fix unmounting of LXC containers

There were two issues here.

1. There was a global object stored for all instances,
thus the last mounted instance was always unmounted.

2. Even if there was only a single LXC instance in use,
the global object would be lost on restart of Nova.

Therefore we reset the internal state for the mount object,
by passing in the mount point to destroy_container(),
and querying the device in use for that mount point.

Fixes bug: 971621
Change-Id: I5442442f00d93f5e8b82f492d62918419db5cd3b

nova/tests/test_virt.py

@@ -15,9 +15,12 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import os
+
 from nova import exception
 from nova import flags
 from nova import test
+from nova import utils
 from nova.virt.disk import api as disk_api
 from nova.virt import driver
 
@@ -86,6 +89,16 @@ class TestVirtDriver(test.TestCase):
 
 
 class TestVirtDisk(test.TestCase):
+    def setUp(self):
+        super(TestVirtDisk, self).setUp()
+        self.executes = []
+
+        def fake_execute(*cmd, **kwargs):
+            self.executes.append(cmd)
+            return None, None
+
+        self.stubs.Set(utils, 'execute', fake_execute)
+
     def test_check_safe_path(self):
         ret = disk_api._join_and_check_path_within_fs('/foo', 'etc',
                                                       'something.conf')
@@ -101,3 +114,54 @@ class TestVirtDisk(test.TestCase):
                           disk_api._inject_file_into_fs,
                           '/tmp', '/etc/../../../../etc/passwd',
                           'hax')
+
+    def test_lxc_destroy_container(self):
+
+        def proc_mounts(self, mount_point):
+            mount_points = {
+                '/mnt/loop/nopart': '/dev/loop0',
+                '/mnt/loop/part': '/dev/mapper/loop0p1',
+                '/mnt/nbd/nopart': '/dev/nbd15',
+                '/mnt/nbd/part': '/dev/mapper/nbd15p1',
+                '/mnt/guestfs': 'guestmount',
+            }
+            return mount_points[mount_point]
+
+        self.stubs.Set(os.path, 'exists', lambda _: True)
+        self.stubs.Set(disk_api._DiskImage, '_device_for_path', proc_mounts)
+        expected_commands = []
+
+        disk_api.destroy_container('/mnt/loop/nopart')
+        expected_commands += [
+                              ('umount', '/dev/loop0'),
+                              ('losetup', '--detach', '/dev/loop0'),
+                             ]
+
+        disk_api.destroy_container('/mnt/loop/part')
+        expected_commands += [
+                              ('umount', '/dev/mapper/loop0p1'),
+                              ('kpartx', '-d', '/dev/loop0'),
+                              ('losetup', '--detach', '/dev/loop0'),
+                             ]
+
+        disk_api.destroy_container('/mnt/nbd/nopart')
+        expected_commands += [
+                              ('umount', '/dev/nbd15'),
+                              ('qemu-nbd', '-d', '/dev/nbd15'),
+                             ]
+
+        disk_api.destroy_container('/mnt/nbd/part')
+        expected_commands += [
+                              ('umount', '/dev/mapper/nbd15p1'),
+                              ('kpartx', '-d', '/dev/nbd15'),
+                              ('qemu-nbd', '-d', '/dev/nbd15'),
+                             ]
+
+        disk_api.destroy_container('/mnt/guestfs')
+        expected_commands += [
+                              ('fusermount', '-u', '/mnt/guestfs'),
+                             ]
+        # It's not worth trying to match the last timeout command
+        self.executes.pop()
+
+        self.assertEqual(self.executes, expected_commands)