On Fri, 31 Mar 2023 17:01:54 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote:
> On Tue, Mar 28, 2023 at 8:04 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>
> > ---
> > drivers/net/virtio_net.c | 15 ++++++---------
> > 1 file changed, 6 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index e2560b6f7980..4d2bf1ce0730 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));
> > @@ -1259,6 +1262,9 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> > page_address(page) + offset, len);
> > frame_sz = PAGE_SIZE;
> > offset = VIRTIO_XDP_HEADROOM;
> > +
> > + put_page(page);
> > + page = xdp_page;
> > } else {
> > xdp_page = page;
> > }
>
> While at this I would go a little further, just remove the above
> assignment then we can use:
>
> data = page_address(page) + offset;
>
> Which seems cleaner?
I will try.
Thanks.
>
> Thanks
>
> > @@ -1278,8 +1284,6 @@ 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 +1301,6 @@ 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 +1309,6 @@ 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 +1321,6 @@ 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
> >
>
