Re: [PATCH 1/1] mm/mm_init: compute hash mask with unsigned arithmetic

[Mike Rapoport]

Hi,

On Sun, Aug 09, 2026 at 08:31:19PM +0800, Longlong Xia wrote:
> From: Longlong Xia <xialonglong@xxxxxxxxxx>
> 
> alloc_large_system_hash() allows up to 2^31 buckets, so log2qty can
> reach 31. At that limit, the current expression relies on signed
> integer wrapping to produce the unsigned hash mask.
> 
> Use an unsigned literal so the mask is computed with unsigned
> arithmetic. Supported compiler settings already produce the same
> result, so this is a source-level cleanup with no functional change.

If complier already takes care of this then why do we want this patch?
 
> Assisted-by: Codex:gpt-5.6-sol
> Signed-off-by: Longlong Xia <xialonglong@xxxxxxxxxx>
> ---
>  mm/mm_init.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index 498d62c4ece3..1883fe923ffb 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -2469,7 +2469,7 @@ void *__init alloc_large_system_hash(const char *tablename,
>  	if (_hash_shift)
>  		*_hash_shift = log2qty;
>  	if (_hash_mask)
> -		*_hash_mask = (1 << log2qty) - 1;
> +		*_hash_mask = (1U << log2qty) - 1;
>  
>  	return table;
>  }
> -- 
> 2.43.0
> 

-- 
Sincerely yours,
Mike.