block/blk-merge.c

   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 "blk.h"
  11
  12 static struct bio *blk_bio_discard_split(struct request_queue *q,
  13                                          struct bio *bio,
  14                                          struct bio_set *bs,
  15                                          unsigned *nsegs)
  16 {
  17         unsigned int max_discard_sectors, granularity;
  18         int alignment;
  19         sector_t tmp;
  20         unsigned split_sectors;
  21
  22         *nsegs = 1;
  23
  24         /* Zero-sector (unknown) and one-sector granularities are the same.  */
  25         granularity = max(q->limits.discard_granularity >> 9, 1U);
  26
  27         max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
  28         max_discard_sectors -= max_discard_sectors % granularity;
  29
  30         if (unlikely(!max_discard_sectors)) {
  31                 /* XXX: warn */
  32                 return NULL;
  33         }
  34
  35         if (bio_sectors(bio) <= max_discard_sectors)
  36                 return NULL;
  37
  38         split_sectors = max_discard_sectors;
  39
  40         /*
  41          * If the next starting sector would be misaligned, stop the discard at
  42          * the previous aligned sector.
  43          */
  44         alignment = (q->limits.discard_alignment >> 9) % granularity;
  45
  46         tmp = bio->bi_iter.bi_sector + split_sectors - alignment;
  47         tmp = sector_div(tmp, granularity);
  48
  49         if (split_sectors > tmp)
  50                 split_sectors -= tmp;
  51
  52         return bio_split(bio, split_sectors, GFP_NOIO, bs);
  53 }
  54
  55 static struct bio *blk_bio_write_same_split(struct request_queue *q,
  56                                             struct bio *bio,
  57                                             struct bio_set *bs,
  58                                             unsigned *nsegs)
  59 {
  60         *nsegs = 1;
  61
  62         if (!q->limits.max_write_same_sectors)
  63                 return NULL;
  64
  65         if (bio_sectors(bio) <= q->limits.max_write_same_sectors)
  66                 return NULL;
  67
  68         return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
  69 }
  70
  71 static struct bio *blk_bio_segment_split(struct request_queue *q,
  72                                          struct bio *bio,
  73                                          struct bio_set *bs,
  74                                          unsigned *segs)
  75 {
  76         struct bio_vec bv, bvprv, *bvprvp = NULL;
  77         struct bvec_iter iter;
  78         unsigned seg_size = 0, nsegs = 0, sectors = 0;
  79
  80         bio_for_each_segment(bv, bio, iter) {
  81                 if (sectors + (bv.bv_len >> 9) > queue_max_sectors(q))
  82                         goto split;
  83
  84                 /*
  85                  * If the queue doesn't support SG gaps and adding this
  86                  * offset would create a gap, disallow it.
  87                  */
  88                 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
  89                         goto split;
  90
  91                 if (bvprvp && blk_queue_cluster(q)) {
  92                         if (seg_size + bv.bv_len > queue_max_segment_size(q))
  93                                 goto new_segment;
  94                         if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv))
  95                                 goto new_segment;
  96                         if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv))
  97                                 goto new_segment;
  98
  99                         seg_size += bv.bv_len;
 100                         bvprv = bv;
 101                         bvprvp = &bv;
 102                         sectors += bv.bv_len >> 9;
 103                         continue;
 104                 }
 105 new_segment:
 106                 if (nsegs == queue_max_segments(q))
 107                         goto split;
 108
 109                 nsegs++;
 110                 bvprv = bv;
 111                 bvprvp = &bv;
 112                 seg_size = bv.bv_len;
 113                 sectors += bv.bv_len >> 9;
 114         }
 115
 116         *segs = nsegs;
 117         return NULL;
 118 split:
 119         *segs = nsegs;
 120         return bio_split(bio, sectors, GFP_NOIO, bs);
