+/**
+ * i915_gem_release_mmap - remove physical page mappings
+ * @obj: obj in question
+ *
+ * Preserve the reservation of the mmaping with the DRM core code, but
+ * relinquish ownership of the pages back to the system.
+ *
+ * It is vital that we remove the page mapping if we have mapped a tiled
+ * object through the GTT and then lose the fence register due to
+ * resource pressure. Similarly if the object has been moved out of the
+ * aperture, than pages mapped into userspace must be revoked. Removing the
+ * mapping will then trigger a page fault on the next user access, allowing
+ * fixup by i915_gem_fault().
+ */
+static void
+i915_gem_release_mmap(struct drm_gem_object *obj)
+{
+ struct drm_device *dev = obj->dev;
+ struct drm_i915_gem_object *obj_priv = obj->driver_private;
+
+ if (dev->dev_mapping)
+ unmap_mapping_range(dev->dev_mapping,
+ obj_priv->mmap_offset, obj->size, 1);
+}
+