spec_startio
static struct buf *spec_startio(struct vnode *, page_t *, u_offset_t, size_t,
bp = spec_startio(vp, pp, io_off1, io_len1,
(void) spec_startio(vp, pp2, io_off2, io_len2,
bp = spec_startio(vp, pp, io_off, io_len, B_WRITE | flags);
bp = spec_startio(vp, pp, io_off, io_len, flags);