linux-kernel - Re: [PATCH v5 02/12] common/rc: Add _require_fio

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Message-ID: <40b11ae3-a2ef-440b-9929-ecf4f8c7cdb9@oracle.com>
Date: Tue, 2 Sep 2025 09:29:30 +0100
From: John Garry <john.g.garry@...cle.com>
To: Zorro Lang <zlang@...hat.com>, Ojaswin Mujoo <ojaswin@...ux.ibm.com>
Cc: "Darrick J. Wong" <djwong@...nel.org>, 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 v5 02/12] common/rc: Add _require_fio_version helper

On 30/08/2025 18:09, Zorro Lang wrote:
>> I think John has a bit more background but afaict, RWF_ATOMIC support
>> was added (fio commit: d01612f3ae25) but then removed (commit:
>> a25ba6c64fe1) since the feature didn't make it to kernel in time.
>> However the option seemed to be kept in place. Later, commit 40f1fc11d
>> added the support back in a later version of fio.
>>
>> So yes, I think there are some version where fio will accept atomic=1
>> but not act upon it and the tests may start failing with no apparent
>> reason.
> The concern from Darrick might be a problem. May I ask which fio commit
> brought in this issue, and which fio commit fixed it? If this issue be
> brought in and fixed within a fio release, it might be better. But if it
> crosses fio release, that might be bad, then we might be better to have
> this helper.

The history is that fio atomic write support was originally added some 
time ago for out-of-kernel atomic write support, which was O_ATOMIC 
flag. Since O_ATOMIC never made it into the kernel, the feature was 
removed, but the plumbing for atomic writes stayed in fio - specifically 
the "atomic=" option. So I just reused that plumbing in d01612f3ae25 to 
support RWF_ATOMIC.

The point is that we should check the fio version, as different versions 
can give different behaviour for "atomic" option, those being:
a. O_ATOMIC (we definitely don't want this)
b. no nothing (bad)
c. use RWF_ATOMIC

Thanks,
John