block/blk-merge.c

   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/scatterlist.h>
  10
  11 #include <trace/events/block.h>
  12
  13 #include "blk.h"
  14
  15 /*
  16  * Check if the two bvecs from two bios can be merged to one segment.  If yes,
  17  * no need to check gap between the two bios since the 1st bio and the 1st bvec
  18  * in the 2nd bio can be handled in one segment.
  19  */
  20 static inline bool bios_segs_mergeable(struct request_queue *q,
  21                 struct bio *prev, struct bio_vec *prev_last_bv,
  22                 struct bio_vec *next_first_bv)
  23 {
  24         if (!biovec_phys_mergeable(q, prev_last_bv, next_first_bv))
  25                 return false;
  26         if (prev->bi_seg_back_size + next_first_bv->bv_len >
  27                         queue_max_segment_size(q))
  28                 return false;
  29         return true;
  30 }
  31
  32 static inline bool bio_will_gap(struct request_queue *q,
  33                 struct request *prev_rq, struct bio *prev, struct bio *next)
  34 {
  35         struct bio_vec pb, nb;
  36
  37         if (!bio_has_data(prev) || !queue_virt_boundary(q))
  38                 return false;
  39
  40         /*
  41          * Don't merge if the 1st bio starts with non-zero offset, otherwise it
  42          * is quite difficult to respect the sg gap limit.  We work hard to
  43          * merge a huge number of small single bios in case of mkfs.
  44          */
  45         if (prev_rq)
  46                 bio_get_first_bvec(prev_rq->bio, &pb);
  47         else
  48                 bio_get_first_bvec(prev, &pb);
  49         if (pb.bv_offset)
  50                 return true;
  51
  52         /*
  53          * We don't need to worry about the situation that the merged segment
  54          * ends in unaligned virt boundary:
  55          *
  56          * - if 'pb' ends aligned, the merged segment ends aligned
  57          * - if 'pb' ends unaligned, the next bio must include
  58          *   one single bvec of 'nb', otherwise the 'nb' can't
  59          *   merge with 'pb'
  60          */
  61         bio_get_last_bvec(prev, &pb);
  62         bio_get_first_bvec(next, &nb);
  63         if (bios_segs_mergeable(q, prev, &pb, &nb))
  64                 return false;
  65         return __bvec_gap_to_prev(q, &pb, nb.bv_offset);
  66 }
  67
  68 static inline bool req_gap_back_merge(struct request *req, struct bio *bio)
  69 {
  70         return bio_will_gap(req->q, req, req->biotail, bio);
  71 }
  72
  73 static inline bool req_gap_front_merge(struct request *req, struct bio *bio)
  74 {
  75         return bio_will_gap(req->q, NULL, bio, req->bio);
  76 }
  77
  78 static struct bio *blk_bio_discard_split(struct request_queue *q,
  79                                          struct bio *bio,
  80                                          struct bio_set *bs,
  81                                          unsigned *nsegs)
  82 {
  83         unsigned int max_discard_sectors, granularity;
  84         int alignment;
  85         sector_t tmp;
  86         unsigned split_sectors;
  87
  88         *nsegs = 1;
  89
  90         /* Zero-sector (unknown) and one-sector granularities are the same.  */
  91         granularity = max(q->limits.discard_granularity >> 9, 1U);
  92
  93         max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
  94         max_discard_sectors -= max_discard_sectors % granularity;
  95
  96         if (unlikely(!max_discard_sectors)) {
  97                 /* XXX: warn */
  98                 return NULL;
  99         }
 100
 101         if (bio_sectors(bio) <= max_discard_sectors)
 102                 return NULL;
 103
 104         split_sectors = max_discard_sectors;
 105
 106         /*
 107          * If the next starting sector would be misaligned, stop the discard at
 108          * the previous aligned sector.
