block/blk-merge.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Functions related to segment and merge handling
   4  */
   5 #include <linux/kernel.h>
   6 #include <linux/module.h>
   7 #include <linux/bio.h>
   8 #include <linux/blkdev.h>
   9 #include <linux/scatterlist.h>
  10
  11 #include <trace/events/block.h>
  12
  13 #include "blk.h"
  14
  15 /*
  16  * Check if the two bvecs from two bios can be merged to one segment.  If yes,
  17  * no need to check gap between the two bios since the 1st bio and the 1st bvec
  18  * in the 2nd bio can be handled in one segment.
  19  */
  20 static inline bool bios_segs_mergeable(struct request_queue *q,
  21                 struct bio *prev, struct bio_vec *prev_last_bv,
  22                 struct bio_vec *next_first_bv)
  23 {
  24         if (!biovec_phys_mergeable(q, prev_last_bv, next_first_bv))
  25                 return false;
  26         if (prev->bi_seg_back_size + next_first_bv->bv_len >
  27                         queue_max_segment_size(q))
  28                 return false;
  29         return true;
  30 }
  31
  32 static inline bool bio_will_gap(struct request_queue *q,
  33                 struct request *prev_rq, struct bio *prev, struct bio *next)
  34 {
  35         struct bio_vec pb, nb;
  36
  37         if (!bio_has_data(prev) || !queue_virt_boundary(q))
  38                 return false;
  39
  40         /*
  41          * Don't merge if the 1st bio starts with non-zero offset, otherwise it
  42          * is quite difficult to respect the sg gap limit.  We work hard to
  43          * merge a huge number of small single bios in case of mkfs.
  44          */
  45         if (prev_rq)
  46                 bio_get_first_bvec(prev_rq->bio, &pb);
  47         else
  48                 bio_get_first_bvec(prev, &pb);
  49         if (pb.bv_offset & queue_virt_boundary(q))
  50                 return true;
  51
  52         /*
  53          * We don't need to worry about the situation that the merged segment
  54          * ends in unaligned virt boundary:
  55          *
  56          * - if 'pb' ends aligned, the merged segment ends aligned
  57          * - if 'pb' ends unaligned, the next bio must include
  58          *   one single bvec of 'nb', otherwise the 'nb' can't
  59          *   merge with 'pb'
  60          */
  61         bio_get_last_bvec(prev, &pb);
  62         bio_get_first_bvec(next, &nb);
  63         if (bios_segs_mergeable(q, prev, &pb, &nb))
  64                 return false;
  65         return __bvec_gap_to_prev(q, &pb, nb.bv_offset);
  66 }
  67
  68 static inline bool req_gap_back_merge(struct request *req, struct bio *bio)
  69 {
  70         return bio_will_gap(req->q, req, req->biotail, bio);
  71 }
  72
  73 static inline bool req_gap_front_merge(struct request *req, struct bio *bio)
  74 {
  75         return bio_will_gap(req->q, NULL, bio, req->bio);
  76 }
  77
  78 static struct bio *blk_bio_discard_split(struct request_queue *q,
  79                                          struct bio *bio,
  80                                          struct bio_set *bs,
  81                                          unsigned *nsegs)
  82 {
  83         unsigned int max_discard_sectors, granularity;
  84         int alignment;
  85         sector_t tmp;
  86         unsigned split_sectors;
  87
  88         *nsegs = 1;
  89
  90         /* Zero-sector (unknown) and one-sector granularities are the same.  */
  91         granularity = max(q->limits.discard_granularity >> 9, 1U);
  92
  93         max_discard_sectors = min(q->limits.max_discard_sectors,
  94                         bio_allowed_max_sectors(q));
  95         max_discard_sectors -= max_discard_sectors % granularity;
  96
  97         if (unlikely(!max_discard_sectors)) {
  98                 /* XXX: warn */
  99                 return NULL;
 100         }
 101
 102         if (bio_sectors(bio) <= max_discard_sectors)
 103                 return NULL;
 104
 105         split_sectors = max_discard_sectors;
 106
 107         /*
 108          * If the next starting sector would be misaligned, stop the discard at
 109          * the previous aligned sector.
