[Virtio-fs] Adding notifications vq to the virtio-fs device

[Dr. David Alan Gilbert]

* Stefan Hajnoczi (stefanha at redhat.com) wrote:
> Hi Vivek,
> There is discussion of adding the notifications vq to the virtio-fs
> device so that FUSE Notification messages are possible.  This was
> previously discussed on the VIRTIO mailing lists here:
> https://lists.oasis-open.org/archives/virtio-dev/201902/msg00074.html
> 
> The main issue is how to handle the case where the device wishes to
> raise notifications but the driver has not supplied enough buffers.
> 
> FUSE requires reliable notification delivery.  We cannot drop
> notifications.
> 
> The mechanism will have to support reliable delivery.  For example, the
> device may need to pause further operation until the driver makes
> buffers available again.  But this could lead to DoS or deadlocks, so
> care is needed!
> 
> I hope this link is useful in restarting the discussion about the
> notifications vq.

In the case we were recently discussing, notification of lock
availability, that's not necessarily a problem; if there's no
space on the notification queue then we stop notifying about
locks until there is some space.

Dave

> Stefan


--
Dr. David Alan Gilbert / dgilbert at redhat.com / Manchester, UK