linux-kernel - Re: [PATCH v3 3/6] mm/huge_memory: respect MADV_COLLAPSE with PR_THP_DISABLE_EXCEPT

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Message-ID: <cd99f0f2-260d-4494-bbf6-99daec3e0683@gmail.com>
Date: Tue, 5 Aug 2025 16:08:55 +0100
From: Usama Arif <usamaarif642@...il.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.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, ziy@...dia.com,
 laoar.shao@...il.com, dev.jain@....com, baolin.wang@...ux.alibaba.com,
 npache@...hat.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
Subject: Re: [PATCH v3 3/6] mm/huge_memory: respect MADV_COLLAPSE with
 PR_THP_DISABLE_EXCEPT_ADVISED


>> diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
>> index 9c1d6e49b8a9..cdda963a039a 100644
>> --- a/include/uapi/linux/prctl.h
>> +++ b/include/uapi/linux/prctl.h
>> @@ -185,7 +185,7 @@ struct prctl_mm_map {
>>  #define PR_SET_THP_DISABLE	41
>>  /*
>>   * Don't disable THPs when explicitly advised (e.g., MADV_HUGEPAGE /
>> - * VM_HUGEPAGE).
>> + * VM_HUGEPAGE, MADV_COLLAPSE).
>>   */
>>  # define PR_THP_DISABLE_EXCEPT_ADVISED	(1 << 1)
>>  #define PR_GET_THP_DISABLE	42
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index 85252b468f80..ef5ccb0ec5d5 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -104,7 +104,8 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
>>  {
>>  	const bool smaps = type == TVA_SMAPS;
>>  	const bool in_pf = type == TVA_PAGEFAULT;
>> -	const bool enforce_sysfs = type != TVA_FORCED_COLLAPSE;
>> +	const bool forced_collapse = type == TVA_FORCED_COLLAPSE;
>> +	const bool enforce_sysfs = !forced_collapse;
> 
> I guess as discussed we'll return to this.
> 

Thanks for the review!

Yes I have a follow up patch ready, will send that when things stabalize and this series
makes into mm-new.