From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 81B506B0044 for ; Thu, 15 Jan 2009 23:25:58 -0500 (EST) Date: Fri, 16 Jan 2009 13:22:53 +0900 From: Daisuke Nishimura Subject: Re: [BUGFIX][PATCH] memcg: get/put parents at create/free Message-Id: <20090116132253.69cf80ea.nishimura@mxp.nes.nec.co.jp> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: KAMEZAWA Hiroyuki , LKML , linux-mm , Balbir Singh , Pavel Emelyanov , Li Zefan , Paul Menage , nishimura@mxp.nes.nec.co.jp List-ID: This is a fix for memcg-get-put-parents-at-create-free.patch. === From: Daisuke Nishimura Andrew suggested that it's strange to add a little helper function for get(), while put() is open-code. This patch also adds a few comments. Signed-off-by: Daisuke Nishimura --- mm/memcontrol.c | 20 ++++++++++---------- 1 files changed, 10 insertions(+), 10 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 45e1b51..92790e4 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -203,7 +203,6 @@ 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, @@ -2195,6 +2194,9 @@ static void mem_cgroup_put(struct mem_cgroup *mem) } } +/* + * Returns the parent mem_cgroup in memcgroup hierarchy with hierarchy enabled. + */ static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem) { if (!mem->res.parent) @@ -2202,14 +2204,6 @@ static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem) 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) { @@ -2247,6 +2241,13 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont) if (parent && parent->use_hierarchy) { res_counter_init(&mem->res, &parent->res); res_counter_init(&mem->memsw, &parent->memsw); + /* + * We increment refcnt of the parent to ensure that we can + * safely access it on res_counter_charge/uncharge. + * This refcnt will be decremented when freeing this + * mem_cgroup(see mem_cgroup_put). + */ + mem_cgroup_get(parent); } else { res_counter_init(&mem->res, NULL); res_counter_init(&mem->memsw, NULL); @@ -2257,7 +2258,6 @@ 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org