Function vdev_is_dead

freebsd/contrib/openzfs/module/zfs/vdev.c:4009–4022

}

boolean_t
vdev_is_dead(vdev_t *vd)
{
	/*
	 * Holes and missing devices are always considered "dead".
	 * This simplifies the code since we don't have to check for
	 * these types of devices in the various code paths.
	 * Instead we rely on the fact that we skip over dead devices
	 * before issuing I/O to them.
	 */
	return (vd->vdev_state < VDEV_STATE_DEGRADED ||
	    vd->vdev_ops == &vdev_hole_ops ||
	    vd->vdev_ops == &vdev_missing_ops);
}

boolean_t
vdev_readable(vdev_t *vd)