netdev - Re: [net-next 7/7] openvswitch: Use skb

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Date:	Tue, 3 Dec 2013 21:43:02 -0800
From:	Jesse Gross <jesse@...ira.com>
To:	Thomas Graf <tgraf@...g.ch>
Cc:	David Miller <davem@...emloft.net>,
	"dev@...nvswitch.org" <dev@...nvswitch.org>,
	netdev <netdev@...r.kernel.org>,
	Daniel Borkmann <dborkman@...hat.com>, ffusco@...hat.com,
	fleitner@...hat.com, Eric Dumazet <eric.dumazet@...il.com>,
	Ben Hutchings <bhutchings@...arflare.com>
Subject: Re: [net-next 7/7] openvswitch: Use skb_zerocopy() for upcall

On Sat, Nov 30, 2013 at 4:21 AM, Thomas Graf <tgraf@...g.ch> wrote:
> diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
> index 8eaa39a..867edf1 100644
> --- a/net/openvswitch/datapath.c
> +++ b/net/openvswitch/datapath.c
> +static int queue_gso_packets(struct datapath *, struct net *, int dp_ifindex,
> +                            struct sk_buff *, const struct dp_upcall_info *);
> +static int queue_userspace_packet(struct datapath *, struct net *,
> +                                 int dp_ifindex, struct sk_buff *,
>                                   const struct dp_upcall_info *);

Should we drop the dp_ifindex arguments from these functions? It
should be trivially derivable from struct datapath.

>  static size_t upcall_msg_size(const struct sk_buff *skb,
> -                             const struct nlattr *userdata)
> +                             const struct nlattr *userdata,
> +                             unsigned int hdrlen)

I think that 'skb' is now unused.

> @@ -427,7 +429,21 @@ static int queue_userspace_packet(struct net *net, int dp_ifindex,
>                 goto out;
>         }
>
> -       len = upcall_msg_size(skb, upcall_info->userdata);
> +       /* Complete checksum if needed */
> +       if (skb->ip_summed == CHECKSUM_PARTIAL &&
> +           (err = skb_checksum_help(skb)))
> +               goto out;

I think that we can remove the hardware features argument to
__skb_gso_segment() in queue_gso_packet(). It was there to take
advantage of the copy and checksum optimization but that's no longer
present.

> @@ -447,13 +463,17 @@ static int queue_userspace_packet(struct net *net, int dp_ifindex,
>                           nla_len(upcall_info->userdata),
>                           nla_data(upcall_info->userdata));
>
> -       nla = __nla_reserve(user_skb, OVS_PACKET_ATTR_PACKET, skb->len);
> +       /* Only reserve room for attribute header, packet data is added
> +        * in skb_zerocopy() */
> +       if (!(nla = nla_reserve(user_skb, OVS_PACKET_ATTR_PACKET, 0)))
> +               goto out;

Does this initialized 'err' on failure?
--
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