linux-kernel - Re: [PATCH v3 1/6] memcg: fix error code in hugetlb_force_memcg

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Date:	Mon, 14 May 2012 10:07:34 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Han Ying <yinghan@...gle.com>,
	Glauber Costa <glommer@...allels.com>,
	Tejun Heo <tj@...nel.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Hiroyuki Kamezawa <kamezawa.hiroyuki@...il.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/6] memcg: fix error code in hugetlb_force_memcg_empty()

(2012/05/12 6:17), Andrew Morton wrote:

> On Fri, 11 May 2012 18:45:18 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> 
>> The conditions are handled as -EBUSY, _now_.
> 
> The changelog is poor.  I rewrote it to
> 
> : hugetlb_force_memcg_empty() incorrectly returns 0 (success) when the
> : cgroup is found to be busy.  Return -EBUSY instead.
> 
> But it still doesn't tell us the end-user-visible effects of the bug. 
> It should.
> 


Ah, sorry. How about this ?



The force_empty interface allows to make the memcg only when the cgroup
doesn't include any tasks.

	# echo 0 > /cgroup/xxxx/memory.force_empty

If cgroup isn't empty, force_empty does nothing and retruns -EBUSY in usual
memcg, memcontrol.c. But hugetlb implementation has inconsitency with
it and returns 0 and do nothing. Fix it to return -EBUSY.

Thanks,
-Kame


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