Merge "Implement resize down for XenAPI"

15 files changed, 334 insertions, 197 deletions

diff --git a/nova/api/openstack/v2/servers.py b/nova/api/openstack/v2/servers.py
index 5066633be..f41ed9467 100644
--- a/nova/api/openstack/v2/servers.py
+++ b/nova/api/openstack/v2/servers.py
@@ -679,9 +679,6 @@ class Controller(wsgi.Controller):
         except exception.CannotResizeToSameSize:
             msg = _("Resize requires a change in size.")
             raise exc.HTTPBadRequest(explanation=msg)
-        except exception.CannotResizeToSmallerSize:
-            msg = _("Resizing to a smaller size is not supported.")
-            raise exc.HTTPBadRequest(explanation=msg)
 
         return webob.Response(status_int=202)
 
diff --git a/nova/compute/api.py b/nova/compute/api.py
index c7cf2a1e9..787817e31 100644
--- a/nova/compute/api.py
+++ b/nova/compute/api.py
@@ -1275,8 +1275,6 @@ class API(base.Base):
 
         current_memory_mb = current_instance_type['memory_mb']
         new_memory_mb = new_instance_type['memory_mb']
-        if current_memory_mb > new_memory_mb:
-            raise exception.CannotResizeToSmallerSize()
 
         if (current_memory_mb == new_memory_mb) and flavor_id:
             raise exception.CannotResizeToSameSize()
diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index 9bacae271..311d17c6a 100644
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -1069,6 +1069,8 @@ class ComputeManager(manager.SchedulerDependentManager):
         migration_ref = self.db.migration_get(context, migration_id)
         instance_ref = self.db.instance_get_by_uuid(context,
                 migration_ref.instance_uuid)
+        instance_type_ref = self.db.instance_type_get(context,
+                migration_ref.new_instance_type_id)
 
         self.db.migration_update(context,
                                  migration_id,
@@ -1076,7 +1078,8 @@ class ComputeManager(manager.SchedulerDependentManager):
 
         try:
             disk_info = self.driver.migrate_disk_and_power_off(
-                    context, instance_ref, migration_ref['dest_host'])
+                    context, instance_ref, migration_ref['dest_host'],
+                    instance_type_ref)
         except exception.MigrationError, error:
             LOG.error(_('%s. Setting instance vm_state to ERROR') % (error,))
             self._instance_update(context,
diff --git a/nova/exception.py b/nova/exception.py
index f30218ab0..8da1d752c 100644
--- a/nova/exception.py
+++ b/nova/exception.py
@@ -830,10 +830,6 @@ class CannotResizeToSameSize(NovaException):
     message = _("When resizing, instances must change size!")
 
 
-class CannotResizeToSmallerSize(NovaException):
-    message = _("Resizing to a smaller size is not supported.")
-
-
 class ImageTooLarge(NovaException):
     message = _("Image is larger than instance type allows")
 
diff --git a/nova/tests/test_compute.py b/nova/tests/test_compute.py
index 1affd6b87..bccc590c3 100644
--- a/nova/tests/test_compute.py
+++ b/nova/tests/test_compute.py
@@ -1568,23 +1568,6 @@ class ComputeAPITestCase(BaseTestCase):
 
         self.compute.terminate_instance(context, instance['uuid'])
 
-    def test_resize_down_fails(self):
-        """Ensure resizing down raises and fails"""
-        instance = self._create_fake_instance()
-        context = self.context.elevated()
-        instance = db.instance_get_by_uuid(context, instance['uuid'])
-        self.compute.run_instance(self.context, instance['uuid'])
-
-        inst_type = instance_types.get_instance_type_by_name('m1.xlarge')
-        db.instance_update(self.context, instance['uuid'],
-                {'instance_type_id': inst_type['id']})
-
-        instance = db.instance_get_by_uuid(context, instance['uuid'])
-        self.assertRaises(exception.CannotResizeToSmallerSize,
-                          self.compute_api.resize, context, instance, 1)
-
-        self.compute.terminate_instance(context, instance['uuid'])
-
     def test_resize_same_size_fails(self):
         """Ensure invalid flavors raise"""
         context = self.context.elevated()
diff --git a/nova/tests/test_virt_drivers.py b/nova/tests/test_virt_drivers.py
index 8b4fa177f..8c5cda6f0 100644
--- a/nova/tests/test_virt_drivers.py
+++ b/nova/tests/test_virt_drivers.py
@@ -173,8 +173,9 @@ class _VirtDriverTestCase(test.TestCase):
     @catch_notimplementederror
     def test_migrate_disk_and_power_off(self):
         instance_ref, network_info = self._get_running_instance()
+        instance_type_ref = test_utils.get_test_instance_type()
         self.connection.migrate_disk_and_power_off(
-            self.ctxt, instance_ref, 'dest_host')
+            self.ctxt, instance_ref, 'dest_host', instance_type_ref)
 
