Add support for LXC volumes.

This introduces volume support for LXC containers in Nova.
The way that this works is that when a device is attached to an
LXC container is that, the xml is parsed to find out which device to
connect to the LXC container, binds the device to the LXC container,
and allow the device through cgroups.

This bug fixes LP: #924601.

Change-Id: I00b41426ae8354b3cd4212655ecb48319a63aa9b
Signed-off-by: Chuck Short <chuck.short@canonical.com>

nova/tests/test_libvirt.py

@@ -195,6 +195,27 @@ def test_libvirt_rbd_driver(self):
         libvirt_driver.disconnect_volume(connection_info, mount_device)
         connection_info = vol_driver.terminate_connection(vol, self.connr)
 
+    def test_libvirt_lxc_volume(self):
+        self.stubs.Set(os.path, 'exists', lambda x: True)
+        vol_driver = volume_driver.ISCSIDriver()
+        libvirt_driver = volume.LibvirtISCSIVolumeDriver(self.fake_conn)
+        location = '10.0.2.15:3260'
+        name = 'volume-00000001'
+        iqn = 'iqn.2010-10.org.openstack:%s' % name
+        vol = {'id': 1,
+               'name': name,
+               'provider_auth': None,
+               'provider_location': '%s,fake %s' % (location, iqn)}
+        connection_info = vol_driver.initialize_connection(vol, self.connr)
+        mount_device = "vde"
+        xml = libvirt_driver.connect_volume(connection_info, mount_device)
+        tree = xml_to_tree(xml)
+        dev_str = '/dev/disk/by-path/ip-%s-iscsi-%s-lun-0' % (location, iqn)
+        self.assertEqual(tree.get('type'), 'block')
+        self.assertEqual(tree.find('./source').get('dev'), dev_str)
+        libvirt_driver.disconnect_volume(connection_info, mount_device)
+        connection_info = vol_driver.terminate_connection(vol, self.connr)
+
 
 class CacheConcurrencyTestCase(test.TestCase):
     def setUp(self):

nova/virt/disk/api.py

@@ -106,6 +106,26 @@ def extend(image, size):
     utils.execute('resize2fs', image, check_exit_code=False)
 
 
+def bind(src, target, instance_name):
+    """Bind device to a filesytem"""
+    if src:
+        utils.execute('touch', target, run_as_root=True)
+        utils.execute('mount', '-o', 'bind', src, target,
+                run_as_root=True)
+        s = os.stat(src)
+        cgroup_info = "c %s:%s rwm" % (os.major(s.st_rdev),
+                                       os.minor(s.st_rdev))
+        cgroups_path = \
+            "/sys/fs/cgroup/devices/sysdefault/libvirt/lxc/%s/devices.allow" \
+            % instance_name
+        utils.execute('echo', '>', cgroup_info, cgroups_path, run_as_root=True)
+
+
+def unbind(target):
+    if target:
+        utils.execute('umount', target, run_as_root=True)
+
+
 class _DiskImage(object):
     """Provide operations on a disk image file."""
 

nova/virt/libvirt/connection.py

@@ -449,7 +449,11 @@ def attach_volume(self, connection_info, instance_name, mountpoint):
         xml = self.volume_driver_method('connect_volume',
                                         connection_info,
                                         mount_device)
-        virt_dom.attachDevice(xml)
+
+        if FLAGS.libvirt_type == 'lxc':
+            self._attach_lxc_volume(xml, virt_dom, instance_name)
+        else:
+            virt_dom.attachDevice(xml)
 
     @staticmethod
     def _get_disk_xml(xml, device):
@@ -476,12 +480,64 @@ def detach_volume(self, connection_info, instance_name, mountpoint):
             xml = self._get_disk_xml(virt_dom.XMLDesc(0), mount_device)
             if not xml:
                 raise exception.DiskNotFound(location=mount_device)
-            virt_dom.detachDevice(xml)
+            if FLAGS.libvirt_type == 'lxc':
+                self._detach_lxc_volume(xml, vort_dom, instance_name)
+            else:
+                virt_dom.detachDevice(xml)
         finally:
             self.volume_driver_method('disconnect_volume',
                                       connection_info,
                                       mount_device)
 
+    @exception.wrap_exception()
+    def _attach_lxc_volume(self, xml, virt_dom, instance_name):
+        LOG.info(_('attaching LXC block device'))
+
+        lxc_container_root = self.get_lxc_container_root(virt_dom)
+        lxc_host_volume = self.get_lxc_host_device(xml)
+        lxc_container_device = self.get_lxc_container_target(xml)
+        lxc_container_target = "%s/%s" % (lxc_container_root,
+                                          lxc_container_device)
+
+        if lxc_container_target:
+            disk.bind(lxc_host_volume, lxc_container_target, instance_name)
+
+    @exception.wrap_exception()
+    def _detach_lxc_volume(self, xml, virt_dom, instance_name):
+        LOG.info(_('detaching LXC block device'))
+
+        lxc_container_root = self.get_lxc_container_root(virt_dom)
+        lxc_host_volume = self.get_lxc_host_device(xml)
+        lxc_container_device = self.get_lxc_container_target(xml)
+        lxc_container_target = "%s/%s" % (lxc_container_root,
+                                          lxc_container_device)
+
+        if lxc_container_target:
+            disk.unbind(lxc_container_target)
+
+    @staticmethod
+    def get_lxc_container_root(virt_dom):
+        xml = virt_dom.XMLDesc(0)
+        doc = ElementTree.fromstring(xml)
+        filesystem_block = doc.findall('./devices/filesystem')
+        for cnt, filesystem_nodes in enumerate(filesystem_block):
+            return filesystem_nodes[cnt].get('dir')
+
+    @staticmethod
+    def get_lxc_host_device(xml):
+        dom = minidom.parseString(xml)
+
+        for device in dom.getElementsByTagName('source'):
+            return device.getAttribute('dev')
+
+    @staticmethod
+    def get_lxc_container_target(xml):
+        dom = minidom.parseString(xml)
+
+        for device in dom.getElementsByTagName('target'):
+            filesystem = device.getAttribute('dev')
+            return 'dev/%s' % filesystem
+
     @exception.wrap_exception()
     def snapshot(self, context, instance, image_href):
         """Create snapshot from a running VM instance.