linux-kernel - Re: [PATCH 1/4] swap: revert special hibernation allocation

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Message-Id: <20100906171307.9e8d9637.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Mon, 6 Sep 2010 17:13:07 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Hugh Dickins <hughd@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Ondrej Zary <linux@...nbow-software.org>,
	Andrea Gelmini <andrea.gelmini@...il.com>,
	Balbir Singh <balbir@...ibm.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Nigel Cunningham <nigel@...onice.net>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] swap: revert special hibernation allocation

On Mon, 6 Sep 2010 01:10:55 -0700 (PDT)
Hugh Dickins <hughd@...gle.com> wrote:

> Please revert 2.6.36-rc commit d2997b1042ec150616c1963b5e5e919ffd0b0ebf
> "hibernation: freeze swap at hibernation".  It complicated matters by
> adding a second swap allocation path, just for hibernation; without in
> any way fixing the issue that it was intended to address - page reclaim
> after fixing the hibernation image might free swap from a page already
> imaged as swapcache, letting its swap be reallocated to store a different
> page of the image: resulting in data corruption if the imaged page were
> freed as clean then swapped back in.  Pages freed to si->swap_map were
> still in danger of being reallocated by the alternative allocation path.
> 
> I guess it inadvertently fixed slow SSD swap allocation for hibernation,
> as reported by Nigel Cunningham: by missing out the discards that occur
> on the usual swap allocation path; but that was unintentional, and needs
> a separate fix.
> 
> Signed-off-by: Hugh Dickins <hughd@...gle.com>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Cc: "Rafael J. Wysocki" <rjw@...k.pl>
> Cc: Ondrej Zary <linux@...nbow-software.org>
> Cc: Andrea Gelmini <andrea.gelmini@...il.com>
> Cc: Balbir Singh <balbir@...ibm.com>
> Cc: Andrea Arcangeli <aarcange@...hat.com>
> Cc: Nigel Cunningham <nigel@...onice.net>

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

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