Commit e3c78ca5 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

block: reorganize queue draining 



Reorganize queue draining related code in preparation of queue exit
changes.

* Factor out actual draining from elv_quiesce_start() to
  blk_drain_queue().

* Make elv_quiesce_start/end() responsible for their own locking.

* Replace open-coded ELVSWITCH clearing in elevator_switch() with
  elv_quiesce_end().

This patch doesn't cause any visible functional difference.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 315fceee

block/blk-core.c

+28 −0
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
#include <linux/task_io_accounting_ops.h>

#include <linux/fault-inject.h>

#include <linux/list_sort.h>

#include <linux/delay.h>



#define CREATE_TRACE_POINTS

#include <trace/events/block.h>
@@ -345,6 +346,33 @@ void blk_put_queue(struct request_queue *q) 
}

EXPORT_SYMBOL(blk_put_queue);



/**

 * blk_drain_queue - drain requests from request_queue

 * @q: queue to drain

 *

 * Drain ELV_PRIV requests from @q.  The caller is responsible for ensuring

 * that no new requests which need to be drained are queued.

 */

void blk_drain_queue(struct request_queue *q)

{

	while (true) {

		int nr_rqs;



		spin_lock_irq(q->queue_lock);



		elv_drain_elevator(q);



		__blk_run_queue(q);

		nr_rqs = q->rq.elvpriv;



		spin_unlock_irq(q->queue_lock);



		if (!nr_rqs)

			break;

		msleep(10);

	}

}



/*

 * Note: If a driver supplied the queue lock, it is disconnected

 * by this function. The actual state of the lock doesn't matter

block/blk.h

+1 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ void blk_rq_bio_prep(struct request_queue *q, struct request *rq, 
			struct bio *bio);

int blk_rq_append_bio(struct request_queue *q, struct request *rq,

		      struct bio *bio);

void blk_drain_queue(struct request_queue *q);

void blk_dequeue_request(struct request *rq);

void __blk_queue_free_tags(struct request_queue *q);

bool __blk_end_bidi_request(struct request *rq, int error,

block/elevator.c

+11 −26
Original line number Diff line number Diff line
@@ -31,7 +31,6 @@ 
#include <linux/slab.h>

#include <linux/init.h>

#include <linux/compiler.h>

#include <linux/delay.h>

#include <linux/blktrace_api.h>

#include <linux/hash.h>

#include <linux/uaccess.h>
@@ -606,43 +605,35 @@ void elv_requeue_request(struct request_queue *q, struct request *rq) 
void elv_drain_elevator(struct request_queue *q)

{

	static int printed;



	lockdep_assert_held(q->queue_lock);



	while (q->elevator->ops->elevator_dispatch_fn(q, 1))

		;

	if (q->nr_sorted == 0)

		return;

	if (printed++ < 10) {

	if (q->nr_sorted && printed++ < 10) {

		printk(KERN_ERR "%s: forced dispatching is broken "

		       "(nr_sorted=%u), please report this\n",

		       q->elevator->elevator_type->elevator_name, q->nr_sorted);

	}

}



/*

 * Call with queue lock held, interrupts disabled

 */

void elv_quiesce_start(struct request_queue *q)

{

	if (!q->elevator)

		return;



	spin_lock_irq(q->queue_lock);

	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_run_queue(q);

	spin_unlock_irq(q->queue_lock);

		msleep(10);

		spin_lock_irq(q->queue_lock);

		elv_drain_elevator(q);

	}



	blk_drain_queue(q);

}



void elv_quiesce_end(struct request_queue *q)

{

	spin_lock_irq(q->queue_lock);

	queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);

	spin_unlock_irq(q->queue_lock);

}



void __elv_add_request(struct request_queue *q, struct request *rq, int where)
@@ -972,7 +963,6 @@ 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);

	elv_quiesce_start(q);



	/*
@@ -983,8 +973,8 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) 
	/*

	 * attach and start new elevator

	 */

	spin_lock_irq(q->queue_lock);

	elevator_attach(q, e, data);



	spin_unlock_irq(q->queue_lock);



	if (old_elevator->registered) {
@@ -999,9 +989,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) 
	 * finally exit old elevator and turn off BYPASS.

	 */

	elevator_exit(old_elevator);

	spin_lock_irq(q->queue_lock);

	elv_quiesce_end(q);

	spin_unlock_irq(q->queue_lock);



	blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name);
@@ -1015,10 +1003,7 @@ fail_register: 
	elevator_exit(e);

	q->elevator = old_elevator;

	elv_register_queue(q);



	spin_lock_irq(q->queue_lock);

	queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);

	spin_unlock_irq(q->queue_lock);

	elv_quiesce_end(q);



	return err;

}

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