WIP potential fix from Mike Rapoport <rppt@linux.ibm.com>

mm/shuffle.c

@@ -58,7 +58,8 @@ module_param_call(shuffle, shuffle_store, shuffle_show, &shuffle_param, 0400);
  * For two pages to be swapped in the shuffle, they must be free (on a
  * 'free_area' lru), have the same order, and have the same migratetype.
  */
-static struct page * __meminit shuffle_valid_page(unsigned long pfn, int order)
+static struct page * __meminit shuffle_valid_page(unsigned long pfn, int order,
+						  struct zone *z)
 {
 	struct page *page;
 
@@ -80,6 +81,9 @@ static struct page * __meminit shuffle_valid_page(unsigned long pfn, int order)
 	if (!PageBuddy(page))
 		return NULL;
 
+	if (!memmap_valid_within(pfn, page, z))
+		return NULL;
+
 	/*
 	 * ...is the page on the same list as the page we will
 	 * shuffle it with?
@@ -123,7 +127,7 @@ void __meminit __shuffle_zone(struct zone *z)
 		 * page_j randomly selected in the span @zone_start_pfn to
 		 * @spanned_pages.
 		 */
-		page_i = shuffle_valid_page(i, order);
+		page_i = shuffle_valid_page(i, order, z);
 		if (!page_i)
 			continue;
 
@@ -137,7 +141,7 @@ void __meminit __shuffle_zone(struct zone *z)
 			j = z->zone_start_pfn +
 				ALIGN_DOWN(get_random_long() % z->spanned_pages,
 						order_pages);
-			page_j = shuffle_valid_page(j, order);
+			page_j = shuffle_valid_page(j, order, z);
 			if (page_j && page_j != page_i)
 				break;
 		}