+static void dsa_tree_migrate_ports_from_lag_master(struct dsa_switch_tree *dst,
+ struct net_device *lag_dev)
+{
+ struct net_device *new_master = dsa_tree_find_first_master(dst);
+ struct dsa_port *dp;
+ int err;
+
+ dsa_tree_for_each_user_port(dp, dst) {
+ if (dsa_port_to_master(dp) != lag_dev)
+ continue;
+
+ err = dsa_slave_change_master(dp->slave, new_master, NULL);
+ if (err) {
+ netdev_err(dp->slave,
+ "failed to restore master to %s: %pe\n",
+ new_master->name, ERR_PTR(err));
+ }
+ }
+}
+
+static int dsa_master_lag_join(struct net_device *master,
+ struct net_device *lag_dev,
+ struct netdev_lag_upper_info *uinfo,
+ struct netlink_ext_ack *extack)
+{
+ struct dsa_port *cpu_dp = master->dsa_ptr;
+ struct dsa_switch_tree *dst = cpu_dp->dst;
+ struct dsa_port *dp;
+ int err;
+
+ err = dsa_master_lag_setup(lag_dev, cpu_dp, uinfo, extack);
+ if (err)
+ return err;
+
+ dsa_tree_for_each_user_port(dp, dst) {
+ if (dsa_port_to_master(dp) != master)
+ continue;
+
+ err = dsa_slave_change_master(dp->slave, lag_dev, extack);
+ if (err)
+ goto restore;
+ }
+
+ return 0;
+
+restore:
+ dsa_tree_for_each_user_port_continue_reverse(dp, dst) {
+ if (dsa_port_to_master(dp) != lag_dev)
+ continue;
+
+ err = dsa_slave_change_master(dp->slave, master, NULL);
+ if (err) {
+ netdev_err(dp->slave,
+ "failed to restore master to %s: %pe\n",
+ master->name, ERR_PTR(err));
+ }
+ }
+
+ dsa_master_lag_teardown(lag_dev, master->dsa_ptr);
+
+ return err;
+}
+
+static void dsa_master_lag_leave(struct net_device *master,
+ struct net_device *lag_dev)
+{
+ struct dsa_port *dp, *cpu_dp = lag_dev->dsa_ptr;
+ struct dsa_switch_tree *dst = cpu_dp->dst;
+ struct dsa_port *new_cpu_dp = NULL;
+ struct net_device *lower;
+ struct list_head *iter;
+
+ netdev_for_each_lower_dev(lag_dev, lower, iter) {
+ if (netdev_uses_dsa(lower)) {
+ new_cpu_dp = lower->dsa_ptr;
+ break;
+ }
+ }
+
+ if (new_cpu_dp) {
+ /* Update the CPU port of the user ports still under the LAG
+ * so that dsa_port_to_master() continues to work properly
+ */
+ dsa_tree_for_each_user_port(dp, dst)
+ if (dsa_port_to_master(dp) == lag_dev)
+ dp->cpu_dp = new_cpu_dp;
+
+ /* Update the index of the virtual CPU port to match the lowest
+ * physical CPU port
+ */
+ lag_dev->dsa_ptr = new_cpu_dp;
+ wmb();
+ } else {
+ /* If the LAG DSA master has no ports left, migrate back all
+ * user ports to the first physical CPU port
+ */
+ dsa_tree_migrate_ports_from_lag_master(dst, lag_dev);
+ }
+
+ /* This DSA master has left its LAG in any case, so let
+ * the CPU port leave the hardware LAG as well
+ */
+ dsa_master_lag_teardown(lag_dev, master->dsa_ptr);
+}
+
+static int dsa_master_changeupper(struct net_device *dev,
+ struct netdev_notifier_changeupper_info *info)
+{
+ struct netlink_ext_ack *extack;
+ int err = NOTIFY_DONE;
+
+ if (!netdev_uses_dsa(dev))
+ return err;
+
+ extack = netdev_notifier_info_to_extack(&info->info);
+
+ if (netif_is_lag_master(info->upper_dev)) {
+ if (info->linking) {
+ err = dsa_master_lag_join(dev, info->upper_dev,
+ info->upper_info, extack);
+ err = notifier_from_errno(err);
+ } else {
+ dsa_master_lag_leave(dev, info->upper_dev);
+ err = NOTIFY_OK;
+ }
+ }
+
+ return err;
+}
+