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

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Date:   Fri, 26 Aug 2016 21:56:54 +0200
From:   Pavel Machek <pavel@....cz>
To:     Chen Yu <yu.c.chen@...el.com>
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!

> > > > 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.

> +#ifdef CONFIG_HIBERNATION_CHECK_E820
> +#define MD5_HASH_SIZE 128
> +
> +/**
> + *	get_e820_md5 - calculate md5 according to struct e820map
> + *
> + *	@map: the e820 map to be calculated
> + *	@buf: the md5 result to be stored to
> + */
> +static int get_e820_md5(struct e820map *map, void *buf)
> +{
> +	struct scatterlist sg;
> +	struct crypto_ahash *tfm;
> +	struct ahash_request *req;
> +	int ret = 0;
> +
> +	tfm = crypto_alloc_ahash("md5", 0, CRYPTO_ALG_ASYNC);
> +	if (IS_ERR(tfm))
> +		return -ENOMEM;
> +
> +	req = ahash_request_alloc(tfm, GFP_ATOMIC);

what context is this called from? GFP_ATOMIC allocations like to fail...

> +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?
> +

> +	/*
> +	 * 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_.

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