blk-merge.c 20.3 KB
Newer Older
1
// SPDX-License-Identifier: GPL-2.0
2 3 4 5 6 7 8 9 10
/*
 * Functions related to segment and merge handling
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/scatterlist.h>

11 12
#include <trace/events/block.h>

13 14
#include "blk.h"

15 16
static struct bio *blk_bio_discard_split(struct request_queue *q,
					 struct bio *bio,
17 18
					 struct bio_set *bs,
					 unsigned *nsegs)
19 20 21 22 23 24
{
	unsigned int max_discard_sectors, granularity;
	int alignment;
	sector_t tmp;
	unsigned split_sectors;

25 26
	*nsegs = 1;

27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57
	/* Zero-sector (unknown) and one-sector granularities are the same.  */
	granularity = max(q->limits.discard_granularity >> 9, 1U);

	max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
	max_discard_sectors -= max_discard_sectors % granularity;

	if (unlikely(!max_discard_sectors)) {
		/* XXX: warn */
		return NULL;
	}

	if (bio_sectors(bio) <= max_discard_sectors)
		return NULL;

	split_sectors = max_discard_sectors;

	/*
	 * If the next starting sector would be misaligned, stop the discard at
	 * the previous aligned sector.
	 */
	alignment = (q->limits.discard_alignment >> 9) % granularity;

	tmp = bio->bi_iter.bi_sector + split_sectors - alignment;
	tmp = sector_div(tmp, granularity);

	if (split_sectors > tmp)
		split_sectors -= tmp;

	return bio_split(bio, split_sectors, GFP_NOIO, bs);
}

58 59 60 61 62 63 64 65 66 67 68 69 70 71
static struct bio *blk_bio_write_zeroes_split(struct request_queue *q,
		struct bio *bio, struct bio_set *bs, unsigned *nsegs)
{
	*nsegs = 1;

	if (!q->limits.max_write_zeroes_sectors)
		return NULL;

	if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors)
		return NULL;

	return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs);
}

72 73
static struct bio *blk_bio_write_same_split(struct request_queue *q,
					    struct bio *bio,
74 75
					    struct bio_set *bs,
					    unsigned *nsegs)
76
{
77 78
	*nsegs = 1;

79 80 81 82 83 84 85 86 87
	if (!q->limits.max_write_same_sectors)
		return NULL;

	if (bio_sectors(bio) <= q->limits.max_write_same_sectors)
		return NULL;

	return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
}

88 89 90 91 92 93 94 95 96 97 98 99
static inline unsigned get_max_io_size(struct request_queue *q,
				       struct bio *bio)
{
	unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);
	unsigned mask = queue_logical_block_size(q) - 1;

	/* aligned to logical block size */
	sectors &= ~(mask >> 9);

	return sectors;
}

100 101
static struct bio *blk_bio_segment_split(struct request_queue *q,
					 struct bio *bio,
102 103
					 struct bio_set *bs,
					 unsigned *segs)
104
{
105
	struct bio_vec bv, bvprv, *bvprvp = NULL;
106
	struct bvec_iter iter;
107
	unsigned seg_size = 0, nsegs = 0, sectors = 0;
M
Ming Lei 已提交
108 109 110
	unsigned front_seg_size = bio->bi_seg_front_size;
	bool do_split = true;
	struct bio *new = NULL;
111
	const unsigned max_sectors = get_max_io_size(q, bio);
112 113 114 115 116 117

	bio_for_each_segment(bv, bio, iter) {
		/*
		 * If the queue doesn't support SG gaps and adding this
		 * offset would create a gap, disallow it.
		 */
118
		if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
119 120
			goto split;

121
		if (sectors + (bv.bv_len >> 9) > max_sectors) {
122 123 124 125 126
			/*
			 * Consider this a new segment if we're splitting in
			 * the middle of this vector.
			 */
			if (nsegs < queue_max_segments(q) &&
127
			    sectors < max_sectors) {
128
				nsegs++;
129
				sectors = max_sectors;
130
			}
131
			goto split;
132 133
		}

