Re: [PATCH 1/4] io_uring: add IO_URING_F_INLINE issue flag

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

On Thu, Jun 5, 2025 at 12:47 PM Jens Axboe <axboe@kernel.dk> wrote:
>
> Set when the execution of the request is done inline from the system
> call itself. Any deferred issue will never have this flag set.
>
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
>  include/linux/io_uring_types.h | 2 ++
>  io_uring/io_uring.c            | 3 ++-
>  2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
> index 2922635986f5..054c43c02c96 100644
> --- a/include/linux/io_uring_types.h
> +++ b/include/linux/io_uring_types.h
> @@ -26,6 +26,8 @@ enum io_uring_cmd_flags {
>         IO_URING_F_MULTISHOT            = 4,
>         /* executed by io-wq */
>         IO_URING_F_IOWQ                 = 8,
> +       /* executed inline from syscall */
> +       IO_URING_F_INLINE               = 16,
>         /* int's last bit, sign checks are usually faster than a bit test */
>         IO_URING_F_NONBLOCK             = INT_MIN,
>
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index cf759c172083..079a95e1bd82 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -1962,7 +1962,8 @@ static inline void io_queue_sqe(struct io_kiocb *req)
>  {
>         int ret;
>
> -       ret = io_issue_sqe(req, IO_URING_F_NONBLOCK|IO_URING_F_COMPLETE_DEFER);
> +       ret = io_issue_sqe(req, IO_URING_F_NONBLOCK|IO_URING_F_COMPLETE_DEFER|
> +                               IO_URING_F_INLINE);

Isn't io_queue_sqe() also called from io_req_task_submit(), which is
an io_req_tw_func_t callback? Task work runs after the SQ slots have
already been returned to userspace, right? Before the unconditional
memcpy() was added, we had observed requests in linked chains with
corrupted SQEs due to the async task work issue.

As is, it looks like IO_URING_F_INLINE is just the inverse of
IO_URING_F_IOWQ, so it may not be necessary to add a new flag. But I
can see how core io_uring might add additional async issue cases in
the future.

Best,
Caleb



>
>         /*
>          * We async punt it if the file wasn't marked NOWAIT, or if the file
> --
> 2.49.0
>