 121 }
 122
 123 void blk_queue_split(struct request_queue *q, struct bio **bio,
 124                      struct bio_set *bs)
 125 {
 126         struct bio *split, *res;
 127         unsigned nsegs;
 128
 129         if ((*bio)->bi_rw & REQ_DISCARD)
 130                 split = blk_bio_discard_split(q, *bio, bs, &nsegs);
 131         else if ((*bio)->bi_rw & REQ_WRITE_SAME)
 132                 split = blk_bio_write_same_split(q, *bio, bs, &nsegs);
 133         else
 134                 split = blk_bio_segment_split(q, *bio, q->bio_split, &nsegs);
 135
 136         /* physical segments can be figured out during splitting */
 137         res = split ? split : *bio;
 138         res->bi_phys_segments = nsegs;
 139         bio_set_flag(res, BIO_SEG_VALID);
 140
 141         if (split) {
 142                 bio_chain(split, *bio);
 143                 generic_make_request(*bio);
 144                 *bio = split;
 145         }
 146 }
 147 EXPORT_SYMBOL(blk_queue_split);
 148
 149 static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
 150                                              struct bio *bio,
 151                                              bool no_sg_merge)
 152 {
 153         struct bio_vec bv, bvprv = { NULL };
 154         int cluster, prev = 0;
 155         unsigned int seg_size, nr_phys_segs;
 156         struct bio *fbio, *bbio;
 157         struct bvec_iter iter;
 158
 159         if (!bio)
 160                 return 0;
 161
 162         /*
 163          * This should probably be returning 0, but blk_add_request_payload()
 164          * (Christoph!!!!)
 165          */
 166         if (bio->bi_rw & REQ_DISCARD)
 167                 return 1;
 168
 169         if (bio->bi_rw & REQ_WRITE_SAME)
 170                 return 1;
 171
 172         fbio = bio;
 173         cluster = blk_queue_cluster(q);
 174         seg_size = 0;
 175         nr_phys_segs = 0;
 176         for_each_bio(bio) {
 177                 bio_for_each_segment(bv, bio, iter) {
 178                         /*
 179                          * If SG merging is disabled, each bio vector is
 180                          * a segment
 181                          */
 182                         if (no_sg_merge)
 183                                 goto new_segment;
 184
 185                         if (prev && cluster) {
 186                                 if (seg_size + bv.bv_len
 187                                     > queue_max_segment_size(q))
 188                                         goto new_segment;
 189                                 if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv))
 190                                         goto new_segment;
 191                                 if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv))
 192                                         goto new_segment;
 193
 194                                 seg_size += bv.bv_len;
 195                                 bvprv = bv;
 196                                 continue;
 197                         }
 198 new_segment:
 199                         if (nr_phys_segs == 1 && seg_size >
 200                             fbio->bi_seg_front_size)
 201                                 fbio->bi_seg_front_size = seg_size;
 202
 203                         nr_phys_segs++;
 204                         bvprv = bv;
 205                         prev = 1;
 206                         seg_size = bv.bv_len;
 207                 }
 208                 bbio = bio;
 209         }
 210
 211         if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
 212                 fbio->bi_seg_front_size = seg_size;
 213         if (seg_size > bbio->bi_seg_back_size)
 214                 bbio->bi_seg_back_size = seg_size;
 215
 216         return nr_phys_segs;
 217 }
 218
 219 void blk_recalc_rq_segments(struct request *rq)
 220 {
 221         bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
 222                         &rq->q->queue_flags);
 223
 224         rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio,
 225                         no_sg_merge);
 226 }
 227
 228 void blk_recount_segments(struct request_queue *q, struct bio *bio)
 229 {
 230         unsigned short seg_cnt;
 231
 232         /* estimate segment number by bi_vcnt for non-cloned bio */
 233         if (bio_flagged(bio, BIO_CLONED))
 234                 seg_cnt = bio_segments(bio);
