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Commit d732580b authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

block: implement blk_queue_bypass_start/end() 



Rename and extend elv_queisce_start/end() to
blk_queue_bypass_start/end() which are exported and supports nesting
via @q->bypass_depth.  Also add blk_queue_bypass() to test bypass
state.

This will be further extended and used for blkio_group management.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent b2fab5ac

block/blk-core.c

+37 −2
Original line number Diff line number Diff line
@@ -409,6 +409,42 @@ void blk_drain_queue(struct request_queue *q, bool drain_all) 
	}

}



/**

 * blk_queue_bypass_start - enter queue bypass mode

 * @q: queue of interest

 *

 * In bypass mode, only the dispatch FIFO queue of @q is used.  This

 * function makes @q enter bypass mode and drains all requests which were

 * issued before.  On return, it's guaranteed that no request has ELVPRIV

 * set.

 */

void blk_queue_bypass_start(struct request_queue *q)

{

	spin_lock_irq(q->queue_lock);

	q->bypass_depth++;

	queue_flag_set(QUEUE_FLAG_BYPASS, q);

	spin_unlock_irq(q->queue_lock);



	blk_drain_queue(q, false);

}

EXPORT_SYMBOL_GPL(blk_queue_bypass_start);



/**

 * blk_queue_bypass_end - leave queue bypass mode

 * @q: queue of interest

 *

 * Leave bypass mode and restore the normal queueing behavior.

 */

void blk_queue_bypass_end(struct request_queue *q)

{

	spin_lock_irq(q->queue_lock);

	if (!--q->bypass_depth)

		queue_flag_clear(QUEUE_FLAG_BYPASS, q);

	WARN_ON_ONCE(q->bypass_depth < 0);

	spin_unlock_irq(q->queue_lock);

}

EXPORT_SYMBOL_GPL(blk_queue_bypass_end);



/**

 * blk_cleanup_queue - shutdown a request queue

 * @q: request queue to shutdown
@@ -862,8 +898,7 @@ static struct request *get_request(struct request_queue *q, int rw_flags, 
	 * Also, lookup icq while holding queue_lock.  If it doesn't exist,

	 * it will be created after releasing queue_lock.

	 */

	if (blk_rq_should_init_elevator(bio) &&

	    !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags)) {

	if (blk_rq_should_init_elevator(bio) && !blk_queue_bypass(q)) {

		rw_flags |= REQ_ELVPRIV;

		rl->elvpriv++;

		if (et->icq_cache && ioc)

block/blk.h

+2 −4
Original line number Diff line number Diff line
@@ -23,7 +23,8 @@ 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, bool drain_all);

void blk_queue_bypass_start(struct request_queue *q);

void blk_queue_bypass_end(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,
@@ -144,9 +145,6 @@ void blk_queue_congestion_threshold(struct request_queue *q); 


int blk_dev_init(void);



void elv_quiesce_start(struct request_queue *q);

void elv_quiesce_end(struct request_queue *q);





/*

 * Return the threshold (number of used requests) at which the queue is

block/elevator.c

+3 −22
Original line number Diff line number Diff line
@@ -553,25 +553,6 @@ void elv_drain_elevator(struct request_queue *q) 
	}

}



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);

	spin_unlock_irq(q->queue_lock);



	blk_drain_queue(q, false);

}



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)

{

	trace_block_rq_insert(q, rq);
@@ -903,7 +884,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) 
	 * using INSERT_BACK.  All requests have SOFTBARRIER set and no

	 * merge happens either.

	 */

	elv_quiesce_start(q);

	blk_queue_bypass_start(q);



	/* unregister and clear all auxiliary data of the old elevator */

	if (registered)
@@ -933,7 +914,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) 


	/* done, kill the old one and finish */

	elevator_exit(old);

	elv_quiesce_end(q);

	blk_queue_bypass_end(q);



	blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
@@ -945,7 +926,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) 
	/* switch failed, restore and re-register old elevator */

	q->elevator = old;

	elv_register_queue(q);

	elv_quiesce_end(q);

	blk_queue_bypass_end(q);



	return err;

}

include/linux/blkdev.h

+4 −1
Original line number Diff line number Diff line
@@ -389,6 +389,8 @@ struct request_queue { 


	struct mutex		sysfs_lock;



	int			bypass_depth;



#if defined(CONFIG_BLK_DEV_BSG)

	bsg_job_fn		*bsg_job_fn;

	int			bsg_job_size;
@@ -406,7 +408,7 @@ struct request_queue { 
#define	QUEUE_FLAG_SYNCFULL	3	/* read queue has been filled */

#define QUEUE_FLAG_ASYNCFULL	4	/* write queue has been filled */

#define QUEUE_FLAG_DEAD		5	/* queue being torn down */

#define QUEUE_FLAG_ELVSWITCH	6	/* don't use elevator, just do FIFO */

#define QUEUE_FLAG_BYPASS	6	/* act as dumb FIFO queue */

#define QUEUE_FLAG_BIDI		7	/* queue supports bidi requests */

#define QUEUE_FLAG_NOMERGES     8	/* disable merge attempts */

#define QUEUE_FLAG_SAME_COMP	9	/* complete on same CPU-group */
@@ -494,6 +496,7 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q) 
#define blk_queue_tagged(q)	test_bit(QUEUE_FLAG_QUEUED, &(q)->queue_flags)

#define blk_queue_stopped(q)	test_bit(QUEUE_FLAG_STOPPED, &(q)->queue_flags)

#define blk_queue_dead(q)	test_bit(QUEUE_FLAG_DEAD, &(q)->queue_flags)

#define blk_queue_bypass(q)	test_bit(QUEUE_FLAG_BYPASS, &(q)->queue_flags)

#define blk_queue_nomerges(q)	test_bit(QUEUE_FLAG_NOMERGES, &(q)->queue_flags)

#define blk_queue_noxmerges(q)	\

	test_bit(QUEUE_FLAG_NOXMERGES, &(q)->queue_flags)