linux-kernel - Re: [PATCH] io_uring: Remove CONFIG

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Message-ID: <CAFxkdAqK+JyBysxYwUp8BAuQcjkdOpJ=kA_QNVJMTzGez10HVA@mail.gmail.com>
Date:   Thu, 3 Jun 2021 10:43:23 -0500
From:   Justin Forbes <jmforbes@...uxtx.org>
To:     Justin Forbes <jforbes@...hat.com>
Cc:     Jens Axboe <axboe@...nel.dk>, asml.silence@...il.com,
        io-uring@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] io_uring: Remove CONFIG_EXPERT

On Thu, May 27, 2021 at 11:01 AM Justin Forbes <jforbes@...hat.com> wrote:
>
> On Thu, May 27, 2021 at 9:19 AM Jens Axboe <axboe@...nel.dk> wrote:
> >
> > On 5/27/21 8:12 AM, Justin Forbes wrote:
> > > On Thu, May 27, 2021 at 8:43 AM Jens Axboe <axboe@...nel.dk> wrote:
> > >>
> > >> On 5/26/21 4:34 PM, Justin M. Forbes wrote:
> > >>> While IO_URING has been in fairly heavy development, it is hidden behind
> > >>> CONFIG_EXPERT with a default of on.  It has been long enough now that I
> > >>> think we should remove EXPERT and allow users and distros to decide how
> > >>> they want this config option set without jumping through hoops.
> > >>
> > >> The whole point of EXPERT is to ensure that it doesn't get turned off
> > >> "by accident". It's a core feature, and something that more and more
> > >> apps or libraries are relying on. It's not something I intended to ever
> > >> go away, just like it would never go away for eg futex or epoll support.
> > >>
> > >
> > > I am not arguing with that, I don't expect it will go away. I
> > > certainly do not have an issue with it defaulting to on, and I didn't
> > > even submit this with intention to turn it off for default Fedora. I
> > > do think that there are cases where people might not wish it turned on
> > > at this point in time. Hiding it behind EXPERT makes it much more
> > > difficult than it needs to be.  There are plenty of config options
> > > that are largely expected default and not hidden behind EXPERT.
> >
> > Right there are, but not really core kernel features like the ones
> > I mentioned. Hence my argument for why it's correct as-is and I
> > don't think it should be changed.
> >
>
> Honestly, this is fair, and I understand your concerns behind it. I
> think my real issue is that there is no simple way to override one
> EXPERT setting without having to set them all.  It would be nice if
> expert were a "visible if" menu, setting defaults if not selected,
> which allows direct override with a config file. Perhaps I will try to
> fix this in kbuild.
>

So it turns out that untangling this in kbuild is very difficult
without getting very unexpected results. Given the audit and security
discussions around io_uring lately, I am inclined to believe the
proper action is still to remove 'if EXPERT'.

Justin