linux-kernel - Re: [PATCH v5 6/7] selftests: prctl: introduce tests for disabling THPs completely

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Message-ID: <5a3fd8fd-d215-464c-9e84-b8051c16f07f@gmail.com>
Date: Fri, 5 Sep 2025 20:44:10 +0100
From: Usama Arif <usamaarif642@...il.com>
To: Mark Brown <broonie@...nel.org>, Zi Yan <ziy@...dia.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, david@...hat.com,
 linux-mm@...ck.org, linux-fsdevel@...r.kernel.org, corbet@....net,
 rppt@...nel.org, surenb@...gle.com, mhocko@...e.com, hannes@...xchg.org,
 baohua@...nel.org, shakeel.butt@...ux.dev, riel@...riel.com,
 laoar.shao@...il.com, dev.jain@....com, baolin.wang@...ux.alibaba.com,
 npache@...hat.com, lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com,
 ryan.roberts@....com, vbabka@...e.cz, jannh@...gle.com,
 Arnd Bergmann <arnd@...db.de>, sj@...nel.org, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org, kernel-team@...a.com, Aishwarya.TCV@....com
Subject: Re: [PATCH v5 6/7] selftests: prctl: introduce tests for disabling
 THPs completely



On 05/09/2025 20:40, Usama Arif wrote:
> 
> 
> On 05/09/2025 19:02, Mark Brown wrote:
>> On Fri, Sep 05, 2025 at 01:55:53PM -0400, Zi Yan wrote:
>>> On 5 Sep 2025, at 13:43, Mark Brown wrote:
>>
>>>> but the header there is getting ignored AFAICT.  Probably the problem is
>>>> fairly obvious and I'm just being slow - I'm not quite 100% at the
>>>> minute.
>>
>>> prctl_thp_disable.c uses “#include <sys/mman.h>” but asm-generic/mman-common.h
>>> is included in asm/mman.h. And sys/mman.h gets MADV_COLLAPSE from
>>> bits/mman-linux.h. Maybe that is why?
>>
>> Ah, of course - if glibc is reproducing the kernel definitions rather
>> than including the kernel headers to get them then that'd do it.
>> Probably the test needs to locally define the new MADV_COLLAPSE for
>> glibc compatibility, IME trying to directly include the kernel headers
>> when glibc doesn't normally use them tends to blow up on you sooner or
>> later.
>>
>> I knew it'd be something simple, thanks.
> 
> Hi Mark,
> 
> Thanks for raising this. I think doing 
> 
> diff --git a/tools/testing/selftests/mm/prctl_thp_disable.c b/tools/testing/selftests/mm/prctl_thp_disable.c
> index 89ed0d7db1c16..0afcdbad94f3d 100644
> --- a/tools/testing/selftests/mm/prctl_thp_disable.c
> +++ b/tools/testing/selftests/mm/prctl_thp_disable.c
> @@ -9,6 +9,7 @@
>  #include <string.h>
>  #include <unistd.h>
>  #include <sys/mman.h>
> +#include <linux/mman.h>
>  #include <sys/prctl.h>
>  #include <sys/wait.h>
> 
> 
> should fix this issue?
> 
> Thanks
> Usama


If that fixes it, please feel free to send a patch or let me know and I will send it.

Thanks!
Usama