     @catch_notimplementederror
     def test_pause(self):
diff --git a/nova/tests/test_xenapi.py b/nova/tests/test_xenapi.py
index 906f176fd..c72ee37a7 100644
--- a/nova/tests/test_xenapi.py
+++ b/nova/tests/test_xenapi.py
@@ -803,17 +803,20 @@ class XenAPIMigrateInstance(test.TestCase):
                               product_version=(6, 0, 0))
         stubs.stubout_loopingcall_start(self.stubs)
         conn = xenapi_conn.get_connection(False)
-        conn._vmops.resize_instance(instance, '')
+        conn._vmops._resize_instance(instance, '')
         self.assertEqual(called['resize'], True)
 
     def test_migrate_disk_and_power_off(self):
         instance = db.instance_create(self.context, self.instance_values)
+        instance_type = db.instance_type_get_by_name(self.context, 'm1.large')
         stubs.stubout_session(self.stubs, stubs.FakeSessionForMigrationTests)
         conn = xenapi_conn.get_connection(False)
-        conn.migrate_disk_and_power_off(self.context, instance, '127.0.0.1')
+        conn.migrate_disk_and_power_off(self.context, instance,
+                                        '127.0.0.1', instance_type)
 
     def test_migrate_disk_and_power_off_passes_exceptions(self):
         instance = db.instance_create(self.context, self.instance_values)
+        instance_type = db.instance_type_get_by_name(self.context, 'm1.large')
         stubs.stubout_session(self.stubs, stubs.FakeSessionForMigrationTests)
 
         def fake_raise(*args, **kwargs):
@@ -823,7 +826,7 @@ class XenAPIMigrateInstance(test.TestCase):
         conn = xenapi_conn.get_connection(False)
         self.assertRaises(exception.MigrationError,
                           conn.migrate_disk_and_power_off,
-                          self.context, instance, '127.0.0.1')
+                          self.context, instance, '127.0.0.1', instance_type)
 
     def test_revert_migrate(self):
         instance = db.instance_create(self.context, self.instance_values)
@@ -1163,12 +1166,10 @@ class XenAPIAutoDiskConfigTestCase(test.TestCase):
     def assertIsPartitionCalled(self, called):
         marker = {"partition_called": False}
 
-        @classmethod
-        def fake_resize_partition_fs(cls, dev_path, partition_path):
+        def fake_resize_part_and_fs(dev, start, old, new):
             marker["partition_called"] = True
-
-        self.stubs.Set(vm_utils.VMHelper, "_resize_partition_and_fs",
-                       fake_resize_partition_fs)
+        self.stubs.Set(vm_utils, "_resize_part_and_fs",
+                       fake_resize_part_and_fs)
 
         instance = db.instance_create(self.context, self.instance_values)
         disk_image_type = vm_utils.ImageType.DISK_VHD
@@ -1193,12 +1194,10 @@ class XenAPIAutoDiskConfigTestCase(test.TestCase):
         """Should not partition unless fail safes pass"""
         self.instance_values['auto_disk_config'] = True
 
-        @classmethod
-        def fake_resize_partition_allowed(cls, dev_path, partition_path):
-            return False
-
-        self.stubs.Set(vm_utils.VMHelper, "_resize_partition_allowed",
-                       fake_resize_partition_allowed)
+        def fake_get_partitions(dev):
+            return [(1, 0, 100, 'ext4'), (2, 100, 200, 'ext4')]
+        self.stubs.Set(vm_utils, "_get_partitions",
+                       fake_get_partitions)
 
         self.assertIsPartitionCalled(False)
 
@@ -1209,10 +1208,9 @@ class XenAPIAutoDiskConfigTestCase(test.TestCase):
         """
         self.instance_values['auto_disk_config'] = True
 
-        @classmethod
-        def fake_resize_partition_allowed(cls, dev_path, partition_path):
-            return True
-        self.stubs.Set(vm_utils.VMHelper, "_resize_partition_allowed",
-                       fake_resize_partition_allowed)
+        def fake_get_partitions(dev):
+            return [(1, 0, 100, 'ext4')]
+        self.stubs.Set(vm_utils, "_get_partitions",
+                       fake_get_partitions)
 
         self.assertIsPartitionCalled(True)
diff --git a/nova/tests/utils.py b/nova/tests/utils.py
index e5de01275..cc387fbcd 100644
--- a/nova/tests/utils.py
+++ b/nova/tests/utils.py
@@ -34,6 +34,21 @@ def get_test_image_info(context, instance_ref):
     return image_service.show(context, image_id)
 
 
+def get_test_instance_type(context=None):
+    if not context:
+        context = get_test_admin_context()
+
+    test_instance_type = {'name': 'kinda.big',
+                          'memory_mb': 2048,
+                          'vcpus': 4,
+                          'local_gb': 40,
+                          'swap': 1024}
+
+    instance_type_ref = nova.db.instance_type_create(context,
+            test_instance_type)
+    return instance_type_ref
+
+
 def get_test_instance(context=None):
     if not context:
         context = get_test_admin_context()
diff --git a/nova/virt/driver.py b/nova/virt/driver.py
index e12be1f0e..f2e20bd3e 100644
--- a/nova/virt/driver.py
+++ b/nova/virt/driver.py
@@ -236,7 +236,8 @@ class ComputeDriver(object):
         """
         raise NotImplementedError()
 
