Re: A potential refcount issue during __folio_split

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

> BTW, in the folio world, I do not think it is possible to perform the aforementioned
> split_huge_page_to_list_to_order() pattern any more, since you always work on folio,
> the head. Unless there is a need of getting hold of a tail after-split folio after
> a folio split, the pattern would be:
> 
> tail_page = folio_page(folio, N);
> 
> folio_get(folio);
> folio_lock(folio);
> folio_split(folio, ..., /* new parameter: lock_at = */ tail_page, ...);
> tail_folio = page_folio(tail_page);
> folio_unlock(tail_folio);
> folio_put(tail_folio);

Agreed. Maybe it would be even nicer if the split function could return 
the new folio directly.

folio_get(folio);
folio_lock(folio);
split_folio = folio_split_XXX(folio, ..., tail_page, ...);
if (IS_ERR_VALUE(split_folio)) {
	...
}
folio_unlock(split_folio);
folio_put(split__folio);

-- 
Cheers,

David