Re: [PATCH v3 11/18] mm/huge_memory: allow splitting mappingless swap cache folios

[David Hildenbrand (Arm)]

> +	if (anon_vma) {
>  		if (!ret && !folio_is_device_private(folio))
>  			ttu_flags = TTU_USE_SHARED_ZEROPAGE;
>  		remap_page(folio, 1 << old_order, ttu_flags);
> @@ -4259,6 +4261,7 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
>  		struct page *split_at, struct page *lock_at,
>  		struct list_head *list, enum split_type split_type)
>  {
> +	bool is_swapcache = folio_test_swapcache(folio);
>  	struct folio *end_folio = folio_next(folio);
>  	bool is_anon = folio_test_anon(folio);
>  	int old_order = folio_order(folio);
> @@ -4285,8 +4288,11 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
>  	}
>  
>  	if (is_anon)
> -		ret = __folio_split_unmap_and_freeze_anon(folio, new_order, split_at, true,
> -							  true, list, split_type);
> +		ret = __folio_split_unmap_and_freeze(folio, new_order, split_at, true,
> +						     true, list, split_type);
> +	else if (is_swapcache)
> +		ret = __folio_split_unmap_and_freeze(folio, new_order, split_at, true,
> +						     false, list, split_type);

These two boolean parameters are really a pain. There must be a better way.

Also, I don't like that __folio_split_unmap_and_freeze() sounds generic again.

There must be a better way for that as well. We had a clean split and now we
mangle it again.


... but I am just before my PTO and out of puff, so others can brainstorm on how
to do this cleaner :)

-- 
Cheers,

David