SDEV_SUBDIR
spp->sp_nflags |= SDEV_SUBDIR;
if (spp->sp_nflags & SDEV_SUBDIR) {
devzvol_validate, SDEV_ZONED | SDEV_DYNAMIC | SDEV_VTOR | SDEV_SUBDIR },
SDEV_DYNAMIC | SDEV_VTOR | SDEV_SUBDIR },