cgroup/cpuset: Simplify setsched decision check in task iteration loop of cpuset_can_attach()

Centralize the check required to run security_task_setscheduler() in
the task iteration loop of cpuset_can_attach() outside of the loop as
it has no dependency on the characteristics of the tasks themselves.

There is no functional change.

Signed-off-by: Waiman Long <[email protected]>
Signed-off-by: Tejun Heo <[email protected]>

Author: Waiman-Long

kernel/cgroup/cpuset.c

@@ -2988,7 +2988,7 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
 	struct cgroup_subsys_state *css;
 	struct cpuset *cs, *oldcs;
 	struct task_struct *task;
-	bool cpus_updated, mems_updated;
+	bool setsched_check;
 	int ret;
 
 	/* used later by cpuset_attach() */
@@ -3003,20 +3003,21 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
 	if (ret)
 		goto out_unlock;
 
-	cpus_updated = !cpumask_equal(cs->effective_cpus, oldcs->effective_cpus);
-	mems_updated = !nodes_equal(cs->effective_mems, oldcs->effective_mems);
+	/*
+	 * Skip rights over task setsched check in v2 when nothing changes,
+	 * migration permission derives from hierarchy ownership in
+	 * cgroup_procs_write_permission()).
+	 */
+	setsched_check = !cpuset_v2() ||
+		!cpumask_equal(cs->effective_cpus, oldcs->effective_cpus) ||
+		!nodes_equal(cs->effective_mems, oldcs->effective_mems);
 
 	cgroup_taskset_for_each(task, css, tset) {
 		ret = task_can_attach(task);
 		if (ret)
 			goto out_unlock;
 
-		/*
-		 * Skip rights over task check in v2 when nothing changes,
-		 * migration permission derives from hierarchy ownership in
-		 * cgroup_procs_write_permission()).
-		 */
-		if (!cpuset_v2() || (cpus_updated || mems_updated)) {
+		if (setsched_check) {
 			ret = security_task_setscheduler(task);
 			if (ret)
 				goto out_unlock;