On Tue, Apr 18, 2023 at 2:53 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote:
>
> In the xdp implementation of virtio-net mergeable, it always checks
> whether two page is used and a page is selected to release. This is
> complicated for the processing of action, and be careful.
>
> In the entire process, we have such principles:
> * If xdp_page is used (PASS, TX, Redirect), then we release the old
> page.
> * If it is a drop case, we will release two. The old page obtained from
> buf is release inside err_xdp, and xdp_page needs be relased by us.
>
> But in fact, when we allocate a new page, we can release the old page
> immediately. Then just one is using, we just need to release the new
> page for drop case. On the drop path, err_xdp will release the variable
> "page", so we only need to let "page" point to the new xdp_page in
> advance.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
Thanks
> ---
> drivers/net/virtio_net.c | 19 +++++++------------
> 1 file changed, 7 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index e2560b6f7980..42435e762d72 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1245,6 +1245,9 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> if (!xdp_page)
> goto err_xdp;
> offset = VIRTIO_XDP_HEADROOM;
> +
> + put_page(page);
> + page = xdp_page;
> } else if (unlikely(headroom < virtnet_get_headroom(vi))) {
> xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
> sizeof(struct skb_shared_info));
> @@ -1259,11 +1262,12 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> page_address(page) + offset, len);
> frame_sz = PAGE_SIZE;
> offset = VIRTIO_XDP_HEADROOM;
> - } else {
> - xdp_page = page;
> +
> + put_page(page);
> + page = xdp_page;
> }
>
> - data = page_address(xdp_page) + offset;
> + data = page_address(page) + offset;
> err = virtnet_build_xdp_buff_mrg(dev, vi, rq, &xdp, data, len, frame_sz,
> &num_buf, &xdp_frags_truesz, stats);
> if (unlikely(err))
> @@ -1278,8 +1282,6 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> if (unlikely(!head_skb))
> goto err_xdp_frags;
>
> - if (unlikely(xdp_page != page))
> - put_page(page);
> rcu_read_unlock();
> return head_skb;
> case XDP_TX:
> @@ -1297,8 +1299,6 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> goto err_xdp_frags;
> }
> *xdp_xmit |= VIRTIO_XDP_TX;
> - if (unlikely(xdp_page != page))
> - put_page(page);
> rcu_read_unlock();
> goto xdp_xmit;
> case XDP_REDIRECT:
> @@ -1307,8 +1307,6 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> if (err)
> goto err_xdp_frags;
> *xdp_xmit |= VIRTIO_XDP_REDIR;
> - if (unlikely(xdp_page != page))
> - put_page(page);
> rcu_read_unlock();
> goto xdp_xmit;
> default:
> @@ -1321,9 +1319,6 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> goto err_xdp_frags;
> }
> err_xdp_frags:
> - if (unlikely(xdp_page != page))
> - __free_pages(xdp_page, 0);
> -
> if (xdp_buff_has_frags(&xdp)) {
> shinfo = xdp_get_shared_info_from_buff(&xdp);
> for (i = 0; i < shinfo->nr_frags; i++) {
> --
> 2.32.0.3.g01195cf9f
>
