Re: [PATCH 1/2] virtio_balloon: factor out virtballoon_quiesce()

["David Hildenbrand (Arm)" <david@kernel.org>]

On 6/22/26 15:37, Denis V. Lunev wrote:
> virtballoon_remove() stops all of the balloon's asynchronous work (the
> free page reporting worker, the inflate/deflate and stats workers, the
> OOM notifier and the free page shrinker) before tearing the device
> down. A following change needs the same teardown from a .shutdown
> handler, so move it into a virtballoon_quiesce() helper.
> 
> No functional change.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> ---
>  drivers/virtio/virtio_balloon.c | 27 ++++++++++++++++++++-------
>  1 file changed, 20 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 088b3a0e6ce6..5b02d9191ac6 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -1098,26 +1098,39 @@ static void remove_common(struct virtio_balloon *vb)
>  	vb->vdev->config->del_vqs(vb->vdev);
>  }
>  
> -static void virtballoon_remove(struct virtio_device *vdev)
> +/*
> + * Stop all asynchronous balloon work. The device must still be alive so that
> + * in-flight requests can drain via the host before it is reset or freed.
> + */
> +static void virtballoon_quiesce(struct virtio_balloon *vb)
>  {
> -	struct virtio_balloon *vb = vdev->priv;
> +	struct virtio_device *vdev = vb->vdev;
>  
> -	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
> +	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_REPORTING))
>  		page_reporting_unregister(&vb->pr_dev_info);

Most functions here grab mutexes and can sleep. I assume that's fine in shutdown
context.

Nothing jumped at me


Sashiko asks whether ->remove (hotunplug/driver-unloading) can follow a
->shutdown callback. I don't know, seems questionable if this could happen and
should probably be handled by the core?

If it's possible you'd have to remember that stuff was already quiesce'ed. Maybe
simply by checking early in virtballoon_quiesce() whether vb->stop_update ==
true already.

-- 
Cheers,

David