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v6.9.4
   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Functions related to segment and merge handling
   4 */
   5#include <linux/kernel.h>
   6#include <linux/module.h>
   7#include <linux/bio.h>
   8#include <linux/blkdev.h>
   9#include <linux/blk-integrity.h>
  10#include <linux/scatterlist.h>
  11#include <linux/part_stat.h>
  12#include <linux/blk-cgroup.h>
  13
  14#include <trace/events/block.h>
  15
  16#include "blk.h"
  17#include "blk-mq-sched.h"
  18#include "blk-rq-qos.h"
  19#include "blk-throttle.h"
  20
  21static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv)
  22{
  23	*bv = mp_bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
  24}
  25
  26static inline void bio_get_last_bvec(struct bio *bio, struct bio_vec *bv)
  27{
  28	struct bvec_iter iter = bio->bi_iter;
  29	int idx;
  30
  31	bio_get_first_bvec(bio, bv);
  32	if (bv->bv_len == bio->bi_iter.bi_size)
  33		return;		/* this bio only has a single bvec */
  34
  35	bio_advance_iter(bio, &iter, iter.bi_size);
  36
  37	if (!iter.bi_bvec_done)
  38		idx = iter.bi_idx - 1;
  39	else	/* in the middle of bvec */
  40		idx = iter.bi_idx;
  41
  42	*bv = bio->bi_io_vec[idx];
  43
  44	/*
  45	 * iter.bi_bvec_done records actual length of the last bvec
  46	 * if this bio ends in the middle of one io vector
  47	 */
  48	if (iter.bi_bvec_done)
  49		bv->bv_len = iter.bi_bvec_done;
  50}
  51
  52static inline bool bio_will_gap(struct request_queue *q,
  53		struct request *prev_rq, struct bio *prev, struct bio *next)
  54{
  55	struct bio_vec pb, nb;
  56
  57	if (!bio_has_data(prev) || !queue_virt_boundary(q))
  58		return false;
  59
  60	/*
  61	 * Don't merge if the 1st bio starts with non-zero offset, otherwise it
  62	 * is quite difficult to respect the sg gap limit.  We work hard to
  63	 * merge a huge number of small single bios in case of mkfs.
  64	 */
  65	if (prev_rq)
  66		bio_get_first_bvec(prev_rq->bio, &pb);
  67	else
  68		bio_get_first_bvec(prev, &pb);
  69	if (pb.bv_offset & queue_virt_boundary(q))
  70		return true;
  71
  72	/*
  73	 * We don't need to worry about the situation that the merged segment
  74	 * ends in unaligned virt boundary:
  75	 *
  76	 * - if 'pb' ends aligned, the merged segment ends aligned
  77	 * - if 'pb' ends unaligned, the next bio must include
  78	 *   one single bvec of 'nb', otherwise the 'nb' can't
  79	 *   merge with 'pb'
  80	 */
  81	bio_get_last_bvec(prev, &pb);
  82	bio_get_first_bvec(next, &nb);
  83	if (biovec_phys_mergeable(q, &pb, &nb))
  84		return false;
  85	return __bvec_gap_to_prev(&q->limits, &pb, nb.bv_offset);
  86}
  87
  88static inline bool req_gap_back_merge(struct request *req, struct bio *bio)
  89{
  90	return bio_will_gap(req->q, req, req->biotail, bio);
  91}
  92
  93static inline bool req_gap_front_merge(struct request *req, struct bio *bio)
  94{
  95	return bio_will_gap(req->q, NULL, bio, req->bio);
  96}
  97
  98/*
  99 * The max size one bio can handle is UINT_MAX becasue bvec_iter.bi_size
 100 * is defined as 'unsigned int', meantime it has to be aligned to with the
 101 * logical block size, which is the minimum accepted unit by hardware.
 102 */
 103static unsigned int bio_allowed_max_sectors(const struct queue_limits *lim)
 104{
 105	return round_down(UINT_MAX, lim->logical_block_size) >> SECTOR_SHIFT;
 106}
 107
 108static struct bio *bio_split_discard(struct bio *bio,
 109				     const struct queue_limits *lim,
 110				     unsigned *nsegs, struct bio_set *bs)
 111{
 112	unsigned int max_discard_sectors, granularity;
 
 113	sector_t tmp;
 114	unsigned split_sectors;
 115
 116	*nsegs = 1;
 117
 118	granularity = max(lim->discard_granularity >> 9, 1U);
 
 119
 120	max_discard_sectors =
 121		min(lim->max_discard_sectors, bio_allowed_max_sectors(lim));
 122	max_discard_sectors -= max_discard_sectors % granularity;
 123	if (unlikely(!max_discard_sectors))
 
 
 124		return NULL;
 
 125
 126	if (bio_sectors(bio) <= max_discard_sectors)
 127		return NULL;
 128
 129	split_sectors = max_discard_sectors;
 130
 131	/*
 132	 * If the next starting sector would be misaligned, stop the discard at
 133	 * the previous aligned sector.
 134	 */
 135	tmp = bio->bi_iter.bi_sector + split_sectors -
 136		((lim->discard_alignment >> 9) % granularity);
 
 137	tmp = sector_div(tmp, granularity);
 138
 139	if (split_sectors > tmp)
 140		split_sectors -= tmp;
 141
 142	return bio_split(bio, split_sectors, GFP_NOIO, bs);
 143}
 144
 145static struct bio *bio_split_write_zeroes(struct bio *bio,
 146					  const struct queue_limits *lim,
 147					  unsigned *nsegs, struct bio_set *bs)
 
 148{
 149	*nsegs = 0;
 150	if (!lim->max_write_zeroes_sectors)
 151		return NULL;
 152	if (bio_sectors(bio) <= lim->max_write_zeroes_sectors)
 153		return NULL;
 154	return bio_split(bio, lim->max_write_zeroes_sectors, GFP_NOIO, bs);
 155}
 156
 157/*
 158 * Return the maximum number of sectors from the start of a bio that may be
 159 * submitted as a single request to a block device. If enough sectors remain,
 160 * align the end to the physical block size. Otherwise align the end to the
 161 * logical block size. This approach minimizes the number of non-aligned
 162 * requests that are submitted to a block device if the start of a bio is not
 163 * aligned to a physical block boundary.
 164 */
 165static inline unsigned get_max_io_size(struct bio *bio,
 166				       const struct queue_limits *lim)
 167{
 168	unsigned pbs = lim->physical_block_size >> SECTOR_SHIFT;
 169	unsigned lbs = lim->logical_block_size >> SECTOR_SHIFT;
 170	unsigned max_sectors = lim->max_sectors, start, end;
 171
 172	if (lim->chunk_sectors) {
 173		max_sectors = min(max_sectors,
 174			blk_chunk_sectors_left(bio->bi_iter.bi_sector,
 175					       lim->chunk_sectors));
 176	}
 177
 178	start = bio->bi_iter.bi_sector & (pbs - 1);
 179	end = (start + max_sectors) & ~(pbs - 1);
 180	if (end > start)
 181		return end - start;
 182	return max_sectors & ~(lbs - 1);
 183}
 184
 185/**
 186 * get_max_segment_size() - maximum number of bytes to add as a single segment
 187 * @lim: Request queue limits.
 188 * @start_page: See below.
 189 * @offset: Offset from @start_page where to add a segment.
 190 *
 191 * Returns the maximum number of bytes that can be added as a single segment.
 192 */
 193static inline unsigned get_max_segment_size(const struct queue_limits *lim,
 194		struct page *start_page, unsigned long offset)
 195{
 196	unsigned long mask = lim->seg_boundary_mask;
 197
 198	offset = mask & (page_to_phys(start_page) + offset);
 199
 200	/*
 201	 * Prevent an overflow if mask = ULONG_MAX and offset = 0 by adding 1
 202	 * after having calculated the minimum.
 203	 */
 204	return min(mask - offset, (unsigned long)lim->max_segment_size - 1) + 1;
 205}
 206
 207/**
 208 * bvec_split_segs - verify whether or not a bvec should be split in the middle
 209 * @lim:      [in] queue limits to split based on
 210 * @bv:       [in] bvec to examine
 211 * @nsegs:    [in,out] Number of segments in the bio being built. Incremented
 212 *            by the number of segments from @bv that may be appended to that
 213 *            bio without exceeding @max_segs
 214 * @bytes:    [in,out] Number of bytes in the bio being built. Incremented
 215 *            by the number of bytes from @bv that may be appended to that
 216 *            bio without exceeding @max_bytes
 217 * @max_segs: [in] upper bound for *@nsegs
 218 * @max_bytes: [in] upper bound for *@bytes
 219 *
 220 * When splitting a bio, it can happen that a bvec is encountered that is too
 221 * big to fit in a single segment and hence that it has to be split in the
 222 * middle. This function verifies whether or not that should happen. The value
 223 * %true is returned if and only if appending the entire @bv to a bio with
 224 * *@nsegs segments and *@sectors sectors would make that bio unacceptable for
 225 * the block driver.
 226 */
 227static bool bvec_split_segs(const struct queue_limits *lim,
 228		const struct bio_vec *bv, unsigned *nsegs, unsigned *bytes,
 229		unsigned max_segs, unsigned max_bytes)
 230{
 231	unsigned max_len = min(max_bytes, UINT_MAX) - *bytes;
 232	unsigned len = min(bv->bv_len, max_len);
 233	unsigned total_len = 0;
 234	unsigned seg_size = 0;
 235
 236	while (len && *nsegs < max_segs) {
 237		seg_size = get_max_segment_size(lim, bv->bv_page,
 238						bv->bv_offset + total_len);
 239		seg_size = min(seg_size, len);
 240
 241		(*nsegs)++;
 242		total_len += seg_size;
 243		len -= seg_size;
 244
 245		if ((bv->bv_offset + total_len) & lim->virt_boundary_mask)
 246			break;
 247	}
 248
 249	*bytes += total_len;
 
