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

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

On 10/28/19 4:10 PM, Jason Gunthorpe wrote:
> @@ -445,17 +438,9 @@ 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) {
> -		/* It is possible that an mmu notifier could be running
> -		 * concurrently, so take priv->lock to ensure that the vma won't
> -		 * vanishing during the unmap_grant_pages call, since we will
> -		 * spin here until that completes. Such a concurrent call will
> -		 * not do any unmapping, since that has been done prior to
> -		 * closing the vma, but it may still iterate the unmap_ops list.
> -		 */
> -		mutex_lock(&priv->lock);
> +	if (use_ptemod && map->vma == vma) {


Is it possible for map->vma not to be equal to vma?

-boris


> +		mmu_range_notifier_remove(&map->notifier);
>  		map->vma = NULL;
> -		mutex_unlock(&priv->lock);
>  	}
>  	vma->vm_private_data = NULL;
>  	gntdev_put_map(priv, map);
>