linux-kernel - Re: [RFC 5/9] selftests: block_seek

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Message-ID: <20240328223208.GA2373362@fedora>
Date: Thu, 28 Mar 2024 18:32:08 -0400
From: Stefan Hajnoczi <stefanha@...hat.com>
To: Eric Blake <eblake@...hat.com>
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
	Alasdair Kergon <agk@...hat.com>,
	Mikulas Patocka <mpatocka@...hat.com>, dm-devel@...ts.linux.dev,
	David Teigland <teigland@...hat.com>,
	Mike Snitzer <snitzer@...nel.org>, Jens Axboe <axboe@...nel.dk>,
	Christoph Hellwig <hch@....de>, Joe Thornber <ejt@...hat.com>
Subject: Re: [RFC 5/9] selftests: block_seek_hole: add dm-zero test

On Thu, Mar 28, 2024 at 05:19:26PM -0500, Eric Blake wrote:
> On Thu, Mar 28, 2024 at 04:39:06PM -0400, Stefan Hajnoczi wrote:
> > Signed-off-by: Stefan Hajnoczi <stefanha@...hat.com>
> > ---
> >  .../selftests/block_seek_hole/Makefile        |  2 +-
> >  .../testing/selftests/block_seek_hole/config  |  2 ++
> >  .../selftests/block_seek_hole/dm_zero.sh      | 31 +++++++++++++++++++
> >  3 files changed, 34 insertions(+), 1 deletion(-)
> >  create mode 100755 tools/testing/selftests/block_seek_hole/dm_zero.sh
> > 
> 
> > +++ b/tools/testing/selftests/block_seek_hole/dm_zero.sh
> > @@ -0,0 +1,31 @@
> > +#!/bin/sh
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +#
> > +# dm_zero.sh
> > +#
> > +# Test that dm-zero reports data because it does not have a custom
> > +# SEEK_HOLE/SEEK_DATA implementation.
> 
> Why not?  Wouldn't it make more sense to have dm-zero report the
> entire device as a hole (that is, an in-range SEEK_HOLE always returns
> the same offset, while an in-range SEEK_DATA returns the device size)?

Yes, dm-zero could report a hole. I just added this test to verify that
targets that do not implement seek_hole_data() work and the dm-zero
target was convenient for testing.

Stefan

> 
> -- 
> Eric Blake, Principal Software Engineer
> Red Hat, Inc.
> Virtualization:  qemu.org | libguestfs.org
> 

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