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)
 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 < queue_max_segments(q)) {
 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
 244         bio_for_each_bvec(bv, bio, iter) {
 245                 /*
 246                  * If the queue doesn't support SG gaps and adding this
 247                  * offset would create a gap, disallow it.
 248                  */
 249                 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
 250                         goto split;
 251
 252                 if (sectors + (bv.bv_len >> 9) > max_sectors) {
 253                         /*
 254                          * Consider this a new segment if we're splitting in
 255                          * the middle of this vector.
 256                          */
 257                         if (nsegs < queue_max_segments(q) &&
 258                             sectors < max_sectors) {
 259                                 /* split in the middle of bvec */
 260                                 bv.bv_len = (max_sectors - sectors) << 9;
 261                                 bvec_split_segs(q, &bv, &nsegs,
 262                                                 &seg_size,
 263                                                 &front_seg_size,
 264                                                 &sectors);
 265                         }
 266                         goto split;
 267                 }
 268
 269                 if (bvprvp) {
 270                         if (seg_size + bv.bv_len > queue_max_segment_size(q))
 271                                 goto new_segment;
 272                         if (!biovec_phys_mergeable(q, bvprvp, &bv))
 273                                 goto new_segment;
 274
 275                         seg_size += bv.bv_len;
 276                         bvprv = bv;
 277                         bvprvp = &bvprv;
 278                         sectors += bv.bv_len >> 9;
 279
 280                         if (nsegs == 1 && seg_size > front_seg_size)
 281                                 front_seg_size = seg_size;
 282
 283                         continue;
 284                 }
 285 new_segment:
 286                 if (nsegs == queue_max_segments(q))
 287                         goto split;
 288
 289                 bvprv = bv;
 290                 bvprvp = &bvprv;
 291
 292                 if (bv.bv_offset + bv.bv_len <= PAGE_SIZE) {
 293                         nsegs++;
 294                         seg_size = bv.bv_len;
 295                         sectors += bv.bv_len >> 9;
 296                         if (nsegs == 1 && seg_size > front_seg_size)
 297                                 front_seg_size = seg_size;
 298                 } else if (bvec_split_segs(q, &bv, &nsegs, &seg_size,
 299                                     &front_seg_size, &sectors)) {
 300                         goto split;
 301                 }
 302         }
 303
 304         do_split = false;
 305 split:
 306         *segs = nsegs;
 307
 308         if (do_split) {
 309                 new = bio_split(bio, sectors, GFP_NOIO, bs);
 310                 if (new)
 311                         bio = new;
 312         }
 313
 314         bio->bi_seg_front_size = front_seg_size;
 315         if (seg_size > bio->bi_seg_back_size)
 316                 bio->bi_seg_back_size = seg_size;
 317
 318         return do_split ? new : NULL;
 319 }
 320
 321 void blk_queue_split(struct request_queue *q, struct bio **bio)
 322 {
 323         struct bio *split, *res;
 324         unsigned nsegs;
 325
 326         switch (bio_op(*bio)) {
 327         case REQ_OP_DISCARD:
 328         case REQ_OP_SECURE_ERASE:
 329                 split = blk_bio_discard_split(q, *bio, &q->bio_split, &nsegs);
 330                 break;
 331         case REQ_OP_WRITE_ZEROES:
 332                 split = blk_bio_write_zeroes_split(q, *bio, &q->bio_split, &nsegs);
 333                 break;
 334         case REQ_OP_WRITE_SAME:
 335                 split = blk_bio_write_same_split(q, *bio, &q->bio_split, &nsegs);
 336                 break;
 337         default:
 338                 split = blk_bio_segment_split(q, *bio, &q->bio_split, &nsegs);
 339                 break;
 340         }
 341
 342         /* physical segments can be figured out during splitting */
 343         res = split ? split : *bio;
 344         res->bi_phys_segments = nsegs;
 345         bio_set_flag(res, BIO_SEG_VALID);
 346
 347         if (split) {
 348                 /* there isn't chance to merge the splitted bio */
 349                 split->bi_opf |= REQ_NOMERGE;
 350
 351                 /*
 352                  * Since we're recursing into make_request here, ensure
 353                  * that we mark this bio as already having entered the queue.
