[PATCH net-next] virtio_net: exploit napi_complete_done() return value

[Eric Dumazet]

From: Eric Dumazet <eduma...@google.com>

Since commit 364b6055738b ("net: busy-poll: return busypolling status to
drivers"), napi_complete_done() returns a boolean that can be used
by drivers to conditionally rearm interrupts.

This patch changes virtio_net to use this boolean to avoid a bit of
overhead for busy-poll users.

Jason reports about 1.1% improvement for 1 byte TCP_RR (burst 100).

Signed-off-by: Eric Dumazet <eduma...@google.com>
Acked-by: Jason Wang <jasow...@redhat.com>
Cc: Michael S. Tsirkin <m...@redhat.com>
Cc: Willem de Bruijn <will...@google.com>
---
 drivers/net/virtio_net.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 
0382827829d90b1d25d059609bae6d1c5ad2b6d9..29982c7f6080ae99f4753052dc80ff5310f1134b
 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1012,11 +1012,12 @@ static int virtnet_poll(struct napi_struct *napi, int 
budget)
        /* Out of packets? */
        if (received < budget) {
                r = virtqueue_enable_cb_prepare(rq->vq);
-               napi_complete_done(napi, received);
-               if (unlikely(virtqueue_poll(rq->vq, r)) &&
-                   napi_schedule_prep(napi)) {
-                       virtqueue_disable_cb(rq->vq);
-                       __napi_schedule(napi);
+               if (napi_complete_done(napi, received)) {
+                       if (unlikely(virtqueue_poll(rq->vq, r)) &&
+                           napi_schedule_prep(napi)) {
+                               virtqueue_disable_cb(rq->vq);
+                               __napi_schedule(napi);
+                       }
                }
        }