1 files changed, 62 insertions, 29 deletions

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 73ef0dabc3..5e468db958 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -21,6 +21,7 @@
  *  License.  See the file COPYING in the main directory of the Linux
  *  distribution for more details.
  */
+#include "cgroup-internal.h"
 
 #include <linux/cpu.h>
 #include <linux/cpumask.h>
@@ -169,7 +170,7 @@ struct cpuset {
 	/* for custom sched domain */
 	int relax_domain_level;
 
-	/* number of valid sub-partitions */
+	/* number of valid local child partitions */
 	int nr_subparts;
 
 	/* partition root state */
@@ -368,9 +369,10 @@ static inline void notify_partition_change(struct cpuset *cs, int old_prs)
 }
 
 static struct cpuset top_cpuset = {
-	.flags = ((1 << CS_ONLINE) | (1 << CS_CPU_EXCLUSIVE) |
-		  (1 << CS_MEM_EXCLUSIVE)),
+	.flags = BIT(CS_ONLINE) | BIT(CS_CPU_EXCLUSIVE) |
+		 BIT(CS_MEM_EXCLUSIVE) | BIT(CS_SCHED_LOAD_BALANCE),
 	.partition_root_state = PRS_ROOT,
+	.relax_domain_level = -1,
 	.remote_sibling = LIST_HEAD_INIT(top_cpuset.remote_sibling),
 };
 
@@ -956,13 +958,15 @@ static int generate_sched_domains(cpumask_var_t **domains,
 	int nslot;		/* next empty doms[] struct cpumask slot */
 	struct cgroup_subsys_state *pos_css;
 	bool root_load_balance = is_sched_load_balance(&top_cpuset);
+	bool cgrpv2 = cgroup_subsys_on_dfl(cpuset_cgrp_subsys);
 
 	doms = NULL;
 	dattr = NULL;
 	csa = NULL;
 
 	/* Special case for the 99% of systems with one, full, sched domain */
-	if (root_load_balance && !top_cpuset.nr_subparts) {
+	if (root_load_balance && cpumask_empty(subpartitions_cpus)) {
+single_root_domain:
 		ndoms = 1;
 		doms = alloc_sched_domains(ndoms);
 		if (!doms)
@@ -990,16 +994,18 @@ static int generate_sched_domains(cpumask_var_t **domains,
 	cpuset_for_each_descendant_pre(cp, pos_css, &top_cpuset) {
 		if (cp == &top_cpuset)
 			continue;
+
+		if (cgrpv2)
+			goto v2;
+
 		/*
+		 * v1:
 		 * Continue traversing beyond @cp iff @cp has some CPUs and
 		 * isn't load balancing.  The former is obvious.  The
 		 * latter: All child cpusets contain a subset of the
 		 * parent's cpus, so just skip them, and then we call
 		 * update_domain_attr_tree() to calc relax_domain_level of
 		 * the corresponding sched domain.
-		 *
-		 * If root is load-balancing, we can skip @cp if it
-		 * is a subset of the root's effective_cpus.
 		 */
 		if (!cpumask_empty(cp->cpus_allowed) &&
 		    !(is_sched_load_balance(cp) &&
@@ -1007,20 +1013,39 @@ static int generate_sched_domains(cpumask_var_t **domains,
 					 housekeeping_cpumask(HK_TYPE_DOMAIN))))
 			continue;
 
-		if (root_load_balance &&
-		    cpumask_subset(cp->cpus_allowed, top_cpuset.effective_cpus))
-			continue;
-
 		if (is_sched_load_balance(cp) &&
 		    !cpumask_empty(cp->effective_cpus))
 			csa[csn++] = cp;
 
-		/* skip @cp's subtree if not a partition root */
-		if (!is_partition_valid(cp))
+		/* skip @cp's subtree */
+		pos_css = css_rightmost_descendant(pos_css);
+		continue;
+
+v2:
+		/*
+		 * Only valid partition roots that are not isolated and with
+		 * non-empty effective_cpus will be saved into csn[].
+		 */
+		if ((cp->partition_root_state == PRS_ROOT) &&
+		    !cpumask_empty(cp->effective_cpus))
+			csa[csn++] = cp;
+
+		/*
+		 * Skip @cp's subtree if not a partition root and has no
+		 * exclusive CPUs to be granted to child cpusets.
+		 */
+		if (!is_partition_valid(cp) && cpumask_empty(cp->exclusive_cpus))
 			pos_css = css_rightmost_descendant(pos_css);
 	}
 	rcu_read_unlock();
 
