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Date:   Thu, 14 Oct 2021 08:14:31 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Dave Kleikamp <dave.kleikamp@oracle.com>
Cc:     Anton Altaparmakov <anton@tuxera.com>,
        Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
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Subject: Re: don't use ->bd_inode to access the block device size
Message-ID: <202110140813.44C95229@keescook>
References: <20211013051042.1065752-1-hch@lst.de>
 <20211014062844.GA25448@lst.de>
 <3AB8052D-DD45-478B-85F2-BFBEC1C7E9DF@tuxera.com>
 <a5eb3c18-deb2-6539-cc24-57e6d5d3500c@oracle.com>
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On Thu, Oct 14, 2021 at 08:13:59AM -0500, Dave Kleikamp wrote:
> On 10/14/21 4:32AM, Anton Altaparmakov wrote:
> > Hi Christoph,
> > 
> > > On 14 Oct 2021, at 07:28, Christoph Hellwig <hch@lst.de> wrote:
> > > 
> > > On Wed, Oct 13, 2021 at 07:10:13AM +0200, Christoph Hellwig wrote:
> > > > I wondered about adding a helper for looking at the size in byte units
> > > > to avoid the SECTOR_SHIFT shifts in various places.  But given that
> > > > I could not come up with a good name and block devices fundamentally
> > > > work in sector size granularity I decided against that.
> > > 
> > > So it seems like the biggest review feedback is that we should have
> > > such a helper.  I think the bdev_size name is the worst as size does
> > > not imply a particular unit.  bdev_nr_bytes is a little better but I'm
> > > not too happy.  Any other suggestions or strong opinions?
> > 
> > bdev_byte_size() would seem to address your concerns?
> > 
> > bdev_nr_bytes() would work though - it is analogous to bdev_nr_sectors() after all.
> > 
> > No strong opinion here but I do agree with you that bdev_size() is a bad choice for sure.  It is bound to cause bugs down the line when people forget what unit it is in.
> 
> I don't really mind bdev_size since it's analogous to i_size, but
> bdev_nr_bytes seems good to me.

I much prefer bdev_nr_bytes(), as "size" has no units.

-- 
Kees Cook