Merge branch 'for-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:
 "Two cpuset behavior changes:

   - cpuset on cgroup2 is changed to enable memory migration based on
     nodemask by default.

   - A notification is generated when cpuset partition state changes.

  All other patches are minor fixes and cleanups"

* 'for-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: Avoid compiler warnings with no subsystems
  cgroup/cpuset: Avoid memory migration when nodemasks match
  cgroup/cpuset: Enable memory migration for cpuset v2
  cgroup/cpuset: Enable event notification when partition state changes
  cgroup: cgroup-v1: clean up kernel-doc notation
  cgroup: Replace deprecated CPU-hotplug functions.
  cgroup/cpuset: Fix violation of cpuset locking rule
  cgroup/cpuset: Fix a partition bug with hotplug
  cgroup/cpuset: Miscellaneous code cleanup
  cgroup: remove cgroup_mount from comments

1 files changed, 106 insertions, 56 deletions

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 6500cbe0ce16..df1ccf4558f8 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -160,6 +160,9 @@ struct cpuset {
 	 */
 	int use_parent_ecpus;
 	int child_ecpus_count;
+
+	/* Handle for cpuset.cpus.partition */
+	struct cgroup_file partition_file;
 };
 
 /*
@@ -263,6 +266,16 @@ static inline int is_partition_root(const struct cpuset *cs)
 	return cs->partition_root_state > 0;
 }
 
+/*
+ * Send notification event of whenever partition_root_state changes.
+ */
+static inline void notify_partition_change(struct cpuset *cs,
+					   int old_prs, int new_prs)
+{
+	if (old_prs != new_prs)
+		cgroup_file_notify(&cs->partition_file);
+}
+
 static struct cpuset top_cpuset = {
 	.flags = ((1 << CS_ONLINE) | (1 << CS_CPU_EXCLUSIVE) |
 		  (1 << CS_MEM_EXCLUSIVE)),
@@ -992,7 +1005,7 @@ partition_and_rebuild_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
  * 'cpus' is removed, then call this routine to rebuild the
  * scheduler's dynamic sched domains.
  *
- * Call with cpuset_mutex held.  Takes get_online_cpus().
+ * Call with cpuset_mutex held.  Takes cpus_read_lock().
  */
 static void rebuild_sched_domains_locked(void)
 {
@@ -1053,11 +1066,11 @@ static void rebuild_sched_domains_locked(void)
 
 void rebuild_sched_domains(void)
 {
-	get_online_cpus();
+	cpus_read_lock();
 	percpu_down_write(&cpuset_rwsem);
 	rebuild_sched_domains_locked();
 	percpu_up_write(&cpuset_rwsem);
-	put_online_cpus();
+	cpus_read_unlock();
 }
 
 /**
@@ -1127,7 +1140,7 @@ enum subparts_cmd {
  * cpus_allowed can be granted or an error code will be returned.
  *
  * For partcmd_disable, the cpuset is being transofrmed from a partition
- * root back to a non-partition root. any CPUs in cpus_allowed that are in
+ * root back to a non-partition root. Any CPUs in cpus_allowed that are in
  * parent's subparts_cpus will be taken away from that cpumask and put back
  * into parent's effective_cpus. 0 should always be returned.
  *
@@ -1161,6 +1174,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
 	struct cpuset *parent = parent_cs(cpuset);
 	int adding;	/* Moving cpus from effective_cpus to subparts_cpus */
 	int deleting;	/* Moving cpus from subparts_cpus to effective_cpus */
+	int old_prs, new_prs;
 	bool part_error = false;	/* Partition error? */
 
