i_ffs2_size
ip->i_ffs2_size = ip->i_size;
ip->i_size = ip->i_ffs2_size;
lastlbn = ffs_lblkno(fs, ip->i_ffs2_size);
if (nb != 0 && ip->i_ffs2_size >= ffs_lblktosize(fs, lbn + 1)) {
osize = ffs_fragroundup(fs, ffs_blkoff(fs, ip->i_ffs2_size));
if (ip->i_ffs2_size < ffs_lblktosize(fs, lbn + 1))