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 struct bio *blk_bio_segment_split(struct request_queue *q,
 165                                          struct bio *bio,
 166                                          struct bio_set *bs,
 167                                          unsigned *segs)
 168 {
 169         struct bio_vec bv, bvprv, *bvprvp = NULL;
 170         struct bvec_iter iter;
 171         unsigned seg_size = 0, nsegs = 0, sectors = 0;
 172         unsigned front_seg_size = bio->bi_seg_front_size;
 173         bool do_split = true;
 174         struct bio *new = NULL;
 175         const unsigned max_sectors = get_max_io_size(q, bio);
 176
 177         bio_for_each_segment(bv, bio, iter) {
 178                 /*
 179                  * If the queue doesn't support SG gaps and adding this
 180                  * offset would create a gap, disallow it.
 181                  */
 182                 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
 183                         goto split;
 184
 185                 if (sectors + (bv.bv_len >> 9) > max_sectors) {
 186                         /*
 187                          * Consider this a new segment if we're splitting in
 188                          * the middle of this vector.
 189                          */
 190                         if (nsegs < queue_max_segments(q) &&
 191                             sectors < max_sectors) {
 192                                 nsegs++;
 193                                 sectors = max_sectors;
 194                         }
 195                         goto split;
 196                 }
 197
 198                 if (bvprvp) {
 199                         if (seg_size + bv.bv_len > queue_max_segment_size(q))
 200                                 goto new_segment;
 201                         if (!biovec_phys_mergeable(q, bvprvp, &bv))
 202                                 goto new_segment;
 203
 204                         seg_size += bv.bv_len;
 205                         bvprv = bv;
 206                         bvprvp = &bvprv;
 207                         sectors += bv.bv_len >> 9;
 208
 209                         continue;
 210                 }
 211 new_segment:
 212                 if (nsegs == queue_max_segments(q))
 213                         goto split;
 214
 215                 if (nsegs == 1 && seg_size > front_seg_size)
 216                         front_seg_size = seg_size;
 217
 218                 nsegs++;
 219                 bvprv = bv;
 220                 bvprvp = &bvprv;
 221                 seg_size = bv.bv_len;
 222                 sectors += bv.bv_len >> 9;
 223
 224         }
 225
 226         do_split = false;
 227 split:
 228         *segs = nsegs;
 229
 230         if (do_split) {
 231                 new = bio_split(bio, sectors, GFP_NOIO, bs);
 232                 if (new)
 233                         bio = new;
 234         }
 235
 236         if (nsegs == 1 && seg_size > front_seg_size)
 237                 front_seg_size = seg_size;
 238         bio->bi_seg_front_size = front_seg_size;
 239         if (seg_size > bio->bi_seg_back_size)
 240                 bio->bi_seg_back_size = seg_size;
 241
 242         return do_split ? new : NULL;
 243 }
 244
 245 void blk_queue_split(struct request_queue *q, struct bio **bio)
 246 {
 247         struct bio *split, *res;
 248         unsigned nsegs;
 249
 250         switch (bio_op(*bio)) {
 251         case REQ_OP_DISCARD:
 252         case REQ_OP_SECURE_ERASE:
 253                 split = blk_bio_discard_split(q, *bio, &q->bio_split, &nsegs);
 254                 break;
 255         case REQ_OP_WRITE_ZEROES:
 256                 split = blk_bio_write_zeroes_split(q, *bio, &q->bio_split, &nsegs);
 257                 break;
 258         case REQ_OP_WRITE_SAME:
 259                 split = blk_bio_write_same_split(q, *bio, &q->bio_split, &nsegs);
 260                 break;
 261         default:
 262                 split = blk_bio_segment_split(q, *bio, &q->bio_split, &nsegs);
 263                 break;
 264         }
 265
 266         /* physical segments can be figured out during splitting */
 267         res = split ? split : *bio;
 268         res->bi_phys_segments = nsegs;
 269         bio_set_flag(res, BIO_SEG_VALID);
 270
 271         if (split) {
 272                 /* there isn't chance to merge the splitted bio */
 273                 split->bi_opf |= REQ_NOMERGE;
 274
 275                 bio_chain(split, *bio);
 276                 trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
 277                 generic_make_request(*bio);
 278                 *bio = split;
 279         }
 280 }
 281 EXPORT_SYMBOL(blk_queue_split);
 282
 283 static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
 284                                              struct bio *bio,
 285                                              bool no_sg_merge)
 286 {
 287         struct bio_vec bv, bvprv = { NULL };
 288         int prev = 0;
 289         unsigned int seg_size, nr_phys_segs;