 250
 251	/* tell the caller to split the bvec if it is too big to fit */
 252	return len > 0 || bv->bv_len > max_len;
 253}
 254
 255/**
 256 * bio_split_rw - split a bio in two bios
 257 * @bio:  [in] bio to be split
 258 * @lim:  [in] queue limits to split based on
 259 * @segs: [out] number of segments in the bio with the first half of the sectors
 260 * @bs:	  [in] bio set to allocate the clone from
 261 * @max_bytes: [in] maximum number of bytes per bio
 262 *
 263 * Clone @bio, update the bi_iter of the clone to represent the first sectors
 264 * of @bio and update @bio->bi_iter to represent the remaining sectors. The
 265 * following is guaranteed for the cloned bio:
 266 * - That it has at most @max_bytes worth of data
 267 * - That it has at most queue_max_segments(@q) segments.
 268 *
 269 * Except for discard requests the cloned bio will point at the bi_io_vec of
 270 * the original bio. It is the responsibility of the caller to ensure that the
 271 * original bio is not freed before the cloned bio. The caller is also
 272 * responsible for ensuring that @bs is only destroyed after processing of the
 273 * split bio has finished.
 274 */
 275struct bio *bio_split_rw(struct bio *bio, const struct queue_limits *lim,
 276		unsigned *segs, struct bio_set *bs, unsigned max_bytes)
 277{
 278	struct bio_vec bv, bvprv, *bvprvp = NULL;
 279	struct bvec_iter iter;
 280	unsigned nsegs = 0, bytes = 0;
 
 
 
 
 281
 282	bio_for_each_bvec(bv, bio, iter) {
 283		/*
 284		 * If the queue doesn't support SG gaps and adding this
 285		 * offset would create a gap, disallow it.
 286		 */
 287		if (bvprvp && bvec_gap_to_prev(lim, bvprvp, bv.bv_offset))
 288			goto split;
 289
 290		if (nsegs < lim->max_segments &&
 291		    bytes + bv.bv_len <= max_bytes &&
 292		    bv.bv_offset + bv.bv_len <= PAGE_SIZE) {
 293			nsegs++;
 294			bytes += bv.bv_len;
 295		} else {
 296			if (bvec_split_segs(lim, &bv, &nsegs, &bytes,
 297					lim->max_segments, max_bytes))
 
 
 
 298				goto split;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 299		}
 
 
 
 300
 
 301		bvprv = bv;
 302		bvprvp = &bvprv;
 303	}
 
 304
 305	*segs = nsegs;
 306	return NULL;
 307split:
 308	/*
 309	 * We can't sanely support splitting for a REQ_NOWAIT bio. End it
 310	 * with EAGAIN if splitting is required and return an error pointer.
 311	 */
 312	if (bio->bi_opf & REQ_NOWAIT) {
 313		bio->bi_status = BLK_STS_AGAIN;
 314		bio_endio(bio);
 315		return ERR_PTR(-EAGAIN);
 316	}
 317
 
 
 318	*segs = nsegs;
 319
 320	/*
 321	 * Individual bvecs might not be logical block aligned. Round down the
 322	 * split size so that each bio is properly block size aligned, even if
 323	 * we do not use the full hardware limits.
 324	 */
 325	bytes = ALIGN_DOWN(bytes, lim->logical_block_size);
 326
 327	/*
 328	 * Bio splitting may cause subtle trouble such as hang when doing sync
 329	 * iopoll in direct IO routine. Given performance gain of iopoll for
 330	 * big IO can be trival, disable iopoll when split needed.
 331	 */
 332	bio_clear_polled(bio);
 333	return bio_split(bio, bytes >> SECTOR_SHIFT, GFP_NOIO, bs);
 334}
 335EXPORT_SYMBOL_GPL(bio_split_rw);
 336
 337/**
 338 * __bio_split_to_limits - split a bio to fit the queue limits
 339 * @bio:     bio to be split
 340 * @lim:     queue limits to split based on
 341 * @nr_segs: returns the number of segments in the returned bio
 342 *
 343 * Check if @bio needs splitting based on the queue limits, and if so split off
 344 * a bio fitting the limits from the beginning of @bio and return it.  @bio is
 345 * shortened to the remainder and re-submitted.
 346 *
 347 * The split bio is allocated from @q->bio_split, which is provided by the
 348 * block layer.
 349 */
 350struct bio *__bio_split_to_limits(struct bio *bio,
 351				  const struct queue_limits *lim,
 352				  unsigned int *nr_segs)
 353{
 354	struct bio_set *bs = &bio->bi_bdev->bd_disk->bio_split;
 355	struct bio *split;
 356
 357	switch (bio_op(bio)) {
 358	case REQ_OP_DISCARD:
 359	case REQ_OP_SECURE_ERASE:
 360		split = bio_split_discard(bio, lim, nr_segs, bs);
 361		break;
 362	case REQ_OP_WRITE_ZEROES:
 363		split = bio_split_write_zeroes(bio, lim, nr_segs, bs);
 364		break;
 365	default:
 366		split = bio_split_rw(bio, lim, nr_segs, bs,
 367				get_max_io_size(bio, lim) << SECTOR_SHIFT);
 368		if (IS_ERR(split))
 369			return NULL;
 370		break;
 371	}
 372
 373	if (split) {
 374		/* there isn't chance to merge the split bio */
 375		split->bi_opf |= REQ_NOMERGE;
 376
 377		blkcg_bio_issue_init(split);
 378		bio_chain(split, bio);
 379		trace_block_split(split, bio->bi_iter.bi_sector);
 380		submit_bio_noacct(bio);
 381		return split;
 382	}
 383	return bio;
 384}
 
 385
 386/**
 387 * bio_split_to_limits - split a bio to fit the queue limits
 388 * @bio:     bio to be split
 389 *
 390 * Check if @bio needs splitting based on the queue limits of @bio->bi_bdev, and
 391 * if so split off a bio fitting the limits from the beginning of @bio and
 392 * return it.  @bio is shortened to the remainder and re-submitted.
 393 *
 394 * The split bio is allocated from @q->bio_split, which is provided by the
 395 * block layer.
 396 */
 397struct bio *bio_split_to_limits(struct bio *bio)
 398{
 399	const struct queue_limits *lim = &bdev_get_queue(bio->bi_bdev)->limits;
 400	unsigned int nr_segs;
 
 
 
 401
 402	if (bio_may_exceed_limits(bio, lim))
 403		return __bio_split_to_limits(bio, lim, &nr_segs);
 404	return bio;
 405}
 406EXPORT_SYMBOL(bio_split_to_limits);
 407
 408unsigned int blk_recalc_rq_segments(struct request *rq)
 409{
 410	unsigned int nr_phys_segs = 0;
 411	unsigned int bytes = 0;
 412	struct req_iterator iter;
 413	struct bio_vec bv;
 414
 415	if (!rq->bio)
 416		return 0;
 417
 418	switch (bio_op(rq->bio)) {
 419	case REQ_OP_DISCARD:
 420	case REQ_OP_SECURE_ERASE:
 421		if (queue_max_discard_segments(rq->q) > 1) {
 422			struct bio *bio = rq->bio;
 
