linux-kernel - [RFC] mm: fix a BUG, the page is allocated 2 times

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Date:	Mon, 12 Oct 2015 10:40:06 +0800
From:	yalin wang <yalin.wang2010@...il.com>
To:	akpm@...ux-foundation.org, vbabka@...e.cz,
	mgorman@...hsingularity.net, mhocko@...e.com, rientjes@...gle.com,
	js1304@...il.com, kirill.shutemov@...ux.intel.com,
	hannes@...xchg.org, alexander.h.duyck@...hat.com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:	yalin wang <yalin.wang2010@...il.com>
Subject: [RFC] mm: fix a BUG, the page is allocated 2 times

Remove unlikely(order), because we are sure order is not zero if
code reach here, also add if (page == NULL), only allocate page again if
__rmqueue_smallest() failed or alloc_flags & ALLOC_HARDER == 0

Signed-off-by: yalin wang <yalin.wang2010@...il.com>
---
 mm/page_alloc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0d6f540..de82e2c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2241,13 +2241,13 @@ struct page *buffered_rmqueue(struct zone *preferred_zone,
 		spin_lock_irqsave(&zone->lock, flags);
 
 		page = NULL;
-		if (unlikely(order) && (alloc_flags & ALLOC_HARDER)) {
+		if (alloc_flags & ALLOC_HARDER) {
 			page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
 			if (page)
 				trace_mm_page_alloc_zone_locked(page, order, migratetype);
 		}
-
-		page = __rmqueue(zone, order, migratetype, gfp_flags);
+		if (page == NULL)
+			page = __rmqueue(zone, order, migratetype, gfp_flags);
 		spin_unlock(&zone->lock);
 		if (!page)
 			goto failed;
-- 
1.9.1

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