1 files changed, 59 insertions, 36 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2ca3e9bd739c..b09ce5fe0cd2 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1008,6 +1008,52 @@ static void change_pageblock_range(struct page *pageblock_page,
 	}
 }
 
+/*
+ * If breaking a large block of pages, move all free pages to the preferred
+ * allocation list. If falling back for a reclaimable kernel allocation, be
+ * more aggressive about taking ownership of free pages.
+ *
+ * On the other hand, never change migration type of MIGRATE_CMA pageblocks
+ * nor move CMA pages to different free lists. We don't want unmovable pages
+ * to be allocated from MIGRATE_CMA areas.
+ *
+ * Returns the new migratetype of the pageblock (or the same old migratetype
+ * if it was unchanged).
+ */
+static int try_to_steal_freepages(struct zone *zone, struct page *page,
+				  int start_type, int fallback_type)
+{
+	int current_order = page_order(page);
+
+	if (is_migrate_cma(fallback_type))
+		return fallback_type;
+
+	/* Take ownership for orders >= pageblock_order */
+	if (current_order >= pageblock_order) {
+		change_pageblock_range(page, current_order, start_type);
+		return start_type;
+	}
+
+	if (current_order >= pageblock_order / 2 ||
+	    start_type == MIGRATE_RECLAIMABLE ||
+	    page_group_by_mobility_disabled) {
+		int pages;
+
+		pages = move_freepages_block(zone, page, start_type);
+
+		/* Claim the whole block if over half of it is free */
+		if (pages >= (1 << (pageblock_order-1)) ||
+				page_group_by_mobility_disabled) {
+
+			set_pageblock_migratetype(page, start_type);
+			return start_type;
+		}
+
+	}
+
+	return fallback_type;
+}
+
 /* Remove an element from the buddy allocator from the fallback list */
 static inline struct page *
 __rmqueue_fallback(struct zone *zone, int order, int start_migratetype)
@@ -1015,7 +1061,7 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype)
 	struct free_area *area;
 	int current_order;
 	struct page *page;
-	int migratetype, i;
+	int migratetype, new_type, i;
 
 	/* Find the largest possible block of pages in the other list */
 	for (current_order = MAX_ORDER-1; current_order >= order;
@@ -1035,51 +1081,28 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype)
 					struct page, lru);
 			area->nr_free--;
 
-			/*
-			 * If breaking a large block of pages, move all free
-			 * pages to the preferred allocation list. If falling
-			 * back for a reclaimable kernel allocation, be more
-			 * aggressive about taking ownership of free pages
-			 *
-			 * On the other hand, never change migration
-			 * type of MIGRATE_CMA pageblocks nor move CMA
-			 * pages on different free lists. We don't
-			 * want unmovable pages to be allocated from
-			 * MIGRATE_CMA areas.
-			 */
-			if (!is_migrate_cma(migratetype) &&
-			    (current_order >= pageblock_order / 2 ||
-			     start_migratetype == MIGRATE_RECLAIMABLE ||
-			     page_group_by_mobility_disabled)) {
-				int pages;
-				pages = move_freepages_block(zone, page,
-								start_migratetype);
-
-				/* Claim the whole block if over half of it is free */
-				if (pages >= (1 << (pageblock_order-1)) ||
-						page_group_by_mobility_disabled)
-					set_pageblock_migratetype(page,
-								start_migratetype);
-
-				migratetype = start_migratetype;
-			}
+			new_type = try_to_steal_freepages(zone, page,
+							  start_migratetype,
+							  migratetype);
 
 			/* Remove the page from the freelists */
 			list_del(&page->lru);
 			rmv_page_order(page);
 
-			/* Take ownership for orders >= pageblock_order */
-			if (current_order >= pageblock_order &&
-			    !is_migrate_cma(migratetype))
-				change_pageblock_range(page, current_order,
-							start_migratetype);
-
+			/*
+			 * Borrow the excess buddy pages as well, irrespective
+			 * of whether we stole freepages, or took ownership of
+			 * the pageblock or not.
+			 *
+			 * Exception: When borrowing from MIGRATE_CMA, release
+			 * the excess buddy pages to CMA itself.
+			 */
 			expand(zone, page, order, current_order, area,
 			       is_migrate_cma(migratetype)
 			     ? migratetype : start_migratetype);
 
 			trace_mm_page_alloc_extfrag(page, order, current_order,
-				start_migratetype, migratetype);
+				start_migratetype, new_type);
 
 			return page;
 		}