 
 
 
 
 
 
 423
 424			for_each_bio(bio)
 425				nr_phys_segs++;
 426			return nr_phys_segs;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 427		}
 428		return 1;
 429	case REQ_OP_WRITE_ZEROES:
 430		return 0;
 431	default:
 432		break;
 433	}
 434
 435	rq_for_each_bvec(bv, rq, iter)
 436		bvec_split_segs(&rq->q->limits, &bv, &nr_phys_segs, &bytes,
 437				UINT_MAX, UINT_MAX);
 
 
 438	return nr_phys_segs;
 439}
 440
 441static inline struct scatterlist *blk_next_sg(struct scatterlist **sg,
 442		struct scatterlist *sglist)
 443{
 444	if (!*sg)
 445		return sglist;
 446
 447	/*
 448	 * If the driver previously mapped a shorter list, we could see a
 449	 * termination bit prematurely unless it fully inits the sg table
 450	 * on each mapping. We KNOW that there must be more entries here
 451	 * or the driver would be buggy, so force clear the termination bit
 452	 * to avoid doing a full sg_init_table() in drivers for each command.
 453	 */
 454	sg_unmark_end(*sg);
 455	return sg_next(*sg);
 456}
 457
 458static unsigned blk_bvec_map_sg(struct request_queue *q,
 459		struct bio_vec *bvec, struct scatterlist *sglist,
 460		struct scatterlist **sg)
 461{
 462	unsigned nbytes = bvec->bv_len;
 463	unsigned nsegs = 0, total = 0;
 464
 465	while (nbytes > 0) {
 466		unsigned offset = bvec->bv_offset + total;
 467		unsigned len = min(get_max_segment_size(&q->limits,
 468				   bvec->bv_page, offset), nbytes);
 469		struct page *page = bvec->bv_page;
 470
 471		/*
 472		 * Unfortunately a fair number of drivers barf on scatterlists
 473		 * that have an offset larger than PAGE_SIZE, despite other
 474		 * subsystems dealing with that invariant just fine.  For now
 475		 * stick to the legacy format where we never present those from
 476		 * the block layer, but the code below should be removed once
 477		 * these offenders (mostly MMC/SD drivers) are fixed.
 478		 */
 479		page += (offset >> PAGE_SHIFT);
 480		offset &= ~PAGE_MASK;
 481
 482		*sg = blk_next_sg(sg, sglist);
 483		sg_set_page(*sg, page, len, offset);
 
 
 
 484
 485		total += len;
 486		nbytes -= len;
 487		nsegs++;
 488	}
 489
 490	return nsegs;
 491}
 
 492
 493static inline int __blk_bvec_map_sg(struct bio_vec bv,
 494		struct scatterlist *sglist, struct scatterlist **sg)
 495{
 496	*sg = blk_next_sg(sg, sglist);
 497	sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
 498	return 1;
 499}
 500
 501/* only try to merge bvecs into one sg if they are from two bios */
 502static inline bool
 503__blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec,
 504			   struct bio_vec *bvprv, struct scatterlist **sg)
 505{
 506
 507	int nbytes = bvec->bv_len;
 
 
 508
 509	if (!*sg)
 510		return false;
 511
 512	if ((*sg)->length + nbytes > queue_max_segment_size(q))
 513		return false;
 514
 515	if (!biovec_phys_mergeable(q, bvprv, bvec))
 516		return false;
 517
 518	(*sg)->length += nbytes;
 
 
 
 
 
 519
 520	return true;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 521}
 522
 523static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
 524			     struct scatterlist *sglist,
 525			     struct scatterlist **sg)
 526{
 527	struct bio_vec bvec, bvprv = { NULL };
 528	struct bvec_iter iter;
 529	int nsegs = 0;
 530	bool new_bio = false;
 531
 532	for_each_bio(bio) {
 533		bio_for_each_bvec(bvec, bio, iter) {
 534			/*
 535			 * Only try to merge bvecs from two bios given we
 536			 * have done bio internal merge when adding pages
 537			 * to bio
 538			 */
 539			if (new_bio &&
 540			    __blk_segment_map_sg_merge(q, &bvec, &bvprv, sg))
 541				goto next_bvec;
 542
 543			if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE)
 544				nsegs += __blk_bvec_map_sg(bvec, sglist, sg);
 545			else
 546				nsegs += blk_bvec_map_sg(q, &bvec, sglist, sg);
 547 next_bvec:
 548			new_bio = false;
 549		}
 550		if (likely(bio->bi_iter.bi_size)) {
 551			bvprv = bvec;
 552			new_bio = true;
 553		}
 554	}
 555
 
 
 
 
 
 
 
 
 
 
 
 
 
 556	return nsegs;
 557}
 558
 559/*
 560 * map a request to scatterlist, return number of sg entries setup. Caller
 561 * must make sure sg can hold rq->nr_phys_segments entries
 562 */
 563int __blk_rq_map_sg(struct request_queue *q, struct request *rq,
 564		struct scatterlist *sglist, struct scatterlist **last_sg)
 565{
 
 566	int nsegs = 0;
 567
 568	if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
 569		nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, last_sg);
 570	else if (rq->bio)
 571		nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 572
 573	if (*last_sg)
 574		sg_mark_end(*last_sg);
 575
 576	/*
 577	 * Something must have been wrong if the figured number of
 578	 * segment is bigger than number of req's physical segments
 579	 */
 580	WARN_ON(nsegs > blk_rq_nr_phys_segments(rq));
 581
 582	return nsegs;
 583}
 584EXPORT_SYMBOL(__blk_rq_map_sg);
 585
 586static inline unsigned int blk_rq_get_max_sectors(struct request *rq,
 587						  sector_t offset)
 588{
 589	struct request_queue *q = rq->q;
 590	unsigned int max_sectors;
 591
 592	if (blk_rq_is_passthrough(rq))
 593		return q->limits.max_hw_sectors;
 594
 595	max_sectors = blk_queue_get_max_sectors(q, req_op(rq));
 596	if (!q->limits.chunk_sectors ||
 597	    req_op(rq) == REQ_OP_DISCARD ||
 598	    req_op(rq) == REQ_OP_SECURE_ERASE)
 599		return max_sectors;
 600	return min(max_sectors,
 601		   blk_chunk_sectors_left(offset, q->limits.chunk_sectors));
 602}
 603
 604static inline int ll_new_hw_segment(struct request *req, struct bio *bio,
 605		unsigned int nr_phys_segs)
 
 606{
 607	if (!blk_cgroup_mergeable(req, bio))
 608		goto no_merge;
 609
 610	if (blk_integrity_merge_bio(req->q, req, bio) == false)
 611		goto no_merge;
 612
 613	/* discard request merge won't add new segment */
 614	if (req_op(req) == REQ_OP_DISCARD)
 615		return 1;
 616
 617	if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req))
 618		goto no_merge;
 619
 620	/*
 621	 * This will form the start of a new hw segment.  Bump both
 622	 * counters.
 623	 */
 624	req->nr_phys_segments += nr_phys_segs;
 625	return 1;
 626
 627no_merge:
 628	req_set_nomerge(req->q, req);
 
 
 629	return 0;
 630}
 631
 632int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs)
 
 633{
 634	if (req_gap_back_merge(req, bio))
 635		return 0;
 636	if (blk_integrity_rq(req) &&
 637	    integrity_req_gap_back_merge(req, bio))
 638		return 0;
 639	if (!bio_crypt_ctx_back_mergeable(req, bio))
 640		return 0;
 641	if (blk_rq_sectors(req) + bio_sectors(bio) >
 642	    blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
 643		req_set_nomerge(req->q, req);
 
 
 644		return 0;
 645	}
 
 
 
 
 646
 647	return ll_new_hw_segment(req, bio, nr_segs);
 648}
 649
 650static int ll_front_merge_fn(struct request *req, struct bio *bio,
 651		unsigned int nr_segs)
 652{
 
