diff --git a/[refs] b/[refs]
index 5d59abcc0be5..073291ed4b9f 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 3f96b79ad96263cc0ece7bb340cddf9b2ddfb1b3
+refs/heads/master: 252c5f94d944487e9f50ece7942b0fbf659c5c31
diff --git a/trunk/mm/mmap.c b/trunk/mm/mmap.c
index 56eb871c32d0..b6d74b3dbbc2 100644
--- a/trunk/mm/mmap.c
+++ b/trunk/mm/mmap.c
@@ -570,9 +570,9 @@ again:			remove_next = 1 + (end > next->vm_end);
 
 	/*
 	 * When changing only vma->vm_end, we don't really need
-	 * anon_vma lock: but is that case worth optimizing out?
+	 * anon_vma lock.
 	 */
-	if (vma->anon_vma)
+	if (vma->anon_vma && (insert || importer || start != vma->vm_start))
 		anon_vma = vma->anon_vma;
 	if (anon_vma) {
 		spin_lock(&anon_vma->lock);