jffs2_sum_add_kvec
int jffs2_sum_add_kvec(struct jffs2_sb_info *c, const struct kvec *invecs,
int res = jffs2_sum_add_kvec(c, invecs, count, (uint32_t) to);
res = jffs2_sum_add_kvec(c, vecs, count, (uint32_t) to);
res = jffs2_sum_add_kvec(c, vecs, 1, (uint32_t) ofs);