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Commit 0a7ae2ff authored by Jens Axboe's avatar Jens Axboe
Browse files

block: change the tag sync vs async restriction logic 



Make them fully share the tag space, but disallow async requests using
the last any two slots.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent ac36552a

block/blk-barrier.c

+1 −1
Original line number Diff line number Diff line
@@ -218,7 +218,7 @@ static inline bool start_ordered(struct request_queue *q, struct request **rqp) 
	} else

		skip |= QUEUE_ORDSEQ_PREFLUSH;



	if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && q->in_flight)

	if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && queue_in_flight(q))

		rq = NULL;

	else

		skip |= QUEUE_ORDSEQ_DRAIN;

block/blk-core.c

+1 −1
Original line number Diff line number Diff line
@@ -1815,7 +1815,7 @@ void blk_dequeue_request(struct request *rq) 
	 * the driver side.

	 */

	if (blk_account_rq(rq))

		q->in_flight++;

		q->in_flight[rq_is_sync(rq)]++;

}



/**

block/blk-tag.c

+9 −6
Original line number Diff line number Diff line
@@ -336,7 +336,7 @@ EXPORT_SYMBOL(blk_queue_end_tag); 
int blk_queue_start_tag(struct request_queue *q, struct request *rq)

{

	struct blk_queue_tag *bqt = q->queue_tags;

	unsigned max_depth, offset;

	unsigned max_depth;

	int tag;



	if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
@@ -355,13 +355,16 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq) 
	 * to starve sync IO on behalf of flooding async IO.

	 */

	max_depth = bqt->max_depth;

	if (rq_is_sync(rq))

		offset = 0;

	else

		offset = max_depth >> 2;

	if (!rq_is_sync(rq) && max_depth > 1) {

		max_depth -= 2;

		if (!max_depth)

			max_depth = 1;

		if (q->in_flight[0] > max_depth)

			return 1;

	}



	do {

		tag = find_next_zero_bit(bqt->tag_map, max_depth, offset);

		tag = find_first_zero_bit(bqt->tag_map, max_depth);

		if (tag >= max_depth)

			return 1;

block/elevator.c

+4 −4
Original line number Diff line number Diff line
@@ -546,7 +546,7 @@ void elv_requeue_request(struct request_queue *q, struct request *rq) 
	 * in_flight count again

	 */

	if (blk_account_rq(rq)) {

		q->in_flight--;

		q->in_flight[rq_is_sync(rq)]--;

		if (blk_sorted_rq(rq))

			elv_deactivate_rq(q, rq);

	}
@@ -685,7 +685,7 @@ void elv_insert(struct request_queue *q, struct request *rq, int where) 


	if (unplug_it && blk_queue_plugged(q)) {

		int nrq = q->rq.count[BLK_RW_SYNC] + q->rq.count[BLK_RW_ASYNC]

			- q->in_flight;

				- queue_in_flight(q);



		if (nrq >= q->unplug_thresh)

			__generic_unplug_device(q);
@@ -823,7 +823,7 @@ void elv_completed_request(struct request_queue *q, struct request *rq) 
	 * request is released from the driver, io must be done

	 */

	if (blk_account_rq(rq)) {

		q->in_flight--;

		q->in_flight[rq_is_sync(rq)]--;

		if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)

			e->ops->elevator_completed_req_fn(q, rq);

	}
@@ -838,7 +838,7 @@ void elv_completed_request(struct request_queue *q, struct request *rq) 
		if (!list_empty(&q->queue_head))

			next = list_entry_rq(q->queue_head.next);



		if (!q->in_flight &&

		if (!queue_in_flight(q) &&

		    blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&

		    (!next || blk_ordered_req_seq(next) > QUEUE_ORDSEQ_DRAIN)) {

			blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);

include/linux/blkdev.h

+6 −1
Original line number Diff line number Diff line
@@ -404,7 +404,7 @@ struct request_queue 
	struct list_head	tag_busy_list;



	unsigned int		nr_sorted;

	unsigned int		in_flight;

	unsigned int		in_flight[2];



	unsigned int		rq_timeout;

	struct timer_list	timeout;
@@ -511,6 +511,11 @@ static inline void queue_flag_clear_unlocked(unsigned int flag, 
	__clear_bit(flag, &q->queue_flags);

}



static inline int queue_in_flight(struct request_queue *q)

{

	return q->in_flight[0] + q->in_flight[1];

}



static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)

{

	WARN_ON_ONCE(!queue_is_locked(q));