From 45f8aefcd33b7848d33ae2e8d9801925cf8365e7 Mon Sep 17 00:00:00 2001
From: Rick Harris <rconradharris@gmail.com>
Date: Sat, 7 Jul 2012 02:21:52 +0000
Subject: Remove VDI chain limit for snapshots.

Snapshots and migrations were coded with a simplifying assumption that
the maximum length of a VDI chain would be 3. Now that fast-cloning has
been added, this assumption no longer holds.

The goal of this patch is to remove the restriction for snapshots. A
follow-on patch will remove the restriction for migrations.

This patch changes the image-format for XenAPI images. Instead of naming
the VHDs, 'base', 'image', and 'snap', they are now numbered staring
with 0 as the leaf and going to N as the base-copy (root).

Old-style images are still supported.

Change-Id: Ieb073b42dc25db7cee4dfca7ff6525f7e7f46e8e
---
 nova/tests/xenapi/stubs.py   |  2 +-
 nova/virt/xenapi/vm_utils.py | 16 +++++++++-------
 nova/virt/xenapi/vmops.py    | 13 +++++++------
 3 files changed, 17 insertions(+), 14 deletions(-)

(limited to 'nova')

diff --git a/nova/tests/xenapi/stubs.py b/nova/tests/xenapi/stubs.py
index 83a17af84..ec944d84d 100644
--- a/nova/tests/xenapi/stubs.py
+++ b/nova/tests/xenapi/stubs.py
@@ -320,7 +320,7 @@ class FakeSessionForVolumeFailedTests(FakeSessionForVolumeTests):
 def stub_out_migration_methods(stubs):
     @contextlib.contextmanager
     def fake_snapshot_attached_here(session, instance, vm_ref, label):
-        yield dict(image='foo', snap='bar')
+        yield ['bar', 'foo']
 
     def fake_move_disks(self, instance, disk_info):
         vdi_ref = fake.create_vdi(instance['name'], 'fake')
diff --git a/nova/virt/xenapi/vm_utils.py b/nova/virt/xenapi/vm_utils.py
index bf343f977..4ff1a305d 100644
--- a/nova/virt/xenapi/vm_utils.py
+++ b/nova/virt/xenapi/vm_utils.py
@@ -98,6 +98,7 @@ SECTOR_SIZE = 512
 MBR_SIZE_SECTORS = 63
 MBR_SIZE_BYTES = MBR_SIZE_SECTORS * SECTOR_SIZE
 KERNEL_DIR = '/boot/guest'
+MAX_VDI_CHAIN_SIZE = 16
 
 
 class ImageType(object):
@@ -471,7 +472,7 @@ def snapshot_attached_here(session, instance, vm_ref, label):
     LOG.debug(_("Starting snapshot for VM"), instance=instance)
 
     try:
-        template_vm_ref, template_vdi_uuids = _create_snapshot(
+        template_vm_ref, vdi_uuids = _create_snapshot(
                 session, instance, vm_ref, label)
     except session.XenAPI.Failure, exc:
         LOG.error(_("Unable to Snapshot instance: %(exc)s"), locals(),
@@ -479,7 +480,7 @@ def snapshot_attached_here(session, instance, vm_ref, label):
         raise
 
     try:
-        yield template_vdi_uuids
+        yield vdi_uuids
     finally:
         _destroy_snapshot(session, instance, template_vm_ref)
 
@@ -505,10 +506,10 @@ def _create_snapshot(session, instance, vm_ref, label):
     parent_uuid, base_uuid = _wait_for_vhd_coalesce(
             session, instance, sr_ref, vm_vdi_ref, original_parent_uuid)
 
-    template_vdi_uuids = {'base': base_uuid,
-                          'image': parent_uuid,
-                          'snap': template_vdi_uuid}
-    return template_vm_ref, template_vdi_uuids
+    vdi_uuids = [vdi_rec['uuid'] for vdi_rec in
+                 _walk_vdi_chain(session, template_vdi_uuid)]
+
+    return template_vm_ref, vdi_uuids
 
 
 def _destroy_snapshot(session, instance, vm_ref):
@@ -908,8 +909,9 @@ def _fetch_vhd_image(context, session, instance, image_id):
     # which does not have the `uuid` module. To work around this,
     # we generate the uuids here (under Python 2.6+) and
     # pass them as arguments
+    uuid_stack = [str(uuid.uuid4()) for i in xrange(MAX_VDI_CHAIN_SIZE)]
     params = {'image_id': image_id,
-              'uuid_stack': [str(uuid.uuid4()) for i in xrange(3)],
+              'uuid_stack': uuid_stack,
               'sr_path': get_sr_path(session),
               'auth_token': getattr(context, 'auth_token', None)}
 
diff --git a/nova/virt/xenapi/vmops.py b/nova/virt/xenapi/vmops.py
index 23504bffe..f9958ff4c 100644
--- a/nova/virt/xenapi/vmops.py
+++ b/nova/virt/xenapi/vmops.py
@@ -606,9 +606,9 @@ class VMOps(object):
         label = "%s-snapshot" % instance.name
 
         with vm_utils.snapshot_attached_here(
-                self._session, instance, vm_ref, label) as template_vdi_uuids:
-            vm_utils.upload_image(context, self._session, instance,
-                                  template_vdi_uuids, image_id)
+                self._session, instance, vm_ref, label) as vdi_uuids:
+            vm_utils.upload_image(
+                    context, self._session, instance, vdi_uuids, image_id)
 
         LOG.debug(_("Finished snapshot and upload for VM"),
                   instance=instance)
@@ -674,13 +674,14 @@ class VMOps(object):
         # 1. Create Snapshot
         label = "%s-snapshot" % instance.name
         with vm_utils.snapshot_attached_here(
-                self._session, instance, vm_ref, label) as template_vdi_uuids:
-
+                self._session, instance, vm_ref, label) as vdi_uuids:
             self._update_instance_progress(context, instance,
                                            step=1,
                                            total_steps=RESIZE_TOTAL_STEPS)
 
-            base_copy_uuid = template_vdi_uuids['image']
+            # FIXME(sirp): this needs to work with VDI chain of arbitrary
+            # length
+            base_copy_uuid = vdi_uuids[1]
             _vdi_info = vm_utils.get_vdi_for_vm_safely(self._session, vm_ref)
             vdi_ref, vm_vdi_rec = _vdi_info
             cow_uuid = vm_vdi_rec['uuid']
-- 
cgit