 235         else
 236                 seg_cnt = bio->bi_vcnt;
 237
 238         if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
 239                         (seg_cnt < queue_max_segments(q)))
 240                 bio->bi_phys_segments = seg_cnt;
 241         else {
 242                 struct bio *nxt = bio->bi_next;
 243
 244                 bio->bi_next = NULL;
 245                 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
 246                 bio->bi_next = nxt;
 247         }
 248
 249         bio_set_flag(bio, BIO_SEG_VALID);
 250 }
 251 EXPORT_SYMBOL(blk_recount_segments);
 252
 253 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
 254                                    struct bio *nxt)
 255 {
 256         struct bio_vec end_bv = { NULL }, nxt_bv;
 257         struct bvec_iter iter;
 258
 259         if (!blk_queue_cluster(q))
 260                 return 0;
 261
 262         if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
 263             queue_max_segment_size(q))
 264                 return 0;
 265
 266         if (!bio_has_data(bio))
 267                 return 1;
 268
 269         bio_for_each_segment(end_bv, bio, iter)
 270                 if (end_bv.bv_len == iter.bi_size)
 271                         break;
 272
 273         nxt_bv = bio_iovec(nxt);
 274
 275         if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv))
 276                 return 0;
 277
 278         /*
 279          * bio and nxt are contiguous in memory; check if the queue allows
 280          * these two to be merged into one
 281          */
 282         if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv))
 283                 return 1;
 284
 285         return 0;
 286 }
 287
 288 static inline void
 289 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
 290                      struct scatterlist *sglist, struct bio_vec *bvprv,
 291                      struct scatterlist **sg, int *nsegs, int *cluster)
 292 {
 293
 294         int nbytes = bvec->bv_len;
 295
 296         if (*sg && *cluster) {
 297                 if ((*sg)->length + nbytes > queue_max_segment_size(q))
 298                         goto new_segment;
 299
 300                 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
 301                         goto new_segment;
 302                 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
 303                         goto new_segment;
 304
 305                 (*sg)->length += nbytes;
 306         } else {
 307 new_segment:
 308                 if (!*sg)
 309                         *sg = sglist;
 310                 else {
 311                         /*
 312                          * If the driver previously mapped a shorter
 313                          * list, we could see a termination bit
 314                          * prematurely unless it fully inits the sg
 315                          * table on each mapping. We KNOW that there
 316                          * must be more entries here or the driver
 317                          * would be buggy, so force clear the
 318                          * termination bit to avoid doing a full
 319                          * sg_init_table() in drivers for each command.
 320                          */
 321                         sg_unmark_end(*sg);
 322                         *sg = sg_next(*sg);
 323                 }
 324
 325                 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
 326                 (*nsegs)++;
 327         }
 328         *bvprv = *bvec;
 329 }
 330
 331 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
 332                              struct scatterlist *sglist,
 333                              struct scatterlist **sg)
 334 {
 335         struct bio_vec bvec, bvprv = { NULL };
 336         struct bvec_iter iter;
 337         int nsegs, cluster;
 338
 339         nsegs = 0;
 340         cluster = blk_queue_cluster(q);
 341
 342         if (bio->bi_rw & REQ_DISCARD) {
 343                 /*
 344                  * This is a hack - drivers should be neither modifying the
 345                  * biovec, nor relying on bi_vcnt - but because of
 346                  * blk_add_request_payload(), a discard bio may or may not have
 347                  * a payload we need to set up here (thank you Christoph) and
 348                  * bi_vcnt is really the only way of telling if we need to.
