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virtio_balloon: quiesce balloon work before device shutdown

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Commit 8bd2fa086a ("virtio: break and reset virtio devices on
device_shutdown()") added a generic virtio bus .shutdown handler that
breaks and resets every virtio device during device_shutdown(), i.e. on
reboot and kexec.

virtio_balloon provides no .shutdown of its own, so that generic path
runs while the balloon's asynchronous work is still armed. Once the
device has been broken, virtqueue_add_inbuf() in
virtballoon_free_page_report() returns -EIO and trips its
WARN_ON_ONCE(). On a kernel booted with panic_on_warn that turns an
ordinary reboot, for example a kexec based upgrade, into a fatal panic
in the middle of device_shutdown(), so the machine never reaches the
new kernel.

Relaxing that single WARN_ON_ONCE() would only hide the symptom: the
inflate/deflate and OOM paths do not warn, they call
wait_event(vb->acked, ...) and would instead block forever on a broken
queue that can no longer complete. The device has to be quiesced, not
just kept quiet.

Add a .shutdown handler that quiesces the balloon via the shared
virtballoon_quiesce() helper while the device is still alive, and only
then breaks and resets it via virtio_device_shutdown(). Unlike
virtballoon_remove() the balloon workqueue is not destroyed, as shutdown
does not free the device and cancel_work_sync() together with stop_update
already prevent any further work from being queued.

Fixes: 8bd2fa086a ("virtio: break and reset virtio devices on device_shutdown()")
Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20260624140846.2616797-4-den@openvz.org>
This commit is contained in:
Denis V. Lunev
2026-06-24 16:08:45 +02:00
committed by Michael S. Tsirkin
parent 29536a923a
commit 7e17eef046
1 changed files with 7 additions and 0 deletions
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7
drivers/virtio/virtio_balloon.c
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@@ -1135,6 +1135,12 @@ static void virtballoon_remove(struct virtio_device *vdev)
kfree(vb);
}
static void virtballoon_shutdown(struct virtio_device *vdev)
{
virtballoon_quiesce(vdev->priv);
virtio_device_shutdown(vdev);
}
#ifdef CONFIG_PM_SLEEP
static int virtballoon_freeze(struct virtio_device *vdev)
{
@@ -1205,6 +1211,7 @@ static struct virtio_driver virtio_balloon_driver = {
.validate = virtballoon_validate,
.probe = virtballoon_probe,
.remove = virtballoon_remove,
.shutdown = virtballoon_shutdown,
.config_changed = virtballoon_changed,
#ifdef CONFIG_PM_SLEEP
.freeze = virtballoon_freeze,