Re: [PATCH 1/2] net: Add skb_unclone() helper function.

["Michał Mirosław" <mirqus@gmail.com>]

2013/1/24 Pravin B Shelar <pshelar@nicira.com>:
[...]
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -798,6 +798,19 @@ static inline int skb_cloned(const struct sk_buff *skb)
>  }
>
>  /**
> + *     skb_unclone - creates separate copy if skb is cloned.
> + */
> +static inline bool skb_unclone(struct sk_buff *skb, gfp_t pri)
> +{
> +       might_sleep_if(pri & __GFP_WAIT);
> +
> +       if (skb_cloned(skb))
> +               return pskb_expand_head(skb, 0, 0, pri);
> +
> +       return 0;
> +}

This should return int. pskb_expand_head() returns 0 or -ENOMEM.

[...]
> diff --git a/net/ipv4/xfrm4_mode_tunnel.c b/net/ipv4/xfrm4_mode_tunnel.c
> index ddee0a0..c1f00ef 100644
> --- a/net/ipv4/xfrm4_mode_tunnel.c
> +++ b/net/ipv4/xfrm4_mode_tunnel.c
> @@ -142,8 +142,7 @@ static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
>         for_each_input_rcu(rcv_notify_handlers, handler)
>                 handler->handler(skb);
>
> -       if (skb_cloned(skb) &&
> -           (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
> +       if (skb_unclone(skb, GFP_ATOMIC))
>                 goto out;

And here return -ENOMEM is replaced with return -EINVAL because of this.

Best Regards,
Michał Mirosław