 110          */
 111         alignment = (q->limits.discard_alignment >> 9) % granularity;
 112
 113         tmp = bio->bi_iter.bi_sector + split_sectors - alignment;
 114         tmp = sector_div(tmp, granularity);
 115
 116         if (split_sectors > tmp)
 117                 split_sectors -= tmp;
 118
 119         return bio_split(bio, split_sectors, GFP_NOIO, bs);
 120 }
 121
 122 static struct bio *blk_bio_write_zeroes_split(struct request_queue *q,
 123                 struct bio *bio, struct bio_set *bs, unsigned *nsegs)
 124 {
 125         *nsegs = 1;
 126
 127         if (!q->limits.max_write_zeroes_sectors)
 128                 return NULL;
 129
 130         if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors)
 131                 return NULL;
 132
 133         return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs);
 134 }
 135
 136 static struct bio *blk_bio_write_same_split(struct request_queue *q,
 137                                             struct bio *bio,
 138                                             struct bio_set *bs,
 139                                             unsigned *nsegs)
 140 {
 141         *nsegs = 1;
 142
 143         if (!q->limits.max_write_same_sectors)
 144                 return NULL;
 145
 146         if (bio_sectors(bio) <= q->limits.max_write_same_sectors)
 147                 return NULL;
 148
 149         return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
 150 }
 151
 152 static inline unsigned get_max_io_size(struct request_queue *q,
 153                                        struct bio *bio)
 154 {
 155         unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);
 156         unsigned mask = queue_logical_block_size(q) - 1;
 157
 158         /* aligned to logical block size */
 159         sectors &= ~(mask >> 9);
 160
 161         return sectors;
 162 }
 163
 164 static unsigned get_max_segment_size(struct request_queue *q,
 165                                      unsigned offset)
 166 {
 167         unsigned long mask = queue_segment_boundary(q);
 168
 169         /* default segment boundary mask means no boundary limit */
 170         if (mask == BLK_SEG_BOUNDARY_MASK)
 171                 return queue_max_segment_size(q);
 172
 173         return min_t(unsigned long, mask - (mask & offset) + 1,
 174                      queue_max_segment_size(q));
 175 }
 176
 177 /*
 178  * Split the bvec @bv into segments, and update all kinds of
 179  * variables.
 180  */
 181 static bool bvec_split_segs(struct request_queue *q, struct bio_vec *bv,
 182                 unsigned *nsegs, unsigned *last_seg_size,
 183                 unsigned *front_seg_size, unsigned *sectors, unsigned max_segs)
 184 {
 185         unsigned len = bv->bv_len;
 186         unsigned total_len = 0;
 187         unsigned new_nsegs = 0, seg_size = 0;
 188
 189         /*
 190          * Multi-page bvec may be too big to hold in one segment, so the
 191          * current bvec has to be splitted as multiple segments.
 192          */
 193         while (len && new_nsegs + *nsegs < max_segs) {
 194                 seg_size = get_max_segment_size(q, bv->bv_offset + total_len);
 195                 seg_size = min(seg_size, len);
 196
 197                 new_nsegs++;
 198                 total_len += seg_size;
 199                 len -= seg_size;
 200
 201                 if ((bv->bv_offset + total_len) & queue_virt_boundary(q))
 202                         break;
 203         }
 204
 205         if (!new_nsegs)
 206                 return !!len;
 207
 208         /* update front segment size */
 209         if (!*nsegs) {
 210                 unsigned first_seg_size;
 211
 212                 if (new_nsegs == 1)
 213                         first_seg_size = get_max_segment_size(q, bv->bv_offset);
 214                 else
 215                         first_seg_size = queue_max_segment_size(q);
 216
 217                 if (*front_seg_size < first_seg_size)
 218                         *front_seg_size = first_seg_size;
 219         }
 220
 221         /* update other varibles */
 222         *last_seg_size = seg_size;
 223         *nsegs += new_nsegs;
 224         if (sectors)
 225                 *sectors += total_len >> 9;
 226
 227         /* split in the middle of the bvec if len != 0 */
 228         return !!len;
 229 }
 230
 231 static struct bio *blk_bio_segment_split(struct request_queue *q,
 232                                          struct bio *bio,
 233                                          struct bio_set *bs,
 234                                          unsigned *segs)
 235 {
 236         struct bio_vec bv, bvprv, *bvprvp = NULL;
 237         struct bvec_iter iter;
 238         unsigned seg_size = 0, nsegs = 0, sectors = 0;
 239         unsigned front_seg_size = bio->bi_seg_front_size;
 240         bool do_split = true;
 241         struct bio *new = NULL;
 242         const unsigned max_sectors = get_max_io_size(q, bio);
 243         const unsigned max_segs = queue_max_segments(q);
 244
 245         bio_for_each_bvec(bv, bio, iter) {
 246                 /*
 247                  * If the queue doesn't support SG gaps and adding this
 248                  * offset would create a gap, disallow it.
