From 3b62ab5e40e949e4f2431d3db985c8f2c20d70b5 Mon Sep 17 00:00:00 2001
From: Nicolas Simonds <nic@metacloud.com>
Date: Mon, 6 Oct 2014 15:24:58 -0700
Subject: [PATCH] Make _get_instance_block_device_info preserve
 root_device_name

On hard reboots,
nova.compute.manager.ComputeManager._get_instance_block_device_info will
faithfully reconstruct all of the block_device_info attributes that
the instance needs, except for the root_device_name.  This causes
the instance to effectively lose its disk configurations on hard
reboots.

This patch set will preserve the root_device_name if it is defined
for the instance.

Conflicts:
	nova/tests/unit/compute/test_compute.py

(cherry picked from commit ee435b4267b18eb910f7169792ea62244905733a)

Closes-Bug: #1378132
Change-Id: Ia36b1d6170ad120f794aa16d41ed4275b4b11f22
---
 nova/compute/manager.py            |  3 +++
 nova/tests/compute/test_compute.py | 11 +++++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index 8d444a98b0dd..f44273810712 100644
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -1975,7 +1975,10 @@ class ComputeManager(manager.Manager):
         # Get swap out of the list
         swap = driver_block_device.get_swap(swap)
 
+        root_device_name = instance.get('root_device_name')
+
         return {'swap': swap,
+                'root_device_name': root_device_name,
                 'ephemerals': ephemerals,
                 'block_device_mapping': block_device_mapping}
 
diff --git a/nova/tests/compute/test_compute.py b/nova/tests/compute/test_compute.py
index 69563a5bd296..ca715268d13b 100644
--- a/nova/tests/compute/test_compute.py
+++ b/nova/tests/compute/test_compute.py
@@ -2793,6 +2793,7 @@ class ComputeTestCase(BaseTestCase):
             expected = {
                 'swap': None,
                 'ephemerals': [],
+                'root_device_name': None,
                 'block_device_mapping': [{
                     'connection_info': {
                         'driver_volume_type': 'rbd'
@@ -2824,6 +2825,7 @@ class ComputeTestCase(BaseTestCase):
             expected = {
                 'swap': None,
                 'ephemerals': [],
+                'root_device_name': None,
                 'block_device_mapping': [{
                     'connection_info': {
                         'driver_volume_type': 'rbd'
@@ -2888,7 +2890,8 @@ class ComputeTestCase(BaseTestCase):
                                 'virtual_name': 'ephemeral0'},
                                {'device_name': '/dev/vdc', 'num': 1, 'size': 2,
                                 'virtual_name': 'ephemeral1'}],
-                'block_device_mapping': []
+                'block_device_mapping': [],
+                'root_device_name': None
             }
 
             block_device_info = (
@@ -5423,6 +5426,7 @@ class ComputeTestCase(BaseTestCase):
         self.mox.StubOutWithMock(self.compute.driver, 'pre_live_migration')
         self.compute.driver.pre_live_migration(mox.IsA(c), mox.IsA(instance),
                                                {'swap': None, 'ephemerals': [],
+                                                'root_device_name': None,
                                                 'block_device_mapping': []},
                                                mox.IgnoreArg(),
                                                mox.IgnoreArg(),
@@ -5492,7 +5496,8 @@ class ComputeTestCase(BaseTestCase):
                                  'rollback_live_migration_at_destination')
 
         block_device_info = {
-                'swap': None, 'ephemerals': [], 'block_device_mapping': []}
+                'swap': None, 'ephemerals': [], 'block_device_mapping': [],
+                'root_device_name': None}
         self.compute.driver.get_instance_disk_info(
                 instance.name,
                 block_device_info=block_device_info).AndReturn('fake_disk')
@@ -5668,6 +5673,7 @@ class ComputeTestCase(BaseTestCase):
 
             post_live_migration.assert_has_calls([
                 mock.call(c, instance, {'swap': None, 'ephemerals': [],
+                                        'root_device_name': None,
                                         'block_device_mapping': []}, None)])
             unfilter_instance.assert_has_calls([mock.call(instance, [])])
             migration = {'source_compute': srchost,
@@ -5826,6 +5832,7 @@ class ComputeTestCase(BaseTestCase):
                                  'rollback_live_migration_at_destination')
         self.compute.driver.rollback_live_migration_at_destination(c,
                 instance, [], {'swap': None, 'ephemerals': [],
+                               'root_device_name': None,
                                'block_device_mapping': []},
                 destroy_disks=True, migrate_data=None)