diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 946a9a48..c79b692 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -261,7 +261,6 @@ static void obj_cgroup_uncharge_pages(struct obj_cgroup *objcg,
 static void obj_cgroup_release(struct percpu_ref *ref)
 {
 	struct obj_cgroup *objcg = container_of(ref, struct obj_cgroup, refcnt);
-	struct mem_cgroup *memcg;
 	unsigned int nr_bytes;
 	unsigned int nr_pages;
 	unsigned long flags;
@@ -291,11 +290,9 @@ static void obj_cgroup_release(struct percpu_ref *ref)
 	nr_pages = nr_bytes >> PAGE_SHIFT;
 
 	spin_lock_irqsave(&css_set_lock, flags);
-	memcg = obj_cgroup_memcg(objcg);
 	if (nr_pages)
 		obj_cgroup_uncharge_pages(objcg, nr_pages);
 	list_del(&objcg->list);
-	mem_cgroup_put(memcg);
 	spin_unlock_irqrestore(&css_set_lock, flags);
 
 	percpu_ref_exit(ref);
@@ -330,17 +327,12 @@ static void memcg_reparent_objcgs(struct mem_cgroup *memcg,
 
 	spin_lock_irq(&css_set_lock);
 
-	/* Move active objcg to the parent's list */
-	xchg(&objcg->memcg, parent);
-	css_get(&parent->css);
-	list_add(&objcg->list, &parent->objcg_list);
-
-	/* Move already reparented objcgs to the parent's list */
-	list_for_each_entry(iter, &memcg->objcg_list, list) {
-		css_get(&parent->css);
-		xchg(&iter->memcg, parent);
-		css_put(&memcg->css);
-	}
+	/* 1) Ready to reparent active objcg. */
+	list_add(&objcg->list, &memcg->objcg_list);
+	/* 2) Reparent active objcg and already reparented objcgs to parent. */
+	list_for_each_entry(iter, &memcg->objcg_list, list)
+		WRITE_ONCE(iter->memcg, parent);
+	/* 3) Move already reparented objcgs to the parent's list */
 	list_splice(&memcg->objcg_list, &parent->objcg_list);
 
 	spin_unlock_irq(&css_set_lock);