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From: Andreas Dilger <adilger@clusterfs.com>
Date: Wed, 25 Sep 2002 12:03:55 -0600
To: tytso@mit.edu
Cc: torvalds@transmeta.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] loop device broken in 2.5.38
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On Sep 25, 2002  13:35 -0400, tytso@mit.edu wrote:
> The loop device driver was broken in 2.5.38 when it was converted over
> to use gendisk.  I discovered this while doing final regression testing
> on the ext3 htree code.
> 
> The problem is that figure_loop_size() is setting the capacity of the
> loop device in kilobytes (because that's what compute_loop_size()
> returns), but set_capacity() expects the size in 512 byte sectors.
> 
> I've enclosed a patch which fixes the problem, as well as simplifying
> the code by eliminating compute_loop_size(), since it is a static
> function is only used once by figure_loop_size().

Is there a historic reason why we pre-compute and store the loop device
size instead of re-calculating it each time we do a BLKGETSZ ioctl?
Re-calculating it each time allows you to increase the size of the
backing file if needed while it is in use, and I don't think we actually
get the size of the loop device very often, so it is not a big deal,
especially given the simple calculation needed.

Cheers, Andreas
--
Andreas Dilger
http://www-mddsp.enel.ucalgary.ca/People/adilger/
http://sourceforge.net/projects/ext2resize/