Re: [PATCH v3 2/4] mm/huge_memory: replace can_split_folio() with direct refcount calculation

[David Hildenbrand (Red Hat)]

>   static int __folio_freeze_and_split_unmapped(struct folio *folio, unsigned int new_order,
>   					     struct page *split_at, struct xa_state *xas,
>   					     struct address_space *mapping, bool do_lru,
>   					     struct list_head *list, enum split_type split_type,
> -					     pgoff_t end, int *nr_shmem_dropped, int extra_pins)
> +					     pgoff_t end, int *nr_shmem_dropped)
>   {
>   	struct folio *end_folio = folio_next(folio);
>   	struct folio *new_folio, *next;
> @@ -3782,7 +3773,7 @@ static int __folio_freeze_and_split_unmapped(struct folio *folio, unsigned int n
>   	VM_WARN_ON_ONCE(!mapping && end);
>   	/* Prevent deferred_split_scan() touching ->_refcount */
>   	ds_queue = folio_split_queue_lock(folio);
> -	if (folio_ref_freeze(folio, 1 + extra_pins)) {
> +	if (folio_ref_freeze(folio, folio_cache_ref_count(folio) + 1)) {
>   		struct swap_cluster_info *ci = NULL;
>   		struct lruvec *lruvec;
>   		int expected_refs;
> @@ -3853,7 +3844,7 @@ static int __folio_freeze_and_split_unmapped(struct folio *folio, unsigned int n
>   
>   			zone_device_private_split_cb(folio, new_folio);
>   
> -			expected_refs = folio_expected_ref_count(new_folio) + 1;
> +			expected_refs = folio_cache_ref_count(new_folio) + 1;
>   			folio_ref_unfreeze(new_folio, expected_refs);
>   
>   			if (do_lru)
> @@ -3897,7 +3888,7 @@ static int __folio_freeze_and_split_unmapped(struct folio *folio, unsigned int n
>   		 * Otherwise, a parallel folio_try_get() can grab @folio
>   		 * and its caller can see stale page cache entries.
>   		 */
> -		expected_refs = folio_expected_ref_count(folio) + 1;
> +		expected_refs = folio_cache_ref_count(folio) + 1;
>   		folio_ref_unfreeze(folio, expected_refs);

Can we just get rid of the expected_refs variable as well?

Apart from that LGTM, thanks!

Acked-by: David Hildenbrand (Red Hat) <david@xxxxxxxxxx>

--
Cheers

David