linux-kernel - [PATCH 1/6] mm/page_alloc: fix same zone check in __pageblock_pfn_to

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Date:	Mon, 14 Mar 2016 16:31:32 +0900
From:	js1304@...il.com
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Mel Gorman <mgorman@...e.de>,
	Laura Abbott <lauraa@...eaurora.org>,
	Minchan Kim <minchan@...nel.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: [PATCH 1/6] mm/page_alloc: fix same zone check in __pageblock_pfn_to_page()

From: Joonsoo Kim <iamjoonsoo.kim@....com>

There is a system that node's pfn are overlapped like as following.

-----pfn-------->
N0 N1 N2 N0 N1 N2

Therefore, we need to care this overlapping when iterating pfn range.

In __pageblock_pfn_to_page(), there is a check for this but it's
not sufficient. This check cannot distinguish the case that zone id
is the same but node id is different. This patch fixes it.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
---
 mm/page_alloc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8120f07..93293b4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1173,8 +1173,7 @@ struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
 
 	end_page = pfn_to_page(end_pfn);
 
-	/* This gives a shorter code than deriving page_zone(end_page) */
-	if (page_zone_id(start_page) != page_zone_id(end_page))
+	if (zone != page_zone(end_page))
 		return NULL;
 
 	return start_page;
-- 
1.9.1