Re: [PATCH v12 bpf-next 01/18] net: skbuff: add size metadata to skb_shared_info for xdp

From: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
To: John Fastabend <john.fastabend@gmail.com>
Cc: Lorenzo Bianconi <lorenzo@kernel.org>,
	BPF-dev-list <bpf@vger.kernel.org>,
	Network Development <netdev@vger.kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"Agroskin, Shay" <shayagr@amazon.com>,
	David Ahern <dsahern@kernel.org>,
	Jesper Brouer <brouer@redhat.com>,
	Eelco Chaudron <echaudro@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	Alexander Duyck <alexander.duyck@gmail.com>,
	Saeed Mahameed <saeed@kernel.org>,
	Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
	"Karlsson, Magnus" <magnus.karlsson@intel.com>,
	"Sarkar, Tirthendu" <tirthendu.sarkar@intel.com>,
	Toke Hoiland Jorgensen <toke@redhat.com>
Subject: Re: [PATCH v12 bpf-next 01/18] net: skbuff: add size metadata to skb_shared_info for xdp
Date: Fri, 3 Sep 2021 19:13:18 +0200	[thread overview]
Message-ID: <CAJ0CqmWGNapcmVae52UJNAg7XKS7f0F2dmQMoO+1sL3zp=oFTw@mail.gmail.com> (raw)
In-Reply-To: <612eb79343225_6b872087a@john-XPS-13-9370.notmuch>

>
> 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.
> >
> > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
>
> I assume we can use xdp_frags_tsize for anything else above XDP later?
> Other than simple question looks OK to me.

yes, right as we did for gso_type/xdp_frags_size.

Regards,
Lorenzo

>
> Acked-by: John Fastabend <john.fastabend@gmail.com>
>
> > ---
> >  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;
> >
> >       /* Intermediate layers must ensure that destructor_arg
> >        * remains valid until skb destructor */
> > --
> > 2.31.1
> >
>
>