> From: Jason Gunthorpe <jgg@xxxxxxxxxx> > Sent: Wednesday, March 22, 2023 3:15 AM > +int iommufd_device_attach(struct iommufd_device *idev, u32 *pt_id) > +{ > + int rc; > + > + rc = iommufd_device_change_pt(idev, pt_id, > &iommufd_device_do_attach); > + if (rc) > + return rc; > + > + /* > + * Pairs with iommufd_device_detach() - catches caller bugs > attempting > + * to destroy a device with an attachment. > + */ > + refcount_inc(&idev->obj.users); > + return 0; While it's the right thing to do I'm not sure what "catch caller bugs" mean here. There is no WARN_ON to catch. Otherwise it's good. Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>