Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758600AbZAOCax (ORCPT ); Wed, 14 Jan 2009 21:30:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753137AbZAOCao (ORCPT ); Wed, 14 Jan 2009 21:30:44 -0500 Received: from TYO202.gate.nec.co.jp ([202.32.8.206]:33451 "EHLO tyo202.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753075AbZAOCao (ORCPT ); Wed, 14 Jan 2009 21:30:44 -0500 Date: Thu, 15 Jan 2009 11:14:20 +0900 From: Daisuke Nishimura To: KAMEZAWA Hiroyuki Cc: nishimura@mxp.nes.nec.co.jp, "LKML" , "linux-mm" , "Andrew Morton" , "Balbir Singh" , "Pavel Emelyanov" , "Li Zefan" , "Paul Menage" Subject: Re: [RFC][PATCH 5/4] memcg: don't call res_counter_uncharge when obsolete Message-Id: <20090115111420.8559bdb3.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20090115110044.3a863af8.kamezawa.hiroyu@jp.fujitsu.com> 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> Organization: NEC Soft, Ltd. X-Mailer: Sylpheed 2.4.8 (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: 4587 Lines: 152 > > > To handle the problem "parent may be obsolete", > > > > > > call mem_cgroup_get(parent) at create() > > > call mem_cgroup_put(parent) at freeing memcg. > > > (regardless of use_hierarchy.) > > > > > > is clearer way to go, I think. > > > > > > I wonder whether there is mis-accounting problem or not.. > > > > > > So, adding css_tryget() around problematic code can be a fix. > > > -- > > > mem = swap_cgroup_record(); > > > if (css_tryget(&mem->css)) { > > > res_counter_uncharge(&mem->memsw, PAZE_SIZE); > > > css_put(&mem->css) > > > } > > > -- > > > I like css_tryget() rather than mem_cgroup_obsolete(). > > I agree. > > The updated version is attached. > > > > > > Thanks, > > Daisuke nishimura. > > > > > To be honest, I'd like to remove memcg special stuff when I can. > > > > > > Thanks, > > > -Kame > > > > > === > > 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. > > > > Check if the memcg is obsolete by css_tryget, and don't call > > res_counter_uncharge when obsole. > > > > Signed-off-by: Daisuke Nishimura > seems nice loock. > > > > --- > > mm/memcontrol.c | 15 ++++++++++++--- > > 1 files changed, 12 insertions(+), 3 deletions(-) > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index fb62b43..4e3b100 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -1182,7 +1182,10 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm, > > /* avoid double counting */ > > mem = swap_cgroup_record(ent, NULL); > > if (mem) { > > - res_counter_uncharge(&mem->memsw, PAGE_SIZE); > > + if (!css_tryget(&mem->css)) { > > + res_counter_uncharge(&mem->memsw, PAGE_SIZE); > > + css_put(&mem->css); > > + } > > mem_cgroup_put(mem); > > } > > } > > I think css_tryget() returns "ture" at success.... > > So, > == > if (mem && css_tryget(&mem->css)) > res_counter.... > > is correct. > > -Kame > Ooops! you are right. Sorry for my silly mistake.. "mem" is checked beforehand, so I think css_tryget would be enough. I'm now testing the attached one. Thanks, Daisuke Nishimura. === 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. Check if the memcg is obsolete by css_tryget, and don't call res_counter_uncharge when obsole. Signed-off-by: Daisuke Nishimura --- mm/memcontrol.c | 15 ++++++++++++--- 1 files changed, 12 insertions(+), 3 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index fb62b43..b9d5271 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1182,7 +1182,10 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm, /* avoid double counting */ mem = swap_cgroup_record(ent, NULL); if (mem) { - res_counter_uncharge(&mem->memsw, PAGE_SIZE); + if (css_tryget(&mem->css)) { + res_counter_uncharge(&mem->memsw, PAGE_SIZE); + css_put(&mem->css); + } mem_cgroup_put(mem); } } @@ -1252,7 +1255,10 @@ void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr) struct mem_cgroup *memcg; memcg = swap_cgroup_record(ent, NULL); if (memcg) { - res_counter_uncharge(&memcg->memsw, PAGE_SIZE); + if (css_tryget(&memcg->css)) { + res_counter_uncharge(&memcg->memsw, PAGE_SIZE); + css_put(&memcg->css); + } mem_cgroup_put(memcg); } @@ -1397,7 +1403,10 @@ void mem_cgroup_uncharge_swap(swp_entry_t ent) memcg = swap_cgroup_record(ent, NULL); if (memcg) { - res_counter_uncharge(&memcg->memsw, PAGE_SIZE); + if (css_tryget(&memcg->css)) { + res_counter_uncharge(&memcg->memsw, PAGE_SIZE); + css_put(&memcg->css); + } mem_cgroup_put(memcg); } } -- 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/