Refactor ESX storage driver to implement facade pattern

The patch refactors the current ESX storage driver due to following reasons:

1. Given most of the public APIs exposed by the storage driver in Libvirt
remains same, ESX storage driver should not implement logic specific
for only one supported format (current implementation only supports VMFS).
2. Decoupling interface from specific storage implementation gives us an
extensible design to hook implementation for other supported storage
formats.

This patch refactors the current driver to implement it as a facade pattern i.e.
the driver exposes all the public libvirt APIs, but uses backend drivers to get
the required task done. The backend drivers provide implementation specific to
the type of storage device.

File changes:
------------------
esx_storage_driver.c ----> esx_storage_driver.c (base storage driver)
                     |
                     |---> esx_storage_backend_vmfs.c (VMFS backend)

po/POTFILES.in

@@ -32,6 +32,7 @@ src/datatypes.c
 src/driver.c
 src/esx/esx_driver.c
 src/esx/esx_network_driver.c
+src/esx/esx_storage_backend_vmfs.c
 src/esx/esx_storage_driver.c
 src/esx/esx_util.c
 src/esx/esx_vi.c

src/Makefile.am

@@ -493,6 +493,7 @@ ESX_DRIVER_SOURCES =							\
 		esx/esx_interface_driver.c esx/esx_interface_driver.h	\
 		esx/esx_network_driver.c esx/esx_network_driver.h	\
 		esx/esx_storage_driver.c esx/esx_storage_driver.h	\
+		esx/esx_storage_backend_vmfs.c esx/esx_storage_backend_vmfs.h	\
 		esx/esx_device_monitor.c esx/esx_device_monitor.h	\
 		esx/esx_secret_driver.c esx/esx_secret_driver.h		\
 		esx/esx_nwfilter_driver.c esx/esx_nwfilter_driver.h	\

src/esx/esx_driver.c

@@ -163,7 +163,8 @@ esxParseVMXFileName(const char *fileName, void *opaque)
             datastoreName = NULL;
 
             if (esxVI_LookupDatastoreHostMount(data->ctx, datastore->obj,
-                                               &hostMount) < 0 ||
+                                               &hostMount,
+                                               esxVI_Occurrence_RequiredItem) < 0 ||
                 esxVI_GetStringValue(datastore, "summary.name", &datastoreName,
                                      esxVI_Occurrence_RequiredItem) < 0) {
                 goto cleanup;
@@ -307,7 +308,8 @@ esxFormatVMXFileName(const char *fileName, void *opaque)
         if (esxVI_LookupDatastoreByName(data->ctx, datastoreName, NULL, &datastore,
                                         esxVI_Occurrence_RequiredItem) < 0 ||
             esxVI_LookupDatastoreHostMount(data->ctx, datastore->obj,
-                                           &hostMount) < 0) {
+                                           &hostMount,
+                                           esxVI_Occurrence_RequiredItem) < 0) {
             goto cleanup;
         }
 

src/esx/esx_storage_backend_vmfs.h

+
+/*
+ * esx_storage_backend_vmfs.h: ESX storage driver backend for
+ *                             managing VMFS datastores
+ *
+ * Copyright (C) 2012 Ata E Husain Bohra <ata.husain@hotmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef __ESX_STORAGE_BACKEND_VMFS_H__
+# define __ESX_STORAGE_BACKEND_VMFS_H__
+
+# include "driver.h"
+
+extern virStorageDriver esxStorageBackendVMFS;
+
+#endif /* __ESX_STORAGE_BACKEND_VMFS_H__ */

src/esx/esx_vi.c

@@ -3107,7 +3107,8 @@ esxVI_LookupDatastoreByAbsolutePath(esxVI_Context *ctx,
 int
 esxVI_LookupDatastoreHostMount(esxVI_Context *ctx,
                                esxVI_ManagedObjectReference *datastore,
-                               esxVI_DatastoreHostMount **hostMount)
+                               esxVI_DatastoreHostMount **hostMount,
+                               esxVI_Occurrence occurrence)
 {
     int result = -1;
     esxVI_String *propertyNameList = NULL;
@@ -3155,7 +3156,7 @@ esxVI_LookupDatastoreHostMount(esxVI_Context *ctx,
         break;
     }
 
-    if (*hostMount == NULL) {
+    if (*hostMount == NULL && occurrence == esxVI_Occurrence_RequiredItem) {
         virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                        _("Could not lookup datastore host mount"));
         goto cleanup;

src/esx/esx_vi.h

@@ -441,7 +441,8 @@ int esxVI_LookupDatastoreByAbsolutePath(esxVI_Context *ctx,
 
 int esxVI_LookupDatastoreHostMount(esxVI_Context *ctx,
                                    esxVI_ManagedObjectReference *datastore,
-                                   esxVI_DatastoreHostMount **hostMount);
+                                   esxVI_DatastoreHostMount **hostMount,
+                                   esxVI_Occurrence occurrence);
 
 int esxVI_LookupTaskInfoByTask(esxVI_Context *ctx,
                                esxVI_ManagedObjectReference *task,