Re: [Patch v2] mm/huge_memory: use end_folio to terminate anonymous folio remapping

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

On Mon, Dec 15, 2025 at 05:15:17PM +0800, Barry Song wrote:
>On Mon, Dec 15, 2025 at 4:43 PM Wei Yang <richard.weiyang@gmail.com> wrote:
>>
>> On Mon, Dec 15, 2025 at 10:31:15AM +0800, Barry Song wrote:
>> >On Mon, Dec 15, 2025 at 8:49 AM Wei Yang <richard.weiyang@gmail.com> 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>
>> >>
>> >> ---
>> >> v2: move folio assignment in loop
>> >> ---
>> >>  mm/huge_memory.c | 13 ++++---------
>> >>  1 file changed, 4 insertions(+), 9 deletions(-)
>> >>
>> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> >> index 40cf59301c21..fe812d9c7807 100644
>> >> --- a/mm/huge_memory.c
>> >> +++ b/mm/huge_memory.c
>> >> @@ -3423,20 +3423,15 @@ 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)
>> >>  {
>> >
>> >Do we actually see an improvement in readability or performance?
>> >The existing code feels a bit more readable to me; nr is clearly
>> >the number of pages :-)
>> >
>>
>> Hi, Barry,
>>
>> Thanks for your review.
>>
>> Currently end_folio has been used in __folio_split() and
>> __folio_freeze_and_split_unmapped() as a termination marker. So continue to
>> use end_folio here as a termination marker looks consistent and improves
>> readability to me.
>
>In both cases the variables are temporary, and they look fine within their
>own self-documented contexts.
>
>Now that we’re crossing two functions in the context of remap_page(), this
>doesn’t seem to be the case, though.
>

Thanks for your feedback.

>>
>> But yeah, this is my personal preference. If it is not the case, I am fine to
>> keep as it is now. :-)
>
>I personally find the existing code clearer, but I’m also okay if
>others like your new approach more.
>

Thanks

>Thanks
>Barry

-- 
Wei Yang
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