migration: Inactivate images after .save_live_complete_precopy()

Block migration may still access the image during its
.save_live_complete_precopy() implementation, so we should only
inactivate the image afterwards.

Another reason for the change is that inactivating an image fails when
there is still a non-device BlockBackend using it, which includes the
BBs used by block migration. We want to give block migration a chance to
release the BBs before trying to inactivate the image (this will be done
in another patch).

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>

migration/migration.c

@@ -1825,17 +1825,19 @@ static void migration_completion(MigrationState *s, int current_active_state,
 
         if (!ret) {
             ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
+            if (ret >= 0) {
+                qemu_file_set_rate_limit(s->to_dst_file, INT64_MAX);
+                qemu_savevm_state_complete_precopy(s->to_dst_file, false);
+            }
             /*
              * Don't mark the image with BDRV_O_INACTIVE flag if
              * we will go into COLO stage later.
              */
             if (ret >= 0 && !migrate_colo_enabled()) {
                 ret = bdrv_inactivate_all();
-            }
-            if (ret >= 0) {
-                qemu_file_set_rate_limit(s->to_dst_file, INT64_MAX);
-                qemu_savevm_state_complete_precopy(s->to_dst_file, false);
-                s->block_inactive = true;
+                if (ret >= 0) {
+                    s->block_inactive = true;
+                }
             }
         }
         qemu_mutex_unlock_iothread();