Re: [Patch v3 2/2] mm/khugepaged: unify pmd folio installation with map_anon_folio_pmd()

[Wei Yang <richard.weiyang@gmail.com>]

On Wed, Oct 08, 2025 at 04:45:52PM +0200, David Hildenbrand wrote:
>On 08.10.25 11:54, Wei Yang wrote:
>> Currently we install pmd folio with map_anon_folio_pmd() in
>> __do_huge_pmd_anonymous_page() and do_huge_zero_wp_pmd(). While in
>> collapse_huge_page(), it is done with identical code except statistics
>> adjustment.
>> 
>> Unify the process with map_anon_folio_pmd() to install pmd folio. Split
>> it to map_anon_folio_pmd_pf() and map_anon_folio_pmd_nopf() to be used
>> in page fault or not respectively.
>> 
>> No functional change is intended.
>> 
>> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>> Cc: David Hildenbrand <david@redhat.com>
>> Cc: Lance Yang <lance.yang@linux.dev>
>> Cc: Dev Jain <dev.jain@arm.com>
>> Cc: Zi Yan <ziy@nvidia.com>
>> Cc: Usama Arif <usamaarif642@gmail.com>
>> Cc: Matthew Wilcox <willy@infradead.org>
>> Acked-by: David Hildenbrand <david@redhat.com>
>> Reviewed-by: Zi Yan <ziy@nvidia.com>
>> Acked-by: Lance Yang <lance.yang@linux.dev>
>> 
>> ---
>> v3:
>>    * add static inline and put bracket into separate lines
>>    * rebase on latest mm-new
>> v2:
>>    * split map_anon_folio_pmd_[no]pf() suggested by Matthew
>> ---
>>   include/linux/huge_mm.h |  7 +++++++
>>   mm/huge_memory.c        | 14 ++++++++++----
>>   mm/khugepaged.c         |  9 +--------
>>   3 files changed, 18 insertions(+), 12 deletions(-)
>> 
>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
>> index bb48cb50c0ec..588e3522a1d0 100644
>> --- a/include/linux/huge_mm.h
>> +++ b/include/linux/huge_mm.h
>> @@ -542,6 +542,8 @@ void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address,
>>   			   pmd_t *pmd, bool freeze);
>>   bool unmap_huge_pmd_locked(struct vm_area_struct *vma, unsigned long addr,
>>   			   pmd_t *pmdp, struct folio *folio);
>> +void map_anon_folio_pmd_nopf(struct folio *folio, pmd_t *pmd,
>> +		struct vm_area_struct *vma, unsigned long haddr);
>>   #else /* CONFIG_TRANSPARENT_HUGEPAGE */
>> @@ -633,6 +635,11 @@ static inline bool unmap_huge_pmd_locked(struct vm_area_struct *vma,
>>   	return false;
>>   }
>> +static inline void map_anon_folio_pmd_nopf(struct folio *folio, pmd_t *pmd,
>> +		struct vm_area_struct *vma, unsigned long haddr)
>> +{
>> +}
>> +
>
>Thinking again, maybe you don't even need this stub? Any calling code should
>be guarded by CONFIG_TRANSPARENT_HUGEPAGE.
>

I think you are right.

I have removed the stub and build with/out CONFIG_TRANSPARENT_HUGEPAGE, both
are fine.

@Andrew, would you mind removing the above static inline stub? Thanks.

>-- 
>Cheers
>
>David / dhildenb

-- 
Wei Yang
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