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)

nova/virt/disk/api.py

@@ -173,6 +173,8 @@ def unbind(target):
 class _DiskImage(object):
     """Provide operations on a disk image file."""
 
+    tmp_prefix = 'openstack-disk-mount-tmp'
+
     def __init__(self, image, partition=None, use_cow=False, mount_dir=None):
         # These passed to each mounter
         self.image = image
@@ -194,18 +196,50 @@ class _DiskImage(object):
             msg = _('no capable image handler configured')
             raise exception.NovaException(msg)
 
+        if mount_dir:
+            # Note the os.path.ismount() shortcut doesn't
+            # work with libguestfs due to permissions issues.
+            device = self._device_for_path(mount_dir)
+            if device:
+                self._reset(device)
+
+    @staticmethod
+    def _device_for_path(path):
+        device = None
+        with open("/proc/mounts", 'r') as ifp:
+            for line in ifp:
+                fields = line.split()
+                if fields[1] == path:
+                    device = fields[0]
+                    break
+        return device
+
+    def _reset(self, device):
+        """Reset internal state for a previously mounted directory."""
+        mounter_cls = self._handler_class(device=device)
+        mounter = mounter_cls(image=self.image,
+                              partition=self.partition,
+                              mount_dir=self.mount_dir,
+                              device=device)
+        self._mounter = mounter
+
+        mount_name = os.path.basename(self.mount_dir or '')
+        self._mkdir = mount_name.startswith(self.tmp_prefix)
+
     @property
     def errors(self):
         """Return the collated errors from all operations."""
         return '\n--\n'.join([''] + self._errors)
 
     @staticmethod
-    def _handler_class(mode):
+    def _handler_class(mode=None, device=None):
-        """Look up the appropriate class to use based on MODE."""
+        """Look up the appropriate class to use based on MODE or DEVICE."""
         for cls in (loop.Mount, nbd.Mount, guestfs.Mount):
-            if cls.mode == mode:
+            if mode and cls.mode == mode:
                 return cls
-        msg = _("unknown disk image handler: %s") % mode
+            elif device and cls.device_id_string in device:
+                return cls
+        msg = _("no disk image handler for: %s") % mode or device
         raise exception.NovaException(msg)
 
     def mount(self):
@@ -220,7 +254,7 @@ class _DiskImage(object):
             raise exception.NovaException(_('image already mounted'))
 
         if not self.mount_dir:
-            self.mount_dir = tempfile.mkdtemp()
+            self.mount_dir = tempfile.mkdtemp(prefix=self.tmp_prefix)
             self._mkdir = True
 
         try:
@@ -275,18 +309,14 @@ def inject_data(image,
         raise exception.NovaException(img.errors)
 
 
-def setup_container(image, container_dir=None, use_cow=False):
+def setup_container(image, container_dir, use_cow=False):
     """Setup the LXC container.
 
     It will mount the loopback image to the container directory in order
     to create the root filesystem for the container.
-
-    LXC does not support qcow2 images yet.
     """
     img = _DiskImage(image=image, use_cow=use_cow, mount_dir=container_dir)
-    if img.mount():
+    if not img.mount():
-        return img
-    else:
         LOG.error(_("Failed to mount container filesystem '%(image)s' "
                     "on '%(target)s': %(errors)s") %
                   {"image": img, "target": container_dir,
@@ -294,17 +324,15 @@ def setup_container(image, container_dir=None, use_cow=False):
         raise exception.NovaException(img.errors)
 
 
-def destroy_container(img):
+def destroy_container(container_dir):
     """Destroy the container once it terminates.
 
     It will umount the container that is mounted,
     and delete any  linked devices.
-
-    LXC does not support qcow2 images yet.
     """
     try:
-        if img:
+        img = _DiskImage(image=None, mount_dir=container_dir)
-            img.umount()
+        img.umount()
     except Exception, exn:
         LOG.exception(_('Failed to unmount container filesystem: %s'), exn)
 

nova/virt/disk/guestfs.py

@@ -25,6 +25,7 @@ from nova.virt.disk import mount
 class Mount(mount.Mount):
     """libguestfs support for arbitrary images."""
     mode = 'guestfs'
+    device_id_string = 'guest'
 
     def map_dev(self):
         self.mapped = True

nova/virt/disk/loop.py

@@ -22,6 +22,7 @@ from nova.virt.disk import mount
 class Mount(mount.Mount):
     """loop back support for raw images."""
     mode = 'loop'
+    device_id_string = mode
 
     def get_dev(self):
         out, err = utils.trycmd('losetup', '--find', '--show', self.image,

nova/virt/disk/mount.py

@@ -30,7 +30,7 @@ class Mount(object):
     to be called in that order.
     """
 
