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

[Chen, Yu C]

Hi Ingo, thanks for your review/suggestion,

> -----Original Message-----
> From: Ingo Molnar [mailto:mingo.kernel.org@xxxxxxxxx] On Behalf Of Ingo
> Molnar
> Sent: Friday, August 28, 2015 1:38 PM
> To: Chen, Yu C
> Cc: tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; rjw@xxxxxxxxxxxxx;
> pavel@xxxxxx; hpa@xxxxxxxxx; Brown, Len; yinghai@xxxxxxxxxx;
> joeyli.kernel@xxxxxxxxx; Zhang, Rui; linux-pm@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH 3/3] PM / hibernate: Remove the restriction when
> checking memory size before/after hibernation
> 
> 
> * Chen Yu <yu.c.chen@xxxxxxxxx> 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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