-    def migrate_disk_and_power_off(self, context, instance, dest):
+    def migrate_disk_and_power_off(self, context, instance, dest,
+                                   instance_type):
         """
         Transfers the disk of a running instance in multiple phases, turning
         off the instance before the end.
diff --git a/nova/virt/fake.py b/nova/virt/fake.py
index feb85b7f1..1a3b237ea 100644
--- a/nova/virt/fake.py
+++ b/nova/virt/fake.py
@@ -138,7 +138,8 @@ class FakeConnection(driver.ComputeDriver):
     def poll_rescued_instances(self, timeout):
         pass
 
-    def migrate_disk_and_power_off(self, context, instance, dest):
+    def migrate_disk_and_power_off(self, context, instance, dest,
+                                   instance_type):
         pass
 
     def poll_unconfirmed_resizes(self, resize_confirm_window):
diff --git a/nova/virt/xenapi/fake.py b/nova/virt/xenapi/fake.py
index 4f40bb656..b7f665fa7 100644
--- a/nova/virt/xenapi/fake.py
+++ b/nova/virt/xenapi/fake.py
@@ -467,6 +467,9 @@ class SessionBase(object):
             raise Exception('No simulation in host_call_plugin for %s,%s' %
                             (plugin, method))
 
+    def VDI_get_virtual_size(self, *args):
+        return 1 * 1024 * 1024 * 1024
+
     def VDI_resize_online(self, *args):
         return 'derp'
 
diff --git a/nova/virt/xenapi/vm_utils.py b/nova/virt/xenapi/vm_utils.py
index 5ee3507e8..ca06a9450 100644
--- a/nova/virt/xenapi/vm_utils.py
+++ b/nova/virt/xenapi/vm_utils.py
@@ -387,19 +387,36 @@ class VMHelper(HelperBase):
         session.wait_for_task(task, instance.id)
 
     @classmethod
-    def auto_configure_disk(cls, session, vdi_ref):
-        """Partition and resize FS to match the size specified by
-        instance_types.local_gb.
-        """
-        with vdi_attached_here(session, vdi_ref, read_only=False) as dev:
-            dev_path = utils.make_dev_path(dev)
-            partition_path = utils.make_dev_path(dev, partition=1)
-            if cls._resize_partition_allowed(dev_path, partition_path):
-                cls._resize_partition_and_fs(dev_path, partition_path)
+    def resize_disk(cls, session, vdi_ref, instance_type):
+        # Copy VDI over to something we can resize
+        # NOTE(jerdfelt): Would be nice to just set vdi_ref to read/write
+        sr_ref = safe_find_sr(session)
+        copy_ref = session.call_xenapi('VDI.copy', vdi_ref, sr_ref)
+        copy_uuid = session.call_xenapi('VDI.get_uuid', copy_ref)
+
+        try:
+            # Resize partition and filesystem down
+            cls.auto_configure_disk(session=session,
+                                    vdi_ref=copy_ref,
+                                    new_gb=instance_type['local_gb'])
+
+            # Create new VDI
+            new_ref = cls.fetch_blank_disk(session,
+                                           instance_type['id'])
+            new_uuid = session.call_xenapi('VDI.get_uuid', new_ref)
+
+            # Manually copy contents over
+            virtual_size = instance_type['local_gb'] * 1024 * 1024 * 1024
+            _copy_partition(session, copy_ref, new_ref, 1, virtual_size)
+
+            return new_ref, new_uuid
+        finally:
+            cls.destroy_vdi(session, copy_ref)
 
     @classmethod
-    def _resize_partition_allowed(cls, dev_path, partition_path):
-        """Determine whether we should resize the partition and the fs.
+    def auto_configure_disk(cls, session, vdi_ref, new_gb):
+        """Partition and resize FS to match the size specified by
+        instance_types.local_gb.
 
         This is a fail-safe to prevent accidentally destroying data on a disk
         erroneously marked as auto_disk_config=True.
@@ -413,52 +430,16 @@ class VMHelper(HelperBase):
 
             3. The file-system on the one partition must be ext3 or ext4.
         """
-        out, err = utils.execute("parted", "--script", "--machine",
-                                 partition_path, "print", run_as_root=True)
-        lines = [line for line in out.split('\n') if line]
-        partitions = lines[2:]
-
-        num_partitions = len(partitions)
-        fs_type = partitions[0].split(':')[4]
-        LOG.debug(_("Found %(num_partitions)s partitions, the first with"
-                    " fs_type '%(fs_type)s'") % locals())
-
-        allowed_fs = fs_type in ('ext3', 'ext4')
-        return num_partitions == 1 and allowed_fs
-
-    @classmethod
-    def _resize_partition_and_fs(cls, dev_path, partition_path):
-        """Resize partition and fileystem.
-
-        This assumes we are dealing with a single primary partition and using
-        ext3 or ext4.
-        """
-        # 1. Delete and recreate partition to end of disk
-        root_helper = FLAGS.root_helper
-        cmd = """echo "d
-n
-p
-1
-
-
-w
-" | %(root_helper)s fdisk %(dev_path)s""" % locals()
-        utils.execute(cmd, run_as_root=False, shell=True)
-
-        # 2. Remove ext3 journal (making it ext2)
-        utils.execute("tune2fs", "-O ^has_journal", partition_path,
-                      run_as_root=True)
-
-        # 3. fsck the disk
-        # NOTE(sirp): using -p here to automatically repair filesystem, is
-        # this okay?
-        utils.execute("e2fsck", "-f", "-p", partition_path, run_as_root=True)
+        with vdi_attached_here(session, vdi_ref, read_only=False) as dev:
+            partitions = _get_partitions(dev)
 