134
		if (bvprvp && blk_queue_cluster(q)) {
135 136
			if (seg_size + bv.bv_len > queue_max_segment_size(q))
				goto new_segment;
137
			if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv))
138
				goto new_segment;
139
			if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv))
140 141 142 143
				goto new_segment;

			seg_size += bv.bv_len;
			bvprv = bv;
M
Ming Lei 已提交
144
			bvprvp = &bvprv;
145
			sectors += bv.bv_len >> 9;
146

147 148 149 150 151 152
			continue;
		}
new_segment:
		if (nsegs == queue_max_segments(q))
			goto split;

153 154 155
		if (nsegs == 1 && seg_size > front_seg_size)
			front_seg_size = seg_size;

156 157
		nsegs++;
		bvprv = bv;
M
Ming Lei 已提交
158
		bvprvp = &bvprv;
159
		seg_size = bv.bv_len;
160
		sectors += bv.bv_len >> 9;
M
Ming Lei 已提交
161

162 163
	}

M
Ming Lei 已提交
164
	do_split = false;
165
split:
166
	*segs = nsegs;
M
Ming Lei 已提交
167 168 169 170 171 172 173

	if (do_split) {
		new = bio_split(bio, sectors, GFP_NOIO, bs);
		if (new)
			bio = new;
	}

174 175
	if (nsegs == 1 && seg_size > front_seg_size)
		front_seg_size = seg_size;
M
Ming Lei 已提交
176 177 178 179 180
	bio->bi_seg_front_size = front_seg_size;
	if (seg_size > bio->bi_seg_back_size)
		bio->bi_seg_back_size = seg_size;

	return do_split ? new : NULL;
181 182
}

183
void blk_queue_split(struct request_queue *q, struct bio **bio)
184
{
185 186
	struct bio *split, *res;
	unsigned nsegs;
187

A
Adrian Hunter 已提交
188 189 190
	switch (bio_op(*bio)) {
	case REQ_OP_DISCARD:
	case REQ_OP_SECURE_ERASE:
191
		split = blk_bio_discard_split(q, *bio, q->bio_split, &nsegs);
A
Adrian Hunter 已提交
192
		break;
193
	case REQ_OP_WRITE_ZEROES:
194
		split = blk_bio_write_zeroes_split(q, *bio, q->bio_split, &nsegs);
195
		break;
A
Adrian Hunter 已提交
196
	case REQ_OP_WRITE_SAME:
197
		split = blk_bio_write_same_split(q, *bio, q->bio_split, &nsegs);
A
Adrian Hunter 已提交
198 199
		break;
	default:
200
		split = blk_bio_segment_split(q, *bio, q->bio_split, &nsegs);
A
Adrian Hunter 已提交
201 202
		break;
	}
203 204 205 206 207

	/* physical segments can be figured out during splitting */
	res = split ? split : *bio;
	res->bi_phys_segments = nsegs;
	bio_set_flag(res, BIO_SEG_VALID);
208 209

	if (split) {
M
Ming Lei 已提交
210
		/* there isn't chance to merge the splitted bio */
J
Jens Axboe 已提交
211
		split->bi_opf |= REQ_NOMERGE;
M
Ming Lei 已提交
212

213
		bio_chain(split, *bio);
214
		trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
215 216 217 218 219 220
		generic_make_request(*bio);
		*bio = split;
	}
}
EXPORT_SYMBOL(blk_queue_split);

221
static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
M
Ming Lei 已提交
222 223
					     struct bio *bio,
					     bool no_sg_merge)
224
{
225
	struct bio_vec bv, bvprv = { NULL };
226
	int cluster, prev = 0;
227
	unsigned int seg_size, nr_phys_segs;
228
	struct bio *fbio, *bbio;
229
	struct bvec_iter iter;
230

