[sheepdog] [PATCH 2/2] corosync: detect network partition based on left_list_entries

[Hitoshi Mitake]

Corosync passes a number of leaving node with the parameter
left_list_entries of confchg callback. It can be used for detecting
network partition.

Cc: Masahiro Tsuji <tuji at atworks.co.jp>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi at lab.ntt.co.jp>
---
 sheep/cluster/corosync.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/sheep/cluster/corosync.c b/sheep/cluster/corosync.c
index 477e442..f876112 100644
--- a/sheep/cluster/corosync.c
+++ b/sheep/cluster/corosync.c
@@ -17,6 +17,7 @@
 #include "cluster.h"
 #include "event.h"
 #include "work.h"
+#include "sheep_priv.h"
 
 #define CPG_INIT_RETRY_CNT 10
 #define COROSYNC_MAX_NODES 1024
@@ -530,6 +531,7 @@ static void cdrv_cpg_confchg(cpg_handle_t handle,
 	struct cpg_node joined_sheep[COROSYNC_MAX_NODES];
 	struct cpg_node left_sheep[COROSYNC_MAX_NODES];
 	bool promote = true;
+	struct vnode_info *vinfo;
 
 	sd_debug("mem:%zu, joined:%zu, left:%zu", member_list_entries,
 		 joined_list_entries, left_list_entries);
@@ -539,6 +541,17 @@ static void cdrv_cpg_confchg(cpg_handle_t handle,
 	build_cpg_node_list(left_sheep, left_list, left_list_entries);
 	build_cpg_node_list(joined_sheep, joined_list, joined_list_entries);
 
+	vinfo = get_vnode_info();
+	if (vinfo) {
+		/* !vinfo is true during joining */
+		if (vinfo->nr_nodes / 2 + 1 <= left_list_entries)
+			panic("a number of leaving node (%zu) is larger than"
+			      " majority (%d), network partition",
+			      left_list_entries, vinfo->nr_nodes / 2 + 1);
+		else
+			put_vnode_info(vinfo);
+	}
+
 	/* dispatch leave_handler */
 	for (i = 0; i < left_list_entries; i++) {
 		cevent = find_event(COROSYNC_EVENT_TYPE_JOIN, left_sheep + i);
-- 
1.8.3.2