Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759367AbZAOIY7 (ORCPT ); Thu, 15 Jan 2009 03:24:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755535AbZAOIYu (ORCPT ); Thu, 15 Jan 2009 03:24:50 -0500 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:48613 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755530AbZAOIYu (ORCPT ); Thu, 15 Jan 2009 03:24:50 -0500 Date: Thu, 15 Jan 2009 17:23:36 +0900 From: KAMEZAWA Hiroyuki To: Daisuke Nishimura Cc: "LKML" , "linux-mm" , "Andrew Morton" , "Balbir Singh" , "Pavel Emelyanov" , "Li Zefan" , "Paul Menage" Subject: Re: [RFC][PATCH] memcg: get/put parents at create/free Message-Id: <20090115172336.0ed780bb.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090115171315.965da4e3.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> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 2.5.0 (GTK+ 2.10.14; i686-pc-mingw32) 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: 3072 Lines: 106 On Thu, 15 Jan 2009 17:13:15 +0900 Daisuke Nishimura wrote: > From: Daisuke Nishimura > > mem_cgroup_get ensures that the memcg that has been got can be accessed > even after the directory has been removed, but it doesn't ensure that parents > of it can be accessed: parents might have been freed already by rmdir. > > This causes a bug in case of use_hierarchy==1, because res_counter_uncharge > climb up the tree. > > This patch tries to fix this probrem by getting the parent at create, and > putting it at freeing. > > Signed-off-by: Daisuke Nishimura Seems very simple and promissive. But one nitpick > --- > mm/memcontrol.c | 29 ++++++++++++++++++++++++++++- > 1 files changed, 28 insertions(+), 1 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index fb62b43..a80ba68 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 void mem_cgroup_get_parent(struct mem_cgroup *mem); > +static void mem_cgroup_put_parent(struct mem_cgroup *mem); > > static void mem_cgroup_charge_statistics(struct mem_cgroup *mem, > struct page_cgroup *pc, > @@ -2185,10 +2187,34 @@ 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)) { > + mem_cgroup_put_parent(mem); > __mem_cgroup_free(mem); > + } > +} Here, parent is freed before children is freed. Then, == if (atomic_dec_and_test(&mem->refcnt)) { struct mem_cgroup *parent = parent_mem_cgroup(mem); __mem_cgroup_free(mem); mem_cgroup_put(parent); } == Is maybe usual way. -Kame > + > +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); > } > > +static void mem_cgroup_put_parent(struct mem_cgroup *mem) > +{ > + struct mem_cgroup *parent = parent_mem_cgroup(mem); > + > + if (parent) > + mem_cgroup_put(parent); > +} > > #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP > static void __init enable_swap_cgroup(void) > @@ -2237,6 +2263,7 @@ 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); > -- 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/