Subject: Re: [net PATCH v5 1/6] virtio_net: use dev_kfree_skb for small buffer XDP receive

From: "Michael S. Tsirkin" <[email-masked]>
Date: Mon, 23 Jan 2017 23:08:35 +0200

On Tue, Jan 17, 2017 at 02:19:50PM -0800, John Fastabend wrote:
> In the small buffer case during driver unload we currently use
> put_page instead of dev_kfree_skb. Resolve this by adding a check
> for virtnet mode when checking XDP queue type. Also name the
> function so that the code reads correctly to match the additional
> check.
> 
> Fixes: bb91accf2733 ("virtio-net: XDP support for small buffers")
> Signed-off-by: John Fastabend <[email-masked]>
> Acked-by: Jason Wang <[email-masked]>

Acked-by: Michael S. Tsirkin <[email-masked]>

I think we definitely want this one in -net as it's
a bugfix.

> ---
>  drivers/net/virtio_net.c |    8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 4a10500..d97bb71 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1890,8 +1890,12 @@ static void free_receive_page_frags(struct virtnet_info *vi)
>  			put_page(vi->rq[i].alloc_frag.page);
>  }
>  
> -static bool is_xdp_queue(struct virtnet_info *vi, int q)
> +static bool is_xdp_raw_buffer_queue(struct virtnet_info *vi, int q)
>  {
> +	/* For small receive mode always use kfree_skb variants */
> +	if (!vi->mergeable_rx_bufs)
> +		return false;
> +
>  	if (q < (vi->curr_queue_pairs - vi->xdp_queue_pairs))
>  		return false;
>  	else if (q < vi->curr_queue_pairs)
> @@ -1908,7 +1912,7 @@ static void free_unused_bufs(struct virtnet_info *vi)
>  	for (i = 0; i < vi->max_queue_pairs; i++) {
>  		struct virtqueue *vq = vi->sq[i].vq;
>  		while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) {
> -			if (!is_xdp_queue(vi, i))
> +			if (!is_xdp_raw_buffer_queue(vi, i))
>  				dev_kfree_skb(buf);
>  			else
>  				put_page(virt_to_head_page(buf));