[PATCH] mm: skip watermarks check for already isolated blocks insplit_free_page()

[Marek Szyprowski]

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@xxxxxxxxxxx>
---
 mm/page_alloc.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index fd154fe..43ab09f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1394,10 +1394,12 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype)
 	zone = page_zone(page);
 	order = page_order(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 (get_pageblock_migratetype(page) != 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;
+	}
 
 	/* Remove page from free list */
 	list_del(&page->lru);
-- 
1.7.9.5

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