 	percpu_rwsem_assert_held(&cpuset_rwsem);
@@ -1196,6 +1210,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
 	 * A cpumask update cannot make parent's effective_cpus become empty.
 	 */
 	adding = deleting = false;
+	old_prs = new_prs = cpuset->partition_root_state;
 	if (cmd == partcmd_enable) {
 		cpumask_copy(tmp->addmask, cpuset->cpus_allowed);
 		adding = true;
@@ -1238,7 +1253,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
 		/*
 		 * partcmd_update w/o newmask:
 		 *
-		 * addmask = cpus_allowed & parent->effectiveb_cpus
+		 * addmask = cpus_allowed & parent->effective_cpus
 		 *
 		 * Note that parent's subparts_cpus may have been
 		 * pre-shrunk in case there is a change in the cpu list.
@@ -1260,11 +1275,11 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
 		switch (cpuset->partition_root_state) {
 		case PRS_ENABLED:
 			if (part_error)
-				cpuset->partition_root_state = PRS_ERROR;
+				new_prs = PRS_ERROR;
 			break;
 		case PRS_ERROR:
 			if (!part_error)
-				cpuset->partition_root_state = PRS_ENABLED;
+				new_prs = PRS_ENABLED;
 			break;
 		}
 		/*
@@ -1273,10 +1288,10 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
 		part_error = (prev_prs == PRS_ERROR);
 	}
 
-	if (!part_error && (cpuset->partition_root_state == PRS_ERROR))
+	if (!part_error && (new_prs == PRS_ERROR))
 		return 0;	/* Nothing need to be done */
 
-	if (cpuset->partition_root_state == PRS_ERROR) {
+	if (new_prs == PRS_ERROR) {
 		/*
 		 * Remove all its cpus from parent's subparts_cpus.
 		 */
@@ -1285,7 +1300,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
 				       parent->subparts_cpus);
 	}
 
-	if (!adding && !deleting)
+	if (!adding && !deleting && (new_prs == old_prs))
 		return 0;
 
 	/*
@@ -1312,7 +1327,12 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
 	}
 
 	parent->nr_subparts_cpus = cpumask_weight(parent->subparts_cpus);
+
+	if (old_prs != new_prs)
+		cpuset->partition_root_state = new_prs;
+
 	spin_unlock_irq(&callback_lock);
+	notify_partition_change(cpuset, old_prs, new_prs);
 
 	return cmd == partcmd_update;
 }
@@ -1334,6 +1354,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
 	struct cpuset *cp;
 	struct cgroup_subsys_state *pos_css;
 	bool need_rebuild_sched_domains = false;
+	int old_prs, new_prs;
 
 	rcu_read_lock();
 	cpuset_for_each_descendant_pre(cp, pos_css, cs) {
@@ -1373,17 +1394,18 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
 		 * update_tasks_cpumask() again for tasks in the parent
 		 * cpuset if the parent's subparts_cpus changes.
 		 */
-		if ((cp != cs) && cp->partition_root_state) {
+		old_prs = new_prs = cp->partition_root_state;
+		if ((cp != cs) && old_prs) {
 			switch (parent->partition_root_state) {
 			case PRS_DISABLED:
 				/*
 				 * If parent is not a partition root or an
-				 * invalid partition root, clear the state
-				 * state and the CS_CPU_EXCLUSIVE flag.
+				 * invalid partition root, clear its state
+				 * and its CS_CPU_EXCLUSIVE flag.
 				 */
 				WARN_ON_ONCE(cp->partition_root_state
 					     != PRS_ERROR);
-				cp->partition_root_state = 0;
+				new_prs = PRS_DISABLED;
 
 				/*
 				 * clear_bit() is an atomic operation and
@@ -1404,11 +1426,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
 				/*
 				 * When parent is invalid, it has to be too.
 				 */
-				cp->partition_root_state = PRS_ERROR;
-				if (cp->nr_subparts_cpus) {
-					cp->nr_subparts_cpus = 0;
-					cpumask_clear(cp->subparts_cpus);
-				}
+				new_prs = PRS_ERROR;
 				break;
 			}
 		}
@@ -1420,8 +1438,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
 		spin_lock_irq(&callback_lock);
 
