dlm: add time stamp of blocking callback

Record the time the latest blocking callback was queued for
a lock.  This will be used for debugging in combination with
lock queue timestamp changes in the previous patch.
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/dlm_internal.h

@@ -245,6 +245,7 @@ struct dlm_lkb {
 	struct list_head	lkb_astqueue;	/* need ast to be sent */
 	struct list_head	lkb_ownqueue;	/* list of locks for a process */
 	struct list_head	lkb_time_list;
+	ktime_t			lkb_time_bast;	/* for debugging */
 	ktime_t			lkb_timestamp;
 	unsigned long		lkb_timeout_cs;
 

fs/dlm/lock.c

@@ -318,6 +318,8 @@ static inline void queue_cast_overlap(struct dlm_rsb *r, struct dlm_lkb *lkb)
 
 static void queue_bast(struct dlm_rsb *r, struct dlm_lkb *lkb, int rqmode)
 {
+	lkb->lkb_time_bast = ktime_get();
+
 	if (is_master_copy(lkb))
 		send_bast(r, lkb, rqmode);
 	else