linux-kernel - Re: [RFC 7/9] selftests: block_seek

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Message-ID: <20240403142323.GG2524049@fedora>
Date: Wed, 3 Apr 2024 10:23:23 -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 7/9] selftests: block_seek_hole: add dm-linear test

On Thu, Mar 28, 2024 at 07:59:14PM -0500, Eric Blake wrote:
> On Thu, Mar 28, 2024 at 04:39:08PM -0400, Stefan Hajnoczi wrote:
> > The dm-linear linear target passes through SEEK_HOLE/SEEK_DATA. Extend
> > the test case to check that the same holes/data are reported as for the
> > underlying file.
> > 
> > Signed-off-by: Stefan Hajnoczi <stefanha@...hat.com>
> > ---
> >  tools/testing/selftests/block_seek_hole/test.py | 16 +++++++++++++++-
> >  1 file changed, 15 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/testing/selftests/block_seek_hole/test.py b/tools/testing/selftests/block_seek_hole/test.py
> > index 4f7c2d01ab3d3..6360b72aee338 100755
> > --- a/tools/testing/selftests/block_seek_hole/test.py
> > +++ b/tools/testing/selftests/block_seek_hole/test.py
> > @@ -45,6 +45,20 @@ def loop_device(file_path):
> >      finally:
> >          run(['losetup', '-d', loop_path])
> >  
> > +@...textmanager
> > +def dm_linear(file_path):
> > +    file_size = os.path.getsize(file_path)
> > +
> > +    with loop_device(file_path) as loop_path:
> > +        dm_name = f'test-{os.getpid()}'
> > +        run(['dmsetup', 'create', dm_name, '--table',
> > +             f'0 {file_size // 512} linear {loop_path} 0'])
> 
> Would it be worth tryiing to create the dm with two copies of
> loop_path concatenated one after the other?  You'd have to do more
> work on expected output (coalescing adjacent data or holes between the
> tail of the first copy and the head of the second), but without that
> in place, I worry that you are missing logic bugs for when there is
> more than one table in the overall dm (as evidenced by my review in
> 4/9).

Yes, I agree that more tests are needed to cover transitions between
adjacent targets.

Stefan

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