drm/atomic: Cleanup on error properly in the atomic ioctl.

It's probably allowed to leave old_fb set to garbage when unlocking,
but to prevent undefined behavior unset it just in case.

Also crtc_state->event could be NULL on memory allocation failure,
in which case event_space is increased for no reason.

Note: Contains some general simplification of the cleanup code too.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
[danvet: Add note about the other changes in here. And fix long line
while at it.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_atomic.c

@@ -1463,18 +1463,18 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 
 		if (get_user(obj_id, objs_ptr + copied_objs)) {
 			ret = -EFAULT;
-			goto fail;
+			goto out;
 		}
 
 		obj = drm_mode_object_find(dev, obj_id, DRM_MODE_OBJECT_ANY);
 		if (!obj || !obj->properties) {
 			ret = -ENOENT;
-			goto fail;
+			goto out;
 		}
 
 		if (get_user(count_props, count_props_ptr + copied_objs)) {
 			ret = -EFAULT;
-			goto fail;
+			goto out;
 		}
 
 		copied_objs++;
@@ -1486,25 +1486,25 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 
 			if (get_user(prop_id, props_ptr + copied_props)) {
 				ret = -EFAULT;
-				goto fail;
+				goto out;
 			}
 
 			prop = drm_property_find(dev, prop_id);
 			if (!prop) {
 				ret = -ENOENT;
-				goto fail;
+				goto out;
 			}
 
 			if (copy_from_user(&prop_value,
 					   prop_values_ptr + copied_props,
 					   sizeof(prop_value))) {
 				ret = -EFAULT;
-				goto fail;
+				goto out;
 			}
 
 			ret = atomic_set_prop(state, obj, prop, prop_value);
 			if (ret)
-				goto fail;
+				goto out;
 
 			copied_props++;
 		}
@@ -1523,7 +1523,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 			e = create_vblank_event(dev, file_priv, arg->user_data);
 			if (!e) {
 				ret = -ENOMEM;
-				goto fail;
+				goto out;
 			}
 
 			crtc_state->event = e;
@@ -1533,6 +1533,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 	if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) {
 		ret = drm_atomic_check_only(state);
 		/* _check_only() does not free state, unlike _commit() */
+		if (!ret)
 			drm_atomic_state_free(state);
 	} else if (arg->flags & DRM_MODE_ATOMIC_NONBLOCK) {
 		ret = drm_atomic_async_commit(state);
@@ -1540,6 +1541,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 		ret = drm_atomic_commit(state);
 	}
 
+out:
 	/* if succeeded, fixup legacy plane crtc/fb ptrs before dropping
 	 * locks (ie. while it is still safe to deref plane->state).  We
 	 * need to do this here because the driver entry points cannot
@@ -1552,41 +1554,35 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 				drm_framebuffer_reference(new_fb);
 			plane->fb = new_fb;
 			plane->crtc = plane->state->crtc;
-		} else {
-			plane->old_fb = NULL;
-		}
-		if (plane->old_fb) {
+
+			if (plane->old_fb)
 				drm_framebuffer_unreference(plane->old_fb);
-			plane->old_fb = NULL;
 		}
+		plane->old_fb = NULL;
 	}
 
-	drm_modeset_drop_locks(&ctx);
-	drm_modeset_acquire_fini(&ctx);
-
-	return ret;
-
-fail:
-	if (ret == -EDEADLK)
-		goto backoff;
+	if (ret == -EDEADLK) {
+		drm_atomic_state_clear(state);
+		drm_modeset_backoff(&ctx);
+		goto retry;
+	}
 
+	if (ret) {
 		if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT) {
 			for_each_crtc_in_state(state, crtc, crtc_state, i) {
-			destroy_vblank_event(dev, file_priv, crtc_state->event);
-			crtc_state->event = NULL;
+				if (!crtc_state->event)
+					continue;
+
+				destroy_vblank_event(dev, file_priv,
+						     crtc_state->event);
 			}
 		}
 
 		drm_atomic_state_free(state);
+	}
 
 	drm_modeset_drop_locks(&ctx);
 	drm_modeset_acquire_fini(&ctx);
 
 	return ret;
-
-backoff:
-	drm_atomic_state_clear(state);
-	drm_modeset_backoff(&ctx);
-
-	goto retry;
 }