 653	if (req_gap_front_merge(req, bio))
 654		return 0;
 655	if (blk_integrity_rq(req) &&
 656	    integrity_req_gap_front_merge(req, bio))
 657		return 0;
 658	if (!bio_crypt_ctx_front_mergeable(req, bio))
 659		return 0;
 660	if (blk_rq_sectors(req) + bio_sectors(bio) >
 661	    blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
 662		req_set_nomerge(req->q, req);
 
 
 663		return 0;
 664	}
 
 
 
 
 665
 666	return ll_new_hw_segment(req, bio, nr_segs);
 667}
 668
 669static bool req_attempt_discard_merge(struct request_queue *q, struct request *req,
 670		struct request *next)
 
 
 
 671{
 672	unsigned short segments = blk_rq_nr_discard_segments(req);
 673
 674	if (segments >= queue_max_discard_segments(q))
 675		goto no_merge;
 676	if (blk_rq_sectors(req) + bio_sectors(next->bio) >
 677	    blk_rq_get_max_sectors(req, blk_rq_pos(req)))
 678		goto no_merge;
 679
 680	req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next);
 681	return true;
 682no_merge:
 683	req_set_nomerge(q, req);
 684	return false;
 685}
 686
 687static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
 688				struct request *next)
 689{
 690	int total_phys_segments;
 
 
 
 
 
 
 
 
 
 691
 692	if (req_gap_back_merge(req, next->bio))
 693		return 0;
 694
 695	/*
 696	 * Will it become too large?
 697	 */
 698	if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
 699	    blk_rq_get_max_sectors(req, blk_rq_pos(req)))
 700		return 0;
 701
 702	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
 703	if (total_phys_segments > blk_rq_get_max_segments(req))
 704		return 0;
 
 
 
 
 
 705
 706	if (!blk_cgroup_mergeable(req, next->bio))
 707		return 0;
 708
 709	if (blk_integrity_merge_rq(q, req, next) == false)
 710		return 0;
 711
 712	if (!bio_crypt_ctx_merge_rq(req, next))
 713		return 0;
 714
 715	/* Merge is OK... */
 716	req->nr_phys_segments = total_phys_segments;
 717	return 1;
 718}
 719
 720/**
 721 * blk_rq_set_mixed_merge - mark a request as mixed merge
 722 * @rq: request to mark as mixed merge
 723 *
 724 * Description:
 725 *     @rq is about to be mixed merged.  Make sure the attributes
 726 *     which can be mixed are set in each bio and mark @rq as mixed
 727 *     merged.
 728 */
 729static void blk_rq_set_mixed_merge(struct request *rq)
 730{
 731	blk_opf_t ff = rq->cmd_flags & REQ_FAILFAST_MASK;
 732	struct bio *bio;
 733
 734	if (rq->rq_flags & RQF_MIXED_MERGE)
 735		return;
 736
 737	/*
 738	 * @rq will no longer represent mixable attributes for all the
 739	 * contained bios.  It will just track those of the first one.
 740	 * Distributes the attributs to each bio.
 741	 */
 742	for (bio = rq->bio; bio; bio = bio->bi_next) {
 743		WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) &&
 744			     (bio->bi_opf & REQ_FAILFAST_MASK) != ff);
 745		bio->bi_opf |= ff;
 746	}
 747	rq->rq_flags |= RQF_MIXED_MERGE;
 748}
 749
 750static inline blk_opf_t bio_failfast(const struct bio *bio)
 751{
 752	if (bio->bi_opf & REQ_RAHEAD)
 753		return REQ_FAILFAST_MASK;
 
 754
 755	return bio->bi_opf & REQ_FAILFAST_MASK;
 756}
 757
 758/*
 759 * After we are marked as MIXED_MERGE, any new RA bio has to be updated
 760 * as failfast, and request's failfast has to be updated in case of
 761 * front merge.
 762 */
 763static inline void blk_update_mixed_merge(struct request *req,
 764		struct bio *bio, bool front_merge)
 765{
 766	if (req->rq_flags & RQF_MIXED_MERGE) {
 767		if (bio->bi_opf & REQ_RAHEAD)
 768			bio->bi_opf |= REQ_FAILFAST_MASK;
 769
 770		if (front_merge) {
 771			req->cmd_flags &= ~REQ_FAILFAST_MASK;
 772			req->cmd_flags |= bio->bi_opf & REQ_FAILFAST_MASK;
 773		}
 774	}
 775}
 776
 777static void blk_account_io_merge_request(struct request *req)
 778{
 779	if (blk_do_io_stat(req)) {
 780		part_stat_lock();
 781		part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
 782		part_stat_local_dec(req->part,
 783				    in_flight[op_is_write(req_op(req))]);
 784		part_stat_unlock();
 785	}
 786}
 787
 788static enum elv_merge blk_try_req_merge(struct request *req,
 789					struct request *next)
 790{
 791	if (blk_discard_mergable(req))
 792		return ELEVATOR_DISCARD_MERGE;
 793	else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next))
 794		return ELEVATOR_BACK_MERGE;
 795
 796	return ELEVATOR_NO_MERGE;
 797}
 798
 799/*
 800 * For non-mq, this has to be called with the request spinlock acquired.
 801 * For mq with scheduling, the appropriate queue wide lock should be held.
 802 */
 803static struct request *attempt_merge(struct request_queue *q,
 804				     struct request *req, struct request *next)
 805{
 806	if (!rq_mergeable(req) || !rq_mergeable(next))
 807		return NULL;
 808
 809	if (req_op(req) != req_op(next))
 810		return NULL;
 811
 812	if (rq_data_dir(req) != rq_data_dir(next))
 813		return NULL;
 
 
 
 814
 815	/* Don't merge requests with different write hints. */
 816	if (req->write_hint != next->write_hint)
 817		return NULL;
 
 818
 819	if (req->ioprio != next->ioprio)
 820		return NULL;
 
 821
 822	/*
 823	 * If we are allowed to merge, then append bio list
 824	 * from next to rq and release next. merge_requests_fn
 825	 * will have updated segment counts, update sector
 826	 * counts here. Handle DISCARDs separately, as they
 827	 * have separate settings.
 828	 */
 829
 830	switch (blk_try_req_merge(req, next)) {
 831	case ELEVATOR_DISCARD_MERGE:
 832		if (!req_attempt_discard_merge(q, req, next))
 833			return NULL;
 834		break;
 835	case ELEVATOR_BACK_MERGE:
 836		if (!ll_merge_requests_fn(q, req, next))
 837			return NULL;
 838		break;
 839	default:
 840		return NULL;
 841	}
 842
 843	/*
 844	 * If failfast settings disagree or any of the two is already
 845	 * a mixed merge, mark both as mixed before proceeding.  This
 846	 * makes sure that all involved bios have mixable attributes
 847	 * set properly.
 848	 */
 849	if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) ||
 850	    (req->cmd_flags & REQ_FAILFAST_MASK) !=
 851	    (next->cmd_flags & REQ_FAILFAST_MASK)) {
 852		blk_rq_set_mixed_merge(req);
 853		blk_rq_set_mixed_merge(next);
 854	}
 855
 856	/*
 857	 * At this point we have either done a back merge or front merge. We
 858	 * need the smaller start_time_ns of the merged requests to be the
 859	 * current request for accounting purposes.
 
