From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1757991AbcILLcp (ORCPT <rfc822;w@1wt.eu>);
        Mon, 12 Sep 2016 07:32:45 -0400
Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:57869 "EHLO
        atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1756103AbcILLcm (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Mon, 12 Sep 2016 07:32:42 -0400
Date: Mon, 12 Sep 2016 13:32:38 +0200
From: Pavel Machek <pavel@ucw.cz>
To: Anisse Astier <anisse@astier.eu>
Cc: linux-mm@kvack.org, linux-pm@vger.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Laura Abbott <labbott@fedoraproject.org>, Mel Gorman <mgorman@suse.de>,
        "Rafael J . Wysocki" <rjw@rjwysocki.net>,
        Alan Cox <gnomes@lxorguk.ukuu.org.uk>,
        Andi Kleen <andi@firstfloor.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Brad Spengler <spender@grsecurity.net>,
        Dave Hansen <dave.hansen@intel.com>,
        David Rientjes <rientjes@google.com>, Jianyu Zhan <nasa4836@gmail.com>,
        Kees Cook <keescook@chromium.org>, Len Brown <len.brown@intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Mathias Krause <minipli@googlemail.com>,
        Michal Hocko <mhocko@suse.com>, PaX Team <pageexec@freemail.hu>,
        Peter Zijlstra <peterz@infradead.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Yves-Alexis Perez <corsac@debian.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] PM / Hibernate: allow hibernation with
 PAGE_POISONING_ZERO
Message-ID: <20160912113238.GA30927@amd>
References: <1473410612-6207-1-git-send-email-anisse@astier.eu>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1473410612-6207-1-git-send-email-anisse@astier.eu>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

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@astier.eu>
> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: Laura Abbott <labbott@fedoraproject.org>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Rafael J. Wysocki <rjw@rjwysocki.net>

Looks reasonable to me.

Acked-by: Pavel Machek <pavel@ucw.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
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html