linux-kernel - Re: [PATCH] mm/memcontrol:rewrite mem_cgroup_page

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Date:   Wed, 4 Nov 2020 14:38:00 -0800
From:   Roman Gushchin <guro@...com>
To:     Hui Su <sh_def@....com>
CC:     <hannes@...xchg.org>, <mhocko@...nel.org>,
        <vdavydov.dev@...il.com>, <akpm@...ux-foundation.org>,
        <shakeelb@...gle.com>, <laoar.shao@...il.com>,
        <chris@...isdown.name>, <linux-kernel@...r.kernel.org>,
        <cgroups@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH] mm/memcontrol:rewrite mem_cgroup_page_lruvec()

On Wed, Nov 04, 2020 at 10:25:16PM +0800, Hui Su wrote:
> mem_cgroup_page_lruvec() in memcontrol.c and
> mem_cgroup_lruvec() in memcontrol.h is very similar
> except for the param(page and memcg) which also can be
> convert to each other.
> 
> So rewrite mem_cgroup_page_lruvec() with mem_cgroup_lruvec().
> 
> Signed-off-by: Hui Su <sh_def@....com>
> ---
>  include/linux/memcontrol.h | 18 +++++++++++++++--
>  mm/memcontrol.c            | 40 --------------------------------------
>  2 files changed, 16 insertions(+), 42 deletions(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index e391e3c56de5..a586363fb766 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -457,9 +457,10 @@ mem_cgroup_nodeinfo(struct mem_cgroup *memcg, int nid)
>  /**
>   * mem_cgroup_lruvec - get the lru list vector for a memcg & node
>   * @memcg: memcg of the wanted lruvec
> + * @pgdat: pglist_data
>   *
>   * Returns the lru list vector holding pages for a given @memcg &
> - * @node combination. This can be the node lruvec, if the memory
> + * @pgdat combination. This can be the node lruvec, if the memory
>   * controller is disabled.
>   */
>  static inline struct lruvec *mem_cgroup_lruvec(struct mem_cgroup *memcg,
> @@ -489,7 +490,20 @@ static inline struct lruvec *mem_cgroup_lruvec(struct mem_cgroup *memcg,
>  	return lruvec;
>  }

Hi Hui,

>  
> -struct lruvec *mem_cgroup_page_lruvec(struct page *, struct pglist_data *);
> +/**
> + * mem_cgroup_page_lruvec - return lruvec for isolating/putting an LRU page
> + * @page: the page
> + * @pgdat: pgdat of the page
> + *
> + * This function relies on page->mem_cgroup being stable.
> + */
> +static inline struct lruvec *mem_cgroup_page_lruvec(struct page *page,
> +						struct pglist_data *pgdat)

Hm, do we need to pass page and pgdat?

> +{
> +	struct mem_cgroup *memcg = page->mem_cgroup;

It seems like you need to rebase the patch against the latest mm snapshot.

> +
> +	return mem_cgroup_lruvec(memcg, pgdat);

Thanks!