linux-kernel - Re: [PATCH 2/8] mm/swap: fix race on swap_info reuse between swapoff and swapon

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Message-Id: <20140203152340.b28bb35698ee75615eb23041@linux-foundation.org>
Date:	Mon, 3 Feb 2014 15:23:40 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Weijie Yang <weijie.yang@...sung.com>
Cc:	hughd@...gle.com, "'Minchan Kim'" <minchan@...nel.org>,
	shli@...nel.org, "'Bob Liu'" <bob.liu@...cle.com>,
	weijie.yang.kh@...il.com,
	"'Seth Jennings'" <sjennings@...iantweb.net>,
	"'Heesub Shin'" <heesub.shin@...sung.com>, mquzik@...hat.com,
	"'Linux-MM'" <linux-mm@...ck.org>,
	"'linux-kernel'" <linux-kernel@...r.kernel.org>,
	stable@...r.kernel.org
Subject: Re: [PATCH 2/8] mm/swap: fix race on swap_info reuse between
 swapoff and swapon

On Mon, 27 Jan 2014 18:03:04 +0800 Weijie Yang <weijie.yang@...sung.com> wrote:

> swapoff clear swap_info's SWP_USED flag prematurely and free its resources
> after that. A concurrent swapon will reuse this swap_info while its previous
> resources are not cleared completely.
> 
> These late freed resources are:
>  - p->percpu_cluster
>  - swap_cgroup_ctrl[type]
>  - block_device setting
>  - inode->i_flags &= ~S_SWAPFILE
> 
> This patch clear SWP_USED flag after all its resources freed, so that swapon
> can reuse this swap_info by alloc_swap_info() safely.
> 
> This patch is just for a rare scenario, aim to correct of code.

I believe that
http://ozlabs.org/~akpm/mmots/broken-out/mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon.patch
makes this patch redundant?

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