From fac1dfc5eb0c190d6ddddff00930e578f49941f0 Mon Sep 17 00:00:00 2001
From: Mel Gorman <mgorman@suse.de>
Date: Thu, 6 Dec 2012 19:01:14 +0000
Subject: [PATCH] --- yaml --- r: 336245 b: refs/heads/master c:
 60177d31d215bc2b4c5a7aa6f742800e04fa0a92 h: refs/heads/master i:   336243:
 da85f851492c18190dee20e0a69c1400a134e827 v: v3

---
 [refs]                |  2 +-
 trunk/mm/compaction.c | 10 +++++++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/[refs] b/[refs]
index 385a16cce79e..50751a2449be 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 04c5decdc0aecde43bf44860484f26ee0691335f
+refs/heads/master: 60177d31d215bc2b4c5a7aa6f742800e04fa0a92
diff --git a/trunk/mm/compaction.c b/trunk/mm/compaction.c
index 9eef55838fca..694eaabaaebd 100644
--- a/trunk/mm/compaction.c
+++ b/trunk/mm/compaction.c
@@ -713,7 +713,15 @@ static void isolate_freepages(struct zone *zone,
 
 		/* Found a block suitable for isolating free pages from */
 		isolated = 0;
-		end_pfn = min(pfn + pageblock_nr_pages, zone_end_pfn);
+
+		/*
+		 * As pfn may not start aligned, pfn+pageblock_nr_page
+		 * may cross a MAX_ORDER_NR_PAGES boundary and miss
+		 * a pfn_valid check. Ensure isolate_freepages_block()
+		 * only scans within a pageblock
+		 */
+		end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
+		end_pfn = min(end_pfn, zone_end_pfn);
 		isolated = isolate_freepages_block(cc, pfn, end_pfn,
 						   freelist, false);
 		nr_freepages += isolated;