Re: [PATCH v2 1/3] io_uring: register single issuer task at creation

[Pavel Begunkov]

On 9/26/22 20:40, Jens Axboe wrote:
> On 9/26/22 1:12 PM, Pavel Begunkov wrote:
> > On 9/26/22 18:09, Dylan Yudaken wrote:
> > > Instead of picking the task from the first submitter task, rather use the
> > > creator task or in the case of disabled (IORING_SETUP_R_DISABLED) the
> > > enabling task.
> > >
> > > This approach allows a lot of simplification of the logic here. This
> > > removes init logic from the submission path, which can always be a bit
> > > confusing, but also removes the need for locking to write (or read) the
> > > submitter_task.
> > >
> > > Users that want to move a ring before submitting can create the ring
> > > disabled and then enable it on the submitting task.
> >
> > I think Dylan briefly mentioned before that it might be a good
> > idea to task limit registration as well. I can't think of a use
> > case at the moment but I agree we may find some in the future.
> >
> >
> > diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> > index 242d896c00f3..60a471e43fd9 100644
> > --- a/io_uring/io_uring.c
> > +++ b/io_uring/io_uring.c
> > @@ -3706,6 +3706,9 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
> >       if (WARN_ON_ONCE(percpu_ref_is_dying(&ctx->refs)))
> >           return -ENXIO;
> >   
> > +    if (ctx->submitter_task && ctx->submitter_task != current)
> > +        return -EEXIST;
> > +
> >       if (ctx->restricted) {
> >           if (opcode >= IORING_REGISTER_LAST)
> >               return -EINVAL;
>
> Yes, I don't see any reason why not to enforce this for registration
> too. Don't think there's currently a need to do so, but it'd be easy
> to miss once we do add that. Let's queue that up for 6.1?

6.1 + stable sounds ok, I don't have an opinion on how to how
to merge it.

--
Pavel Begunkov