231 232
	if (!bio)
		return 0;
233

234 235 236 237
	switch (bio_op(bio)) {
	case REQ_OP_DISCARD:
	case REQ_OP_SECURE_ERASE:
	case REQ_OP_WRITE_ZEROES:
238 239
		return 0;
	case REQ_OP_WRITE_SAME:
240
		return 1;
241
	}
242

243
	fbio = bio;
244
	cluster = blk_queue_cluster(q);
M
Mikulas Patocka 已提交
245
	seg_size = 0;
246
	nr_phys_segs = 0;
247
	for_each_bio(bio) {
248
		bio_for_each_segment(bv, bio, iter) {
249 250 251 252 253 254 255
			/*
			 * If SG merging is disabled, each bio vector is
			 * a segment
			 */
			if (no_sg_merge)
				goto new_segment;

256
			if (prev && cluster) {
257
				if (seg_size + bv.bv_len
258
				    > queue_max_segment_size(q))
259
					goto new_segment;
260
				if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv))
261
					goto new_segment;
262
				if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv))
263
					goto new_segment;
264

265
				seg_size += bv.bv_len;
266 267 268
				bvprv = bv;
				continue;
			}
269
new_segment:
270 271 272
			if (nr_phys_segs == 1 && seg_size >
			    fbio->bi_seg_front_size)
				fbio->bi_seg_front_size = seg_size;
273

274 275
			nr_phys_segs++;
			bvprv = bv;
276
			prev = 1;
277
			seg_size = bv.bv_len;
278
		}
279
		bbio = bio;
280 281
	}

282 283 284 285
	if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
		fbio->bi_seg_front_size = seg_size;
	if (seg_size > bbio->bi_seg_back_size)
		bbio->bi_seg_back_size = seg_size;
286 287 288 289 290 291

	return nr_phys_segs;
}

void blk_recalc_rq_segments(struct request *rq)
{
M
Ming Lei 已提交
292 293 294 295 296
	bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
			&rq->q->queue_flags);

	rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio,
			no_sg_merge);
297 298 299 300
}

void blk_recount_segments(struct request_queue *q, struct bio *bio)
{
301 302 303 304 305 306 307
	unsigned short seg_cnt;

	/* estimate segment number by bi_vcnt for non-cloned bio */
	if (bio_flagged(bio, BIO_CLONED))
		seg_cnt = bio_segments(bio);
	else
		seg_cnt = bio->bi_vcnt;
308

309 310 311
	if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
			(seg_cnt < queue_max_segments(q)))
		bio->bi_phys_segments = seg_cnt;
312 313 314 315
	else {
		struct bio *nxt = bio->bi_next;

		bio->bi_next = NULL;
316
		bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
317 318
		bio->bi_next = nxt;
	}
319

320
	bio_set_flag(bio, BIO_SEG_VALID);
321 322 323 324 325 326
}
EXPORT_SYMBOL(blk_recount_segments);

static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
				   struct bio *nxt)
{
327
	struct bio_vec end_bv = { NULL }, nxt_bv;
328

329
	if (!blk_queue_cluster(q))
330 331
		return 0;

332
	if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
333
	    queue_max_segment_size(q))
334 335
		return 0;

336 337 338
	if (!bio_has_data(bio))
		return 1;

339 340
	bio_get_last_bvec(bio, &end_bv);
	bio_get_first_bvec(nxt, &nxt_bv);
341 342

	if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv))
343 344
		return 0;

345
	/*
346
	 * bio and nxt are contiguous in memory; check if the queue allows
347 348
	 * these two to be merged into one
	 */
349
	if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv))
350 351 352 353 354
		return 1;

	return 0;
}

355
static inline void
356
__blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
357
		     struct scatterlist *sglist, struct bio_vec *bvprv,
358 359 360 361 362
		     struct scatterlist **sg, int *nsegs, int *cluster)
{

	int nbytes = bvec->bv_len;

