[PATCH v2 2/4] virtio_balloon: factor out virtballoon_quiesce()

["Denis V. Lunev" <den@openvz.org>]

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);
-	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
+	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 		unregister_oom_notifier(&vb->oom_nb);
-	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
+	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 		virtio_balloon_unregister_shrinker(vb);
+
 	spin_lock_irq(&vb->stop_update_lock);
 	vb->stop_update = true;
 	spin_unlock_irq(&vb->stop_update_lock);
 	cancel_work_sync(&vb->update_balloon_size_work);
 	cancel_work_sync(&vb->update_balloon_stats_work);
 
-	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
+	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 		cancel_work_sync(&vb->report_free_page_work);
+}
+
+static void virtballoon_remove(struct virtio_device *vdev)
+{
+	struct virtio_balloon *vb = vdev->priv;
+
+	virtballoon_quiesce(vb);
+
+	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 		destroy_workqueue(vb->balloon_wq);
-	}
 
 	remove_common(vb);
 	mutex_destroy(&vb->balloon_lock);
-- 
2.53.0