netdev - Re: [PATCH AUTOSEL 6.2 09/30] cpumask: fix incorrect cpumask scanning result checks

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Date:   Sun, 19 Mar 2023 18:59:07 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Guenter Roeck <linux@...ck-us.net>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Vernon Yang <vernon2gm@...il.com>,
        Yury Norov <yury.norov@...il.com>,
        "Jason A . Donenfeld" <Jason@...c4.com>, mpe@...erman.id.au,
        tytso@....edu, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, james.smart@...adcom.com,
        dick.kennedy@...adcom.com, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, christophe.leroy@...roup.eu,
        npiggin@...il.com, dmitry.osipenko@...labora.com, joel@....id.au,
        nathanl@...ux.ibm.com, gustavoars@...nel.org,
        naveen.n.rao@...ux.vnet.ibm.com, linuxppc-dev@...ts.ozlabs.org,
        wireguard@...ts.zx2c4.com, netdev@...r.kernel.org,
        linux-scsi@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 6.2 09/30] cpumask: fix incorrect cpumask scanning
 result checks

On Sun, Mar 19, 2023 at 5:53 PM Sasha Levin <sashal@...nel.org> wrote:
>
> [ Upstream commit 8ca09d5fa3549d142c2080a72a4c70ce389163cd ]

These are technically real fixes, but they are really just "documented
behavior" fixes, and don't actually matter unless you also have
596ff4a09b89 ("cpumask: re-introduce constant-sized cpumask
optimizations"), which doesn't look like stable material.

And if somebody *does* decide to backport commit 596ff4a09b89, you
should then backport all of

  6015b1aca1a2 sched_getaffinity: don't assume 'cpumask_size()' is
fully initialized
  e7304080e0e5 cpumask: relax sanity checking constraints
  63355b9884b3 cpumask: be more careful with 'cpumask_setall()'
  8ca09d5fa354 cpumask: fix incorrect cpumask scanning result checks

but again, none of these matter as long as the constant-sized cpumask
optimized case doesn't exist.

(Technically, FORCE_NR_CPUS also does the constant-size optimizations
even before, but that will complain loudly if that constant size then
doesn't match nr_cpu_ids, so ..).

                   Linus