From 3b10ba30ba48798c995e1c487e9f77d719260049 Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Mon, 26 Oct 2009 16:50:00 -0700
Subject: [PATCH] --- yaml --- r: 167750 b: refs/heads/master c:
 6a7b95481d49f73991d3dbf8c1e696a24684ac05 h: refs/heads/master v: v3

---
 [refs]            |  2 +-
 trunk/mm/vmscan.c | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index d24369adaaec..46e2fd75c67e 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: b05ca7385a2848abdc72051f832722641daed8b0
+refs/heads/master: 6a7b95481d49f73991d3dbf8c1e696a24684ac05
diff --git a/trunk/mm/vmscan.c b/trunk/mm/vmscan.c
index fbcac3bdcf19..777af57fd8c8 100644
--- a/trunk/mm/vmscan.c
+++ b/trunk/mm/vmscan.c
@@ -544,6 +544,16 @@ void putback_lru_page(struct page *page)
 		 */
 		lru = LRU_UNEVICTABLE;
 		add_page_to_unevictable_list(page);
+		/*
+		 * When racing with an mlock clearing (page is
+		 * unlocked), make sure that if the other thread does
+		 * not observe our setting of PG_lru and fails
+		 * isolation, we see PG_mlocked cleared below and move
+		 * the page back to the evictable list.
+		 *
+		 * The other side is TestClearPageMlocked().
+		 */
+		smp_mb();
 	}
 
 	/*