Re: [PATCH v2 09/15] xen/gntdev: use mmu_range_notifier_insert

[Boris Ostrovsky <boris.ostrovsky@oracle.com>]

On 11/7/19 3:36 PM, Jason Gunthorpe wrote:
> On Tue, Nov 05, 2019 at 10:16:46AM -0500, Boris Ostrovsky wrote:
>
>>> So, I suppose it can be relaxed to a null test and a WARN_ON that it
>>> hasn't changed?
>> You mean
>>
>> if (use_ptemod) {
>>         WARN_ON(map->vma != vma);
>>         ...
>>
>>
>> Yes, that sounds good.
> I amended my copy of the patch with the above, has this rework shown
> signs of working?

Yes, it works fine.

But please don't forget notifier ops initialization.

With those two changes,

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

>
> @@ -436,7 +436,8 @@ static void gntdev_vma_close(struct vm_area_struct *vma)
>         struct gntdev_priv *priv = file->private_data;
>  
>         pr_debug("gntdev_vma_close %p\n", vma);
> -       if (use_ptemod && map->vma == vma) {
> +       if (use_ptemod) {
> +               WARN_ON(map->vma != vma);
>                 mmu_range_notifier_remove(&map->notifier);
>                 map->vma = NULL;
>         }
>
> Jason