vn_truncate_locked
error = vn_truncate_locked(ctx->vp, newsz, false, cred);
error = vn_truncate_locked(vp, length, false, td->td_ucred);
error = vn_truncate_locked(vp, length, (fp->f_flag & O_FSYNC) != 0,
error = vn_truncate_locked(outvp, outoff + xfer,
error = vn_truncate_locked(outvp, *outoffp,
int vn_truncate_locked(struct vnode *vp, off_t length, bool sync,