Revert "tun/tap: add ptr_ring consume helper with netdev queue wakeup"

This reverts commit d4c22d70d7.

There is no netdev queue left to wake after reverting
commit 1d6e569b7d ("tun/tap & vhost-net: avoid ptr_ring tail-drop
when a qdisc is present").

Signed-off-by: Simon Schippers <simon.schippers@tu-dortmund.de>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://patch.msgid.link/20260728092240.250257-5-simon.schippers@tu-dortmund.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/tun.c

@@ -145,8 +145,6 @@ struct tun_file {
 	struct list_head next;
 	struct tun_struct *detached;
 	struct ptr_ring tx_ring;
-	/* Protected by tx_ring.consumer_lock */
-	int cons_cnt;
 	struct xdp_rxq_info xdp_rxq;
 };
 
@@ -590,13 +588,8 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
 		rcu_assign_pointer(tun->tfiles[index],
 				   tun->tfiles[tun->numqueues - 1]);
 		ntfile = rtnl_dereference(tun->tfiles[index]);
-		spin_lock(&ntfile->tx_ring.consumer_lock);
 		ntfile->queue_index = index;
 		ntfile->xdp_rxq.queue_index = index;
-		ntfile->cons_cnt = 0;
-		if (__ptr_ring_empty(&ntfile->tx_ring))
-			netif_wake_subqueue(tun->dev, index);
-		spin_unlock(&ntfile->tx_ring.consumer_lock);
 		rcu_assign_pointer(tun->tfiles[tun->numqueues - 1],
 				   NULL);
 
@@ -737,9 +730,6 @@ static int tun_attach(struct tun_struct *tun, struct file *file,
 		goto out;
 	}
 
-	spin_lock(&tfile->tx_ring.consumer_lock);
-	tfile->cons_cnt = 0;
-	spin_unlock(&tfile->tx_ring.consumer_lock);
 	tfile->queue_index = tun->numqueues;
 	tfile->socket.sk->sk_shutdown &= ~RCV_SHUTDOWN;
 
@@ -2126,46 +2116,13 @@ done:
 	return total;
 }
 
-/* Callers must hold ring.consumer_lock */
+static void *tun_ring_recv(struct tun_file *tfile, int noblock, int *err)
-static void __tun_wake_queue(struct tun_struct *tun,
-			     struct tun_file *tfile, int consumed)
-{
-	struct netdev_queue *txq = netdev_get_tx_queue(tun->dev,
-						tfile->queue_index);
-
-	/* Paired with smp_mb__after_atomic() in tun_net_xmit() */
-	smp_mb();
-	if (netif_tx_queue_stopped(txq)) {
-		tfile->cons_cnt += consumed;
-		if (tfile->cons_cnt >= tfile->tx_ring.size / 2 ||
-		    __ptr_ring_empty(&tfile->tx_ring)) {
-			netif_tx_wake_queue(txq);
-			tfile->cons_cnt = 0;
-		}
-	}
-}
-
-static void *tun_ring_consume(struct tun_struct *tun, struct tun_file *tfile)
-{
-	void *ptr;
-
-	spin_lock(&tfile->tx_ring.consumer_lock);
-	ptr = __ptr_ring_consume(&tfile->tx_ring);
-	if (ptr)
-		__tun_wake_queue(tun, tfile, 1);
-
-	spin_unlock(&tfile->tx_ring.consumer_lock);
-	return ptr;
-}
-
-static void *tun_ring_recv(struct tun_struct *tun, struct tun_file *tfile,
-			   int noblock, int *err)
 {
 	DECLARE_WAITQUEUE(wait, current);
 	void *ptr = NULL;
 	int error = 0;
 
-	ptr = tun_ring_consume(tun, tfile);
+	ptr = ptr_ring_consume(&tfile->tx_ring);
 	if (ptr)
 		goto out;
 	if (noblock) {
@@ -2177,7 +2134,7 @@ static void *tun_ring_recv(struct tun_struct *tun, struct tun_file *tfile,
 
 	while (1) {
 		set_current_state(TASK_INTERRUPTIBLE);
-		ptr = tun_ring_consume(tun, tfile);
+		ptr = ptr_ring_consume(&tfile->tx_ring);
 		if (ptr)
 			break;
 		if (signal_pending(current)) {
@@ -2214,7 +2171,7 @@ static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile,
 
 	if (!ptr) {
 		/* Read frames from ring */
-		ptr = tun_ring_recv(tun, tfile, noblock, &err);
+		ptr = tun_ring_recv(tfile, noblock, &err);
 		if (!ptr)
 			return err;
 	}
@@ -3669,16 +3626,6 @@ static int tun_queue_resize(struct tun_struct *tun)
 					  dev->tx_queue_len, GFP_KERNEL,
 					  tun_ptr_free);
 
-	if (!ret) {
-		for (i = 0; i < tun->numqueues; i++) {
-			tfile = rtnl_dereference(tun->tfiles[i]);
-			spin_lock(&tfile->tx_ring.consumer_lock);
-			netif_wake_subqueue(tun->dev, tfile->queue_index);
-			tfile->cons_cnt = 0;
-			spin_unlock(&tfile->tx_ring.consumer_lock);
-		}
-	}
-
 	kfree(rings);
 	return ret;
 }