linux-kernel - RE: [PATCH 3/3] PM / hibernate: Remove the restriction when checking memory size before/after hibernation

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Date:	Tue, 1 Sep 2015 09:54:31 +0000
From:	"Chen, Yu C" <yu.c.chen@...el.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	"pavel@....cz" <pavel@....cz>, "hpa@...or.com" <hpa@...or.com>,
	"Brown, Len" <len.brown@...el.com>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"joeyli.kernel@...il.com" <joeyli.kernel@...il.com>,
	"Zhang, Rui" <rui.zhang@...el.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 3/3] PM / hibernate: Remove the restriction when
 checking memory size before/after hibernation

Hi Ingo, thanks for your review/suggestion,

> -----Original Message-----
> From: Ingo Molnar [mailto:mingo.kernel.org@...il.com] On Behalf Of Ingo
> Molnar
> Sent: Friday, August 28, 2015 1:38 PM
> To: Chen, Yu C
> Cc: tglx@...utronix.de; mingo@...hat.com; rjw@...ysocki.net;
> pavel@....cz; hpa@...or.com; Brown, Len; yinghai@...nel.org;
> joeyli.kernel@...il.com; Zhang, Rui; linux-pm@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH 3/3] PM / hibernate: Remove the restriction when
> checking memory size before/after hibernation
> 
> 
> * Chen Yu <yu.c.chen@...el.com> wrote:
> > +	/*
> > +	 * No need to check num_physpages with get_num_physpages
> > +	 * as we did before(please refer to git log), because
> > +	 * is_nosave_page will ensure that each page is safe
> > +	 * to be restored.
> > +	 */
> >  	if (reason) {
> >  		printk(KERN_ERR "PM: Image mismatch: %s\n", reason);
> >  		return -EPERM;
> 
> No, this removes a useful sanity check that protects against data corruption.
> 
> If you want to relax it then you should add code that checks whether the
> before/after memory image is truly a superset of each other, and warn and
> deny the hibernation in any other case. (For example when RAM got
> removed or moved.)
> 
OK, I've sent out another patch based on pfn_mapped checking.thanks

Best Regards,
Yu
> Thanks,
> 
> 	Ingo
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