 354                  * If not, and the queue is going away, we can get stuck
 355                  * forever on waiting for the queue reference to drop. But
 356                  * that will never happen, as we're already holding a
 357                  * reference to it.
 358                  */
 359                 bio_set_flag(*bio, BIO_QUEUE_ENTERED);
 360
 361                 bio_chain(split, *bio);
 362                 trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
 363                 generic_make_request(*bio);
 364                 *bio = split;
 365         }
 366 }
 367 EXPORT_SYMBOL(blk_queue_split);
 368
 369 static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
 370                                              struct bio *bio)
 371 {
 372         struct bio_vec bv, bvprv = { NULL };
 373         int prev = 0;
 374         unsigned int seg_size, nr_phys_segs;
 375         unsigned front_seg_size;
 376         struct bio *fbio, *bbio;
 377         struct bvec_iter iter;
 378
 379         if (!bio)
 380                 return 0;
 381
 382         front_seg_size = bio->bi_seg_front_size;
 383
 384         switch (bio_op(bio)) {
 385         case REQ_OP_DISCARD:
 386         case REQ_OP_SECURE_ERASE:
 387         case REQ_OP_WRITE_ZEROES:
 388                 return 0;
 389         case REQ_OP_WRITE_SAME:
 390                 return 1;
 391         }
 392
 393         fbio = bio;
 394         seg_size = 0;
 395         nr_phys_segs = 0;
 396         for_each_bio(bio) {
 397                 bio_for_each_bvec(bv, bio, iter) {
 398                         if (prev) {
 399                                 if (seg_size + bv.bv_len
 400                                     > queue_max_segment_size(q))
 401                                         goto new_segment;
 402                                 if (!biovec_phys_mergeable(q, &bvprv, &bv))
 403                                         goto new_segment;
 404
 405                                 seg_size += bv.bv_len;
 406                                 bvprv = bv;
 407
 408                                 if (nr_phys_segs == 1 && seg_size >
 409                                                 front_seg_size)
 410                                         front_seg_size = seg_size;
 411
 412                                 continue;
 413                         }
 414 new_segment:
 415                         bvprv = bv;
 416                         prev = 1;
 417                         bvec_split_segs(q, &bv, &nr_phys_segs, &seg_size,
 418                                         &front_seg_size, NULL);
 419                 }
 420                 bbio = bio;
 421         }
 422
 423         fbio->bi_seg_front_size = front_seg_size;
 424         if (seg_size > bbio->bi_seg_back_size)
 425                 bbio->bi_seg_back_size = seg_size;
 426
 427         return nr_phys_segs;
 428 }
 429
 430 void blk_recalc_rq_segments(struct request *rq)
 431 {
 432         rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
 433 }
 434
 435 void blk_recount_segments(struct request_queue *q, struct bio *bio)
 436 {
 437         struct bio *nxt = bio->bi_next;
 438
 439         bio->bi_next = NULL;
 440         bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio);
 441         bio->bi_next = nxt;
 442
 443         bio_set_flag(bio, BIO_SEG_VALID);
 444 }
 445
 446 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
 447                                    struct bio *nxt)
 448 {
 449         struct bio_vec end_bv = { NULL }, nxt_bv;
 450
 451         if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
 452             queue_max_segment_size(q))
 453                 return 0;
 454
 455         if (!bio_has_data(bio))
 456                 return 1;
 457
 458         bio_get_last_bvec(bio, &end_bv);
 459         bio_get_first_bvec(nxt, &nxt_bv);
 460
 461         return biovec_phys_mergeable(q, &end_bv, &nxt_bv);
 462 }
 463
 464 static inline struct scatterlist *blk_next_sg(struct scatterlist **sg,
 465                 struct scatterlist *sglist)
 466 {
 467         if (!*sg)
 468                 return sglist;
 469
 470         /*
 471          * If the driver previously mapped a shorter list, we could see a
 472          * termination bit prematurely unless it fully inits the sg table
 473          * on each mapping. We KNOW that there must be more entries here
 474          * or the driver would be buggy, so force clear the termination bit
 475          * to avoid doing a full sg_init_table() in drivers for each command.
