tipc: use RCU to protect media_ptr pointer

Now the media_ptr pointer is protected with tipc_net_lock write lock
on write side; tipc_net_lock read lock is used to read side. As the
part of effort of eliminating tipc_net_lock, we decide to adjust the
locking policy of media_ptr pointer protection: on write side, RTNL
lock is use while on read side RCU read lock is applied.

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Tested-by: Erik Hugne <erik.hugne@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 3 deletions

diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
index e0625e9e2c72..c24a35114fd7 100644
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -458,7 +458,7 @@ int tipc_enable_l2_media(struct tipc_bearer *b)
                 return -ENODEV;
 
         /* Associate TIPC bearer with Ethernet bearer */
-        b->media_ptr = dev;
+        rcu_assign_pointer(b->media_ptr, dev);
         memset(b->bcast_addr.value, 0, sizeof(b->bcast_addr.value));
         memcpy(b->bcast_addr.value, dev->broadcast, b->media->hwaddr_len);
         b->bcast_addr.media_id = b->media->type_id;
@@ -477,7 +477,10 @@ int tipc_enable_l2_media(struct tipc_bearer *b)
  */
 void tipc_disable_l2_media(struct tipc_bearer *b)
 {
-        struct net_device *dev = (struct net_device *)b->media_ptr;
+        struct net_device *dev;
+
+        dev = (struct net_device *)rtnl_dereference(b->media_ptr);
+        RCU_INIT_POINTER(b->media_ptr, NULL);
         RCU_INIT_POINTER(dev->tipc_ptr, NULL);
         dev_put(dev);
 }
@@ -492,8 +495,12 @@ int tipc_l2_send_msg(struct sk_buff *buf, struct tipc_bearer *b,
                      struct tipc_media_addr *dest)
 {
         struct sk_buff *clone;
+        struct net_device *dev;
         int delta;
-        struct net_device *dev = (struct net_device *)b->media_ptr;
+
+        dev = (struct net_device *)rcu_dereference_rtnl(b->media_ptr);
+        if (!dev)
+                return 0;
 
         clone = skb_clone(buf, GFP_ATOMIC);
         if (!clone)