 249                  */
 250                 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
 251                         goto split;
 252
 253                 if (sectors + (bv.bv_len >> 9) > max_sectors) {
 254                         /*
 255                          * Consider this a new segment if we're splitting in
 256                          * the middle of this vector.
 257                          */
 258                         if (nsegs < max_segs &&
 259                             sectors < max_sectors) {
 260                                 /* split in the middle of bvec */
 261                                 bv.bv_len = (max_sectors - sectors) << 9;
 262                                 bvec_split_segs(q, &bv, &nsegs,
 263                                                 &seg_size,
 264                                                 &front_seg_size,
 265                                                 &sectors, max_segs);
 266                         }
 267                         goto split;
 268                 }
 269
 270                 if (bvprvp) {
 271                         if (seg_size + bv.bv_len > queue_max_segment_size(q))
 272                                 goto new_segment;
 273                         if (!biovec_phys_mergeable(q, bvprvp, &bv))
 274                                 goto new_segment;
 275
 276                         seg_size += bv.bv_len;
 277                         bvprv = bv;
 278                         bvprvp = &bvprv;
 279                         sectors += bv.bv_len >> 9;
 280
 281                         if (nsegs == 1 && seg_size > front_seg_size)
 282                                 front_seg_size = seg_size;
 283
 284                         continue;
 285                 }
 286 new_segment:
 287                 if (nsegs == max_segs)
 288                         goto split;
 289
 290                 bvprv = bv;
 291                 bvprvp = &bvprv;
 292
 293                 if (bv.bv_offset + bv.bv_len <= PAGE_SIZE) {
 294                         nsegs++;
 295                         seg_size = bv.bv_len;
 296                         sectors += bv.bv_len >> 9;
 297                         if (nsegs == 1 && seg_size > front_seg_size)
 298                                 front_seg_size = seg_size;
 299                 } else if (bvec_split_segs(q, &bv, &nsegs, &seg_size,
 300                                     &front_seg_size, &sectors, max_segs)) {
 301                         goto split;
 302                 }
 303         }
 304
 305         do_split = false;
 306 split:
 307         *segs = nsegs;
 308
 309         if (do_split) {
 310                 new = bio_split(bio, sectors, GFP_NOIO, bs);
 311                 if (new)
 312                         bio = new;
 313         }
 314
 315         bio->bi_seg_front_size = front_seg_size;
 316         if (seg_size > bio->bi_seg_back_size)
 317                 bio->bi_seg_back_size = seg_size;
 318
 319         return do_split ? new : NULL;
 320 }
 321
 322 void blk_queue_split(struct request_queue *q, struct bio **bio)
 323 {
 324         struct bio *split, *res;
 325         unsigned nsegs;
 326
 327         switch (bio_op(*bio)) {
 328         case REQ_OP_DISCARD:
 329         case REQ_OP_SECURE_ERASE:
 330                 split = blk_bio_discard_split(q, *bio, &q->bio_split, &nsegs);
 331                 break;
 332         case REQ_OP_WRITE_ZEROES:
 333                 split = blk_bio_write_zeroes_split(q, *bio, &q->bio_split, &nsegs);
 334                 break;
 335         case REQ_OP_WRITE_SAME:
 336                 split = blk_bio_write_same_split(q, *bio, &q->bio_split, &nsegs);
 337                 break;
 338         default:
 339                 split = blk_bio_segment_split(q, *bio, &q->bio_split, &nsegs);
 340                 break;
 341         }
 342
 343         /* physical segments can be figured out during splitting */
 344         res = split ? split : *bio;
 345         res->bi_phys_segments = nsegs;
 346         bio_set_flag(res, BIO_SEG_VALID);
 347
 348         if (split) {
 349                 /* there isn't chance to merge the splitted bio */
 350                 split->bi_opf |= REQ_NOMERGE;
 351
 352                 /*
 353                  * Since we're recursing into make_request here, ensure
 354                  * that we mark this bio as already having entered the queue.
