NONDATA_JHEADS_CNT
if (c->jhead_cnt < NONDATA_JHEADS_CNT + 1 ||
c->jhead_cnt > NONDATA_JHEADS_CNT + UBIFS_MAX_JHEADS) {
c->jhead_cnt = le32_to_cpu(sup->jhead_cnt) + NONDATA_JHEADS_CNT;
c->jhead_cnt - NONDATA_JHEADS_CNT);