363
	if (*sg && *cluster) {
364 365 366
		if ((*sg)->length + nbytes > queue_max_segment_size(q))
			goto new_segment;

367
		if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
368
			goto new_segment;
369
		if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387
			goto new_segment;

		(*sg)->length += nbytes;
	} else {
new_segment:
		if (!*sg)
			*sg = sglist;
		else {
			/*
			 * If the driver previously mapped a shorter
			 * list, we could see a termination bit
			 * prematurely unless it fully inits the sg
			 * table on each mapping. We KNOW that there
			 * must be more entries here or the driver
			 * would be buggy, so force clear the
			 * termination bit to avoid doing a full
			 * sg_init_table() in drivers for each command.
			 */
388
			sg_unmark_end(*sg);
389 390 391 392 393 394
			*sg = sg_next(*sg);
		}

		sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
		(*nsegs)++;
	}
395
	*bvprv = *bvec;
396 397
}

398 399 400 401 402 403 404 405
static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv,
		struct scatterlist *sglist, struct scatterlist **sg)
{
	*sg = sglist;
	sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
	return 1;
}

406 407 408
static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
			     struct scatterlist *sglist,
			     struct scatterlist **sg)
409
{
410
	struct bio_vec bvec, bvprv = { NULL };
411
	struct bvec_iter iter;
412
	int cluster = blk_queue_cluster(q), nsegs = 0;
413 414 415 416 417

	for_each_bio(bio)
		bio_for_each_segment(bvec, bio, iter)
			__blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
					     &nsegs, &cluster);
418

419 420 421 422 423 424 425 426 427 428 429 430 431
	return nsegs;
}

/*
 * map a request to scatterlist, return number of sg entries setup. Caller
 * must make sure sg can hold rq->nr_phys_segments entries
 */
int blk_rq_map_sg(struct request_queue *q, struct request *rq,
		  struct scatterlist *sglist)
{
	struct scatterlist *sg = NULL;
	int nsegs = 0;

432 433 434 435 436
	if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
		nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg);
	else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME)
		nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg);
	else if (rq->bio)
437
		nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
438

439
	if (unlikely(rq->rq_flags & RQF_COPY_USER) &&
440 441 442
	    (blk_rq_bytes(rq) & q->dma_pad_mask)) {
		unsigned int pad_len =
			(q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
443 444 445 446 447

		sg->length += pad_len;
		rq->extra_len += pad_len;
	}

448
	if (q->dma_drain_size && q->dma_drain_needed(rq)) {
449
		if (op_is_write(req_op(rq)))
450 451
			memset(q->dma_drain_buffer, 0, q->dma_drain_size);

452
		sg_unmark_end(sg);
453 454 455 456 457 458
		sg = sg_next(sg);
		sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
			    q->dma_drain_size,
			    ((unsigned long)q->dma_drain_buffer) &
			    (PAGE_SIZE - 1));
		nsegs++;
459
		rq->extra_len += q->dma_drain_size;
460 461 462 463 464
	}

	if (sg)
		sg_mark_end(sg);

465 466 467 468
	/*
	 * Something must have been wrong if the figured number of
	 * segment is bigger than number of req's physical segments
	 */
469
	WARN_ON(nsegs > blk_rq_nr_phys_segments(rq));
470

471 472 473 474 475 476 477 478 479 480
	return nsegs;
}
EXPORT_SYMBOL(blk_rq_map_sg);

static inline int ll_new_hw_segment(struct request_queue *q,
				    struct request *req,
				    struct bio *bio)
{
	int nr_phys_segs = bio_phys_segments(q, bio);

481 482 483
	if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
		goto no_merge;

484
	if (blk_integrity_merge_bio(q, req, bio) == false)
485
		goto no_merge;
486 487 488 489 490 491 492

