Re: [PATCH v5 08/17] mm/huge_memory: move unmap and remap into the split helpers

["David Hildenbrand (Arm)" <david@kernel.org>]

On 9/14/26 19:14, Kairui Song via B4 Relay wrote:
> From: Kairui Song <kasong@tencent.com>
> 
> To prepare for further cleanup, move the unmap/remap handling from
> __folio_split() into the split helpers.  Only anon folios need to
> be remapped, so remap_page() is now only called for anon splits and
> the anon check in remap_page() is redundant and can be removed.
> 
> Reviewed-by: Zi Yan <ziy@nvidia.com>
> Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
> Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
> Signed-off-by: Kairui Song <kasong@tencent.com>
> ---
>  mm/huge_memory.c | 36 ++++++++++++++++++++++--------------
>  1 file changed, 22 insertions(+), 14 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 5ba3bcdfc42d..1749905ade6a 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -3641,9 +3641,6 @@ static void remap_page(struct folio *folio, unsigned long nr, int flags)
>  {
>  	int i = 0;
>  
> -	/* If unmap_folio() uses try_to_migrate() on file, remove this check */
> -	if (!folio_test_anon(folio))
> -		return;
>  	for (;;) {
>  		remove_migration_ptes(folio, folio, TTU_RMAP_LOCKED | flags);
>  		i += folio_nr_pages(folio);
> @@ -4017,15 +4014,23 @@ static int __folio_freeze_split_anon(struct folio *folio,
>  {
>  	struct folio *end_folio = folio_next(folio);
>  	struct swap_cluster_info *ci = NULL;
> +	int old_order = folio_order(folio);

const

>  	struct folio *new_folio, *next;
> +	enum ttu_flags ttu_flags = 0;
>  	struct lruvec *lruvec;
> +	bool need_remap = false;
>  	int ret = 0;
>  

[...]

>  
>  	return ret;
>  }
> @@ -4106,6 +4117,8 @@ static int __folio_freeze_split_file(struct folio *folio,
>  	if (shmem_mapping(mapping))
>  		end = shmem_fallocend(mapping->host, end);
>  
> +	unmap_folio(folio);
> +
>  	xas_lock_irq(xas);
>  
>  	/*
> @@ -4190,8 +4203,11 @@ static int __folio_freeze_split_file(struct folio *folio,
>  
>  	if (do_lru)
>  		lruvec_unlock(lruvec);
> -
>  fail:
> +	/*
> +	 * If we want to use try_to_migrate() on file in unmap_folio,
> +	 * remember to add remap_page() and adapt it.

Again, remove that entirely.

> +	 */
>  	xas_unlock_irq(xas);
>  	if (nr_shmem_dropped)
>  		shmem_uncharge(mapping->host, nr_shmem_dropped);

Acked-by: David Hildenbrand (Arm) <david@kernel.org>

-- 
Cheers,

David