 349                  */
 350
 351                 if (bio->bi_vcnt)
 352                         goto single_segment;
 353
 354                 return 0;
 355         }
 356
 357         if (bio->bi_rw & REQ_WRITE_SAME) {
 358 single_segment:
 359                 *sg = sglist;
 360                 bvec = bio_iovec(bio);
 361                 sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset);
 362                 return 1;
 363         }
 364
 365         for_each_bio(bio)
 366                 bio_for_each_segment(bvec, bio, iter)
 367                         __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
 368                                              &nsegs, &cluster);
 369
 370         return nsegs;
 371 }
 372
 373 /*
 374  * map a request to scatterlist, return number of sg entries setup. Caller
 375  * must make sure sg can hold rq->nr_phys_segments entries
 376  */
 377 int blk_rq_map_sg(struct request_queue *q, struct request *rq,
 378                   struct scatterlist *sglist)
 379 {
 380         struct scatterlist *sg = NULL;
 381         int nsegs = 0;
 382
 383         if (rq->bio)
 384                 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
 385
 386         if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
 387             (blk_rq_bytes(rq) & q->dma_pad_mask)) {
 388                 unsigned int pad_len =
 389                         (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
 390
 391                 sg->length += pad_len;
 392                 rq->extra_len += pad_len;
 393         }
 394
 395         if (q->dma_drain_size && q->dma_drain_needed(rq)) {
 396                 if (rq->cmd_flags & REQ_WRITE)
 397                         memset(q->dma_drain_buffer, 0, q->dma_drain_size);
 398
 399                 sg_unmark_end(sg);
 400                 sg = sg_next(sg);
 401                 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
 402                             q->dma_drain_size,
 403                             ((unsigned long)q->dma_drain_buffer) &
 404                             (PAGE_SIZE - 1));
 405                 nsegs++;
 406                 rq->extra_len += q->dma_drain_size;
 407         }
 408
 409         if (sg)
 410                 sg_mark_end(sg);
 411
 412         return nsegs;
 413 }
 414 EXPORT_SYMBOL(blk_rq_map_sg);
 415
 416 static inline int ll_new_hw_segment(struct request_queue *q,
 417                                     struct request *req,
 418                                     struct bio *bio)
 419 {
 420         int nr_phys_segs = bio_phys_segments(q, bio);
 421
 422         if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
 423                 goto no_merge;
 424
 425         if (blk_integrity_merge_bio(q, req, bio) == false)
 426                 goto no_merge;
 427
 428         /*
 429          * This will form the start of a new hw segment.  Bump both
 430          * counters.
 431          */
 432         req->nr_phys_segments += nr_phys_segs;
 433         return 1;
 434
 435 no_merge:
 436         req->cmd_flags |= REQ_NOMERGE;
 437         if (req == q->last_merge)
 438                 q->last_merge = NULL;
 439         return 0;
 440 }
 441
 442 int ll_back_merge_fn(struct request_queue *q, struct request *req,
 443                      struct bio *bio)
 444 {
 445         if (req_gap_back_merge(req, bio))
 446                 return 0;
 447         if (blk_integrity_rq(req) &&
 448             integrity_req_gap_back_merge(req, bio))
 449                 return 0;
 450         if (blk_rq_sectors(req) + bio_sectors(bio) >
 451             blk_rq_get_max_sectors(req)) {
 452                 req->cmd_flags |= REQ_NOMERGE;
 453                 if (req == q->last_merge)
 454                         q->last_merge = NULL;
 455                 return 0;
 456         }
 457         if (!bio_flagged(req->biotail, BIO_SEG_VALID))
 458                 blk_recount_segments(q, req->biotail);
 459         if (!bio_flagged(bio, BIO_SEG_VALID))
 460                 blk_recount_segments(q, bio);
 461
 462         return ll_new_hw_segment(q, req, bio);
 463 }
 464
 465 int ll_front_merge_fn(struct request_queue *q, struct request *req,
 466                       struct bio *bio)
 467 {
 468
 469         if (req_gap_front_merge(req, bio))
 470                 return 0;
 471         if (blk_integrity_rq(req) &&
 472             integrity_req_gap_front_merge(req, bio))
 473                 return 0;
 474         if (blk_rq_sectors(req) + bio_sectors(bio) >
 475             blk_rq_get_max_sectors(req)) {
 476                 req->cmd_flags |= REQ_NOMERGE;
 477                 if (req == q->last_merge)
 478                         q->last_merge = NULL;
 479                 return 0;
 480         }
 481         if (!bio_flagged(bio, BIO_SEG_VALID))
 482                 blk_recount_segments(q, bio);
 483         if (!bio_flagged(req->bio, BIO_SEG_VALID))
 484                 blk_recount_segments(q, req->bio);
 485
 486         return ll_new_hw_segment(q, req, bio);
 487 }
 488
 489 /*
 490  * blk-mq uses req->special to carry normal driver per-request payload, it
 491  * does not indicate a prepared command that we cannot merge with.
