cpuset: Make generate_sched_domains() work with partition

The generate_sched_domains() function is modified to make it work
correctly with the newly introduced subparts_cpus mask for scheduling
domains generation.

Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 82c88c60c83d65443eb4f35b6d92d0afd5ac9dae..3960de7a75ccf999e8e9de8b4da7534900060637 100644 (file)
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -769,13 +769,14 @@ static int generate_sched_domains(cpumask_var_t **domains,
        int ndoms = 0;          /* number of sched domains in result */
        int nslot;              /* next empty doms[] struct cpumask slot */
        struct cgroup_subsys_state *pos_css;
+       bool root_load_balance = is_sched_load_balance(&top_cpuset);
 
        doms = NULL;
        dattr = NULL;
        csa = NULL;
 
        /* Special case for the 99% of systems with one, full, sched domain */
-       if (is_sched_load_balance(&top_cpuset)) {
+       if (root_load_balance && !top_cpuset.nr_subparts_cpus) {
                ndoms = 1;
                doms = alloc_sched_domains(ndoms);
                if (!doms)
@@ -798,6 +799,8 @@ static int generate_sched_domains(cpumask_var_t **domains,
        csn = 0;
 
        rcu_read_lock();
+       if (root_load_balance)
+               csa[csn++] = &top_cpuset;
        cpuset_for_each_descendant_pre(cp, pos_css, &top_cpuset) {
                if (cp == &top_cpuset)
                        continue;
@@ -808,6 +811,9 @@ static int generate_sched_domains(cpumask_var_t **domains,
                 * 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) &&
@@ -815,11 +821,16 @@ static int generate_sched_domains(cpumask_var_t **domains,
                                         housekeeping_cpumask(HK_FLAG_DOMAIN))))
                        continue;
 
+               if (root_load_balance &&
+                   cpumask_subset(cp->cpus_allowed, top_cpuset.effective_cpus))
+                       continue;
+
                if (is_sched_load_balance(cp))
                        csa[csn++] = cp;
 
-               /* skip @cp's subtree */
-               pos_css = css_rightmost_descendant(pos_css);
+               /* skip @cp's subtree if not a partition root */
+               if (!is_partition_root(cp))
+                       pos_css = css_rightmost_descendant(pos_css);
        }
        rcu_read_unlock();
 
@@ -947,7 +958,12 @@ static void rebuild_sched_domains_locked(void)
         * passing doms with offlined cpu to partition_sched_domains().
         * Anyways, hotplug work item will rebuild sched domains.
         */
-       if (!cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
+       if (!top_cpuset.nr_subparts_cpus &&
+           !cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
+               goto out;
+
+       if (top_cpuset.nr_subparts_cpus &&
+          !cpumask_subset(top_cpuset.effective_cpus, cpu_active_mask))
                goto out;
 
        /* Generate domain masks and attrs */
@@ -1367,11 +1383,15 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
                update_tasks_cpumask(cp);
 
                /*
-                * If the effective cpumask of any non-empty cpuset is changed,
-                * we need to rebuild sched domains.
+                * On legacy hierarchy, if the effective cpumask of any non-
+                * empty cpuset is changed, we need to rebuild sched domains.
+                * On default hierarchy, the cpuset needs to be a partition
+                * root as well.
                 */
                if (!cpumask_empty(cp->cpus_allowed) &&
-                   is_sched_load_balance(cp))
+                   is_sched_load_balance(cp) &&
+                  (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
+                   is_partition_root(cp)))
                        need_rebuild_sched_domains = true;
 
                rcu_read_lock();