nbd: Allow description when creating NBD blockdev

Allow blockdevs to match the feature already present in qemu-nbd -D.
Enhance iotest 223 to cover it.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20191114024635.11363-5-eblake@redhat.com>

blockdev-nbd.c

@@ -144,6 +144,7 @@ void qmp_nbd_server_start(SocketAddressLegacy *addr,
 }
 
 void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
+                        bool has_description, const char *description,
                         bool has_writable, bool writable,
                         bool has_bitmap, const char *bitmap, Error **errp)
 {
@@ -167,6 +168,11 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
         return;
     }
 
+    if (has_description && strlen(description) > NBD_MAX_STRING_SIZE) {
+        error_setg(errp, "description '%s' too long", description);
+        return;
+    }
+
     if (nbd_export_find(name)) {
         error_setg(errp, "NBD server already has export named '%s'", name);
         return;
@@ -195,7 +201,8 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
         writable = false;
     }
 
-    exp = nbd_export_new(bs, 0, len, name, NULL, bitmap, !writable, !writable,
+    exp = nbd_export_new(bs, 0, len, name, description, bitmap,
+                         !writable, !writable,
                          NULL, false, on_eject_blk, errp);
     if (!exp) {
         goto out;

monitor/hmp-cmds.c

@@ -2351,7 +2351,7 @@ void hmp_nbd_server_start(Monitor *mon, const QDict *qdict)
             continue;
         }
 
-        qmp_nbd_server_add(info->value->device, false, NULL,
+        qmp_nbd_server_add(info->value->device, false, NULL, false, NULL,
                            true, writable, false, NULL, &local_err);
 
         if (local_err != NULL) {
@@ -2373,7 +2373,7 @@ 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, !!name, name, true, writable,
+    qmp_nbd_server_add(device, !!name, name, false, NULL, true, writable,
                        false, NULL, &local_err);
     hmp_handle_error(mon, local_err);
 }

qapi/block.json

@@ -250,9 +250,12 @@
 # @name: Export name. If unspecified, the @device parameter is used as the
 #        export name. (Since 2.12)
 #
+# @description: Free-form description of the export, up to 4096 bytes.
+#               (Since 5.0)
+#
 # @writable: Whether clients should be able to write to the device via the
 #     NBD connection (default false).
-
+#
 # @bitmap: Also export the dirty bitmap reachable from @device, so the
 #          NBD client can use NBD_OPT_SET_META_CONTEXT with
 #          "qemu:dirty-bitmap:NAME" to inspect the bitmap. (since 4.0)
@@ -263,8 +266,8 @@
 # Since: 1.3.0
 ##
 { 'command': 'nbd-server-add',
-  'data': {'device': 'str', '*name': 'str', '*writable': 'bool',
-           '*bitmap': 'str' } }
+  'data': {'device': 'str', '*name': 'str', '*description': 'str',
+           '*writable': 'bool', '*bitmap': 'str' } }
 
 ##
 # @NbdServerRemoveMode:

tests/qemu-iotests/223

@@ -153,7 +153,7 @@ _send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-add",
   "bitmap":"b3"}}' "error" # Missing bitmap
 _send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-add",
   "arguments":{"device":"n", "name":"n2", "writable":true,
-  "bitmap":"b2"}}' "return"
+  "description":"some text", "bitmap":"b2"}}' "return"
 $QEMU_NBD_PROG -L -k "$SOCK_DIR/nbd"
 
 echo

tests/qemu-iotests/223.out

@@ -50,7 +50,7 @@ exports available: 0
 {"error": {"class": "GenericError", "desc": "Enabled bitmap 'b2' incompatible with readonly export"}}
 {"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "bitmap":"b3"}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'b3' is not found"}}
-{"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "writable":true, "bitmap":"b2"}}
+{"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "writable":true, "description":"some text", "bitmap":"b2"}}
 {"return": {}}
 exports available: 2
  export: 'n'
@@ -63,6 +63,7 @@ exports available: 2
    base:allocation
    qemu:dirty-bitmap:b
  export: 'n2'
+  description: some text
   size:  4194304
   flags: 0xced ( flush fua trim zeroes df cache fast-zero )
   min block: 1
@@ -130,7 +131,7 @@ exports available: 0
 {"error": {"class": "GenericError", "desc": "Enabled bitmap 'b2' incompatible with readonly export"}}
 {"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "bitmap":"b3"}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'b3' is not found"}}
-{"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "writable":true, "bitmap":"b2"}}
+{"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "writable":true, "description":"some text", "bitmap":"b2"}}
 {"return": {}}
 exports available: 2
  export: 'n'
@@ -143,6 +144,7 @@ exports available: 2
    base:allocation
    qemu:dirty-bitmap:b
  export: 'n2'
+  description: some text
   size:  4194304
   flags: 0xced ( flush fua trim zeroes df cache fast-zero )
   min block: 1