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

[David Hildenbrand <david@redhat.com>]

On 05.09.25 10:13, Pankaj Raghav wrote:
> On 9/4/25 17:26, Kiryl Shutsemau wrote:
>> On Thu, Sep 04, 2025 at 11:51:29AM +0200, 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>
>>
>> Acked-by: Kiryl Shutsemau <kas@kernel.org>
>>
>> Just curious, did you give BUILD_BUG() a try?
>>
> 
> Yes, I tried BUILD_BUG() but it actually fails the build because truncate_inode_partial_folio()
> calls try_folio_split().
> 
> It won't be called in runtime because there is a check for large folios before we call this
> function. So a runtime warning is better in this case.

Right, folio_test_large() is not compiled out.

-- 
Cheers

David / dhildenb