diff --git a/mm/compaction.c b/mm/compaction.c
index 9eef558..694eaab 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -713,7 +713,15 @@
 
 		/* 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;