Re: [PATCH v2 7/7] vfio: Remove calls to vfio_group_add_container_user()

Jason Gunthorpe
2022-04-22T22:06:37Z

On Fri, Apr 22, 2022 at 02:11:27AM +0000, Tian, Kevin wrote:

> > mutex_lock(&device->dev_set->lock);
> > - if (!--device->open_count && device->ops->close_device)
> > + vfio_assert_device_open(device);
> > + if (device->open_count == 1 && device->ops->close_device)
> > device->ops->close_device(device);
> > + device->open_count--;
> > mutex_unlock(&device->dev_set->lock);
>
> Is it necessary to add assertion here? This is the only place to
> decrement the counter and no similar assertion in other release()/
> put() functions.

Necessary, no, but since we have it we may as well check it here. It
is common to check that refcounts don't underflow.

Jason