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 = bio_segments(bio);
 304
 305         if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
 306                         (seg_cnt < queue_max_segments(q)))
 307                 bio->bi_phys_segments = seg_cnt;
 308         else {
 309                 struct bio *nxt = bio->bi_next;
 310
 311                 bio->bi_next = NULL;
 312                 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
 313                 bio->bi_next = nxt;
 314         }
 315
 316         bio_set_flag(bio, BIO_SEG_VALID);
 317 }
 318 EXPORT_SYMBOL(blk_recount_segments);
 319
 320 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
 321                                    struct bio *nxt)
 322 {
 323         struct bio_vec end_bv = { NULL }, nxt_bv;
 324
 325         if (!blk_queue_cluster(q))
 326                 return 0;
 327
 328         if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
 329             queue_max_segment_size(q))
 330                 return 0;
 331
 332         if (!bio_has_data(bio))
 333                 return 1;
 334
 335         bio_get_last_bvec(bio, &end_bv);
 336         bio_get_first_bvec(nxt, &nxt_bv);
 337
 338         if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv))
 339                 return 0;
 340
 341         /*
 342          * bio and nxt are contiguous in memory; check if the queue allows
 343          * these two to be merged into one
 344          */
 345         if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv))
 346                 return 1;
 347
 348         return 0;
 349 }
 350
 351 static inline void
 352 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
 353                      struct scatterlist *sglist, struct bio_vec *bvprv,
 354                      struct scatterlist **sg, int *nsegs, int *cluster)
 355 {
 356
 357         int nbytes = bvec->bv_len;
 358
 359         if (*sg && *cluster) {
 360                 if ((*sg)->length + nbytes > queue_max_segment_size(q))
 361                         goto new_segment;
 362
 363                 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
 364                         goto new_segment;
 365                 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
 366                         goto new_segment;
 367
 368                 (*sg)->length += nbytes;
 369         } else {
 370 new_segment:
 371                 if (!*sg)
 372                         *sg = sglist;
 373                 else {
 374                         /*
 375                          * If the driver previously mapped a shorter
 376                          * list, we could see a termination bit
 377                          * prematurely unless it fully inits the sg
 378                          * table on each mapping. We KNOW that there
 379                          * must be more entries here or the driver
 380                          * would be buggy, so force clear the
 381                          * termination bit to avoid doing a full
 382                          * sg_init_table() in drivers for each command.
 383                          */
 384                         sg_unmark_end(*sg);
 385                         *sg = sg_next(*sg);
 386                 }
 387
 388                 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
 389                 (*nsegs)++;
 390         }
 391         *bvprv = *bvec;
 392 }
 393
 394 static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv,
 395                 struct scatterlist *sglist, struct scatterlist **sg)
 396 {
 397         *sg = sglist;
 398         sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
 399         return 1;
 400 }
 401
 402 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
 403                              struct scatterlist *sglist,
 404                              struct scatterlist **sg)
 405 {
 406         struct bio_vec bvec, bvprv = { NULL };
 407         struct bvec_iter iter;
 408         int cluster = blk_queue_cluster(q), nsegs = 0;
 409
 410         for_each_bio(bio)
 411                 bio_for_each_segment(bvec, bio, iter)
 412                         __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
 413                                              &nsegs, &cluster);
 414
 415         return nsegs;
 416 }
 417
 418 /*
 419  * map a request to scatterlist, return number of sg entries setup. Caller
 420  * must make sure sg can hold rq->nr_phys_segments entries
 421  */
 422 int blk_rq_map_sg(struct request_queue *q, struct request *rq,
 423                   struct scatterlist *sglist)
 424 {
 425         struct scatterlist *sg = NULL;
 426         int nsegs = 0;
 427
 428         if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
 429                 nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg);
 430         else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME)
 431                 nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg);
 432         else if (rq->bio)
 433                 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
 434
 435         if (unlikely(rq->rq_flags & RQF_COPY_USER) &&
 436             (blk_rq_bytes(rq) & q->dma_pad_mask)) {
 437                 unsigned int pad_len =
 438                         (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
 439
 440                 sg->length += pad_len;
 441                 rq->extra_len += pad_len;
 442         }
 443
 444         if (q->dma_drain_size && q->dma_drain_needed(rq)) {
 445                 if (op_is_write(req_op(rq)))
 446                         memset(q->dma_drain_buffer, 0, q->dma_drain_size);
 447
 448                 sg_unmark_end(sg);
 449                 sg = sg_next(sg);
 450                 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
 451                             q->dma_drain_size,
 452                             ((unsigned long)q->dma_drain_buffer) &
 453                             (PAGE_SIZE - 1));
 454                 nsegs++;
 455                 rq->extra_len += q->dma_drain_size;
 456         }
 457
 458         if (sg)
 459                 sg_mark_end(sg);
 460
 461         /*
 462          * Something must have been wrong if the figured number of
 463          * segment is bigger than number of req's physical segments
 464          */
 465         WARN_ON(nsegs > blk_rq_nr_phys_segments(rq));
 466
 467         return nsegs;
 468 }
 469 EXPORT_SYMBOL(blk_rq_map_sg);
 470
 471 static inline int ll_new_hw_segment(struct request_queue *q,
 472                                     struct request *req,
 473                                     struct bio *bio)
 474 {
 475         int nr_phys_segs = bio_phys_segments(q, bio);
 476
 477         if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
 478                 goto no_merge;
 479
 480         if (blk_integrity_merge_bio(q, req, bio) == false)
 481                 goto no_merge;
 482
 483         /*
 484          * This will form the start of a new hw segment.  Bump both
 485          * counters.
