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

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

Sorry Wei,

I know this is small, but can we not be doing these kinds of fiddly patches late
in -rc7 please?

Thanks, Lorenzo

On Thu, Nov 27, 2025 at 02:24:36AM +0000, 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);
>  }
>
>  static void lru_add_split_folio(struct folio *folio, struct folio *new_folio,
> @@ -4066,7 +4060,7 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
>  	if (!ret && is_anon && !folio_is_device_private(folio))
>  		remap_flags = RMP_USE_SHARED_ZEROPAGE;
>
> -	remap_page(folio, 1 << old_order, remap_flags);
> +	remap_page(folio, end_folio, remap_flags);
>
>  	/*
>  	 * Unlock all after-split folios except the one containing
> --
> 2.34.1
>
>