linux-kernel - Re: [PATCH -next 1/3] cpuset: remove redundant special case for null input in node mask update

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Message-ID: <3108a41d-24b2-4a0d-bc71-3e62ff97054b@redhat.com>
Date: Mon, 22 Sep 2025 17:36:57 -0400
From: Waiman Long <llong@...hat.com>
To: Chen Ridong <chenridong@...weicloud.com>, tj@...nel.org,
 hannes@...xchg.org, mkoutny@...e.com
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
 lujialin4@...wei.com, chenridong@...wei.com
Subject: Re: [PATCH -next 1/3] cpuset: remove redundant special case for null
 input in node mask update

On 9/22/25 9:02 AM, Chen Ridong wrote:
> From: Chen Ridong <chenridong@...wei.com>
>
> The nodelist_parse function already handles empty nodemask input
> appropriately, making it unnecessary to handle this case separately
> during the node mask update process.
>
> Signed-off-by: Chen Ridong <chenridong@...wei.com>
> ---
>   kernel/cgroup/cpuset.c | 22 ++++++++--------------
>   1 file changed, 8 insertions(+), 14 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 535174ed7126..20dface3c3e0 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -2847,22 +2847,16 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
>   
>   	/*
>   	 * An empty mems_allowed is ok iff there are no tasks in the cpuset.
> -	 * Since nodelist_parse() fails on an empty mask, we special case
> -	 * that parsing.  The validate_change() call ensures that cpusets
> -	 * with tasks have memory.
> +	 * The validate_change() call ensures that cpusets with tasks have memory.
>   	 */
> -	if (!*buf) {
> -		nodes_clear(trialcs->mems_allowed);
> -	} else {
> -		retval = nodelist_parse(buf, trialcs->mems_allowed);
> -		if (retval < 0)
> -			goto done;
> +	retval = nodelist_parse(buf, trialcs->mems_allowed);
> +	if (retval < 0)
> +		goto done;
>   
> -		if (!nodes_subset(trialcs->mems_allowed,
> -				  top_cpuset.mems_allowed)) {
> -			retval = -EINVAL;
> -			goto done;
> -		}
> +	if (!nodes_subset(trialcs->mems_allowed,
> +			  top_cpuset.mems_allowed)) {
> +		retval = -EINVAL;
> +		goto done;
>   	}
>   
>   	if (nodes_equal(cs->mems_allowed, trialcs->mems_allowed)) {

Right, the *buf check is no longer need with the current version fof 
nodelist_parse().

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