1 files changed, 39 insertions, 33 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d45203779b51..3541c12c47c9 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1078,39 +1078,34 @@ 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.
+ * When we are falling back to another migratetype during allocation, try to
+ * steal extra free pages from the same pageblocks to satisfy further
+ * allocations, instead of polluting multiple pageblocks.
  *
- * 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.
+ * If we are stealing a relatively large buddy page, it is likely there will
+ * be more free pages in the pageblock, so try to steal them all. For
+ * reclaimable and unmovable allocations, we steal regardless of page size,
+ * as fragmentation caused by those allocations polluting movable pageblocks
+ * is worse than movable allocations stealing from unmovable and reclaimable
+ * pageblocks.
  *
- * Returns the allocation migratetype if free pages were stolen, or the
- * fallback migratetype if it was decided not to steal.
+ * If we claim more than half of the pageblock, change pageblock's migratetype
+ * as well.
  */
-static int try_to_steal_freepages(struct zone *zone, struct page *page,
+static void try_to_steal_freepages(struct zone *zone, struct page *page,
 				  int start_type, int fallback_type)
 {
 	int current_order = page_order(page);
 
-	/*
-	 * When borrowing from MIGRATE_CMA, we need to release the excess
-	 * buddy pages to CMA itself. We also ensure the freepage_migratetype
-	 * is set to CMA so it is returned to the correct freelist in case
-	 * the page ends up being not actually allocated from the pcp lists.
-	 */
-	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;
+		return;
 	}
 
 	if (current_order >= pageblock_order / 2 ||
 	    start_type == MIGRATE_RECLAIMABLE ||
+	    start_type == MIGRATE_UNMOVABLE ||
 	    page_group_by_mobility_disabled) {
 		int pages;
 
@@ -1120,11 +1115,7 @@ static int try_to_steal_freepages(struct zone *zone, struct page *page,
 		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 */
@@ -1134,14 +1125,15 @@ __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype)
 	struct free_area *area;
 	unsigned int current_order;
 	struct page *page;
-	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 && current_order <= MAX_ORDER-1;
 				--current_order) {
+		int i;
 		for (i = 0;; i++) {
-			migratetype = fallbacks[start_migratetype][i];
+			int migratetype = fallbacks[start_migratetype][i];
+			int buddy_type = start_migratetype;
 
 			/* MIGRATE_RESERVE handled later if necessary */
 			if (migratetype == MIGRATE_RESERVE)
@@ -1155,22 +1147,36 @@ __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype)
 					struct page, lru);
 			area->nr_free--;
 
-			new_type = try_to_steal_freepages(zone, page,
-							  start_migratetype,
-							  migratetype);
+			if (!is_migrate_cma(migratetype)) {
+				try_to_steal_freepages(zone, page,
+							start_migratetype,
+							migratetype);
+			} else {
+				/*
+				 * When borrowing from MIGRATE_CMA, we need to
+				 * release the excess buddy pages to CMA
+				 * itself, and we do not try to steal extra
+				 * free pages.
+				 */
+				buddy_type = migratetype;
+			}
 
 			/* Remove the page from the freelists */
 			list_del(&page->lru);
 			rmv_page_order(page);
 
 			expand(zone, page, order, current_order, area,
-			       new_type);
-			/* The freepage_migratetype may differ from pageblock's
+					buddy_type);
+
+			/*
+			 * The freepage_migratetype may differ from pageblock's
 			 * migratetype depending on the decisions in
-			 * try_to_steal_freepages. This is OK as long as it does
-			 * not differ for MIGRATE_CMA type.
+			 * try_to_steal_freepages(). This is OK as long as it
+			 * does not differ for MIGRATE_CMA pageblocks. For CMA
+			 * we need to make sure unallocated pages flushed from
+			 * pcp lists are returned to the correct freelist.
 			 */
-			set_freepage_migratetype(page, new_type);
+			set_freepage_migratetype(page, buddy_type);
 
 			trace_mm_page_alloc_extfrag(page, order, current_order,
 				start_migratetype, migratetype);