Re: [PATCH v8 04/11] cgroup/cpuset: Put all task attach related variables into attach_ctx

[Ridong Chen <ridong.chen@linux.dev>]

On 6/27/2026 2:19 AM, Waiman Long wrote:
> Put the task attach related cpuset_attach_old_cs and
> cpuset_attach_nodemask_to static variables into the new attach_ctx
> structure to improve readability and ease maintanence.
> 
> No functional change is expected.
> 
> Suggested-by: Ridong Chen <ridong.chen@linux.dev>
> Signed-off-by: Waiman Long <longman@redhat.com>
> ---
>   kernel/cgroup/cpuset.c | 21 ++++++++++-----------
>   1 file changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index dec9785d0271..1f31f340e0ec 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -362,6 +362,8 @@ static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq);
>    */
>   static struct {
>   	int in_progress;
> +	struct cpuset *old_cs;	/* Source cpuset */
> +	nodemask_t nodemask_to;
>   } attach_ctx;
>   
>   static inline void check_insane_mems_config(nodemask_t *nodes)
> @@ -2996,8 +2998,6 @@ static int update_prstate(struct cpuset *cs, int new_prs)
>   	return 0;
>   }
>   
> -static struct cpuset *cpuset_attach_old_cs;
> -
>   /*
>    * Check to see if a cpuset can accept a new task
>    * For v1, cpus_allowed and mems_allowed can't be empty.
> @@ -3029,8 +3029,8 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
>   	int cpu, ret;
>   
>   	/* used later by cpuset_attach() */
> -	cpuset_attach_old_cs = task_cs(cgroup_taskset_first(tset, &css));
> -	oldcs = cpuset_attach_old_cs;
> +	attach_ctx.old_cs = task_cs(cgroup_taskset_first(tset, &css));
> +	oldcs = attach_ctx.old_cs;
>   	cs = css_cs(css);
>   
>   	mutex_lock(&cpuset_mutex);
> @@ -3133,7 +3133,6 @@ static void cpuset_cancel_attach(struct cgroup_taskset *tset)
>    * allocate from cpuset_init().
>    */
>   static cpumask_var_t cpus_attach;
> -static nodemask_t cpuset_attach_nodemask_to;
>   
>   static void cpuset_attach_task(struct cpuset *cs, struct task_struct *task)
>   {
> @@ -3150,7 +3149,7 @@ static void cpuset_attach_task(struct cpuset *cs, struct task_struct *task)
>   	 */
>   	WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach));
>   
> -	cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to);
> +	cpuset_change_task_nodemask(task, &attach_ctx.nodemask_to);
>   	cpuset1_update_task_spread_flags(cs, task);
>   }
>   
> @@ -3160,7 +3159,7 @@ static void cpuset_attach(struct cgroup_taskset *tset)
>   	struct task_struct *leader;
>   	struct cgroup_subsys_state *css;
>   	struct cpuset *cs;
> -	struct cpuset *oldcs = cpuset_attach_old_cs;
> +	struct cpuset *oldcs = attach_ctx.old_cs;
>   	bool cpus_updated, mems_updated;
>   	bool queue_task_work = false;
>   
> @@ -3172,7 +3171,7 @@ static void cpuset_attach(struct cgroup_taskset *tset)
>   	cpus_updated = !cpumask_equal(cs->effective_cpus,
>   				      oldcs->effective_cpus);
>   	mems_updated = !nodes_equal(cs->effective_mems, oldcs->effective_mems);
> -	guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
> +	guarantee_online_mems(cs, &attach_ctx.nodemask_to);
>   
>   	/*
>   	 * In the default hierarchy, enabling cpuset in the child cgroups
> @@ -3211,7 +3210,7 @@ static void cpuset_attach(struct cgroup_taskset *tset)
>   			 */
>   			if (is_memory_migrate(cs)) {
>   				cpuset_migrate_mm(mm, &oldcs->old_mems_allowed,
> -						  &cpuset_attach_nodemask_to);
> +						  &attach_ctx.nodemask_to);
>   				queue_task_work = true;
>   			} else
>   				mmput(mm);
> @@ -3221,7 +3220,7 @@ static void cpuset_attach(struct cgroup_taskset *tset)
>   out:
>   	if (queue_task_work)
>   		schedule_flush_migrate_mm();
> -	cs->old_mems_allowed = cpuset_attach_nodemask_to;
> +	cs->old_mems_allowed = attach_ctx.nodemask_to;
>   
>   	if (cs->nr_migrate_dl_tasks) {
>   		cs->nr_deadline_tasks += cs->nr_migrate_dl_tasks;
> @@ -3685,7 +3684,7 @@ static void cpuset_fork(struct task_struct *task)
>   
>   	/* CLONE_INTO_CGROUP */
>   	mutex_lock(&cpuset_mutex);
> -	guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
> +	guarantee_online_mems(cs, &attach_ctx.nodemask_to);
>   	cpuset_attach_task(cs, task);
>   
>   	dec_attach_in_progress_locked();

LGTM.

Reviewed-by: Ridong Chen <ridong.chen@linux.dev>

-- 
Best regards
Ridong