Re: [PATCH v2 3/4] mm/huge_memory: make min_order_for_split() always return an order

[David Hildenbrand (Red Hat)]

On 11/22/25 03:55, Zi Yan wrote:
> min_order_for_split() returns -EBUSY when the folio is truncated and cannot
> be split. In commit 77008e1b2ef7 ("mm/huge_memory: do not change
> split_huge_page*() target order silently"), memory_failure() does not
> handle it and pass -EBUSY to try_to_split_thp_page() directly.
> try_to_split_thp_page() returns -EINVAL since -EBUSY becomes 0xfffffff0 as
> new_order is unsigned int in __folio_split() and this large new_order is
> rejected as an invalid input. The code does not cause a bug.
> soft_offline_in_use_page() also uses min_order_for_split() but it always
> passes 0 as new_order for split.
>
> Fix it by making min_order_for_split() always return an order. When the
> given folio is truncated, namely folio->mapping == NULL, return 0 and let
> a subsequent split function handle the situation and return -EBUSY.
>
> Add kernel-doc to min_order_for_split() to clarify its use.
>
> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>

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

--
Cheers

David