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Date: Sat, 08 Nov 2008 17:39:17 +0800
From: Li Zefan <lizf@cn.fujitsu.com>
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To: Balbir Singh <balbir@linux.vnet.ibm.com>
CC: linux-mm@kvack.org, YAMAMOTO Takashi <yamamoto@valinux.co.jp>,
       Paul Menage <menage@google.com>, linux-kernel@vger.kernel.org,
       Nick Piggin <nickpiggin@yahoo.com.au>,
       David Rientjes <rientjes@google.com>,
       Pavel Emelianov <xemul@openvz.org>,
       Dhaval Giani <dhaval@linux.vnet.ibm.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: [RFC][mm] [PATCH 4/4] Memory cgroup hierarchy feature selector
 (v2)
References: <20081108091009.32236.26177.sendpatchset@localhost.localdomain> <20081108091113.32236.12390.sendpatchset@localhost.localdomain>
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> +static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
> +					u64 val)
> +{
> +	int retval = 0;
> +	struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
> +
> +	if (val == 1) {
> +		if (list_empty(&cont->children))

cgroup_lock should be held before checking cont->children.

> +			mem->use_hierarchy = val;
> +		else
> +			retval = -EBUSY;
> +	} else if (val == 0) {

And code duplicate.

> +		if (list_empty(&cont->children))
> +			mem->use_hierarchy = val;
> +		else
> +			retval = -EBUSY;
> +	} else
> +		retval = -EINVAL;
> +
> +	return retval;
> +}
> +