Merge tag 'cgroup-for-6.17-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup fixes from Tejun Heo:

 - Fix NULL de-ref in css_rstat_exit() which could happen after
   allocation failure

 - Fix a cpuset partition handling bug and a couple other misc issues

 - Doc spelling fix

* tag 'cgroup-for-6.17-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  docs: cgroup: fixed spelling mistakes in documentation
  cgroup: avoid null de-ref in css_rstat_exit()
  cgroup/cpuset: Remove the unnecessary css_get/put() in cpuset_partition_write()
  cgroup/cpuset: Fix a partition error with CPU hotplug
  cgroup/cpuset: Use static_branch_enable_cpuslocked() on cpusets_insane_config_key

Author: torvalds

Documentation/admin-guide/cgroup-v2.rst

@@ -435,8 +435,8 @@ both cgroups.
 Controlling Controllers
 -----------------------
 
-Availablity
-~~~~~~~~~~~
+Availability
+~~~~~~~~~~~~
 
 A controller is available in a cgroup when it is supported by the kernel (i.e.,
 compiled in, not disabled and not attached to a v1 hierarchy) and listed in the

kernel/cgroup/cpuset.c

@@ -280,7 +280,7 @@ static inline void check_insane_mems_config(nodemask_t *nodes)
 {
 	if (!cpusets_insane_config() &&
 		movable_only_nodes(nodes)) {
-		static_branch_enable(&cpusets_insane_config_key);
+		static_branch_enable_cpuslocked(&cpusets_insane_config_key);
 		pr_info("Unsupported (movable nodes only) cpuset configuration detected (nmask=%*pbl)!\n"
 			"Cpuset allocations might fail even with a lot of memory available.\n",
 			nodemask_pr_args(nodes));
@@ -1843,7 +1843,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
 			if (is_partition_valid(cs))
 				adding = cpumask_and(tmp->addmask,
 						xcpus, parent->effective_xcpus);
-		} else if (is_partition_invalid(cs) &&
+		} else if (is_partition_invalid(cs) && !cpumask_empty(xcpus) &&
 			   cpumask_subset(xcpus, parent->effective_xcpus)) {
 			struct cgroup_subsys_state *css;
 			struct cpuset *child;
@@ -3358,14 +3358,12 @@ static ssize_t cpuset_partition_write(struct kernfs_open_file *of, char *buf,
 	else
 		return -EINVAL;
 
-	css_get(&cs->css);
 	cpus_read_lock();
 	mutex_lock(&cpuset_mutex);
 	if (is_cpuset_online(cs))
 		retval = update_prstate(cs, val);
 	mutex_unlock(&cpuset_mutex);
 	cpus_read_unlock();
-	css_put(&cs->css);
 	return retval ?: nbytes;
 }
 
@@ -3870,9 +3868,10 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
 		partcmd = partcmd_invalidate;
 	/*
 	 * On the other hand, an invalid partition root may be transitioned
-	 * back to a regular one.
+	 * back to a regular one with a non-empty effective xcpus.
 	 */
-	else if (is_partition_valid(parent) && is_partition_invalid(cs))
+	else if (is_partition_valid(parent) && is_partition_invalid(cs) &&
+		 !cpumask_empty(cs->effective_xcpus))
 		partcmd = partcmd_update;
 
 	if (partcmd >= 0) {

kernel/cgroup/rstat.c

@@ -479,6 +479,9 @@ void css_rstat_exit(struct cgroup_subsys_state *css)
 	if (!css_uses_rstat(css))
 		return;
 
+	if (!css->rstat_cpu)
+		return;
+
 	css_rstat_flush(css);
 
 	/* sanity check */