ffs_truncate
(void)ffs_truncate(vp, osize,
error = ffs_truncate(vp, 0, IO_EXT, cred);
int ffs_truncate(struct vnode *, off_t, int, kauth_cred_t);
(void) ffs_truncate(ovp, osize,
(void) ffs_truncate(ovp, osize, ioflag & IO_SYNC, cred);
(void) ffs_truncate(vp, (off_t)0, 0, NOCRED);
.uo_truncate = ffs_truncate,