[PATCH] io_uring: Remove CONFIG_EXPERT

[PATCH] io_uring: Remove CONFIG_EXPERT

[Justin M. Forbes]

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.

Signed-off-by: Justin M. Forbes <jforbes@fedoraproject.org>
---
 init/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/init/Kconfig b/init/Kconfig
index 1ea12c64e4c9..0decca696bf7 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1621,7 +1621,7 @@ config AIO
 	  this option saves about 7k.

 config IO_URING
-	bool "Enable IO uring support" if EXPERT
+	bool "Enable IO uring support"
 	select IO_WQ
 	default y
 	help
-- 
2.31.1

Re: [PATCH] io_uring: Remove CONFIG_EXPERT

[Pavel Begunkov]

On 5/26/21 11:34 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.

Acked-by: Pavel Begunkov <asml.silence@gmail.com>


> Signed-off-by: Justin M. Forbes <jforbes@fedoraproject.org>
> ---
>  init/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index 1ea12c64e4c9..0decca696bf7 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1621,7 +1621,7 @@ config AIO
>  	  this option saves about 7k.
> 
>  config IO_URING
> -	bool "Enable IO uring support" if EXPERT
> +	bool "Enable IO uring support"
>  	select IO_WQ
>  	default y
>  	help
> 

-- 
Pavel Begunkov

Re: [PATCH] io_uring: Remove CONFIG_EXPERT

[Jens Axboe]

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.

-- 
Jens Axboe

Re: [PATCH] io_uring: Remove CONFIG_EXPERT

[Justin Forbes]

On Thu, May 27, 2021 at 8:43 AM Jens Axboe <axboe@kernel.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.

Justin

Re: [PATCH] io_uring: Remove CONFIG_EXPERT

[Jens Axboe]

On 5/27/21 8:12 AM, Justin Forbes wrote:
> On Thu, May 27, 2021 at 8:43 AM Jens Axboe <axboe@kernel.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.

-- 
Jens Axboe

Re: [PATCH] io_uring: Remove CONFIG_EXPERT

[Justin Forbes]

On Thu, May 27, 2021 at 9:19 AM Jens Axboe <axboe@kernel.dk> wrote:
>
> On 5/27/21 8:12 AM, Justin Forbes wrote:
> > On Thu, May 27, 2021 at 8:43 AM Jens Axboe <axboe@kernel.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.

Justin

RE: [PATCH] io_uring: Remove CONFIG_EXPERT

[David Laight]

From: Justin Forbes
> Sent: 27 May 2021 17:01
> 
> On Thu, May 27, 2021 at 9:19 AM Jens Axboe <axboe@kernel.dk> wrote:
> >
> > On 5/27/21 8:12 AM, Justin Forbes wrote:
> > > On Thu, May 27, 2021 at 8:43 AM Jens Axboe <axboe@kernel.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.

Someone might want to disable things like IO_URING for an embedded
system just to remove code that might have possible attack vectors
and isn't required by the subset of kernel features they need.

If turning on 'EXPERT' makes extra config options visible this is ok.
But if that changes the defaults it gets to be a real PITA.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH] io_uring: Remove CONFIG_EXPERT

[Justin Forbes]

On Thu, May 27, 2021 at 11:01 AM Justin Forbes <jforbes@redhat.com> wrote:
>
> On Thu, May 27, 2021 at 9:19 AM Jens Axboe <axboe@kernel.dk> wrote:
> >
> > On 5/27/21 8:12 AM, Justin Forbes wrote:
> > > On Thu, May 27, 2021 at 8:43 AM Jens Axboe <axboe@kernel.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

Re: [PATCH] io_uring: Remove CONFIG_EXPERT

[Jens Axboe]

On 6/3/21 9:43 AM, Justin Forbes wrote:
> On Thu, May 27, 2021 at 11:01 AM Justin Forbes <jforbes@redhat.com> wrote:
>>
>> On Thu, May 27, 2021 at 9:19 AM Jens Axboe <axboe@kernel.dk> wrote:
>>>
>>> On 5/27/21 8:12 AM, Justin Forbes wrote:
>>>> On Thu, May 27, 2021 at 8:43 AM Jens Axboe <axboe@kernel.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'.

I'm still going to disagree with that. In terms of security, io_uring
is in a much better spot than it was in the past. Arguably it should have
been easier to turn off when it went in, but that ship has sailed a long
time ago and the need now isn't really there imho. The lack of audit
isn't new and is something that'll be solved for the next release.

-- 
Jens Axboe