netdev - Re: [PATCH v13 bpf-next 01/18] net: skbuff: add size metadata to skb_shared

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Date:   Tue, 7 Sep 2021 16:45:28 +0200
From:   Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To:     Jesper Dangaard Brouer <jbrouer@...hat.com>
Cc:     Lorenzo Bianconi <lorenzo@...nel.org>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, brouer@...hat.com, davem@...emloft.net,
        kuba@...nel.org, ast@...nel.org, daniel@...earbox.net,
        shayagr@...zon.com, john.fastabend@...il.com, dsahern@...nel.org,
        echaudro@...hat.com, jasowang@...hat.com,
        alexander.duyck@...il.com, saeed@...nel.org,
        maciej.fijalkowski@...el.com, magnus.karlsson@...el.com,
        tirthendu.sarkar@...el.com, toke@...hat.com
Subject: Re: [PATCH v13 bpf-next 01/18] net: skbuff: add size metadata to
 skb_shared_info for xdp

> 
> 
> On 07/09/2021 14.35, Lorenzo Bianconi wrote:
> > Introduce xdp_frags_tsize field in skb_shared_info data structure
> > to store xdp_buff/xdp_frame truesize (xdp_frags_tsize will be used
> > in xdp multi-buff support). In order to not increase skb_shared_info
> > size we will use a hole due to skb_shared_info alignment.
> > Introduce xdp_frags_size field in skb_shared_info data structure
> > reusing gso_type field in order to store xdp_buff/xdp_frame paged size.
> > xdp_frags_size will be used in xdp multi-buff support.
> > 
> > Acked-by: John Fastabend <john.fastabend@...il.com>
> > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> > ---
> >   include/linux/skbuff.h | 6 +++++-
> >   1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > index 6bdb0db3e825..1abeba7ef82e 100644
> > --- a/include/linux/skbuff.h
> > +++ b/include/linux/skbuff.h
> > @@ -522,13 +522,17 @@ struct skb_shared_info {
> >   	unsigned short	gso_segs;
> >   	struct sk_buff	*frag_list;
> >   	struct skb_shared_hwtstamps hwtstamps;
> > -	unsigned int	gso_type;
> > +	union {
> > +		unsigned int	gso_type;
> > +		unsigned int	xdp_frags_size;
> > +	};
> >   	u32		tskey;
> >   	/*
> >   	 * Warning : all fields before dataref are cleared in __alloc_skb()
> >   	 */
> >   	atomic_t	dataref;
> > +	unsigned int	xdp_frags_tsize;
> 
> I wonder if we could call this variable: xdp_frags_truesize.
> 
> As while reviewing patches I had to focus my eyes extra hard to tell the
> variables xdp_frags_size and xdp_frags_tsize from each-other.

sure, I will fix it in v14.

Regards,
Lorenzo

> 
> --Jesper
> 

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