From 7adcf74c25730f7a4d77f7d9faf3aa741441f00b Mon Sep 17 00:00:00 2001
From: Daniel Vincze <dvincze@cloudbasesolutions.com>
Date: Wed, 9 Jun 2021 13:10:45 +0300
Subject: [PATCH] Reorder root disk as first disk in OSMorphing stage

---
 coriolis/osmorphing/osmount/windows.py |  8 +++-
 coriolis/tasks/osmorphing_tasks.py     | 65 ++++++++++++++++++++++++--
 2 files changed, 69 insertions(+), 4 deletions(-)

diff --git a/coriolis/osmorphing/osmount/windows.py b/coriolis/osmorphing/osmount/windows.py
index 93882aaae..0e7f6688c 100644
--- a/coriolis/osmorphing/osmount/windows.py
+++ b/coriolis/osmorphing/osmount/windows.py
@@ -213,7 +213,13 @@ def mount_os(self):
 
         for fs_root in [r for r in fs_roots if not r[:-1] == system_drive]:
             if self._conn.test_path("%sWindows\\System32" % fs_root):
-                return fs_root, None
+                root_disk_id = None
+                root_disk_ids = self._get_disk_ids_from_drive_letters(
+                    [fs_root.split(':')[0]])
+                if root_disk_ids:
+                    root_disk_id = root_disk_ids[0]
+
+                return fs_root, root_disk_id
 
         raise exception.OperatingSystemNotFound("root partition not found")
 
diff --git a/coriolis/tasks/osmorphing_tasks.py b/coriolis/tasks/osmorphing_tasks.py
index 7e6aafc41..89b7dc33e 100644
--- a/coriolis/tasks/osmorphing_tasks.py
+++ b/coriolis/tasks/osmorphing_tasks.py
@@ -1,6 +1,8 @@
 # Copyright 2016 Cloudbase Solutions Srl
 # All Rights Reserved.
 
+import re
+
 from oslo_log import log as logging
 
 from coriolis import constants
@@ -14,6 +16,55 @@
 LOG = logging.getLogger(__name__)
 
 
+def _reorder_root_disk(volumes_info, root_device, os_type):
+    """
+    Reorders volumes_info so that the root disk will always be the first volume
+
+    root_device is returned by the OSMount Tools as the root partition device
+    (i.e. /dev/vdd2 for linux).
+
+    For Linux, we need to strip the trailing digits
+    to get the actual disk device. After that, we convert the last letter of
+    the disk device name into the equivalent index by alphabetical order.
+
+    Windows OSMount Tools should directly return the root disk index extracted
+    from diskpart (as string; i.e. '1').
+
+    Reordering is done by swapping the indexes of the volumes_info list.
+    """
+    if not root_device:
+        LOG.warn('os_root_dev was not returned by OSMount Tools. '
+                 'Skipping root disk reordering')
+        return
+
+    # the default disk device of the migrated VM should be /dev/Xdb, because
+    # /dev/Xda should be the worker's root disk. Same for Windows: Disk 0
+    # should be the worker's root disk, and Disk 1 the migrated VM's root disk
+    linux_root_default = 'b'
+    windows_root_default = 1
+
+    supported_os_types = [constants.OS_TYPE_LINUX, constants.OS_TYPE_WINDOWS]
+    if os_type == constants.OS_TYPE_LINUX:
+        pattern = r'[0-9]'
+        root_disk = re.sub(pattern, '', root_device)
+        disk_index = ord(root_disk[-1]) - ord(linux_root_default)
+    elif os_type == constants.OS_TYPE_WINDOWS:
+        disk_index = int(root_device) - windows_root_default
+    else:
+        LOG.warn('Root disk reordering only supported for %s. Got OS type: %s.'
+                 'Skipping root disk reordering', supported_os_types, os_type)
+        return
+
+    if disk_index > 0:
+        if disk_index < len(volumes_info):
+            volumes_info[0], volumes_info[disk_index] = (
+                volumes_info[disk_index], volumes_info[0])
+        else:
+            LOG.warn('Disk device name index out of range: %s for device %s'
+                     'Skipping root disk reordering', disk_index, root_device)
+
+
+
 class OSMorphingTask(base.TaskRunner):
 
     @classmethod
@@ -28,7 +79,7 @@ def get_required_task_info_properties(cls):
 
     @classmethod
     def get_returned_task_info_properties(cls):
-        return []
+        return ["instance_deployment_info"]
 
     @classmethod
     def get_required_provider_types(cls):
@@ -53,13 +104,14 @@ def _run(self, ctxt, instance, origin, destination, task_info,
         osmorphing_connection_info = base.unmarshal_migr_conn_info(
             task_info['osmorphing_connection_info'])
         osmorphing_info = task_info.get('osmorphing_info', {})
+        instance_deployment_info = task_info.get('instance_deployment_info', {})
 
         user_scripts = task_info.get("user_scripts")
+        os_type = osmorphing_info.get("os_type")
         instance_script = None
         if user_scripts:
             instance_script = user_scripts.get("instances", {}).get(instance)
             if not instance_script:
-                os_type = osmorphing_info.get("os_type")
                 if os_type:
                     instance_script = user_scripts.get(
                         "global", {}).get(os_type)
@@ -72,7 +124,14 @@ def _run(self, ctxt, instance, origin, destination, task_info,
             instance_script,
             event_handler)
 
-        return {}
+        volumes_info = instance_deployment_info.get('volumes_info', [])
+        LOG.debug('Volumes info before root disk reordering: %s', volumes_info)
+        _reorder_root_disk(volumes_info, osmorphing_info.get('os_root_dev'),
+                           os_type)
+        LOG.debug('Volumes info after root disk reordering: %s', volumes_info)
+
+        return {
+            'instance_deployment_info': instance_deployment_info}
 
 
 class DeployOSMorphingResourcesTask(base.TaskRunner):