linux-kernel - Re: [patch 6/8] mm: memcg: remove unneeded checks from uncharge

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Date:	Thu, 24 Nov 2011 09:06:19 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>,
	Balbir Singh <bsingharora@...il.com>, cgroups@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 6/8] mm: memcg: remove unneeded checks from
 uncharge_page()

On Wed, 23 Nov 2011 16:42:29 +0100
Johannes Weiner <hannes@...xchg.org> wrote:

> From: Johannes Weiner <jweiner@...hat.com>
> 
> mem_cgroup_uncharge_page() is only called on either freshly allocated
> pages without page->mapping or on rmapped PageAnon() pages.  There is
> no need to check for a page->mapping that is not an anon_vma.
> 
> Signed-off-by: Johannes Weiner <jweiner@...hat.com>

For making our assumption clearer to readers of codes,
VM_BUG_ON(page->mapping && !PageAnon(page)) please.

Anyway,
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>


> ---
>  mm/memcontrol.c |    2 --
>  1 files changed, 0 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 0d10be4..b9a3b94 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2989,8 +2989,6 @@ void mem_cgroup_uncharge_page(struct page *page)
>  	/* early check. */
>  	if (page_mapped(page))
>  		return;
> -	if (page->mapping && !PageAnon(page))
> -		return;
>  	__mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_MAPPED);
>  }
>  
> -- 
> 1.7.6.4
> 
> --
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