Re: [PATCHv6 1/8] zsmalloc: add to mm/

Seth Jennings
2013-02-21T22:39:56Z

On 02/21/2013 02:36 PM, Cody P Schafer wrote:
> On Wed, Feb 20, 2013 at 04:04:41PM -0600, Seth Jennings wrote:
>> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
>> +#define MAX(a, b) ((a) >= (b) ? (a) : (b))
>> +/* ZS_MIN_ALLOC_SIZE must be multiple of ZS_ALIGN */
>> +#define ZS_MIN_ALLOC_SIZE \
>> + MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
>
> Could you use the max(a,b) defined in include/linux/kernel.h?
>

Andrew Morton made the same point. We can't use max() or max_t()
because the value of ZS_MIN_ALLOC_SIZE is used to derive the value of
ZS_SIZE_CLASSES which is used to size an array in struct zs_pool.

So the expression must be completely evaluated to a number by the
precompiler.

Thanks,
Seth