Re: [PATCH v1 01/11] io_uring: support CQE32 in io_uring_cqe

[Kanchan Joshi <joshiiitr@gmail.com>]

On Thu, Apr 21, 2022 at 12:02 PM Stefan Roesch <shr@fb.com> wrote:
>
> This adds the struct io_uring_cqe_extra in the structure io_uring_cqe to
> support large CQE's.
>
> Co-developed-by: Jens Axboe <axboe@kernel.dk>
> Signed-off-by: Stefan Roesch <shr@fb.com>
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
>  include/uapi/linux/io_uring.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> index ee677dbd6a6d..6f9f9b6a9d15 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
> @@ -111,6 +111,7 @@ enum {
>  #define IORING_SETUP_R_DISABLED        (1U << 6)       /* start with ring disabled */
>  #define IORING_SETUP_SUBMIT_ALL        (1U << 7)       /* continue submit on error */
>  #define IORING_SETUP_SQE128    (1U << 8)       /* SQEs are 128b */
> +#define IORING_SETUP_CQE32     (1U << 9)       /* CQEs are 32b */
>
>  enum {
>         IORING_OP_NOP,
> @@ -201,6 +202,11 @@ enum {
>  #define IORING_POLL_UPDATE_EVENTS      (1U << 1)
>  #define IORING_POLL_UPDATE_USER_DATA   (1U << 2)
>
> +struct io_uring_cqe_extra {
> +       __u64   extra1;
> +       __u64   extra2;
> +};
> +
>  /*
>   * IO completion data structure (Completion Queue Entry)
>   */
> @@ -208,6 +214,12 @@ struct io_uring_cqe {
>         __u64   user_data;      /* sqe->data submission passed back */
>         __s32   res;            /* result code for this event */
>         __u32   flags;
> +
> +       /*
> +        * If the ring is initialized with IORING_SETUP_CQE32, then this field
> +        * contains 16-bytes of padding, doubling the size of the CQE.
> +        */
> +       struct io_uring_cqe_extra       b[0];
>  };
Will it be any better to replace struct b[0]  with "u64 extra[ ]" ?
With that new fields will be referred as cqe->extra[0] and cqe->extra[1].

And if we go that route, maybe "aux" sounds better than "extra".