Re: [PATCH] PM / Hibernate: allow hibernation with PAGE_POISONING_ZERO

From: Pavel Machek
Date: Mon Sep 12 2016 - 07:32:48 EST

On Fri 2016-09-09 10:43:32, Anisse Astier wrote:
> PAGE_POISONING_ZERO disables zeroing new pages on alloc, they are
> poisoned (zeroed) as they become available.
> In the hibernate use case, free pages will appear in the system without
> being cleared, left there by the loading kernel.
> This patch will make sure free pages are cleared on resume when
> PAGE_POISONING_ZERO is enabled. We free the pages just after resume
> because we can't do it later: going through any device resume code might
> allocate some memory and invalidate the free pages bitmap.
> Thus we don't need to disable hibernation when PAGE_POISONING_ZERO is
> enabled.
> Signed-off-by: Anisse Astier <anisse@xxxxxxxxx>
> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Cc: Laura Abbott <labbott@xxxxxxxxxxxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxx>
> Cc: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>

Looks reasonable to me.

Acked-by: Pavel Machek <pavel@xxxxxx>

Actually.... this takes basically zero time come. Do we want to do it

(Yes, it is free memory, but for sake of debugging, I guess zeros are
preffered to random content that changed during hibernation.)

(But that does not change the Ack.)

Best regards,
(cesky, pictures)