drm/i915/gem: sanity check object size in gem_create

Depending on the regions min_page_size we might need to adjust the
object size, ensure this matches our expectations.
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20210114182402.840247-2-matthew.auld@intel.com

drivers/gpu/drm/i915/gem/i915_gem_create.c

@@ -32,6 +32,8 @@ i915_gem_create(struct drm_file *file,
 	if (IS_ERR(obj))
 		return PTR_ERR(obj);
 
+	GEM_BUG_ON(size != obj->base.size);
+
 	ret = drm_gem_handle_create(file, &obj->base, &handle);
 	/* drop reference from allocate - handle holds it now */
 	i915_gem_object_put(obj);