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

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Message-Id: <20080901150417.96a6a322.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Mon, 1 Sep 2008 15:04:17 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Pavel Emelianov <xemul@...nvz.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] res_counter: fix off-by-one bug in setting limit

On Mon, 01 Sep 2008 13:43:57 +0800
Li Zefan <lizf@...fujitsu.com> wrote:

> KAMEZAWA Hiroyuki wrote:
> > On Mon, 01 Sep 2008 13:08:55 +0800
> > Li Zefan <lizf@...fujitsu.com> wrote:
> > 
> >> 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>
> > 
> > But setting limit to 0(usage) in memcg is buggy operation unless you want to see OOM..
> > Hmm..
> > 
> 
> I used to set 0 limit to test OOM in memcg. I don't think 0 limit is buggy, there's no
> much difference with 0 limit and a very low limit.
> 
> And the real issue is, now we can set limit to > usage, but not >= usage. It's odd that
> usage can reach to limit but limit can't be shrinked to usage.
> 
ok.

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

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