Message-ID: <54EC344F.3050709@openwrt.org>
Date: Tue, 24 Feb 2015 21:20:31 +1300
From: Felix Fietkau <nbd@openwrt.org>
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.4.0
MIME-Version: 1.0
To: Brian Norris <computersforpeace@gmail.com>,
        Rodrigo Freire <rfreire@redhat.com>
CC: linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
        =?windows-1252?Q?J=F6rn_Engel?= <joern@logfs.org>, dwmw2@infradead.org,
        Herton Krzesinski <hkrzesin@redhat.com>
Subject: Re: [PATCH v3 3/3] mtd: block2mtd: Removes PAGE_MASK as a index to
 partition size
References: <371358190.34795877.1410204429882.JavaMail.zimbra@redhat.com> <1444809468.34812041.1410206680931.JavaMail.zimbra@redhat.com> <20140909170231.GA14429@logfs.org> <1807144344.40128259.1410985683342.JavaMail.zimbra@redhat.com> <20141105202303.GN23619@ld-irv-0074> <2086372266.7454667.1415535533979.JavaMail.zimbra@redhat.com> <1874445287.7454806.1415535792984.JavaMail.zimbra@redhat.com> <20141126072147.GO3212@norris-Latitude-E6410> <1417070032.4547583.1417007972343.JavaMail.zimbra@redhat.com> <20150224080752.GF24441@norris-Latitude-E6410>
In-Reply-To: <20150224080752.GF24441@norris-Latitude-E6410>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2703
Lines: 64

On 2015-02-24 21:07, Brian Norris wrote:
> On Wed, Nov 26, 2014 at 08:19:32AM -0500, Rodrigo Freire wrote:
>> From: "Brian Norris" <computersforpeace@gmail.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@openwrt.org>
>> > > Signed-off-by: Rodrigo Freire <rfreire@redhat.com>
>> > > Signed-off-by: Herton Krzesinski <herton@redhat.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 J?rn 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 J?rg wants to state otherwise.
> 
> OK let's drop this patch from the series. At best, we could just do
> something like this instead:
> 
> -	dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
> +	dev->mtd.size = dev->blkdev->bd_inode->i_size;
> 
> But that's really just an unnecessary change.
If I remember correctly, it was problematic to have a dev->mtd.size
value which is not a multiple of the erase size. I think that was the
reason for patch 3.

- Felix
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/