> From: Jason Gunthorpe <jgg@xxxxxxxxxx> > Sent: Friday, April 22, 2022 12:29 AM > > When the open_device() op is called the container_users is incremented and > held incremented until close_device(). Thus, so long as drivers call > functions within their open_device()/close_device() region they do not > need to worry about the container_users. > > These functions can all only be called between open_device() and > close_device(): > > vfio_pin_pages() > vfio_unpin_pages() > vfio_dma_rw() > vfio_register_notifier() > vfio_unregister_notifier() > > Eliminate the calls to vfio_group_add_container_user() and add > vfio_assert_device_open() to detect driver mis-use. > > Reviewed-by: Christoph Hellwig <hch@xxxxxx> > Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>, with one nit > @@ -1544,8 +1550,10 @@ static int vfio_device_fops_release(struct inode > *inode, struct file *filep) > struct vfio_device *device = filep->private_data; > > 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. Thanks Kevin
