diff --git a/mm/ksm.c b/mm/ksm.c
index da6037c..9f2acc9 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -318,19 +318,14 @@
 			  struct anon_vma *anon_vma)
 {
 	rmap_item->anon_vma = anon_vma;
-	atomic_inc(&anon_vma->external_refcount);
+	get_anon_vma(anon_vma);
 }
 
-static void drop_anon_vma(struct rmap_item *rmap_item)
+static void ksm_drop_anon_vma(struct rmap_item *rmap_item)
 {
 	struct anon_vma *anon_vma = rmap_item->anon_vma;
 
-	if (atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->root->lock)) {
-		int empty = list_empty(&anon_vma->head);
-		anon_vma_unlock(anon_vma);
-		if (empty)
-			anon_vma_free(anon_vma);
-	}
+	drop_anon_vma(anon_vma);
 }
 
 /*
@@ -415,7 +410,7 @@
 	 * It is not an accident that whenever we want to break COW
 	 * to undo, we also need to drop a reference to the anon_vma.
 	 */
-	drop_anon_vma(rmap_item);
+	ksm_drop_anon_vma(rmap_item);
 
 	down_read(&mm->mmap_sem);
 	if (ksm_test_exit(mm))
@@ -470,7 +465,7 @@
 			ksm_pages_sharing--;
 		else
 			ksm_pages_shared--;
-		drop_anon_vma(rmap_item);
+		ksm_drop_anon_vma(rmap_item);
 		rmap_item->address &= PAGE_MASK;
 		cond_resched();
 	}
@@ -558,7 +553,7 @@
 		else
 			ksm_pages_shared--;
 
-		drop_anon_vma(rmap_item);
+		ksm_drop_anon_vma(rmap_item);
 		rmap_item->address &= PAGE_MASK;
 
 	} else if (rmap_item->address & UNSTABLE_FLAG) {