From a457b842b6f4b183f813f1eb26eab8fc96fed517 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd@google.com>
Date: Sat, 2 Oct 2010 17:46:06 -0700
Subject: [PATCH] --- yaml --- r: 211225 b: refs/heads/master c:
 4829b906cc063cb7cd1b7f34fa05de6db75ec8bb h: refs/heads/master i:   211223:
 03a6952c2ad3b551bd1174f7dc58c8a5419cec1f v: v3

---
 [refs]          | 2 +-
 trunk/mm/rmap.c | 8 +++++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/[refs] b/[refs]
index ddb471e07364..f407396d4f2f 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: c6ea21e35bf3691cad59647c771e6606067f627d
+refs/heads/master: 4829b906cc063cb7cd1b7f34fa05de6db75ec8bb
diff --git a/trunk/mm/rmap.c b/trunk/mm/rmap.c
index 9d2ba01bd4f9..92e6757f196e 100644
--- a/trunk/mm/rmap.c
+++ b/trunk/mm/rmap.c
@@ -381,7 +381,13 @@ vma_address(struct page *page, struct vm_area_struct *vma)
 unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
 {
 	if (PageAnon(page)) {
-		if (vma->anon_vma->root != page_anon_vma(page)->root)
+		struct anon_vma *page__anon_vma = page_anon_vma(page);
+		/*
+		 * Note: swapoff's unuse_vma() is more efficient with this
+		 * check, and needs it to match anon_vma when KSM is active.
+		 */
+		if (!vma->anon_vma || !page__anon_vma ||
+		    vma->anon_vma->root != page__anon_vma->root)
 			return -EFAULT;
 	} else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
 		if (!vma->vm_file ||