Re: [Libguestfs] [PATCH nbdkit 1/2] tests/test-python-plugin.py: Allow test to use large disks

On Wed, Dec 22, 2021 at 12:36 AM Richard W.M. Jones <rjones(a)redhat.com&gt; wrote: > > On Tue, Dec 21, 2021 at 10:25:35PM +0000, Richard W.M. Jones wrote: > > On Wed, Dec 22, 2021 at 12:21:25AM +0200, Nir Soffer wrote: > > > It would be help also if we can test extents argument, currently the > > > plugin ignores the argument so we did not detect the issue with the > > > wrong format string. > > > > OK, I'll take a look. > > I see - the plugin function is defined just to return the extents sent > in (for testing): > > def extents(h, count, offset, flags): > return cfg.get('extents', []) > > This means we don't test the parameters. However to test those > realistically I suppose we would really need to support sparse disks > in this test plugin, which seems quite tricky. I think what can work is this: - pass the actual extents to the plugin For example empty sparse file: extents = [(0, 10 * GiB, nbdkit.EXTENT_ZERO)] Now when we request: extents(4*GB -1, 0, 0) The plugin can return: return [(0, count, nbdkit.EXTENT_ZERO)]

The logic to return extents from the existing list is a little tricky. I have similar code in a memory backend for imageio (in review): https://github.com/oVirt/ovirt-imageio/pull/7/commits/9068f84c96f1239d841... And this is also the code for getting extents from imageio, posted here: https://listman.redhat.com/archives/libguestfs/2021-December/msg00197.html