netdev - Re: [PATCH net-next 1/3] skbuff: Add skb_list

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Date:	Tue, 20 Jan 2015 13:43:15 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Pravin B Shelar <pshelar@...ira.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/3] skbuff: Add skb_list_linearize()

On Tue, 2015-01-20 at 12:25 -0800, Pravin B Shelar wrote:
> similar to skb_linearize(), this API takes skb list as arg and
> linearize it into one big skb. STT driver patch will use this.
> 
> Signed-off-by: Pravin B Shelar <pshelar@...ira.com>
> ---
>  include/linux/skbuff.h |  2 ++
>  net/core/skbuff.c      | 35 +++++++++++++++++++++++++++++++++++
>  2 files changed, 37 insertions(+)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 85ab7d7..c9194c1 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -2532,6 +2532,8 @@ static inline int skb_linearize(struct sk_buff *skb)
>  	return skb_is_nonlinear(skb) ? __skb_linearize(skb) : 0;
>  }
>  
> +int skb_list_linearize(struct sk_buff *head, gfp_t gfp_mask);
> +
>  /**
>   * skb_has_shared_frag - can any frag be overwritten
>   * @skb: buffer to test
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 56db472..9ef2881 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -2329,6 +2329,41 @@ void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to)
>  }
>  EXPORT_SYMBOL(skb_copy_and_csum_dev);
>  
> +int skb_list_linearize(struct sk_buff *head, gfp_t gfp_mask)
> +{
> +	struct sk_buff *skb;
> +	int tlen = 0;
> +	int err;
> +
> +	err = skb_linearize(head);
> +	if (err)
> +		return err;
> +
> +	skb = head->next;
> +	while (skb) {
> +		tlen += skb->len;
> +		skb = skb->next;
> +	}
> +	err = pskb_expand_head(head, 0, tlen, gfp_mask);
> +	if (err)
> +		return err;
> +
> +	skb = head->next;
> +	while (skb) {
> +		err = skb_copy_bits(skb, 0, skb_tail_pointer(head), skb->len);
> +		if (err)
> +			return err;
> +		head->tail += skb->len;
> +		skb = skb->next;
> +	}
> +	kfree_skb_list(head->next);
> +	head->next = NULL;
> +	head->len += tlen;
> +	head->truesize = SKB_TRUESIZE(skb_end_offset(head));

This is buggy : skb can have a destructor, like sock_wfree()



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