Re: [PATCH 2/2] iotests/169: Test source cont with backing bmap

[Eric Blake]

On 7/30/20 7:02 AM, Max Reitz wrote:
> Test migrating from a VM with a persistent bitmap in the backing chain,
> and then continuing that VM after the migration

Indeed, the more our iotest is like what libvirt actually does, the 
better we protect ourselves from future bugs in this area.

> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>   tests/qemu-iotests/169     | 64 +++++++++++++++++++++++++++++++++++++-
>   tests/qemu-iotests/169.out |  4 +--
>   2 files changed, 65 insertions(+), 3 deletions(-)

> +class TestDirtyBitmapBackingMigration(iotests.QMPTestCase):
> +    def setUp(self):
> +        qemu_img_create('-f', iotests.imgfmt, base_a, size)
> +        qemu_img_create('-f', iotests.imgfmt, '-F', iotests.imgfmt,
> +                        '-b', base_a, disk_a, size)
> +
> +        for f in (disk_a, base_a):
> +            qemu_img('bitmap', '--add', f, 'bmap0')

I'm so glad to see 'qemu-img bitmap' getting some use :)

> +
> +        blockdev = {
> +            'node-name': 'node0',
> +            'driver': iotests.imgfmt,
> +            'file': {
> +                'driver': 'file',
> +                'filename': disk_a
> +            },
> +            'backing': {
> +                'node-name': 'node0-base',
> +                'driver': iotests.imgfmt,
> +                'file': {
> +                    'driver': 'file',
> +                    'filename': base_a
> +                }
> +            }
> +        }
> +
> +        self.vm = iotests.VM()
> +        self.vm.launch()
> +
> +        result = self.vm.qmp('blockdev-add', **blockdev)
> +        self.assert_qmp(result, 'return', {})
> +
> +        # Check that the bitmaps are there
> +        for node in self.vm.qmp('query-named-block-nodes', 
> flat=True)['return']:
> +            if 'node0' in node['node-name']:

This caught me on the first read, before I realized it was a clever way 
to test both 'node0' and 'node0-base'.

> +                self.assert_qmp(node, 'dirty-bitmaps[0]/name', 'bmap0')
> +
> +        caps = [{'capability': 'events', 'state': True}]
> +        result = self.vm.qmp('migrate-set-capabilities', capabilities=caps)
> +        self.assert_qmp(result, 'return', {})
> +
> +    def tearDown(self):
> +        self.vm.shutdown()
> +        for f in (disk_a, base_a):
> +            os.remove(f)
> +
> +    def test_cont_on_source(self):
> +        """
> +        Continue the source after migration.
> +        """
> +        result = self.vm.qmp('migrate', uri=f'exec: cat > /dev/null')
> +        self.assert_qmp(result, 'return', {})
> +
> +        with Timeout(10, 'Migration timeout'):
> +            self.vm.wait_migration('postmigrate')
> +
> +        result = self.vm.qmp('cont')
> +        self.assert_qmp(result, 'return', {})
> +

Reviewed-by: Eric Blake <eblake@redhat.com>

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org