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, 4 insertions, 1 deletions

diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
index ef8884482439..33e5f90dfcf5 100644
--- a/drivers/vhost/tcm_vhost.c
+++ b/drivers/vhost/tcm_vhost.c
@@ -970,7 +970,10 @@ static long vhost_scsi_ioctl(struct file *f, unsigned int ioctl,
                 return vhost_scsi_set_features(vs, features);
         default:
                 mutex_lock(&vs->dev.mutex);
-                r = vhost_dev_ioctl(&vs->dev, ioctl, arg);
+                r = vhost_dev_ioctl(&vs->dev, ioctl, argp);
+                /* TODO: flush backend after dev ioctl. */
+                if (r == -ENOIOCTLCMD)
+                        r = vhost_vring_ioctl(&vs->dev, ioctl, argp);
                 mutex_unlock(&vs->dev.mutex);
                 return r;
         }