Re: [Xen-devel] [PATCH] xen-netback: use netdev_alloc_skb_ip_align

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

(apologies for the late reply, I've been away)

On Wed, 2013-03-20 at 19:21 +0000, Stephen Hemminger wrote:
> Use standard helper function to allocate and align received packet.
> Compile tested only
> 
> Signed-off-by: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
> 
> 
> --- a/drivers/net/xen-netback/netback.c       2013-03-07 18:12:52.825300956 
> -0800
> +++ b/drivers/net/xen-netback/netback.c       2013-03-20 12:09:09.052034865 
> -0700
> @@ -1357,8 +1357,8 @@ static unsigned xen_netbk_tx_build_gops(
>                           ret < MAX_SKB_FRAGS) ?
>                       PKT_PROT_LEN : txreq.size;
>  
> -             skb = alloc_skb(data_len + NET_SKB_PAD + NET_IP_ALIGN,
> -                             GFP_ATOMIC | __GFP_NOWARN);
> +             skb = __netdev_alloc_skb_ip_align(vif->dev, data_len,
> +                                               GFP_ATOMIC | __GFP_NOWARN);

__netdev_alloc_skb_ip_align accounts for NET_IP_ALIGN but not
NET_SKB_PAD, is this aspect of the change intentional? (I'm not really
sure how much NET_SKB_PAD is worth in practice).


>               if (unlikely(skb == NULL)) {
>                       netdev_dbg(vif->dev,
>                                  "Can't allocate a skb in start_xmit.\n");
> @@ -1366,9 +1366,6 @@ static unsigned xen_netbk_tx_build_gops(
>                       break;
>               }
>  
> -             /* Packets passed to netif_rx() must have some headroom. */
> -             skb_reserve(skb, NET_SKB_PAD + NET_IP_ALIGN);
> -
>               if (extras[XEN_NETIF_EXTRA_TYPE_GSO - 1].type) {
>                       struct xen_netif_extra_info *gso;
>                       gso = &extras[XEN_NETIF_EXTRA_TYPE_GSO - 1];



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