 109          */
 110         alignment = (q->limits.discard_alignment >> 9) % granularity;
 111
 112         tmp = bio->bi_iter.bi_sector + split_sectors - alignment;
 113         tmp = sector_div(tmp, granularity);
 114
 115         if (split_sectors > tmp)
 116                 split_sectors -= tmp;
 117
 118         return bio_split(bio, split_sectors, GFP_NOIO, bs);
 119 }
 120
 121 static struct bio *blk_bio_write_zeroes_split(struct request_queue *q,
 122                 struct bio *bio, struct bio_set *bs, unsigned *nsegs)
 123 {
 124         *nsegs = 1;
 125
 126         if (!q->limits.max_write_zeroes_sectors)
 127                 return NULL;
 128
 129         if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors)
 130                 return NULL;
 131
 132         return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs);
 133 }
 134
 135 static struct bio *blk_bio_write_same_split(struct request_queue *q,
 136                                             struct bio *bio,
 137                                             struct bio_set *bs,
 138                                             unsigned *nsegs)
 139 {
 140         *nsegs = 1;
 141
 142         if (!q->limits.max_write_same_sectors)
 143                 return NULL;
 144
 145         if (bio_sectors(bio) <= q->limits.max_write_same_sectors)
 146                 return NULL;
 147
 148         return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
 149 }
 150
 151 static inline unsigned get_max_io_size(struct request_queue *q,
 152                                        struct bio *bio)
 153 {
 154         unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);
 155         unsigned mask = queue_logical_block_size(q) - 1;
 156
 157         /* aligned to logical block size */
 158         sectors &= ~(mask >> 9);
 159
 160         return sectors;
 161 }
 162
 163 static struct bio *blk_bio_segment_split(struct request_queue *q,
 164                                          struct bio *bio,
 165                                          struct bio_set *bs,
 166                                          unsigned *segs)
 167 {
 168         struct bio_vec bv, bvprv, *bvprvp = NULL;
 169         struct bvec_iter iter;
 170         unsigned seg_size = 0, nsegs = 0, sectors = 0;
 171         unsigned front_seg_size = bio->bi_seg_front_size;
 172         bool do_split = true;
 173         struct bio *new = NULL;
 174         const unsigned max_sectors = get_max_io_size(q, bio);
 175
 176         bio_for_each_segment(bv, bio, iter) {
 177                 /*
 178                  * If the queue doesn't support SG gaps and adding this
 179                  * offset would create a gap, disallow it.
 180                  */
 181                 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
 182                         goto split;
 183
 184                 if (sectors + (bv.bv_len >> 9) > max_sectors) {
 185                         /*
 186                          * Consider this a new segment if we're splitting in
 187                          * the middle of this vector.
 188                          */
 189                         if (nsegs < queue_max_segments(q) &&
 190                             sectors < max_sectors) {
 191                                 nsegs++;
 192                                 sectors = max_sectors;
 193                         }
 194                         goto split;
 195                 }
 196
 197                 if (bvprvp && blk_queue_cluster(q)) {
 198                         if (seg_size + bv.bv_len > queue_max_segment_size(q))
 199                                 goto new_segment;
 200                         if (!biovec_phys_mergeable(q, bvprvp, &bv))
 201                                 goto new_segment;
 202
 203                         seg_size += bv.bv_len;
 204                         bvprv = bv;
 205                         bvprvp = &bvprv;
 206                         sectors += bv.bv_len >> 9;
 207
 208                         continue;
 209                 }
 210 new_segment:
 211                 if (nsegs == queue_max_segments(q))
 212                         goto split;
 213
 214                 if (nsegs == 1 && seg_size > front_seg_size)
 215                         front_seg_size = seg_size;
 216
 217                 nsegs++;
 218                 bvprv = bv;
 219                 bvprvp = &bvprv;
 220                 seg_size = bv.bv_len;
 221                 sectors += bv.bv_len >> 9;
 222
 223         }
 224
 225         do_split = false;
 226 split:
 227         *segs = nsegs;
 228
 229         if (do_split) {
 230                 new = bio_split(bio, sectors, GFP_NOIO, bs);
 231                 if (new)
 232                         bio = new;
 233         }
 234
 235         if (nsegs == 1 && seg_size > front_seg_size)
 236                 front_seg_size = seg_size;
 237         bio->bi_seg_front_size = front_seg_size;
 238         if (seg_size > bio->bi_seg_back_size)
 239                 bio->bi_seg_back_size = seg_size;
 240
 241         return do_split ? new : NULL;
 242 }
 243
 244 void blk_queue_split(struct request_queue *q, struct bio **bio)
 245 {
 246         struct bio *split, *res;
 247         unsigned nsegs;
 248
 249         switch (bio_op(*bio)) {
 250         case REQ_OP_DISCARD:
 251         case REQ_OP_SECURE_ERASE:
 252                 split = blk_bio_discard_split(q, *bio, &q->bio_split, &nsegs);
 253                 break;
 254         case REQ_OP_WRITE_ZEROES:
 255                 split = blk_bio_write_zeroes_split(q, *bio, &q->bio_split, &nsegs);
 256                 break;
 257         case REQ_OP_WRITE_SAME:
 258                 split = blk_bio_write_same_split(q, *bio, &q->bio_split, &nsegs);
 259                 break;
 260         default:
 261                 split = blk_bio_segment_split(q, *bio, &q->bio_split, &nsegs);
 262                 break;
 263         }
 264
 265         /* physical segments can be figured out during splitting */
 266         res = split ? split : *bio;
 267         res->bi_phys_segments = nsegs;
 268         bio_set_flag(res, BIO_SEG_VALID);
 269
 270         if (split) {
 271                 /* there isn't chance to merge the splitted bio */
 272                 split->bi_opf |= REQ_NOMERGE;
 273
 274                 /*
 275                  * Since we're recursing into make_request here, ensure
 276                  * that we mark this bio as already having entered the queue.
