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

[KAMEZAWA Hiroyuki]

On Mon, 6 Sep 2010 01:10:55 -0700 (PDT)
Hugh Dickins <hughd@xxxxxxxxxx> 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@xxxxxxxxxx>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> Cc: "Rafael J. Wysocki" <rjw@xxxxxxx>
> Cc: Ondrej Zary <linux@xxxxxxxxxxxxxxxxxxxx>
> Cc: Andrea Gelmini <andrea.gelmini@xxxxxxxxx>
> Cc: Balbir Singh <balbir@xxxxxxxxxx>
> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> Cc: Nigel Cunningham <nigel@xxxxxxxxxxxx>

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

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