utils: Move 'get_bdm_image_metadata' to nova.block_device

The 'nova.block_device' module is essentially a catchall utils-like
module for all things BDM. The 'get_bdm_image_metadata' module, and
closely related 'get_image_metadata_from_volume' both fall into the
category of functions that belong here so move them. This allows us to
clean up tests and, crucially, avoid a circular reference seen when we
want to use proper type hints in the 'nova.virt.driver' module.

  nova.context imports...
  nova.utils, which imports...
  nova.block_device, which imports...
  nova.virt.driver, which tries to import...
  nova.context, causing a circular dependency

Change-Id: I48177d6e93f2ff132d26b53cd682fd24a43a4b31
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

nova/block_device.py

@@ -13,11 +13,12 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import copy
 import re
 
 from oslo_log import log as logging
 from oslo_utils import strutils
-
+from oslo_utils import units
 
 import nova.conf
 from nova import exception
@@ -34,6 +35,12 @@ _DEFAULT_MAPPINGS = {'ami': 'sda1',
                      'root': DEFAULT_ROOT_DEV_NAME,
                      'swap': 'sda3'}
 
+# Image attributes which Cinder stores in volume image metadata
+# as regular properties
+VIM_IMAGE_ATTRIBUTES = (
+    'image_id', 'image_name', 'size', 'checksum',
+    'container_format', 'disk_format', 'min_ram', 'min_disk',
+)
 
 bdm_legacy_fields = set(['device_name', 'delete_on_termination',
                          'virtual_name', 'snapshot_id',
@@ -629,3 +636,86 @@ def get_bdm_swap_list(block_device_mappings):
 def get_bdm_local_disk_num(block_device_mappings):
     return len([bdm for bdm in block_device_mappings
                 if bdm.get('destination_type') == 'local'])
+
+
+def get_bdm_image_metadata(context, image_api, volume_api,
+                           block_device_mapping, legacy_bdm=True):
+    """Attempt to retrive image metadata from a given block_device_mapping.
+
+    If we are booting from a volume, we need to get the volume details from
+    Cinder and make sure we pass the metadata back accordingly.
+
+    :param context: request context
+    :param image_api: Image API
+    :param volume_api: Volume API
+    :param block_device_mapping:
+    :param legacy_bdm:
+    """
+    if not block_device_mapping:
+        return {}
+
+    for bdm in block_device_mapping:
+        if (legacy_bdm and
+                get_device_letter(
+                   bdm.get('device_name', '')) != 'a'):
+            continue
+        elif not legacy_bdm and bdm.get('boot_index') != 0:
+            continue
+
+        volume_id = bdm.get('volume_id')
+        snapshot_id = bdm.get('snapshot_id')
+        if snapshot_id:
+            # NOTE(alaski): A volume snapshot inherits metadata from the
+            # originating volume, but the API does not expose metadata
+            # on the snapshot itself.  So we query the volume for it below.
+            snapshot = volume_api.get_snapshot(context, snapshot_id)
+            volume_id = snapshot['volume_id']
+
+        if bdm.get('image_id'):
+            try:
+                image_id = bdm['image_id']
+                image_meta = image_api.get(context, image_id)
+                return image_meta
+            except Exception:
+                raise exception.InvalidBDMImage(id=image_id)
+        elif volume_id:
+            try:
+                volume = volume_api.get(context, volume_id)
+            except exception.CinderConnectionFailed:
+                raise
+            except Exception:
+                raise exception.InvalidBDMVolume(id=volume_id)
+
+            if not volume.get('bootable', True):
+                raise exception.InvalidBDMVolumeNotBootable(id=volume_id)
+
+            return get_image_metadata_from_volume(volume)
+    return {}
+
+
+def get_image_metadata_from_volume(volume):
+    properties = copy.copy(volume.get('volume_image_metadata', {}))
+    image_meta = {'properties': properties}
+    # Volume size is no longer related to the original image size,
+    # so we take it from the volume directly. Cinder creates
+    # volumes in Gb increments, and stores size in Gb, whereas
+    # glance reports size in bytes. As we're returning glance
+    # metadata here, we need to convert it.
+    image_meta['size'] = volume.get('size', 0) * units.Gi
+    # NOTE(yjiang5): restore the basic attributes
+    # NOTE(mdbooth): These values come from volume_glance_metadata
+    # in cinder. This is a simple key/value table, and all values
+    # are strings. We need to convert them to ints to avoid
+    # unexpected type errors.
+    for attr in VIM_IMAGE_ATTRIBUTES:
+        val = properties.pop(attr, None)
+        if attr in ('min_ram', 'min_disk'):
+            image_meta[attr] = int(val or 0)
+    # NOTE(mriedem): Set the status to 'active' as a really old hack
+    # from when this method was in the compute API class and is
+    # needed for _validate_flavor_image which makes sure the image
+    # is 'active'. For volume-backed servers, if the volume is not
+    # available because the image backing the volume is not active,
+    # then the compute API trying to reserve the volume should fail.
+    image_meta['status'] = 'active'
+    return image_meta