linux-kernel - Re: [PATCH][v6] PM / hibernate: Print the possible panic reason when resuming with inconsistent e820 map

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Date:   Sun, 28 Aug 2016 10:07:10 +0800
From:   Chen Yu <yu.c.chen@...el.com>
To:     Pavel Machek <pavel@....cz>
Cc:     joeyli <jlee@...e.com>, "Rafael J. Wysocki" <rjw@...ysocki.net>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][v6] PM / hibernate: Print the possible panic reason when
 resuming with inconsistent e820 map

Hi,
On Fri, Aug 26, 2016 at 09:56:54PM +0200, Pavel Machek wrote:
> Hi!
> 
> > > > > What's the progress of this patch? Looks already have experts review it.
> > > > > Why this patch didn't accept?
> > > > This patch is a little overkilled, and I have saved another simpler
> > > > version to only check the md5 hash (as people suggested) for it. I can post it later.
> > > > 
> > > 
> > > I am happy to test and review it.
> > >
> > Here it is. As Rafael is on travel, it would be grateful
> > if you can give some advance on this, thanks!
> 
> Better than last one.
> 
> > +		return -ENOMEM;
> > +
> > +	req = ahash_request_alloc(tfm, GFP_ATOMIC);
> 
> what context is this called from? GFP_ATOMIC allocations like to fail...
>
It is in normal process context, OK, I'll change it to GFP_KERNEL.
> > +static int hibernation_e820_check(void *buf)
> > +{
> > +	int ret;
> > +	char result[MD5_HASH_SIZE] = {0};
> > +
> > +	ret = get_e820_md5(&e820_saved, result);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (memcmp(result, buf, MD5_HASH_SIZE))
> > +		e820_conflict = true;
> 
> Passing return value using global variable is ugly. Can you just print
> the warning and kill the box here?
Do you mean get rid of the panic hooker and just print the warning here?
> > +
> 
> > +	/*
> > +	 * A page has been allocated previously to store the hibernation
> > +	 * image header, so we can safely store the md5 result behind
> > +	 * struct restore_data_record, with size of 128 bytes.
> > +	 */
> > +	hibernation_e820_save(addr + sizeof(struct restore_data_record));
> > +
> 
> Please just allocate space in struct restore_data_record . And I don't
> think md5 sum is 128 _bytes_.
>
OK. The md5 sum should be 128 bits thus 16 bytes.

Thanks!
Yu