linux-kernel - Re: [PATCH] nfsd: move init of percpu reply_cache_stats counters back to nfsd_init

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Date:   Sun, 18 Jun 2023 12:40:19 +0200
From:   Thorsten Leemhuis <regressions@...mhuis.info>
To:     Jeff Layton <jlayton@...nel.org>, Chuck Lever <cel@...nel.org>
Cc:     Chuck Lever <chuck.lever@...cle.com>, Neil Brown <neilb@...e.de>,
        Olga Kornievskaia <kolga@...app.com>,
        Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>,
        stable@...r.kernel.org, Eirik Fuller <efuller@...hat.com>,
        linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nfsd: move init of percpu reply_cache_stats counters back
 to nfsd_init_net

On 16.06.23 22:54, Jeff Layton wrote:
> On Fri, 2023-06-16 at 16:27 -0400, Chuck Lever wrote:
>> Thanks Eirik and Jeff.
>>
>> At this point in the release cycle, I plan to apply this for the
>> next merge window (6.5).
> 
> I think we should take this in sooner. This is a regression and a
> user-triggerable oops in the right situation. If:
> 
> - non-x86_64 arch
> - /proc/fs/nfsd is mounted in the namespace
> - nfsd is not started in the namespace
> - unprivileged user calls "cat /proc/fs/nfsd/reply_cache_stats"

FWIW, might be worth to simply tell Linus about it and let him decide,
that's totally fine and even documented in the old and the new docs for
handling regressions[1].

[1]
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/Documentation/process/handling-regressions.rst?id=eed892da9cd08be76a8f467c600ef58716dbb4d2

>>> Cc: stable@...r.kernel.org # v6.3+
>>> Fixes: f5f9d4a314da ("nfsd: move reply cache initialization into nfsd startup")
>>
>> Why both Fixes: and Cc: stable?
> 
> *shrug* : they mean different things. I can drop the Cc stable.

Please leave it, only a stable tag ensures backporting; a fixes tag
alone is not enough. See [1] above or these recent messages from Greg:

https://lore.kernel.org/all/2023061137-algorithm-almanac-1337@gregkh/
https://lore.kernel.org/all/2023060703-colony-shakily-3514@gregkh/

Ciao, Thorsten