tipc: remove TIPC usage of field af_packet_priv in struct net_device

TIPC is currently using the field 'af_packet_priv' in struct net_device
as a handle to find the bearer instance associated to the given network
device. But, by doing so it is blocking other networking cleanups, such
as the one discussed here:

http://patchwork.ozlabs.org/patch/178044/

This commit removes this usage from TIPC. Instead, we introduce a new
field, 'tipc_ptr', to the net_device structure, to serve this purpose.
When TIPC bearer is enabled, the bearer object is associated to
'tipc_ptr'. When a TIPC packet arrives in the recv_msg() upcall
from a networking device, the bearer object can now be obtained from
'tipc_ptr'. When a bearer is disabled, the bearer object is detached
from its underlying network device by setting 'tipc_ptr' to NULL.

Additionally, an RCU lock is used to protect the new pointer.
Henceforth, the existing tipc_net_lock is used in write mode to
serialize write accesses to this pointer, while the new RCU lock is
applied on the read side to ensure that the pointer is 100% valid
within its wrapped area for all readers.

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Cc: Patrick McHardy <kaber@trash.net>
Reviewed-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 9d55e5188b96..0ca8100f9fbc 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1283,6 +1283,9 @@ struct net_device {
 #if IS_ENABLED(CONFIG_NET_DSA)
 	struct dsa_switch_tree	*dsa_ptr;	/* dsa specific data */
 #endif
+#if IS_ENABLED(CONFIG_TIPC)
+	struct tipc_bearer __rcu *tipc_ptr;	/* TIPC specific data */
+#endif
 	void 			*atalk_ptr;	/* AppleTalk link 	*/
 	struct in_device __rcu	*ip_ptr;	/* IPv4 specific data	*/
 	struct dn_dev __rcu     *dn_ptr;        /* DECnet specific data */