vn_ioctl
struct vn_ioctl vnio;
static int vniocattach_file (struct vn_softc *, struct vn_ioctl *, cdev_t dev, int flag, struct ucred *cred);
static int vniocattach_swap (struct vn_softc *, struct vn_ioctl *, cdev_t dev, int flag, struct ucred *cred);
struct vn_ioctl *vio;
vio = (struct vn_ioctl *)ap->a_data;
vniocattach_file(struct vn_softc *vn, struct vn_ioctl *vio, cdev_t dev,
vniocattach_swap(struct vn_softc *vn, struct vn_ioctl *vio, cdev_t dev,
static int vn_ioctl (struct file *fp, u_long com, caddr_t data,
.fo_ioctl = vn_ioctl,
#define VNIOCATTACH _IOWR('F', 0, struct vn_ioctl) /* attach file */
#define VNIOCDETACH _IOWR('F', 1, struct vn_ioctl) /* detach disk */
struct vn_ioctl vnio;