modules/btrfs: add GetDefaultSubvolumeID

libblockdev provides a method to get the default subvolume id since
2014, with no way to change it. This method does not require any
administrative privileges but requires it for setting.

modules/btrfs/data/org.freedesktop.UDisks2.btrfs.xml

@@ -219,6 +219,20 @@
  <arg name="options" type="a{sv}" direction="in"/>
  </method>
 
+ <!--
+ GetDefaultSubvolumeID:
+ @options: Additional options.
+ @since: 2.11.0
+
+ Returns the default subvolume id.
+
+ No additional options are currently defined.
+ -->
+ <method name="GetDefaultSubvolumeID">
+ <arg name="id" direction="out" type="u"/>
+ <arg name="options" type="a{sv}" direction="in"/>
+ </method>
+
  <property name="label" type="s" access="read"/>
  <property name="uuid" type="s" access="read"/>
  <property name="num_devices" type="t" access="read"/>

modules/btrfs/udiskslinuxfilesystembtrfs.c

@@ -660,6 +660,51 @@ handle_get_subvolumes (UDisksFilesystemBTRFS *fs_btrfs,
  return TRUE;
 }
 
+static gboolean
+handle_get_default_subvolume_id (UDisksFilesystemBTRFS *fs_btrfs,
+ GDBusMethodInvocation *invocation,
+ GVariant *arg_options)
+{
+ UDisksLinuxFilesystemBTRFS *l_fs_btrfs = UDISKS_LINUX_FILESYSTEM_BTRFS (fs_btrfs);
+ UDisksLinuxBlockObject *object = NULL;
+ GError *error = NULL;
+ gchar *mount_point = NULL;
+ guint64 default_id;
+
+ object = udisks_daemon_util_dup_object (l_fs_btrfs, &error);
+ if (! object)
+ {
+ g_dbus_method_invocation_take_error (invocation, error);
+ goto out;
+ }
+
+ /* Get the mount point for this volume. */
+ mount_point = udisks_filesystem_btrfs_get_first_mount_point (fs_btrfs, &error);
+ if (! mount_point)
+ {
+ g_dbus_method_invocation_take_error (invocation, error);
+ goto out;
+ }
+
+ default_id = bd_btrfs_get_default_subvolume_id (mount_point, &error);
+ if (! default_id && error)
+ {
+ g_dbus_method_invocation_take_error (invocation, error);
+ goto out;
+ }
+
+ /* Complete DBus call. */
+ udisks_filesystem_btrfs_complete_get_default_subvolume_id (fs_btrfs, invocation, default_id);
+
+out:
+ /* Release the resources */
+ g_clear_object (&object);
+ g_free (mount_point);
+
+ /* Indicate that we handled the method invocation */
+ return TRUE;
+}
+
 static gboolean
 handle_create_snapshot (UDisksFilesystemBTRFS *fs_btrfs,
  GDBusMethodInvocation *invocation,
@@ -849,6 +894,7 @@ udisks_linux_filesystem_btrfs_iface_init (UDisksFilesystemBTRFSIface *iface)
  iface->handle_create_subvolume = handle_create_subvolume;
  iface->handle_remove_subvolume = handle_remove_subvolume;
  iface->handle_get_subvolumes = handle_get_subvolumes;
+ iface->handle_get_default_subvolume_id = handle_get_default_subvolume_id;
  iface->handle_create_snapshot = handle_create_snapshot;
  iface->handle_repair = handle_repair;
  iface->handle_resize = handle_resize;

src/tests/dbus-tests/test_btrfs.py

@@ -381,3 +381,21 @@ def test_subvolume_mount(self):
  dbus_mounts.assertLen(1) # just one mountpoint
  dbus_mnt = self.ay_to_str(dbus_mounts.value[0]) # mountpoints are arrays of bytes
  self.assertEqual(dbus_mnt, mnt_path)
+
+ def test_get_default_subvolume_id(self):
+ dev = self._get_devices(1)[0]
+ self.addCleanup(self._clean_format, dev.obj)
+
+ manager = self.get_object('/Manager')
+ manager.CreateVolume([dev.obj_path],
+ 'test_subvolume_id', 'single', 'single',
+ self.no_options,
+ dbus_interface=self.iface_prefix + '.Manager.BTRFS')
+
+ fstype = self.get_property(dev.obj, '.Block', 'IdType')
+ fstype.assertEqual('btrfs')
+
+ with self._temp_mount(dev.path):
+ default_id = dev.obj.GetDefaultSubvolumeID(self.no_options,
+ dbus_interface=self.iface_prefix + '.Filesystem.BTRFS')
+ self.assertEqual(default_id, 5)