 277                  * If not, and the queue is going away, we can get stuck
 278                  * forever on waiting for the queue reference to drop. But
 279                  * that will never happen, as we're already holding a
 280                  * reference to it.
 281                  */
 282                 bio_set_flag(*bio, BIO_QUEUE_ENTERED);
 283
 284                 bio_chain(split, *bio);
 285                 trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
 286                 generic_make_request(*bio);
 287                 *bio = split;
 288         }
 289 }
 290 EXPORT_SYMBOL(blk_queue_split);
 291
 292 static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
 293                                              struct bio *bio,
 294                                              bool no_sg_merge)
 295 {
 296         struct bio_vec bv, bvprv = { NULL };
 297         int cluster, prev = 0;
 298         unsigned int seg_size, nr_phys_segs;
 299         struct bio *fbio, *bbio;
 300         struct bvec_iter iter;
 301
 302         if (!bio)
 303                 return 0;
 304
 305         switch (bio_op(bio)) {
 306         case REQ_OP_DISCARD:
 307         case REQ_OP_SECURE_ERASE:
 308         case REQ_OP_WRITE_ZEROES:
 309                 return 0;
 310         case REQ_OP_WRITE_SAME:
 311                 return 1;
 312         }
 313
 314         fbio = bio;
 315         cluster = blk_queue_cluster(q);
 316         seg_size = 0;
 317         nr_phys_segs = 0;
 318         for_each_bio(bio) {
 319                 bio_for_each_segment(bv, bio, iter) {
 320                         /*
 321                          * If SG merging is disabled, each bio vector is
 322                          * a segment
 323                          */
 324                         if (no_sg_merge)
 325                                 goto new_segment;
 326
 327                         if (prev && cluster) {
 328                                 if (seg_size + bv.bv_len
 329                                     > queue_max_segment_size(q))
 330                                         goto new_segment;
 331                                 if (!biovec_phys_mergeable(q, &bvprv, &bv))
 332                                         goto new_segment;
 333
 334                                 seg_size += bv.bv_len;
 335                                 bvprv = bv;
 336                                 continue;
 337                         }
 338 new_segment:
 339                         if (nr_phys_segs == 1 && seg_size >
 340                             fbio->bi_seg_front_size)
 341                                 fbio->bi_seg_front_size = seg_size;
 342
 343                         nr_phys_segs++;
 344                         bvprv = bv;
 345                         prev = 1;
 346                         seg_size = bv.bv_len;
 347                 }
 348                 bbio = bio;
 349         }
 350
 351         if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
 352                 fbio->bi_seg_front_size = seg_size;
 353         if (seg_size > bbio->bi_seg_back_size)
 354                 bbio->bi_seg_back_size = seg_size;
 355
 356         return nr_phys_segs;
 357 }
 358
 359 void blk_recalc_rq_segments(struct request *rq)
 360 {
 361         bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
 362                         &rq->q->queue_flags);
 363
 364         rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio,
 365                         no_sg_merge);
 366 }
 367
 368 void blk_recount_segments(struct request_queue *q, struct bio *bio)
 369 {
 370         unsigned short seg_cnt;
 371
 372         /* estimate segment number by bi_vcnt for non-cloned bio */
 373         if (bio_flagged(bio, BIO_CLONED))
 374                 seg_cnt = bio_segments(bio);
 375         else
 376                 seg_cnt = bio->bi_vcnt;
 377
 378         if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
 379                         (seg_cnt < queue_max_segments(q)))
 380                 bio->bi_phys_segments = seg_cnt;
 381         else {
 382                 struct bio *nxt = bio->bi_next;
 383
 384                 bio->bi_next = NULL;
 385                 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
 386                 bio->bi_next = nxt;
 387         }
 388
 389         bio_set_flag(bio, BIO_SEG_VALID);
 390 }
 391 EXPORT_SYMBOL(blk_recount_segments);
 392
 393 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
 394                                    struct bio *nxt)
 395 {
 396         struct bio_vec end_bv = { NULL }, nxt_bv;
 397
 398         if (!blk_queue_cluster(q))
 399                 return 0;
 400
 401         if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
 402             queue_max_segment_size(q))
 403                 return 0;
 404
 405         if (!bio_has_data(bio))
 406                 return 1;
 407
 408         bio_get_last_bvec(bio, &end_bv);
 409         bio_get_first_bvec(nxt, &nxt_bv);
 410
 411         return biovec_phys_mergeable(q, &end_bv, &nxt_bv);
 412 }
 413
 414 static inline void
 415 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
