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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sun, 19 Mar 2023 18:59:07 -0700
Message-ID: <CAHk-=wgpK-Gm-nOybRKs1LTD5yb7rPHQ4+=PCDvq61mUpBskYw@mail.gmail.com>
Subject: Re: [PATCH AUTOSEL 6.2 09/30] cpumask: fix incorrect cpumask scanning
 result checks
To:     Sasha Levin <sashal@kernel.org>
Cc:     linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        Guenter Roeck <linux@roeck-us.net>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Vernon Yang <vernon2gm@gmail.com>,
        Yury Norov <yury.norov@gmail.com>,
        "Jason A . Donenfeld" <Jason@zx2c4.com>, mpe@ellerman.id.au,
        tytso@mit.edu, davem@davemloft.net, edumazet@google.com,
        kuba@kernel.org, pabeni@redhat.com, james.smart@broadcom.com,
        dick.kennedy@broadcom.com, jejb@linux.ibm.com,
        martin.petersen@oracle.com, christophe.leroy@csgroup.eu,
        npiggin@gmail.com, dmitry.osipenko@collabora.com, joel@jms.id.au,
        nathanl@linux.ibm.com, gustavoars@kernel.org,
        naveen.n.rao@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org,
        wireguard@lists.zx2c4.com, netdev@vger.kernel.org,
        linux-scsi@vger.kernel.org
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On Sun, Mar 19, 2023 at 5:53=E2=80=AFPM Sasha Levin <sashal@kernel.org> wro=
te:
>
> [ 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