> From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> Sent: Tuesday, April 16, 2024 5:25 PM
>
> On 2024/4/16 17:01, Tian, Kevin wrote:
> >> From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> >> Sent: Friday, April 12, 2024 4:21 PM
> >>
> >> +
> >> + rc = ida_get_lowest(&vdev->pasids, pasid, pasid);
> >> + if (rc == pasid)
> >> + return iommufd_device_pasid_replace(vdev-
> >>> iommufd_device,
> >> + pasid, pt_id);
> >> +
> >> + rc = iommufd_device_pasid_attach(vdev->iommufd_device, pasid,
> >> pt_id);
> >> + if (rc)
> >> + return rc;
> >> +
> >> + rc = ida_alloc_range(&vdev->pasids, pasid, pasid, GFP_KERNEL);
> >> + if (rc < 0) {
> >> + iommufd_device_pasid_detach(vdev->iommufd_device,
> >> pasid);
> >> + return rc;
> >> + }
> >
> > I'd do simple operation (ida_alloc_range()) first before doing attach.
> >
>
> But that means we rely on the ida_alloc_range() to return -ENOSPC to
> indicate the pasid is allocated, hence this attach is actually a
> replacement. This is easy to be broken if ida_alloc_range() returns
> -ENOSPC for other reasons in future.
>
ida_alloc_range() could fail for other reasons e.g. -ENOMEM.
in case I didn't make it clear I just meant to swap the order
between iommufd_device_pasid_attach() and ida_alloc_range().
replacement is still checked against ida_get_lowest().
