More accurate rescue mode testing for XenAPI

Update test_rescue to make sure the swap partition wasn't rescued. Since
this test fails with the current code, I also updated the code so the test
passed.

Fixes bug 997835

Change-Id: I9f09b3bbbee0ddfcbfdb243a7dff0b9bae99925d

3 files changed, 22 insertions, 14 deletions

diff --git a/nova/tests/test_xenapi.py b/nova/tests/test_xenapi.py
index 7e9265718..3056661b4 100644
--- a/nova/tests/test_xenapi.py
+++ b/nova/tests/test_xenapi.py
@@ -713,13 +713,26 @@ class XenAPIVMTestCase(test.TestCase):
     def test_rescue(self):
         instance = self._create_instance()
         session = xenapi_conn.XenAPISession('test_url', 'root', 'test_pass')
-        vm = vm_utils.VMHelper.lookup(session, instance.name)
-        vbd = xenapi_fake.create_vbd(vm, None)
+        vm_ref = vm_utils.VMHelper.lookup(session, instance.name)
+
+        xenapi_fake.create_vbd(vm_ref, "swap", userdevice=1)
+        xenapi_fake.create_vbd(vm_ref, "rootfs", userdevice=0)
+
         conn = xenapi_conn.get_connection(False)
         image_meta = {'id': glance_stubs.FakeGlance.IMAGE_VHD,
                       'disk_format': 'vhd'}
         conn.rescue(self.context, instance, [], image_meta)
 
+        vm = xenapi_fake.get_record('VM', vm_ref)
+        rescue_name = "%s-rescue" % vm["name_label"]
+        rescue_ref = vm_utils.VMHelper.lookup(session, rescue_name)
+        rescue_vm = xenapi_fake.get_record('VM', rescue_ref)
+
+        vdi_uuids = []
+        for vbd_uuid in rescue_vm["VBDs"]:
+            vdi_uuids.append(xenapi_fake.get_record('VBD', vbd_uuid)["VDI"])
+        self.assertTrue("swap" not in vdi_uuids)
+
     def test_unrescue(self):
         instance = self._create_instance()
         conn = xenapi_conn.get_connection(False)
diff --git a/nova/virt/xenapi/fake.py b/nova/virt/xenapi/fake.py
index 26f1c0847..223f8b109 100644
--- a/nova/virt/xenapi/fake.py
+++ b/nova/virt/xenapi/fake.py
@@ -161,10 +161,10 @@ def create_vdi(name_label, sr_ref, **kwargs):
     return _create_object('VDI', vdi_rec)
 
 
-def create_vbd(vm_ref, vdi_ref):
+def create_vbd(vm_ref, vdi_ref, userdevice=0):
     vbd_rec = {'VM': vm_ref,
                'VDI': vdi_ref,
-               'userdevice': '0',
+               'userdevice': str(userdevice),
                'currently_attached': False}
     vbd_ref = _create_object('VBD', vbd_rec)
     after_VBD_create(vbd_ref, vbd_rec)
diff --git a/nova/virt/xenapi/vmops.py b/nova/virt/xenapi/vmops.py
index d28b34f24..7ac455367 100644
--- a/nova/virt/xenapi/vmops.py
+++ b/nova/virt/xenapi/vmops.py
@@ -1014,17 +1014,12 @@ class VMOps(object):
 
         vbd_refs = self._session.call_xenapi("VM.get_VBDs", vm_ref)
 
-        if len(vbd_refs) == 0:
-            raise Exception(_("Unable to find VBD for VM"))
-        elif len(vbd_refs) == 1:
-            # If we only have one VBD, assume it's the root fs
-            vbd_ref = vbd_refs[0]
-        else:
-            # If we have more than one VBD, swap will be first by convention
-            # with the root fs coming second
-            vbd_ref = vbd_refs[1]
+        for vbd_uuid in vbd_refs:
+            vbd = self._session.call_xenapi("VBD.get_record", vbd_uuid)
+            if vbd["userdevice"] == "0":
+                return vbd["VDI"]
 
-        return self._session.call_xenapi("VBD.get_record", vbd_ref)["VDI"]
+        raise exception.NotFound(_("Unable to find root VBD/VDI for VM"))
 
     def _safe_destroy_vdis(self, vdi_refs):
         """Destroys the requested VDIs, logging any StorageError exceptions."""