i_blkno
xi->i_blkno = bp->b_lblkno >> (bd->d_blkshift - DEV_BSHIFT);
xi->i_blkno = d_blkno + pstart;
xi->i_blkno = lblkno + p_lba;
xi->i_blkno = start;
xi->i_blkno += xi->i_nblks;