 		cpumask_copy(cp->effective_cpus, tmp->new_cpus);
-		if (cp->nr_subparts_cpus &&
-		   (cp->partition_root_state != PRS_ENABLED)) {
+		if (cp->nr_subparts_cpus && (new_prs != PRS_ENABLED)) {
 			cp->nr_subparts_cpus = 0;
 			cpumask_clear(cp->subparts_cpus);
 		} else if (cp->nr_subparts_cpus) {
@@ -1448,7 +1465,12 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
 					= cpumask_weight(cp->subparts_cpus);
 			}
 		}
+
+		if (new_prs != old_prs)
+			cp->partition_root_state = new_prs;
+
 		spin_unlock_irq(&callback_lock);
+		notify_partition_change(cp, old_prs, new_prs);
 
 		WARN_ON(!is_in_v2_mode() &&
 			!cpumask_equal(cp->cpus_allowed, cp->effective_cpus));
@@ -1625,6 +1647,11 @@ static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
 {
 	struct cpuset_migrate_mm_work *mwork;
 
+	if (nodes_equal(*from, *to)) {
+		mmput(mm);
+		return;
+	}
+
 	mwork = kzalloc(sizeof(*mwork), GFP_KERNEL);
 	if (mwork) {
 		mwork->mm = mm;
@@ -1950,34 +1977,32 @@ out:
 
 /*
  * update_prstate - update partititon_root_state
- * cs:	the cpuset to update
- * val: 0 - disabled, 1 - enabled
+ * cs: the cpuset to update
+ * new_prs: new partition root state
  *
  * Call with cpuset_mutex held.
  */
-static int update_prstate(struct cpuset *cs, int val)
+static int update_prstate(struct cpuset *cs, int new_prs)
 {
-	int err;
+	int err, old_prs = cs->partition_root_state;
 	struct cpuset *parent = parent_cs(cs);
-	struct tmpmasks tmp;
+	struct tmpmasks tmpmask;
 
-	if ((val != 0) && (val != 1))
-		return -EINVAL;
-	if (val == cs->partition_root_state)
+	if (old_prs == new_prs)
 		return 0;
 
 	/*
 	 * Cannot force a partial or invalid partition root to a full
 	 * partition root.
 	 */
-	if (val && cs->partition_root_state)
+	if (new_prs && (old_prs == PRS_ERROR))
 		return -EINVAL;
 
-	if (alloc_cpumasks(NULL, &tmp))
+	if (alloc_cpumasks(NULL, &tmpmask))
 		return -ENOMEM;
 
 	err = -EINVAL;
-	if (!cs->partition_root_state) {
+	if (!old_prs) {
 		/*
 		 * Turning on partition root requires setting the
 		 * CS_CPU_EXCLUSIVE bit implicitly as well and cpus_allowed
@@ -1991,31 +2016,27 @@ static int update_prstate(struct cpuset *cs, int val)
 			goto out;
 
 		err = update_parent_subparts_cpumask(cs, partcmd_enable,
-						     NULL, &tmp);
+						     NULL, &tmpmask);
 		if (err) {
 			update_flag(CS_CPU_EXCLUSIVE, cs, 0);
 			goto out;
 		}
-		cs->partition_root_state = PRS_ENABLED;
 	} else {
 		/*
 		 * Turning off partition root will clear the
 		 * CS_CPU_EXCLUSIVE bit.
 		 */
-		if (cs->partition_root_state == PRS_ERROR) {
-			cs->partition_root_state = 0;
+		if (old_prs == PRS_ERROR) {
 			update_flag(CS_CPU_EXCLUSIVE, cs, 0);
 			err = 0;
 			goto out;
 		}
 
 		err = update_parent_subparts_cpumask(cs, partcmd_disable,
-						     NULL, &tmp);
+						     NULL, &tmpmask);
 		if (err)
 			goto out;
 