 416                      struct scatterlist *sglist, struct bio_vec *bvprv,
 417                      struct scatterlist **sg, int *nsegs, int *cluster)
 418 {
 419
 420         int nbytes = bvec->bv_len;
 421
 422         if (*sg && *cluster) {
 423                 if ((*sg)->length + nbytes > queue_max_segment_size(q))
 424                         goto new_segment;
 425                 if (!biovec_phys_mergeable(q, bvprv, bvec))
 426                         goto new_segment;
 427
 428                 (*sg)->length += nbytes;
 429         } else {
 430 new_segment:
 431                 if (!*sg)
 432                         *sg = sglist;
 433                 else {
 434                         /*
 435                          * If the driver previously mapped a shorter
 436                          * list, we could see a termination bit
 437                          * prematurely unless it fully inits the sg
 438                          * table on each mapping. We KNOW that there
 439                          * must be more entries here or the driver
 440                          * would be buggy, so force clear the
 441                          * termination bit to avoid doing a full
 442                          * sg_init_table() in drivers for each command.
 443                          */
 444                         sg_unmark_end(*sg);
 445                         *sg = sg_next(*sg);
 446                 }
 447
 448                 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
 449                 (*nsegs)++;
 450         }
 451         *bvprv = *bvec;
 452 }
 453
 454 static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv,
 455                 struct scatterlist *sglist, struct scatterlist **sg)
 456 {
 457         *sg = sglist;
 458         sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
 459         return 1;
 460 }
 461
 462 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
 463                              struct scatterlist *sglist,
 464                              struct scatterlist **sg)
 465 {
 466         struct bio_vec bvec, bvprv = { NULL };
 467         struct bvec_iter iter;
 468         int cluster = blk_queue_cluster(q), nsegs = 0;
 469
 470         for_each_bio(bio)
 471                 bio_for_each_segment(bvec, bio, iter)
 472                         __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
 473                                              &nsegs, &cluster);
 474
 475         return nsegs;
 476 }
 477
 478 /*
 479  * map a request to scatterlist, return number of sg entries setup. Caller
 480  * must make sure sg can hold rq->nr_phys_segments entries
 481  */
 482 int blk_rq_map_sg(struct request_queue *q, struct request *rq,
 483                   struct scatterlist *sglist)
 484 {
 485         struct scatterlist *sg = NULL;
 486         int nsegs = 0;
 487
 488         if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
 489                 nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg);
 490         else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME)
 491                 nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg);
 492         else if (rq->bio)
 493                 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
 494
 495         if (unlikely(rq->rq_flags & RQF_COPY_USER) &&
 496             (blk_rq_bytes(rq) & q->dma_pad_mask)) {
 497                 unsigned int pad_len =
 498                         (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
 499
 500                 sg->length += pad_len;
 501                 rq->extra_len += pad_len;
 502         }
 503
 504         if (q->dma_drain_size && q->dma_drain_needed(rq)) {
 505                 if (op_is_write(req_op(rq)))
 506                         memset(q->dma_drain_buffer, 0, q->dma_drain_size);
 507
 508                 sg_unmark_end(sg);
 509                 sg = sg_next(sg);
 510                 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
 511                             q->dma_drain_size,
 512                             ((unsigned long)q->dma_drain_buffer) &
 513                             (PAGE_SIZE - 1));
 514                 nsegs++;
 515                 rq->extra_len += q->dma_drain_size;
 516         }
 517
 518         if (sg)
 519                 sg_mark_end(sg);
 520
 521         /*
 522          * Something must have been wrong if the figured number of
 523          * segment is bigger than number of req's physical segments
 524          */
 525         WARN_ON(nsegs > blk_rq_nr_phys_segments(rq));
 526
 527         return nsegs;
 528 }
 529 EXPORT_SYMBOL(blk_rq_map_sg);
 530
 531 static inline int ll_new_hw_segment(struct request_queue *q,
 532                                     struct request *req,
 533                                     struct bio *bio)
 534 {
 535         int nr_phys_segs = bio_phys_segments(q, bio);
 536
 537         if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
 538                 goto no_merge;
 539
 540         if (blk_integrity_merge_bio(q, req, bio) == false)
 541                 goto no_merge;
 542
 543         /*
 544          * This will form the start of a new hw segment.  Bump both
 545          * counters.
