linux-kernel - Re: [PATCH 0/2] memcg: mm_update_next

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Message-ID: <20140418184441.GA26046@redhat.com>
Date:	Fri, 18 Apr 2014 20:44:41 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Chiang <pchiang@...dia.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Balbir Singh <bsingharora@...il.com>,
	Johannes Weiner <hannes@...xchg.org>,
	"ccross@...roid.com" <ccross@...roid.com>,
	"lizefan@...wei.com" <lizefan@...wei.com>,
	"tj@...nel.org" <tj@...nel.org>, "pavel@....cz" <pavel@....cz>,
	"ebiederm@...ssion.com" <ebiederm@...ssion.com>,
	"guillaume@...infr.org" <guillaume@...infr.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/2] memcg: mm_update_next_owner() should skip kthreads

On 04/18, Michal Hocko wrote:
>
> On Fri 18-04-14 19:26:31, Oleg Nesterov wrote:
> > On 04/18, Oleg Nesterov wrote:
> > >
> > > Hmm. I seem to see a bug in this function, it can be fulled by use_mm,
> > > but I am not sure this can explain the problem. I'll send a patch.
> >
> > Untested, please review. But it really looks "obviously wrong", and note
> > that unuse_mm() doesn't do mm_update_next_owner(). (just in case, do not
> > confuse it with unuse_mm() in mm/swapfile.c).
>
> Both patches seem to be correct but I am missinng why they are marked as
> memcg: when they are touching generic mm_update_next_owner path.

Well, this is because I didn't know which prefix should I use. I looked
at git-blame to see who changed this function, picked the random 733eda7ac
"memcg: clear mm->owner when last possible owner leaves" commit and copied
"memcg" from there.

OTOH, mm->owner is used by mm/memcontrol.c, so perhaps the prefix is fine?

I do not even understand why do we have CONFIG_MM_OWNER, perhaps it should
die?

> Anyway, feel free to add
> Reviewed-by: Michal Hocko <mhocko@...e.cz>

Thanks!

Oleg.

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