prove to myself that the found
> inconsistency was not due to a test bug, so I bisected the failed
> test to the minimal operations that trigger the failure and wrote
> a small independent test to reproduce the issue using dm flakey target.
>
> The following fsck error is reliably reproduced by replaying some fsx ops
> on overlapping file regions, then emulating a crash, followed by mount,
> umount and fsck -nf:
>
>   ./ltp/fsx -d --replay-ops /tmp/8995.fsxops /mnt/scratch/testfile
>   1 write 0x137dd thru    0x21445 (0xdc69 bytes)
>   2 falloc        from 0xb531 to 0x16ade (0xb5ad bytes)
>   3 collapse      from 0x1c000 to 0x20000, (0x4000 bytes)
>   4 write 0x3e5ec thru    0x3ffff (0x1a14 bytes)
>   5 zero  from 0x20fac to 0x27d48, (0x6d9c bytes)
>   6 mapwrite      0x216ad thru    0x23dfb (0x274f bytes)
>   All 7 operations completed A-OK!
>   _check_generic_filesystem: filesystem on /dev/mapper/ssd-scratch is inconsistent
>   *** fsck.ext4 output ***
>   fsck from util-linux 2.27.1
>   e2fsck 1.42.13 (17-May-2015)
>   Pass 1: Checking inodes, blocks, and sizes
>   Inode 12, end of extent exceeds allowed value
>           (logical block 33, physical block 33441, len 7)
>   Clear? no
>   Inode 12, i_blocks is 184, should be 128.  Fix? no
Hi Amir,

I always get the following output when running your xfstests test case 501.
---------------------------------------------------------------------------
e2fsck 1.42.9 (28-Dec-2013)
Pass 1: Checking inodes, blocks, and sizes
Inode 12, i_size is 147456, should be 163840. Fix? no
---------------------------------------------------------------------------

Could you tell me how to get the expected output as you reported?

Thanks,
Xiao Yang
> Note that the inconsistency is "applied" by journal replay during mount.
> fsck -nf before mount does not report any errors.
>
> I did not intend for this test to be merged as is, but rather to be used
> by ext4 developers to analyze the problem and then re-write the test with
> more comments and less arbitrary offset/length values.
>
> P.S.: crash consistency tests also reliably reproduce a btrfs fsck error.
>       a detailed report with I/O recording was sent to Josef.
> P.S.2: crash consistency tests report file data checksum errors on xfs
>        after fsync+crash, but I still need to prove the reliability of
>        these reports.
>  
> [1] https://github.com/amir73il/xfstests/commits/dm-log-writes
>
>  tests/generic/501     | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  tests/generic/501.out |  2 ++
>  tests/generic/group   |  1 +
>  3 files changed, 83 insertions(+)
>  create mode 100755 tests/generic/501
>  create mode 100644 tests/generic/501.out
>
> diff --git a/tests/generic/501 b/tests/generic/501
> new file mode 100755
> index 0000000..ccb513d
> --- /dev/null
> +++ b/tests/generic/501
> @@ -0,0 +1,80 @@
> +#! /bin/bash
> +# FS QA Test No. 501
> +#
> +# This test is motivated by a bug found in ext4 during random crash
> +# consistency tests.
> +#
> +#-----------------------------------------------------------------------
> +# Copyright (C) 2017 CTERA Networks. All Rights Reserved.
> +# Author: Amir Goldstein <amir73il@gmail.com>
> +#
> +# 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!
> +
> +_cleanup()
> +{
> +	_cleanup_flakey
> +	cd /
> +	rm -f $tmp.*
> +}
> +trap "_cleanup; exit \$status" 0 1 2 3 15
> +
> +# get standard environment, filters and checks
> +. ./common/rc
> +. ./common/filter
> +. ./common/dmflakey
> +
> +# real QA test starts here
> +_supported_fs generic
> +_supported_os Linux
> +_require_scratch
> +_require_dm_target flakey
> +_require_metadata_journaling $SCRATCH_DEV
> +
> +rm -f $seqres.full
> +
> +_scratch_mkfs >> $seqres.full 2>&1
> +
> +_init_flakey
> +_mount_flakey
> +
> +fsxops=$tmp.fsxops
> +cat <<EOF > $fsxops
> +write 0x137dd 0xdc69 0x0
> +fallocate 0xb531 0xb5ad 0x21446
> +collapse_range 0x1c000 0x4000 0x21446
> +write 0x3e5ec 0x1a14 0x21446
> +zero_range 0x20fac 0x6d9c 0x40000 keep_size
> +mapwrite 0x216ad 0x274f 0x40000
> +EOF
> +run_check $here/ltp/fsx -d --replay-ops $fsxops $SCRATCH_MNT/testfile
> +
> +_flakey_drop_and_remount
> +_unmount_flakey
> +_cleanup_flakey
> +_check_scratch_fs
> +
> +echo "Silence is golden"
> +
> +status=0
> +exit
> diff --git a/tests/generic/501.out b/tests/generic/501.out
> new file mode 100644
> index 0000000..00133b6
> --- /dev/null
> +++ b/tests/generic/501.out
> @@ -0,0 +1,2 @@
> +QA output created by 501
> +Silence is golden
> diff --git a/tests/generic/group b/tests/generic/group
> index 2396b72..bb870f2 100644
> --- a/tests/generic/group
> +++ b/tests/generic/group
> @@ -454,3 +454,4 @@
>  449 auto quick acl enospc
>  450 auto quick rw
>  500 auto log replay
> +501 auto quick metadata