-        # 4. Resize the disk
-        utils.execute("resize2fs", partition_path, run_as_root=True)
+            if len(partitions) != 1:
+                return
 
-        # 5. Add back journal
-        utils.execute("tune2fs", "-j", partition_path, run_as_root=True)
+            num, start, old_sectors, ptype = partitions[0]
+            if ptype in ('ext3', 'ext4'):
+                new_sectors = new_gb * 1024 * 1024 * 1024 / SECTOR_SIZE
+                _resize_part_and_fs(dev, start, old_sectors, new_sectors)
 
     @classmethod
     def generate_swap(cls, session, instance, vm_ref, userdevice, swap_mb):
@@ -1317,6 +1298,27 @@ def _is_vdi_pv(dev):
     return False
 
 
+def _get_partitions(dev):
+    """Return partition information (num, size, type) for a device."""
+    dev_path = utils.make_dev_path(dev)
+    out, err = utils.execute('parted', '--script', '--machine',
+                             dev_path, 'unit s', 'print',
+                             run_as_root=True)
+    lines = [line for line in out.split('\n') if line]
+    partitions = []
+
+    LOG.debug(_("Partitions:"))
+    for line in lines[2:]:
+        num, start, end, size, ptype = line.split(':')[:5]
+        start = int(start.rstrip('s'))
+        end = int(end.rstrip('s'))
+        size = int(size.rstrip('s'))
+        LOG.debug(_("  %(num)s: %(ptype)s %(size)d sectors") % locals())
+        partitions.append((num, start, size, ptype))
+
+    return partitions
+
+
 def _stream_disk(dev, image_type, virtual_size, image_file):
     offset = 0
     if image_type == ImageType.DISK:
@@ -1353,6 +1355,68 @@ def _write_partition(virtual_size, dev):
     LOG.debug(_('Writing partition table %s done.'), dev_path)
 
 
+def _resize_part_and_fs(dev, start, old_sectors, new_sectors):
+    """Resize partition and fileystem.
+
+    This assumes we are dealing with a single primary partition and using
+    ext3 or ext4.
+    """
+    size = new_sectors - start
+    end = new_sectors - 1
+
+    dev_path = utils.make_dev_path(dev)
+    partition_path = utils.make_dev_path(dev, partition=1)
+
+    # Remove ext3 journal (making it ext2)
+    utils.execute('tune2fs', '-O ^has_journal', partition_path,
+                  run_as_root=True)
+
+    # fsck the disk
+    # NOTE(sirp): using -p here to automatically repair filesystem, is
+    # this okay?
+    utils.execute('e2fsck', '-f', '-p', partition_path, run_as_root=True)
+
+    if new_sectors < old_sectors:
+        # Resizing down, resize filesystem before partition resize
+        utils.execute('resize2fs', partition_path, '%ds' % size,
+                      run_as_root=True)
+
+    utils.execute('parted', '--script', dev_path, 'rm', '1',
+                  run_as_root=True)
+    utils.execute('parted', '--script', dev_path, 'mkpart',
+                  'primary',
+                  '%ds' % start,
+                  '%ds' % end,
+                  run_as_root=True)
+
+    if new_sectors > old_sectors:
+        # Resizing up, resize filesystem after partition resize
+        utils.execute('resize2fs', partition_path, run_as_root=True)
+
+    # Add back journal
+    utils.execute('tune2fs', '-j', partition_path, run_as_root=True)
+
+
+def _copy_partition(session, src_ref, dst_ref, partition, virtual_size):
+    # Part of disk taken up by MBR
+    virtual_size -= MBR_SIZE_BYTES
+
+    with vdi_attached_here(session, src_ref, read_only=True) as src:
+        src_path = utils.make_dev_path(src, partition=partition)
+
+        with vdi_attached_here(session, dst_ref, read_only=False) as dst:
+            dst_path = utils.make_dev_path(dst, partition=partition)
+
+            _write_partition(virtual_size, dst)
+
+            num_blocks = virtual_size / SECTOR_SIZE
+            utils.execute('dd',
+                          'if=%s' % src_path,
+                          'of=%s' % dst_path,
+                          'count=%d' % num_blocks,
+                          run_as_root=True)
+
+
 def _mount_filesystem(dev_path, dir):
     """mounts the device specified by dev_path in dir"""
     try:
diff --git a/nova/virt/xenapi/vmops.py b/nova/virt/xenapi/vmops.py
index 6430c4450..1a5cd8d33 100644
--- a/nova/virt/xenapi/vmops.py
+++ b/nova/virt/xenapi/vmops.py
@@ -21,7 +21,6 @@ Management class for VM-related functions (spawn, reboot, etc).
 
