netpoll info leak

After looking harder, Steve noticed that the netpoll
beast leaked a little every time it shutdown for a nap.
Not a big leak, but a nuisance kind of thing.

He took out his refcount duct tape and patched the
leak. It was overkill since there was already other
locking in that area, but it looked clean and wouldn't
attract fleas.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>

include/linux/netpoll.h

@@ -25,6 +25,7 @@ struct netpoll {
 };
 
 struct netpoll_info {
+	atomic_t refcnt;
 	spinlock_t poll_lock;
 	int poll_owner;
 	int tries;

net/core/netpoll.c

@@ -658,8 +658,11 @@ int netpoll_setup(struct netpoll *np)
 		npinfo->tries = MAX_RETRIES;
 		spin_lock_init(&npinfo->rx_lock);
 		skb_queue_head_init(&npinfo->arp_tx);
-	} else
+		atomic_set(&npinfo->refcnt, 1);
+	} else {
 		npinfo = ndev->npinfo;
+		atomic_inc(&npinfo->refcnt);
+	}
 
 	if (!ndev->poll_controller) {
 		printk(KERN_ERR "%s: %s doesn't support polling, aborting.\n",
@@ -766,12 +769,22 @@ void netpoll_cleanup(struct netpoll *np)
 
 	if (np->dev) {
 		npinfo = np->dev->npinfo;
-		if (npinfo && npinfo->rx_np == np) {
+		if (npinfo) {
+			if (npinfo->rx_np == np) {
 				spin_lock_irqsave(&npinfo->rx_lock, flags);
 				npinfo->rx_np = NULL;
 				npinfo->rx_flags &= ~NETPOLL_RX_ENABLED;
 				spin_unlock_irqrestore(&npinfo->rx_lock, flags);
 			}
+
+			np->dev->npinfo = NULL;
+			if (atomic_dec_and_test(&npinfo->refcnt)) {
+				skb_queue_purge(&npinfo->arp_tx);
+
+				kfree(npinfo);
+			}
+		}
+
 		dev_put(np->dev);
 	}