linux-kernel - Re: [PATCH next/mmotm] swap: add per-partition lock for swapfile fix

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Message-ID: <20130128000705.GA1306@kernel.org>
Date:	Mon, 28 Jan 2013 08:07:05 +0800
From:	Shaohua Li <shli@...nel.org>
To:	Hugh Dickins <hughd@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	Shaohua Li <shli@...ionio.com>, Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan@...nel.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH next/mmotm] swap: add per-partition lock for swapfile fix

On Sun, Jan 27, 2013 at 01:47:01PM -0800, Hugh Dickins wrote:
> I had all cpus spinning in swap_info_get(), for the lock on an area
> being swapped off: probably because get_swap_page() forgot to unlock.
> 
> Signed-off-by: Hugh Dickins <hughd@...gle.com>

Good catch. Thanks!

> ---
> 
>  mm/swapfile.c |    5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> --- mmotm.orig/mm/swapfile.c	2013-01-23 17:55:39.132447115 -0800
> +++ mmotm/mm/swapfile.c	2013-01-27 10:41:45.000000000 -0800
> @@ -470,10 +470,9 @@ swp_entry_t get_swap_page(void)
>  		spin_unlock(&swap_lock);
>  		/* This is called for allocating swap entry for cache */
>  		offset = scan_swap_map(si, SWAP_HAS_CACHE);
> -		if (offset) {
> -			spin_unlock(&si->lock);
> +		spin_unlock(&si->lock);
> +		if (offset)
>  			return swp_entry(type, offset);
> -		}
>  		spin_lock(&swap_lock);
>  		next = swap_list.next;
>  	}
--
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