ipoib_change_mtu
int ipoib_change_mtu(struct ipoib_dev_priv *priv, int new_mtu, bool propagate);
error = -ipoib_change_mtu(priv, ifr->ifr_mtu, false);
ipoib_change_mtu(priv, min(priv->mcast_mtu, priv->admin_mtu),