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> > > > > + > > > > > + mutex_lock(&idev->igroup->lock); > > > > > + if (idev->vdev) { > > > > > + struct iommufd_vdevice *vdev; > > > > > + > > > > > + vdev = iommufd_get_vdevice(idev->ictx, idev->vdev->obj.id); > > > > > + if (IS_ERR(vdev)) { > > > > > > > > This incrs obj.users which will cause a concurrent > > > > iommufd_object_remove() to fail with -EBUSY, which we are trying to > > > > avoid. > > > > > > concurrent remove means a user-initiated IOMMU_DESTROY, for which > > > failing with -EBUSY is expected as it doesn't wait for shortterm? > > > > Yes a user IOMMU_DESTROY of the vdevice should not have a transient > > EBUSY failure. Avoiding that is the purpose of the shorterm_users > > mechanism. > > hmm my understanding is the opposite. > > currently iommufd_destroy() doesn't set REMOVE_WAIT_SHORTTERM: Oh yes I got them mixed up. > waiting shorterm_users is more for kernel destroy. Yes, it is to make kernel destroy not fail > Then iommufd_device_remove_vdev() will wait on idev->vdev to > be NULL instead of calling iommufd_object_tombstone_user(). Ah, because the original version incrs users, not just shortterm_users. Jason