 546          */
 547         req->nr_phys_segments += nr_phys_segs;
 548         return 1;
 549
 550 no_merge:
 551         req_set_nomerge(q, req);
 552         return 0;
 553 }
 554
 555 int ll_back_merge_fn(struct request_queue *q, struct request *req,
 556                      struct bio *bio)
 557 {
 558         if (req_gap_back_merge(req, bio))
 559                 return 0;
 560         if (blk_integrity_rq(req) &&
 561             integrity_req_gap_back_merge(req, bio))
 562                 return 0;
 563         if (blk_rq_sectors(req) + bio_sectors(bio) >
 564             blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
 565                 req_set_nomerge(q, req);
 566                 return 0;
 567         }
 568         if (!bio_flagged(req->biotail, BIO_SEG_VALID))
 569                 blk_recount_segments(q, req->biotail);
 570         if (!bio_flagged(bio, BIO_SEG_VALID))
 571                 blk_recount_segments(q, bio);
 572
 573         return ll_new_hw_segment(q, req, bio);
 574 }
 575
 576 int ll_front_merge_fn(struct request_queue *q, struct request *req,
 577                       struct bio *bio)
 578 {
 579
 580         if (req_gap_front_merge(req, bio))
 581                 return 0;
 582         if (blk_integrity_rq(req) &&
 583             integrity_req_gap_front_merge(req, bio))
 584                 return 0;
 585         if (blk_rq_sectors(req) + bio_sectors(bio) >
 586             blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
 587                 req_set_nomerge(q, req);
 588                 return 0;
 589         }
 590         if (!bio_flagged(bio, BIO_SEG_VALID))
 591                 blk_recount_segments(q, bio);
 592         if (!bio_flagged(req->bio, BIO_SEG_VALID))
 593                 blk_recount_segments(q, req->bio);
 594
 595         return ll_new_hw_segment(q, req, bio);
 596 }
 597
 598 /*
 599  * blk-mq uses req->special to carry normal driver per-request payload, it
 600  * does not indicate a prepared command that we cannot merge with.
 601  */
 602 static bool req_no_special_merge(struct request *req)
 603 {
 604         struct request_queue *q = req->q;
 605
 606         return !q->mq_ops && req->special;
 607 }
 608
 609 static bool req_attempt_discard_merge(struct request_queue *q, struct request *req,
 610                 struct request *next)
 611 {
 612         unsigned short segments = blk_rq_nr_discard_segments(req);
 613
 614         if (segments >= queue_max_discard_segments(q))
 615                 goto no_merge;
 616         if (blk_rq_sectors(req) + bio_sectors(next->bio) >
 617             blk_rq_get_max_sectors(req, blk_rq_pos(req)))
 618                 goto no_merge;
 619
 620         req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next);
 621         return true;
 622 no_merge:
 623         req_set_nomerge(q, req);
 624         return false;
 625 }
 626
 627 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
 628                                 struct request *next)
 629 {
 630         int total_phys_segments;
 631         unsigned int seg_size =
 632                 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
 633
 634         /*
 635          * First check if the either of the requests are re-queued
 636          * requests.  Can't merge them if they are.