 476          */
 477         sg_unmark_end(*sg);
 478         return sg_next(*sg);
 479 }
 480
 481 static unsigned blk_bvec_map_sg(struct request_queue *q,
 482                 struct bio_vec *bvec, struct scatterlist *sglist,
 483                 struct scatterlist **sg)
 484 {
 485         unsigned nbytes = bvec->bv_len;
 486         unsigned nsegs = 0, total = 0, offset = 0;
 487
 488         while (nbytes > 0) {
 489                 unsigned seg_size;
 490                 struct page *pg;
 491                 unsigned idx;
 492
 493                 *sg = blk_next_sg(sg, sglist);
 494
 495                 seg_size = get_max_segment_size(q, bvec->bv_offset + total);
 496                 seg_size = min(nbytes, seg_size);
 497
 498                 offset = (total + bvec->bv_offset) % PAGE_SIZE;
 499                 idx = (total + bvec->bv_offset) / PAGE_SIZE;
 500                 pg = bvec_nth_page(bvec->bv_page, idx);
 501
 502                 sg_set_page(*sg, pg, seg_size, offset);
 503
 504                 total += seg_size;
 505                 nbytes -= seg_size;
 506                 nsegs++;
 507         }
 508
 509         return nsegs;
 510 }
 511
 512 static inline void
 513 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
 514                      struct scatterlist *sglist, struct bio_vec *bvprv,
 515                      struct scatterlist **sg, int *nsegs)
 516 {
 517
 518         int nbytes = bvec->bv_len;
 519
 520         if (*sg) {
 521                 if ((*sg)->length + nbytes > queue_max_segment_size(q))
 522                         goto new_segment;
 523                 if (!biovec_phys_mergeable(q, bvprv, bvec))
 524                         goto new_segment;
 525
 526                 (*sg)->length += nbytes;
 527         } else {
 528 new_segment:
 529                 if (bvec->bv_offset + bvec->bv_len <= PAGE_SIZE) {
 530                         *sg = blk_next_sg(sg, sglist);
 531                         sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
 532                         (*nsegs) += 1;
 533                 } else
 534                         (*nsegs) += blk_bvec_map_sg(q, bvec, sglist, sg);
 535         }
 536         *bvprv = *bvec;
 537 }
 538
 539 static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv,
 540                 struct scatterlist *sglist, struct scatterlist **sg)
 541 {
 542         *sg = sglist;
 543         sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
 544         return 1;
 545 }
 546
 547 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
 548                              struct scatterlist *sglist,
 549                              struct scatterlist **sg)
 550 {
 551         struct bio_vec bvec, bvprv = { NULL };
 552         struct bvec_iter iter;
 553         int nsegs = 0;
 554
 555         for_each_bio(bio)
 556                 bio_for_each_bvec(bvec, bio, iter)
 557                         __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
 558                                              &nsegs);
 559
 560         return nsegs;
 561 }
 562
 563 /*
 564  * map a request to scatterlist, return number of sg entries setup. Caller
 565  * must make sure sg can hold rq->nr_phys_segments entries
 566  */
 567 int blk_rq_map_sg(struct request_queue *q, struct request *rq,
 568                   struct scatterlist *sglist)
 569 {
 570         struct scatterlist *sg = NULL;
 571         int nsegs = 0;
 572
 573         if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
 574                 nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg);
 575         else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME)
 576                 nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg);
 577         else if (rq->bio)
 578                 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
 579
 580         if (unlikely(rq->rq_flags & RQF_COPY_USER) &&
 581             (blk_rq_bytes(rq) & q->dma_pad_mask)) {
 582                 unsigned int pad_len =
 583                         (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
 584
 585                 sg->length += pad_len;
 586                 rq->extra_len += pad_len;
 587         }
 588
 589         if (q->dma_drain_size && q->dma_drain_needed(rq)) {
 590                 if (op_is_write(req_op(rq)))
 591                         memset(q->dma_drain_buffer, 0, q->dma_drain_size);
 592
 593                 sg_unmark_end(sg);
 594                 sg = sg_next(sg);
 595                 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
 596                             q->dma_drain_size,
 597                             ((unsigned long)q->dma_drain_buffer) &
 598                             (PAGE_SIZE - 1));
 599                 nsegs++;
 600                 rq->extra_len += q->dma_drain_size;
 601         }
 602
 603         if (sg)
 604                 sg_mark_end(sg);
 605
 606         /*
 607          * Something must have been wrong if the figured number of
 608          * segment is bigger than number of req's physical segments
 609          */
 610         WARN_ON(nsegs > blk_rq_nr_phys_segments(rq));
 611
 612         return nsegs;
 613 }
 614 EXPORT_SYMBOL(blk_rq_map_sg);
 615
 616 static inline int ll_new_hw_segment(struct request_queue *q,
 617                                     struct request *req,
 618                                     struct bio *bio)
 619 {
 620         int nr_phys_segs = bio_phys_segments(q, bio);
 621
 622         if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
 623                 goto no_merge;
 624
 625         if (blk_integrity_merge_bio(q, req, bio) == false)
 626                 goto no_merge;
 627
 628         /*
 629          * This will form the start of a new hw segment.  Bump both
 630          * counters.
