linux-kernel - Re: [PATCH v3 3/3] mtd: block2mtd: Removes PAGE

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Date:	Wed, 26 Nov 2014 08:19:32 -0500 (EST)
From:	Rodrigo Freire <rfreire@...hat.com>
To:	Brian Norris <computersforpeace@...il.com>
Cc:	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Jörn Engel <joern@...fs.org>,
	Felix Fietkau <nbd@...nwrt.org>, dwmw2@...radead.org,
	Herton Krzesinski <hkrzesin@...hat.com>
Subject: Re: [PATCH v3 3/3] mtd: block2mtd: Removes PAGE_MASK as a index to
 partition size

From: "Brian Norris" <computersforpeace@...il.com>
Sent: Wednesday, November 26, 2014 5:21:47 AM
Subject: Re: [PATCH v3 3/3] mtd: block2mtd: Removes PAGE_MASK as a index to
partition size

> On Sun, Nov 09, 2014 at 07:23:12AM -0500, Rodrigo Freire wrote:
> > PAGE_MASK is no longer needed with the new term.

> This isn't too descriptive. What you probably mean is that we assume the
> erase size is always larger than PAGE_SIZE.

> > This patch keeps the device size aligned with the erase_size.
> >
> > Signed-off-by: Felix Fietkau <nbd@...nwrt.org>
> > Signed-off-by: Rodrigo Freire <rfreire@...hat.com>
> > Signed-off-by: Herton Krzesinski <herton@...hat.com>
> > ---
> > V3: Separated on a single patch
> > --- a/drivers/mtd/devices/block2mtd.c 2014-11-07 17:40:58.688747820 -0200
> > +++ b/drivers/mtd/devices/block2mtd.c 2014-11-07 17:41:28.054750893 -0200
> > @@ -291,8 +291,7 @@ static struct block2mtd_dev *add_device(
> > goto err_destroy_mutex;
> >
> > dev->mtd.name = name;
> > -
> > - dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
> > + dev->mtd.size = dev->blkdev->bd_inode->i_size & ~(erase_size - 1);

> You never guaranteed that erase_size is a power of two, so this doesn't
> necessarily mask the way you'd like...

> But also, why is this even necessary? I see that we should already have
> errored out if this was actually significant, since we have above:

> if ((long)dev->blkdev->bd_inode->i_size % erase_size) {
> pr_err("erasesize must be a divisor of device size\n");
> goto err_free_block2mtd;
> }

Hello Brian, and thanks for the review.

Honestly, I'd leave that untouched, but Jörn pointed that it could be a issue at https://lkml.org/lkml/2014/9/9/680

I'd happily let it go without this patch 3, unless Jörg wants to state otherwise.
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