netdev - RE: [PATCH v20 bpf-next 12/23] bpf: add multi-buff support to the bpf_xdp_adjust

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Date:   Fri, 10 Dec 2021 16:11:19 -0800
From:   John Fastabend <john.fastabend@...il.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>, bpf@...r.kernel.org,
        netdev@...r.kernel.org
Cc:     lorenzo.bianconi@...hat.com, davem@...emloft.net, kuba@...nel.org,
        ast@...nel.org, daniel@...earbox.net, shayagr@...zon.com,
        john.fastabend@...il.com, dsahern@...nel.org, brouer@...hat.com,
        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 v20 bpf-next 12/23] bpf: add multi-buff support to the
 bpf_xdp_adjust_tail() API

Lorenzo Bianconi wrote:
> From: Eelco Chaudron <echaudro@...hat.com>
> 
> This change adds support for tail growing and shrinking for XDP multi-buff.
> 
> When called on a multi-buffer packet with a grow request, it will work
> on the last fragment of the packet. So the maximum grow size is the
> last fragments tailroom, i.e. no new buffer will be allocated.
> A XDP mb capable driver is expected to set frag_size in xdp_rxq_info data
> structure to notify the XDP core the fragment size. frag_size set to 0 is
> interpreted by the XDP core as tail growing is not allowed.
> Introduce __xdp_rxq_info_reg utility routine to initialize frag_size field.
> 
> When shrinking, it will work from the last fragment, all the way down to
> the base buffer depending on the shrinking size. It's important to mention
> that once you shrink down the fragment(s) are freed, so you can not grow
> again to the original size.
> 
> Acked-by: Jakub Kicinski <kuba@...nel.org>
> Co-developed-by: Lorenzo Bianconi <lorenzo@...nel.org>
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> Signed-off-by: Eelco Chaudron <echaudro@...hat.com>
> ---
>  drivers/net/ethernet/marvell/mvneta.c |  3 +-
>  include/net/xdp.h                     | 16 ++++++-
>  net/core/filter.c                     | 65 +++++++++++++++++++++++++++
>  net/core/xdp.c                        | 12 ++---
>  4 files changed, 88 insertions(+), 8 deletions(-)
> 

LGTM

Acked-by: John Fastabend <john.fastabend@...il.com>