 355                  * If not, and the queue is going away, we can get stuck
 356                  * forever on waiting for the queue reference to drop. But
 357                  * that will never happen, as we're already holding a
 358                  * reference to it.
 359                  */
 360                 bio_set_flag(*bio, BIO_QUEUE_ENTERED);
 361
 362                 bio_chain(split, *bio);
 363                 trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
 364                 generic_make_request(*bio);
 365                 *bio = split;
 366         }
 367 }
 368 EXPORT_SYMBOL(blk_queue_split);
 369
 370 static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
 371                                              struct bio *bio)
 372 {
 373         struct bio_vec bv, bvprv = { NULL };
 374         int prev = 0;
 375         unsigned int seg_size, nr_phys_segs;
 376         unsigned front_seg_size;
 377         struct bio *fbio, *bbio;
 378         struct bvec_iter iter;
 379
 380         if (!bio)
 381                 return 0;
 382
 383         front_seg_size = bio->bi_seg_front_size;
 384
 385         switch (bio_op(bio)) {
 386         case REQ_OP_DISCARD:
 387         case REQ_OP_SECURE_ERASE:
 388         case REQ_OP_WRITE_ZEROES:
 389                 return 0;
 390         case REQ_OP_WRITE_SAME:
 391                 return 1;
 392         }
 393
 394         fbio = bio;
 395         seg_size = 0;
 396         nr_phys_segs = 0;
 397         for_each_bio(bio) {
 398                 bio_for_each_bvec(bv, bio, iter) {
 399                         if (prev) {
 400                                 if (seg_size + bv.bv_len
 401                                     > queue_max_segment_size(q))
 402                                         goto new_segment;
 403                                 if (!biovec_phys_mergeable(q, &bvprv, &bv))
 404                                         goto new_segment;
 405
 406                                 seg_size += bv.bv_len;
 407                                 bvprv = bv;
 408
 409                                 if (nr_phys_segs == 1 && seg_size >
 410                                                 front_seg_size)
 411                                         front_seg_size = seg_size;
 412
 413                                 continue;
 414                         }
 415 new_segment:
 416                         bvprv = bv;
 417                         prev = 1;
 418                         bvec_split_segs(q, &bv, &nr_phys_segs, &seg_size,
 419                                         &front_seg_size, NULL, UINT_MAX);
 420                 }
 421                 bbio = bio;
 422         }
 423
 424         fbio->bi_seg_front_size = front_seg_size;
 425         if (seg_size > bbio->bi_seg_back_size)
 426                 bbio->bi_seg_back_size = seg_size;
 427
 428         return nr_phys_segs;
 429 }
 430
 431 void blk_recalc_rq_segments(struct request *rq)
 432 {
 433         rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
 434 }
 435
 436 void blk_recount_segments(struct request_queue *q, struct bio *bio)
 437 {
 438         struct bio *nxt = bio->bi_next;
 439
 440         bio->bi_next = NULL;
 441         bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio);
 442         bio->bi_next = nxt;
 443
 444         bio_set_flag(bio, BIO_SEG_VALID);
 445 }
 446
 447 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
 448                                    struct bio *nxt)
 449 {
 450         struct bio_vec end_bv = { NULL }, nxt_bv;
 451
 452         if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
 453             queue_max_segment_size(q))
 454                 return 0;
 455
 456         if (!bio_has_data(bio))
 457                 return 1;
 458
 459         bio_get_last_bvec(bio, &end_bv);
 460         bio_get_first_bvec(nxt, &nxt_bv);
 461
 462         return biovec_phys_mergeable(q, &end_bv, &nxt_bv);
 463 }
 464
 465 static inline struct scatterlist *blk_next_sg(struct scatterlist **sg,
 466                 struct scatterlist *sglist)
 467 {
 468         if (!*sg)
 469                 return sglist;
 470
 471         /*
 472          * If the driver previously mapped a shorter list, we could see a
 473          * termination bit prematurely unless it fully inits the sg table
 474          * on each mapping. We KNOW that there must be more entries here
 475          * or the driver would be buggy, so force clear the termination bit
 476          * to avoid doing a full sg_init_table() in drivers for each command.
