drm/lease: look at ->universal_planes only once

It's lockless, and userspace might chance it underneath us. That's not
really a problem, all userspace gets is a slightly dysfunctional
lease with the current code. But this might change, and gcc might
decide to reload a few too many times, and then boom. So better safe
than sorry.

v2: Remove the now unused lessor_priv argument from validate_lease()
(Keith).

v3: Actually add everything ... silly me.

Cc: Keith Packard <keithp@keithp.com>
Cc: Dave Airlie <airlied@gmail.com>
Acked-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181105101211.22737-1-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_lease.c

@@ -353,9 +353,9 @@ void drm_lease_revoke(struct drm_master *top)
 }
 
 static int validate_lease(struct drm_device *dev,
-			  struct drm_file *lessor_priv,
 			  int object_count,
-			  struct drm_mode_object **objects)
+			  struct drm_mode_object **objects,
+			  bool universal_planes)
 {
 	int o;
 	int has_crtc = -1;
@@ -372,14 +372,14 @@ static int validate_lease(struct drm_device *dev,
 		if (objects[o]->type == DRM_MODE_OBJECT_CONNECTOR && has_connector == -1)
 			has_connector = o;
 
-		if (lessor_priv->universal_planes) {
+		if (universal_planes) {
 			if (objects[o]->type == DRM_MODE_OBJECT_PLANE && has_plane == -1)
 				has_plane = o;
 		}
 	}
 	if (has_crtc == -1 || has_connector == -1)
 		return -EINVAL;
-	if (lessor_priv->universal_planes && has_plane == -1)
+	if (universal_planes && has_plane == -1)
 		return -EINVAL;
 	return 0;
 }
@@ -393,6 +393,8 @@ static int fill_object_idr(struct drm_device *dev,
 	struct drm_mode_object **objects;
 	u32 o;
 	int ret;
+	bool universal_planes = READ_ONCE(lessor_priv->universal_planes);
+
 	objects = kcalloc(object_count, sizeof(struct drm_mode_object *),
 			  GFP_KERNEL);
 	if (!objects)
@@ -421,7 +423,7 @@ static int fill_object_idr(struct drm_device *dev,
 		}
 	}
 
-	ret = validate_lease(dev, lessor_priv, object_count, objects);
+	ret = validate_lease(dev, object_count, objects, universal_planes);
 	if (ret) {
 		DRM_DEBUG_LEASE("lease validation failed\n");
 		goto out_free_objects;
@@ -448,7 +450,7 @@ static int fill_object_idr(struct drm_device *dev,
 					object_id, ret);
 			goto out_free_objects;
 		}
-		if (obj->type == DRM_MODE_OBJECT_CRTC && !lessor_priv->universal_planes) {
+		if (obj->type == DRM_MODE_OBJECT_CRTC && !universal_planes) {
 			struct drm_crtc *crtc = obj_to_crtc(obj);
 			ret = idr_alloc(leases, &drm_lease_idr_object, crtc->primary->base.id, crtc->primary->base.id + 1, GFP_KERNEL);
 			if (ret < 0) {