On Wed, Apr 06, 2016 at 10:40:19AM +0100, Tvrtko Ursulin wrote:
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@chris-wilson.co.uk Cc: dri-devel@lists.freedesktop.org Cc: Ville Syrjälä ville.syrjala@linux.intel.com Reviewed-by: Ville Syrjälä ville.syrjala@linux.intel.com Acked-by: Dave Airlie airlied@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;
?
Cargo-culting. I guess the only thought was to avoid the div-by-zero and to fallthrough to returning kmalloc(0) for equivalent behaviour. -Chris