[PATCH net 2/3] vhost_net: keep private_data and rx_ring synced

[Jason Wang <jasowang@redhat.com>]

We get pointer ring from the exported sock, this means we should keep
rx_ring and vq->private synced during both vq stop and backend set,
otherwise we may see stale rx_ring.

Fixes: c67df11f6e480 ("vhost_net: try batch dequing from skb array")
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/vhost/net.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 60f1080..efb9306 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -973,6 +973,7 @@ static struct socket *vhost_net_stop_vq(struct vhost_net *n,
 	vhost_net_disable_vq(n, vq);
 	vq->private_data = NULL;
 	vhost_net_buf_unproduce(nvq);
+	nvq->rx_ring = NULL;
 	mutex_unlock(&vq->mutex);
 	return sock;
 }
@@ -1162,14 +1163,14 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
 		vhost_net_disable_vq(n, vq);
 		vq->private_data = sock;
 		vhost_net_buf_unproduce(nvq);
-		if (index == VHOST_NET_VQ_RX)
-			nvq->rx_ring = get_tap_ptr_ring(fd);
 		r = vhost_vq_init_access(vq);
 		if (r)
 			goto err_used;
 		r = vhost_net_enable_vq(n, vq);
 		if (r)
 			goto err_used;
+		if (index == VHOST_NET_VQ_RX)
+			nvq->rx_ring = get_tap_ptr_ring(fd);
 
 		oldubufs = nvq->ubufs;
 		nvq->ubufs = ubufs;
-- 
2.7.4