XBDF_NONE
if (xbd_flag != XBDF_NONE && (sc->xbd_flags & xbd_flag) == 0)
xbd_freeze(sc, XBDF_NONE);
xbd_thaw(sc, XBDF_NONE);
if (xbd_flag != XBDF_NONE && (sc->xbd_flags & xbd_flag) != 0)