mm/page_alloc: reduce fallbacks to (MIGRATE_PCPTYPES - 1)

The commit 1dd214b8f21c ("mm: page_alloc: avoid merging non-fallbackable
pageblocks with others") has removed MIGRATE_CMA and MIGRATE_ISOLATE from
fallbacks list. so there is no need to add an element at the end of every
type.

Reduce fallbacks to (MIGRATE_PCPTYPES - 1).

Link: https://lkml.kernel.org/r/20230203100132.1627787-1-yajun.deng@linux.dev
Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5ebce58..21d820c 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2603,10 +2603,10 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
  *
  * The other migratetypes do not have fallbacks.
  */
-static int fallbacks[MIGRATE_TYPES][3] = {
-       [MIGRATE_UNMOVABLE]   = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE,   MIGRATE_TYPES },
-       [MIGRATE_MOVABLE]     = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_TYPES },
-       [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE,   MIGRATE_MOVABLE,   MIGRATE_TYPES },
+static int fallbacks[MIGRATE_TYPES][MIGRATE_PCPTYPES - 1] = {
+       [MIGRATE_UNMOVABLE]   = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE   },
+       [MIGRATE_MOVABLE]     = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE },
+       [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE,   MIGRATE_MOVABLE   },
 };
 
 #ifdef CONFIG_CMA
@@ -2865,11 +2865,8 @@ int find_suitable_fallback(struct free_area *area, unsigned int order,
                return -1;
 
        *can_steal = false;
-       for (i = 0;; i++) {
+       for (i = 0; i < MIGRATE_PCPTYPES - 1 ; i++) {
                fallback_mt = fallbacks[migratetype][i];
-               if (fallback_mt == MIGRATE_TYPES)
-                       break;
-
                if (free_area_empty(area, fallback_mt))
                        continue;