 477          */
 478         sg_unmark_end(*sg);
 479         return sg_next(*sg);
 480 }
 481
 482 static unsigned blk_bvec_map_sg(struct request_queue *q,
 483                 struct bio_vec *bvec, struct scatterlist *sglist,
 484                 struct scatterlist **sg)
 485 {
 486         unsigned nbytes = bvec->bv_len;
 487         unsigned nsegs = 0, total = 0, offset = 0;
 488
 489         while (nbytes > 0) {
 490                 unsigned seg_size;
 491                 struct page *pg;
 492                 unsigned idx;
 493
 494                 *sg = blk_next_sg(sg, sglist);
 495
 496                 seg_size = get_max_segment_size(q, bvec->bv_offset + total);
 497                 seg_size = min(nbytes, seg_size);
 498
 499                 offset = (total + bvec->bv_offset) % PAGE_SIZE;
 500                 idx = (total + bvec->bv_offset) / PAGE_SIZE;
 501                 pg = bvec_nth_page(bvec->bv_page, idx);
 502
 503                 sg_set_page(*sg, pg, seg_size, offset);
 504
 505                 total += seg_size;
 506                 nbytes -= seg_size;
 507                 nsegs++;
 508         }
 509
 510         return nsegs;
 511 }
 512
 513 static inline void
 514 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
 515                      struct scatterlist *sglist, struct bio_vec *bvprv,
 516                      struct scatterlist **sg, int *nsegs)
 517 {
 518
 519         int nbytes = bvec->bv_len;
 520
 521         if (*sg) {
 522                 if ((*sg)->length + nbytes > queue_max_segment_size(q))
 523                         goto new_segment;
 524                 if (!biovec_phys_mergeable(q, bvprv, bvec))
 525                         goto new_segment;
 526
 527                 (*sg)->length += nbytes;
 528         } else {
 529 new_segment:
 530                 if (bvec->bv_offset + bvec->bv_len <= PAGE_SIZE) {
 531                         *sg = blk_next_sg(sg, sglist);
 532                         sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
 533                         (*nsegs) += 1;
 534                 } else
 535                         (*nsegs) += blk_bvec_map_sg(q, bvec, sglist, sg);
 536         }
 537         *bvprv = *bvec;
 538 }
 539
 540 static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv,
 541                 struct scatterlist *sglist, struct scatterlist **sg)
 542 {
 543         *sg = sglist;
 544         sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
 545         return 1;
 546 }
 547
 548 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
 549                              struct scatterlist *sglist,
 550                              struct scatterlist **sg)
 551 {
 552         struct bio_vec bvec, bvprv = { NULL };
 553         struct bvec_iter iter;
 554         int nsegs = 0;
 555
 556         for_each_bio(bio)
 557                 bio_for_each_bvec(bvec, bio, iter)
 558                         __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
 559                                              &nsegs);
 560
 561         return nsegs;
 562 }
 563
 564 /*
 565  * map a request to scatterlist, return number of sg entries setup. Caller
 566  * must make sure sg can hold rq->nr_phys_segments entries
 567  */
 568 int blk_rq_map_sg(struct request_queue *q, struct request *rq,
 569                   struct scatterlist *sglist)
 570 {
 571         struct scatterlist *sg = NULL;
 572         int nsegs = 0;
 573
 574         if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
 575                 nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg);
 576         else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME)
 577                 nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg);
 578         else if (rq->bio)
 579                 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
 580
 581         if (unlikely(rq->rq_flags & RQF_COPY_USER) &&
 582             (blk_rq_bytes(rq) & q->dma_pad_mask)) {
 583                 unsigned int pad_len =
 584                         (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
 585
 586                 sg->length += pad_len;
 587                 rq->extra_len += pad_len;
 588         }
 589
 590         if (q->dma_drain_size && q->dma_drain_needed(rq)) {
 591                 if (op_is_write(req_op(rq)))
 592                         memset(q->dma_drain_buffer, 0, q->dma_drain_size);
 593
 594                 sg_unmark_end(sg);
 595                 sg = sg_next(sg);
 596                 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
 597                             q->dma_drain_size,
 598                             ((unsigned long)q->dma_drain_buffer) &
 599                             (PAGE_SIZE - 1));
 600                 nsegs++;
 601                 rq->extra_len += q->dma_drain_size;
 602         }
 603
 604         if (sg)
 605                 sg_mark_end(sg);
 606
 607         /*
 608          * Something must have been wrong if the figured number of
 609          * segment is bigger than number of req's physical segments
 610          */
 611         WARN_ON(nsegs > blk_rq_nr_phys_segments(rq));
 612
 613         return nsegs;
 614 }
 615 EXPORT_SYMBOL(blk_rq_map_sg);
 616
 617 static inline int ll_new_hw_segment(struct request_queue *q,
 618                                     struct request *req,
 619                                     struct bio *bio)
 620 {
 621         int nr_phys_segs = bio_phys_segments(q, bio);
 622
 623         if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
 624                 goto no_merge;
 625
 626         if (blk_integrity_merge_bio(q, req, bio) == false)
 627                 goto no_merge;
 628
 629         /*
 630          * This will form the start of a new hw segment.  Bump both
 631          * counters.
