Re: [PATCH v3 10/17] iommufd: Reorganize iommufd_device_attach into iommufd_device_change_pt

On Thu, Mar 23, 2023 at 07:25:55AM +0000, Tian, Kevin wrote:

...

From: Jason Gunthorpe jgg@nvidia.com 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.

The WARN_ON is on the destroy path of the device

was_destroyed = iommufd_object_destroy_user(idev->ictx, &idev->obj); WARN_ON(!was_destroyed);

It is the idev we are incr'ing

Jason