linux-kernel - Re: [PATCH 06/10] cgroup: convert memcg controller to the new cftype interface

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Message-ID: <4F695C3F.3000406@jp.fujitsu.com>
Date:	Wed, 21 Mar 2012 13:42:39 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Tejun Heo <tj@...nel.org>
CC:	glommer@...allels.com, lizf@...fujitsu.com,
	containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org, fweisbec@...il.com, rni@...gle.com,
	ctalbott@...gle.com, Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Balbir Singh <bsingharora@...il.com>,
	Hugh Dickins <hughd@...gle.com>,
	Greg Thelen <gthelen@...gle.com>
Subject: Re: [PATCH 06/10] cgroup: convert memcg controller to the new cftype
 interface

(2012/03/20 1:10), Tejun Heo wrote:

> Hello,
> 
> On Mon, Mar 19, 2012 at 01:26:02PM +0900, KAMEZAWA Hiroyuki wrote:
>>> +CGROUP_SUBSYS_CFTYPES_COND(mem_cgroup_subsys, memsw_cgroup_files,
>>> +			   really_do_swap_account);
>>
>>
>> I'm sorry but why you use really_do_swap_account instead of do_swap_account ?
> 
> Because do_swap_account is initialized too late.
> CGROUP_SUBSYS_CFTYPES() are processed via fs_initcall().  AFAICS,
> do_swap_account may not have been initialized by then.  Also, if memcg
> as whole is disabled, it doesn't matter whether those files are
> registered or not, right?  We probably need some comment there tho.
> 


I think creating file based on really_do_swap_account is wrong.
(I'm sorry for this complication.)

How about creating this file unconditionally ? Returning -ENOTSUP in memcg's
handler will work well...anyway it's configured, no reason to show them is bad.

Thanks,
-Kame

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