net/mlx4: Add reference counting to MAC registeration

Add reference counting to the driver MAC registeration code. This would
be needed for cases where a mac is registered from more than once, e.g
when both the host and the VM driver register the same mac, the host
for mac spoof protection purposes and the VM for its regular needs.
Signed-off-by: NRony Efraim <ronye@mellanox.com>
Signed-off-by: NOr Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/port.c

@@ -141,8 +141,9 @@ int __mlx4_register_mac(struct mlx4_dev *dev, u8 port, u64 mac)
 		}
 
 		if (mac == (MLX4_MAC_MASK & be64_to_cpu(table->entries[i]))) {
-			/* MAC already registered, Must not have duplicates */
-			err = -EEXIST;
+			/* MAC already registered, increment ref count */
+			err = i;
+			++table->refs[i];
 			goto out;
 		}
 	}
@@ -165,7 +166,7 @@ int __mlx4_register_mac(struct mlx4_dev *dev, u8 port, u64 mac)
 		table->entries[free] = 0;
 		goto out;
 	}
-
+	table->refs[free] = 1;
 	err = free;
 	++table->total;
 out:
@@ -206,12 +207,16 @@ void __mlx4_unregister_mac(struct mlx4_dev *dev, u8 port, u64 mac)
 	struct mlx4_mac_table *table = &info->mac_table;
 	int index;
 
-	index = find_index(dev, table, mac);
-
 	mutex_lock(&table->mutex);
+	index = find_index(dev, table, mac);
 
 	if (validate_index(dev, table, index))
 		goto out;
+	if (--table->refs[index]) {
+		mlx4_dbg(dev, "Have more references for index %d,"
+			 "no need to modify mac table\n", index);
+		goto out;
+	}
 
 	table->entries[index] = 0;
 	mlx4_set_port_mac_table(dev, port, table->entries);