chunk_io
return chunk_io(ps, ps->area, chunk, opf, 0);
return chunk_io(ps, ps->zero_area, area_location(ps, area),
r = chunk_io(ps, ps->header_area, 0, REQ_OP_READ, 1);
return chunk_io(ps, ps->header_area, 0, REQ_OP_WRITE, 1);