drm: modify drm_global_item_ref to avoid two times of writing ref->object

In previous drm_global_item_ref, there are two times of writing
ref->object if item->refcount is 0. So this patch does a minor update
to put alloc and init ref firstly, and then to modify the item of glob
array. Use "else" to avoid two times of writing ref->object. It can
make the code logic more clearly.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/drm_global.c

@@ -65,30 +65,34 @@ void drm_global_release(void)
 
 int drm_global_item_ref(struct drm_global_reference *ref)
 {
-	int ret;
+	int ret = 0;
 	struct drm_global_item *item = &glob[ref->global_type];
 
 	mutex_lock(&item->mutex);
 	if (item->refcount == 0) {
-		item->object = kzalloc(ref->size, GFP_KERNEL);
-		if (unlikely(item->object == NULL)) {
+		ref->object = kzalloc(ref->size, GFP_KERNEL);
+		if (unlikely(ref->object == NULL)) {
 			ret = -ENOMEM;
-			goto out_err;
+			goto error_unlock;
 		}
-
-		ref->object = item->object;
 		ret = ref->init(ref);
 		if (unlikely(ret != 0))
-			goto out_err;
+			goto error_free;
 
+		item->object = ref->object;
+	} else {
+		ref->object = item->object;
 	}
+
 	++item->refcount;
-	ref->object = item->object;
 	mutex_unlock(&item->mutex);
 	return 0;
-out_err:
+
+error_free:
+	kfree(ref->object);
+	ref->object = NULL;
+error_unlock:
 	mutex_unlock(&item->mutex);
-	item->object = NULL;
 	return ret;
 }
 EXPORT_SYMBOL(drm_global_item_ref);