From: Jakub Kicinski <jakub.kicinski@netronome.com>
Date: Sat, 2 Sep 2017 18:26:05 -0700
Subject: nfp: flower: restore RTNL locking around representor updates
Patch-mainline: v4.14-rc1
Git-commit: 9ce4fa548313f585c637aa846f7fc904b676bf43
References: bsc#1055968

When we moved to updating representors from a workqueue grabbing
the RTNL somehow got lost in the process.  Restore it, and make
sure RCU lock is not held while we are grabbing the RTNL.  RCU
protects the representor table, so since we will be under RTNL
we can drop RCU lock as soon as we find the netdev pointer.
RTNL is needed for the dev_set_mtu() call.

Fixes: 2dff19622421 ("nfp: process MTU updates from firmware flower app")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/netronome/nfp/flower/cmsg.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/net/ethernet/netronome/nfp/flower/cmsg.c
+++ b/drivers/net/ethernet/netronome/nfp/flower/cmsg.c
@@ -141,12 +141,14 @@ nfp_flower_cmsg_portmod_rx(struct nfp_ap
 	msg = nfp_flower_cmsg_get_data(skb);
 	link = msg->info & NFP_FLOWER_CMSG_PORTMOD_INFO_LINK;
 
+	rtnl_lock();
 	rcu_read_lock();
 	netdev = nfp_app_repr_get(app, be32_to_cpu(msg->portnum));
+	rcu_read_unlock();
 	if (!netdev) {
 		nfp_flower_cmsg_warn(app, "ctrl msg for unknown port 0x%08x\n",
 				     be32_to_cpu(msg->portnum));
-		rcu_read_unlock();
+		rtnl_unlock();
 		return;
 	}
 
@@ -161,7 +163,7 @@ nfp_flower_cmsg_portmod_rx(struct nfp_ap
 	} else {
 		netif_carrier_off(netdev);
 	}
-	rcu_read_unlock();
+	rtnl_unlock();
 }
 
 static void