cgroup/cpuset: Streamline rm_siblings_excl_cpus()

If exclusive_cpus is set, effective_xcpus must be a subset of
exclusive_cpus. Currently, rm_siblings_excl_cpus() checks both
exclusive_cpus and effective_xcpus consecutively. It is simpler
to check only exclusive_cpus if non-empty or just effective_xcpus
otherwise.

No functional change is expected.

Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

Author: Waiman-Long

kernel/cgroup/cpuset.c

@@ -1355,23 +1355,29 @@ static int rm_siblings_excl_cpus(struct cpuset *parent, struct cpuset *cs,
 	int retval = 0;
 
 	if (cpumask_empty(excpus))
-		return retval;
+		return 0;
 
 	/*
-	 * Exclude exclusive CPUs from siblings
+	 * Remove exclusive CPUs from siblings
 	 */
 	rcu_read_lock();
 	cpuset_for_each_child(sibling, css, parent) {
+		struct cpumask *sibling_xcpus;
+
 		if (sibling == cs)
 			continue;
 
-		if (cpumask_intersects(excpus, sibling->exclusive_cpus)) {
-			cpumask_andnot(excpus, excpus, sibling->exclusive_cpus);
-			retval++;
-			continue;
-		}
-		if (cpumask_intersects(excpus, sibling->effective_xcpus)) {
-			cpumask_andnot(excpus, excpus, sibling->effective_xcpus);
+		/*
+		 * If exclusive_cpus is defined, effective_xcpus will always
+		 * be a subset. Otherwise, effective_xcpus will only be set
+		 * in a valid partition root.
+		 */
+		sibling_xcpus = cpumask_empty(sibling->exclusive_cpus)
+			      ? sibling->effective_xcpus
+			      : sibling->exclusive_cpus;
+
+		if (cpumask_intersects(excpus, sibling_xcpus)) {
+			cpumask_andnot(excpus, excpus, sibling_xcpus);
 			retval++;
 		}
 	}