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Message-ID: <1681981800.3300662-2-xuanzhuo@linux.alibaba.com>
Date:   Thu, 20 Apr 2023 17:10:00 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     netdev@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        virtualization@...ts.linux-foundation.org, bpf@...r.kernel.org
Subject: Re: [PATCH net-next v2 08/14] virtio_net: auto release xdp shinfo

On Thu, 20 Apr 2023 13:59:30 +0800, Jason Wang <jasowang@...hat.com> wrote:
> On Tue, Apr 18, 2023 at 2:53 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> >
> > virtnet_build_xdp_buff_mrg() and virtnet_xdp_handler() auto
> > release xdp shinfo then the caller no need to careful the xdp shinfo.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > ---
> >  drivers/net/virtio_net.c | 29 +++++++++++++++++------------
> >  1 file changed, 17 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index e2eade87d2d4..266c1670beda 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -834,7 +834,7 @@ static int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
> >                 xdpf = xdp_convert_buff_to_frame(xdp);
> >                 if (unlikely(!xdpf)) {
> >                         netdev_dbg(dev, "convert buff to frame failed for xdp\n");
> > -                       return VIRTNET_XDP_RES_DROP;
> > +                       goto drop;
> >                 }
> >
> >                 err = virtnet_xdp_xmit(dev, 1, &xdpf, 0);
> > @@ -842,7 +842,7 @@ static int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
> >                         xdp_return_frame_rx_napi(xdpf);
> >                 } else if (unlikely(err < 0)) {
> >                         trace_xdp_exception(dev, xdp_prog, act);
> > -                       return VIRTNET_XDP_RES_DROP;
> > +                       goto drop;
> >                 }
> >
> >                 *xdp_xmit |= VIRTIO_XDP_TX;
> > @@ -852,7 +852,7 @@ static int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
> >                 stats->xdp_redirects++;
> >                 err = xdp_do_redirect(dev, xdp, xdp_prog);
> >                 if (err)
> > -                       return VIRTNET_XDP_RES_DROP;
> > +                       goto drop;
> >
> >                 *xdp_xmit |= VIRTIO_XDP_REDIR;
> >                 return VIRTNET_XDP_RES_CONSUMED;
> > @@ -864,8 +864,12 @@ static int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
> >                 trace_xdp_exception(dev, xdp_prog, act);
> >                 fallthrough;
> >         case XDP_DROP:
> > -               return VIRTNET_XDP_RES_DROP;
> > +               break;
> >         }
> > +
> > +drop:
> > +       put_xdp_frags(xdp);
> > +       return VIRTNET_XDP_RES_DROP;
> >  }
>
> Patch looks correct but we end up some inconsistency here.
>
> frags are automatically released.
>
> but the page still needs to be freed by the caller?


Yes.

Do you want to auto free page?

Thanks.



>
> Thanks
>
>
> >
> >  static unsigned int virtnet_get_headroom(struct virtnet_info *vi)
> > @@ -1201,7 +1205,7 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
> >                                  dev->name, *num_buf,
> >                                  virtio16_to_cpu(vi->vdev, hdr->num_buffers));
> >                         dev->stats.rx_length_errors++;
> > -                       return -EINVAL;
> > +                       goto err;
> >                 }
> >
> >                 stats->bytes += len;
> > @@ -1220,7 +1224,7 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
> >                         pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
> >                                  dev->name, len, (unsigned long)(truesize - room));
> >                         dev->stats.rx_length_errors++;
> > -                       return -EINVAL;
> > +                       goto err;
> >                 }
> >
> >                 frag = &shinfo->frags[shinfo->nr_frags++];
> > @@ -1235,6 +1239,10 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
> >
> >         *xdp_frags_truesize = xdp_frags_truesz;
> >         return 0;
> > +
> > +err:
> > +       put_xdp_frags(xdp);
> > +       return -EINVAL;
> >  }
> >
> >  static void *mergeable_xdp_prepare(struct virtnet_info *vi,
> > @@ -1364,7 +1372,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> >                 err = virtnet_build_xdp_buff_mrg(dev, vi, rq, &xdp, data, len, frame_sz,
> >                                                  &num_buf, &xdp_frags_truesz, stats);
> >                 if (unlikely(err))
> > -                       goto err_xdp_frags;
> > +                       goto err_xdp;
> >
> >                 act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
> >
> > @@ -1372,7 +1380,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> >                 case VIRTNET_XDP_RES_PASS:
> >                         head_skb = build_skb_from_xdp_buff(dev, vi, &xdp, xdp_frags_truesz);
> >                         if (unlikely(!head_skb))
> > -                               goto err_xdp_frags;
> > +                               goto err_xdp;
> >
> >                         rcu_read_unlock();
> >                         return head_skb;
> > @@ -1382,11 +1390,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> >                         goto xdp_xmit;
> >
> >                 case VIRTNET_XDP_RES_DROP:
> > -                       break;
> > +                       goto err_xdp;
> >                 }
> > -err_xdp_frags:
> > -               put_xdp_frags(&xdp);
> > -               goto err_xdp;
> >         }
> >         rcu_read_unlock();
> >
> > --
> > 2.32.0.3.g01195cf9f
> >
>

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