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

David Hildenbrand
2020-03-10T11:13:05Z

>> 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.

--
Thanks,

David / dhildenb