linux-kernel - [PATCH 2/3] memcg: fix off-by-one when calculating swap cgroup map length

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Date:	Fri, 18 Mar 2011 21:54:14 +0900
From:	Namhyung Kim <namhyung@...il.com>
To:	Paul Menage <menage@...gle.com>, Li Zefan <lizf@...fujitsu.com>
Cc:	containers@...ts.linux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: [PATCH 2/3] memcg: fix off-by-one when calculating swap cgroup map length

It allocated one more page than necessary if @max_pages was
a multiple of SC_PER_PAGE.

Signed-off-by: Namhyung Kim <namhyung@...il.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
---
 mm/page_cgroup.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
index 2d1a0fa01d7b..29951abc852e 100644
--- a/mm/page_cgroup.c
+++ b/mm/page_cgroup.c
@@ -446,7 +446,7 @@ int swap_cgroup_swapon(int type, unsigned long max_pages)
 	if (!do_swap_account)
 		return 0;
 
-	length = ((max_pages/SC_PER_PAGE) + 1);
+	length = DIV_ROUND_UP(max_pages, SC_PER_PAGE);
 	array_size = length * sizeof(void *);
 
 	array = vmalloc(array_size);
-- 
1.7.4

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