 860	 */
 861	if (next->start_time_ns < req->start_time_ns)
 862		req->start_time_ns = next->start_time_ns;
 863
 864	req->biotail->bi_next = next->bio;
 865	req->biotail = next->biotail;
 866
 867	req->__data_len += blk_rq_bytes(next);
 868
 869	if (!blk_discard_mergable(req))
 870		elv_merge_requests(q, req, next);
 871
 872	blk_crypto_rq_put_keyslot(next);
 873
 874	/*
 875	 * 'next' is going away, so update stats accordingly
 876	 */
 877	blk_account_io_merge_request(next);
 878
 879	trace_block_rq_merge(next);
 
 
 880
 881	/*
 882	 * ownership of bio passed from next to req, return 'next' for
 883	 * the caller to free
 884	 */
 885	next->bio = NULL;
 886	return next;
 
 887}
 888
 889static struct request *attempt_back_merge(struct request_queue *q,
 890		struct request *rq)
 891{
 892	struct request *next = elv_latter_request(q, rq);
 893
 894	if (next)
 895		return attempt_merge(q, rq, next);
 896
 897	return NULL;
 898}
 899
 900static struct request *attempt_front_merge(struct request_queue *q,
 901		struct request *rq)
 902{
 903	struct request *prev = elv_former_request(q, rq);
 904
 905	if (prev)
 906		return attempt_merge(q, prev, rq);
 907
 908	return NULL;
 909}
 910
 911/*
 912 * Try to merge 'next' into 'rq'. Return true if the merge happened, false
 913 * otherwise. The caller is responsible for freeing 'next' if the merge
 914 * happened.
 915 */
 916bool blk_attempt_req_merge(struct request_queue *q, struct request *rq,
 917			   struct request *next)
 918{
 919	return attempt_merge(q, rq, next);
 920}
 921
 922bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 923{
 924	if (!rq_mergeable(rq) || !bio_mergeable(bio))
 925		return false;
 926
 927	if (req_op(rq) != bio_op(bio))
 928		return false;
 929
 930	/* different data direction or already started, don't merge */
 931	if (bio_data_dir(bio) != rq_data_dir(rq))
 932		return false;
 933
 934	/* don't merge across cgroup boundaries */
 935	if (!blk_cgroup_mergeable(rq, bio))
 936		return false;
 937
 938	/* only merge integrity protected bio into ditto rq */
 939	if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
 940		return false;
 941
 942	/* Only merge if the crypt contexts are compatible */
 943	if (!bio_crypt_rq_ctx_compatible(rq, bio))
 944		return false;
 945
 946	/* Don't merge requests with different write hints. */
 947	if (rq->write_hint != bio->bi_write_hint)
 948		return false;
 949
 950	if (rq->ioprio != bio_prio(bio))
 951		return false;
 952
 953	return true;
 954}
 955
 956enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
 957{
 958	if (blk_discard_mergable(rq))
 959		return ELEVATOR_DISCARD_MERGE;
 960	else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
 961		return ELEVATOR_BACK_MERGE;
 962	else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
 963		return ELEVATOR_FRONT_MERGE;
 964	return ELEVATOR_NO_MERGE;
 965}
 966
 967static void blk_account_io_merge_bio(struct request *req)
 968{
 969	if (!blk_do_io_stat(req))
 970		return;
 971
 972	part_stat_lock();
 973	part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
 974	part_stat_unlock();
 975}
 976
 977enum bio_merge_status {
 978	BIO_MERGE_OK,
 979	BIO_MERGE_NONE,
 980	BIO_MERGE_FAILED,
 981};
 982
 983static enum bio_merge_status bio_attempt_back_merge(struct request *req,
 984		struct bio *bio, unsigned int nr_segs)
 985{
 986	const blk_opf_t ff = bio_failfast(bio);
 987
 988	if (!ll_back_merge_fn(req, bio, nr_segs))
 989		return BIO_MERGE_FAILED;
 990
 991	trace_block_bio_backmerge(bio);
 992	rq_qos_merge(req->q, req, bio);
 993
 994	if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
 995		blk_rq_set_mixed_merge(req);
 996
 997	blk_update_mixed_merge(req, bio, false);
 998
 999	req->biotail->bi_next = bio;
1000	req->biotail = bio;
1001	req->__data_len += bio->bi_iter.bi_size;
1002
1003	bio_crypt_free_ctx(bio);
1004
1005	blk_account_io_merge_bio(req);
1006	return BIO_MERGE_OK;
1007}
1008
1009static enum bio_merge_status bio_attempt_front_merge(struct request *req,
1010		struct bio *bio, unsigned int nr_segs)
1011{
1012	const blk_opf_t ff = bio_failfast(bio);
1013
1014	if (!ll_front_merge_fn(req, bio, nr_segs))
1015		return BIO_MERGE_FAILED;
1016
1017	trace_block_bio_frontmerge(bio);
1018	rq_qos_merge(req->q, req, bio);
1019
1020	if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1021		blk_rq_set_mixed_merge(req);
1022
1023	blk_update_mixed_merge(req, bio, true);
1024
1025	bio->bi_next = req->bio;
1026	req->bio = bio;
1027
1028	req->__sector = bio->bi_iter.bi_sector;
1029	req->__data_len += bio->bi_iter.bi_size;
1030
1031	bio_crypt_do_front_merge(req, bio);
1032
1033	blk_account_io_merge_bio(req);
1034	return BIO_MERGE_OK;
1035}
1036
1037static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q,
1038		struct request *req, struct bio *bio)
1039{
1040	unsigned short segments = blk_rq_nr_discard_segments(req);
1041
1042	if (segments >= queue_max_discard_segments(q))
1043		goto no_merge;
1044	if (blk_rq_sectors(req) + bio_sectors(bio) >
1045	    blk_rq_get_max_sectors(req, blk_rq_pos(req)))
1046		goto no_merge;
1047
1048	rq_qos_merge(q, req, bio);
1049
1050	req->biotail->bi_next = bio;
1051	req->biotail = bio;
1052	req->__data_len += bio->bi_iter.bi_size;
1053	req->nr_phys_segments = segments + 1;
1054
1055	blk_account_io_merge_bio(req);
1056	return BIO_MERGE_OK;
1057no_merge:
1058	req_set_nomerge(q, req);
1059	return BIO_MERGE_FAILED;
1060}
1061
1062static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
1063						   struct request *rq,
1064						   struct bio *bio,
1065						   unsigned int nr_segs,
1066						   bool sched_allow_merge)
1067{
1068	if (!blk_rq_merge_ok(rq, bio))
1069		return BIO_MERGE_NONE;
1070
1071	switch (blk_try_merge(rq, bio)) {
1072	case ELEVATOR_BACK_MERGE:
1073		if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio))
1074			return bio_attempt_back_merge(rq, bio, nr_segs);
1075		break;
1076	case ELEVATOR_FRONT_MERGE:
1077		if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio))
1078			return bio_attempt_front_merge(rq, bio, nr_segs);
1079		break;
1080	case ELEVATOR_DISCARD_MERGE:
1081		return bio_attempt_discard_merge(q, rq, bio);
1082	default:
1083		return BIO_MERGE_NONE;
1084	}
1085
1086	return BIO_MERGE_FAILED;
1087}
1088
1089/**
1090 * blk_attempt_plug_merge - try to merge with %current's plugged list
1091 * @q: request_queue new bio is being queued at
1092 * @bio: new bio being queued
1093 * @nr_segs: number of segments in @bio
1094 * from the passed in @q already in the plug list
1095 *
1096 * Determine whether @bio being queued on @q can be merged with the previous
1097 * request on %current's plugged list.  Returns %true if merge was successful,
1098 * otherwise %false.
1099 *
1100 * Plugging coalesces IOs from the same issuer for the same purpose without
1101 * going through @q->queue_lock.  As such it's more of an issuing mechanism
1102 * than scheduling, and the request, while may have elvpriv data, is not
1103 * added on the elevator at this point.  In addition, we don't have
1104 * reliable access to the elevator outside queue lock.  Only check basic
1105 * merging parameters without querying the elevator.
1106 *
1107 * Caller must ensure !blk_queue_nomerges(q) beforehand.
1108 */
1109bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
1110		unsigned int nr_segs)
1111{
1112	struct blk_plug *plug;
1113	struct request *rq;
1114
1115	plug = blk_mq_plug(bio);
1116	if (!plug || rq_list_empty(plug->mq_list))
1117		return false;
1118
1119	rq_list_for_each(&plug->mq_list, rq) {
1120		if (rq->q == q) {
1121			if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) ==
1122			    BIO_MERGE_OK)
1123				return true;
1124			break;
1125		}
1126
1127		/*
1128		 * Only keep iterating plug list for merges if we have multiple
1129		 * queues
1130		 */
1131		if (!plug->multiple_queues)
1132			break;
1133	}
1134	return false;
1135}
1136
1137/*
1138 * Iterate list of requests and see if we can merge this bio with any
1139 * of them.
1140 */
1141bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
1142			struct bio *bio, unsigned int nr_segs)
1143{
1144	struct request *rq;
1145	int checked = 8;
1146
1147	list_for_each_entry_reverse(rq, list, queuelist) {
1148		if (!checked--)
1149			break;
1150
1151		switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) {
1152		case BIO_MERGE_NONE:
1153			continue;
1154		case BIO_MERGE_OK:
1155			return true;
1156		case BIO_MERGE_FAILED:
1157			return false;
1158		}
1159
1160	}
1161
1162	return false;
1163}
1164EXPORT_SYMBOL_GPL(blk_bio_list_merge);
1165
1166bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
1167		unsigned int nr_segs, struct request **merged_request)
1168{
1169	struct request *rq;
1170
1171	switch (elv_merge(q, &rq, bio)) {
1172	case ELEVATOR_BACK_MERGE:
1173		if (!blk_mq_sched_allow_merge(q, rq, bio))
1174			return false;
1175		if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
1176			return false;
1177		*merged_request = attempt_back_merge(q, rq);
1178		if (!*merged_request)
1179			elv_merged_request(q, rq, ELEVATOR_BACK_MERGE);
1180		return true;
1181	case ELEVATOR_FRONT_MERGE:
1182		if (!blk_mq_sched_allow_merge(q, rq, bio))
1183			return false;
1184		if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
1185			return false;
1186		*merged_request = attempt_front_merge(q, rq);
1187		if (!*merged_request)
1188			elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
1189		return true;
1190	case ELEVATOR_DISCARD_MERGE:
1191		return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK;
1192	default:
1193		return false;
1194	}
1195}
1196EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
v4.6
 
