netdev - Re: [bpf-next V1-RFC PATCH 10/14] tun: setup xdp_rxq

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Date:   Thu, 21 Dec 2017 16:42:28 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Willem de Bruijn <willemb@...gle.com>,
        "Michael S. Tsirkin" <mst@...hat.com>, netdev@...r.kernel.org,
        dsahern@...il.com, gospo@...adcom.com, bjorn.topel@...el.com,
        michael.chan@...adcom.com, brouer@...hat.com
Subject: Re: [bpf-next V1-RFC PATCH 10/14] tun: setup xdp_rxq_info

On Wed, 20 Dec 2017 15:48:01 +0800
Jason Wang <jasowang@...hat.com> wrote:

> > diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> > index e367d6310353..f1df08c2c541 100644
> > --- a/drivers/net/tun.c
> > +++ b/drivers/net/tun.c
> > @@ -180,6 +180,7 @@ struct tun_file {
> >   	struct list_head next;
> >   	struct tun_struct *detached;
> >   	struct skb_array tx_array;
> > +	struct xdp_rxq_info xdp_rxq;
> >   };
> >   
> >   struct tun_flow_entry {
> > @@ -687,8 +688,10 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
> >   			    tun->dev->reg_state == NETREG_REGISTERED)
> >   				unregister_netdevice(tun->dev);
> >   		}
> > -		if (tun)
> > +		if (tun) {
> >   			skb_array_cleanup(&tfile->tx_array);
> > +			xdp_rxq_info_unreg(&tfile->xdp_rxq);
> > +		}
> >   		sock_put(&tfile->sk);
> >   	}
> >   }
> > @@ -728,11 +731,15 @@ static void tun_detach_all(struct net_device *dev)
> >   		tun_napi_del(tun, tfile);
> >   		/* Drop read queue */
> >   		tun_queue_purge(tfile);
> > +		skb_array_cleanup(&tfile->tx_array);  
> 
> Looks like this is unnecessary, skb array will be cleaned up only when 
> fd is closed otherwise there will be a double free.

What code path is called on "fd close" which call skb_array_cleanup() ?
(Is it __tun_detach()?)

Then, I guess I don't need below xdp_rxq_info_unreg() either, right?
 
> > +		xdp_rxq_info_unreg(&tfile->xdp_rxq);
> >   		sock_put(&tfile->sk);

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer