Re: [PATCH v2] sparc: Avoid -Wunused-but-set-parameter in clear_user_page()

[Andreas Larsson]

On 2026-05-25 10:36, Thomas Weißschuh wrote:
> The loop in clear_user_pages() iterates over all pages and calls
> clear_user_page() for each of them. During the loop "vaddr" is modified.
> However on sparc clear_user() is a macro which does not use "vaddr".
> The compiler sees a variable which is modified but never used and emits
> a warning for that:
> 
> 	include/linux/highmem.h: In function 'clear_user_pages':
> 	include/linux/highmem.h:234:63: warning: parameter 'vaddr' set but not used [-Wunused-but-set-parameter=]
> 		static inline void clear_user_pages(void *addr, unsigned long vaddr,
> 
> Other architectures use an inline function for clear_user_page() which
> avoids the warning. This is not possible on sparc, as
> sparc_flush_page_to_ram() is not yet declared where clear_user_page() is
> defined. Including cacheflush_32.h will trigger recursive and lots of
> other issues.
> 
> So hide the warning with a cast to (void) instead.
> 
> While we are here, do the same for copy_user_page().
> 
> Fixes: 62a9f5a85b98 ("mm: introduce clear_pages() and clear_user_pages()")
> Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
> ---
> Changes in v2:
> - Put parens around vaddr.
> - Link to v1: https://patch.msgid.link/20260524-sparc-clear_user_page-v1-1-baa5b90e5d0d@xxxxxxxxxxxxxx
> ---
>  arch/sparc/include/asm/page_32.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/sparc/include/asm/page_32.h b/arch/sparc/include/asm/page_32.h
> index c1bccbedf567..9f0b54f70908 100644
> --- a/arch/sparc/include/asm/page_32.h
> +++ b/arch/sparc/include/asm/page_32.h
> @@ -20,10 +20,12 @@
>  #define clear_user_page(addr, vaddr, page)	\
>  	do { 	clear_page(addr);		\
>  		sparc_flush_page_to_ram(page);	\
> +		(void)(vaddr);			\
>  	} while (0)
>  #define copy_user_page(to, from, vaddr, page)	\
>  	do {	copy_page(to, from);		\
>  		sparc_flush_page_to_ram(page);	\
> +		(void)(vaddr);			\
>  	} while (0)
>  
>  /* The following structure is used to hold the physical
> 
> ---
> base-commit: d87895ce6e45997825cfe1b3565a1843e8ac8011
> change-id: 20260523-sparc-clear_user_page-7448669a2476

Reviewed-by: Andreas Larsson <andreas@xxxxxxxxxxx>

Picking this up to my for-next.

Thanks,
Andreas