From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 14 Jun 2019 18:24:15 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20190614172414.GJ2785@work-vm> References: <20190610160955.GA19995@stefanha-x1.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190610160955.GA19995@stefanha-x1.localdomain> Subject: Re: [Virtio-fs] Adding notifications vq to the virtio-fs device List-Id: Development discussions about virtio-fs List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: virtio-fs@redhat.com, vgoyal@redhat.com * Stefan Hajnoczi (stefanha@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@redhat.com / Manchester, UK