ocfs2: report error from o2hb_do_disk_heartbeat() to user

Report return value of o2hb_do_disk_heartbeat() as a part of ML_HEARTBEAT
message so that we know whether a heartbeat actually happened or not.
This also makes assigned but otherwise unused 'ret' variable used.

Coverity id: 1227053.
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ocfs2/cluster/heartbeat.c

@@ -1127,10 +1127,10 @@ static int o2hb_thread(void *data)
 		elapsed_msec = o2hb_elapsed_msecs(&before_hb, &after_hb);
 
 		mlog(ML_HEARTBEAT,
-		     "start = %lu.%lu, end = %lu.%lu, msec = %u\n",
+		     "start = %lu.%lu, end = %lu.%lu, msec = %u, ret = %d\n",
 		     before_hb.tv_sec, (unsigned long) before_hb.tv_usec,
 		     after_hb.tv_sec, (unsigned long) after_hb.tv_usec,
-		     elapsed_msec);
+		     elapsed_msec, ret);
 
 		if (!kthread_should_stop() &&
 		    elapsed_msec < reg->hr_timeout_ms) {