udf_do_unreserve_space
udf_do_unreserve_space(ump, udf_node, vpart_num, udf_node->uncommitted_lbs);
udf_do_unreserve_space(ump, udf_node, vpart_num, num_lb);
udf_do_unreserve_space(ump, NULL, vpart_num, 1);
void udf_do_unreserve_space(struct udf_mount *ump, struct udf_node *udf_node, uint16_t vpart_num, uint32_t num_lb);