md-cluster: init suspend_list and suspend_lock early in join

If the node just join the cluster, and receive the msg from other nodes
before init suspend_list, it will cause kernel crash due to NULL pointer
dereference, so move the initializations early to fix the bug.

md-cluster: Joined cluster 3578507b-e0cb-6d4f-6322-696cd7b1b10c slot 3
BUG: unable to handle kernel NULL pointer dereference at           (null)
... ... ...
Call Trace:
[<ffffffffa0444924>] process_recvd_msg+0x2e4/0x330 [md_cluster]
[<ffffffffa0444a06>] recv_daemon+0x96/0x170 [md_cluster]
[<ffffffffa045189d>] md_thread+0x11d/0x170 [md_mod]
[<ffffffff810768c4>] kthread+0xb4/0xc0
[<ffffffff8151927c>] ret_from_fork+0x7c/0xb0
... ... ...
RIP  [<ffffffffa0443581>] __remove_suspend_info+0x11/0xa0 [md_cluster]

Reviewed-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: NeilBrown <neilb@suse.com>

drivers/md/md-cluster.c

@@ -671,6 +671,8 @@ static int join(struct mddev *mddev, int nodes)
 	if (!cinfo)
 		return -ENOMEM;
 
+	INIT_LIST_HEAD(&cinfo->suspend_list);
+	spin_lock_init(&cinfo->suspend_lock);
 	init_completion(&cinfo->completion);
 
 	mutex_init(&cinfo->sb_mutex);
@@ -736,9 +738,6 @@ static int join(struct mddev *mddev, int nodes)
 		goto err;
 	}
 
-	INIT_LIST_HEAD(&cinfo->suspend_list);
-	spin_lock_init(&cinfo->suspend_lock);
-
 	ret = gather_all_resync_info(mddev, nodes);
 	if (ret)
 		goto err;