linux-ext4 - Re: Filesystem corruption after unreachable storage

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Date:   Tue, 25 Feb 2020 14:19:09 +0100
From:   Jean-Louis Dupond <jean-louis@...ond.be>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: Filesystem corruption after unreachable storage

FYI,

Just did same test with e2fsprogs 1.45.5 (from buster backports) and 
kernel 5.4.13-1~bpo10+1.
And having exactly the same issue.
The VM needs a manual fsck after storage outage.

Don't know if its useful to test with 5.5 or 5.6?
But it seems like the issue still exists.

Thanks
Jean-Louis

On 20/02/2020 17:14, Jean-Louis Dupond wrote:
>
> On 20/02/2020 16:50, Theodore Y. Ts'o wrote:
>> On Thu, Feb 20, 2020 at 10:08:44AM +0100, Jean-Louis Dupond wrote:
>>> dumpe2fs -> see attachment
>> Looking at the dumpe2fs output, it's interesting that it was "clean
>> with errors", without any error information being logged in the
>> superblock.  What version of the kernel are you using?  I'm guessing
>> it's a fairly old one?
> Debian 10 (Buster), with kernel 4.19.67-2+deb10u1
>>> Fsck:
>>> # e2fsck -fy /dev/mapper/vg01-root
>>> e2fsck 1.44.5 (15-Dec-2018)
>> And that's a old version of e2fsck as well.  Is this some kind of
>> stable/enterprise linux distro?
> Debian 10 indeed.
>>> Pass 1: Checking inodes, blocks, and sizes
>>> Inodes that were part of a corrupted orphan linked list found.  Fix? 
>>> yes
>>>
>>> Inode 165708 was part of the orphaned inode list.  FIXED.
>> OK, this and the rest looks like it's relating to a file truncation or
>> deletion at the time of the disconnection.
>>
>>   > > > On KVM for example there is a unlimited timeout (afaik) until 
>> the
>>>>> storage is
>>>>> back, and the VM just continues running after storage recovery.
>>>> Well, you can adjust the SCSI timeout, if you want to give that a 
>>>> try....
>>> It has some other disadvantages? Or is it quite safe to increment 
>>> the SCSI
>>> timeout?
>> It should be pretty safe.
>>
>> Can you reliably reproduce the problem by disconnecting the machine
>> from the SAN?
> Yep, can be reproduced by killing the connection to the SAN while the 
> VM is running, and then after the scsi timeout passed, re-enabled the 
> SAN connection.
> Then reset the machine, and then you need to run an fsck to have it 
> back online.
>>                         - Ted