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Commit 75ad23bc authored by Nick Piggin's avatar Nick Piggin Committed by Jens Axboe
Browse files

block: make queue flags non-atomic 



We can save some atomic ops in the IO path, if we clearly define
the rules of how to modify the queue flags.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 68154e90

block/blk-core.c

+26 −13
Original line number Diff line number Diff line
@@ -198,7 +198,8 @@ void blk_plug_device(struct request_queue *q) 
	if (blk_queue_stopped(q))

		return;



	if (!test_and_set_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags)) {

	if (!test_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags)) {

		__set_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags);

		mod_timer(&q->unplug_timer, jiffies + q->unplug_delay);

		blk_add_trace_generic(q, NULL, 0, BLK_TA_PLUG);

	}
@@ -213,9 +214,10 @@ int blk_remove_plug(struct request_queue *q) 
{

	WARN_ON(!irqs_disabled());



	if (!test_and_clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags))

	if (!test_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags))

		return 0;



	queue_flag_clear(QUEUE_FLAG_PLUGGED, q);

	del_timer(&q->unplug_timer);

	return 1;

}
@@ -311,15 +313,16 @@ void blk_start_queue(struct request_queue *q) 
{

	WARN_ON(!irqs_disabled());



	clear_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);

	queue_flag_clear(QUEUE_FLAG_STOPPED, q);



	/*

	 * one level of recursion is ok and is much faster than kicking

	 * the unplug handling

	 */

	if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {

	if (!test_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {

		queue_flag_set(QUEUE_FLAG_REENTER, q);

		q->request_fn(q);

		clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);

		queue_flag_clear(QUEUE_FLAG_REENTER, q);

	} else {

		blk_plug_device(q);

		kblockd_schedule_work(&q->unplug_work);
@@ -344,7 +347,7 @@ EXPORT_SYMBOL(blk_start_queue); 
void blk_stop_queue(struct request_queue *q)

{

	blk_remove_plug(q);

	set_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);

	queue_flag_set(QUEUE_FLAG_STOPPED, q);

}

EXPORT_SYMBOL(blk_stop_queue);
@@ -373,11 +376,8 @@ EXPORT_SYMBOL(blk_sync_queue); 
 * blk_run_queue - run a single device queue

 * @q:	The queue to run

 */

void blk_run_queue(struct request_queue *q)

void __blk_run_queue(struct request_queue *q)

{

	unsigned long flags;



	spin_lock_irqsave(q->queue_lock, flags);

	blk_remove_plug(q);



	/*
@@ -385,15 +385,28 @@ void blk_run_queue(struct request_queue *q) 
	 * handling reinvoke the handler shortly if we already got there.

	 */

	if (!elv_queue_empty(q)) {

		if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {

		if (!test_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {

			queue_flag_set(QUEUE_FLAG_REENTER, q);

			q->request_fn(q);

			clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);

			queue_flag_clear(QUEUE_FLAG_REENTER, q);

		} else {

			blk_plug_device(q);

			kblockd_schedule_work(&q->unplug_work);

		}

	}

}

EXPORT_SYMBOL(__blk_run_queue);



/**

 * blk_run_queue - run a single device queue

 * @q: The queue to run

 */

void blk_run_queue(struct request_queue *q)

{

	unsigned long flags;



	spin_lock_irqsave(q->queue_lock, flags);

	__blk_run_queue(q);

	spin_unlock_irqrestore(q->queue_lock, flags);

}

EXPORT_SYMBOL(blk_run_queue);
@@ -406,7 +419,7 @@ void blk_put_queue(struct request_queue *q) 
void blk_cleanup_queue(struct request_queue *q)

{

	mutex_lock(&q->sysfs_lock);

	set_bit(QUEUE_FLAG_DEAD, &q->queue_flags);

	queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);

	mutex_unlock(&q->sysfs_lock);



	if (q->elevator)

block/blk-merge.c

+3 −3
Original line number Diff line number Diff line
@@ -55,7 +55,7 @@ void blk_recalc_rq_segments(struct request *rq) 
	if (!rq->bio)

		return;



	cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);

	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);

	hw_seg_size = seg_size = 0;

	phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;

	rq_for_each_segment(bv, rq, iter) {
@@ -128,7 +128,7 @@ EXPORT_SYMBOL(blk_recount_segments); 
static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,

				   struct bio *nxt)

{

	if (!(q->queue_flags & (1 << QUEUE_FLAG_CLUSTER)))

	if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))

		return 0;



	if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
@@ -175,7 +175,7 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq, 
	int nsegs, cluster;



	nsegs = 0;

	cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);

	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);



	/*

	 * for each bio in rq

block/blk-settings.c

+1 −1
Original line number Diff line number Diff line
@@ -287,7 +287,7 @@ void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b) 
	t->max_segment_size = min(t->max_segment_size, b->max_segment_size);

	t->hardsect_size = max(t->hardsect_size, b->hardsect_size);

	if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags))

		clear_bit(QUEUE_FLAG_CLUSTER, &t->queue_flags);

		queue_flag_clear(QUEUE_FLAG_CLUSTER, t);

}

EXPORT_SYMBOL(blk_queue_stack_limits);

block/blk-tag.c

+4 −4
Original line number Diff line number Diff line
@@ -70,7 +70,7 @@ void __blk_queue_free_tags(struct request_queue *q) 
	__blk_free_tags(bqt);



	q->queue_tags = NULL;

	q->queue_flags &= ~(1 << QUEUE_FLAG_QUEUED);

	queue_flag_clear(QUEUE_FLAG_QUEUED, q);

}



/**
@@ -98,7 +98,7 @@ EXPORT_SYMBOL(blk_free_tags); 
 **/

void blk_queue_free_tags(struct request_queue *q)

{

	clear_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);

	queue_flag_clear(QUEUE_FLAG_QUEUED, q);

}

EXPORT_SYMBOL(blk_queue_free_tags);
@@ -188,7 +188,7 @@ int blk_queue_init_tags(struct request_queue *q, int depth, 
		rc = blk_queue_resize_tags(q, depth);

		if (rc)

			return rc;

		set_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);

		queue_flag_set(QUEUE_FLAG_QUEUED, q);

		return 0;

	} else

		atomic_inc(&tags->refcnt);
@@ -197,7 +197,7 @@ int blk_queue_init_tags(struct request_queue *q, int depth, 
	 * assign it, all done

	 */

	q->queue_tags = tags;

	q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);

	queue_flag_set(QUEUE_FLAG_QUEUED, q);

	INIT_LIST_HEAD(&q->tag_busy_list);

	return 0;

fail:

block/elevator.c

+10 −3
Original line number Diff line number Diff line
@@ -1070,7 +1070,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) 
	 */

	spin_lock_irq(q->queue_lock);



	set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);

	queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);



	elv_drain_elevator(q);
@@ -1104,7 +1104,10 @@ 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);

	clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);

	spin_lock_irq(q->queue_lock);

	queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);

	spin_unlock_irq(q->queue_lock);



	return 1;



fail_register:
@@ -1115,7 +1118,11 @@ fail_register: 
	elevator_exit(e);

	q->elevator = old_elevator;

	elv_register_queue(q);

	clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);



	spin_lock_irq(q->queue_lock);

	queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);

	spin_unlock_irq(q->queue_lock);



	return 0;

}