diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 798944aa847a0351fc18aa06722e7c0c51701943..ac2ca5f75af35a060002225f7e71cda34cbcfd0d 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -1528,6 +1528,7 @@ int dsa_slave_change_mtu(struct net_device *dev, int new_mtu)
 	struct dsa_port *dp = dsa_slave_to_port(dev);
 	struct dsa_slave_priv *p = netdev_priv(dev);
 	struct dsa_switch *ds = p->dp->ds;
+	struct dsa_port *dp_iter;
 	struct dsa_port *cpu_dp;
 	int port = p->dp->index;
 	int largest_mtu = 0;
@@ -1535,31 +1536,31 @@ int dsa_slave_change_mtu(struct net_device *dev, int new_mtu)
 	int old_master_mtu;
 	int mtu_limit;
 	int cpu_mtu;
-	int err, i;
+	int err;
 
 	if (!ds->ops->port_change_mtu)
 		return -EOPNOTSUPP;
 
-	for (i = 0; i < ds->num_ports; i++) {
+	list_for_each_entry(dp_iter, &ds->dst->ports, list) {
 		int slave_mtu;
 
-		if (!dsa_is_user_port(ds, i))
+		if (!dsa_port_is_user(dp_iter))
 			continue;
 
 		/* During probe, this function will be called for each slave
 		 * device, while not all of them have been allocated. That's
 		 * ok, it doesn't change what the maximum is, so ignore it.
 		 */
-		if (!dsa_to_port(ds, i)->slave)
+		if (!dp_iter->slave)
 			continue;
 
 		/* Pretend that we already applied the setting, which we
 		 * actually haven't (still haven't done all integrity checks)
 		 */
-		if (i == port)
+		if (dp_iter == dp)
 			slave_mtu = new_mtu;
 		else
-			slave_mtu = dsa_to_port(ds, i)->slave->mtu;
+			slave_mtu = dp_iter->slave->mtu;
 
 		if (largest_mtu < slave_mtu)
 			largest_mtu = slave_mtu;