Re: [PATCH v3 1/4] mm/huge_memory: change folio_split_supported() to folio_check_splittable()

[David Hildenbrand (Red Hat)]

> -	/*
> -	 * Folios that just got truncated cannot get split. Signal to the
> -	 * caller that there was a race.
> -	 *
> -	 * TODO: this will also currently refuse shmem folios that are in the
> -	 * swapcache.
> -	 */
> -	if (!is_anon && !folio->mapping)
> -		return -EBUSY;
> -
>   	if (new_order >= old_order)
>   		return -EINVAL;
>   
> -	if (!folio_split_supported(folio, new_order, split_type, /* warn = */ true))
> -		return -EINVAL;
> -
> -	is_hzp = is_huge_zero_folio(folio);
> -	if (is_hzp) {
> -		pr_warn_ratelimited("Called split_huge_page for huge zero page\n");
> -		return -EBUSY;

As we are changing that case to a VM_WARN_ONCE(), is there some path 
where we might trigger that?

I'm wondering about the split_huge_pages_all() function in particular. I 
guess the "!folio_test_lru(folio)" would protect us?

Apart from that LGTM

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

--
Cheers

David