-		cs->partition_root_state = 0;
-
 		/* Turning off CS_CPU_EXCLUSIVE will not return error */
 		update_flag(CS_CPU_EXCLUSIVE, cs, 0);
 	}
@@ -2028,11 +2049,18 @@ static int update_prstate(struct cpuset *cs, int val)
 		update_tasks_cpumask(parent);
 
 	if (parent->child_ecpus_count)
-		update_sibling_cpumasks(parent, cs, &tmp);
+		update_sibling_cpumasks(parent, cs, &tmpmask);
 
 	rebuild_sched_domains_locked();
 out:
-	free_cpumasks(NULL, &tmp);
+	if (!err) {
+		spin_lock_irq(&callback_lock);
+		cs->partition_root_state = new_prs;
+		spin_unlock_irq(&callback_lock);
+		notify_partition_change(cs, old_prs, new_prs);
+	}
+
+	free_cpumasks(NULL, &tmpmask);
 	return err;
 }
 
@@ -2293,7 +2321,7 @@ static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
 	cpuset_filetype_t type = cft->private;
 	int retval = 0;
 
-	get_online_cpus();
+	cpus_read_lock();
 	percpu_down_write(&cpuset_rwsem);
 	if (!is_cpuset_online(cs)) {
 		retval = -ENODEV;
@@ -2331,7 +2359,7 @@ static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
 	}
 out_unlock:
 	percpu_up_write(&cpuset_rwsem);
-	put_online_cpus();
+	cpus_read_unlock();
 	return retval;
 }
 
@@ -2342,7 +2370,7 @@ static int cpuset_write_s64(struct cgroup_subsys_state *css, struct cftype *cft,
 	cpuset_filetype_t type = cft->private;
 	int retval = -ENODEV;
 
-	get_online_cpus();
+	cpus_read_lock();
 	percpu_down_write(&cpuset_rwsem);
 	if (!is_cpuset_online(cs))
 		goto out_unlock;
@@ -2357,7 +2385,7 @@ static int cpuset_write_s64(struct cgroup_subsys_state *css, struct cftype *cft,
 	}
 out_unlock:
 	percpu_up_write(&cpuset_rwsem);
-	put_online_cpus();
+	cpus_read_unlock();
 	return retval;
 }
 
@@ -2396,7 +2424,7 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
 	kernfs_break_active_protection(of->kn);
 	flush_work(&cpuset_hotplug_work);
 
-	get_online_cpus();
+	cpus_read_lock();
 	percpu_down_write(&cpuset_rwsem);
 	if (!is_cpuset_online(cs))
 		goto out_unlock;
@@ -2422,7 +2450,7 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
 	free_cpuset(trialcs);
 out_unlock:
 	percpu_up_write(&cpuset_rwsem);
-	put_online_cpus();
+	cpus_read_unlock();
 	kernfs_unbreak_active_protection(of->kn);
 	css_put(&cs->css);
 	flush_workqueue(cpuset_migrate_mm_wq);
@@ -2553,7 +2581,7 @@ static ssize_t sched_partition_write(struct kernfs_open_file *of, char *buf,
 		return -EINVAL;
 
 	css_get(&cs->css);
-	get_online_cpus();
+	cpus_read_lock();
 	percpu_down_write(&cpuset_rwsem);
 	if (!is_cpuset_online(cs))
 		goto out_unlock;
@@ -2561,7 +2589,7 @@ static ssize_t sched_partition_write(struct kernfs_open_file *of, char *buf,
 	retval = update_prstate(cs, val);
 out_unlock:
 	percpu_up_write(&cpuset_rwsem);
-	put_online_cpus();
+	cpus_read_unlock();
 	css_put(&cs->css);
 	return retval ?: nbytes;
 }
@@ -2713,6 +2741,7 @@ static struct cftype dfl_files[] = {
 		.write = sched_partition_write,
 		.private = FILE_PARTITION_ROOT,
 		.flags = CFTYPE_NOT_ON_ROOT,
+		.file_offset = offsetof(struct cpuset, partition_file),
 	},
 
