Re: [PATCH 5.19 2/3] Revert "io_uring: add buffer selection support to IORING_OP_NOP"

[Dylan Yudaken <dylany@fb.com>]

On Tue, 2022-06-14 at 17:51 +0100, Pavel Begunkov wrote:
> This reverts commit 3d200242a6c968af321913b635fc4014b238cba4.
> 
> Buffer selection with nops was used for debugging and benchmarking
> but
> is useless in real life. Let's revert it before it's released.
> 
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>  fs/io_uring.c | 15 +--------------
>  1 file changed, 1 insertion(+), 14 deletions(-)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index bf556f77d4ab..1b95c6750a81 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -1114,7 +1114,6 @@ static const struct io_op_def io_op_defs[] = {
>         [IORING_OP_NOP] = {
>                 .audit_skip             = 1,
>                 .iopoll                 = 1,
> -               .buffer_select          = 1,
>         },
>         [IORING_OP_READV] = {
>                 .needs_file             = 1,
> @@ -5269,19 +5268,7 @@ static int io_nop_prep(struct io_kiocb *req,
> const struct io_uring_sqe *sqe)
>   */
>  static int io_nop(struct io_kiocb *req, unsigned int issue_flags)
>  {
> -       unsigned int cflags;
> -       void __user *buf;
> -
> -       if (req->flags & REQ_F_BUFFER_SELECT) {
> -               size_t len = 1;
> -
> -               buf = io_buffer_select(req, &len, issue_flags);
> -               if (!buf)
> -                       return -ENOBUFS;
> -       }
> -
> -       cflags = io_put_kbuf(req, issue_flags);
> -       __io_req_complete(req, issue_flags, 0, cflags);
> +       __io_req_complete(req, issue_flags, 0, 0);
>         return 0;
>  }
>  

The liburing test case I added in "buf-ring: add tests that cycle
through the provided buffer ring" relies on this.

I don't mind either way if this is kept or that liburing patch is
reverted, but it should be consistent. What do you think?