1 files changed, 18 insertions, 7 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 322d18d..014a4f1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3270,9 +3270,6 @@ void memcg_register_cache(struct kmem_cache *s)
 
 	css_get(&memcg->css);
 
-	mutex_lock(&memcg->slab_caches_mutex);
-	list_add(&s->memcg_params->list, &memcg->memcg_slab_caches);
-	mutex_unlock(&memcg->slab_caches_mutex);
 
 	/*
 	 * Since readers won't lock (see cache_from_memcg_idx()), we need a
@@ -3281,7 +3278,16 @@ void memcg_register_cache(struct kmem_cache *s)
 	 */
 	smp_wmb();
 
+	/*
+	 * Initialize the pointer to this cache in its parent's memcg_params
+	 * before adding it to the memcg_slab_caches list, otherwise we can
+	 * fail to convert memcg_params_to_cache() while traversing the list.
+	 */
 	root->memcg_params->memcg_caches[id] = s;
+
+	mutex_lock(&memcg->slab_caches_mutex);
+	list_add(&s->memcg_params->list, &memcg->memcg_slab_caches);
+	mutex_unlock(&memcg->slab_caches_mutex);
 }
 
 void memcg_unregister_cache(struct kmem_cache *s)
@@ -3293,16 +3299,21 @@ void memcg_unregister_cache(struct kmem_cache *s)
 	if (is_root_cache(s))
 		return;
 
-	memcg = s->memcg_params->memcg;
-	id  = memcg_cache_id(memcg);
-
 	root = s->memcg_params->root_cache;
-	root->memcg_params->memcg_caches[id] = NULL;
+	memcg = s->memcg_params->memcg;
+	id = memcg_cache_id(memcg);
 
 	mutex_lock(&memcg->slab_caches_mutex);
 	list_del(&s->memcg_params->list);
 	mutex_unlock(&memcg->slab_caches_mutex);
 
+	/*
+	 * Clear the pointer to this cache in its parent's memcg_params only
+	 * after removing it from the memcg_slab_caches list, otherwise we can
+	 * fail to convert memcg_params_to_cache() while traversing the list.
+	 */
+	root->memcg_params->memcg_caches[id] = NULL;
+
 	css_put(&memcg->css);
 }