linux-kernel - Re: [PATCH 3/7] memcg: remove test for current->mm in memcg_stop/resume_kmem

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Message-ID: <50A4B5A0.8040102@jp.fujitsu.com>
Date:	Thu, 15 Nov 2012 18:28:00 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Glauber Costa <glommer@...allels.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>
Subject: Re: [PATCH 3/7] memcg: remove test for current->mm in memcg_stop/resume_kmem_account

(2012/11/15 11:54), Glauber Costa wrote:
> The original reason for the existence of this test, was that
> memcg_kmem_cache_create could be called from either softirq context
> (where memcg_stop/resume_account is not needed), or process context,
> (where memcg_stop/resume_account is needed). Just skipping it
> in-function was the cleanest way to merge both behaviors. The reason for
> that is that we would try to create caches right away through
> memcg_kmem_cache_create if the context would allow us to.
> 
> However, the final version of the code that merged did not have this
> behavior and we always queue up new cache creation. Thus, instead of a
> comment explaining why current->mm test is needed, my proposal in this
> patch is to remove memcg_stop/resume_account from the worker thread and
> make sure all callers have a valid mm context.
> 
> Signed-off-by: Glauber Costa <glommer@...allels.com>
> CC: Michal Hocko <mhocko@...e.cz>
> CC: Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> CC: Johannes Weiner <hannes@...xchg.org>
> CC: Andrew Morton <akpm@...ux-foundation.org>

seems ok to me. But do we need VM_BUG_ON() ?
It seems functions called under memcg_stop_kmem_account() doesn't access
current->mm...

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



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