linux-kernel - Re: [PATCH] resource, kunit: add dependency on SPARSEMEM

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Message-ID: <87h6a1rhzh.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date: Fri, 27 Sep 2024 09:41:06 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: Dan Williams <dan.j.williams@...el.com>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>,  Guenter Roeck
 <linux@...ck-us.net>,  Andrew Morton <akpm@...ux-foundation.org>,
  linux-kernel@...r.kernel.org,  Linus Torvalds
 <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] resource, kunit: add dependency on SPARSEMEM

Dan Williams <dan.j.williams@...el.com> writes:

> Huang, Ying wrote:
>> Geert Uytterhoeven <geert@...ux-m68k.org> writes:
>> 
>> > Hi Huang,
>> >
>> > On Tue, Sep 24, 2024 at 3:25 AM Huang, Ying <ying.huang@...el.com> wrote:
>> >> Guenter Roeck <linux@...ck-us.net> writes:
>> >> > On 9/23/24 05:58, Geert Uytterhoeven wrote:
>> >> >> Hi Günter,
>> >> >> On Mon, Sep 23, 2024 at 12:50 AM Guenter Roeck <linux@...ck-us.net>
>> >> >> wrote:
>> >> >>> Building allmodconfig images on systems with SPARSEMEM=n results in
>> >> >>> the following message.
>> >> >>>
>> >> >>> WARNING: unmet direct dependencies detected for GET_FREE_REGION
>> >> >>>    Depends on [n]: SPARSEMEM [=n]
>> >> >>>    Selected by [m]:
>> >> >>>    - RESOURCE_KUNIT_TEST [=m] && RUNTIME_TESTING_MENU [=y] && KUNIT [=m]
>> >
>> >> After Linus' fix for PHYSMEM_END, GET_FREE_REGION doesn't need to depend
>> >> on SPARSEMEM anymore.  So, I think we can remove the dependency.  Can
>> >> you check whether the following patch work for you on top of latest
>> >> upstream kernel (with Linus' fix).
>> >
>> > Yes it does, thanks!
>> >
>> > One remaining issue is that RESOURCE_KUNIT_TEST selects GET_FREE_REGION.
>> > IMHO merely enabling a test should not enable extra functionality
>> > in the kernel.  Can the individual test(s) that do depend on
>> > GET_FREE_REGION be protected by #ifdef CONFIG_GET_FREE_REGION instead?
>> 
>> After checking GET_FREE_REGION, I don't think that it's a special
>> functionality.  I guess it's selectable because it depends on SPARSEMEM
>> and to reduce code size.
>> 
>> Hi, Dan, please correct me if I'm wrong here.
>
> Right, the only reason it is selectable is just to be mindful is
> micro-bloat in kernel/resource.c for the small number of drivers that
> need that call.

Thanks for explanation.

>> So, to reduce #ifdef in .c file as much as possible and make code
>> simpler, I prefer to select it for RESOURCE_KUNIT_TEST.
>
> I agree with the result, but for a different rationale.
>
> RESOURCE_KUNIT_TEST is simply another "driver" that needs
> GET_FREE_REGION. So while I agree with the general idea that "enabling a
> test should not enable extra functionality", in this case the *test* is
> the extra functionality and GET_FREE_REGION comes along for the ride.

Thanks, this sounds totally reasonable for me.

--
Best Regards,
Huang, Ying