qapi: add name parameter to nbd-server-add

Allow user to specify name for new export, to not reuse internal
node name and to not show it to clients.

This also allows creating several exports per device.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180119135719.24745-2-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

blockdev-nbd.c

@@ -140,8 +140,8 @@ void qmp_nbd_server_start(SocketAddressLegacy *addr,
     qapi_free_SocketAddress(addr_flat);
 }
 
-void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
-                        Error **errp)
+void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
+                        bool has_writable, bool writable, Error **errp)
 {
     BlockDriverState *bs = NULL;
     BlockBackend *on_eject_blk;
@@ -152,8 +152,12 @@ void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
         return;
     }
 
-    if (nbd_export_find(device)) {
-        error_setg(errp, "NBD server already exporting device '%s'", device);
+    if (!has_name) {
+        name = device;
+    }
+
+    if (nbd_export_find(name)) {
+        error_setg(errp, "NBD server already has export named '%s'", name);
         return;
     }
 
@@ -177,7 +181,7 @@ void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
         return;
     }
 
-    nbd_export_set_name(exp, device);
+    nbd_export_set_name(exp, name);
 
     /* The list of named exports has a strong reference to this export now and
      * our only way of accessing it is through nbd_export_find(), so we can drop

hmp.c

@@ -2203,7 +2203,8 @@ void hmp_nbd_server_start(Monitor *mon, const QDict *qdict)
             continue;
         }
 
-        qmp_nbd_server_add(info->value->device, true, writable, &local_err);
+        qmp_nbd_server_add(info->value->device, false, NULL,
+                           true, writable, &local_err);
 
         if (local_err != NULL) {
             qmp_nbd_server_stop(NULL);
@@ -2223,7 +2224,7 @@ void hmp_nbd_server_add(Monitor *mon, const QDict *qdict)
     bool writable = qdict_get_try_bool(qdict, "writable", false);
     Error *local_err = NULL;
 
-    qmp_nbd_server_add(device, true, writable, &local_err);
+    qmp_nbd_server_add(device, false, NULL, true, writable, &local_err);
 
     if (local_err != NULL) {
         hmp_handle_error(mon, &local_err);

qapi/block.json

@@ -213,14 +213,19 @@
 #
 # @device: The device name or node name of the node to be exported
 #
+# @name: Export name. If unspecified, the @device parameter is used as the
+#        export name. (Since 2.12)
+#
 # @writable: Whether clients should be able to write to the device via the
 #     NBD connection (default false).
 #
-# Returns: error if the device is already marked for export.
+# Returns: error if the server is not running, or export with the same name
+#          already exists.
 #
 # Since: 1.3.0
 ##
-{ 'command': 'nbd-server-add', 'data': {'device': 'str', '*writable': 'bool'} }
+{ 'command': 'nbd-server-add',
+  'data': {'device': 'str', '*name': 'str', '*writable': 'bool'} }
 
 ##
 # @nbd-server-stop: