D_BSIZE
error = bread(dhp->h_devvp, dbtodoff(lsn), D_BSIZE, &bp);
hpfs_breadstruct(hpmp, lsn, D_BSIZE, D_MAGIC, bpp)
error = bread(hp->h_devvp, dbtodoff(lsn), D_BSIZE, &bp);