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