	/*
	 * This will form the start of a new hw segment.  Bump both
	 * counters.
	 */
	req->nr_phys_segments += nr_phys_segs;
	return 1;
493 494

no_merge:
R
Ritesh Harjani 已提交
495
	req_set_nomerge(q, req);
496
	return 0;
497 498 499 500 501
}

int ll_back_merge_fn(struct request_queue *q, struct request *req,
		     struct bio *bio)
{
502 503
	if (req_gap_back_merge(req, bio))
		return 0;
504 505 506
	if (blk_integrity_rq(req) &&
	    integrity_req_gap_back_merge(req, bio))
		return 0;
507
	if (blk_rq_sectors(req) + bio_sectors(bio) >
D
Damien Le Moal 已提交
508
	    blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
R
Ritesh Harjani 已提交
509
		req_set_nomerge(q, req);
510 511
		return 0;
	}
512
	if (!bio_flagged(req->biotail, BIO_SEG_VALID))
513
		blk_recount_segments(q, req->biotail);
514
	if (!bio_flagged(bio, BIO_SEG_VALID))
515 516 517 518 519
		blk_recount_segments(q, bio);

	return ll_new_hw_segment(q, req, bio);
}

520
int ll_front_merge_fn(struct request_queue *q, struct request *req,
521 522
		      struct bio *bio)
{
523 524 525

	if (req_gap_front_merge(req, bio))
		return 0;
526 527 528
	if (blk_integrity_rq(req) &&
	    integrity_req_gap_front_merge(req, bio))
		return 0;
529
	if (blk_rq_sectors(req) + bio_sectors(bio) >
D
Damien Le Moal 已提交
530
	    blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
R
Ritesh Harjani 已提交
531
		req_set_nomerge(q, req);
532 533
		return 0;
	}
534
	if (!bio_flagged(bio, BIO_SEG_VALID))
535
		blk_recount_segments(q, bio);
536
	if (!bio_flagged(req->bio, BIO_SEG_VALID))
537 538 539 540 541
		blk_recount_segments(q, req->bio);

	return ll_new_hw_segment(q, req, bio);
}

542 543 544 545 546 547 548 549 550 551 552
/*
 * blk-mq uses req->special to carry normal driver per-request payload, it
 * does not indicate a prepared command that we cannot merge with.
 */
static bool req_no_special_merge(struct request *req)
{
	struct request_queue *q = req->q;

	return !q->mq_ops && req->special;
}

553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570
static bool req_attempt_discard_merge(struct request_queue *q, struct request *req,
		struct request *next)
{
	unsigned short segments = blk_rq_nr_discard_segments(req);

	if (segments >= queue_max_discard_segments(q))
		goto no_merge;
	if (blk_rq_sectors(req) + bio_sectors(next->bio) >
	    blk_rq_get_max_sectors(req, blk_rq_pos(req)))
		goto no_merge;

	req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next);
	return true;
no_merge:
	req_set_nomerge(q, req);
	return false;
}

571 572 573 574
static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
				struct request *next)
{
	int total_phys_segments;
575 576
	unsigned int seg_size =
		req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
577 578 579 580 581

	/*
	 * First check if the either of the requests are re-queued
	 * requests.  Can't merge them if they are.
	 */
582
	if (req_no_special_merge(req) || req_no_special_merge(next))
583 584
		return 0;

585
	if (req_gap_back_merge(req, next->bio))
586 587
		return 0;

588 589 590
	/*
	 * Will it become too large?
	 */
591
	if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
D
Damien Le Moal 已提交
592
	    blk_rq_get_max_sectors(req, blk_rq_pos(req)))
593 594 595
		return 0;

	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
596 597 598 599 600
	if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
		if (req->nr_phys_segments == 1)
			req->bio->bi_seg_front_size = seg_size;
		if (next->nr_phys_segments == 1)
			next->biotail->bi_seg_back_size = seg_size;
601
		total_phys_segments--;
602
	}
603