 637          */
 638         if (req_no_special_merge(req) || req_no_special_merge(next))
 639                 return 0;
 640
 641         if (req_gap_back_merge(req, next->bio))
 642                 return 0;
 643
 644         /*
 645          * Will it become too large?
 646          */
 647         if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
 648             blk_rq_get_max_sectors(req, blk_rq_pos(req)))
 649                 return 0;
 650
 651         total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
 652         if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
 653                 if (req->nr_phys_segments == 1)
 654                         req->bio->bi_seg_front_size = seg_size;
 655                 if (next->nr_phys_segments == 1)
 656                         next->biotail->bi_seg_back_size = seg_size;
 657                 total_phys_segments--;
 658         }
 659
 660         if (total_phys_segments > queue_max_segments(q))
 661                 return 0;
 662
 663         if (blk_integrity_merge_rq(q, req, next) == false)
 664                 return 0;
 665
 666         /* Merge is OK... */
 667         req->nr_phys_segments = total_phys_segments;
 668         return 1;
 669 }
 670
 671 /**
 672  * blk_rq_set_mixed_merge - mark a request as mixed merge
 673  * @rq: request to mark as mixed merge
 674  *
 675  * Description:
 676  *     @rq is about to be mixed merged.  Make sure the attributes
 677  *     which can be mixed are set in each bio and mark @rq as mixed
 678  *     merged.
 679  */
 680 void blk_rq_set_mixed_merge(struct request *rq)
 681 {
 682         unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
 683         struct bio *bio;
 684
 685         if (rq->rq_flags & RQF_MIXED_MERGE)
 686                 return;
 687
 688         /*
 689          * @rq will no longer represent mixable attributes for all the
 690          * contained bios.  It will just track those of the first one.
 691          * Distributes the attributs to each bio.
 692          */
 693         for (bio = rq->bio; bio; bio = bio->bi_next) {
 694                 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) &&
 695                              (bio->bi_opf & REQ_FAILFAST_MASK) != ff);
 696                 bio->bi_opf |= ff;
 697         }
 698         rq->rq_flags |= RQF_MIXED_MERGE;
 699 }
 700
 701 static void blk_account_io_merge(struct request *req)
 702 {
 703         if (blk_do_io_stat(req)) {
 704                 struct hd_struct *part;
 705                 int cpu;
 706
 707                 cpu = part_stat_lock();
 708                 part = req->part;
 709
 710                 part_round_stats(req->q, cpu, part);
 711                 part_dec_in_flight(req->q, part, rq_data_dir(req));
 712
 713                 hd_struct_put(part);
 714                 part_stat_unlock();
 715         }
 716 }
 717
 718 /*
 719  * For non-mq, this has to be called with the request spinlock acquired.
 720  * For mq with scheduling, the appropriate queue wide lock should be held.
 721  */
 722 static struct request *attempt_merge(struct request_queue *q,
 723                                      struct request *req, struct request *next)
 724 {
 725         if (!q->mq_ops)
 726                 lockdep_assert_held(q->queue_lock);
 727
 728         if (!rq_mergeable(req) || !rq_mergeable(next))
 729                 return NULL;
 730
 731         if (req_op(req) != req_op(next))
 732                 return NULL;
 733
 734         /*
 735          * not contiguous
 736          */
 737         if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
 738                 return NULL;
 739
 740         if (rq_data_dir(req) != rq_data_dir(next)
 741             || req->rq_disk != next->rq_disk
 742             || req_no_special_merge(next))
 743                 return NULL;
 744
 745         if (req_op(req) == REQ_OP_WRITE_SAME &&
 746             !blk_write_same_mergeable(req->bio, next->bio))
 747                 return NULL;
 748
 749         /*
 750          * Don't allow merge of different write hints, or for a hint with
 751          * non-hint IO.
 752          */
 753         if (req->write_hint != next->write_hint)
 754                 return NULL;
 755
 756         /*
 757          * If we are allowed to merge, then append bio list
 758          * from next to rq and release next. merge_requests_fn
 759          * will have updated segment counts, update sector
 760          * counts here. Handle DISCARDs separately, as they
 761          * have separate settings.
