Re: [PATCH 2/5] io_uring/zcrx: notify user on frag copy fallback

[Pavel Begunkov <asml.silence@gmail.com>]

On 4/22/26 12:25, Clément Léger wrote:
> Add a ZCRX_NOTIF_COPY notification type to signal userspace when a
> received fragment could not be delivered using zero-copy and was
> instead copied into a buffer.
> 
> Signed-off-by: Clément Léger <cleger@meta.com>
> ---
>   include/uapi/linux/io_uring/zcrx.h | 1 +
>   io_uring/zcrx.c                    | 7 ++++++-
>   io_uring/zcrx.h                    | 3 ++-
>   3 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/include/uapi/linux/io_uring/zcrx.h b/include/uapi/linux/io_uring/zcrx.h
> index b8596d7d47b6..e0c0079626c8 100644
> --- a/include/uapi/linux/io_uring/zcrx.h
> +++ b/include/uapi/linux/io_uring/zcrx.h
> @@ -70,6 +70,7 @@ enum zcrx_features {
>   
>   enum zcrx_notification_type {
>   	ZCRX_NOTIF_NO_BUFFERS = 1 << 0,
> +	ZCRX_NOTIF_COPY = 1 << 1
>   };
>   
>   struct zcrx_notification_desc {
> diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
> index 35ca28cb6583..732e585aa13a 100644
> --- a/io_uring/zcrx.c
> +++ b/io_uring/zcrx.c
> @@ -1510,8 +1510,13 @@ static int io_zcrx_copy_frag(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
>   			     const skb_frag_t *frag, int off, int len)
>   {
>   	struct page *page = skb_frag_page(frag);
> +	int ret;
> +
> +	ret = io_zcrx_copy_chunk(req, ifq, page, off + skb_frag_off(frag), len);
> +	if (ret > 0)
> +		zcrx_send_notif(ifq, ZCRX_NOTIF_COPY);

We also copy the linear part if present, depends on the semantics
would make sense adding it there as well.

Pavel Begunkov