 486          */
 487         req->nr_phys_segments += nr_phys_segs;
 488         return 1;
 489
 490 no_merge:
 491         req_set_nomerge(q, req);
 492         return 0;
 493 }
 494
 495 int ll_back_merge_fn(struct request_queue *q, struct request *req,
 496                      struct bio *bio)
 497 {
 498         if (req_gap_back_merge(req, bio))
 499                 return 0;
 500         if (blk_integrity_rq(req) &&
 501             integrity_req_gap_back_merge(req, bio))
 502                 return 0;
 503         if (blk_rq_sectors(req) + bio_sectors(bio) >
 504             blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
 505                 req_set_nomerge(q, req);
 506                 return 0;
 507         }
 508         if (!bio_flagged(req->biotail, BIO_SEG_VALID))
 509                 blk_recount_segments(q, req->biotail);
 510         if (!bio_flagged(bio, BIO_SEG_VALID))
 511                 blk_recount_segments(q, bio);
 512
 513         return ll_new_hw_segment(q, req, bio);
 514 }
 515
 516 int ll_front_merge_fn(struct request_queue *q, struct request *req,
 517                       struct bio *bio)
 518 {
 519
 520         if (req_gap_front_merge(req, bio))
 521                 return 0;
 522         if (blk_integrity_rq(req) &&
 523             integrity_req_gap_front_merge(req, bio))
 524                 return 0;
 525         if (blk_rq_sectors(req) + bio_sectors(bio) >
 526             blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
 527                 req_set_nomerge(q, req);
 528                 return 0;
 529         }
 530         if (!bio_flagged(bio, BIO_SEG_VALID))
 531                 blk_recount_segments(q, bio);
 532         if (!bio_flagged(req->bio, BIO_SEG_VALID))
 533                 blk_recount_segments(q, req->bio);
 534
 535         return ll_new_hw_segment(q, req, bio);
 536 }
 537
 538 /*
 539  * blk-mq uses req->special to carry normal driver per-request payload, it
 540  * does not indicate a prepared command that we cannot merge with.
 541  */
 542 static bool req_no_special_merge(struct request *req)
 543 {
 544         struct request_queue *q = req->q;
 545
 546         return !q->mq_ops && req->special;
 547 }
 548
 549 static bool req_attempt_discard_merge(struct request_queue *q, struct request *req,
 550                 struct request *next)
 551 {
 552         unsigned short segments = blk_rq_nr_discard_segments(req);
 553
 554         if (segments >= queue_max_discard_segments(q))
 555                 goto no_merge;
 556         if (blk_rq_sectors(req) + bio_sectors(next->bio) >
 557             blk_rq_get_max_sectors(req, blk_rq_pos(req)))
 558                 goto no_merge;
 559
 560         req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next);
 561         return true;
 562 no_merge:
 563         req_set_nomerge(q, req);
 564         return false;
 565 }
 566
 567 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
 568                                 struct request *next)
 569 {
 570         int total_phys_segments;
 571         unsigned int seg_size =
 572                 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
 573
 574         /*
 575          * First check if the either of the requests are re-queued
 576          * requests.  Can't merge them if they are.
 577          */
 578         if (req_no_special_merge(req) || req_no_special_merge(next))
 579                 return 0;
 580
 581         if (req_gap_back_merge(req, next->bio))
 582                 return 0;
 583
 584         /*
 585          * Will it become too large?
