linux-ext4 - Re: [PATCH v3 05/13] generic/1226: Add atomic write test using fio crc check verifier

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Message-ID: <76974111-88f6-4de8-96bc-9806c6317d19@oracle.com>
Date: Fri, 1 Aug 2025 09:23:46 +0100
From: John Garry <john.g.garry@...cle.com>
To: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
Cc: "Darrick J. Wong" <djwong@...nel.org>, Zorro Lang <zlang@...hat.com>,
        fstests@...r.kernel.org, Ritesh Harjani <ritesh.list@...il.com>,
        tytso@....edu, linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-ext4@...r.kernel.org
Subject: Re: [PATCH v3 05/13] generic/1226: Add atomic write test using fio
 crc check verifier

On 01/08/2025 07:41, Ojaswin Mujoo wrote:
> Got it, I think I can make this test work for ext4 only but then it might
> be more appropriate to run the fio tests directly on atomic blkdev and
> skip the FS, since we anyways want to focus on the storage stack.
> 

testing on ext4 will prove also that the FS and iomap behave correctly 
in that they generate a single bio per atomic write (as well as testing 
the block stack and below).

>>> I'll try to check if we can modify the tests to write on non-overlapping
>>> ranges in a file.
>> JFYI, for testing SW-based atomic writes on XFS, I do something like this. I
>> have multiple threads each writing to separate regions of a file or writing
>> to separate files. I use this for power-fail testing with my RPI. Indeed, I
>> have also being using this sort of test in qemu for shutting down the VM
>> when fio is running - I would like to automate this, but I am not sure how
>> yet.
>>
>> Please let me know if you want further info on the fio script.
> Got it, thanks for the insights. I was thinking of something similar now
> where I can modify the fio files of this test to write on non
> overlapping ranges in the same file. The only doubt i have right now is
> that when I have eg, numjobs=10 filesize=1G, how do i ensure each job
> writes to its own separate range and not overlap with each other.
> 
> I saw the offset_increment= fio options which might help, yet to try it
> out though. If you know any better way please do share.

Yeah, so I use something like:
--numjobs=2 --offset_align=0 --offset_increment=1M --size=1M

Thanks,
John