-    def __init__(self, image, mount_dir, partition=None):
+    def __init__(self, image, mount_dir, partition=None, device=None):
 
         # Input
         self.image = image
@@ -42,7 +42,24 @@ class Mount(object):
 
         # Internal
         self.linked = self.mapped = self.mounted = False
-        self.device = self.mapped_device = None
+        self.device = self.mapped_device = device
+
+        # Reset to mounted dir if possible
+        self.reset_dev()
+
+    def reset_dev(self):
+        """Reset device paths to allow unmounting."""
+        if not self.device:
+            return
+
+        self.linked = self.mapped = self.mounted = True
+
+        device = self.device
+        if os.path.isabs(device) and os.path.exists(device):
+            if device.startswith('/dev/mapper/'):
+                device = os.path.basename(device)
+                device, self.partition = device.rsplit('p', 1)
+                self.device = os.path.join('/dev', device)
 
     def get_dev(self):
         """Make the image available as a block device in the file system."""

nova/virt/disk/nbd.py

@@ -40,6 +40,7 @@ FLAGS.register_opts(nbd_opts)
 class Mount(mount.Mount):
     """qemu-nbd support disk images."""
     mode = 'nbd'
+    device_id_string = mode
 
     # NOTE(padraig): There are three issues with this nbd device handling
     #  1. max_nbd_devices should be inferred (#861504)
@@ -69,7 +70,11 @@ class Mount(mount.Mount):
         return device
 
     def _free_nbd(self, device):
-        self._DEVICES.append(device)
+        # The device could already be present if unget_dev
+        # is called right after a nova restart
+        # (when destroying an LXC container for example).
+        if not device in self._DEVICES:
+            self._DEVICES.append(device)
 
     def get_dev(self):
         device = self._allocate_nbd()

nova/virt/libvirt/driver.py

@@ -271,7 +271,6 @@ class LibvirtDriver(driver.ComputeDriver):
         self._host_state = None
         self._initiator = None
         self._wrapped_conn = None
-        self.container = None
         self.read_only = read_only
         if FLAGS.firewall_driver not in firewall.drivers:
             FLAGS.set_default('firewall_driver', firewall.drivers[0])
@@ -551,7 +550,10 @@ class LibvirtDriver(driver.ComputeDriver):
         LOG.info(_('Deleting instance files %(target)s') % locals(),
                  instance=instance)
         if FLAGS.libvirt_type == 'lxc':
-            disk.destroy_container(self.container)
+            container_dir = os.path.join(FLAGS.instances_path,
+                                         instance['name'],
+                                         'rootfs')
+            disk.destroy_container(container_dir=container_dir)
         if os.path.exists(target):
             # If we fail to get rid of the directory
             # tree, this shouldn't block deletion of
@@ -1242,7 +1244,9 @@ class LibvirtDriver(driver.ComputeDriver):
         libvirt_utils.write_to_file(basepath('libvirt.xml'), libvirt_xml)
 
         if FLAGS.libvirt_type == 'lxc':
-            container_dir = '%s/rootfs' % basepath(suffix='')
+            container_dir = os.path.join(FLAGS.instances_path,
+                                         instance['name'],
+                                         'rootfs')
             libvirt_utils.ensure_tree(container_dir)
 
         # NOTE(dprince): for rescue console.log may already exist... chown it.
@@ -1438,9 +1442,9 @@ class LibvirtDriver(driver.ComputeDriver):
                          instance=instance)
 
         if FLAGS.libvirt_type == 'lxc':
-            self.container = disk.setup_container(basepath('disk'),
+            disk.setup_container(basepath('disk'),
-                                                  container_dir=container_dir,
+                                 container_dir=container_dir,
-                                                  use_cow=FLAGS.use_cow_images)
+                                 use_cow=FLAGS.use_cow_images)
 
         if FLAGS.libvirt_type == 'uml':
             libvirt_utils.chown(basepath('disk'), 'root')
@@ -1569,7 +1573,7 @@ class LibvirtDriver(driver.ComputeDriver):
             fs.source_type = "mount"
             fs.source_dir = os.path.join(FLAGS.instances_path,
                                          instance['name'],
-                                         "rootfs")
+                                         'rootfs')
             devices.append(fs)
         else:
             if image_meta and image_meta.get('disk_format') == 'iso':