 586          */
 587         if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
 588             blk_rq_get_max_sectors(req, blk_rq_pos(req)))
 589                 return 0;
 590
 591         total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
 592         if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
 593                 if (req->nr_phys_segments == 1)
 594                         req->bio->bi_seg_front_size = seg_size;
 595                 if (next->nr_phys_segments == 1)
 596                         next->biotail->bi_seg_back_size = seg_size;
 597                 total_phys_segments--;
 598         }
 599
 600         if (total_phys_segments > queue_max_segments(q))
 601                 return 0;
 602
 603         if (blk_integrity_merge_rq(q, req, next) == false)
 604                 return 0;
 605
 606         /* Merge is OK... */
 607         req->nr_phys_segments = total_phys_segments;
 608         return 1;
 609 }
 610
 611 /**
 612  * blk_rq_set_mixed_merge - mark a request as mixed merge
 613  * @rq: request to mark as mixed merge
 614  *
 615  * Description:
 616  *     @rq is about to be mixed merged.  Make sure the attributes
 617  *     which can be mixed are set in each bio and mark @rq as mixed
 618  *     merged.
 619  */
 620 void blk_rq_set_mixed_merge(struct request *rq)
 621 {
 622         unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
 623         struct bio *bio;
 624
 625         if (rq->rq_flags & RQF_MIXED_MERGE)
 626                 return;
 627
 628         /*
 629          * @rq will no longer represent mixable attributes for all the
 630          * contained bios.  It will just track those of the first one.
 631          * Distributes the attributs to each bio.
 632          */
 633         for (bio = rq->bio; bio; bio = bio->bi_next) {
 634                 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) &&
 635                              (bio->bi_opf & REQ_FAILFAST_MASK) != ff);
 636                 bio->bi_opf |= ff;
 637         }
 638         rq->rq_flags |= RQF_MIXED_MERGE;
 639 }
 640
 641 static void blk_account_io_merge(struct request *req)
 642 {
 643         if (blk_do_io_stat(req)) {
 644                 struct hd_struct *part;
 645                 int cpu;
 646
 647                 cpu = part_stat_lock();
 648                 part = req->part;
 649
 650                 part_round_stats(req->q, cpu, part);
 651                 part_dec_in_flight(req->q, part, rq_data_dir(req));
 652
 653                 hd_struct_put(part);
 654                 part_stat_unlock();
 655         }
 656 }
 657 /*
 658  * Two cases of handling DISCARD merge:
 659  * If max_discard_segments > 1, the driver takes every bio
 660  * as a range and send them to controller together. The ranges
 661  * needn't to be contiguous.
 662  * Otherwise, the bios/requests will be handled as same as
 663  * others which should be contiguous.
 664  */
 665 static inline bool blk_discard_mergable(struct request *req)
 666 {
 667         if (req_op(req) == REQ_OP_DISCARD &&
 668             queue_max_discard_segments(req->q) > 1)
 669                 return true;
 670         return false;
 671 }
 672
 673 enum elv_merge blk_try_req_merge(struct request *req, struct request *next)
 674 {
 675         if (blk_discard_mergable(req))
 676                 return ELEVATOR_DISCARD_MERGE;
 677         else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next))
 678                 return ELEVATOR_BACK_MERGE;
 679
 680         return ELEVATOR_NO_MERGE;
 681 }
 682
 683 /*
 684  * For non-mq, this has to be called with the request spinlock acquired.
 685  * For mq with scheduling, the appropriate queue wide lock should be held.
 686  */
 687 static struct request *attempt_merge(struct request_queue *q,
 688                                      struct request *req, struct request *next)
 689 {
 690         if (!q->mq_ops)
 691                 lockdep_assert_held(q->queue_lock);
 692
 693         if (!rq_mergeable(req) || !rq_mergeable(next))
 694                 return NULL;
 695
 696         if (req_op(req) != req_op(next))
 697                 return NULL;
 698
 699         if (rq_data_dir(req) != rq_data_dir(next)
 700             || req->rq_disk != next->rq_disk
 701             || req_no_special_merge(next))
 702                 return NULL;
 703
 704         if (req_op(req) == REQ_OP_WRITE_SAME &&
 705             !blk_write_same_mergeable(req->bio, next->bio))
 706                 return NULL;
 707
 708         /*
 709          * Don't allow merge of different write hints, or for a hint with
 710          * non-hint IO.
 711          */
 712         if (req->write_hint != next->write_hint)
 713                 return NULL;
 714
 715         /*
 716          * If we are allowed to merge, then append bio list
 717          * from next to rq and release next. merge_requests_fn
 718          * will have updated segment counts, update sector
 719          * counts here. Handle DISCARDs separately, as they
 720          * have separate settings.