 import base64
 import json
-import M2Crypto
 import os
 import pickle
 import random
@@ -30,6 +29,10 @@ import sys
 import time
 import uuid
 
+import M2Crypto
+
+from nova.compute import api as compute
+from nova.compute import power_state
 from nova import context as nova_context
 from nova import db
 from nova import exception
@@ -37,15 +40,14 @@ from nova import flags
 from nova import ipv6
 from nova import log as logging
 from nova import utils
-
-from nova.compute import api as compute
-from nova.compute import power_state
 from nova.virt import driver
-from nova.virt.xenapi.volume_utils import VolumeHelper
-from nova.virt.xenapi.network_utils import NetworkHelper
-from nova.virt.xenapi.vm_utils import VMHelper
-from nova.virt.xenapi.vm_utils import ImageType
+from nova.virt.xenapi import volume_utils
+from nova.virt.xenapi import network_utils
+from nova.virt.xenapi import vm_utils
 
+VolumeHelper = volume_utils.VolumeHelper
+NetworkHelper = network_utils.NetworkHelper
+VMHelper = vm_utils.VMHelper
 XenAPI = None
 LOG = logging.getLogger("nova.virt.xenapi.vmops")
 
@@ -141,14 +143,14 @@ class VMOps(object):
 
     def finish_migration(self, context, migration, instance, disk_info,
                          network_info, image_meta, resize_instance):
-        vdi_uuid = self.link_disks(instance, disk_info['base_copy'],
-                disk_info['cow'])
+        vdi_uuid = self._move_disks(instance, disk_info)
+
+        if resize_instance:
+            self._resize_instance(instance, vdi_uuid)
 
         vm_ref = self._create_vm(context, instance,
                                  [dict(vdi_type='os', vdi_uuid=vdi_uuid)],
                                  network_info, image_meta)
-        if resize_instance:
-            self.resize_instance(instance, vdi_uuid)
 
         # 5. Start VM
         self._start(instance, vm_ref=vm_ref)
@@ -175,7 +177,7 @@ class VMOps(object):
 
         for vdi in vdis:
             if vdi["vdi_type"] == "os":
-                self.resize_instance(instance, vdi["vdi_uuid"])
+                self._resize_instance(instance, vdi["vdi_uuid"])
 
         return vdis
 
@@ -242,11 +244,11 @@ class VMOps(object):
             if instance.kernel_id:
                 kernel = VMHelper.fetch_image(context, self._session,
                         instance, instance.kernel_id, instance.user_id,
-                        instance.project_id, ImageType.KERNEL)[0]
+                        instance.project_id, vm_utils.ImageType.KERNEL)[0]
             if instance.ramdisk_id:
                 ramdisk = VMHelper.fetch_image(context, self._session,
                         instance, instance.ramdisk_id, instance.user_id,
-                        instance.project_id, ImageType.RAMDISK)[0]
+                        instance.project_id, vm_utils.ImageType.RAMDISK)[0]
 
             # NOTE(jk0): Since vdi_type may contain either 'os' or 'swap', we
             # need to ensure that the 'swap' VDI is not chosen as the mount
@@ -318,12 +320,15 @@ class VMOps(object):
 
     def _attach_disks(self, instance, disk_image_type, vm_ref, first_vdi_ref,
             vdis):
+        ctx = nova_context.get_admin_context()
+
         instance_uuid = instance['uuid']
+
         # device 0 reserved for RW disk
         userdevice = 0
 
         # DISK_ISO needs two VBDs: the ISO disk and a blank RW disk
-        if disk_image_type == ImageType.DISK_ISO:
+        if disk_image_type == vm_utils.ImageType.DISK_ISO:
             LOG.debug("detected ISO image type, going to create blank VM for "
                   "install")
 
@@ -346,8 +351,11 @@ class VMOps(object):
                 LOG.debug(_("Auto configuring disk for instance"
                             " %(instance_uuid)s, attempting to"
                             " resize partition...") % locals())
+                instance_type = db.instance_type_get(ctx,
+                        instance.instance_type_id)
                 VMHelper.auto_configure_disk(session=self._session,
-                                             vdi_ref=first_vdi_ref)
+                                             vdi_ref=first_vdi_ref,
+                                             new_gb=instance_type['local_gb'])
 
             VolumeHelper.create_vbd(session=self._session, vm_ref=vm_ref,
                                     vdi_ref=first_vdi_ref,
@@ -357,7 +365,6 @@ class VMOps(object):
             # userdevice 1 is reserved for rescue and we've used '0'
             userdevice = 2
 
