vhost: avoid backend flush on vring ops

vring changes already do a flush internally where appropriate, so we do
not need a second flush.

It's currently not very expensive but a follow-up patch makes flush more
heavy-weight, so remove the extra flush here to avoid regressing
performance if call or kick fds are changed on data path.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index ff6c91995c96..1802ab662082 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -942,8 +942,11 @@ static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
                 return vhost_net_reset_owner(n);
         default:
                 mutex_lock(&n->dev.mutex);
-                r = vhost_dev_ioctl(&n->dev, ioctl, arg);
-                vhost_net_flush(n);
+                r = vhost_dev_ioctl(&n->dev, ioctl, argp);
+                if (r == -ENOIOCTLCMD)
+                        r = vhost_vring_ioctl(&n->dev, ioctl, argp);
+                else
+                        vhost_net_flush(n);
                 mutex_unlock(&n->dev.mutex);
                 return r;
         }