Commit 9e380825 authored by Shirley Ma's avatar Shirley Ma Committed by Michael S. Tsirkin
Browse files

vhost: handle wrap around in # of bufs math 



The meth for calculating the # of outstanding buffers gives
incorrect results when vq->upend_idx wraps around zero.
Fix that.

Signed-off-by: default avatarShirley Ma <xma@us.ibm.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent c047e5f3

drivers/vhost/net.c

+9 −3
Original line number Diff line number Diff line
@@ -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;