Re: [PATCH] mm: move bad zone checking before getting it

[David Hildenbrand <david@redhat.com>]

On 05.09.24 11:52, Wang Yibo wrote:
> When flags from gfp_zone() has an error combination, VM_BUG_ON() should firt know it before use it.

s/firt/first/

Please break long lines. (checkpatch.pl should have warned you)

> 
> Signed-off-by: Wang Yibo <wangyibo@uniontech.com>
> ---
>   include/linux/gfp.h | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index f53f76e0b17e..ca61b2440ab3 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -133,10 +133,11 @@ static inline enum zone_type gfp_zone(gfp_t flags)
>   {
>   	enum zone_type z;
>   	int bit = (__force int) (flags & GFP_ZONEMASK);
> +	VM_BUG_ON((GFP_ZONE_BAD >> bit) & 1);

Better use VM_WARN_ON_ONCE() instead while at it.

>   
>   	z = (GFP_ZONE_TABLE >> (bit * GFP_ZONES_SHIFT)) &
>   					 ((1 << GFP_ZONES_SHIFT) - 1);
> -	VM_BUG_ON((GFP_ZONE_BAD >> bit) & 1);
> +

Unrelated whitespace change.

>   	return z;
>   }
>   

But I don't see why we would want this change? It's not like the kernel 
would crash when calculating z.

Or is there some change in behavior I am missing?

-- 
Cheers,

David / dhildenb