virtio_net: do not reschedule rx refill forever

We currently fill all of RX ring, then add_buf
returns ENOSPC, which gets mis-detected as an out of
memory condition and causes us to reschedule the work,
and so on forever. Fix this by oom = err == -ENOMEM;
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: stable@kernel.org # .34.x
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/virtio_net.c

@@ -415,7 +415,7 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi, gfp_t gfp)
 static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp)
 {
 	int err;
-	bool oom = false;
+	bool oom;
 
 	do {
 		if (vi->mergeable_rx_bufs)
@@ -425,10 +425,9 @@ static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp)
 		else
 			err = add_recvbuf_small(vi, gfp);
 
-		if (err < 0) {
-			oom = true;
+		oom = err == -ENOMEM;
+		if (err < 0)
 			break;
-		}
 		++vi->num;
 	} while (err > 0);
 	if (unlikely(vi->num > vi->max))