-        ctx = nova_context.get_admin_context()
         instance_type = db.instance_type_get(ctx, instance.instance_type_id)
         swap_mb = instance_type['swap']
         generate_swap = swap_mb and FLAGS.xenapi_generate_swap
@@ -509,9 +516,9 @@ class VMOps(object):
                     LOG.debug(_("Skipping VDI destroy for %s"), vdi_to_remove)
             if item['file']:
                 # There is also a file to remove.
-                if vdi_type == ImageType.KERNEL_STR:
+                if vdi_type == vm_utils.ImageType.KERNEL_STR:
                     kernel_file = item['file']
-                elif vdi_type == ImageType.RAMDISK_STR:
+                elif vdi_type == vm_utils.ImageType.RAMDISK_STR:
                     ramdisk_file = item['file']
 
         if kernel_file or ramdisk_file:
@@ -656,8 +663,10 @@ class VMOps(object):
                     " %(progress)d") % locals())
         db.instance_update(context, instance_uuid, {'progress': progress})
 
-    def migrate_disk_and_power_off(self, context, instance, dest):
-        """Copies a VHD from one host machine to another.
+    def migrate_disk_and_power_off(self, context, instance, dest,
+                                   instance_type):
+        """Copies a VHD from one host machine to another, possibly
+        resizing filesystem before hand.
 
         :param instance: the instance that owns the VHD in question.
         :param dest: the destination host machine.
@@ -692,23 +701,69 @@ class VMOps(object):
 
             sr_path = VMHelper.get_sr_path(self._session)
 
-            # 2. Transfer the base copy
-            self._migrate_vhd(instance, base_copy_uuid, dest, sr_path)
-            self._update_instance_progress(context, instance,
-                                           step=2,
-                                           total_steps=RESIZE_TOTAL_STEPS)
-
-            # 3. Now power down the instance
-            self._shutdown(instance, vm_ref, hard=False)
-            self._update_instance_progress(context, instance,
-                                           step=3,
-                                           total_steps=RESIZE_TOTAL_STEPS)
-
-            # 4. Transfer the COW VHD
-            self._migrate_vhd(instance, cow_uuid, dest, sr_path)
-            self._update_instance_progress(context, instance,
-                                           step=4,
-                                           total_steps=RESIZE_TOTAL_STEPS)
+            if instance['auto_disk_config'] and \
+               instance['local_gb'] > instance_type['local_gb']:
+                # Resizing disk storage down
+                old_gb = instance['local_gb']
+                new_gb = instance_type['local_gb']
+
+                LOG.debug(_("Resizing down VDI %(cow_uuid)s from "
+                          "%(old_gb)dGB to %(new_gb)dGB") % locals())
+
+                # 2. Power down the instance before resizing
+                self._shutdown(instance, vm_ref, hard=False)
+                self._update_instance_progress(context, instance,
+                                               step=2,
+                                               total_steps=RESIZE_TOTAL_STEPS)
+
+                # 3. Copy VDI, resize partition and filesystem, forget VDI,
+                # truncate VHD
+                new_ref, new_uuid = VMHelper.resize_disk(self._session,
+                                                         vdi_ref,
+                                                         instance_type)
+                self._update_instance_progress(context, instance,
+                                               step=3,
+                                               total_steps=RESIZE_TOTAL_STEPS)
+
+                # 4. Transfer the new VHD
+                self._migrate_vhd(instance, new_uuid, dest, sr_path)
+                self._update_instance_progress(context, instance,
+                                               step=4,
+                                               total_steps=RESIZE_TOTAL_STEPS)
+
+                # Clean up VDI now that it's been copied
+                VMHelper.destroy_vdi(self._session, new_ref)
+
+                vdis = {'base_copy': new_uuid}
+            else:
+                # Resizing disk storage up, will be handled on destination
+
+                # As an optimization, we transfer the base VDI first,
+                # then shut down the VM, followed by transfering the COW
+                # VDI.
+
+                # 2. Transfer the base copy
+                self._migrate_vhd(instance, base_copy_uuid, dest, sr_path)
+                self._update_instance_progress(context, instance,
+                                               step=2,
+                                               total_steps=RESIZE_TOTAL_STEPS)
+
+                # 3. Now power down the instance
+                self._shutdown(instance, vm_ref, hard=False)
+                self._update_instance_progress(context, instance,
+                                               step=3,
+                                               total_steps=RESIZE_TOTAL_STEPS)
+
+                # 4. Transfer the COW VHD
+                self._migrate_vhd(instance, cow_uuid, dest, sr_path)
+                self._update_instance_progress(context, instance,
+                                               step=4,
+                                               total_steps=RESIZE_TOTAL_STEPS)
+
+                # TODO(mdietz): we could also consider renaming these to
+                # something sensible so we don't need to blindly pass
+                # around dictionaries
+                vdis = {'base_copy': base_copy_uuid, 'cow': cow_uuid}
 
             # NOTE(sirp): in case we're resizing to the same host (for dev
             # purposes), apply a suffix to name-label so the two VM records
@@ -720,20 +775,27 @@ class VMOps(object):
                 self._destroy(instance, template_vm_ref,
                         shutdown=False, destroy_kernel_ramdisk=False)
 
