virtio: clarify NO_NOTIFY flag usage

The other side (host) can set the NO_NOTIFY flag as an optimization,
to say "no need to kick me when you add things".  Make it clear that
this is advisory only; especially that we should always notify when
the ring is full.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 342bb0363fbe..dbe1d35db32a 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -87,6 +87,8 @@ static int vring_add_buf(struct virtqueue *_vq,
         if (vq->num_free < out + in) {
                 pr_debug("Can't add buf len %i - avail = %i\n",
                          out + in, vq->num_free);
+                /* We notify *even if* VRING_USED_F_NO_NOTIFY is set here. */
+                vq->notify(&vq->vq);
                 END_USE(vq);
                 return -ENOSPC;
         }