Commit 050c8ea8 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

block: separate out blk_rq_merge_ok() and blk_try_merge() from elevator functions 



blk_rq_merge_ok() is the elevator-neutral part of merge eligibility
test.  blk_try_merge() determines merge direction and expects the
caller to have tested elv_rq_merge_ok() previously.

elv_rq_merge_ok() now wraps blk_rq_merge_ok() and then calls
elv_iosched_allow_merge().  elv_try_merge() is removed and the two
callers are updated to call elv_rq_merge_ok() explicitly followed by
blk_try_merge().  While at it, make rq_merge_ok() functions return
bool.

This is to prepare for plug merge update and doesn't introduce any
behavior change.

This is based on Jens' patch to skip elevator_allow_merge_fn() from
plug merge.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
LKML-Reference: <4F16F3CA.90904@kernel.dk>
Original-patch-by: default avatarJens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 4e8670e2

block/blk-core.c

+2 −2
Original line number Diff line number Diff line
@@ -1282,10 +1282,10 @@ static bool attempt_plug_merge(struct request_queue *q, struct bio *bio, 


		(*request_count)++;



		if (rq->q != q)

		if (rq->q != q || !elv_rq_merge_ok(rq, bio))

			continue;



		el_ret = elv_try_merge(rq, bio);

		el_ret = blk_try_merge(rq, bio);

		if (el_ret == ELEVATOR_BACK_MERGE) {

			ret = bio_attempt_back_merge(q, rq, bio);

			if (ret)

block/blk-merge.c

+37 −0
Original line number Diff line number Diff line
@@ -471,3 +471,40 @@ int blk_attempt_req_merge(struct request_queue *q, struct request *rq, 
{

	return attempt_merge(q, rq, next);

}



bool blk_rq_merge_ok(struct request *rq, struct bio *bio)

{

	if (!rq_mergeable(rq))

		return false;



	/* don't merge file system requests and discard requests */

	if ((bio->bi_rw & REQ_DISCARD) != (rq->bio->bi_rw & REQ_DISCARD))

		return false;



	/* don't merge discard requests and secure discard requests */

	if ((bio->bi_rw & REQ_SECURE) != (rq->bio->bi_rw & REQ_SECURE))

		return false;



	/* different data direction or already started, don't merge */

	if (bio_data_dir(bio) != rq_data_dir(rq))

		return false;



	/* must be same device and not a special request */

	if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)

		return false;



	/* only merge integrity protected bio into ditto rq */

	if (bio_integrity(bio) != blk_integrity_rq(rq))

		return false;



	return true;

}



int blk_try_merge(struct request *rq, struct bio *bio)

{

	if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_sector)

		return ELEVATOR_BACK_MERGE;

	else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_sector)

		return ELEVATOR_FRONT_MERGE;

	return ELEVATOR_NO_MERGE;

}

block/blk.h

+2 −0
Original line number Diff line number Diff line
@@ -137,6 +137,8 @@ int blk_attempt_req_merge(struct request_queue *q, struct request *rq, 
				struct request *next);

void blk_recalc_rq_segments(struct request *rq);

void blk_rq_set_mixed_merge(struct request *rq);

bool blk_rq_merge_ok(struct request *rq, struct bio *bio);

int blk_try_merge(struct request *rq, struct bio *bio);



void blk_queue_congestion_threshold(struct request_queue *q);

block/elevator.c

+4 −51
Original line number Diff line number Diff line
@@ -70,39 +70,9 @@ static int elv_iosched_allow_merge(struct request *rq, struct bio *bio) 
/*

 * can we safely merge with this request?

 */

int elv_rq_merge_ok(struct request *rq, struct bio *bio)

bool elv_rq_merge_ok(struct request *rq, struct bio *bio)

{

	if (!rq_mergeable(rq))

		return 0;



	/*

	 * Don't merge file system requests and discard requests

	 */

	if ((bio->bi_rw & REQ_DISCARD) != (rq->bio->bi_rw & REQ_DISCARD))

		return 0;



	/*

	 * Don't merge discard requests and secure discard requests

	 */

	if ((bio->bi_rw & REQ_SECURE) != (rq->bio->bi_rw & REQ_SECURE))

		return 0;



	/*

	 * different data direction or already started, don't merge

	 */

	if (bio_data_dir(bio) != rq_data_dir(rq))

		return 0;



	/*

	 * must be same device and not a special request

	 */

	if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)

		return 0;



	/*

	 * only merge integrity protected bio into ditto rq

	 */

	if (bio_integrity(bio) != blk_integrity_rq(rq))

	if (!blk_rq_merge_ok(rq, bio))

		return 0;



	if (!elv_iosched_allow_merge(rq, bio))
@@ -112,23 +82,6 @@ int elv_rq_merge_ok(struct request *rq, struct bio *bio) 
}

EXPORT_SYMBOL(elv_rq_merge_ok);



int elv_try_merge(struct request *__rq, struct bio *bio)

{

	int ret = ELEVATOR_NO_MERGE;



	/*

	 * we can merge and sequence is ok, check if it's possible

	 */

	if (elv_rq_merge_ok(__rq, bio)) {

		if (blk_rq_pos(__rq) + blk_rq_sectors(__rq) == bio->bi_sector)

			ret = ELEVATOR_BACK_MERGE;

		else if (blk_rq_pos(__rq) - bio_sectors(bio) == bio->bi_sector)

			ret = ELEVATOR_FRONT_MERGE;

	}



	return ret;

}



static struct elevator_type *elevator_find(const char *name)

{

	struct elevator_type *e;
@@ -478,8 +431,8 @@ int elv_merge(struct request_queue *q, struct request **req, struct bio *bio) 
	/*

	 * First try one-hit cache.

	 */

	if (q->last_merge) {

		ret = elv_try_merge(q->last_merge, bio);

	if (q->last_merge && elv_rq_merge_ok(q->last_merge, bio)) {

		ret = blk_try_merge(q->last_merge, bio);

		if (ret != ELEVATOR_NO_MERGE) {

			*req = q->last_merge;

			return ret;

include/linux/elevator.h

+1 −2
Original line number Diff line number Diff line
@@ -122,7 +122,6 @@ extern void elv_dispatch_add_tail(struct request_queue *, struct request *); 
extern void elv_add_request(struct request_queue *, struct request *, int);

extern void __elv_add_request(struct request_queue *, struct request *, int);

extern int elv_merge(struct request_queue *, struct request **, struct bio *);

extern int elv_try_merge(struct request *, struct bio *);

extern void elv_merge_requests(struct request_queue *, struct request *,

			       struct request *);

extern void elv_merged_request(struct request_queue *, struct request *, int);
@@ -155,7 +154,7 @@ extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t); 
extern int elevator_init(struct request_queue *, char *);

extern void elevator_exit(struct elevator_queue *);

extern int elevator_change(struct request_queue *, const char *);

extern int elv_rq_merge_ok(struct request *, struct bio *);

extern bool elv_rq_merge_ok(struct request *, struct bio *);



/*

 * Helper functions.

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