 	{
@@ -2748,12 +2777,16 @@ cpuset_css_alloc(struct cgroup_subsys_state *parent_css)
 		return ERR_PTR(-ENOMEM);
 	}
 
-	set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
+	__set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
 	nodes_clear(cs->mems_allowed);
 	nodes_clear(cs->effective_mems);
 	fmeter_init(&cs->fmeter);
 	cs->relax_domain_level = -1;
 
+	/* Set CS_MEMORY_MIGRATE for default hierarchy */
+	if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys))
+		__set_bit(CS_MEMORY_MIGRATE, &cs->flags);
+
 	return &cs->css;
 }
 
@@ -2767,7 +2800,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
 	if (!parent)
 		return 0;
 
-	get_online_cpus();
+	cpus_read_lock();
 	percpu_down_write(&cpuset_rwsem);
 
 	set_bit(CS_ONLINE, &cs->flags);
@@ -2820,7 +2853,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
 	spin_unlock_irq(&callback_lock);
 out_unlock:
 	percpu_up_write(&cpuset_rwsem);
-	put_online_cpus();
+	cpus_read_unlock();
 	return 0;
 }
 
@@ -2839,7 +2872,7 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css)
 {
 	struct cpuset *cs = css_cs(css);
 
-	get_online_cpus();
+	cpus_read_lock();
 	percpu_down_write(&cpuset_rwsem);
 
 	if (is_partition_root(cs))
@@ -2860,7 +2893,7 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css)
 	clear_bit(CS_ONLINE, &cs->flags);
 
 	percpu_up_write(&cpuset_rwsem);
-	put_online_cpus();
+	cpus_read_unlock();
 }
 
 static void cpuset_css_free(struct cgroup_subsys_state *css)
@@ -3071,7 +3104,7 @@ retry:
 		goto retry;
 	}
 
-	parent =  parent_cs(cs);
+	parent = parent_cs(cs);
 	compute_effective_cpumask(&new_cpus, cs, parent);
 	nodes_and(new_mems, cs->mems_allowed, parent->effective_mems);
 
@@ -3093,8 +3126,10 @@ retry:
 	if (is_partition_root(cs) && (cpumask_empty(&new_cpus) ||
 	   (parent->partition_root_state == PRS_ERROR))) {
 		if (cs->nr_subparts_cpus) {
+			spin_lock_irq(&callback_lock);
 			cs->nr_subparts_cpus = 0;
 			cpumask_clear(cs->subparts_cpus);
+			spin_unlock_irq(&callback_lock);
 			compute_effective_cpumask(&new_cpus, cs, parent);
 		}
 
@@ -3106,9 +3141,17 @@ retry:
 		 */
 		if ((parent->partition_root_state == PRS_ERROR) ||
 		     cpumask_empty(&new_cpus)) {
+			int old_prs;
+
 			update_parent_subparts_cpumask(cs, partcmd_disable,
 						       NULL, tmp);
-			cs->partition_root_state = PRS_ERROR;
+			old_prs = cs->partition_root_state;
+			if (old_prs != PRS_ERROR) {
+				spin_lock_irq(&callback_lock);
+				cs->partition_root_state = PRS_ERROR;
+				spin_unlock_irq(&callback_lock);
+				notify_partition_change(cs, old_prs, PRS_ERROR);
+			}
 		}
 		cpuset_force_rebuild();
 	}
@@ -3179,6 +3222,13 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
 	cpus_updated = !cpumask_equal(top_cpuset.effective_cpus, &new_cpus);
 	mems_updated = !nodes_equal(top_cpuset.effective_mems, new_mems);
 
+	/*
+	 * In the rare case that hotplug removes all the cpus in subparts_cpus,
+	 * we assumed that cpus are updated.
+	 */
+	if (!cpus_updated && top_cpuset.nr_subparts_cpus)
+		cpus_updated = true;
+
 	/* synchronize cpus_allowed to cpu_active_mask */
 	if (cpus_updated) {
 		spin_lock_irq(&callback_lock);