604
	if (total_phys_segments > queue_max_segments(q))
605 606
		return 0;

607
	if (blk_integrity_merge_rq(q, req, next) == false)
608 609
		return 0;

610 611 612 613 614
	/* Merge is OK... */
	req->nr_phys_segments = total_phys_segments;
	return 1;
}

615 616 617 618 619 620 621 622 623 624 625 626 627 628
/**
 * blk_rq_set_mixed_merge - mark a request as mixed merge
 * @rq: request to mark as mixed merge
 *
 * Description:
 *     @rq is about to be mixed merged.  Make sure the attributes
 *     which can be mixed are set in each bio and mark @rq as mixed
 *     merged.
 */
void blk_rq_set_mixed_merge(struct request *rq)
{
	unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
	struct bio *bio;

629
	if (rq->rq_flags & RQF_MIXED_MERGE)
630 631 632 633 634 635 636 637
		return;

	/*
	 * @rq will no longer represent mixable attributes for all the
	 * contained bios.  It will just track those of the first one.
	 * Distributes the attributs to each bio.
	 */
	for (bio = rq->bio; bio; bio = bio->bi_next) {
J
Jens Axboe 已提交
638 639 640
		WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) &&
			     (bio->bi_opf & REQ_FAILFAST_MASK) != ff);
		bio->bi_opf |= ff;
641
	}
642
	rq->rq_flags |= RQF_MIXED_MERGE;
643 644
}

645 646 647 648 649 650 651
static void blk_account_io_merge(struct request *req)
{
	if (blk_do_io_stat(req)) {
		struct hd_struct *part;
		int cpu;

		cpu = part_stat_lock();
652
		part = req->part;
653

654 655
		part_round_stats(req->q, cpu, part);
		part_dec_in_flight(req->q, part, rq_data_dir(req));
656

657
		hd_struct_put(part);
658 659 660 661
		part_stat_unlock();
	}
}

662
/*
663 664
 * For non-mq, this has to be called with the request spinlock acquired.
 * For mq with scheduling, the appropriate queue wide lock should be held.
665
 */
666 667
static struct request *attempt_merge(struct request_queue *q,
				     struct request *req, struct request *next)
668
{
669 670 671
	if (!q->mq_ops)
		lockdep_assert_held(q->queue_lock);

672
	if (!rq_mergeable(req) || !rq_mergeable(next))
673
		return NULL;
674

675
	if (req_op(req) != req_op(next))
676
		return NULL;
677

678 679 680
	/*
	 * not contiguous
	 */
681
	if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
682
		return NULL;
683 684 685

	if (rq_data_dir(req) != rq_data_dir(next)
	    || req->rq_disk != next->rq_disk
686
	    || req_no_special_merge(next))
687
		return NULL;
688

689
	if (req_op(req) == REQ_OP_WRITE_SAME &&
690
	    !blk_write_same_mergeable(req->bio, next->bio))
691
		return NULL;
692

693 694 695 696 697 698 699
	/*
	 * Don't allow merge of different write hints, or for a hint with
	 * non-hint IO.
	 */
	if (req->write_hint != next->write_hint)
		return NULL;

700 701 702 703
	/*
	 * If we are allowed to merge, then append bio list
	 * from next to rq and release next. merge_requests_fn
	 * will have updated segment counts, update sector
704 705
	 * counts here. Handle DISCARDs separately, as they
	 * have separate settings.
706
	 */
707 708 709 710
	if (req_op(req) == REQ_OP_DISCARD) {
		if (!req_attempt_discard_merge(q, req, next))
			return NULL;
	} else if (!ll_merge_requests_fn(q, req, next))
711
		return NULL;
712

