On Fri, Sep 09, 2016 at 04:54:44PM +0300, Denis V. Lunev wrote: > From: Konstantin Neumoin <[email protected]> > > At this moment oom notification in balloon does not work as expected. > After virtballoon_oom_notify there is an infinitive loop: > - virtballoon_oom_notify was called and balloon was deflated > - balloon get notification that config was changed, compare target and > actual and try to reach target again. > > This patch adds global variable fail_counter which indicates that oom has > been happened. We check that fail_counter was changed between calls > update_balloon_size_func. In this case we should not try to inflate balloon > even if actual != target.
Doesn't look right to me. What if it triggered an hour ago? We really need mm core to expose an oom_in_progress flag that we can test. More implementation comments below. > > Signed-off-by: Konstantin Neumoin <[email protected]> > Signed-off-by: Denis V. Lunev <[email protected]> > CC: Michael S. Tsirkin <[email protected]> > --- > drivers/virtio/virtio_balloon.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > index 4e7003d..253bf05 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -50,6 +50,8 @@ MODULE_PARM_DESC(oom_pages, "pages to free on OOM"); > static struct vfsmount *balloon_mnt; > #endif > > +static unsigned long fail_count; > + > struct virtio_balloon { > struct virtio_device *vdev; > struct virtqueue *inflate_vq, *deflate_vq, *stats_vq; > @@ -361,6 +363,8 @@ static int virtballoon_oom_notify(struct notifier_block > *self, > unsigned long *freed; > unsigned num_freed_pages; > > + fail_count++; > + > vb = container_of(self, struct virtio_balloon, nb); > if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) > return NOTIFY_OK; OOM should not interfere with ballooning unless VIRTIO_BALLOON_F_DEFLATE_ON_OOM has been negotiated. > @@ -386,11 +390,22 @@ static void update_balloon_size_func(struct work_struct > *work) > { > struct virtio_balloon *vb; > s64 diff; > + static unsigned long fc; > + > + if (fc == 0) > + fc = fail_count; Why? > > vb = container_of(work, struct virtio_balloon, > update_balloon_size_work); > diff = towards_target(vb); > > + if (fc != fail_count) { > + fc = fail_count; Unlikely to work correctly if there are multiple balloon devices. > + /* Don't inflate balloon after oom notification */ > + if (diff > 0) > + return; > + } > + > if (diff > 0) > diff -= fill_balloon(vb, diff); > else if (diff < 0) I'd rather make it per-device. Absence of memory ordering primitives of any kind also looks suspicious. > -- > 2.7.4
