linux-ext4 - Re: problem with tune2fs after ext4 godown

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Date:   Fri, 31 Aug 2018 22:53:54 +0800
From:   cgxu519 <cgxu519@....com>
To:     Amir Goldstein <amir73il@...il.com>
Cc:     Chengguang Xu <cgxu519@...oud.com>, Eryu Guan <eguan@...hat.com>,
        fstests <fstests@...r.kernel.org>,
        Ext4 <linux-ext4@...r.kernel.org>, Theodore Tso <tytso@....edu>
Subject: Re: problem with tune2fs after ext4 godown

On 08/31/2018 10:28 PM, Amir Goldstein wrote:
> [switching over to ext4 list]
>
> On Fri, Aug 31, 2018 at 5:19 PM cgxu519 <cgxu519@....com> wrote:
>>
>> Hi Amir,
>>
>> It seems godown will cause side effect on ext4/tune2fs, mount an ext4
>> filesystem after running godown,
>> then tune2fs -l <dev> complains like below. so definitely it will not
>> pass d_type check.
>>
>>
>> [root@...1 xfstests-dev]# tune2fs -l /dev/mapper/test-test1
>> tune2fs 1.44.2 (14-May-2018)
>> tune2fs: Superblock checksum does not match superblock while trying to
>> open /dev/mapper/test-test1
>> Couldn't find valid filesystem superblock.
>>
>>
> Chengguang,
>
> Bringing this to the attention of ext4 developers,
> can you please re-iterate the reproducer (without the mention of
> overlayfs and genereic/474) to demonstrate the problem.

steps to reproduce:

1) mount an ext4 fs
2) write a file in the fs
3) sync / or do nothing
4) running godown tool in xfstest to the fs
5) umount the fs
6) mount the fs
7) tune2fs -l <dev>

tune2fs -l will fail with below error.

[root@...1 xfstests-dev]# tune2fs -l /dev/mapper/test-test1
tune2fs 1.44.2 (14-May-2018)
tune2fs: Superblock checksum does not match superblock while trying to
open /dev/mapper/test-test1
Couldn't find valid filesystem superblock.


If I do not write any file in (2), then tune2fs -l in (7) will finish 
successfully.
If I run tune2fs -l during (4) and (5) or during (5) and (6) also finish 
successfully.

NOTE, I don't know this is a real issue or just by design.


Thanks,
Chengguang