Re: [PATCH] mm/huge_memory: use end_folio to terminate anonymous folio remapping

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

On Thu, Nov 27, 2025 at 08:22:26AM +0100, David Hildenbrand (Red Hat) wrote:
>On 11/27/25 03:24, Wei Yang wrote:
>> After splitting a large folio, it is necessary to remap the resulting
>> anonymous folios.
>> 
>> The current implementation determines the end of the remapping process
>> by counting the number of pages that have been processed.
>> 
>> Since the final folio in the sequence, end_folio, is already known and
>> tracked, this commit refactors the remapping loop to leverage end_folio
>> as the termination marker.
>> 
>> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>> Cc: Zi Yan <ziy@nvidia.com>
>> ---
>>   mm/huge_memory.c | 14 ++++----------
>>   1 file changed, 4 insertions(+), 10 deletions(-)
>> 
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index 553bfa961fce..afc7b2f91e99 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -3414,20 +3414,14 @@ bool unmap_huge_pmd_locked(struct vm_area_struct *vma, unsigned long addr,
>>   	return __discard_anon_folio_pmd_locked(vma, addr, pmdp, folio);
>>   }
>> -static void remap_page(struct folio *folio, unsigned long nr, int flags)
>> +static void remap_page(struct folio *folio, struct folio *end_folio, int flags)
>>   {
>> -	int i = 0;
>> -
>>   	/* If unmap_folio() uses try_to_migrate() on file, remove this check */
>>   	if (!folio_test_anon(folio))
>>   		return;
>> -	for (;;) {
>> +	do {
>>   		remove_migration_ptes(folio, folio, RMP_LOCKED | flags);
>> -		i += folio_nr_pages(folio);
>> -		if (i >= nr)
>> -			break;
>> -		folio = folio_next(folio);
>> -	}
>> +	} while ((folio = folio_next(folio)) != end_folio);
>
>Rather ugly.
>
>Nothing lost by just keeping "folio = folio_next(folio);" in the loop and
>focusing on what your patch documents.
>
>But as Lorenzo said, the time for such cleanups is after most of the current
>stuff was merged in the upcoming merge window.

Sure.

>
>-- 
>Cheers
>
>David

-- 
Wei Yang
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