Re: [PATCH][V2] libbpf: add support for canceling cached_cons advance

[Magnus Karlsson <magnus.karlsson@gmail.com>]

On Tue, Nov 24, 2020 at 8:33 AM Li RongQing <lirongqing@baidu.com> wrote:
>
> Add a new function for returning descriptors the user received
> after an xsk_ring_cons__peek call. After the application has
> gotten a number of descriptors from a ring, it might not be able
> to or want to process them all for various reasons. Therefore,
> it would be useful to have an interface for returning or
> cancelling a number of them so that they are returned to the ring.
>
> This patch adds a new function called xsk_ring_cons__cancel that
> performs this operation on nb descriptors counted from the end of
> the batch of descriptors that was received through the peek call.
>
> Signed-off-by: Li RongQing <lirongqing@baidu.com>
> [ Magnus Karlsson: rewrote changelog ]
> Cc: Magnus Karlsson <magnus.karlsson@intel.com>
> ---
> diff with v1: fix the building, and rewrote changelog
>
>  tools/lib/bpf/xsk.h | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h
> index 1069c46364ff..1719a327e5f9 100644
> --- a/tools/lib/bpf/xsk.h
> +++ b/tools/lib/bpf/xsk.h
> @@ -153,6 +153,12 @@ static inline size_t xsk_ring_cons__peek(struct xsk_ring_cons *cons,
>         return entries;
>  }
>
> +static inline void xsk_ring_cons__cancel(struct xsk_ring_cons *cons,
> +                                        size_t nb)
> +{
> +       cons->cached_cons -= nb;
> +}
> +
>  static inline void xsk_ring_cons__release(struct xsk_ring_cons *cons, size_t nb)
>  {
>         /* Make sure data has been read before indicating we are done
> --
> 2.17.3

Thank you RongQing.

Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>