 762          */
 763         if (req_op(req) == REQ_OP_DISCARD) {
 764                 if (!req_attempt_discard_merge(q, req, next))
 765                         return NULL;
 766         } else if (!ll_merge_requests_fn(q, req, next))
 767                 return NULL;
 768
 769         /*
 770          * If failfast settings disagree or any of the two is already
 771          * a mixed merge, mark both as mixed before proceeding.  This
 772          * makes sure that all involved bios have mixable attributes
 773          * set properly.
 774          */
 775         if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) ||
 776             (req->cmd_flags & REQ_FAILFAST_MASK) !=
 777             (next->cmd_flags & REQ_FAILFAST_MASK)) {
 778                 blk_rq_set_mixed_merge(req);
 779                 blk_rq_set_mixed_merge(next);
 780         }
 781
 782         /*
 783          * At this point we have either done a back merge or front merge. We
 784          * need the smaller start_time_ns of the merged requests to be the
 785          * current request for accounting purposes.
 786          */
 787         if (next->start_time_ns < req->start_time_ns)
 788                 req->start_time_ns = next->start_time_ns;
 789
 790         req->biotail->bi_next = next->bio;
 791         req->biotail = next->biotail;
 792
 793         req->__data_len += blk_rq_bytes(next);
 794
 795         if (req_op(req) != REQ_OP_DISCARD)
 796                 elv_merge_requests(q, req, next);
 797
 798         /*
 799          * 'next' is going away, so update stats accordingly
 800          */
 801         blk_account_io_merge(next);
 802
 803         req->ioprio = ioprio_best(req->ioprio, next->ioprio);
 804         if (blk_rq_cpu_valid(next))
 805                 req->cpu = next->cpu;
 806
 807         /*
 808          * ownership of bio passed from next to req, return 'next' for
 809          * the caller to free
 810          */
 811         next->bio = NULL;
 812         return next;
 813 }
 814
 815 struct request *attempt_back_merge(struct request_queue *q, struct request *rq)
 816 {
 817         struct request *next = elv_latter_request(q, rq);
 818
 819         if (next)
 820                 return attempt_merge(q, rq, next);
 821
 822         return NULL;
 823 }
 824
 825 struct request *attempt_front_merge(struct request_queue *q, struct request *rq)
 826 {
 827         struct request *prev = elv_former_request(q, rq);
 828
 829         if (prev)
 830                 return attempt_merge(q, prev, rq);
 831
 832         return NULL;
 833 }
 834
 835 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
 836                           struct request *next)
 837 {
 838         struct elevator_queue *e = q->elevator;
 839         struct request *free;
 840
 841         if (!e->uses_mq && e->type->ops.sq.elevator_allow_rq_merge_fn)
 842                 if (!e->type->ops.sq.elevator_allow_rq_merge_fn(q, rq, next))
 843                         return 0;
 844
 845         free = attempt_merge(q, rq, next);
 846         if (free) {
 847                 __blk_put_request(q, free);
 848                 return 1;
 849         }
 850
 851         return 0;
 852 }
 853
 854 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 855 {
 856         if (!rq_mergeable(rq) || !bio_mergeable(bio))
 857                 return false;
 858
 859         if (req_op(rq) != bio_op(bio))
 860                 return false;
 861
 862         /* different data direction or already started, don't merge */
 863         if (bio_data_dir(bio) != rq_data_dir(rq))
 864                 return false;
 865
 866         /* must be same device and not a special request */
 867         if (rq->rq_disk != bio->bi_disk || req_no_special_merge(rq))
 868                 return false;
 869
 870         /* only merge integrity protected bio into ditto rq */
 871         if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
 872                 return false;
 873
 874         /* must be using the same buffer */
 875         if (req_op(rq) == REQ_OP_WRITE_SAME &&
 876             !blk_write_same_mergeable(rq->bio, bio))
 877                 return false;
 878
 879         /*
 880          * Don't allow merge of different write hints, or for a hint with
 881          * non-hint IO.
 882          */
 883         if (rq->write_hint != bio->bi_write_hint)
 884                 return false;
 885
 886         return true;
 887 }
 888
 889 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
 890 {
 891         if (req_op(rq) == REQ_OP_DISCARD &&
 892             queue_max_discard_segments(rq->q) > 1)
 893                 return ELEVATOR_DISCARD_MERGE;
 894         else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
 895                 return ELEVATOR_BACK_MERGE;
 896         else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
 897                 return ELEVATOR_FRONT_MERGE;
 898         return ELEVATOR_NO_MERGE;
 899 }