Merge ~mwhudson/curtin:disk_handler-empty-vtoc into curtin:master

[Michael Hudson-Doyle]

create an empty vtoc in disk_handler

Another merge proposal I have uses fdasd to get the block and track size
when partitioning a disk. But the wiping disk_handler can do can do
enough damage to stop fdasd working at all. Putting an empty vtoc onto
the disk allows fdasd to report the sizes when needed.

[Server Team CI bot (server-team-bot)]

FAILED: Continuous integration, rev:8d535e1368d3035539c81368556c777db0723bd6

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review: Needs Fixing (continuous-integration)

[Dimitri John Ledkov (xnox)]

normally no dasd drives ever are without a vtoc. However, one can try very hard to destory them, or actually come up for the first time in the z/vm environment. In such cases, it's near impossible to operate on the dasd in any sensible manner, thus creating vtoc is the only right way forward. After doing that, it becomes much easier to add/remove partitions or wipe the device (in cutin terms).

review: Approve

[Server Team CI bot (server-team-bot)]

review: Approve (continuous-integration)

diff --git a/curtin/commands/block_meta.py b/curtin/commands/block_meta.py
index eada650..874ccbb 100644
--- a/curtin/commands/block_meta.py
+++ b/curtin/commands/block_meta.py
@@ -611,8 +611,7 @@ def disk_handler(info, storage_config):
             elif ptable in _dos_names:
                 util.subp(["parted", disk, "--script", "mklabel", "msdos"])
             elif ptable == "vtoc":
-                # ignore dasd partition tables
-                pass
+                util.subp(["fdasd", "-c", "/dev/null", disk])
         holders = clear_holders.get_holders(disk)
         if len(holders) > 0:
             LOG.info('Detected block holders on disk %s: %s', disk, holders)
diff --git a/tests/unittests/test_commands_block_meta.py b/tests/unittests/test_commands_block_meta.py
index 98be573..ffec434 100644
--- a/tests/unittests/test_commands_block_meta.py
+++ b/tests/unittests/test_commands_block_meta.py
@@ -1294,6 +1294,17 @@ class TestDiskHandler(CiTestCase):
         m_getpath.assert_called_with(info['id'], storage_config)
         m_block.get_part_table_type.assert_called_with(disk_path)
 
+    @patch('curtin.commands.block_meta.util.subp')
+    @patch('curtin.commands.block_meta.clear_holders.get_holders')
+    @patch('curtin.commands.block_meta.get_path_to_storage_volume')
+    def test_disk_handler_calls_fdasd_for_vtoc(self, m_getpath,
+                                               m_get_holders, m_subp):
+        info = {'ptable': 'vtoc', 'type': 'disk', 'id': 'disk-foobar'}
+        path = m_getpath.return_value = self.random_string()
+        m_get_holders.return_value = []
+        block_meta.disk_handler(info, OrderedDict())
+        m_subp.assert_called_once_with(['fdasd', '-c', '/dev/null', path])
+
 
 class TestLvmVolgroupHandler(CiTestCase):