linux-kernel - Re: [patch 1/3] mm: fix pageref leak in do_swap

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Message-Id: <20090421083639.97ae549c.minchan.kim@barrios-desktop>
Date:	Tue, 21 Apr 2009 08:36:39 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Balbir Singh <balbir@...ux.vnet.ibm.com>
Subject: Re: [patch 1/3] mm: fix pageref leak in do_swap_page()

On Mon, 20 Apr 2009 22:24:43 +0200
Johannes Weiner <hannes@...xchg.org> wrote:

Nice catch!!
Reviewed-by: Minchan Kim <minchan.kim@...il.com>

> By the time the memory cgroup code is notified about a swapin we
> already hold a reference on the fault page.
> 
> If the cgroup callback fails make sure to unlock AND release the page
> or we leak the reference.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> Cc: Balbir Singh <balbir@...ux.vnet.ibm.com>
> ---
>  mm/memory.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 366dab5..db126b6 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2536,8 +2536,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
>  
>  	if (mem_cgroup_try_charge_swapin(mm, page, GFP_KERNEL, &ptr)) {
>  		ret = VM_FAULT_OOM;
> -		unlock_page(page);
> -		goto out;
> +		goto out_page;
>  	}
>  
>  	/*
> @@ -2599,6 +2598,7 @@ out:
>  out_nomap:
>  	mem_cgroup_cancel_charge_swapin(ptr);
>  	pte_unmap_unlock(page_table, ptl);
> +out_page:
>  	unlock_page(page);
>  	page_cache_release(page);
>  	return ret;
> -- 
> 1.6.2.1.135.gde769
> 
> --
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-- 
Kinds Regards
Minchan Kim
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