[sheepdog] [PATCH] sheep: fix a crash caused by float point exception in recalculate_vnodes

[levin li]

From: levin li <xingke.lwp at taobao.com>

When sheep starts as a gateway-only node firstly in the cluster, there's
no non-gateway-only nodes and thus nr_non_gateway_nodes is zero, and it
casues to divide zero which causes gateway-only node crash

Signed-off-by: levin li <xingke.lwp at taobao.com>
---
 sheep/group.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sheep/group.c b/sheep/group.c
index 8ebb3e6..05ffb3e 100644
--- a/sheep/group.c
+++ b/sheep/group.c
@@ -797,6 +797,10 @@ void recalculate_vnodes(struct sd_node *nodes, int nr_nodes)
 			nr_non_gateway_nodes++;
 		}
 	}
+
+	if (!nr_non_gateway_nodes)
+		return;
+
 	avg_size /= nr_non_gateway_nodes;
 
 	for (i = 0; i < nr_nodes; i++) {
-- 
1.7.10