mm: cma: skip watermarks check for already isolated blocks in split_free_page()

Since commit 2139cbe627b8 ("cma: fix counting of isolated pages") free
pages in isolated pageblocks are not accounted to NR_FREE_PAGES counters,
so watermarks check is not required if one operates on a free page in
isolated pageblock.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Mel Gorman <mel@csn.ul.ie>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 8 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d9fbac1b5030..265fea4fbc81 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1394,21 +1394,22 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype)
 
         zone = page_zone(page);
         order = page_order(page);
+        mt = get_pageblock_migratetype(page);
 
-        /* Obey watermarks as if the page was being allocated */
-        watermark = low_wmark_pages(zone) + (1 << order);
-        if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
-                return 0;
+        if (mt != MIGRATE_ISOLATE) {
+                /* Obey watermarks as if the page was being allocated */
+                watermark = low_wmark_pages(zone) + (1 << order);
+                if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
+                        return 0;
+
+                __mod_zone_freepage_state(zone, -(1UL << alloc_order), mt);
+        }
 
         /* Remove page from free list */
         list_del(&page->lru);
         zone->free_area[order].nr_free--;
         rmv_page_order(page);
 
-        mt = get_pageblock_migratetype(page);
-        if (unlikely(mt != MIGRATE_ISOLATE))
-                __mod_zone_freepage_state(zone, -(1UL << alloc_order), mt);
-
         if (alloc_order != order)
                 expand(zone, page, alloc_order, order,
                         &zone->free_area[order], migratetype);