Re: [PATCH v2 3/3] slab: use logical instead of bitwise operation in kmalloc_type()

[Andrew Morton]

On Fri,  9 Nov 2018 10:35:34 +0100 Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote:

> The operation here really is more logical than bitwise, even if
> due to the setup the bitwise operation works fine. However, this
> causes a complaint from sparse that the operation doesn't really
> make sense due to the not.
> 
> Use a logical and instead of bitwise.
> 
> In my (somewhat unscientific) test this caused no differences in
> the generated code.
> 
> ...
>
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -329,7 +329,7 @@ static __always_inline enum kmalloc_cache_type kmalloc_type(gfp_t flags)
>  	 * If an allocation is both __GFP_DMA and __GFP_RECLAIMABLE, return
>  	 * KMALLOC_DMA and effectively ignore __GFP_RECLAIMABLE
>  	 */
> -	return type_dma + (is_reclaimable & !is_dma) * KMALLOC_RECLAIM;
> +	return type_dma + (is_reclaimable && !is_dma) * KMALLOC_RECLAIM;
>  }
>  
>  /*

Thanks.  There's presently a bit of head-scratching going on over this.
http://lkml.kernel.org/r/20181105204000.129023-1-bvanassche@xxxxxxx -
please feel free to weigh in ;)