Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 6c7e8cee authored by Jens Axboe's avatar Jens Axboe
Browse files

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: default avatarJerome Marchand <jmarchan@redhat.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent d508afb4

block/blk.h

+4 −0
Original line number Diff line number Diff line
@@ -70,6 +70,10 @@ void blk_queue_congestion_threshold(struct request_queue *q); 


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

block/elevator.c

+27 −13
Original line number Diff line number Diff line
@@ -587,6 +587,31 @@ static void elv_drain_elevator(struct request_queue *q) 
	}

}



/*

 * 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;
@@ -1101,18 +1126,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) 
	 * Turn on BYPASS and drain all requests w/ elevator private data

	 */

	spin_lock_irq(q->queue_lock);



	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);

	}

	elv_quisce_start(q);



	/*

	 * Remember old elevator.
@@ -1136,7 +1150,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) 
	 */

	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);