Re: [PATCH v7 1/4] io_uring: Add io_uring04 test for vectored I/O operations

Hi Sachin,

On Mon, 8 Jun 2026 at 13:27, Sachin Sant <[email protected]> wrote:

>
> Hi Sebastian
> > I see some fundamental problems here which admittedly started before this
> > series. I believe these need to be fixed before we apply more tests on
> top
> > of it.
> >
> > In io_uring_submit_sqe() and io_uring_submit_sqe_vec(), opcode is passed
> as
> > user_data:
> > io_uring_submit_sqe_internal(s, fd, opcode, (unsigned long)buf,
> >                               len, offset, opcode);
> >
> > user_data is supposed to be a unique per-request identifier for
> correlating
> > CQEs back to their SQEs. Using opcode there is meaningless as a tag.
> >
> > The existing tests happen to pass because io_uring_do_io_op() and
> > io_uring_do_vec_io_op() always submit exactly one SQE and immediately
> > block waiting for its CQE, so correlation is never actually needed.
> > However, any test with multiple in-flight SQEs of the same opcode would
> > pass;
> > the user_data check in io_uring_wait-cqe() would match regardless of
> which
> > CQE corresponds to which request.
> >
> > Please hold off on applying this series until the underlying issue is
> > fixed. I will send a patch to correct the user_data handling.
> You're right.
>
> In io_uring_submit_sqe() and io_uring_submit_sqe_vec(), we currently
> pass the
> opcode as user_data through io_uring_submit_sqe_internal().
> As you pointed out, that is not a meaningful per-request identifier and it
> breaks CQE-to-SQE correlation once there is more than one in-flight request
> with the same opcode.
>
> > I also think io_uring_do_io_op() and io_uring_do_vec_io_op() should not
> > tightly couple SQE submission with waiting for a CQE.
> > Keeping them as a single helper makes the tests effectively synchronous
> and
> > does not model real io_uring usage.
> > It would be cleaner to have separate helpers for submitting SQEs and
> > waiting/reaping CQEs, and let each test handle CQE validation and
> > result reporting in its own body.
> > Having basic smoke tests, sending single SQE and checking CQE makes sense
> > in LTP, but I doubt we shall have this as a helper.
>
> The existing helpers
> io_uring_do_io_op() and io_uring_do_vec_io_op() hide this because they
> submit a single SQE and immediately wait for a single CQE, so the tests
> are effectively synchronous. That makes the current code work for simple
> smoke coverage, but it is not a good base for adding more
> io_uring tests.
>
> I agree that we should fix this first before applying more tests on top.
>
> The right direction seems to be:
>
> - stop using opcode as user_data
> - make user_data a caller-provided per-request tag/context
> - separate SQE submission from CQE waiting/reaping
> - let each test validate CQEs and report results explicitly as needed
>
> I'll wait for your patch and rework the helpers/tests on top of that
> approach.
> > Thanks and let me know if I misunderstand something here. It's the first
> > time I look at this code really.
> > Sebastian
> >
>
> Nope, you are spot-on with the analysis. Let me know if I can help in
> any way.
>
>
I have the patches ready, so you could absolutely help with the review of
those.
I'm about to send them to the mailing list

Thanks,
Sebastian



> --
> Thanks
> - Sachin
>
>
>

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