Re: [PATCH liburing 3/3] man/io_uring_enter.2: add EACCES and EBADFD errors

[Stefano Garzarella <sgarzare@redhat.com>]

On Mon, Sep 14, 2020 at 09:38:25AM -0600, Jens Axboe wrote:
> On 9/14/20 2:05 AM, Stefano Garzarella wrote:
> > On Fri, Sep 11, 2020 at 09:36:02AM -0600, Jens Axboe wrote:
> >> On 9/11/20 7:34 AM, Stefano Garzarella wrote:
> >>> These new errors are added with the restriction series recently
> >>> merged in io_uring (Linux 5.10).
> >>>
> >>> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> >>> ---
> >>>  man/io_uring_enter.2 | 18 ++++++++++++++++++
> >>>  1 file changed, 18 insertions(+)
> >>>
> >>> diff --git a/man/io_uring_enter.2 b/man/io_uring_enter.2
> >>> index 5443d5f..4773dfd 100644
> >>> --- a/man/io_uring_enter.2
> >>> +++ b/man/io_uring_enter.2
> >>> @@ -842,6 +842,16 @@ is set appropriately.
> >>>  .PP
> >>>  .SH ERRORS
> >>>  .TP
> >>> +.B EACCES
> >>> +The
> >>> +.I flags
> >>> +field or
> >>> +.I opcode
> >>> +in a submission queue entry is not allowed due to registered restrictions.
> >>> +See
> >>> +.BR io_uring_register (2)
> >>> +for details on how restrictions work.
> >>> +.TP
> >>>  .B EAGAIN
> >>>  The kernel was unable to allocate memory for the request, or otherwise ran out
> >>>  of resources to handle it. The application should wait for some completions and
> >>> @@ -861,6 +871,14 @@ field in the submission queue entry is invalid, or the
> >>>  flag was set in the submission queue entry, but no files were registered
> >>>  with the io_uring instance.
> >>>  .TP
> >>> +.B EBADFD
> >>> +The
> >>> +.I fd
> >>> +field in the submission queue entry is valid, but the io_uring ring is not
> >>> +in the right state (enabled). See
> >>> +.BR io_uring_register (2)
> >>> +for details on how to enable the ring.
> >>> +.TP
> >>
> >> I actually think some of this needs general updating. io_uring_enter()
> >> will not return an error on behalf of an sqe, it'll only return an error
> >> if one happened outside the context of a specific sqe. Any error
> >> specific to an sqe will generate a cqe with the result.
> > 
> > Mmm, right.
> > 
> > For example in this case, EACCES is returned by a cqe and EBADFD is
> > returned by io_uring_enter().
> > 
> > Should we create 2 error sections?
> 
> Yep, I think we should. One that describes that io_uring_enter() would
> return in terms of errors, and one that describes cqe->res returns.

Yeah, that would be much better!

> 
> Are you up for this? Would be a great change, making it a lot more
> accurate.

Sure! I'll prepare a patch with this change, and I'll also try to catch
all possible return values, then I'll rebase this series on top of that.

Thanks,
Stefano