-        # TODO(mdietz): we could also consider renaming these to something
-        # sensible so we don't need to blindly pass around dictionaries
-        return {'base_copy': base_copy_uuid, 'cow': cow_uuid}
+        return vdis
 
-    def link_disks(self, instance, base_copy_uuid, cow_uuid):
-        """Links the base copy VHD to the COW via the XAPI plugin."""
+    def _move_disks(self, instance, disk_info):
+        """Move and possibly link VHDs via the XAPI plugin."""
+        base_copy_uuid = disk_info['base_copy']
         new_base_copy_uuid = str(uuid.uuid4())
-        new_cow_uuid = str(uuid.uuid4())
+
         params = {'instance_uuid': instance['uuid'],
+                  'sr_path': VMHelper.get_sr_path(self._session),
                   'old_base_copy_uuid': base_copy_uuid,
-                  'old_cow_uuid': cow_uuid,
-                  'new_base_copy_uuid': new_base_copy_uuid,
-                  'new_cow_uuid': new_cow_uuid,
-                  'sr_path': VMHelper.get_sr_path(self._session), }
+                  'new_base_copy_uuid': new_base_copy_uuid}
+
+        if 'cow' in disk_info:
+            cow_uuid = disk_info['cow']
+            new_cow_uuid = str(uuid.uuid4())
+            params['old_cow_uuid'] = cow_uuid
+            params['new_cow_uuid'] = new_cow_uuid
+
+            new_uuid = new_cow_uuid
+        else:
+            new_uuid = new_base_copy_uuid
 
         task = self._session.async_call_plugin('migration',
                 'move_vhds_into_sr', {'params': pickle.dumps(params)})
@@ -744,25 +806,33 @@ class VMOps(object):
 
         # Set name-label so we can find if we need to clean up a failed
         # migration
-        VMHelper.set_vdi_name_label(self._session, new_cow_uuid,
+        VMHelper.set_vdi_name_label(self._session, new_uuid,
                                     instance.name)
 
-        return new_cow_uuid
+        return new_uuid
 
-    def resize_instance(self, instance, vdi_uuid):
-        """Resize a running instance by changing its RAM and disk size."""
+    def _resize_instance(self, instance, vdi_uuid):
+        """Resize a running instance by changing its disk size."""
         #TODO(mdietz): this will need to be adjusted for swap later
-        #The new disk size must be in bytes
 
         new_disk_size = instance.local_gb * 1024 * 1024 * 1024
-        if new_disk_size > 0:
-            instance_name = instance.name
-            instance_local_gb = instance.local_gb
-            LOG.debug(_("Resizing VDI %(vdi_uuid)s for instance"
-                        "%(instance_name)s. Expanding to %(instance_local_gb)d"
-                        " GB") % locals())
-            vdi_ref = self._session.call_xenapi('VDI.get_by_uuid', vdi_uuid)
-            # for an instance with no local storage
+        if not new_disk_size:
+            return
+
+        # Get current size of VDI
+        vdi_ref = self._session.call_xenapi('VDI.get_by_uuid', vdi_uuid)
+        virtual_size = self._session.call_xenapi('VDI.get_virtual_size',
+                                                 vdi_ref)
+        virtual_size = int(virtual_size)
+
+        instance_name = instance.name
+        old_gb = virtual_size / (1024 * 1024 * 1024)
+        new_gb = instance.local_gb
+
+        if virtual_size < new_disk_size:
+            # Resize up. Simple VDI resize will do the trick
+            LOG.debug(_("Resizing up VDI %(vdi_uuid)s from %(old_gb)dGB to "
+                        "%(new_gb)dGB") % locals())
             if self._product_version[0] > 5:
                 resize_func_name = 'VDI.resize'
             else:
diff --git a/nova/virt/xenapi_conn.py b/nova/virt/xenapi_conn.py
index 7f8edcc14..da722aa59 100644
--- a/nova/virt/xenapi_conn.py
+++ b/nova/virt/xenapi_conn.py
@@ -245,10 +245,12 @@ class XenAPIConnection(driver.ComputeDriver):
         """Unpause paused VM instance"""
         self._vmops.unpause(instance)
 
-    def migrate_disk_and_power_off(self, context, instance, dest):
+    def migrate_disk_and_power_off(self, context, instance, dest,
+                                   instance_type):
         """Transfers the VHD of a running instance to another host, then shuts
         off the instance copies over the COW disk"""
-        return self._vmops.migrate_disk_and_power_off(context, instance, dest)
+        return self._vmops.migrate_disk_and_power_off(context, instance,
+                                                      dest, instance_type)
 
     def suspend(self, instance):
         """suspend the specified instance"""
diff --git a/plugins/xenserver/xenapi/etc/xapi.d/plugins/migration b/plugins/xenserver/xenapi/etc/xapi.d/plugins/migration
index 19b5e98e8..adcfc2608 100755
--- a/plugins/xenserver/xenapi/etc/xapi.d/plugins/migration
+++ b/plugins/xenserver/xenapi/etc/xapi.d/plugins/migration
@@ -37,50 +37,55 @@ def move_vhds_into_sr(session, args):
     params = pickle.loads(exists(args, 'params'))
     instance_uuid = params['instance_uuid']
 
