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

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Date:   Tue, 26 Sep 2017 18:45:51 +0800
From:   Xiao Yang <yangx.jy@...fujitsu.com>
To:     Amir Goldstein <amir73il@...il.com>
CC:     Theodore Ts'o <tytso@....edu>, Eryu Guan <eguan@...hat.com>,
        Josef Bacik <jbacik@...com>, fstests <fstests@...r.kernel.org>,
        Ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [RFC][PATCH] fstest: regression test for ext4 crash consistency
 bug

On 2017/09/25 18:53, Amir Goldstein wrote:
> On Mon, Sep 25, 2017 at 12:49 PM, Xiao Yang<yangx.jy@...fujitsu.com>  wrote:
>> 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@...il.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.
> Now merged as test generic/456
>
>> ---------------------------------------------------------------------------
>> 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?
> I can't say I am doing anything special, but I can say that I get the
> same output as you did when running the test inside kvm-xfstests.
> Actually, I could not reproduce ANY of the the crash consistency bugs
> inside kvm-xfstests. Must be something to do with different timing of
> IO with KVM+virtio disks??
>
> When running on my laptop (Ubuntu 16.04 with latest kernel)
> on a 10G SSD volume, I always get the error reported above.
> I just re-verified with latest stable e2fsprogs (1.43.6).
Hi Amir,

I tested generic/456 with KVM+virtio disks and SATA volumes on some 
kernels (including
v3.10.0, the latest kernel), but i still got the same output as i reported.

Could you determine whether the two different outputs are caused by the 
same bug
or not ?

Thanks,
Xiao Yang.
> Amir.
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