linux-kernel - Re: [PATCH -next 2/3] cgroup/cpuset: remove fetch

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Message-ID: <c1225ca7-5b4a-42f8-bb16-f435c6137d95@redhat.com>
Date: Mon, 19 Aug 2024 14:28:05 -0400
From: Waiman Long <longman@...hat.com>
To: Chen Ridong <chenridong@...wei.com>, tj@...nel.org,
 lizefan.x@...edance.com, hannes@...xchg.org, adityakali@...gle.com,
 sergeh@...nel.org, mkoutny@...e.com
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next 2/3] cgroup/cpuset: remove fetch_xcpus

On 8/16/24 04:27, Chen Ridong wrote:
> Both fetch_xcpus and user_xcpus functions are used to retrieve the value
> of exclusive_cpus. If exclusive_cpus is not set, cpus_allowed is the
> implicit value used as exclusive in a local partition. I can not imagine
> a scenario where effective_xcpus is not empty when exclusive_cpus is
> empty. Therefore, I suggest removing the fetch_xcpus function.
>
> Signed-off-by: Chen Ridong <chenridong@...wei.com>
> ---
>   kernel/cgroup/cpuset.c | 13 +++----------
>   1 file changed, 3 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index fdd5346616d3..8be0259065f5 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -771,13 +771,6 @@ static inline bool xcpus_empty(struct cpuset *cs)
>   	       cpumask_empty(cs->exclusive_cpus);
>   }
>   
> -static inline struct cpumask *fetch_xcpus(struct cpuset *cs)
> -{
> -	return !cpumask_empty(cs->exclusive_cpus) ? cs->exclusive_cpus :
> -	       cpumask_empty(cs->effective_xcpus) ? cs->cpus_allowed
> -						  : cs->effective_xcpus;
> -}
> -
>   /*
>    * cpusets_are_exclusive() - check if two cpusets are exclusive
>    *
> @@ -785,8 +778,8 @@ static inline struct cpumask *fetch_xcpus(struct cpuset *cs)
>    */
>   static inline bool cpusets_are_exclusive(struct cpuset *cs1, struct cpuset *cs2)
>   {
> -	struct cpumask *xcpus1 = fetch_xcpus(cs1);
> -	struct cpumask *xcpus2 = fetch_xcpus(cs2);
> +	struct cpumask *xcpus1 = user_xcpus(cs1);
> +	struct cpumask *xcpus2 = user_xcpus(cs2);
>   
>   	if (cpumask_intersects(xcpus1, xcpus2))
>   		return false;
> @@ -2585,7 +2578,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
>   		invalidate = true;
>   		rcu_read_lock();
>   		cpuset_for_each_child(cp, css, parent) {
> -			struct cpumask *xcpus = fetch_xcpus(trialcs);
> +			struct cpumask *xcpus = user_xcpus(trialcs);
>   
>   			if (is_partition_valid(cp) &&
>   			    cpumask_intersects(xcpus, cp->effective_xcpus)) {

LGTM.

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