linux-kernel - Re: [PATCH -mm v8 1/7] memcg: add page_cgroup

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Message-ID: <CAJu=L5_Hc-p7n79S-qoSepFR4nVhjR8QkFysKvWPvzb5tqhZOw@mail.gmail.com>
Date:	Wed, 15 Jul 2015 11:59:22 -0700
From:	Andres Lagar-Cavilla <andreslc@...gle.com>
To:	Vladimir Davydov <vdavydov@...allels.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan@...nel.org>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Greg Thelen <gthelen@...gle.com>,
	Michel Lespinasse <walken@...gle.com>,
	David Rientjes <rientjes@...gle.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Jonathan Corbet <corbet@....net>, linux-api@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm v8 1/7] memcg: add page_cgroup_ino helper

On Wed, Jul 15, 2015 at 6:54 AM, Vladimir Davydov
<vdavydov@...allels.com> wrote:
> This function returns the inode number of the closest online ancestor of
> the memory cgroup a page is charged to. It is required for exporting
> information about which page is charged to which cgroup to userspace,
> which will be introduced by a following patch.
>
> Signed-off-by: Vladimir Davydov <vdavydov@...allels.com>

Reviewed-by: Andres Lagar-Cavilla <andreslc@...gle.com>

> ---
>  include/linux/memcontrol.h |  1 +
>  mm/memcontrol.c            | 23 +++++++++++++++++++++++
>  2 files changed, 24 insertions(+)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 73b02b0a8f60..50069abebc3c 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -116,6 +116,7 @@ static inline bool mm_match_cgroup(struct mm_struct *mm,
>
>  extern struct cgroup_subsys_state *mem_cgroup_css(struct mem_cgroup *memcg);
>  extern struct cgroup_subsys_state *mem_cgroup_css_from_page(struct page *page);
> +extern unsigned long page_cgroup_ino(struct page *page);
>
>  struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *,
>                                    struct mem_cgroup *,
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index acb93c554f6e..894dc2169979 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -631,6 +631,29 @@ struct cgroup_subsys_state *mem_cgroup_css_from_page(struct page *page)
>         return &memcg->css;
>  }
>
> +/**
> + * page_cgroup_ino - return inode number of the memcg a page is charged to
> + * @page: the page
> + *
> + * Look up the closest online ancestor of the memory cgroup @page is charged to
> + * and return its inode number or 0 if @page is not charged to any cgroup. It
> + * is safe to call this function without holding a reference to @page.
> + */
> +unsigned long page_cgroup_ino(struct page *page)
> +{
> +       struct mem_cgroup *memcg;
> +       unsigned long ino = 0;
> +
> +       rcu_read_lock();
> +       memcg = READ_ONCE(page->mem_cgroup);
> +       while (memcg && !(memcg->css.flags & CSS_ONLINE))
> +               memcg = parent_mem_cgroup(memcg);
> +       if (memcg)
> +               ino = cgroup_ino(memcg->css.cgroup);
> +       rcu_read_unlock();
> +       return ino;
> +}
> +
>  static struct mem_cgroup_per_zone *
>  mem_cgroup_page_zoneinfo(struct mem_cgroup *memcg, struct page *page)
>  {
> --
> 2.1.4
>



-- 
Andres Lagar-Cavilla | Google Kernel Team | andreslc@...gle.com
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