Commit e17fc0a1 authored by David Woodhouse's avatar David Woodhouse Committed by Jens Axboe
Browse files

Allow elevators to sort/merge discard requests 



But blkdev_issue_discard() still emits requests which are interpreted as
soft barriers, because naïve callers might otherwise issue subsequent
writes to those same sectors, which might cross on the queue (if they're
reallocated quickly enough).

Callers still _can_ issue non-barrier discard requests, but they have to
take care of queue ordering for themselves.

Signed-off-by: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent d30a2605

block/blk-barrier.c

+1 −1
Original line number Diff line number Diff line
@@ -372,7 +372,7 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, 
			nr_sects = 0;

		}

		bio_get(bio);

		submit_bio(WRITE_DISCARD, bio);

		submit_bio(DISCARD_BARRIER, bio);



		/* Check if it failed immediately */

		if (bio_flagged(bio, BIO_EOPNOTSUPP))

block/blk-core.c

+7 −5
Original line number Diff line number Diff line
@@ -1077,12 +1077,13 @@ void init_request_from_bio(struct request *req, struct bio *bio) 
	/*

	 * REQ_BARRIER implies no merging, but lets make it explicit

	 */

	if (unlikely(bio_barrier(bio)))

		req->cmd_flags |= (REQ_HARDBARRIER | REQ_NOMERGE);

	if (unlikely(bio_discard(bio))) {

		req->cmd_flags |= (REQ_SOFTBARRIER | REQ_DISCARD);

		req->cmd_flags |= REQ_DISCARD;

		if (bio_barrier(bio))

			req->cmd_flags |= REQ_SOFTBARRIER;

		req->q->prepare_discard_fn(req->q, req);

	}

	} else if (unlikely(bio_barrier(bio)))

		req->cmd_flags |= (REQ_HARDBARRIER | REQ_NOMERGE);



	if (bio_sync(bio))

		req->cmd_flags |= REQ_RW_SYNC;
@@ -1114,7 +1115,8 @@ static int __make_request(struct request_queue *q, struct bio *bio) 
	blk_queue_bounce(q, &bio);



	barrier = bio_barrier(bio);

	if (unlikely(barrier) && (q->next_ordered == QUEUE_ORDERED_NONE)) {

	if (unlikely(barrier) && bio_has_data(bio) &&

	    (q->next_ordered == QUEUE_ORDERED_NONE)) {

		err = -EOPNOTSUPP;

		goto end_io;

	}

block/blk-merge.c

+17 −10
Original line number Diff line number Diff line
@@ -11,7 +11,7 @@ 


void blk_recalc_rq_sectors(struct request *rq, int nsect)

{

	if (blk_fs_request(rq)) {

	if (blk_fs_request(rq) || blk_discard_rq(rq)) {

		rq->hard_sector += nsect;

		rq->hard_nr_sectors -= nsect;
@@ -131,13 +131,17 @@ static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, 
	if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))

		return 0;



	if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))

		return 0;

	if (bio->bi_size + nxt->bi_size > q->max_segment_size)

		return 0;



	if (!bio_has_data(bio))

		return 1;



	if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))

		return 0;



	/*

	 * bio and nxt are contigous in memory, check if the queue allows

	 * bio and nxt are contiguous in memory; check if the queue allows

	 * these two to be merged into one

	 */

	if (BIO_SEG_BOUNDARY(q, bio, nxt))
@@ -153,8 +157,9 @@ static int blk_hw_contig_segment(struct request_queue *q, struct bio *bio, 
		blk_recount_segments(q, bio);

	if (!bio_flagged(nxt, BIO_SEG_VALID))

		blk_recount_segments(q, nxt);

	if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||

	    BIOVEC_VIRT_OVERSIZE(bio->bi_hw_back_size + nxt->bi_hw_front_size))

	if (bio_has_data(bio) &&

	    (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||

	     BIOVEC_VIRT_OVERSIZE(bio->bi_hw_back_size + nxt->bi_hw_front_size)))

		return 0;

	if (bio->bi_hw_back_size + nxt->bi_hw_front_size > q->max_segment_size)

		return 0;
@@ -317,8 +322,9 @@ int ll_back_merge_fn(struct request_queue *q, struct request *req, 
	if (!bio_flagged(bio, BIO_SEG_VALID))

		blk_recount_segments(q, bio);

	len = req->biotail->bi_hw_back_size + bio->bi_hw_front_size;

	if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio))

	    && !BIOVEC_VIRT_OVERSIZE(len)) {

	if (!bio_has_data(bio) || 

	    (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio))

	     && !BIOVEC_VIRT_OVERSIZE(len))) {

		int mergeable =  ll_new_mergeable(q, req, bio);



		if (mergeable) {
@@ -356,8 +362,9 @@ int ll_front_merge_fn(struct request_queue *q, struct request *req, 
		blk_recount_segments(q, bio);

	if (!bio_flagged(req->bio, BIO_SEG_VALID))

		blk_recount_segments(q, req->bio);

	if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) &&

	    !BIOVEC_VIRT_OVERSIZE(len)) {

	if (!bio_has_data(bio) || 

	    (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) &&

	     !BIOVEC_VIRT_OVERSIZE(len))) {

		int mergeable =  ll_new_mergeable(q, req, bio);



		if (mergeable) {

block/elevator.c

+10 −2
Original line number Diff line number Diff line
@@ -74,6 +74,12 @@ int 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_discard(bio) != bio_discard(rq->bio))

		return 0;



	/*

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

	 */
@@ -438,6 +444,8 @@ void elv_dispatch_sort(struct request_queue *q, struct request *rq) 
	list_for_each_prev(entry, &q->queue_head) {

		struct request *pos = list_entry_rq(entry);



		if (blk_discard_rq(rq) != blk_discard_rq(pos))

			break;

		if (rq_data_dir(rq) != rq_data_dir(pos))

			break;

		if (pos->cmd_flags & stop_flags)
@@ -607,7 +615,7 @@ void elv_insert(struct request_queue *q, struct request *rq, int where) 
		break;



	case ELEVATOR_INSERT_SORT:

		BUG_ON(!blk_fs_request(rq));

		BUG_ON(!blk_fs_request(rq) && !blk_discard_rq(rq));

		rq->cmd_flags |= REQ_SORTED;

		q->nr_sorted++;

		if (rq_mergeable(rq)) {
@@ -692,7 +700,7 @@ void __elv_add_request(struct request_queue *q, struct request *rq, int where, 
		 * this request is scheduling boundary, update

		 * end_sector

		 */

		if (blk_fs_request(rq)) {

		if (blk_fs_request(rq) || blk_discard_rq(rq)) {

			q->end_sector = rq_end_sector(rq);

			q->boundary_rq = rq;

		}

block/ioctl.c

+1 −1
Original line number Diff line number Diff line
@@ -161,7 +161,7 @@ static int blk_ioctl_discard(struct block_device *bdev, uint64_t start, 
			bio->bi_size = len << 9;

			len = 0;

		}

		submit_bio(WRITE_DISCARD, bio);

		submit_bio(DISCARD_NOBARRIER, bio);



		wait_for_completion(&wait);

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