[PATCH 4/6] mm/page_alloc: Remove unnecessary page == NULL check in rmqueue

[Mel Gorman <mgorman@techsingularity.net>]

The VM_BUG_ON check for a valid page can be avoided with a simple
change in the flow. The ZONE_BOOSTED_WATERMARK is unlikely in general
and even more unlikely if the page allocation failed so mark the
branch unlikely.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Tested-by: Minchan Kim <minchan@kernel.org>
Acked-by: Minchan Kim <minchan@kernel.org>
---
 mm/page_alloc.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1c4c54503a5d..b543333dce8f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3765,17 +3765,18 @@ struct page *rmqueue(struct zone *preferred_zone,
 
 	page = rmqueue_buddy(preferred_zone, zone, order, alloc_flags,
 							migratetype);
-	if (unlikely(!page))
-		return NULL;
 
 out:
 	/* Separate test+clear to avoid unnecessary atomics */
-	if (test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags)) {
+	if (unlikely(test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags))) {
 		clear_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
 		wakeup_kswapd(zone, 0, 0, zone_idx(zone));
 	}
 
-	VM_BUG_ON_PAGE(page && bad_range(zone, page), page);
+	if (unlikely(!page))
+		return NULL;
+
+	VM_BUG_ON_PAGE(bad_range(zone, page), page);
 	return page;
 }
 
-- 
2.34.1