VI_WRMAP
if ((vp->v_iflag & (VI_TEXT|VI_EXECMAP|VI_WRMAP)) != 0 ||
vp->v_iflag &= ~(VI_TEXT|VI_EXECMAP|VI_WRMAP);
needwritemap = (vp->v_iflag & VI_WRMAP) == 0 &&
vp->v_iflag |= VI_WRMAP;
if (modified && (vp->v_iflag & VI_WRMAP) != 0 &&