Re: [Qemu-devel] [PATCH] vhost: correctly pass error to caller in vhost_dev_enable_notifiers()

[Jason Wang <jasowang@redhat.com>]

On 05/29/2015 02:13 PM, Jason Wang wrote:
> We override the error value r in fail_vq, this will cause the caller
> can't detect the failure which may cause the caller may disable the
> notifiers twice if vhost is failed to start. Fix this by using another
> variable to keep track the return value of set_host_notifier().
>
> Fixes b0b3db79559e57db340b292621c397e7a6cdbdc5 ("vhost-net: cleanup
> host notifiers at last step")
>
> Cc: qemu-stable@nongnu.org
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>  hw/virtio/vhost.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 54851b7..a7858d3 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -921,7 +921,7 @@ int vhost_dev_enable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev)
>      BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
>      VirtioBusState *vbus = VIRTIO_BUS(qbus);
>      VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(vbus);
> -    int i, r;
> +    int i, r, e;
>      if (!k->set_host_notifier) {
>          fprintf(stderr, "binding does not support host notifiers\n");
>          r = -ENOSYS;
> @@ -939,12 +939,12 @@ int vhost_dev_enable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev)
>      return 0;
>  fail_vq:
>      while (--i >= 0) {
> -        r = k->set_host_notifier(qbus->parent, hdev->vq_index + i, false);
> -        if (r < 0) {
> +        e = k->set_host_notifier(qbus->parent, hdev->vq_index + i, false);
> +        if (e < 0) {
>              fprintf(stderr, "vhost VQ %d notifier cleanup error: %d\n", i, -r);
>              fflush(stderr);
>          }
> -        assert (r >= 0);
> +        assert (e >= 0);
>      }
>  fail:
>      return r;

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