 492  */
 493 static bool req_no_special_merge(struct request *req)
 494 {
 495         struct request_queue *q = req->q;
 496
 497         return !q->mq_ops && req->special;
 498 }
 499
 500 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
 501                                 struct request *next)
 502 {
 503         int total_phys_segments;
 504         unsigned int seg_size =
 505                 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
 506
 507         /*
 508          * First check if the either of the requests are re-queued
 509          * requests.  Can't merge them if they are.
 510          */
 511         if (req_no_special_merge(req) || req_no_special_merge(next))
 512                 return 0;
 513
 514         if (req_gap_back_merge(req, next->bio))
 515                 return 0;
 516
 517         /*
 518          * Will it become too large?
 519          */
 520         if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
 521             blk_rq_get_max_sectors(req))
 522                 return 0;
 523
 524         total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
 525         if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
 526                 if (req->nr_phys_segments == 1)
 527                         req->bio->bi_seg_front_size = seg_size;
 528                 if (next->nr_phys_segments == 1)
 529                         next->biotail->bi_seg_back_size = seg_size;
 530                 total_phys_segments--;
 531         }
 532
 533         if (total_phys_segments > queue_max_segments(q))
 534                 return 0;
 535
 536         if (blk_integrity_merge_rq(q, req, next) == false)
 537                 return 0;
 538
 539         /* Merge is OK... */
 540         req->nr_phys_segments = total_phys_segments;
 541         return 1;
 542 }
 543
 544 /**
 545  * blk_rq_set_mixed_merge - mark a request as mixed merge
 546  * @rq: request to mark as mixed merge
 547  *
 548  * Description:
 549  *     @rq is about to be mixed merged.  Make sure the attributes
 550  *     which can be mixed are set in each bio and mark @rq as mixed
 551  *     merged.
 552  */
 553 void blk_rq_set_mixed_merge(struct request *rq)
 554 {
 555         unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
 556         struct bio *bio;
 557
 558         if (rq->cmd_flags & REQ_MIXED_MERGE)
 559                 return;
 560
 561         /*
 562          * @rq will no longer represent mixable attributes for all the
 563          * contained bios.  It will just track those of the first one.
 564          * Distributes the attributs to each bio.
 565          */
 566         for (bio = rq->bio; bio; bio = bio->bi_next) {
 567                 WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
 568                              (bio->bi_rw & REQ_FAILFAST_MASK) != ff);
 569                 bio->bi_rw |= ff;
 570         }
 571         rq->cmd_flags |= REQ_MIXED_MERGE;
 572 }
 573
 574 static void blk_account_io_merge(struct request *req)
 575 {
 576         if (blk_do_io_stat(req)) {
 577                 struct hd_struct *part;
 578                 int cpu;
 579
 580                 cpu = part_stat_lock();
 581                 part = req->part;
 582
 583                 part_round_stats(cpu, part);
 584                 part_dec_in_flight(part, rq_data_dir(req));
 585
 586                 hd_struct_put(part);
 587                 part_stat_unlock();
 588         }
 589 }
 590
 591 /*
 592  * Has to be called with the request spinlock acquired
 593  */
 594 static int attempt_merge(struct request_queue *q, struct request *req,
 595                           struct request *next)
 596 {
 597         if (!rq_mergeable(req) || !rq_mergeable(next))
 598                 return 0;
 599
 600         if (!blk_check_merge_flags(req->cmd_flags, next->cmd_flags))
 601                 return 0;
 602
 603         /*
 604          * not contiguous
 605          */
 606         if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
 607                 return 0;
 608
 609         if (rq_data_dir(req) != rq_data_dir(next)
 610             || req->rq_disk != next->rq_disk
 611             || req_no_special_merge(next))
 612                 return 0;
 613
 614         if (req->cmd_flags & REQ_WRITE_SAME &&
 615             !blk_write_same_mergeable(req->bio, next->bio))
 616                 return 0;
 617
 618         /*
 619          * If we are allowed to merge, then append bio list
 620          * from next to rq and release next. merge_requests_fn
 621          * will have updated segment counts, update sector
 622          * counts here.
