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, 32 insertions, 23 deletions

diff --git a/net/tipc/eth_media.c b/net/tipc/eth_media.c
index 37fb145476ec..c5f685dee15b 100644
--- a/net/tipc/eth_media.c
+++ b/net/tipc/eth_media.c
@@ -63,6 +63,9 @@ static int eth_started;
 
 static int recv_notification(struct notifier_block *nb, unsigned long evt,
 			     void *dv);
+static int recv_msg(struct sk_buff *buf, struct net_device *dev,
+		    struct packet_type *pt, struct net_device *orig_dev);
+
 /*
  * Network device notifier info
  */
@@ -71,6 +74,11 @@ static struct notifier_block notifier = {
 	.priority	= 0
 };
 
+static struct packet_type tipc_packet_type __read_mostly = {
+	.type = __constant_htons(ETH_P_TIPC),
+	.func = recv_msg,
+};
+
 /**
  * eth_media_addr_set - initialize Ethernet media address structure
  *
@@ -128,20 +136,25 @@ static int send_msg(struct sk_buff *buf, struct tipc_bearer *tb_ptr,
 static int recv_msg(struct sk_buff *buf, struct net_device *dev,
 		    struct packet_type *pt, struct net_device *orig_dev)
 {
-	struct eth_media *eb_ptr = (struct eth_media *)pt->af_packet_priv;
+	struct tipc_bearer *b_ptr;
 
 	if (!net_eq(dev_net(dev), &init_net)) {
 		kfree_skb(buf);
 		return NET_RX_DROP;
 	}
 
-	if (likely(eb_ptr->bearer)) {
+	rcu_read_lock();
+	b_ptr = rcu_dereference(dev->tipc_ptr);
+	if (likely(b_ptr)) {
 		if (likely(buf->pkt_type <= PACKET_BROADCAST)) {
 			buf->next = NULL;
-			tipc_recv_msg(buf, eb_ptr->bearer);
+			tipc_recv_msg(buf, b_ptr);
+			rcu_read_unlock();
 			return NET_RX_SUCCESS;
 		}
 	}
+	rcu_read_unlock();
+
 	kfree_skb(buf);
 	return NET_RX_DROP;
 }
@@ -151,10 +164,7 @@ static int recv_msg(struct sk_buff *buf, struct net_device *dev,
  */
 static void setup_media(struct work_struct *work)
 {
-	struct eth_media *eb_ptr =
-		container_of(work, struct eth_media, setup);
-
-	dev_add_pack(&eb_ptr->tipc_packet_type);
+	dev_add_pack(&tipc_packet_type);
 }
 
 /**
@@ -183,15 +193,11 @@ static int enable_media(struct tipc_bearer *tb_ptr)
 
 	/* Create Ethernet bearer for device */
 	eb_ptr->dev = dev;
-	eb_ptr->tipc_packet_type.type = htons(ETH_P_TIPC);
-	eb_ptr->tipc_packet_type.dev = dev;
-	eb_ptr->tipc_packet_type.func = recv_msg;
-	eb_ptr->tipc_packet_type.af_packet_priv = eb_ptr;
-	INIT_LIST_HEAD(&(eb_ptr->tipc_packet_type.list));
 	INIT_WORK(&eb_ptr->setup, setup_media);
 	schedule_work(&eb_ptr->setup);
 
 	/* Associate TIPC bearer with Ethernet bearer */
+	tb_ptr->dev = dev;
 	eb_ptr->bearer = tb_ptr;
 	tb_ptr->usr_handle = (void *)eb_ptr;
 	memset(tb_ptr->bcast_addr.value, 0, sizeof(tb_ptr->bcast_addr.value));
@@ -200,6 +206,7 @@ static int enable_media(struct tipc_bearer *tb_ptr)
 	tb_ptr->bcast_addr.broadcast = 1;
 	tb_ptr->mtu = dev->mtu;
 	eth_media_addr_set(tb_ptr, &tb_ptr->addr, (char *)dev->dev_addr);
+	rcu_assign_pointer(dev->tipc_ptr, tb_ptr);
 	return 0;
 }
 
@@ -213,7 +220,7 @@ static void cleanup_media(struct work_struct *work)
 	struct eth_media *eb_ptr =
 		container_of(work, struct eth_media, cleanup);
 
-	dev_remove_pack(&eb_ptr->tipc_packet_type);
+	dev_remove_pack(&tipc_packet_type);
 	dev_put(eb_ptr->dev);
 	eb_ptr->dev = NULL;
 }
@@ -232,6 +239,7 @@ static void disable_media(struct tipc_bearer *tb_ptr)
 	eb_ptr->bearer = NULL;
 	INIT_WORK(&eb_ptr->cleanup, cleanup_media);
 	schedule_work(&eb_ptr->cleanup);
+	RCU_INIT_POINTER(tb_ptr->dev->tipc_ptr, NULL);
 }
 
 /**
@@ -243,21 +251,20 @@ static void disable_media(struct tipc_bearer *tb_ptr)
 static int recv_notification(struct notifier_block *nb, unsigned long evt,
 			     void *ptr)
 {
+	struct tipc_bearer *b_ptr;
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
-	struct eth_media *eb_ptr = &eth_media_array[0];
-	struct eth_media *stop = &eth_media_array[MAX_ETH_MEDIA];
 
 	if (!net_eq(dev_net(dev), &init_net))
 		return NOTIFY_DONE;
 
-	while ((eb_ptr->dev != dev)) {
-		if (++eb_ptr == stop)
-			return NOTIFY_DONE;	/* couldn't find device */
-	}
-	if (!eb_ptr->bearer)
+	rcu_read_lock();
+	b_ptr = rcu_dereference(dev->tipc_ptr);
+	if (!b_ptr) {
+		rcu_read_unlock();
 		return NOTIFY_DONE;		/* bearer had been disabled */
+	}
 
-	eb_ptr->bearer->mtu = dev->mtu;
+	b_ptr->mtu = dev->mtu;
 
 	switch (evt) {
 	case NETDEV_CHANGE:
@@ -266,13 +273,15 @@ static int recv_notification(struct notifier_block *nb, unsigned long evt,
 	case NETDEV_DOWN:
 	case NETDEV_CHANGEMTU:
 	case NETDEV_CHANGEADDR:
-		tipc_reset_bearer(eb_ptr->bearer);
+		tipc_reset_bearer(b_ptr);
 		break;
 	case NETDEV_UNREGISTER:
 	case NETDEV_CHANGENAME:
-		tipc_disable_bearer(eb_ptr->bearer->name);
+		tipc_disable_bearer(b_ptr->name);
 		break;
 	}
+	rcu_read_unlock();
+
 	return NOTIFY_OK;
 }