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