Re: [PATCH 2/6] vhost_net: get rid of vhost_net_flush_vq() and extra flush calls

[Stefano Garzarella]

On Mon, Nov 15, 2021 at 06:29:59PM +0300, Andrey Ryabinin wrote:
> vhost_net_flush_vq() calls vhost_work_dev_flush() twice passing
> vhost_dev pointer obtained via 'n->poll[index].dev' and
> 'n->vqs[index].vq.poll.dev'. This is actually the same pointer,
> initialized in vhost_net_open()/vhost_dev_init()/vhost_poll_init()
>
> Remove vhost_net_flush_vq() and call vhost_work_dev_flush() directly.
> Do the flushes only once instead of several flush calls in a row
> which seems rather useless.
>
> Signed-off-by: Andrey Ryabinin <arbn@xxxxxxxxxxxxxxx>
> ---
> drivers/vhost/net.c   | 11 ++---------
> drivers/vhost/vhost.h |  1 +
> 2 files changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 11221f6d11b8..b1feb5e0571e 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -1373,16 +1373,9 @@ static void vhost_net_stop(struct vhost_net *n, struct socket **tx_sock,
> 	*rx_sock = vhost_net_stop_vq(n, &n->vqs[VHOST_NET_VQ_RX].vq);
> }
>
> -static void vhost_net_flush_vq(struct vhost_net *n, int index)
> -{
> -	vhost_work_dev_flush(n->poll[index].dev);
> -	vhost_work_dev_flush(n->vqs[index].vq.poll.dev);
> -}
> -
> static void vhost_net_flush(struct vhost_net *n)
> {
> -	vhost_net_flush_vq(n, VHOST_NET_VQ_TX);
> -	vhost_net_flush_vq(n, VHOST_NET_VQ_RX);
> +	vhost_work_dev_flush(&n->dev);
> 	if (n->vqs[VHOST_NET_VQ_TX].ubufs) {
> 		mutex_lock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);
> 		n->tx_flush = true;
> @@ -1572,7 +1565,7 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
> 	}
>
> 	if (oldsock) {
> -		vhost_net_flush_vq(n, index);
> +		vhost_work_dev_flush(&n->dev);
> 		sockfd_put(oldsock);
> 	}
>
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index 638bb640d6b4..ecbaa5c6005f 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -15,6 +15,7 @@
> #include <linux/vhost_iotlb.h>
> #include <linux/irqbypass.h>
>
> +struct vhost_dev;

Is this change needed?

Stefano