storage: use enum for snapshot driver type

This is the last use of raw strings for disk formats throughout
the src/conf directory.

* src/conf/snapshot_conf.h (_virDomainSnapshotDiskDef): Store enum
rather than string for disk type.
* src/conf/snapshot_conf.c (virDomainSnapshotDiskDefClear)
(virDomainSnapshotDiskDefParseXML, virDomainSnapshotDefFormat):
Adjust users.
* src/qemu/qemu_driver.c (qemuDomainSnapshotDiskPrepare)
(qemuDomainSnapshotCreateSingleDiskActive): Likewise.

src/conf/snapshot_conf.c

@@ -82,7 +82,6 @@ virDomainSnapshotDiskDefClear(virDomainSnapshotDiskDefPtr disk)
 {
     VIR_FREE(disk->name);
     VIR_FREE(disk->file);
-    VIR_FREE(disk->driverType);
 }
 
 void virDomainSnapshotDefFree(virDomainSnapshotDefPtr def)
@@ -134,15 +133,24 @@ virDomainSnapshotDiskDefParseXML(xmlNodePtr node,
             if (!def->file &&
                 xmlStrEqual(cur->name, BAD_CAST "source")) {
                 def->file = virXMLPropString(cur, "file");
-            } else if (!def->driverType &&
+            } else if (!def->format &&
                        xmlStrEqual(cur->name, BAD_CAST "driver")) {
-                def->driverType = virXMLPropString(cur, "type");
+                char *driver = virXMLPropString(cur, "type");
+                def->format = virStorageFileFormatTypeFromString(driver);
+                if (def->format <= 0) {
+                    virReportError(VIR_ERR_INTERNAL_ERROR,
+                                   _("unknown disk snapshot driver '%s'"),
+                                   driver);
+                    VIR_FREE(driver);
+                    goto cleanup;
+                }
+                VIR_FREE(driver);
             }
         }
         cur = cur->next;
     }
 
-    if (!def->snapshot && (def->file || def->driverType))
+    if (!def->snapshot && (def->file || def->format))
         def->snapshot = VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL;
 
     ret = 0;
@@ -536,11 +544,12 @@ char *virDomainSnapshotDefFormat(const char *domain_uuid,
             if (disk->snapshot)
                 virBufferAsprintf(&buf, " snapshot='%s'",
                                   virDomainSnapshotLocationTypeToString(disk->snapshot));
-            if (disk->file || disk->driverType) {
+            if (disk->file || disk->format > 0) {
                 virBufferAddLit(&buf, ">\n");
-                if (disk->driverType)
+                if (disk->format > 0)
                     virBufferEscapeString(&buf, "      <driver type='%s'/>\n",
-                                          disk->driverType);
+                                          virStorageFileFormatTypeToString(
+                                              disk->format));
                 if (disk->file)
                     virBufferEscapeString(&buf, "      <source file='%s'/>\n",
                                           disk->file);

src/conf/snapshot_conf.h

@@ -52,7 +52,7 @@ struct _virDomainSnapshotDiskDef {
     int index; /* index within snapshot->dom->disks that matches name */
     int snapshot; /* enum virDomainSnapshotLocation */
     char *file; /* new source file when snapshot is external */
-    char *driverType; /* file format type of new file */
+    int format; /* enum virStorageFileFormat */
 };
 
 /* Stores the complete snapshot metadata */

src/qemu/qemu_driver.c

@@ -10681,17 +10681,15 @@ qemuDomainSnapshotDiskPrepare(virDomainObjPtr vm, virDomainSnapshotDefPtr def,
             break;
 
         case VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL:
-            if (!disk->driverType) {
-                if (!(disk->driverType = strdup("qcow2"))) {
-                    virReportOOMError();
-                    goto cleanup;
-                }
-            } else if (STRNEQ(disk->driverType, "qcow2") &&
-                       STRNEQ(disk->driverType, "qed")) {
+            if (!disk->format) {
+                disk->format = VIR_STORAGE_FILE_QCOW2;
+            } else if (disk->format != VIR_STORAGE_FILE_QCOW2 &&
+                       disk->format != VIR_STORAGE_FILE_QED) {
                 virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                                _("external snapshot format for disk %s "
                                  "is unsupported: %s"),
-                               disk->name, disk->driverType);
+                               disk->name,
+                               virStorageFileFormatTypeToString(disk->format));
                 goto cleanup;
             }
             if (stat(disk->file, &st) < 0) {
@@ -10761,7 +10759,8 @@ qemuDomainSnapshotCreateSingleDiskActive(struct qemud_driver *driver,
     qemuDomainObjPrivatePtr priv = vm->privateData;
     char *device = NULL;
     char *source = NULL;
-    int format = VIR_STORAGE_FILE_NONE;
+    int format = snap->format;
+    const char *formatStr = NULL;
     char *persistSource = NULL;
     int ret = -1;
     int fd = -1;
@@ -10775,15 +10774,6 @@ qemuDomainSnapshotCreateSingleDiskActive(struct qemud_driver *driver,
         return -1;
     }
 
-    if (snap->driverType) {
-        format = virStorageFileFormatTypeFromString(snap->driverType);
-        if (format <= 0) {
-            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
-                           _("unknown driver type %s"), snap->driverType);
-            goto cleanup;
-        }
-    }
-
     if (virAsprintf(&device, "drive-%s", disk->info.alias) < 0 ||
         !(source = strdup(snap->file)) ||
         (persistDisk &&
@@ -10829,8 +10819,10 @@ qemuDomainSnapshotCreateSingleDiskActive(struct qemud_driver *driver,
     disk->format = origdriver;
 
     /* create the actual snapshot */
+    if (snap->format)
+        formatStr = virStorageFileFormatTypeToString(snap->format);
     ret = qemuMonitorDiskSnapshot(priv->mon, actions, device, source,
-                                  snap->driverType, reuse);
+                                  formatStr, reuse);
     virDomainAuditDisk(vm, disk->src, source, "snapshot", ret >= 0);
     if (ret < 0)
         goto cleanup;