linux-kernel - Re: [PATCH] cpuset: Fix the bug that subpart_cpus updated wrongly in update

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Date:   Tue, 18 Jan 2022 15:21:44 -0500
From:   Waiman Long <longman@...hat.com>
To:     Tianchen Ding <dtcccc@...ux.alibaba.com>,
        Zefan Li <lizefan.x@...edance.com>, Tejun Heo <tj@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>
Cc:     cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpuset: Fix the bug that subpart_cpus updated wrongly in
 update_cpumask()

On 1/18/22 05:05, Tianchen Ding wrote:
> subparts_cpus should be limited as a subset of cpus_allowed, but it is
> updated wrongly by using cpumask_andnot(). Use cpumask_and() instead to
> fix it.
>
> Fixes: ee8dde0cd2ce ("cpuset: Add new v2 cpuset.sched.partition flag")
> Signed-off-by: Tianchen Ding <dtcccc@...ux.alibaba.com>
> ---
>   kernel/cgroup/cpuset.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index bb3531e7fda7..804ff5738c5f 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -1635,8 +1635,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
>   	 * Make sure that subparts_cpus is a subset of cpus_allowed.
>   	 */
>   	if (cs->nr_subparts_cpus) {
> -		cpumask_andnot(cs->subparts_cpus, cs->subparts_cpus,
> -			       cs->cpus_allowed);
> +		cpumask_and(cs->subparts_cpus, cs->subparts_cpus, cs->cpus_allowed);
>   		cs->nr_subparts_cpus = cpumask_weight(cs->subparts_cpus);
>   	}
>   	spin_unlock_irq(&callback_lock);

Thanks for the fix.

Reviewed-by: Waiman Long <longman@...hat.com>