Do not validate root partition size for whole disk images in iscsi deploy

On whole disk images a root partition is already created and populated, so
validating its size makes no sense. We don't do it for direct deploy.

Change-Id: I7a4114979afb310aeb77f99fbcf09ef7c54862d6
Closes-Bug: #1742451

ironic/drivers/modules/iscsi_deploy.py

@@ -88,10 +88,17 @@ def _save_disk_layout(node, i_info):
 def check_image_size(task):
     """Check if the requested image is larger than the root partition size.
 
+    Does nothing for whole-disk images.
+
     :param task: a TaskManager instance containing the node to act on.
     :raises: InstanceDeployFailure if size of the image is greater than root
         partition.
     """
+    if task.node.driver_internal_info['is_whole_disk_image']:
+        # The root partition is already created and populated, no use
+        # validating its size
+        return
+
     i_info = deploy_utils.parse_instance_info(task.node)
     image_path = _get_image_file_path(task.node.uuid)
     image_mb = disk_utils.get_image_mb(image_path)

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

@@ -117,6 +117,17 @@ class IscsiDeployMethodsTestCase(db_base.DbTestCase):
             get_image_mb_mock.assert_called_once_with(
                 iscsi_deploy._get_image_file_path(task.node.uuid))
 
+    @mock.patch.object(disk_utils, 'get_image_mb', autospec=True)
+    def test_check_image_size_whole_disk_image(self, get_image_mb_mock):
+        get_image_mb_mock.return_value = 1025
+        with task_manager.acquire(self.context, self.node.uuid,
+                                  shared=False) as task:
+            task.node.instance_info['root_gb'] = 1
+            task.node.driver_internal_info['is_whole_disk_image'] = True
+            # No error for whole disk images
+            iscsi_deploy.check_image_size(task)
+            self.assertFalse(get_image_mb_mock.called)
+
     @mock.patch.object(disk_utils, 'get_image_mb', autospec=True)
     def test_check_image_size_fails(self, get_image_mb_mock):
         get_image_mb_mock.return_value = 1025

releasenotes/notes/iscsi-whole-disk-cd464d589d029b01.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    No longer validates requested root partition size for whole-disk images
+    using ``iscsi`` deploy interface, see `bug 1742451
+    <https://bugs.launchpad.net/ironic/+bug/1742451>`_ for details.