block: elevator quiescing helpers

Simple helper functions to quiesce the request queue. These are currently only used for switching IO schedulers on-the-fly, but we can use them to properly switch IO accounting on and off as well. Signed-off-by: Jerome Marchand <jmarchan@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block: elevator quiescing helpers
Simple helper functions to quiesce the request queue. These are currently only used for switching IO schedulers on-the-fly, but we can use them to properly switch IO accounting on and off as well. Signed-off-by: Jerome Marchand <jmarchan@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Jens Axboe
1 parent d508afb437
Showing 2 changed files with 31 additions and 13 deletions Side-by-side Diff
block/blk.h
block/elevator.c
@@ -70,6 +70,10 @@
  
 int blk_dev_init(void);
  
+void elv_quisce_start(struct request_queue *q);
+void elv_quisce_end(struct request_queue *q);
+
+
 /*
  * Return the threshold (number of used requests) at which the queue is
  * considered to be congested.  It include a little hysteresis to keep the
@@ -587,6 +587,31 @@
 	}
 }
  
+/*
+ * Call with queue lock held, interrupts disabled
+ */
+void elv_quisce_start(struct request_queue *q)
+{
+	queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
+
+	/*
+	 * make sure we don't have any requests in flight
+	 */
+	elv_drain_elevator(q);
+	while (q->rq.elvpriv) {
+		blk_start_queueing(q);
+		spin_unlock_irq(q->queue_lock);
+		msleep(10);
+		spin_lock_irq(q->queue_lock);
+		elv_drain_elevator(q);
+	}
+}
+
+void elv_quisce_end(struct request_queue *q)
+{
+	queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
+}
+
 void elv_insert(struct request_queue *q, struct request *rq, int where)
 {
 	struct list_head *pos;
  
@@ -1101,19 +1126,8 @@
 	 * Turn on BYPASS and drain all requests w/ elevator private data
 	 */
 	spin_lock_irq(q->queue_lock);
+	elv_quisce_start(q);
  
-	queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
-
-	elv_drain_elevator(q);
-
-	while (q->rq.elvpriv) {
-		blk_start_queueing(q);
-		spin_unlock_irq(q->queue_lock);
-		msleep(10);
-		spin_lock_irq(q->queue_lock);
-		elv_drain_elevator(q);
-	}
-
 	/*
 	 * Remember old elevator.
 	 */
@@ -1136,7 +1150,7 @@
 	 */
 	elevator_exit(old_elevator);
 	spin_lock_irq(q->queue_lock);
-	queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
+	elv_quisce_end(q);
 	spin_unlock_irq(q->queue_lock);
  
 	blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name);
...	...	@@ -70,6 +70,10 @@
70	70
71	71	int blk_dev_init(void);
72	72
	73	+void elv_quisce_start(struct request_queue *q);
	74	+void elv_quisce_end(struct request_queue *q);
	75	+
	76	+
73	77	/*
74	78	* Return the threshold (number of used requests) at which the queue is
75	79	* considered to be congested. It include a little hysteresis to keep the
...	...	@@ -587,6 +587,31 @@
587	587	}
588	588	}
589	589
	590	+/*
	591	+ * Call with queue lock held, interrupts disabled
	592	+ */
	593	+void elv_quisce_start(struct request_queue *q)
	594	+{
	595	+ queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
	596	+
	597	+ /*
	598	+ * make sure we don't have any requests in flight
	599	+ */
	600	+ elv_drain_elevator(q);
	601	+ while (q->rq.elvpriv) {
	602	+ blk_start_queueing(q);
	603	+ spin_unlock_irq(q->queue_lock);
	604	+ msleep(10);
	605	+ spin_lock_irq(q->queue_lock);
	606	+ elv_drain_elevator(q);
	607	+ }
	608	+}
	609	+
	610	+void elv_quisce_end(struct request_queue *q)
	611	+{
	612	+ queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
	613	+}
	614	+
590	615	void elv_insert(struct request_queue q, struct request rq, int where)
591	616	{
592	617	struct list_head *pos;
593	618
...	...	@@ -1101,19 +1126,8 @@
1101	1126	* Turn on BYPASS and drain all requests w/ elevator private data
1102	1127	*/
1103	1128	spin_lock_irq(q->queue_lock);
	1129	+ elv_quisce_start(q);
1104	1130
1105		- queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
1106		-
1107		- elv_drain_elevator(q);
1108		-
1109		- while (q->rq.elvpriv) {
1110		- blk_start_queueing(q);
1111		- spin_unlock_irq(q->queue_lock);
1112		- msleep(10);
1113		- spin_lock_irq(q->queue_lock);
1114		- elv_drain_elevator(q);
1115		- }
1116		-
1117	1131	/*
1118	1132	* Remember old elevator.
1119	1133	*/
...	...	@@ -1136,7 +1150,7 @@
1136	1150	*/
1137	1151	elevator_exit(old_elevator);
1138	1152	spin_lock_irq(q->queue_lock);
1139		- queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
	1153	+ elv_quisce_end(q);
1140	1154	spin_unlock_irq(q->queue_lock);
1141	1155
1142	1156	blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name);