linux-kernel - Re: [PATCH 1/2] mm: add a function to return a bdi

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Message-ID: <20180801110356.GH16767@dhcp22.suse.cz>
Date:   Wed, 1 Aug 2018 13:03:56 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Li RongQing <lirongqing@...du.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>
Subject: Re: [PATCH 1/2] mm: add a function to return a bdi_writeback dirty
 page statistic

On Wed 01-08-18 18:48:35, Li RongQing wrote:
> this is a preparation to optimise a full writeback
> when reclaim memory

Please do not add unused functions. This makes review harder without a
good reason. Besides that we already have mem_cgroup_wb_stats. Why
cannot you reuse it?

> Signed-off-by: Zhang Yu <zhangyu31@...du.com>
> Signed-off-by: Li RongQing <lirongqing@...du.com>
> ---
>  include/linux/memcontrol.h | 2 +-
>  mm/memcontrol.c            | 6 ++++++
>  2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 6c6fb116e925..58e29555ac81 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1141,7 +1141,7 @@ struct wb_domain *mem_cgroup_wb_domain(struct bdi_writeback *wb);
>  void mem_cgroup_wb_stats(struct bdi_writeback *wb, unsigned long *pfilepages,
>  			 unsigned long *pheadroom, unsigned long *pdirty,
>  			 unsigned long *pwriteback);
> -
> +unsigned long mem_cgroup_wb_dirty_stats(struct bdi_writeback *wb);
>  #else	/* CONFIG_CGROUP_WRITEBACK */
>  
>  static inline struct wb_domain *mem_cgroup_wb_domain(struct bdi_writeback *wb)
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 8c0280b3143e..82d3061e91d1 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3640,6 +3640,12 @@ void mem_cgroup_wb_stats(struct bdi_writeback *wb, unsigned long *pfilepages,
>  	}
>  }
>  
> +unsigned long mem_cgroup_wb_dirty_stats(struct bdi_writeback *wb)
> +{
> +	struct mem_cgroup *memcg = mem_cgroup_from_css(wb->memcg_css);
> +
> +	return memcg_page_state(memcg, NR_FILE_DIRTY);
> +}
>  #else	/* CONFIG_CGROUP_WRITEBACK */
>  
>  static int memcg_wb_domain_init(struct mem_cgroup *memcg, gfp_t gfp)
> -- 
> 2.16.2

-- 
Michal Hocko
SUSE Labs