Re: [PATCH v2] virtio-balloon: Switch back to OOM handler for VIRTIO_BALLOON_F_DEFLATE_ON_OOM

Michael S. Tsirkin
2020-03-10T11:19:27Z

On Tue, Mar 10, 2020 at 12:12:50PM +0100, David Hildenbrand wrote:
> >> static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
> >> @@ -971,7 +950,22 @@ static int virtballoon_probe(struct virtio_device *vdev)
> >> VIRTIO_BALLOON_CMD_ID_STOP);
> >> spin_lock_init(&vb->free_page_list_lock);
> >> INIT_LIST_HEAD(&vb->free_page_list);
> >> + /*
> >> + * We're allowed to reuse any free pages, even if they are
> >> + * still to be processed by the host.
> >> + */
> >> + err = virtio_balloon_register_shrinker(vb);
> >> + if (err)
> >> + goto out_del_balloon_wq;
> >> }
> >> + if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
> >> + vb->oom_nb.notifier_call = virtio_balloon_oom_notify;
> >> + vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY;
> >> + err = register_oom_notifier(&vb->oom_nb);
> >> + if (err < 0)
> >> + goto out_unregister_shrinker;
> >> + }
> >> +
> >
> >
> > Let's decide whether we want an empty line after }, or not, and stick to
> > it. I prefer an empty line but no biggie as long as we are consistent.
>
> Can add one.
>
> >
> >> if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
> >> /* Start with poison val of 0 representing general init */
> >> __u32 poison_val = 0;
> >> @@ -986,15 +980,6 @@ static int virtballoon_probe(struct virtio_device *vdev)
> >> virtio_cwrite(vb->vdev, struct virtio_balloon_config,
> >> poison_val, &poison_val);
> >> }
> >> - /*
> >> - * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a
> >> - * shrinker needs to be registered to relieve memory pressure.
> >> - */
> >> - if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
> >> - err = virtio_balloon_register_shrinker(vb);
> >> - if (err)
> >> - goto out_del_balloon_wq;
> >> - }
> >>
> >> vb->pr_dev_info.report = virtballoon_free_page_report;
> >> if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
> >> @@ -1003,12 +988,12 @@ static int virtballoon_probe(struct virtio_device *vdev)
> >> capacity = virtqueue_get_vring_size(vb->reporting_vq);
> >> if (capacity < PAGE_REPORTING_CAPACITY) {
> >> err = -ENOSPC;
> >> - goto out_unregister_shrinker;
> >> + goto out_unregister_oom;
> >> }
> >>
> >> err = page_reporting_register(&vb->pr_dev_info);
> >> if (err)
> >> - goto out_unregister_shrinker;
> >> + goto out_unregister_oom;
> >> }
> >>
> >> virtio_device_ready(vdev);
> >> @@ -1017,8 +1002,11 @@ static int virtballoon_probe(struct virtio_device *vdev)
> >> virtballoon_changed(vdev);
> >> return 0;
> >>
> >> +out_unregister_oom:
> >> + if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
> >> + unregister_oom_notifier(&vb->oom_nb);
> >> out_unregister_shrinker:
> >> - if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
> >> + if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
> >> virtio_balloon_unregister_shrinker(vb);
> >
> >
> > What's with vdev versus vb->vdev here?
> > I suggest we keep using vb->vdev to make the patch minimal if we can.
> > Same elsewhere.
>
> As we touch this line either way, does it really make a difference? No
> strong opinion. Can just do a vb->vdev and clean this up globally later.
>

Let's just be consistent. I guess that means keep using vb->vdev
everywhere.

> --
> Thanks,
>
> David / dhildenb