linux-kernel - Re: [patch 03/11] mm: shmem: do not try to uncharge known swapcache pages

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Date:	Mon, 9 Jul 2012 16:46:57 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 03/11] mm: shmem: do not try to uncharge known swapcache
 pages

On Thu 05-07-12 02:44:55, Johannes Weiner wrote:
> Once charged, swapcache pages can only be uncharged after they are
> removed from swapcache again.
> 
> Do not try to uncharge pages that are known to be in the swapcache, to
> allow future patches to remove checks for that in the uncharge code.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> ---
>  mm/shmem.c |   11 ++++++-----
>  1 files changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index ee1c5a2..d12b705 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -302,8 +302,6 @@ static int shmem_add_to_page_cache(struct page *page,
>  		if (!expected)
>  			radix_tree_preload_end();
>  	}
> -	if (error)
> -		mem_cgroup_uncharge_cache_page(page);

Maybe I am missing something but who does the uncharge from:
shmem_unuse
  mem_cgroup_cache_charge
  shmem_unuse_inode
    shmem_add_to_page_cache

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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