linux-kernel - Re: [PATCH 3/4] mtd: block2mtd: check device size

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Message-Id: <20140129205105.b88b00ea09c07de7014ab1d9@skynet.be>
Date:	Wed, 29 Jan 2014 20:51:05 +0800
From:	Fabian Frederick <fabf@...net.be>
To:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
Cc:	Brian Norris <computersforpeace@...il.com>,
	linux-mtd@...ts.infradead.org, akpm@...ux-foundation.org,
	rdunlap@...radead.org, joern@...ybastard.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] mtd: block2mtd: check device size

On Wed, 29 Jan 2014 07:04:25 -0300
Ezequiel Garcia <ezequiel.garcia@...e-electrons.com> wrote:

> Hi Fabian,
> 
> I saw you sent a v2 for one of the patches on this series,
> but maybe this is worth considering too.
> 
> On Thu, Jan 23, 2014 at 08:53:31PM +0100, Fabian Frederick wrote:
> [..]
> > -/* FIXME: ensure that mtd->size % erase_size == 0 */
> >  static struct block2mtd_dev *add_device(char *devname, int erase_size)
> >  {
> >  	const fmode_t mode = FMODE_READ | FMODE_WRITE | FMODE_EXCL;
> > @@ -250,6 +249,11 @@ static struct block2mtd_dev *add_device(char *devname, int erase_size)
> >  		goto devinit_err1;
> >  	}
> >  
> > +	if ((long)dev->blkdev->bd_inode->i_size % erase_size) {
> > +		pr_err("erasesize muse be a divisor of device size\n");
> > +		goto devinit_err1;
> > +	}
> > +
> 
> Brian: What do you think?
> 
> Fabian: Have you tested this patch? Can you elaborate a bit more about
> the effect it would have, compared to the current behavior?

Hi Ezequiel,

   This patch was tested with the following commands :
   
rmmod block2mtd;modprobe block2mtd block2mtd=/dev/loop0,<erasesize>;dmesg

with both correct and incorrect values.It tries to address the fixme 
comment above the function.
(/* FIXME: ensure that mtd->size % erase_size == 0 */) 
   
   From what I understand, global size must be a multiple of 
erase_size when it comes to any MTD I/O operations. If Brian finds this one 
interesting I can repost it with current error names against l2-mtd.git/next

   AFAICS, current behavior let any value work...
  
 PS : This would need further testing (eg boot command).
 
Regards,
Fabian


> -- 
> Ezequiel García, Free Electrons
> Embedded Linux, Kernel and Android Engineering
> http://free-electrons.com
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