-    old_base_copy_uuid = params['old_base_copy_uuid']
-    old_cow_uuid = params['old_cow_uuid']
-
-    new_base_copy_uuid = params['new_base_copy_uuid']
-    new_cow_uuid = params['new_cow_uuid']
-
     sr_path = params['sr_path']
-    sr_temp_path = "%s/tmp/" % sr_path
+    sr_temp_path = "%s/tmp" % sr_path
+    temp_vhd_path = "%s/instance%s" % (sr_temp_path, instance_uuid)
+
+    logging.debug('Creating temporary SR path %s' % temp_vhd_path)
+    os.makedirs(temp_vhd_path)
 
     # Discover the copied VHDs locally, and then set up paths to copy
     # them to under the SR
     source_image_path = "/images/instance%s" % instance_uuid
+
+    old_base_copy_uuid = params['old_base_copy_uuid']
+    new_base_copy_uuid = params['new_base_copy_uuid']
     source_base_copy_path = "%s/%s.vhd" % (source_image_path,
             old_base_copy_uuid)
-    source_cow_path = "%s/%s.vhd" % (source_image_path, old_cow_uuid)
-
-    temp_vhd_path = "%s/instance%s/" % (sr_temp_path, instance_uuid)
     new_base_copy_path = "%s/%s.vhd" % (temp_vhd_path, new_base_copy_uuid)
-    new_cow_path = "%s/%s.vhd" % (temp_vhd_path, new_cow_uuid)
 
-    logging.debug('Creating temporary SR path %s' % temp_vhd_path)
-    os.makedirs(temp_vhd_path)
-
-    logging.debug('Moving %s into %s' % (source_base_copy_path, temp_vhd_path))
+    logging.debug('Moving base %s into %s' % (source_base_copy_path,
+                                              temp_vhd_path))
     shutil.move(source_base_copy_path, new_base_copy_path)
 
-    logging.debug('Moving %s into %s' % (source_cow_path, temp_vhd_path))
-    shutil.move(source_cow_path, new_cow_path)
+    if 'old_cow_uuid' in params:
+        old_cow_uuid = params['old_cow_uuid']
+        new_cow_uuid = params['new_cow_uuid']
 
-    logging.debug('Cleaning up %s' % source_image_path)
-    os.rmdir(source_image_path)
+        source_cow_path = "%s/%s.vhd" % (source_image_path, old_cow_uuid)
+        new_cow_path = "%s/%s.vhd" % (temp_vhd_path, new_cow_uuid)
 
-    # Link the COW to the base copy
-    logging.debug('Attaching COW to the base copy %s -> %s' %
-            (new_cow_path, new_base_copy_path))
-    subprocess.call(shlex.split('/usr/sbin/vhd-util modify -n %s -p %s' %
-            (new_cow_path, new_base_copy_path)))
+        logging.debug('Moving COW %s into %s' % (source_cow_path,
+                                                 temp_vhd_path))
+        shutil.move(source_cow_path, new_cow_path)
 
-    logging.debug('Moving VHDs into SR %s' % sr_path)
-    # NOTE(sirp): COW should be copied before base_copy to avoid snapwatchd
-    # GC'ing an unreferenced base copy VDI
-    shutil.move(new_cow_path, sr_path)
+        # Link the COW to the base copy
+        logging.debug('Attaching COW to the base %s -> %s' %
+                      (new_cow_path, new_base_copy_path))
+        subprocess.call(['/usr/sbin/vhd-util', 'modify',
+                         '-n', new_cow_path, '-p', new_base_copy_path])
+
+        # NOTE(sirp): COW should be copied before base_copy to avoid
+        # snapwatchd GC'ing an unreferenced base copy VDI
+        logging.debug('Moving COW %s to %s' % (new_cow_path, sr_path))
+        shutil.move(new_cow_path, sr_path)
+
+    logging.debug('Moving base %s to %s' % (new_base_copy_path, sr_path))
     shutil.move(new_base_copy_path, sr_path)
 
+    logging.debug('Cleaning up source path %s' % source_image_path)
+    os.rmdir(source_image_path)
+
     logging.debug('Cleaning up temporary SR path %s' % temp_vhd_path)
     os.rmdir(temp_vhd_path)
     return ""
@@ -103,7 +108,7 @@ def transfer_vhd(session, args):
 
     ssh_cmd = '\"ssh -o StrictHostKeyChecking=no\"'
 
-    rsync_args = shlex.split('nohup /usr/bin/rsync -av --progress -e %s %s %s'
+    rsync_args = shlex.split('nohup /usr/bin/rsync -av -e %s %s %s'
             % (ssh_cmd, source_path, dest_path))
 
     logging.debug('rsync %s' % (' '.join(rsync_args, )))