 631          */
 632         req->nr_phys_segments += nr_phys_segs;
 633         return 1;
 634
 635 no_merge:
 636         req_set_nomerge(q, req);
 637         return 0;
 638 }
 639
 640 int ll_back_merge_fn(struct request_queue *q, struct request *req,
 641                      struct bio *bio)
 642 {
 643         if (req_gap_back_merge(req, bio))
 644                 return 0;
 645         if (blk_integrity_rq(req) &&
 646             integrity_req_gap_back_merge(req, bio))
 647                 return 0;
 648         if (blk_rq_sectors(req) + bio_sectors(bio) >
 649             blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
 650                 req_set_nomerge(q, req);
 651                 return 0;
 652         }
 653         if (!bio_flagged(req->biotail, BIO_SEG_VALID))
 654                 blk_recount_segments(q, req->biotail);
 655         if (!bio_flagged(bio, BIO_SEG_VALID))
 656                 blk_recount_segments(q, bio);
 657
 658         return ll_new_hw_segment(q, req, bio);
 659 }
 660
 661 int ll_front_merge_fn(struct request_queue *q, struct request *req,
 662                       struct bio *bio)
 663 {
 664
 665         if (req_gap_front_merge(req, bio))
 666                 return 0;
 667         if (blk_integrity_rq(req) &&
 668             integrity_req_gap_front_merge(req, bio))
 669                 return 0;
 670         if (blk_rq_sectors(req) + bio_sectors(bio) >
 671             blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
 672                 req_set_nomerge(q, req);
 673                 return 0;
 674         }
 675         if (!bio_flagged(bio, BIO_SEG_VALID))
 676                 blk_recount_segments(q, bio);
 677         if (!bio_flagged(req->bio, BIO_SEG_VALID))
 678                 blk_recount_segments(q, req->bio);
 679
 680         return ll_new_hw_segment(q, req, bio);
 681 }
 682
 683 static bool req_attempt_discard_merge(struct request_queue *q, struct request *req,
 684                 struct request *next)
 685 {
 686         unsigned short segments = blk_rq_nr_discard_segments(req);
 687
 688         if (segments >= queue_max_discard_segments(q))
 689                 goto no_merge;
 690         if (blk_rq_sectors(req) + bio_sectors(next->bio) >
 691             blk_rq_get_max_sectors(req, blk_rq_pos(req)))
 692                 goto no_merge;
 693
 694         req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next);
 695         return true;
 696 no_merge:
 697         req_set_nomerge(q, req);
 698         return false;
 699 }
 700
 701 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
 702                                 struct request *next)
 703 {
 704         int total_phys_segments;
 705         unsigned int seg_size =
 706                 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
 707
 708         if (req_gap_back_merge(req, next->bio))
 709                 return 0;
 710
 711         /*
 712          * Will it become too large?
