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