iscsi: wipe part table before starting the target

If the local disk has already a partition table, it must be clean up
before the disk is exposed through iscsi. Otherwise this disk partition
can create a conflict during the grub installation.

How reproducible:

1. Inject an image on the root disk, like for example ipxe.usb or ipxe.iso
2. Try to deploy a system on the node using Ironic
3. The node is properly deployed but the grub installation has failed
   with the following error:
     attempting to install grub to a disk with multiple partition labels

A simple sgdisk -Z /dev/vdX is not enough because grub-install will
inspect the disk and will still detect a remaining partition.

This commit makes use of the ironic-lib to do the clean up of the disk.
The additional review Id59fa5a06b9115c0f9afc09aae95daaac97e2fac increase
the amount of data to wipe.

References:
https://bugzilla.redhat.com/show_bug.cgi?id=1310883

Partial-Bug: 1550604

Change-Id: Ie68cb6296c782e904d40f6e9de0faa52ab2af2bf

1 files changed, 13 insertions, 2 deletions

diff --git a/ironic_python_agent/extensions/iscsi.py b/ironic_python_agent/extensions/iscsi.py
index 24292227..288e6a2f 100644
--- a/ironic_python_agent/extensions/iscsi.py
+++ b/ironic_python_agent/extensions/iscsi.py
@@ -16,6 +16,7 @@
 #    under the License.
 
 
+from ironic_lib import disk_utils
 from oslo_concurrency import processutils
 from oslo_log import log
 from oslo_utils import uuidutils
@@ -136,13 +137,23 @@ def clean_up(device):
 
 class ISCSIExtension(base.BaseAgentExtension):
     @base.sync_command('start_iscsi_target')
-    def start_iscsi_target(self, iqn=None):
-        """Expose the disk as an ISCSI target."""
+    def start_iscsi_target(self, iqn=None, wipe_disk_metadata=False):
+        """Expose the disk as an ISCSI target.
+
+        :param wipe_disk_metadata: if the disk metadata should be wiped out
+        before the disk is exposed.
+        """
         # If iqn is not given, generate one
         if iqn is None:
             iqn = 'iqn.2008-10.org.openstack:%s' % uuidutils.generate_uuid()
 
         device = hardware.dispatch_to_managers('get_os_install_device')
+
+        if wipe_disk_metadata:
+            disk_utils.destroy_disk_metadata(
+                device,
+                self.agent.get_node_uuid())
+
         LOG.debug("Starting ISCSI target with iqn %(iqn)s on device "
                   "%(device)s", {'iqn': iqn, 'device': device})