static int bond_change_mtu(struct net_device *bond_dev, int new_mtu)
{
	struct bonding *bond = netdev_priv(bond_dev);
	struct slave *slave, *stop_at;
	int res = 0;
	int i;

	pr_debug("bond=%p, name=%s, new_mtu=%d\n", bond,
		 (bond_dev ? bond_dev->name : "None"), new_mtu);

	/* Can't hold bond->lock with bh disabled here since
	 * some base drivers panic. On the other hand we can't
	 * hold bond->lock without bh disabled because we'll
	 * deadlock. The only solution is to rely on the fact
	 * that we're under rtnl_lock here, and the slaves
	 * list won't change. This doesn't solve the problem
	 * of setting the slave's MTU while it is
	 * transmitting, but the assumption is that the base
	 * driver can handle that.
	 *
	 * TODO: figure out a way to safely iterate the slaves
	 * list, but without holding a lock around the actual
	 * call to the base driver.
	 */

	bond_for_each_slave(bond, slave, i) {
		pr_debug("s %p s->p %p c_m %p\n",
			 slave,
			 slave->prev,
			 slave->dev->netdev_ops->ndo_change_mtu);

		res = dev_set_mtu(slave->dev, new_mtu);

		if (res) {
			/* If we failed to set the slave's mtu to the new value
			 * we must abort the operation even in ACTIVE_BACKUP
			 * mode, because if we allow the backup slaves to have
			 * different mtu values than the active slave we'll
			 * need to change their mtu when doing a failover. That
			 * means changing their mtu from timer context, which
			 * is probably not a good idea.
			 */
			pr_debug("err %d %s\n", res, slave->dev->name);
			goto unwind;
		}
	}

	bond_dev->mtu = new_mtu;

	return 0;

unwind:
	/* unwind from head to the slave that failed */
	stop_at = slave;
	bond_for_each_slave_from_to(bond, slave, i, bond->first_slave, stop_at) {
		int tmp_res;

		tmp_res = dev_set_mtu(slave->dev, bond_dev->mtu);
		if (tmp_res) {
			pr_debug("unwind err %d dev %s\n",
				 tmp_res, slave->dev->name);
		}
	}

	return res;
}
static int bond_change_mtu(struct net_device *bond_dev, int new_mtu)
{
	struct bonding *bond = netdev_priv(bond_dev);
	struct slave *slave, *stop_at;
	int res = 0;
	int i;

	pr_debug("bond=%p, name=%s, new_mtu=%d\n", bond,
		 (bond_dev ? bond_dev->name : "None"), new_mtu);

	 

	bond_for_each_slave(bond, slave, i) {
		pr_debug("s %p s->p %p c_m %p\n",
			 slave,
			 slave->prev,
			 slave->dev->netdev_ops->ndo_change_mtu);

		res = dev_set_mtu(slave->dev, new_mtu);

		if (res) {
			 
			pr_debug("err %d %s\n", res, slave->dev->name);
			goto unwind;
		}
	}

	bond_dev->mtu = new_mtu;

	return 0;

unwind:
	 
	stop_at = slave;
	bond_for_each_slave_from_to(bond, slave, i, bond->first_slave, stop_at) {
		int tmp_res;

		tmp_res = dev_set_mtu(slave->dev, bond_dev->mtu);
		if (tmp_res) {
			pr_debug("unwind err %d dev %s\n",
				 tmp_res, slave->dev->name);
		}
	}

	return res;
}