Re: [PATCH v2] huge_memory: return -EINVAL in folio split functions when THP is disabled

[Zi Yan <ziy@nvidia.com>]

On 4 Sep 2025, at 5:51, Pankaj Raghav (Samsung) wrote:

> From: Pankaj Raghav <p.raghav@samsung.com>
>
> split_huge_page_to_list_[to_order](), split_huge_page() and
> try_folio_split() return 0 on success and error codes on failure.
>
> When THP is disabled, these functions return 0 indicating success even
> though an error code should be returned as it is not possible to split a
> folio when THP is disabled.
>
> Make all these functions return -EINVAL to indicate failure instead of
> 0. As large folios depend on CONFIG_THP, issue warning as this function
> should not be called without a large folio.
>
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> ---
> This issue was discovered while experimenting enabling large folios
> without THP and found that returning 0 in these functions is resulting in
> undefined behavior in truncate operations. This change fixes the issue.
>
>  include/linux/huge_mm.h | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
>
Acked-by: Zi Yan <ziy@nvidia.com>

Best Regards,
Yan, Zi