[Intel-gfx] [PATCH 5/6] drm,i915: Introduce drm_malloc_gfp()

[Tvrtko Ursulin]

On 05/04/16 14:05, Chris Wilson wrote:
> On Tue, Apr 05, 2016 at 01:57:36PM +0100, Chris Wilson wrote:
>> I have instances where I want to use drm_malloc_ab() but with a custom
>> gfp mask. And with those, where I want a temporary allocation, I want to
>> try a high-order kmalloc() before using a vmalloc().
>>
>> So refactor my usage into drm_malloc_gfp().
>>
>> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
>> Cc: dri-devel at lists.freedesktop.org
>> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
>> Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
>> Acked-by: Dave Airlie <airlied at redhat.com>
>
>> +static __inline__ void *drm_malloc_gfp(size_t nmemb, size_t size, gfp_t gfp)
>> +{
>> +	if (size != 0 && nmemb > SIZE_MAX / size)
>> +		return NULL;
>
> I know Dave G. has some fancy code to detect when the size parameter is
> not constant, but one thing I noticed was that gcc would uninline this
> function and we would lose the constant folding. Is there anything we
> can do to convince gcc to avoid a div here (other than pure macro)?

Don't know, apart from maybe _always_inline if it is not considered too big.

But I wanted to ask, why it is interesting to allow size == 0 ? Why not:

	if (size == 0 || nmemb > SIZE_MAX / size)
		return NULL;

?

Regards,

Tvrtko