diff --git a/mm/mmap.c b/mm/mmap.c
index f940062..9ed3a06 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1488,7 +1488,11 @@
 		 *
 		 * Answer: Yes, several device drivers can do it in their
 		 *         f_op->mmap method. -DaveM
+		 * Bug: If addr is changed, prev, rb_link, rb_parent should
+		 *      be updated for vma_link()
 		 */
+		WARN_ON_ONCE(addr != vma->vm_start);
+
 		addr = vma->vm_start;
 		pgoff = vma->vm_pgoff;
 		vm_flags = vma->vm_flags;