cgroup/cpuset: remove use_parent_ecpus of cpuset

use_parent_ecpus is used to track whether the children are using the
parent's effective_cpus. When a parent's effective_cpus is changed
due to changes in a child partition's effective_xcpus, any child
using parent'effective_cpus must call update_cpumasks_hier. However,
if a child is not a valid partition, it is sufficient to determine
whether to call update_cpumasks_hier based on whether the child's
effective_cpus is going to change. To make the code more succinct,
it is suggested to remove use_parent_ecpus.

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

Author: Chen Ridong

kernel/cgroup/cpuset.c

@@ -185,12 +185,6 @@ struct cpuset {
 	/* partition root state */
 	int partition_root_state;
 
-	/*
-	 * Default hierarchy only:
-	 * use_parent_ecpus - set if using parent's effective_cpus
-	 */
-	int use_parent_ecpus;
-
 	/*
 	 * number of SCHED_DEADLINE tasks attached to this cpuset, so that we
 	 * know when to rebuild associated root domain bandwidth information.
@@ -1505,11 +1499,8 @@ static void reset_partition_data(struct cpuset *cs)
 		if (is_cpu_exclusive(cs))
 			clear_bit(CS_CPU_EXCLUSIVE, &cs->flags);
 	}
-	if (!cpumask_and(cs->effective_cpus,
-			 parent->effective_cpus, cs->cpus_allowed)) {
-		cs->use_parent_ecpus = true;
+	if (!cpumask_and(cs->effective_cpus, parent->effective_cpus, cs->cpus_allowed))
 		cpumask_copy(cs->effective_cpus, parent->effective_cpus);
-	}
 }
 
 /*
@@ -1683,8 +1674,6 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
 	spin_lock_irq(&callback_lock);
 	isolcpus_updated = partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
 	list_add(&cs->remote_sibling, &remote_children);
-	if (cs->use_parent_ecpus)
-		cs->use_parent_ecpus = false;
 	spin_unlock_irq(&callback_lock);
 	update_unbound_workqueue_cpumask(isolcpus_updated);
 
@@ -2309,13 +2298,8 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp,
 		 * it is a partition root that has explicitly distributed
 		 * out all its CPUs.
 		 */
-		if (is_in_v2_mode() && !remote && cpumask_empty(tmp->new_cpus)) {
+		if (is_in_v2_mode() && !remote && cpumask_empty(tmp->new_cpus))
 			cpumask_copy(tmp->new_cpus, parent->effective_cpus);
-			if (!cp->use_parent_ecpus)
-				cp->use_parent_ecpus = true;
-		} else if (cp->use_parent_ecpus) {
-			cp->use_parent_ecpus = false;
-		}
 
 		if (remote)
 			goto get_css;
@@ -2452,8 +2436,7 @@ static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
 	 * Check all its siblings and call update_cpumasks_hier()
 	 * if their effective_cpus will need to be changed.
 	 *
-	 * With the addition of effective_xcpus which is a subset of
-	 * cpus_allowed. It is possible a change in parent's effective_cpus
+	 * It is possible a change in parent's effective_cpus
 	 * due to a change in a child partition's effective_xcpus will impact
 	 * its siblings even if they do not inherit parent's effective_cpus
 	 * directly.
@@ -2467,8 +2450,7 @@ static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
 	cpuset_for_each_child(sibling, pos_css, parent) {
 		if (sibling == cs)
 			continue;
-		if (!sibling->use_parent_ecpus &&
-		    !is_partition_valid(sibling)) {
+		if (!is_partition_valid(sibling)) {
 			compute_effective_cpumask(tmp->new_cpus, sibling,
 						  parent);
 			if (cpumask_equal(tmp->new_cpus, sibling->effective_cpus))
@@ -4128,7 +4110,6 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
 	if (is_in_v2_mode()) {
 		cpumask_copy(cs->effective_cpus, parent->effective_cpus);
 		cs->effective_mems = parent->effective_mems;
-		cs->use_parent_ecpus = true;
 	}
 	spin_unlock_irq(&callback_lock);
 
@@ -4194,9 +4175,6 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css)
 	    is_sched_load_balance(cs))
 		update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
 
-	if (cs->use_parent_ecpus)
-		cs->use_parent_ecpus = false;
-
 	cpuset_dec();
 	clear_bit(CS_ONLINE, &cs->flags);