  1/*
  2 * Functions related to segment and merge handling
  3 */
  4#include <linux/kernel.h>
  5#include <linux/module.h>
  6#include <linux/bio.h>
  7#include <linux/blkdev.h>
 
  8#include <linux/scatterlist.h>
 
 
  9
 10#include <trace/events/block.h>
 11
 12#include "blk.h"
 
 
 
 13
 14static struct bio *blk_bio_discard_split(struct request_queue *q,
 15					 struct bio *bio,
 16					 struct bio_set *bs,
 17					 unsigned *nsegs)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 18{
 19	unsigned int max_discard_sectors, granularity;
 20	int alignment;
 21	sector_t tmp;
 22	unsigned split_sectors;
 23
 24	*nsegs = 1;
 25
 26	/* Zero-sector (unknown) and one-sector granularities are the same.  */
 27	granularity = max(q->limits.discard_granularity >> 9, 1U);
 28
 29	max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
 
 30	max_discard_sectors -= max_discard_sectors % granularity;
 31
 32	if (unlikely(!max_discard_sectors)) {
 33		/* XXX: warn */
 34		return NULL;
 35	}
 36
 37	if (bio_sectors(bio) <= max_discard_sectors)
 38		return NULL;
 39
 40	split_sectors = max_discard_sectors;
 41
 42	/*
 43	 * If the next starting sector would be misaligned, stop the discard at
 44	 * the previous aligned sector.
 45	 */
 46	alignment = (q->limits.discard_alignment >> 9) % granularity;
 47
 48	tmp = bio->bi_iter.bi_sector + split_sectors - alignment;
 49	tmp = sector_div(tmp, granularity);
 50
 51	if (split_sectors > tmp)
 52		split_sectors -= tmp;
 53
 54	return bio_split(bio, split_sectors, GFP_NOIO, bs);
 55}
 56
 57static struct bio *blk_bio_write_same_split(struct request_queue *q,
 58					    struct bio *bio,
 59					    struct bio_set *bs,
 60					    unsigned *nsegs)
 61{
 62	*nsegs = 1;
 63
 64	if (!q->limits.max_write_same_sectors)
 
 65		return NULL;
 
 
 66
 67	if (bio_sectors(bio) <= q->limits.max_write_same_sectors)
 68		return NULL;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 69
 70	return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
 
 
 
 
 71}
 72
 73static inline unsigned get_max_io_size(struct request_queue *q,
 74				       struct bio *bio)
 
 
 
 
 
 
 
 
 75{
 76	unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);
 77	unsigned mask = queue_logical_block_size(q) - 1;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 78
 79	/* aligned to logical block size */
 80	sectors &= ~(mask >> 9);
 81
 82	return sectors;
 
 83}
 84
 85static struct bio *blk_bio_segment_split(struct request_queue *q,
 86					 struct bio *bio,
 87					 struct bio_set *bs,
 88					 unsigned *segs)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 89{
 90	struct bio_vec bv, bvprv, *bvprvp = NULL;
 91	struct bvec_iter iter;
 92	unsigned seg_size = 0, nsegs = 0, sectors = 0;
 93	unsigned front_seg_size = bio->bi_seg_front_size;
 94	bool do_split = true;
 95	struct bio *new = NULL;
 96	const unsigned max_sectors = get_max_io_size(q, bio);
 97
 98	bio_for_each_segment(bv, bio, iter) {
 99		/*
100		 * If the queue doesn't support SG gaps and adding this
101		 * offset would create a gap, disallow it.
102		 */
103		if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
104			goto split;
105
106		if (sectors + (bv.bv_len >> 9) > max_sectors) {
107			/*
108			 * Consider this a new segment if we're splitting in
109			 * the middle of this vector.
110			 */
111			if (nsegs < queue_max_segments(q) &&
112			    sectors < max_sectors) {
113				nsegs++;
114				sectors = max_sectors;
115			}
116			if (sectors)
117				goto split;
118			/* Make this single bvec as the 1st segment */
119		}
120
121		if (bvprvp && blk_queue_cluster(q)) {
122			if (seg_size + bv.bv_len > queue_max_segment_size(q))
123				goto new_segment;
124			if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv))
125				goto new_segment;
126			if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv))
127				goto new_segment;
128
129			seg_size += bv.bv_len;
130			bvprv = bv;
131			bvprvp = &bvprv;
132			sectors += bv.bv_len >> 9;
133
134			if (nsegs == 1 && seg_size > front_seg_size)
135				front_seg_size = seg_size;
136			continue;
137		}
138new_segment:
139		if (nsegs == queue_max_segments(q))
140			goto split;
141
142		nsegs++;
143		bvprv = bv;
144		bvprvp = &bvprv;
145		seg_size = bv.bv_len;
146		sectors += bv.bv_len >> 9;
147
148		if (nsegs == 1 && seg_size > front_seg_size)
149			front_seg_size = seg_size;
 
 
 
 
 
 
 
 
 
150	}
151
152	do_split = false;
153split:
154	*segs = nsegs;
155
156	if (do_split) {
157		new = bio_split(bio, sectors, GFP_NOIO, bs);
158		if (new)
159			bio = new;
160	}
 
161
162	bio->bi_seg_front_size = front_seg_size;
163	if (seg_size > bio->bi_seg_back_size)
164		bio->bi_seg_back_size = seg_size;
165
166	return do_split ? new : NULL;
 
 
167}
 
168
169void blk_queue_split(struct request_queue *q, struct bio **bio,
170		     struct bio_set *bs)
171{
172	struct bio *split, *res;
173	unsigned nsegs;
174
175	if ((*bio)->bi_rw & REQ_DISCARD)
176		split = blk_bio_discard_split(q, *bio, bs, &nsegs);
177	else if ((*bio)->bi_rw & REQ_WRITE_SAME)
178		split = blk_bio_write_same_split(q, *bio, bs, &nsegs);
179	else
180		split = blk_bio_segment_split(q, *bio, q->bio_split, &nsegs);
181
182	/* physical segments can be figured out during splitting */
183	res = split ? split : *bio;
184	res->bi_phys_segments = nsegs;
185	bio_set_flag(res, BIO_SEG_VALID);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
186
187	if (split) {
188		/* there isn't chance to merge the splitted bio */
189		split->bi_rw |= REQ_NOMERGE;
190
191		bio_chain(split, *bio);
192		trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
193		generic_make_request(*bio);
194		*bio = split;
 
195	}
 
196}
197EXPORT_SYMBOL(blk_queue_split);
198
199static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
200					     struct bio *bio,
201					     bool no_sg_merge)
 
 
 
 
 
 
 
 
 
202{
203	struct bio_vec bv, bvprv = { NULL };
204	int cluster, prev = 0;
205	unsigned int seg_size, nr_phys_segs;
206	struct bio *fbio, *bbio;
207	struct bvec_iter iter;
208
209	if (!bio)
210		return 0;
 
 
 
