IO_SEQMAX
if (nh->nh_seqcount > IO_SEQMAX)
nh->nh_seqcount = IO_SEQMAX;
fp->f_seqcount[UIO_READ] = MIN(IO_SEQMAX,
if (uio->uio_resid >= IO_SEQMAX * 16384)
fp->f_seqcount[rw] = IO_SEQMAX;
if (fp->f_seqcount[rw] > IO_SEQMAX)
fp->f_seqcount[rw] = IO_SEQMAX;
ioflags |= IO_SEQMAX << IO_SEQSHIFT;