[PATCH net-next v1] mm: fix build on powerpc with GCC 14

[Matthew Wilcox]

On Fri, Sep 13, 2024 at 07:20:36PM +0000, Mina Almasry wrote:
> +++ b/include/linux/page-flags.h
> @@ -239,8 +239,8 @@ static inline unsigned long _compound_head(const struct page *page)
>  {
>  	unsigned long head = READ_ONCE(page->compound_head);
>  
> -	if (unlikely(head & 1))
> -		return head - 1;
> +	if (unlikely(head & 1UL))
> +		return head & ~1UL;
>  	return (unsigned long)page_fixed_fake_head(page);

NAK, that pessimises compound_head().