linux-ext4 - Re: Filesystem corruption after unreachable storage

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Date:   Thu, 20 Feb 2020 17:14:19 +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


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