net/af_iucv: don't track individual TX skbs for TRANS_HIPER sockets

Stop maintaining the skb_send_q list for TRANS_HIPER sockets.

Not only is it extra overhead, but keeping around a list of skb clones
means that we later also have to match the ->sk_txnotify() calls
against these clones and free them accordingly.
The current matching logic (comparing the skbs' shinfo location) is
frustratingly fragile, and breaks if the skb's head is mangled in any
sort of way while passing from dev_queue_xmit() to the device's
HW queue.

Also adjust the interface for ->sk_txnotify(), to make clear that we
don't actually care about any skb internals.

Signed-off-by: Julian Wiedmann <[e-mail]>
Acked-by: Willem de Bruijn <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/s390/net/qeth_core_main.c

···
 	struct sk_buff *skb;
 
 	skb_queue_walk(&buf->skb_list, skb) {
+		struct sock *sk = skb->sk;
+
 		QETH_CARD_TEXT_(q->card, 5, "skbn%d", notification);
 		QETH_CARD_TEXT_(q->card, 5, "%lx", (long) skb);
-		if (skb->sk && skb->sk->sk_family == PF_IUCV)
-			iucv_sk(skb->sk)->sk_txnotify(skb, notification);
+		if (sk && sk->sk_family == PF_IUCV)
+			iucv_sk(sk)->sk_txnotify(sk, notification);
 	}
 }
 

include/net/iucv/af_iucv.h

···
 	atomic_t		msg_recv;
 	atomic_t		pendings;
 	int			transport;
-	void                    (*sk_txnotify)(struct sk_buff *skb,
+	void			(*sk_txnotify)(struct sock *sk,
 					       enum iucv_tx_notify n);
 };
 

net/iucv/af_iucv.c

···
 static void iucv_sock_kill(struct sock *sk);
 static void iucv_sock_close(struct sock *sk);
 
-static void afiucv_hs_callback_txnotify(struct sk_buff *, enum iucv_tx_notify);
+static void afiucv_hs_callback_txnotify(struct sock *sk, enum iucv_tx_notify);
 
 /* Call Back functions */
 static void iucv_callback_rx(struct iucv_path *, struct iucv_message *);
···
 {
 	struct iucv_sock *iucv = iucv_sk(sock);
 	struct af_iucv_trans_hdr *phs_hdr;
-	struct sk_buff *nskb;
 	int err, confirm_recv = 0;
 
 	phs_hdr = skb_push(skb, sizeof(*phs_hdr));
···
 	}
 	skb->protocol = cpu_to_be16(ETH_P_AF_IUCV);
 
-	__skb_header_release(skb);
-	nskb = skb_clone(skb, GFP_ATOMIC);
-	if (!nskb) {
-		err = -ENOMEM;
-		goto err_free;
-	}
-
-	skb_queue_tail(&iucv->send_skb_q, nskb);
 	atomic_inc(&iucv->skbs_in_xmit);
 	err = dev_queue_xmit(skb);
 	if (net_xmit_eval(err)) {
 		atomic_dec(&iucv->skbs_in_xmit);
-		skb_unlink(nskb, &iucv->send_skb_q);
-		kfree_skb(nskb);
 	} else {
 		atomic_sub(confirm_recv, &iucv->msg_recv);
 		WARN_ON(atomic_read(&iucv->msg_recv) < 0);
···
  * afiucv_hs_callback_txnotify() - handle send notifcations from HiperSockets
  *                                 transport
  **/
-static void afiucv_hs_callback_txnotify(struct sk_buff *skb,
-					enum iucv_tx_notify n)
+static void afiucv_hs_callback_txnotify(struct sock *sk, enum iucv_tx_notify n)
 {
-	struct iucv_sock *iucv = iucv_sk(skb->sk);
-	struct sock *sk = skb->sk;
-	struct sk_buff_head *list;
-	struct sk_buff *list_skb;
-	struct sk_buff *nskb;
-	unsigned long flags;
+	struct iucv_sock *iucv = iucv_sk(sk);
 
 	if (sock_flag(sk, SOCK_ZAPPED))
 		return;
 
-	list = &iucv->send_skb_q;
-	spin_lock_irqsave(&list->lock, flags);
-	skb_queue_walk_safe(list, list_skb, nskb) {
-		if (skb_shinfo(list_skb) == skb_shinfo(skb)) {
-			switch (n) {
-			case TX_NOTIFY_OK:
-				atomic_dec(&iucv->skbs_in_xmit);
-				__skb_unlink(list_skb, list);
-				kfree_skb(list_skb);
-				iucv_sock_wake_msglim(sk);
-				break;
-			case TX_NOTIFY_PENDING:
-				atomic_inc(&iucv->pendings);
-				break;
-			case TX_NOTIFY_DELAYED_OK:
-				atomic_dec(&iucv->skbs_in_xmit);
-				__skb_unlink(list_skb, list);
-				atomic_dec(&iucv->pendings);
-				if (atomic_read(&iucv->pendings) <= 0)
-					iucv_sock_wake_msglim(sk);
-				kfree_skb(list_skb);
-				break;
-			case TX_NOTIFY_UNREACHABLE:
-			case TX_NOTIFY_DELAYED_UNREACHABLE:
-			case TX_NOTIFY_TPQFULL: /* not yet used */
-			case TX_NOTIFY_GENERALERROR:
-			case TX_NOTIFY_DELAYED_GENERALERROR:
-				atomic_dec(&iucv->skbs_in_xmit);
-				__skb_unlink(list_skb, list);
-				kfree_skb(list_skb);
-				if (sk->sk_state == IUCV_CONNECTED) {
-					sk->sk_state = IUCV_DISCONN;
-					sk->sk_state_change(sk);
-				}
-				break;
-			}
-			break;
+	switch (n) {
+	case TX_NOTIFY_OK:
+		atomic_dec(&iucv->skbs_in_xmit);
+		iucv_sock_wake_msglim(sk);
+		break;
+	case TX_NOTIFY_PENDING:
+		atomic_inc(&iucv->pendings);
+		break;
+	case TX_NOTIFY_DELAYED_OK:
+		atomic_dec(&iucv->skbs_in_xmit);
+		if (atomic_dec_return(&iucv->pendings) <= 0)
+			iucv_sock_wake_msglim(sk);
+		break;
+	default:
+		atomic_dec(&iucv->skbs_in_xmit);
+		if (sk->sk_state == IUCV_CONNECTED) {
+			sk->sk_state = IUCV_DISCONN;
+			sk->sk_state_change(sk);
 		}
 	}
-	spin_unlock_irqrestore(&list->lock, flags);
 
 	if (sk->sk_state == IUCV_CLOSING) {
 		if (atomic_read(&iucv->skbs_in_xmit) == 0) {
···
 			sk->sk_state_change(sk);
 		}
 	}
-
 }
 
 /*