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

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Date:	Tue, 25 Nov 2014 23:21:47 -0800
From:	Brian Norris <computersforpeace@...il.com>
To:	Rodrigo Freire <rfreire@...hat.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

On Sun, Nov 09, 2014 at 07:23:12AM -0500, Rodrigo Freire wrote:
> From: Felix Fietkau <nbd@...nwrt.org>
> 
> mtd: block2mtd: Removes PAGE_MASK as a index to partition size

You don't need to repeat the subject here.

> 
> 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;
	}

>  	dev->mtd.erasesize = erase_size;
>  	dev->mtd.writesize = 1;
>  	dev->mtd.writebufsize = PAGE_SIZE;

Brian
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