 713          */
 714         if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
 715             blk_rq_get_max_sectors(req, blk_rq_pos(req)))
 716                 return 0;
 717
 718         total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
 719         if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
 720                 if (req->nr_phys_segments == 1)
 721                         req->bio->bi_seg_front_size = seg_size;
 722                 if (next->nr_phys_segments == 1)
 723                         next->biotail->bi_seg_back_size = seg_size;
 724                 total_phys_segments--;
 725         }
 726
 727         if (total_phys_segments > queue_max_segments(q))
 728                 return 0;
 729
 730         if (blk_integrity_merge_rq(q, req, next) == false)
 731                 return 0;
 732
 733         /* Merge is OK... */
 734         req->nr_phys_segments = total_phys_segments;
 735         return 1;
 736 }
 737
 738 /**
 739  * blk_rq_set_mixed_merge - mark a request as mixed merge
 740  * @rq: request to mark as mixed merge
 741  *
 742  * Description:
 743  *     @rq is about to be mixed merged.  Make sure the attributes
 744  *     which can be mixed are set in each bio and mark @rq as mixed
 745  *     merged.
 746  */
 747 void blk_rq_set_mixed_merge(struct request *rq)
 748 {
 749         unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
 750         struct bio *bio;
 751
 752         if (rq->rq_flags & RQF_MIXED_MERGE)
 753                 return;
 754
 755         /*
 756          * @rq will no longer represent mixable attributes for all the
 757          * contained bios.  It will just track those of the first one.
 758          * Distributes the attributs to each bio.
 759          */
 760         for (bio = rq->bio; bio; bio = bio->bi_next) {
 761                 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) &&
 762                              (bio->bi_opf & REQ_FAILFAST_MASK) != ff);
 763                 bio->bi_opf |= ff;
 764         }
 765         rq->rq_flags |= RQF_MIXED_MERGE;
 766 }
 767
 768 static void blk_account_io_merge(struct request *req)
 769 {
 770         if (blk_do_io_stat(req)) {
 771                 struct hd_struct *part;
 772
 773                 part_stat_lock();
 774                 part = req->part;
 775
 776                 part_dec_in_flight(req->q, part, rq_data_dir(req));
 777
 778                 hd_struct_put(part);
 779                 part_stat_unlock();
 780         }
 781 }
 782 /*
 783  * Two cases of handling DISCARD merge:
 784  * If max_discard_segments > 1, the driver takes every bio
 785  * as a range and send them to controller together. The ranges
 786  * needn't to be contiguous.
 787  * Otherwise, the bios/requests will be handled as same as
 788  * others which should be contiguous.
 789  */
 790 static inline bool blk_discard_mergable(struct request *req)
 791 {
 792         if (req_op(req) == REQ_OP_DISCARD &&
 793             queue_max_discard_segments(req->q) > 1)
 794                 return true;
 795         return false;
 796 }
 797
 798 static enum elv_merge blk_try_req_merge(struct request *req,
 799                                         struct request *next)
 800 {
 801         if (blk_discard_mergable(req))
 802                 return ELEVATOR_DISCARD_MERGE;
 803         else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next))
 804                 return ELEVATOR_BACK_MERGE;
 805
 806         return ELEVATOR_NO_MERGE;
 807 }
 808
 809 /*
 810  * For non-mq, this has to be called with the request spinlock acquired.
 811  * For mq with scheduling, the appropriate queue wide lock should be held.
 812  */
 813 static struct request *attempt_merge(struct request_queue *q,
 814                                      struct request *req, struct request *next)
 815 {
 816         if (!rq_mergeable(req) || !rq_mergeable(next))
 817                 return NULL;
 818
 819         if (req_op(req) != req_op(next))
 820                 return NULL;
 821
 822         if (rq_data_dir(req) != rq_data_dir(next)
 823             || req->rq_disk != next->rq_disk)
 824                 return NULL;
 825
 826         if (req_op(req) == REQ_OP_WRITE_SAME &&
 827             !blk_write_same_mergeable(req->bio, next->bio))
 828                 return NULL;
 829
 830         /*
 831          * Don't allow merge of different write hints, or for a hint with
 832          * non-hint IO.
 833          */
 834         if (req->write_hint != next->write_hint)
 835                 return NULL;
 836
 837         if (req->ioprio != next->ioprio)
 838                 return NULL;
 839
 840         /*
 841          * If we are allowed to merge, then append bio list
 842          * from next to rq and release next. merge_requests_fn
 843          * will have updated segment counts, update sector
 844          * counts here. Handle DISCARDs separately, as they
 845          * have separate settings.
