Re: [PATCH 1/1] mm/rmap: add CONFIG_MM_ID guard for folio_test_large_maybe_mapped_shared()

[David Hildenbrand]

On 17.04.25 14:49, Lance Yang wrote:
> Add a compile-time check to make sure folio_test_large_maybe_mapped_shared()
> is only used with CONFIG_MM_ID enabled, as it directly accesses the _mm_ids
> field that only works under CONFIG_MM_ID.
>
> Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
> Signed-off-by: Mingzhe Yang <mingzhe.yang@xxxxxx>

^ should that be here?

> Signed-off-by: Lance Yang <ioworker0@xxxxxxxxx>
> ---
>   include/linux/page-flags.h | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index d3909cb1e576..6bd9b9043976 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -1232,6 +1232,8 @@ static inline int folio_has_private(const struct folio *folio)
>   
>   static inline bool folio_test_large_maybe_mapped_shared(const struct folio *folio)
>   {
> +	/* This function should never be called without CONFIG_MM_ID enabled. */
> +	BUILD_BUG_ON(!IS_ENABLED(CONFIG_MM_ID));
>   	return test_bit(FOLIO_MM_IDS_SHARED_BITNUM, &folio->_mm_ids);
>   }
>   #undef PF_ANY

That should work. I can throw this into a cross-compile setup later if I 
get to it.

Acked-by: David Hildenbrand <david@xxxxxxxxxx>

--
Cheers,

David / dhildenb