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

[Jason Gunthorpe]

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?

@@ -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