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Date: Thu, 26 Apr 2012 11:22:27 +0200 From: Eric Dumazet <eric.dumazet@...il.com> To: David Miller <davem@...emloft.net> Cc: ilpo.jarvinen@...sinki.fi, rick.jones2@...com, netdev@...r.kernel.org, therbert@...gle.com, ncardwell@...gle.com, maze@...gle.com, ycheng@...gle.com Subject: Re: [RFC] allow skb->head to point/alias to first skb frag On Thu, 2012-04-26 at 05:18 -0400, David Miller wrote: > From: Eric Dumazet <eric.dumazet@...il.com> > Date: Thu, 26 Apr 2012 11:10:02 +0200 > > > The 'frag' would have a known size : 2048 bytes > > > > But the end of it would be used by struct skb_shared_info > > > > so data_len would be 0 in fact. > > > > This would look like a regular linear skb. > > > > Just a bit set in skb to say : Warning, skb->head was not kmalloced : > > replace kfree(head) by put_page(...) > > > > And this bit would be tested in GRO or tcp merge to 'upgrade' this > > skb->head to proper page/frag > > And what happens if this ends up in a piece of code which wants to > append a page frag? > > Or a piece of code which copies an SKB, including page frag parts? > > All I'm saying is that the number of tests necessary to make this work > properly might become prohibitive. I'll cook a patch, I believe not so many parts assume skb->head can be kmalloc()/kfree(). This should be contained in net/core/skbuff.c only. Elsewhere we use skb->head as a pointer to memory. It will stay the same. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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