 846          */
 847
 848         switch (blk_try_req_merge(req, next)) {
 849         case ELEVATOR_DISCARD_MERGE:
 850                 if (!req_attempt_discard_merge(q, req, next))
 851                         return NULL;
 852                 break;
 853         case ELEVATOR_BACK_MERGE:
 854                 if (!ll_merge_requests_fn(q, req, next))
 855                         return NULL;
 856                 break;
 857         default:
 858                 return NULL;
 859         }
 860
 861         /*
 862          * If failfast settings disagree or any of the two is already
 863          * a mixed merge, mark both as mixed before proceeding.  This
 864          * makes sure that all involved bios have mixable attributes
 865          * set properly.
 866          */
 867         if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) ||
 868             (req->cmd_flags & REQ_FAILFAST_MASK) !=
 869             (next->cmd_flags & REQ_FAILFAST_MASK)) {
 870                 blk_rq_set_mixed_merge(req);
 871                 blk_rq_set_mixed_merge(next);
 872         }
 873
 874         /*
 875          * At this point we have either done a back merge or front merge. We
 876          * need the smaller start_time_ns of the merged requests to be the
 877          * current request for accounting purposes.
 878          */
 879         if (next->start_time_ns < req->start_time_ns)
 880                 req->start_time_ns = next->start_time_ns;
 881
 882         req->biotail->bi_next = next->bio;
 883         req->biotail = next->biotail;
 884
 885         req->__data_len += blk_rq_bytes(next);
 886
 887         if (!blk_discard_mergable(req))
 888                 elv_merge_requests(q, req, next);
 889
 890         /*
 891          * 'next' is going away, so update stats accordingly
 892          */
 893         blk_account_io_merge(next);
 894
 895         /*
 896          * ownership of bio passed from next to req, return 'next' for
 897          * the caller to free
 898          */
 899         next->bio = NULL;
 900         return next;
 901 }
 902
 903 struct request *attempt_back_merge(struct request_queue *q, struct request *rq)
 904 {
 905         struct request *next = elv_latter_request(q, rq);
 906
 907         if (next)
 908                 return attempt_merge(q, rq, next);
 909
 910         return NULL;
 911 }
 912
 913 struct request *attempt_front_merge(struct request_queue *q, struct request *rq)
 914 {
 915         struct request *prev = elv_former_request(q, rq);
 916
 917         if (prev)
 918                 return attempt_merge(q, prev, rq);
 919
 920         return NULL;
 921 }
 922
 923 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
 924                           struct request *next)
 925 {
 926         struct request *free;
 927
 928         free = attempt_merge(q, rq, next);
 929         if (free) {
 930                 blk_put_request(free);
 931                 return 1;
 932         }
 933
 934         return 0;
 935 }
 936
 937 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 938 {
 939         if (!rq_mergeable(rq) || !bio_mergeable(bio))
 940                 return false;
 941
 942         if (req_op(rq) != bio_op(bio))
 943                 return false;
 944
 945         /* different data direction or already started, don't merge */
 946         if (bio_data_dir(bio) != rq_data_dir(rq))
 947                 return false;
 948
 949         /* must be same device */
 950         if (rq->rq_disk != bio->bi_disk)
 951                 return false;
 952
 953         /* only merge integrity protected bio into ditto rq */
 954         if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
 955                 return false;
 956
 957         /* must be using the same buffer */
 958         if (req_op(rq) == REQ_OP_WRITE_SAME &&
 959             !blk_write_same_mergeable(rq->bio, bio))
 960                 return false;
 961
 962         /*
 963          * Don't allow merge of different write hints, or for a hint with
 964          * non-hint IO.
 965          */
 966         if (rq->write_hint != bio->bi_write_hint)
 967                 return false;
 968
 969         if (rq->ioprio != bio_prio(bio))
 970                 return false;
 971
 972         return true;
 973 }
 974
 975 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
 976 {
 977         if (blk_discard_mergable(rq))
 978                 return ELEVATOR_DISCARD_MERGE;
 979         else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
 980                 return ELEVATOR_BACK_MERGE;
 981         else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
 982                 return ELEVATOR_FRONT_MERGE;
 983         return ELEVATOR_NO_MERGE;
 984 }