IPoIB: Rejoin all multicast groups after a port event

When ipoib_ib_dev_flush() is called because of a port event, the
driver needs to rejoin all multicast groups, since the flush will call
ipoib_mcast_dev_flush() (via ipoib_ib_dev_down()).  Otherwise no
(non-broadcast) multicast groups will be rejoined until the networking
core calls ->set_multicast_list again, and so multicast reception will
be broken for potentially a long time.
Signed-off-by: Eli Cohen <eli@mellanox.co.il>
Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/ulp/ipoib/ipoib_ib.c

@@ -631,8 +631,10 @@ void ipoib_ib_dev_flush(void *_dev)
 	 * The device could have been brought down between the start and when
 	 * we get here, don't bring it back up if it's not configured up
 	 */
-	if (test_bit(IPOIB_FLAG_ADMIN_UP, &priv->flags))
+	if (test_bit(IPOIB_FLAG_ADMIN_UP, &priv->flags)) {
 		ipoib_ib_dev_up(dev);
+		ipoib_mcast_restart_task(dev);
+	}
 
 	mutex_lock(&priv->vlan_mutex);