 632          */
 633         req->nr_phys_segments += nr_phys_segs;
 634         return 1;
 635
 636 no_merge:
 637         req_set_nomerge(q, req);
 638         return 0;
 639 }
 640
 641 int ll_back_merge_fn(struct request_queue *q, struct request *req,
 642                      struct bio *bio)
 643 {
 644         if (req_gap_back_merge(req, bio))
 645                 return 0;
 646         if (blk_integrity_rq(req) &&
 647             integrity_req_gap_back_merge(req, bio))
 648                 return 0;
 649         if (blk_rq_sectors(req) + bio_sectors(bio) >
 650             blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
 651                 req_set_nomerge(q, req);
 652                 return 0;
 653         }
 654         if (!bio_flagged(req->biotail, BIO_SEG_VALID))
 655                 blk_recount_segments(q, req->biotail);
 656         if (!bio_flagged(bio, BIO_SEG_VALID))
 657                 blk_recount_segments(q, bio);
 658
 659         return ll_new_hw_segment(q, req, bio);
 660 }
 661
 662 int ll_front_merge_fn(struct request_queue *q, struct request *req,
 663                       struct bio *bio)
 664 {
 665
 666         if (req_gap_front_merge(req, bio))
 667                 return 0;
 668         if (blk_integrity_rq(req) &&
 669             integrity_req_gap_front_merge(req, bio))
 670                 return 0;
 671         if (blk_rq_sectors(req) + bio_sectors(bio) >
 672             blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
 673                 req_set_nomerge(q, req);
 674                 return 0;
 675         }
 676         if (!bio_flagged(bio, BIO_SEG_VALID))
 677                 blk_recount_segments(q, bio);
 678         if (!bio_flagged(req->bio, BIO_SEG_VALID))
 679                 blk_recount_segments(q, req->bio);
 680
 681         return ll_new_hw_segment(q, req, bio);
 682 }
 683
 684 static bool req_attempt_discard_merge(struct request_queue *q, struct request *req,
 685                 struct request *next)
 686 {
 687         unsigned short segments = blk_rq_nr_discard_segments(req);
 688
 689         if (segments >= queue_max_discard_segments(q))
 690                 goto no_merge;
 691         if (blk_rq_sectors(req) + bio_sectors(next->bio) >
 692             blk_rq_get_max_sectors(req, blk_rq_pos(req)))
 693                 goto no_merge;
 694
 695         req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next);
 696         return true;
 697 no_merge:
 698         req_set_nomerge(q, req);
 699         return false;
 700 }
 701
 702 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
 703                                 struct request *next)
 704 {
 705         int total_phys_segments;
 706         unsigned int seg_size =
 707                 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
 708
 709         if (req_gap_back_merge(req, next->bio))
 710                 return 0;
 711
 712         /*
 713          * Will it become too large?