 623          */
 624         if (!ll_merge_requests_fn(q, req, next))
 625                 return 0;
 626
 627         /*
 628          * If failfast settings disagree or any of the two is already
 629          * a mixed merge, mark both as mixed before proceeding.  This
 630          * makes sure that all involved bios have mixable attributes
 631          * set properly.
 632          */
 633         if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE ||
 634             (req->cmd_flags & REQ_FAILFAST_MASK) !=
 635             (next->cmd_flags & REQ_FAILFAST_MASK)) {
 636                 blk_rq_set_mixed_merge(req);
 637                 blk_rq_set_mixed_merge(next);
 638         }
 639
 640         /*
 641          * At this point we have either done a back merge
 642          * or front merge. We need the smaller start_time of
 643          * the merged requests to be the current request
 644          * for accounting purposes.
 645          */
 646         if (time_after(req->start_time, next->start_time))
 647                 req->start_time = next->start_time;
 648
 649         req->biotail->bi_next = next->bio;
 650         req->biotail = next->biotail;
 651
 652         req->__data_len += blk_rq_bytes(next);
 653
 654         elv_merge_requests(q, req, next);
 655
 656         /*
 657          * 'next' is going away, so update stats accordingly
 658          */
 659         blk_account_io_merge(next);
 660
 661         req->ioprio = ioprio_best(req->ioprio, next->ioprio);
 662         if (blk_rq_cpu_valid(next))
 663                 req->cpu = next->cpu;
 664
 665         /* owner-ship of bio passed from next to req */
 666         next->bio = NULL;
 667         __blk_put_request(q, next);
 668         return 1;
 669 }
 670
 671 int attempt_back_merge(struct request_queue *q, struct request *rq)
 672 {
 673         struct request *next = elv_latter_request(q, rq);
 674
 675         if (next)
 676                 return attempt_merge(q, rq, next);
 677
 678         return 0;
 679 }
 680
 681 int attempt_front_merge(struct request_queue *q, struct request *rq)
 682 {
 683         struct request *prev = elv_former_request(q, rq);
 684
 685         if (prev)
 686                 return attempt_merge(q, prev, rq);
 687
 688         return 0;
 689 }
 690
 691 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
 692                           struct request *next)
 693 {
 694         return attempt_merge(q, rq, next);
 695 }
 696
 697 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 698 {
 699         if (!rq_mergeable(rq) || !bio_mergeable(bio))
 700                 return false;
 701
 702         if (!blk_check_merge_flags(rq->cmd_flags, bio->bi_rw))
 703                 return false;
 704
 705         /* different data direction or already started, don't merge */
 706         if (bio_data_dir(bio) != rq_data_dir(rq))
 707                 return false;
 708
 709         /* must be same device and not a special request */
 710         if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq))
 711                 return false;
 712
 713         /* only merge integrity protected bio into ditto rq */
 714         if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
 715                 return false;
 716
 717         /* must be using the same buffer */
 718         if (rq->cmd_flags & REQ_WRITE_SAME &&
 719             !blk_write_same_mergeable(rq->bio, bio))
 720                 return false;
 721
 722         return true;
 723 }
 724
 725 int blk_try_merge(struct request *rq, struct bio *bio)
 726 {
 727         if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
 728                 return ELEVATOR_BACK_MERGE;
 729         else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
 730                 return ELEVATOR_FRONT_MERGE;
 731         return ELEVATOR_NO_MERGE;
 732 }