cgroup/cpuset: Skip spread flags update on v2

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2077665

commit 18f9a4d
Author: Waiman Long <longman@redhat.com>
Date:   Sat, 12 Nov 2022 17:19:38 -0500

    cgroup/cpuset: Skip spread flags update on v2

    Cpuset v2 has no spread flags to set. So we can skip spread
    flags update if cpuset v2 is being used. Also change the name to
    cpuset_update_task_spread_flags() to indicate that there are multiple
    spread flags.

    Signed-off-by: Waiman Long <longman@redhat.com>
    Signed-off-by: Tejun Heo <tj@kernel.org>

Signed-off-by: Waiman Long <longman@redhat.com>

Author: Waiman-Long

kernel/cgroup/cpuset.c

@@ -550,11 +550,15 @@ static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)
 /*
  * update task's spread flag if cpuset's page/slab spread flag is set
  *
- * Call with callback_lock or cpuset_rwsem held.
+ * Call with callback_lock or cpuset_rwsem held. The check can be skipped
+ * if on default hierarchy.
  */
-static void cpuset_update_task_spread_flag(struct cpuset *cs,
+static void cpuset_update_task_spread_flags(struct cpuset *cs,
 					struct task_struct *tsk)
 {
+	if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys))
+		return;
+
 	if (is_spread_page(cs))
 		task_set_spread_page(tsk);
 	else
@@ -2153,7 +2157,7 @@ static void update_tasks_flags(struct cpuset *cs)
 
 	css_task_iter_start(&cs->css, 0, &it);
 	while ((task = css_task_iter_next(&it)))
-		cpuset_update_task_spread_flag(cs, task);
+		cpuset_update_task_spread_flags(cs, task);
 	css_task_iter_end(&it);
 }
 
@@ -2530,7 +2534,7 @@ static void cpuset_attach(struct cgroup_taskset *tset)
 		WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach));
 
 		cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to);
-		cpuset_update_task_spread_flag(cs, task);
+		cpuset_update_task_spread_flags(cs, task);
 	}
 
 	/*