 714          */
 715         if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
 716             blk_rq_get_max_sectors(req, blk_rq_pos(req)))
 717                 return 0;
 718
 719         total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
 720         if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
 721                 if (req->nr_phys_segments == 1)
 722                         req->bio->bi_seg_front_size = seg_size;
 723                 if (next->nr_phys_segments == 1)
 724                         next->biotail->bi_seg_back_size = seg_size;
 725                 total_phys_segments--;
 726         }
 727
 728         if (total_phys_segments > queue_max_segments(q))
 729                 return 0;
 730
 731         if (blk_integrity_merge_rq(q, req, next) == false)
 732                 return 0;
 733
 734         /* Merge is OK... */
 735         req->nr_phys_segments = total_phys_segments;
 736         return 1;
 737 }
 738
 739 /**
 740  * blk_rq_set_mixed_merge - mark a request as mixed merge
 741  * @rq: request to mark as mixed merge
 742  *
 743  * Description:
 744  *     @rq is about to be mixed merged.  Make sure the attributes
 745  *     which can be mixed are set in each bio and mark @rq as mixed
 746  *     merged.
 747  */
 748 void blk_rq_set_mixed_merge(struct request *rq)
 749 {
 750         unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
 751         struct bio *bio;
 752
 753         if (rq->rq_flags & RQF_MIXED_MERGE)
 754                 return;
 755
 756         /*
 757          * @rq will no longer represent mixable attributes for all the
 758          * contained bios.  It will just track those of the first one.
 759          * Distributes the attributs to each bio.
 760          */
 761         for (bio = rq->bio; bio; bio = bio->bi_next) {
 762                 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) &&
 763                              (bio->bi_opf & REQ_FAILFAST_MASK) != ff);
 764                 bio->bi_opf |= ff;
 765         }
 766         rq->rq_flags |= RQF_MIXED_MERGE;
 767 }
 768
 769 static void blk_account_io_merge(struct request *req)
 770 {
 771         if (blk_do_io_stat(req)) {
 772                 struct hd_struct *part;
 773
 774                 part_stat_lock();
 775                 part = req->part;
 776
 777                 part_dec_in_flight(req->q, part, rq_data_dir(req));
 778
 779                 hd_struct_put(part);
 780                 part_stat_unlock();
 781         }
 782 }
 783 /*
 784  * Two cases of handling DISCARD merge:
 785  * If max_discard_segments > 1, the driver takes every bio
 786  * as a range and send them to controller together. The ranges
 787  * needn't to be contiguous.
 788  * Otherwise, the bios/requests will be handled as same as
 789  * others which should be contiguous.
 790  */
 791 static inline bool blk_discard_mergable(struct request *req)
 792 {
 793         if (req_op(req) == REQ_OP_DISCARD &&
 794             queue_max_discard_segments(req->q) > 1)
 795                 return true;
 796         return false;
 797 }
 798
 799 static enum elv_merge blk_try_req_merge(struct request *req,
 800                                         struct request *next)
 801 {
 802         if (blk_discard_mergable(req))
 803                 return ELEVATOR_DISCARD_MERGE;
 804         else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next))
 805                 return ELEVATOR_BACK_MERGE;
 806
 807         return ELEVATOR_NO_MERGE;
 808 }
 809
 810 /*
 811  * For non-mq, this has to be called with the request spinlock acquired.
 812  * For mq with scheduling, the appropriate queue wide lock should be held.
 813  */
 814 static struct request *attempt_merge(struct request_queue *q,
 815                                      struct request *req, struct request *next)
 816 {
 817         if (!rq_mergeable(req) || !rq_mergeable(next))
 818                 return NULL;
 819
 820         if (req_op(req) != req_op(next))
 821                 return NULL;
 822
 823         if (rq_data_dir(req) != rq_data_dir(next)
 824             || req->rq_disk != next->rq_disk)
 825                 return NULL;
 826
 827         if (req_op(req) == REQ_OP_WRITE_SAME &&
 828             !blk_write_same_mergeable(req->bio, next->bio))
 829                 return NULL;
 830
 831         /*
 832          * Don't allow merge of different write hints, or for a hint with
 833          * non-hint IO.
 834          */
 835         if (req->write_hint != next->write_hint)
 836                 return NULL;
 837
 838         if (req->ioprio != next->ioprio)
 839                 return NULL;
 840
 841         /*
 842          * If we are allowed to merge, then append bio list
 843          * from next to rq and release next. merge_requests_fn
 844          * will have updated segment counts, update sector
 845          * counts here. Handle DISCARDs separately, as they
 846          * have separate settings.
