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Message-Id: <20090116133121.2f50d71d.kamezawa.hiroyu@jp.fujitsu.com>
Date: Fri, 16 Jan 2009 13:31:21 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Cc: "Andrew Morton" <akpm@...ux-foundation.org>,
"LKML" <linux-kernel@...r.kernel.org>,
"linux-mm" <linux-mm@...ck.org>,
"Balbir Singh" <balbir@...ux.vnet.ibm.com>,
"Pavel Emelyanov" <xemul@...nvz.org>,
"Li Zefan" <lizf@...fujitsu.com>, "Paul Menage" <menage@...gle.com>
Subject: Re: [BUGFIX][PATCH] memcg: get/put parents at create/free
On Fri, 16 Jan 2009 13:22:53 +0900
Daisuke Nishimura <nishimura@....nes.nec.co.jp> wrote:
> This is a fix for memcg-get-put-parents-at-create-free.patch.
>
Thank you, I'll test.
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> ===
> From: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
>
> 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 <nishimura@....nes.nec.co.jp>
> ---
> 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);
>
--
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