linux-kernel - Re: [PATCH] memcg: clean up soft_limit

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Date:	Wed, 14 Dec 2011 10:16:36 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Michal Hocko <mhocko@...e.cz>, Hillf Danton <dhillf@...il.com>,
	Hugh Dickins <hughd@...gle.com>,
	Balbir Singh <bsingharora@...il.com>,
	David Rientjes <rientjes@...gle.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] memcg: clean up soft_limit_tree properly new

On Tue, 13 Dec 2011 17:00:12 -0800
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Mon, 12 Dec 2011 15:09:35 +0100
> Michal Hocko <mhocko@...e.cz> wrote:
> 
> > And a follow up patch for the proper clean up:
> > ---
> > >From 4b9f5a1e88496af9f336d1ef37cfdf3754a3ba48 Mon Sep 17 00:00:00 2001
> > From: Michal Hocko <mhocko@...e.cz>
> > Date: Mon, 12 Dec 2011 15:04:18 +0100
> > Subject: [PATCH] memcg: clean up soft_limit_tree properly
> > 
> > If we are not able to allocate tree nodes for all NUMA nodes then we
> > should better clean up those that were allocated otherwise we will leak
> > a memory.
> > 
> > Signed-off-by: Michal Hocko <mhocko@...e.cz>
> > ---
> >  mm/memcontrol.c |   12 +++++++++++-
> >  1 files changed, 11 insertions(+), 1 deletions(-)
> > 
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index 6aff93c..838d812 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -4874,7 +4874,7 @@ static int mem_cgroup_soft_limit_tree_init(void)
> >  			tmp = -1;
> >  		rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, tmp);
> >  		if (!rtpn)
> > -			return 1;
> > +			goto err_cleanup;
> >  
> >  		soft_limit_tree.rb_tree_per_node[node] = rtpn;
> >  
> > @@ -4885,6 +4885,16 @@ static int mem_cgroup_soft_limit_tree_init(void)
> >  		}
> >  	}
> >  	return 0;
> > +
> > +err_cleanup:
> > +	for_each_node_state(node, N_POSSIBLE) {
> > +		if (!soft_limit_tree.rb_tree_per_node[node])
> > +			break;
> > +		kfree(soft_limit_tree.rb_tree_per_node[node]);
> > +		soft_limit_tree.rb_tree_per_node[node] = NULL;
> > +	}
> > +	return 1;
> > +
> >  }
> 
> afacit the kernel never frees the soft_limit_tree.rb_tree_per_node[]
> entries on the mem_cgroup_destroy() path.  Bug?
> 

soft_limit_tree.rb_tree_per_node[] is a global object and allocated once
at creating root cgroup.

Nodes of rb_tree for a memcg are contained in struct mem_cgroup_per_zone
and it's freed at mem_cgroup_destroy().

Thanks,
-Kame




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