713 714 715 716 717 718
	/*
	 * If failfast settings disagree or any of the two is already
	 * a mixed merge, mark both as mixed before proceeding.  This
	 * makes sure that all involved bios have mixable attributes
	 * set properly.
	 */
719
	if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) ||
720 721 722 723 724 725
	    (req->cmd_flags & REQ_FAILFAST_MASK) !=
	    (next->cmd_flags & REQ_FAILFAST_MASK)) {
		blk_rq_set_mixed_merge(req);
		blk_rq_set_mixed_merge(next);
	}

726
	/*
727 728 729
	 * At this point we have either done a back merge or front merge. We
	 * need the smaller start_time_ns of the merged requests to be the
	 * current request for accounting purposes.
730
	 */
731 732
	if (next->start_time_ns < req->start_time_ns)
		req->start_time_ns = next->start_time_ns;
733 734 735 736

	req->biotail->bi_next = next->bio;
	req->biotail = next->biotail;

737
	req->__data_len += blk_rq_bytes(next);
738

739 740
	if (req_op(req) != REQ_OP_DISCARD)
		elv_merge_requests(q, req, next);
741

742 743 744 745
	/*
	 * 'next' is going away, so update stats accordingly
	 */
	blk_account_io_merge(next);
746 747

	req->ioprio = ioprio_best(req->ioprio, next->ioprio);
748 749
	if (blk_rq_cpu_valid(next))
		req->cpu = next->cpu;
750

751 752 753 754
	/*
	 * ownership of bio passed from next to req, return 'next' for
	 * the caller to free
	 */
755
	next->bio = NULL;
756
	return next;
757 758
}

759
struct request *attempt_back_merge(struct request_queue *q, struct request *rq)
760 761 762 763 764 765
{
	struct request *next = elv_latter_request(q, rq);

	if (next)
		return attempt_merge(q, rq, next);

766
	return NULL;
767 768
}

769
struct request *attempt_front_merge(struct request_queue *q, struct request *rq)
770 771 772 773 774 775
{
	struct request *prev = elv_former_request(q, rq);

	if (prev)
		return attempt_merge(q, prev, rq);

776
	return NULL;
777
}
778 779 780 781

int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
			  struct request *next)
{
782
	struct elevator_queue *e = q->elevator;
783
	struct request *free;
784

785
	if (!e->uses_mq && e->type->ops.sq.elevator_allow_rq_merge_fn)
786
		if (!e->type->ops.sq.elevator_allow_rq_merge_fn(q, rq, next))
787 788
			return 0;

789 790 791 792 793 794 795
	free = attempt_merge(q, rq, next);
	if (free) {
		__blk_put_request(q, free);
		return 1;
	}

	return 0;
796
}
797 798 799

bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
{
800
	if (!rq_mergeable(rq) || !bio_mergeable(bio))
801 802
		return false;

803
	if (req_op(rq) != bio_op(bio))
804 805
		return false;

806 807 808 809 810
	/* 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 */
811
	if (rq->rq_disk != bio->bi_disk || req_no_special_merge(rq))
812 813 814
		return false;

	/* only merge integrity protected bio into ditto rq */
815
	if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
816 817
		return false;

818
	/* must be using the same buffer */
819
	if (req_op(rq) == REQ_OP_WRITE_SAME &&
820 821 822
	    !blk_write_same_mergeable(rq->bio, bio))
		return false;

823 824 825 826 827 828 829
	/*
	 * Don't allow merge of different write hints, or for a hint with
	 * non-hint IO.
	 */
	if (rq->write_hint != bio->bi_write_hint)
		return false;

830 831 832
	return true;
}

833
enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
834
{
835 836 837 838
	if (req_op(rq) == REQ_OP_DISCARD &&
	    queue_max_discard_segments(rq->q) > 1)
		return ELEVATOR_DISCARD_MERGE;
	else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
839
		return ELEVATOR_BACK_MERGE;
840
	else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
841 842 843
		return ELEVATOR_FRONT_MERGE;
	return ELEVATOR_NO_MERGE;
}