Revert "IPoIB: Consolidate rtnl_lock tasks in workqueue"

This reverts commit afe1de66.

The series of IPoIB bug fixes that went into 3.19-rc1 introduce
regressions, and after trying to sort things out, we decided to revert
to 3.18's IPoIB driver and get things right for 3.20.
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/ulp/ipoib/ipoib_multicast.c

@@ -190,6 +190,12 @@ static int ipoib_mcast_join_finish(struct ipoib_mcast *mcast,
 		spin_unlock_irq(&priv->lock);
 		priv->tx_wr.wr.ud.remote_qkey = priv->qkey;
 		set_qkey = 1;
+
+		if (!ipoib_cm_admin_enabled(dev)) {
+			rtnl_lock();
+			dev_set_mtu(dev, min(priv->mcast_mtu, priv->admin_mtu));
+			rtnl_unlock();
+		}
 	}
 
 	if (!test_bit(IPOIB_MCAST_FLAG_SENDONLY, &mcast->flags)) {
@@ -365,8 +371,6 @@ void ipoib_mcast_carrier_on_task(struct work_struct *work)
 	}
 
 	rtnl_lock();
-	if (!ipoib_cm_admin_enabled(priv->dev))
-		dev_set_mtu(priv->dev, min(priv->mcast_mtu, priv->admin_mtu));
 	netif_carrier_on(priv->dev);
 	rtnl_unlock();
 }