 721          */
 722
 723         switch (blk_try_req_merge(req, next)) {
 724         case ELEVATOR_DISCARD_MERGE:
 725                 if (!req_attempt_discard_merge(q, req, next))
 726                         return NULL;
 727                 break;
 728         case ELEVATOR_BACK_MERGE:
 729                 if (!ll_merge_requests_fn(q, req, next))
 730                         return NULL;
 731                 break;
 732         default:
 733                 return NULL;
 734         }
 735
 736         /*
 737          * If failfast settings disagree or any of the two is already
 738          * a mixed merge, mark both as mixed before proceeding.  This
 739          * makes sure that all involved bios have mixable attributes
 740          * set properly.
 741          */
 742         if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) ||
 743             (req->cmd_flags & REQ_FAILFAST_MASK) !=
 744             (next->cmd_flags & REQ_FAILFAST_MASK)) {
 745                 blk_rq_set_mixed_merge(req);
 746                 blk_rq_set_mixed_merge(next);
 747         }
 748
 749         /*
 750          * At this point we have either done a back merge
 751          * or front merge. We need the smaller start_time of
 752          * the merged requests to be the current request
 753          * for accounting purposes.
 754          */
 755         if (time_after(req->start_time, next->start_time))
 756                 req->start_time = next->start_time;
 757
 758         req->biotail->bi_next = next->bio;
 759         req->biotail = next->biotail;
 760
 761         req->__data_len += blk_rq_bytes(next);
 762
 763         if (!blk_discard_mergable(req))
 764                 elv_merge_requests(q, req, next);
 765
 766         /*
 767          * 'next' is going away, so update stats accordingly
 768          */
 769         blk_account_io_merge(next);
 770
 771         req->ioprio = ioprio_best(req->ioprio, next->ioprio);
 772         if (blk_rq_cpu_valid(next))
 773                 req->cpu = next->cpu;
 774
 775         /*
 776          * ownership of bio passed from next to req, return 'next' for
 777          * the caller to free
 778          */
 779         next->bio = NULL;
 780         return next;
 781 }
 782
 783 struct request *attempt_back_merge(struct request_queue *q, struct request *rq)
 784 {
 785         struct request *next = elv_latter_request(q, rq);
 786
 787         if (next)
 788                 return attempt_merge(q, rq, next);
 789
 790         return NULL;
 791 }
 792
 793 struct request *attempt_front_merge(struct request_queue *q, struct request *rq)
 794 {
 795         struct request *prev = elv_former_request(q, rq);
 796
 797         if (prev)
 798                 return attempt_merge(q, prev, rq);
 799
 800         return NULL;
 801 }
 802
 803 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
 804                           struct request *next)
 805 {
 806         struct elevator_queue *e = q->elevator;
 807         struct request *free;
 808
 809         if (!e->uses_mq && e->type->ops.sq.elevator_allow_rq_merge_fn)
 810                 if (!e->type->ops.sq.elevator_allow_rq_merge_fn(q, rq, next))
 811                         return 0;
 812
 813         free = attempt_merge(q, rq, next);
 814         if (free) {
 815                 __blk_put_request(q, free);
 816                 return 1;
 817         }
 818
 819         return 0;
 820 }
 821
 822 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 823 {
 824         if (!rq_mergeable(rq) || !bio_mergeable(bio))
 825                 return false;
 826
 827         if (req_op(rq) != bio_op(bio))
 828                 return false;
 829
 830         /* different data direction or already started, don't merge */
 831         if (bio_data_dir(bio) != rq_data_dir(rq))
 832                 return false;
 833
 834         /* must be same device and not a special request */
 835         if (rq->rq_disk != bio->bi_disk || req_no_special_merge(rq))
 836                 return false;
 837
 838         /* only merge integrity protected bio into ditto rq */
 839         if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
 840                 return false;
 841
 842         /* must be using the same buffer */
 843         if (req_op(rq) == REQ_OP_WRITE_SAME &&
 844             !blk_write_same_mergeable(rq->bio, bio))
 845                 return false;
 846
 847         /*
 848          * Don't allow merge of different write hints, or for a hint with
 849          * non-hint IO.
 850          */
 851         if (rq->write_hint != bio->bi_write_hint)
 852                 return false;
 853
 854         return true;
 855 }
 856
 857 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
 858 {
 859         if (blk_discard_mergable(rq))
 860                 return ELEVATOR_DISCARD_MERGE;
 861         else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
 862                 return ELEVATOR_BACK_MERGE;
 863         else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
 864                 return ELEVATOR_FRONT_MERGE;
 865         return ELEVATOR_NO_MERGE;
 866 }