XenAPI should only snapshot root disk

Change ID I3e2973 broke XenAPI migrations (resizes) as it caused snapshots
of all disks (including swap and ephemeral disks, if enabled) to be sent
over to the destination host.  The destination only expects vhds for the
root disk, named by sequence numbers.  swap and ephemeral disks ended up
with sequence numbers, also, messing up the re-building of the chain on
the destination.

Fixes bug 1064083

Change ID I3e2973 also didn't change the stub of VM.snapshot to
VDI.snapshot, but tests still passed due to the new code ignoring all
exceptions while snapshotting.  Potential issues in
snapshot_attached_here() would also be ignored due to excessive stubbing
in the xenapi migration testing.  This is also addressed here.

Change-Id: I145030f92a75615d056a30cabcb6ca97e34a8b6c

nova/tests/test_xenapi.py

@@ -34,7 +34,6 @@ from nova import flags
 from nova.openstack.common import importutils
 from nova.openstack.common import jsonutils
 from nova.openstack.common import log as logging
-from nova.openstack.common import timeutils
 from nova import test
 from nova.tests.db import fakes as db_fakes
 from nova.tests import fake_network

nova/tests/xenapi/stubs.py

@@ -15,7 +15,6 @@
 
 """Stubouts, mocks and fixtures for the test suite"""
 
-import contextlib
 import pickle
 import random
 
@@ -33,9 +32,9 @@ def stubout_firewall_driver(stubs, conn):
     def fake_none(self, *args):
         return
 
-    vmops = conn._vmops
-    stubs.Set(vmops.firewall_driver, 'prepare_instance_filter', fake_none)
-    stubs.Set(vmops.firewall_driver, 'instance_filter_exists', fake_none)
+    _vmops = conn._vmops
+    stubs.Set(_vmops.firewall_driver, 'prepare_instance_filter', fake_none)
+    stubs.Set(_vmops.firewall_driver, 'instance_filter_exists', fake_none)
 
 
 def stubout_instance_snapshot(stubs):
@@ -189,16 +188,9 @@ class FakeSessionForVMTests(fake.SessionBase):
         vm_rec = self.VM_start(_1, vm_ref, _2, _3)
         vm_rec['resident_on'] = host_ref
 
-    def VM_snapshot(self, session_ref, vm_ref, label):
-        status = "Running"
-        template_vm_ref = fake.create_vm(label, status, is_a_template=True,
-            is_control_domain=False)
-
+    def VDI_snapshot(self, session_ref, vm_ref, _1):
         sr_ref = "fakesr"
-        template_vdi_ref = fake.create_vdi(label, sr_ref, read_only=True)
-
-        template_vbd_ref = fake.create_vbd(template_vm_ref, template_vdi_ref)
-        return template_vm_ref
+        return fake.create_vdi('fakelabel', sr_ref, read_only=True)
 
     def SR_scan(self, session_ref, sr_ref):
         pass
@@ -300,23 +292,24 @@ class FakeSessionForVolumeFailedTests(FakeSessionForVolumeTests):
 
 
 def stub_out_migration_methods(stubs):
-    @contextlib.contextmanager
-    def fake_snapshot_attached_here(session, instance, vm_ref, label):
-        yield ['bar', 'foo']
+    fakesr = fake.create_sr()
 
     def fake_move_disks(self, instance, disk_info):
-        vdi_ref = fake.create_vdi(instance['name'], 'fake')
+        vdi_ref = fake.create_vdi(instance['name'], fakesr)
         vdi_rec = fake.get_record('VDI', vdi_ref)
         vdi_rec['other_config']['nova_disk_type'] = 'root'
         return {'uuid': vdi_rec['uuid'], 'ref': vdi_ref}
 
     def fake_get_vdi(session, vm_ref):
-        vdi_ref = fake.create_vdi('derp', 'herp')
+        vdi_ref_parent = fake.create_vdi('derp-parent', fakesr)
+        vdi_rec_parent = fake.get_record('VDI', vdi_ref_parent)
+        vdi_ref = fake.create_vdi('derp', fakesr,
+                sm_config={'vhd-parent': vdi_rec_parent['uuid']})
         vdi_rec = session.call_xenapi("VDI.get_record", vdi_ref)
-        return vdi_ref, {'uuid': vdi_rec['uuid'], }
+        return vdi_ref, vdi_rec
 
     def fake_sr(session, *args):
-        pass
+        return fakesr
 
     def fake_get_sr_path(*args):
         return "fake"
@@ -330,8 +323,6 @@ def stub_out_migration_methods(stubs):
     stubs.Set(vmops.VMOps, '_destroy', fake_destroy)
     stubs.Set(vm_utils, 'move_disks', fake_move_disks)
     stubs.Set(vm_utils, 'scan_default_sr', fake_sr)
-    stubs.Set(vm_utils, '_scan_sr', fake_sr)
-    stubs.Set(vm_utils, 'snapshot_attached_here', fake_snapshot_attached_here)
     stubs.Set(vm_utils, 'get_vdi_for_vm_safely', fake_get_vdi)
     stubs.Set(vm_utils, 'get_sr_path', fake_get_sr_path)
     stubs.Set(vm_utils, 'generate_ephemeral', fake_generate_ephemeral)