un_head_ident
if ((ul->un_chksum == ul->un_head_ident + ul->un_tail_ident) &&
if ((ul->un_chksum == ul->un_head_ident + ul->un_tail_ident) &&
if ((ul->un_chksum != ul->un_head_ident + ul->un_tail_ident) ||
if (up != NULL && up->un_head_ident == id) {
new_ident = ul->un_head_ident;
ul->un_head_ident = new_ident;
ul->un_tail_ident = ul->un_head_ident;
ul->un_head_ident = lufs_hd_genid(ul);
ul->un_tail_ident = ul->un_head_ident;
new_ident = ul->un_head_ident + (end_blkno - beg_blkno);
new_ident = ul->un_head_ident + (end_blkno - beg_blkno);
ident = ul->un_head_ident;