ffs_truncate
int ffs_truncate(struct vnode *, off_t, int, struct ucred *);
if ((error = ffs_truncate(vp, (off_t)0, 0, proc0.p_ucred)) != 0)
error = ffs_truncate(vp, (off_t)0, 0, NOCRED);
(void)ffs_truncate(dvp, (off_t)dp->i_endoff, IO_SYNC, cred);
(void)ffs_truncate(vp, osize, ioflag & IO_SYNC,
error = ffs_truncate(tvp, (off_t)0, ioflag,
error = ffs_truncate(vp, (off_t)0, ioflag, cnp->cn_cred);
if ((error = ffs_truncate(vp, vap->va_size, 0, cred)) != 0)