211
212	/*
213	 * This should probably be returning 0, but blk_add_request_payload()
214	 * (Christoph!!!!)
215	 */
216	if (bio->bi_rw & REQ_DISCARD)
217		return 1;
218
219	if (bio->bi_rw & REQ_WRITE_SAME)
220		return 1;
221
222	fbio = bio;
223	cluster = blk_queue_cluster(q);
224	seg_size = 0;
225	nr_phys_segs = 0;
226	for_each_bio(bio) {
227		bio_for_each_segment(bv, bio, iter) {
228			/*
229			 * If SG merging is disabled, each bio vector is
230			 * a segment
231			 */
232			if (no_sg_merge)
233				goto new_segment;
234
235			if (prev && cluster) {
236				if (seg_size + bv.bv_len
237				    > queue_max_segment_size(q))
238					goto new_segment;
239				if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv))
240					goto new_segment;
241				if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv))
242					goto new_segment;
243
244				seg_size += bv.bv_len;
245				bvprv = bv;
246				continue;
247			}
248new_segment:
249			if (nr_phys_segs == 1 && seg_size >
250			    fbio->bi_seg_front_size)
251				fbio->bi_seg_front_size = seg_size;
252
253			nr_phys_segs++;
254			bvprv = bv;
255			prev = 1;
256			seg_size = bv.bv_len;
257		}
258		bbio = bio;
 
 
 
 
259	}
260
261	if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
262		fbio->bi_seg_front_size = seg_size;
263	if (seg_size > bbio->bi_seg_back_size)
264		bbio->bi_seg_back_size = seg_size;
265
266	return nr_phys_segs;
267}
268
269void blk_recalc_rq_segments(struct request *rq)
 
270{
271	bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
272			&rq->q->queue_flags);
273
274	rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio,
275			no_sg_merge);
 
 
 
 
 
 
 
276}
277
278void blk_recount_segments(struct request_queue *q, struct bio *bio)
279{
280	unsigned short seg_cnt;
 
 
 
 
 
 
 
 
 
281
282	/* estimate segment number by bi_vcnt for non-cloned bio */
283	if (bio_flagged(bio, BIO_CLONED))
284		seg_cnt = bio_segments(bio);
285	else
286		seg_cnt = bio->bi_vcnt;
 
 
 
 
 
287
288	if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
289			(seg_cnt < queue_max_segments(q)))
290		bio->bi_phys_segments = seg_cnt;
291	else {
292		struct bio *nxt = bio->bi_next;
293
294		bio->bi_next = NULL;
295		bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
296		bio->bi_next = nxt;
297	}
298
299	bio_set_flag(bio, BIO_SEG_VALID);
300}
301EXPORT_SYMBOL(blk_recount_segments);
302
303static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
304				   struct bio *nxt)
305{
306	struct bio_vec end_bv = { NULL }, nxt_bv;
 
 
 
307
308	if (!blk_queue_cluster(q))
309		return 0;
 
 
 
310
311	if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
312	    queue_max_segment_size(q))
313		return 0;
314
315	if (!bio_has_data(bio))
316		return 1;
317
318	bio_get_last_bvec(bio, &end_bv);
319	bio_get_first_bvec(nxt, &nxt_bv);
320
321	if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv))
322		return 0;
323
324	/*
325	 * bio and nxt are contiguous in memory; check if the queue allows
326	 * these two to be merged into one
327	 */
328	if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv))
329		return 1;
330
331	return 0;
332}
333
334static inline void
335__blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
336		     struct scatterlist *sglist, struct bio_vec *bvprv,
337		     struct scatterlist **sg, int *nsegs, int *cluster)
338{
339
340	int nbytes = bvec->bv_len;
341
342	if (*sg && *cluster) {
343		if ((*sg)->length + nbytes > queue_max_segment_size(q))
344			goto new_segment;
345
346		if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
347			goto new_segment;
348		if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
349			goto new_segment;
350
351		(*sg)->length += nbytes;
352	} else {
353new_segment:
354		if (!*sg)
355			*sg = sglist;
356		else {
357			/*
358			 * If the driver previously mapped a shorter
359			 * list, we could see a termination bit
360			 * prematurely unless it fully inits the sg
361			 * table on each mapping. We KNOW that there
362			 * must be more entries here or the driver
363			 * would be buggy, so force clear the
364			 * termination bit to avoid doing a full
365			 * sg_init_table() in drivers for each command.
366			 */
367			sg_unmark_end(*sg);
368			*sg = sg_next(*sg);
369		}
370
371		sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
372		(*nsegs)++;
373	}
374	*bvprv = *bvec;
375}
376
377static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
378			     struct scatterlist *sglist,
379			     struct scatterlist **sg)
380{
381	struct bio_vec bvec, bvprv = { NULL };
382	struct bvec_iter iter;
383	int nsegs, cluster;
 
384
385	nsegs = 0;
386	cluster = blk_queue_cluster(q);
387
388	if (bio->bi_rw & REQ_DISCARD) {
389		/*
390		 * This is a hack - drivers should be neither modifying the
391		 * biovec, nor relying on bi_vcnt - but because of
392		 * blk_add_request_payload(), a discard bio may or may not have
393		 * a payload we need to set up here (thank you Christoph) and
394		 * bi_vcnt is really the only way of telling if we need to.
395		 */
396
397		if (bio->bi_vcnt)
398			goto single_segment;
399
400		return 0;
 
 
 
 
 
 
401	}
402
403	if (bio->bi_rw & REQ_WRITE_SAME) {
404single_segment:
405		*sg = sglist;
406		bvec = bio_iovec(bio);
407		sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset);
408		return 1;
409	}
410
411	for_each_bio(bio)
412		bio_for_each_segment(bvec, bio, iter)
413			__blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
414					     &nsegs, &cluster);
415
416	return nsegs;
417}
418
419/*
420 * map a request to scatterlist, return number of sg entries setup. Caller
421 * must make sure sg can hold rq->nr_phys_segments entries
422 */
423int blk_rq_map_sg(struct request_queue *q, struct request *rq,
424		  struct scatterlist *sglist)
425{
426	struct scatterlist *sg = NULL;
427	int nsegs = 0;
428
429	if (rq->bio)
430		nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
431
432	if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
433	    (blk_rq_bytes(rq) & q->dma_pad_mask)) {
434		unsigned int pad_len =
435			(q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
436
437		sg->length += pad_len;
438		rq->extra_len += pad_len;
439	}
440
441	if (q->dma_drain_size && q->dma_drain_needed(rq)) {
442		if (rq->cmd_flags & REQ_WRITE)
443			memset(q->dma_drain_buffer, 0, q->dma_drain_size);
444
445		sg_unmark_end(sg);
446		sg = sg_next(sg);
447		sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
448			    q->dma_drain_size,
449			    ((unsigned long)q->dma_drain_buffer) &
450			    (PAGE_SIZE - 1));
451		nsegs++;
452		rq->extra_len += q->dma_drain_size;
453	}
454
455	if (sg)
456		sg_mark_end(sg);
457
458	/*
459	 * Something must have been wrong if the figured number of
460	 * segment is bigger than number of req's physical segments
461	 */
462	WARN_ON(nsegs > rq->nr_phys_segments);
463
464	return nsegs;
465}
466EXPORT_SYMBOL(blk_rq_map_sg);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
467
468static inline int ll_new_hw_segment(struct request_queue *q,
469				    struct request *req,
470				    struct bio *bio)
471{
472	int nr_phys_segs = bio_phys_segments(q, bio);
 
473
474	if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
475		goto no_merge;
476
477	if (blk_integrity_merge_bio(q, req, bio) == false)
 
 
 
 
478		goto no_merge;
479
480	/*
481	 * This will form the start of a new hw segment.  Bump both
482	 * counters.
483	 */
484	req->nr_phys_segments += nr_phys_segs;
485	return 1;
486
487no_merge:
488	req->cmd_flags |= REQ_NOMERGE;
489	if (req == q->last_merge)
490		q->last_merge = NULL;
491	return 0;
492}
493
494int ll_back_merge_fn(struct request_queue *q, struct request *req,
495		     struct bio *bio)
496{
497	if (req_gap_back_merge(req, bio))
498		return 0;
499	if (blk_integrity_rq(req) &&
500	    integrity_req_gap_back_merge(req, bio))
501		return 0;
 
