Fix disk label to account for UEFI

Previously disk labels would not be populated if not explicitly
set by an API user, which lead to a dangerous possible case,
which sometimes could work, but was ultimately wrong to
setup a UEFI booting machine with a BIOS MBR partition table.

Not all systems support this, but UEFI systems are supposed to
support GPT partition tables.

We now fallback if no explicit override is set and assume GPT
if the machine is set to UEFI mode.

Change-Id: I001d8c6ee3b1d6c466c71ea5179bdbca9bdd692d

ironic/drivers/modules/deploy_utils.py

@@ -356,7 +356,13 @@ def get_disk_label(node):
     :returns: the disk label or None if no disk label was specified.
     """
     capabilities = utils.parse_instance_info_capabilities(node)
-    return capabilities.get('disk_label')
+    label = capabilities.get('disk_label')
+    # NOTE(TheJulia): If the node is UEFI based, we should likely just default
+    # the table type to gpt as otherwise we rely upon the user to supply the
+    # right information, and for UEFI mode bios may work, but is wrong.
+    if label is None and boot_mode_utils.get_boot_mode(node) == 'uefi':
+        label = 'gpt'
+    return label
 
 
 def get_pxe_boot_file(node):

ironic/tests/unit/drivers/modules/test_deploy_utils.py

@@ -1039,6 +1039,20 @@ class ParseInstanceInfoCapabilitiesTestCase(tests_base.TestCase):
         result = utils.get_disk_label(self.node)
         self.assertEqual('gpt', result)
 
+    def test_get_disk_label_nothing_set(self):
+        inst_info = {'capabilities': {'cat': 'meows'}}
+        self.node.instance_info = inst_info
+        result = utils.get_disk_label(self.node)
+        self.assertIsNone(result)
+
+    def test_get_disk_label_uefi_mode(self):
+        inst_info = {'capabilities': {'cat': 'meows'}}
+        properties = {'capabilities': 'boot_mode:uefi'}
+        self.node.instance_info = inst_info
+        self.node.properties = properties
+        result = utils.get_disk_label(self.node)
+        self.assertEqual('gpt', result)
+
 
 class TrySetBootDeviceTestCase(db_base.DbTestCase):
 

releasenotes/notes/assume-gpt-for-uefi-boot-mode-8f9c77721394459a.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Fixes the logic which determines the partition table type to utilize with
+    partition images account for the boot mode of the machine. If no value is
+    set by the API user, Ironic now correctly defaults to GPT if the node
+    has been set in UEFI mode.