linux-kernel - Re: [PATCH] PM / Hibernate: allow hibernation with PAGE_POISONING

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Date:   Mon, 12 Sep 2016 19:47:47 +0200
From:   Pavel Machek <pavel@....cz>
To:     Anisse Astier <anisse@...ier.eu>
Cc:     David Rientjes <rientjes@...gle.com>,
        Michal Hocko <mhocko@...e.com>, linux-pm@...r.kernel.org,
        Mathias Krause <minipli@...glemail.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Laura Abbott <labbott@...oraproject.org>, linux-mm@...ck.org,
        Brad Spengler <spender@...ecurity.net>,
        Jianyu Zhan <nasa4836@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yves-Alexis Perez <corsac@...ian.org>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>,
        Len Brown <len.brown@...el.com>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        PaX Team <pageexec@...email.hu>,
        Dave Hansen <dave.hansen@...el.com>,
        Mel Gorman <mgorman@...e.de>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] PM / Hibernate: allow hibernation with
 PAGE_POISONING_ZERO

Hi!

On Mon 2016-09-12 17:19:54, Anisse Astier wrote:
> Le 12 sept. 2016 13:32, "Pavel Machek" <pavel@....cz> a écrit :
> >
> > 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@...ier.eu>
> > > Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > > Cc: Laura Abbott <labbott@...oraproject.org>
> > > Cc: Mel Gorman <mgorman@...e.de>
> > > Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> >
> > Looks reasonable to me.
> >
> > Acked-by: Pavel Machek <pavel@....cz>
> >
> > Actually.... this takes basically zero time come. Do we want to do it
> > unconditionally?
> >
> > (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,
> >
> Pavel
> > --
> 
> I have no opposition on doing this unconditionally. I can send a v2 as soon
> as I get closer to a computer.

Actually, I'd keep this one as is, when it works and there are no
problems for a release or so, we can delete the ifdefs.

Thanks!
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html