 847          */
 848
 849         switch (blk_try_req_merge(req, next)) {
 850         case ELEVATOR_DISCARD_MERGE:
 851                 if (!req_attempt_discard_merge(q, req, next))
 852                         return NULL;
 853                 break;
 854         case ELEVATOR_BACK_MERGE:
 855                 if (!ll_merge_requests_fn(q, req, next))
 856                         return NULL;
 857                 break;
 858         default:
 859                 return NULL;
 860         }
 861
 862         /*
 863          * If failfast settings disagree or any of the two is already
 864          * a mixed merge, mark both as mixed before proceeding.  This
 865          * makes sure that all involved bios have mixable attributes
 866          * set properly.
 867          */
 868         if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) ||
 869             (req->cmd_flags & REQ_FAILFAST_MASK) !=
 870             (next->cmd_flags & REQ_FAILFAST_MASK)) {
 871                 blk_rq_set_mixed_merge(req);
 872                 blk_rq_set_mixed_merge(next);
 873         }
 874
 875         /*
 876          * At this point we have either done a back merge or front merge. We
 877          * need the smaller start_time_ns of the merged requests to be the
 878          * current request for accounting purposes.
 879          */
 880         if (next->start_time_ns < req->start_time_ns)
 881                 req->start_time_ns = next->start_time_ns;
 882
 883         req->biotail->bi_next = next->bio;
 884         req->biotail = next->biotail;
 885
 886         req->__data_len += blk_rq_bytes(next);
 887
 888         if (!blk_discard_mergable(req))
 889                 elv_merge_requests(q, req, next);
 890
 891         /*
 892          * 'next' is going away, so update stats accordingly
 893          */
 894         blk_account_io_merge(next);
 895
 896         /*
 897          * ownership of bio passed from next to req, return 'next' for
 898          * the caller to free
 899          */
 900         next->bio = NULL;
 901         return next;
 902 }
 903
 904 struct request *attempt_back_merge(struct request_queue *q, struct request *rq)
 905 {
 906         struct request *next = elv_latter_request(q, rq);
 907
 908         if (next)
 909                 return attempt_merge(q, rq, next);
 910
 911         return NULL;
 912 }
 913
 914 struct request *attempt_front_merge(struct request_queue *q, struct request *rq)
 915 {
 916         struct request *prev = elv_former_request(q, rq);
 917
 918         if (prev)
 919                 return attempt_merge(q, prev, rq);
 920
 921         return NULL;
 922 }
 923
 924 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
 925                           struct request *next)
 926 {
 927         struct request *free;
 928
 929         free = attempt_merge(q, rq, next);
 930         if (free) {
 931                 blk_put_request(free);
 932                 return 1;
 933         }
 934
 935         return 0;
 936 }
 937
 938 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 939 {
 940         if (!rq_mergeable(rq) || !bio_mergeable(bio))
 941                 return false;
 942
 943         if (req_op(rq) != bio_op(bio))
 944                 return false;
 945
 946         /* different data direction or already started, don't merge */
 947         if (bio_data_dir(bio) != rq_data_dir(rq))
 948                 return false;
 949
 950         /* must be same device */
 951         if (rq->rq_disk != bio->bi_disk)
 952                 return false;
 953
 954         /* only merge integrity protected bio into ditto rq */
 955         if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
 956                 return false;
 957
 958         /* must be using the same buffer */
 959         if (req_op(rq) == REQ_OP_WRITE_SAME &&
 960             !blk_write_same_mergeable(rq->bio, bio))
 961                 return false;
 962
 963         /*
 964          * Don't allow merge of different write hints, or for a hint with
 965          * non-hint IO.
 966          */
 967         if (rq->write_hint != bio->bi_write_hint)
 968                 return false;
 969
 970         if (rq->ioprio != bio_prio(bio))
 971                 return false;
 972
 973         return true;
 974 }
 975
 976 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
 977 {
 978         if (blk_discard_mergable(rq))
 979                 return ELEVATOR_DISCARD_MERGE;
 980         else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
 981                 return ELEVATOR_BACK_MERGE;
 982         else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
 983                 return ELEVATOR_FRONT_MERGE;
 984         return ELEVATOR_NO_MERGE;
 985 }