netpoll: cleanup sparse warnings

With my recent commit I introduced two sparse warnings.  Looking closer there
were a few more in the same file, so I fixed them all up.  Basic rcu pointer
dereferencing suff.

I've validated these changes using CONFIG_PROVE_RCU while starting and stopping
netconsole repeatedly in bonded and non-bonded configurations

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: fengguang.wu@intel.com
CC: David Miller <davem@davemloft.net>
CC: eric.dumazet@gmail.com

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 4 deletions

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index c536474e2260..bcfd4f4599a5 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -206,7 +206,7 @@ static void netpoll_poll_dev(struct net_device *dev)
          * the dev_open/close paths use this to block netpoll activity
          * while changing device state
          */
-        if (!mutex_trylock(&dev->npinfo->dev_lock))
+        if (!mutex_trylock(&ni->dev_lock))
                 return;
 
         if (!dev || !netif_running(dev))
@@ -221,7 +221,7 @@ static void netpoll_poll_dev(struct net_device *dev)
 
         poll_napi(dev);
 
-        mutex_unlock(&dev->npinfo->dev_lock);
+        mutex_unlock(&ni->dev_lock);
 
         if (dev->flags & IFF_SLAVE) {
                 if (ni) {
@@ -1056,7 +1056,7 @@ int __netpoll_setup(struct netpoll *np, struct net_device *ndev, gfp_t gfp)
                                 goto free_npinfo;
                 }
         } else {
-                npinfo = ndev->npinfo;
+                npinfo = rtnl_dereference(ndev->npinfo);
                 atomic_inc(&npinfo->refcnt);
         }
 
@@ -1236,7 +1236,11 @@ void __netpoll_cleanup(struct netpoll *np)
         struct netpoll_info *npinfo;
         unsigned long flags;
 
-        npinfo = np->dev->npinfo;
+        /* rtnl_dereference would be preferable here but
+         * rcu_cleanup_netpoll path can put us in here safely without
+         * holding the rtnl, so plain rcu_dereference it is
+         */
+        npinfo = rtnl_dereference(np->dev->npinfo);
         if (!npinfo)
                 return;