cgroup/cpuset: Don't track # of local child partitions

The cpuset structure has a nr_subparts field which tracks the number
of child local partitions underneath a particular cpuset. Right now,
nr_subparts is only used in partition_is_populated() to avoid iteration
of child cpusets if the condition is right. So by always performing the
child iteration, we can avoid tracking the number of child partitions
and simplify the code a bit.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/cgroup/cpuset-internal.h b/kernel/cgroup/cpuset-internal.h
index 337608f408ce0a95560de8afda90ec28319bd1b2..5cac42c5fd9727c1b5021d92158b00cdd205c0d3 100644 (file)
--- a/kernel/cgroup/cpuset-internal.h
+++ b/kernel/cgroup/cpuset-internal.h
@@ -155,9 +155,6 @@ struct cpuset {
        /* for custom sched domain */
        int relax_domain_level;
 
-       /* number of valid local child partitions */
-       int nr_subparts;
-
        /* partition root state */
        int partition_root_state;
 

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 52468d2c178a3ef6b71d42f3b4fff748d0943cf6..7aef59ea962765cc06d83b6807d237fff690c5eb 100644 (file)
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -358,8 +358,13 @@ static inline bool is_in_v2_mode(void)
  * @excluded_child: a child cpuset to be excluded in task checking
  * Return: true if there are tasks, false otherwise
  *
- * It is assumed that @cs is a valid partition root. @excluded_child should
- * be non-NULL when this cpuset is going to become a partition itself.
+ * @cs should be a valid partition root or going to become a partition root.
+ * @excluded_child should be non-NULL when this cpuset is going to become a
+ * partition itself.
+ *
+ * Note that a remote partition is not allowed underneath a valid local
+ * or remote partition. So if a non-partition root child is populated,
+ * the whole partition is considered populated.
  */
 static inline bool partition_is_populated(struct cpuset *cs,
                                          struct cpuset *excluded_child)
@@ -369,8 +374,6 @@ static inline bool partition_is_populated(struct cpuset *cs,
 
        if (cs->css.cgroup->nr_populated_csets)
                return true;
-       if (!excluded_child && !cs->nr_subparts)
-               return cgroup_is_populated(cs->css.cgroup);
 
        rcu_read_lock();
        cpuset_for_each_child(child, css, cs) {
@@ -1302,7 +1305,6 @@ static void reset_partition_data(struct cpuset *cs)
 
        lockdep_assert_held(&callback_lock);
 
-       cs->nr_subparts = 0;
        if (cpumask_empty(cs->exclusive_cpus)) {
                cpumask_clear(cs->effective_xcpus);
                if (is_cpu_exclusive(cs))
@@ -1746,7 +1748,6 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
        int deleting;   /* Deleting cpus from parent's effective_cpus   */
        int old_prs, new_prs;
        int part_error = PERR_NONE;     /* Partition error? */
-       int subparts_delta = 0;
        int isolcpus_updated = 0;
        struct cpumask *xcpus = user_xcpus(cs);
        bool nocpu;
@@ -1771,10 +1772,9 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
                if (is_partition_valid(parent))
                        adding = cpumask_and(tmp->addmask,
                                             xcpus, parent->effective_xcpus);
-               if (old_prs > 0) {
+               if (old_prs > 0)
                        new_prs = -old_prs;
-                       subparts_delta--;
-               }
+
                goto write_error;
        }
 
@@ -1829,7 +1829,6 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
                WARN_ON_ONCE(!cpumask_subset(tmp->new_cpus, parent->effective_cpus));
 
                deleting = true;
-               subparts_delta++;
        } else if (cmd == partcmd_disable) {
                /*
                 * May need to add cpus back to parent's effective_cpus
@@ -1840,7 +1839,6 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
                if (is_partition_valid(cs)) {
                        cpumask_copy(tmp->addmask, cs->effective_xcpus);
                        adding = true;
-                       subparts_delta--;
                }
                new_prs = PRS_MEMBER;
        } else if (newmask) {
@@ -1963,17 +1961,13 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
                switch (cs->partition_root_state) {
                case PRS_ROOT:
                case PRS_ISOLATED:
-                       if (part_error) {
+                       if (part_error)
                                new_prs = -old_prs;
-                               subparts_delta--;
-                       }
                        break;
                case PRS_INVALID_ROOT:
                case PRS_INVALID_ISOLATED:
-                       if (!part_error) {
+                       if (!part_error)
                                new_prs = -old_prs;
-                               subparts_delta++;
-                       }
                        break;
                }
        }
@@ -2002,11 +1996,9 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
         * newly deleted ones will be added back to effective_cpus.
         */
        spin_lock_irq(&callback_lock);
-       if (old_prs != new_prs) {
+       if (old_prs != new_prs)
                cs->partition_root_state = new_prs;
-               if (new_prs <= 0)
-                       cs->nr_subparts = 0;
-       }
+
        /*
         * Adding to parent's effective_cpus means deletion CPUs from cs
         * and vice versa.
@@ -2018,10 +2010,6 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
                isolcpus_updated += partition_xcpus_add(new_prs, parent,
                                                        tmp->delmask);
 
-       if (is_partition_valid(parent)) {
-               parent->nr_subparts += subparts_delta;
-               WARN_ON_ONCE(parent->nr_subparts < 0);
-       }
        spin_unlock_irq(&callback_lock);
        update_unbound_workqueue_cpumask(isolcpus_updated);
 
@@ -2105,8 +2093,6 @@ static void compute_partition_effective_cpumask(struct cpuset *cs,
                         */
                        spin_lock_irq(&callback_lock);
                        make_partition_invalid(child);
-                       cs->nr_subparts--;
-                       child->nr_subparts = 0;
                        spin_unlock_irq(&callback_lock);
                        notify_partition_change(child, old_prs);
                        continue;
@@ -4021,7 +4007,6 @@ static void cpuset_handle_hotplug(void)
                 */
                if (!cpumask_empty(subpartitions_cpus)) {
                        if (cpumask_subset(&new_cpus, subpartitions_cpus)) {
-                               top_cpuset.nr_subparts = 0;
                                cpumask_clear(subpartitions_cpus);
                        } else {
                                cpumask_andnot(&new_cpus, &new_cpus,