+	/*
+	 * If there are only isolated partitions underneath the cgroup root,
+	 * we can optimize out unneeded sched domains scanning.
+	 */
+	if (root_load_balance && (csn == 1))
+		goto single_root_domain;
+
 	for (i = 0; i < csn; i++)
 		csa[i]->pn = i;
 	ndoms = csn;
@@ -1063,6 +1088,20 @@ restart:
 	dattr = kmalloc_array(ndoms, sizeof(struct sched_domain_attr),
 			      GFP_KERNEL);
 
+	/*
+	 * Cgroup v2 doesn't support domain attributes, just set all of them
+	 * to SD_ATTR_INIT. Also non-isolating partition root CPUs are a
+	 * subset of HK_TYPE_DOMAIN housekeeping CPUs.
+	 */
+	if (cgrpv2) {
+		for (i = 0; i < ndoms; i++) {
+			cpumask_copy(doms[i], csa[i]->effective_cpus);
+			if (dattr)
+				dattr[i] = SD_ATTR_INIT;
+		}
+		goto done;
+	}
+
 	for (nslot = 0, i = 0; i < csn; i++) {
 		struct cpuset *a = csa[i];
 		struct cpumask *dp;
@@ -1222,7 +1261,7 @@ static void rebuild_sched_domains_locked(void)
 	 * root should be only a subset of the active CPUs.  Since a CPU in any
 	 * partition root could be offlined, all must be checked.
 	 */
-	if (top_cpuset.nr_subparts) {
+	if (!cpumask_empty(subpartitions_cpus)) {
 		rcu_read_lock();
 		cpuset_for_each_descendant_pre(cs, pos_css, &top_cpuset) {
 			if (!is_partition_valid(cs)) {
@@ -3773,9 +3812,6 @@ static ssize_t sched_partition_write(struct kernfs_open_file *of, char *buf,
 
 	buf = strstrip(buf);
 
-	/*
-	 * Convert "root" to ENABLED, and convert "member" to DISABLED.
-	 */
 	if (!strcmp(buf, "root"))
 		val = PRS_ROOT;
 	else if (!strcmp(buf, "member"))
@@ -4051,11 +4087,6 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
 		cs->effective_mems = parent->effective_mems;
 		cs->use_parent_ecpus = true;
 		parent->child_ecpus_count++;
-		/*
-		 * Clear CS_SCHED_LOAD_BALANCE if parent is isolated
-		 */
-		if (!is_sched_load_balance(parent))
-			clear_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
 	}
 
 	/*
@@ -4309,8 +4340,6 @@ int __init cpuset_init(void)
 	nodes_setall(top_cpuset.effective_mems);
 
 	fmeter_init(&top_cpuset.fmeter);
-	set_bit(CS_SCHED_LOAD_BALANCE, &top_cpuset.flags);
-	top_cpuset.relax_domain_level = -1;
 	INIT_LIST_HEAD(&remote_children);
 
 	BUG_ON(!alloc_cpumask_var(&cpus_attach, GFP_KERNEL));
@@ -4580,7 +4609,7 @@ static void cpuset_handle_hotplug(void)
 	 * In the rare case that hotplug removes all the cpus in
 	 * subpartitions_cpus, we assumed that cpus are updated.
 	 */
-	if (!cpus_updated && top_cpuset.nr_subparts)
+	if (!cpus_updated && !cpumask_empty(subpartitions_cpus))
 		cpus_updated = true;
 
 	/* For v1, synchronize cpus_allowed to cpu_active_mask */
@@ -5060,10 +5089,14 @@ int proc_cpuset_show(struct seq_file *m, struct pid_namespace *ns,
 	if (!buf)
 		goto out;
 
-	css = task_get_css(tsk, cpuset_cgrp_id);
-	retval = cgroup_path_ns(css->cgroup, buf, PATH_MAX,
-				current->nsproxy->cgroup_ns);
-	css_put(css);
+	rcu_read_lock();
+	spin_lock_irq(&css_set_lock);
+	css = task_css(tsk, cpuset_cgrp_id);
+	retval = cgroup_path_ns_locked(css->cgroup, buf, PATH_MAX,
+				       current->nsproxy->cgroup_ns);
+	spin_unlock_irq(&css_set_lock);
+	rcu_read_unlock();
+
 	if (retval == -E2BIG)
 		retval = -ENAMETOOLONG;
 	if (retval < 0)