From 924867f41b634f953533b332a219062a5b5082cb Mon Sep 17 00:00:00 2001
From: Andrea Arcangeli <aarcange@redhat.com>
Date: Mon, 9 Aug 2010 17:19:10 -0700
Subject: [PATCH] --- yaml --- r: 207237 b: refs/heads/master c:
 44ab57a06ded284db6ccdefc6b76eddb1c34d7ed h: refs/heads/master i:   207235:
 d5e0458074a6400f08ee23c873199f06bfae88bf v: v3

---
 [refs]          | 2 +-
 trunk/mm/rmap.c | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 58fa3eab93f9..96f7cf3b9647 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 21d0d443cdc1658a8c1484fdcece4803f0f96d0e
+refs/heads/master: 44ab57a06ded284db6ccdefc6b76eddb1c34d7ed
diff --git a/trunk/mm/rmap.c b/trunk/mm/rmap.c
index 2f855babfd06..4d152a6d3a89 100644
--- a/trunk/mm/rmap.c
+++ b/trunk/mm/rmap.c
@@ -811,6 +811,7 @@ static void __page_check_anon_rmap(struct page *page,
 	 * are initially only visible via the pagetables, and the pte is locked
 	 * over the call to page_add_new_anon_rmap.
 	 */
+	BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
 	BUG_ON(page->index != linear_page_index(vma, address));
 #endif
 }
@@ -1408,6 +1409,7 @@ int try_to_munlock(struct page *page)
  */
 void drop_anon_vma(struct anon_vma *anon_vma)
 {
+	BUG_ON(atomic_read(&anon_vma->external_refcount) <= 0);
 	if (atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->root->lock)) {
 		struct anon_vma *root = anon_vma->root;
 		int empty = list_empty(&anon_vma->head);
@@ -1419,6 +1421,7 @@ void drop_anon_vma(struct anon_vma *anon_vma)
 		 * the refcount on the root and check if we need to free it.
 		 */
 		if (empty && anon_vma != root) {
+			BUG_ON(atomic_read(&root->external_refcount) <= 0);
 			last_root_user = atomic_dec_and_test(&root->external_refcount);
 			root_empty = list_empty(&root->head);
 		}