1 files changed, 49 insertions, 31 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b8dc8e4..0f1d921 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3321,52 +3321,53 @@ void mem_cgroup_destroy_cache(struct kmem_cache *cachep)
 	schedule_work(&cachep->memcg_params->destroy);
 }
 
-static char *memcg_cache_name(struct mem_cgroup *memcg, struct kmem_cache *s)
-{
-	char *name;
-	struct dentry *dentry;
-
-	rcu_read_lock();
-	dentry = rcu_dereference(memcg->css.cgroup->dentry);
-	rcu_read_unlock();
-
-	BUG_ON(dentry == NULL);
-
-	name = kasprintf(GFP_KERNEL, "%s(%d:%s)", s->name,
-			 memcg_cache_id(memcg), dentry->d_name.name);
-
-	return name;
-}
+/*
+ * This lock protects updaters, not readers. We want readers to be as fast as
+ * they can, and they will either see NULL or a valid cache value. Our model
+ * allow them to see NULL, in which case the root memcg will be selected.
+ *
+ * We need this lock because multiple allocations to the same cache from a non
+ * will span more than one worker. Only one of them can create the cache.
+ */
+static DEFINE_MUTEX(memcg_cache_mutex);
 
+/*
+ * Called with memcg_cache_mutex held
+ */
 static struct kmem_cache *kmem_cache_dup(struct mem_cgroup *memcg,
 					 struct kmem_cache *s)
 {
-	char *name;
 	struct kmem_cache *new;
+	static char *tmp_name = NULL;
 
-	name = memcg_cache_name(memcg, s);
-	if (!name)
-		return NULL;
+	lockdep_assert_held(&memcg_cache_mutex);
+
+	/*
+	 * kmem_cache_create_memcg duplicates the given name and
+	 * cgroup_name for this name requires RCU context.
+	 * This static temporary buffer is used to prevent from
+	 * pointless shortliving allocation.
+	 */
+	if (!tmp_name) {
+		tmp_name = kmalloc(PATH_MAX, GFP_KERNEL);
+		if (!tmp_name)
+			return NULL;
+	}
+
+	rcu_read_lock();
+	snprintf(tmp_name, PATH_MAX, "%s(%d:%s)", s->name,
+			 memcg_cache_id(memcg), cgroup_name(memcg->css.cgroup));
+	rcu_read_unlock();
 
-	new = kmem_cache_create_memcg(memcg, name, s->object_size, s->align,
+	new = kmem_cache_create_memcg(memcg, tmp_name, s->object_size, s->align,
 				      (s->flags & ~SLAB_PANIC), s->ctor, s);
 
 	if (new)
 		new->allocflags |= __GFP_KMEMCG;
 
-	kfree(name);
 	return new;
 }
 
-/*
- * This lock protects updaters, not readers. We want readers to be as fast as
- * they can, and they will either see NULL or a valid cache value. Our model
- * allow them to see NULL, in which case the root memcg will be selected.
- *
- * We need this lock because multiple allocations to the same cache from a non
- * will span more than one worker. Only one of them can create the cache.
- */
-static DEFINE_MUTEX(memcg_cache_mutex);
 static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
 						  struct kmem_cache *cachep)
 {
@@ -5912,6 +5913,7 @@ static struct cftype mem_cgroup_files[] = {
 	},
 	{
 		.name = "use_hierarchy",
+		.flags = CFTYPE_INSANE,
 		.write_u64 = mem_cgroup_hierarchy_write,
 		.read_u64 = mem_cgroup_hierarchy_read,
 	},
@@ -6907,6 +6909,21 @@ static void mem_cgroup_move_task(struct cgroup *cont,
 }
 #endif
 
+/*
+ * Cgroup retains root cgroups across [un]mount cycles making it necessary
+ * to verify sane_behavior flag on each mount attempt.
+ */
+static void mem_cgroup_bind(struct cgroup *root)
+{
+	/*
+	 * use_hierarchy is forced with sane_behavior.  cgroup core
+	 * guarantees that @root doesn't have any children, so turning it
+	 * on for the root memcg is enough.
+	 */
+	if (cgroup_sane_behavior(root))
+		mem_cgroup_from_cont(root)->use_hierarchy = true;
+}
+
 struct cgroup_subsys mem_cgroup_subsys = {
 	.name = "memory",
 	.subsys_id = mem_cgroup_subsys_id,
@@ -6917,6 +6934,7 @@ struct cgroup_subsys mem_cgroup_subsys = {
 	.can_attach = mem_cgroup_can_attach,
 	.cancel_attach = mem_cgroup_cancel_attach,
 	.attach = mem_cgroup_move_task,
+	.bind = mem_cgroup_bind,
 	.base_cftypes = mem_cgroup_files,
 	.early_init = 0,
 	.use_id = 1,