ocfs2: fix race between mount and delete node/cluster

There is a race case between mount and delete node/cluster, which will
lead o2hb_thread to malfunctioning dead loop.

    o2hb_thread
    {
        o2nm_depend_this_node();
        <<<<<< race window, node may have already been deleted, and then
               enter the loop, o2hb thread will be malfunctioning
               because of no configured nodes found.
        while (!kthread_should_stop() &&
               !reg->hr_unclean_stop && !reg->hr_aborted_start) {
    }

So check the return value of o2nm_depend_this_node() is needed.  If node
has been deleted, do not enter the loop and let mount fail.
Signed-off-by: NJoseph Qi <joseph.qi@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/ocfs2/cluster/heartbeat.c

@@ -219,7 +219,8 @@ struct o2hb_region {
 	unsigned		hr_unclean_stop:1,
 				hr_aborted_start:1,
 				hr_item_pinned:1,
-				hr_item_dropped:1;
+				hr_item_dropped:1,
+				hr_node_deleted:1;
 
 	/* protected by the hr_callback_sem */
 	struct task_struct 	*hr_task;
@@ -1078,7 +1079,13 @@ static int o2hb_thread(void *data)
 	set_user_nice(current, MIN_NICE);
 
 	/* Pin node */
-	o2nm_depend_this_node();
+	ret = o2nm_depend_this_node();
+	if (ret) {
+		mlog(ML_ERROR, "Node has been deleted, ret = %d\n", ret);
+		reg->hr_node_deleted = 1;
+		wake_up(&o2hb_steady_queue);
+		return 0;
+	}
 
 	while (!kthread_should_stop() &&
 	       !reg->hr_unclean_stop && !reg->hr_aborted_start) {
@@ -1787,7 +1794,8 @@ static ssize_t o2hb_region_dev_write(struct o2hb_region *reg,
 	spin_unlock(&o2hb_live_lock);
 
 	ret = wait_event_interruptible(o2hb_steady_queue,
-				atomic_read(&reg->hr_steady_iterations) == 0);
+				atomic_read(&reg->hr_steady_iterations) == 0 ||
+				reg->hr_node_deleted);
 	if (ret) {
 		atomic_set(&reg->hr_steady_iterations, 0);
 		reg->hr_aborted_start = 1;
@@ -1798,6 +1806,11 @@ static ssize_t o2hb_region_dev_write(struct o2hb_region *reg,
 		goto out3;
 	}
 
+	if (reg->hr_node_deleted) {
+		ret = -EINVAL;
+		goto out3;
+	}
+
 	/* Ok, we were woken.  Make sure it wasn't by drop_item() */
 	spin_lock(&o2hb_live_lock);
 	hb_task = reg->hr_task;