Re: [PATCH v2] io_uring: fix incorrect unlikely() usage in io_waitid_prep()

[Caleb Sander Mateos <csander@purestorage.com>]

On Sat, Oct 18, 2025 at 12:33 PM Alok Tiwari <alok.a.tiwari@oracle.com> wrote:
>
> The negation operator incorrectly places outside the unlikely() macro:

"incorrectly places" -> "is incorrectly placed"?

>
>     if (!unlikely(iwa))
>
> This inverted the compiler branch prediction hint, marking the NULL
> case as likely instead of unlikely. The intent is to indicate that
> allocation failures are rare, consistent with common kernel patterns.
>
>  Moving the negation inside unlikely():
>
>     if (unlikely(!iwa))
>
> Fixes: 2b4fc4cd43f2 ("io_uring/waitid: setup async data in the prep handler")
> Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>

Other than that,
Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>

> ---
> v1 -> v2
> Remove misleading "constant result" wording and
> rephrase commit message
> --
>  io_uring/waitid.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/io_uring/waitid.c b/io_uring/waitid.c
> index f25110fb1b12..53532ae6256c 100644
> --- a/io_uring/waitid.c
> +++ b/io_uring/waitid.c
> @@ -250,7 +250,7 @@ int io_waitid_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>                 return -EINVAL;
>
>         iwa = io_uring_alloc_async_data(NULL, req);
> -       if (!unlikely(iwa))
> +       if (unlikely(!iwa))
>                 return -ENOMEM;
>         iwa->req = req;
>
> --
> 2.50.1
>