linux-kernel - [PATCH] res_counter: fix off-by-one bug in setting limit

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Date:	Mon, 01 Sep 2008 13:08:55 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Pavel Emelianov <xemul@...nvz.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] res_counter: fix off-by-one bug in setting limit

I found we can no longer set limit to 0 with 2.6.27-rcX:
 # mount -t cgroup -omemory xxx /mnt
 # mkdir /mnt/0
 # echo 0 > /mnt/0/memory.limit_in_bytes
 bash: echo: write error: Device or resource busy

It turned out 'limit' can't be set to 'usage', which is wrong IMO.

Signed-off-by: Li Zefan <lizf@...fujitsu.com>
---
 include/linux/res_counter.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
index fdeadd9..271c1c2 100644
--- a/include/linux/res_counter.h
+++ b/include/linux/res_counter.h
@@ -166,7 +166,7 @@ static inline int res_counter_set_limit(struct res_counter *cnt,
 	int ret = -EBUSY;
 
 	spin_lock_irqsave(&cnt->lock, flags);
-	if (cnt->usage < limit) {
+	if (cnt->usage <= limit) {
 		cnt->limit = limit;
 		ret = 0;
 	}
-- 1.5.4.rc3 
--
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