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From: David Miller <davem@davemloft.net>
Subject: Re: ixgbe: normalize frag_list usage
Date: Wed, 13 Oct 2010 19:17:02 -0700 (PDT)
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From: Alexander Duyck <alexander.h.duyck@intel.com>
Date: Thu, 07 Oct 2010 12:59:14 -0700

> I can track it in the RSC_CB if that works for you.  Right now though
> I guess I am not seeing the difference between tracking this in
> skb->frag_next vs IXGBE_RSC_CB(skb)->frag_head.  I think it might help
> if you were to provide some functions that demonstrate exactly what
> you had in mind for frag list handling.  Specifically if you were to
> add a function for merging a frag into the frag list, and for how you
> want to approach cleaning up the skb->prev/frag_tail_tracker pointer
> when you are cleaning up an active frag_list.

Basically the one helper function will look like this.

static inline void skb_frag_list_add(struct sk_buff *head,
				     struct sk_buff *new)
{
	if (!skb_shinfo(skb)->frag_list) {
		skb_shinfo(skb)->frag_list = new;
		skb->frag_list_tail = new;
	} else {
		skb->frag_list_tail->frag_list_next = new;
		skb->frag_list_tail = new;
	}
}

If you have to track the head from the tail packets, please do
so in a private control block.