block_device: introduce helper function to check swap or ephemeral device

and move generic function, mappings_prepend_dev() from ec2utils to
block_device

nova/api/ec2/cloud.py

@@ -106,7 +106,7 @@ def _parse_block_device_mapping(bdm):
 
 
 def _properties_get_mappings(properties):
-    return ec2utils.mappings_prepend_dev(properties.get('mappings', []))
+    return block_device.mappings_prepend_dev(properties.get('mappings', []))
 
 
 def _format_block_device_mapping(bdm):
@@ -145,8 +145,7 @@ def _format_mappings(properties, result):
     """Format multiple BlockDeviceMappingItemType"""
     mappings = [{'virtualName': m['virtual'], 'deviceName': m['device']}
                 for m in _properties_get_mappings(properties)
-                if (m['virtual'] == 'swap' or
-                    m['virtual'].startswith('ephemeral'))]
+                if block_device.is_swap_or_ephemeral(m['virtual'])]
 
     block_device_mapping = [_format_block_device_mapping(bdm) for bdm in
                             properties.get('block_device_mapping', [])]
@@ -1447,8 +1446,7 @@ class CloudController(object):
             if virtual_name in ('ami', 'root'):
                 continue
 
-            assert (virtual_name == 'swap' or
-                    virtual_name.startswith('ephemeral'))
+            assert block_device.is_swap_or_ephemeral(virtual_name)
             device_name = m['device']
             if device_name in [b['device_name'] for b in mapping
                                if not b.get('no_device', False)]:

nova/api/ec2/ec2utils.py

@@ -135,13 +135,3 @@ def dict_from_dotted_str(items):
                 args[key] = value
 
     return args
-
-
-def mappings_prepend_dev(mappings):
-    """Prepend '/dev/' to 'device' entry of swap/ephemeral virtual type"""
-    for m in mappings:
-        virtual = m['virtual']
-        if ((virtual == 'swap' or virtual.startswith('ephemeral')) and
-            (not m['device'].startswith('/'))):
-            m['device'] = '/dev/' + m['device']
-    return mappings

nova/block_device.py

@@ -15,6 +15,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import re
+
 
 def properties_root_device_name(properties):
     """get root device name from image meta data.
@@ -33,3 +35,37 @@ def properties_root_device_name(properties):
         root_device_name = properties['root_device_name']
 
     return root_device_name
+
+
+_ephemeral = re.compile('^ephemeral(\d|[1-9]\d+)$')
+
+
+def is_ephemeral(device_name):
+    return _ephemeral.match(device_name)
+
+
+def ephemeral_num(ephemeral_name):
+    assert is_ephemeral(ephemeral_name)
+    return int(_ephemeral.sub('\\1', ephemeral_name))
+
+
+def is_swap_or_ephemeral(device_name):
+    return device_name == 'swap' or is_ephemeral(device_name)
+
+
+def mappings_prepend_dev(mappings):
+    """Prepend '/dev/' to 'device' entry of swap/ephemeral virtual type"""
+    for m in mappings:
+        virtual = m['virtual']
+        if (is_swap_or_ephemeral(virtual) and
+            (not m['device'].startswith('/'))):
+            m['device'] = '/dev/' + m['device']
+    return mappings
+
+
+_dev = re.compile('^/dev/')
+
+
+def strip_dev(device_name):
+    """remove leading '/dev/'"""
+    return _dev.sub('', device_name)

nova/tests/test_api.py

@@ -187,7 +187,7 @@ class Ec2utilsTestCase(test.TestCase):
              'device': '/dev/sdc1'},
             {'virtual': 'ephemeral1',
              'device': '/dev/sdc1'}]
-        self.assertDictListMatch(ec2utils.mappings_prepend_dev(mappings),
+        self.assertDictListMatch(block_device.mappings_prepend_dev(mappings),
                                  expected_result)