Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936071AbZAPCNV (ORCPT ); Thu, 15 Jan 2009 21:13:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762151AbZAPCNA (ORCPT ); Thu, 15 Jan 2009 21:13:00 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:55820 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761558AbZAPCM7 (ORCPT ); Thu, 15 Jan 2009 21:12:59 -0500 Date: Thu, 15 Jan 2009 18:12:43 -0800 From: Andrew Morton To: Daisuke Nishimura Cc: KAMEZAWA Hiroyuki , "LKML" , "linux-mm" , "Balbir Singh" , "Pavel Emelyanov" , "Li Zefan" , "Paul Menage" Subject: Re: [BUGFIX][PATCH] memcg: get/put parents at create/free Message-Id: <20090115181243.8dad9052.akpm@linux-foundation.org> In-Reply-To: <20090116105009.7cabac46.nishimura@mxp.nes.nec.co.jp> References: <20090113184533.6ffd2af9.nishimura@mxp.nes.nec.co.jp> <20090114175121.275ecd59.nishimura@mxp.nes.nec.co.jp> <7602a77a9fc6b1e8757468048fde749a.squirrel@webmail-b.css.fujitsu.com> <20090115100330.37d89d3d.nishimura@mxp.nes.nec.co.jp> <20090115110044.3a863af8.kamezawa.hiroyu@jp.fujitsu.com> <20090115111420.8559bdb3.nishimura@mxp.nes.nec.co.jp> <20090115133814.a52460fa.nishimura@mxp.nes.nec.co.jp> <20090115164537.d402e95f.nishimura@mxp.nes.nec.co.jp> <20090115165453.271848d9.kamezawa.hiroyu@jp.fujitsu.com> <20090115171315.965da4e3.nishimura@mxp.nes.nec.co.jp> <20090115172336.0ed780bb.kamezawa.hiroyu@jp.fujitsu.com> <20090115175131.9542ae59.nishimura@mxp.nes.nec.co.jp> <20090115181056.74a938d5.kamezawa.hiroyu@jp.fujitsu.com> <20090116105009.7cabac46.nishimura@mxp.nes.nec.co.jp> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.5; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2937 Lines: 85 On Fri, 16 Jan 2009 10:50:09 +0900 Daisuke Nishimura wrote: > This version works well in my test. > > Andrew, please pick up this one. > > === > From: Daisuke Nishimura > > The lifetime of struct cgroup and struct mem_cgroup is different and > mem_cgroup has its own reference count for handling references from swap_cgroup. > > This causes strange problem that the parent mem_cgroup dies while > child mem_cgroup alive, and this problem causes a bug in case of use_hierarchy==1 > because res_counter_uncharge climbs up the tree. > > This patch is for avoiding it by getting the parent at create, and > putting it at freeing. > > Signed-off-by: Daisuke Nishimura > Reviewed-by; KAMEZAWA Hiroyuki > --- > mm/memcontrol.c | 23 ++++++++++++++++++++++- > 1 files changed, 22 insertions(+), 1 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index fb62b43..45e1b51 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -202,6 +202,8 @@ pcg_default_flags[NR_CHARGE_TYPE] = { > > static void mem_cgroup_get(struct mem_cgroup *mem); > static void mem_cgroup_put(struct mem_cgroup *mem); > +static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem); > +static void mem_cgroup_get_parent(struct mem_cgroup *mem); > > static void mem_cgroup_charge_statistics(struct mem_cgroup *mem, > struct page_cgroup *pc, > @@ -2185,10 +2187,28 @@ static void mem_cgroup_get(struct mem_cgroup *mem) > > static void mem_cgroup_put(struct mem_cgroup *mem) > { > - if (atomic_dec_and_test(&mem->refcnt)) > + if (atomic_dec_and_test(&mem->refcnt)) { > + struct mem_cgroup *parent = parent_mem_cgroup(mem); > __mem_cgroup_free(mem); > + if (parent) > + mem_cgroup_put(parent); > + } > +} > + > +static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem) > +{ > + if (!mem->res.parent) > + return NULL; > + return mem_cgroup_from_res_counter(mem->res.parent, res); > } > > +static void mem_cgroup_get_parent(struct mem_cgroup *mem) > +{ > + struct mem_cgroup *parent = parent_mem_cgroup(mem); > + > + if (parent) > + mem_cgroup_get(parent); > +} > > #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP > static void __init enable_swap_cgroup(void) > @@ -2237,6 +2257,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont) > if (parent) > mem->swappiness = get_swappiness(parent); > atomic_set(&mem->refcnt, 1); > + mem_cgroup_get_parent(mem); > return &mem->css; > free_out: > __mem_cgroup_free(mem); It seems strange that we add a little helper function for the get(), but open-code the put()? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/