IPoIB: Use rtnl lock/unlock when changing device flags

Use of this lock is required to synchronize changes to the netdvice's
data structs.  Also move the call to ipoib_flush_paths() after the
modification of the netdevice flags in set_mode().
Signed-off-by: Eli Cohen <eli@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/ulp/ipoib/ipoib_cm.c

@@ -1440,7 +1440,9 @@ static ssize_t set_mode(struct device *d, struct device_attribute *attr,
 		ipoib_warn(priv, "enabling connected mode "
 			   "will cause multicast packet drops\n");
 
+		rtnl_lock();
 		dev->features &= ~(NETIF_F_IP_CSUM | NETIF_F_SG | NETIF_F_TSO);
+		rtnl_unlock();
 		priv->tx_wr.send_flags &= ~IB_SEND_IP_CSUM;
 
 		ipoib_flush_paths(dev);
@@ -1449,14 +1451,16 @@ static ssize_t set_mode(struct device *d, struct device_attribute *attr,
 
 	if (!strcmp(buf, "datagram\n")) {
 		clear_bit(IPOIB_FLAG_ADMIN_CM, &priv->flags);
-		dev->mtu = min(priv->mcast_mtu, dev->mtu);
-		ipoib_flush_paths(dev);
 
+		rtnl_lock();
 		if (test_bit(IPOIB_FLAG_CSUM, &priv->flags)) {
 			dev->features |= NETIF_F_IP_CSUM | NETIF_F_SG;
 			if (priv->hca_caps & IB_DEVICE_UD_TSO)
 				dev->features |= NETIF_F_TSO;
 		}
+		dev->mtu = min(priv->mcast_mtu, dev->mtu);
+		rtnl_unlock();
+		ipoib_flush_paths(dev);
 
 		return count;
 	}

drivers/infiniband/ulp/ipoib/ipoib_multicast.c

@@ -575,8 +575,11 @@ void ipoib_mcast_join_task(struct work_struct *work)
 
 	priv->mcast_mtu = IPOIB_UD_MTU(ib_mtu_enum_to_int(priv->broadcast->mcmember.mtu));
 
-	if (!ipoib_cm_admin_enabled(dev))
+	if (!ipoib_cm_admin_enabled(dev)) {
+		rtnl_lock();
 		dev->mtu = min(priv->mcast_mtu, priv->admin_mtu);
+		rtnl_unlock();
+	}
 
 	ipoib_dbg_mcast(priv, "successfully joined all multicast groups\n");