Merge branch 'vhost-net-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

drivers/vhost/net.c

@@ -182,15 +182,21 @@ static void handle_tx(struct vhost_net *net)
 			break;
 		/* Nothing new?  Wait for eventfd to tell us they refilled. */
 		if (head == vq->num) {
+			int num_pends;
+
 			wmem = atomic_read(&sock->sk->sk_wmem_alloc);
 			if (wmem >= sock->sk->sk_sndbuf * 3 / 4) {
 				tx_poll_start(net, sock);
 				set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
 				break;
 			}
-			/* If more outstanding DMAs, queue the work */
-			if (unlikely(vq->upend_idx - vq->done_idx >
-				     VHOST_MAX_PEND)) {
+			/* If more outstanding DMAs, queue the work.
+			 * Handle upend_idx wrap around
+			 */
+			num_pends = likely(vq->upend_idx >= vq->done_idx) ?
+				    (vq->upend_idx - vq->done_idx) :
+				    (vq->upend_idx + UIO_MAXIOV - vq->done_idx);
+			if (unlikely(num_pends > VHOST_MAX_PEND)) {
 				tx_poll_start(net, sock);
 				set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
 				break;
@@ -711,8 +717,12 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
 
 	mutex_unlock(&vq->mutex);
 
-	if (oldubufs)
+	if (oldubufs) {
 		vhost_ubuf_put_and_wait(oldubufs);
+		mutex_lock(&vq->mutex);
+		vhost_zerocopy_signal_used(vq);
+		mutex_unlock(&vq->mutex);
+	}
 
 	if (oldsock) {
 		vhost_net_flush_vq(n, index);