From: Erez Shitrit <erezsh@mellanox.com>
Date: Tue, 23 May 2017 11:42:52 +0300
Subject: IB/IPoIB: Forward MTU change to driver below
Patch-mainline: v4.13-rc2
Git-commit: ed7b521d8a98c3371e3c9300df8bf3cb774d8ea6
References: bsc#1046307 FATE#322941

This patch checks if there is a driver below that
needs to be updated on the new MTU and calls it
accordingly.

Signed-off-by: Erez Shitrit <erezsh@mellanox.com>
Reviewed by: Alex Vesker <valex@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/infiniband/ulp/ipoib/ipoib_main.c |   19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

--- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
@@ -233,6 +233,7 @@ static netdev_features_t ipoib_fix_featu
 static int ipoib_change_mtu(struct net_device *dev, int new_mtu)
 {
 	struct ipoib_dev_priv *priv = ipoib_priv(dev);
+	int ret = 0;
 
 	/* dev->mtu > 2K ==> connected mode */
 	if (ipoib_cm_admin_enabled(dev)) {
@@ -256,9 +257,23 @@ static int ipoib_change_mtu(struct net_d
 		ipoib_dbg(priv, "MTU must be smaller than the underlying "
 				"link layer MTU - 4 (%u)\n", priv->mcast_mtu);
 
-	dev->mtu = min(priv->mcast_mtu, priv->admin_mtu);
+	new_mtu = min(priv->mcast_mtu, priv->admin_mtu);
 
-	return 0;
+	if (priv->rn_ops->ndo_change_mtu) {
+		bool carrier_status = netif_carrier_ok(dev);
+
+		netif_carrier_off(dev);
+
+		/* notify lower level on the real mtu */
+		ret = priv->rn_ops->ndo_change_mtu(dev, new_mtu);
+
+		if (carrier_status)
+			netif_carrier_on(dev);
+	} else {
+		dev->mtu = new_mtu;
+	}
+
+	return ret;
 }
 
 /* Called with an RCU read lock taken */