xfsize
m0->m_len = xfsize(i, npages, off, space);
*space -= xfsize(old - 1, old, off, *space);
*space -= xfsize(0, old, off, *space);
xfsize(i, npages, off, len))) {
xfsize(j, npages, off, len))) {
xfsize(j, npages, off, len))) {
xfs = xfsize(i, npages, off, space);