virtio_net: ensure netdev_tx_reset_queue is called on tx ring resize

virtnet_tx_resize() flushes remaining tx skbs, requiring DQL counters to
be reset when flushing has actually occurred. Add
virtnet_sq_free_unused_buf_done() as a callback for virtqueue_reset() to
handle this.

Fixes: c8bd1f7 ("virtio_net: add support for Byte Queue Limits")
Cc: <stable@vger.kernel.org> # v6.11+
Signed-off-by: Koichiro Den <koichiro.den@canonical.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/virtio_net.c

@@ -503,6 +503,7 @@ struct virtio_net_common_hdr {
 static struct virtio_net_common_hdr xsk_hdr;
 
 static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf);
+static void virtnet_sq_free_unused_buf_done(struct virtqueue *vq);
 static int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
 			       struct net_device *dev,
 			       unsigned int *xdp_xmit,
@@ -3394,7 +3395,8 @@ static int virtnet_tx_resize(struct virtnet_info *vi, struct send_queue *sq,
 
 	virtnet_tx_pause(vi, sq);
 
-	err = virtqueue_resize(sq->vq, ring_num, virtnet_sq_free_unused_buf, NULL);
+	err = virtqueue_resize(sq->vq, ring_num, virtnet_sq_free_unused_buf,
+			       virtnet_sq_free_unused_buf_done);
 	if (err)
 		netdev_err(vi->dev, "resize tx fail: tx queue index: %d err: %d\n", qindex, err);
 
@@ -6233,6 +6235,14 @@ static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf)
 	}
 }
 
+static void virtnet_sq_free_unused_buf_done(struct virtqueue *vq)
+{
+	struct virtnet_info *vi = vq->vdev->priv;
+	int i = vq2txq(vq);
+
+	netdev_tx_reset_queue(netdev_get_tx_queue(vi->dev, i));
+}
+
 static void free_unused_bufs(struct virtnet_info *vi)
 {
 	void *buf;