 
502	if (blk_rq_sectors(req) + bio_sectors(bio) >
503	    blk_rq_get_max_sectors(req)) {
504		req->cmd_flags |= REQ_NOMERGE;
505		if (req == q->last_merge)
506			q->last_merge = NULL;
507		return 0;
508	}
509	if (!bio_flagged(req->biotail, BIO_SEG_VALID))
510		blk_recount_segments(q, req->biotail);
511	if (!bio_flagged(bio, BIO_SEG_VALID))
512		blk_recount_segments(q, bio);
513
514	return ll_new_hw_segment(q, req, bio);
515}
516
517int ll_front_merge_fn(struct request_queue *q, struct request *req,
518		      struct bio *bio)
519{
520
521	if (req_gap_front_merge(req, bio))
522		return 0;
523	if (blk_integrity_rq(req) &&
524	    integrity_req_gap_front_merge(req, bio))
525		return 0;
 
 
526	if (blk_rq_sectors(req) + bio_sectors(bio) >
527	    blk_rq_get_max_sectors(req)) {
528		req->cmd_flags |= REQ_NOMERGE;
529		if (req == q->last_merge)
530			q->last_merge = NULL;
531		return 0;
532	}
533	if (!bio_flagged(bio, BIO_SEG_VALID))
534		blk_recount_segments(q, bio);
535	if (!bio_flagged(req->bio, BIO_SEG_VALID))
536		blk_recount_segments(q, req->bio);
537
538	return ll_new_hw_segment(q, req, bio);
539}
540
541/*
542 * blk-mq uses req->special to carry normal driver per-request payload, it
543 * does not indicate a prepared command that we cannot merge with.
544 */
545static bool req_no_special_merge(struct request *req)
546{
547	struct request_queue *q = req->q;
548
549	return !q->mq_ops && req->special;
 
 
 
 
 
 
 
 
 
 
550}
551
552static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
553				struct request *next)
554{
555	int total_phys_segments;
556	unsigned int seg_size =
557		req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
558
559	/*
560	 * First check if the either of the requests are re-queued
561	 * requests.  Can't merge them if they are.
562	 */
563	if (req_no_special_merge(req) || req_no_special_merge(next))
564		return 0;
565
566	if (req_gap_back_merge(req, next->bio))
567		return 0;
568
569	/*
570	 * Will it become too large?
571	 */
572	if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
573	    blk_rq_get_max_sectors(req))
574		return 0;
575
576	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
577	if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
578		if (req->nr_phys_segments == 1)
579			req->bio->bi_seg_front_size = seg_size;
580		if (next->nr_phys_segments == 1)
581			next->biotail->bi_seg_back_size = seg_size;
582		total_phys_segments--;
583	}
584
585	if (total_phys_segments > queue_max_segments(q))
586		return 0;
587
588	if (blk_integrity_merge_rq(q, req, next) == false)
589		return 0;
590
 
 
 
591	/* Merge is OK... */
592	req->nr_phys_segments = total_phys_segments;
593	return 1;
594}
595
596/**
597 * blk_rq_set_mixed_merge - mark a request as mixed merge
598 * @rq: request to mark as mixed merge
599 *
600 * Description:
601 *     @rq is about to be mixed merged.  Make sure the attributes
602 *     which can be mixed are set in each bio and mark @rq as mixed
603 *     merged.
604 */
605void blk_rq_set_mixed_merge(struct request *rq)
606{
607	unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
608	struct bio *bio;
609
610	if (rq->cmd_flags & REQ_MIXED_MERGE)
611		return;
612
613	/*
614	 * @rq will no longer represent mixable attributes for all the
615	 * contained bios.  It will just track those of the first one.
616	 * Distributes the attributs to each bio.
617	 */
618	for (bio = rq->bio; bio; bio = bio->bi_next) {
619		WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
620			     (bio->bi_rw & REQ_FAILFAST_MASK) != ff);
621		bio->bi_rw |= ff;
622	}
623	rq->cmd_flags |= REQ_MIXED_MERGE;
624}
625
626static void blk_account_io_merge(struct request *req)
627{
628	if (blk_do_io_stat(req)) {
629		struct hd_struct *part;
630		int cpu;
631
632		cpu = part_stat_lock();
633		part = req->part;
634
635		part_round_stats(cpu, part);
636		part_dec_in_flight(part, rq_data_dir(req));
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
637
638		hd_struct_put(part);
 
 
 
 
 
 
639		part_stat_unlock();
640	}
641}
642
 
 
 
 
 
 
 
 
 
 
 
643/*
644 * Has to be called with the request spinlock acquired
 
645 */
646static int attempt_merge(struct request_queue *q, struct request *req,
647			  struct request *next)
648{
649	if (!rq_mergeable(req) || !rq_mergeable(next))
650		return 0;
651
652	if (!blk_check_merge_flags(req->cmd_flags, next->cmd_flags))
653		return 0;
654
655	/*
656	 * not contiguous
657	 */
658	if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
659		return 0;
660
661	if (rq_data_dir(req) != rq_data_dir(next)
662	    || req->rq_disk != next->rq_disk
663	    || req_no_special_merge(next))
664		return 0;
665
666	if (req->cmd_flags & REQ_WRITE_SAME &&
667	    !blk_write_same_mergeable(req->bio, next->bio))
668		return 0;
669
670	/*
671	 * If we are allowed to merge, then append bio list
672	 * from next to rq and release next. merge_requests_fn
673	 * will have updated segment counts, update sector
674	 * counts here.
 
675	 */
676	if (!ll_merge_requests_fn(q, req, next))
677		return 0;
 
 
 
 
 
 
 
 
 
 
 
678
679	/*
680	 * If failfast settings disagree or any of the two is already
681	 * a mixed merge, mark both as mixed before proceeding.  This
682	 * makes sure that all involved bios have mixable attributes
683	 * set properly.
684	 */
685	if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE ||
686	    (req->cmd_flags & REQ_FAILFAST_MASK) !=
687	    (next->cmd_flags & REQ_FAILFAST_MASK)) {
688		blk_rq_set_mixed_merge(req);
689		blk_rq_set_mixed_merge(next);
690	}
691
692	/*
693	 * At this point we have either done a back merge
694	 * or front merge. We need the smaller start_time of
695	 * the merged requests to be the current request
696	 * for accounting purposes.
697	 */
698	if (time_after(req->start_time, next->start_time))
699		req->start_time = next->start_time;
700
701	req->biotail->bi_next = next->bio;
702	req->biotail = next->biotail;
703
704	req->__data_len += blk_rq_bytes(next);
705
706	elv_merge_requests(q, req, next);
 
 
 
707
708	/*
709	 * 'next' is going away, so update stats accordingly
710	 */
711	blk_account_io_merge(next);
712
713	req->ioprio = ioprio_best(req->ioprio, next->ioprio);
714	if (blk_rq_cpu_valid(next))
715		req->cpu = next->cpu;
716
717	/* owner-ship of bio passed from next to req */
 
 
 
718	next->bio = NULL;
719	__blk_put_request(q, next);
720	return 1;
721}
722
723int attempt_back_merge(struct request_queue *q, struct request *rq)
 
724{
725	struct request *next = elv_latter_request(q, rq);
726
727	if (next)
728		return attempt_merge(q, rq, next);
729
730	return 0;
731}
732
733int attempt_front_merge(struct request_queue *q, struct request *rq)
 
734{
735	struct request *prev = elv_former_request(q, rq);
736
737	if (prev)
738		return attempt_merge(q, prev, rq);
739
740	return 0;
741}
742
743int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
744			  struct request *next)
 
 
 
 
 
745{
746	return attempt_merge(q, rq, next);
747}
748
749bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
750{
751	if (!rq_mergeable(rq) || !bio_mergeable(bio))
752		return false;
753
754	if (!blk_check_merge_flags(rq->cmd_flags, bio->bi_rw))
755		return false;
756
757	/* different data direction or already started, don't merge */
758	if (bio_data_dir(bio) != rq_data_dir(rq))
759		return false;
760
761	/* must be same device and not a special request */
762	if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq))
763		return false;
764
765	/* only merge integrity protected bio into ditto rq */
766	if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
767		return false;
768
769	/* must be using the same buffer */
770	if (rq->cmd_flags & REQ_WRITE_SAME &&
771	    !blk_write_same_mergeable(rq->bio, bio))
 
 
 
 
 
 
772		return false;
773
774	return true;
775}
776
777int blk_try_merge(struct request *rq, struct bio *bio)
778{
779	if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
 
 
780		return ELEVATOR_BACK_MERGE;
781	else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
782		return ELEVATOR_FRONT_MERGE;
783	return ELEVATOR_NO_MERGE;
784}