gve: Track RX buffer allocation failures

The rx_buf_alloc_fail counter wasn't getting updated.

Fixes: 433e274b

 ("gve: Add stats for gve.")
Signed-off-by: Catherine Sullivan <csully@google.com>
Signed-off-by: Jeroen de Borst <jeroendb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/google/gve/gve_rx.c

@@ -532,8 +532,13 @@ static bool gve_rx_refill_buffers(struct gve_priv *priv, struct gve_rx_ring *rx)
 
 				gve_rx_free_buffer(dev, page_info, data_slot);
 				page_info->page = NULL;
-				if (gve_rx_alloc_buffer(priv, dev, page_info, data_slot))
+				if (gve_rx_alloc_buffer(priv, dev, page_info,
+							data_slot)) {
+					u64_stats_update_begin(&rx->statss);
+					rx->rx_buf_alloc_fail++;
+					u64_stats_update_end(&rx->statss);
 					break;
+				}
 			}
 		}
 		fill_cnt++;