 290         struct bio *fbio, *bbio;
 291         struct bvec_iter iter;
 292
 293         if (!bio)
 294                 return 0;
 295
 296         switch (bio_op(bio)) {
 297         case REQ_OP_DISCARD:
 298         case REQ_OP_SECURE_ERASE:
 299         case REQ_OP_WRITE_ZEROES:
 300                 return 0;
 301         case REQ_OP_WRITE_SAME:
 302                 return 1;
 303         }
 304
 305         fbio = bio;
 306         seg_size = 0;
 307         nr_phys_segs = 0;
 308         for_each_bio(bio) {
 309                 bio_for_each_segment(bv, bio, iter) {
 310                         /*
 311                          * If SG merging is disabled, each bio vector is
 312                          * a segment
 313                          */
 314                         if (no_sg_merge)
 315                                 goto new_segment;
 316
 317                         if (prev) {
 318                                 if (seg_size + bv.bv_len
 319                                     > queue_max_segment_size(q))
 320                                         goto new_segment;
 321                                 if (!biovec_phys_mergeable(q, &bvprv, &bv))
 322                                         goto new_segment;
 323
 324                                 seg_size += bv.bv_len;
 325                                 bvprv = bv;
 326                                 continue;
 327                         }
 328 new_segment:
 329                         if (nr_phys_segs == 1 && seg_size >
 330                             fbio->bi_seg_front_size)
 331                                 fbio->bi_seg_front_size = seg_size;
 332
 333                         nr_phys_segs++;
 334                         bvprv = bv;
 335                         prev = 1;
 336                         seg_size = bv.bv_len;
 337                 }
 338                 bbio = bio;
 339         }
 340
 341         if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
 342                 fbio->bi_seg_front_size = seg_size;
 343         if (seg_size > bbio->bi_seg_back_size)
 344                 bbio->bi_seg_back_size = seg_size;
 345
 346         return nr_phys_segs;
 347 }
 348
 349 void blk_recalc_rq_segments(struct request *rq)
 350 {
 351         bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
 352                         &rq->q->queue_flags);
 353
 354         rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio,
 355                         no_sg_merge);
 356 }
 357
 358 void blk_recount_segments(struct request_queue *q, struct bio *bio)
 359 {
 360         unsigned short seg_cnt;
 361
 362         /* estimate segment number by bi_vcnt for non-cloned bio */
 363         if (bio_flagged(bio, BIO_CLONED))
 364                 seg_cnt = bio_segments(bio);
 365         else
 366                 seg_cnt = bio->bi_vcnt;
 367
 368         if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
 369                         (seg_cnt < queue_max_segments(q)))
 370                 bio->bi_phys_segments = seg_cnt;
 371         else {
 372                 struct bio *nxt = bio->bi_next;
 373
 374                 bio->bi_next = NULL;
 375                 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
 376                 bio->bi_next = nxt;
 377         }
 378
 379         bio_set_flag(bio, BIO_SEG_VALID);
 380 }
 381
 382 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
 383                                    struct bio *nxt)
 384 {
 385         struct bio_vec end_bv = { NULL }, nxt_bv;
 386
 387         if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
 388             queue_max_segment_size(q))
 389                 return 0;
 390
 391         if (!bio_has_data(bio))
 392                 return 1;
 393
 394         bio_get_last_bvec(bio, &end_bv);
 395         bio_get_first_bvec(nxt, &nxt_bv);
 396
 397         return biovec_phys_mergeable(q, &end_bv, &nxt_bv);
 398 }
 399
 400 static inline void
 401 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
 402                      struct scatterlist *sglist, struct bio_vec *bvprv,
 403                      struct scatterlist **sg, int *nsegs)
 404 {
 405
 406         int nbytes = bvec->bv_len;
 407
 408         if (*sg) {
 409                 if ((*sg)->length + nbytes > queue_max_segment_size(q))
 410                         goto new_segment;
 411                 if (!biovec_phys_mergeable(q, bvprv, bvec))
 412                         goto new_segment;
 413
 414                 (*sg)->length += nbytes;
 415         } else {
 416 new_segment:
 417                 if (!*sg)
 418                         *sg = sglist;
 419                 else {
 420                         /*
 421                          * If the driver previously mapped a shorter
 422                          * list, we could see a termination bit
 423                          * prematurely unless it fully inits the sg
 424                          * table on each mapping. We KNOW that there
 425                          * must be more entries here or the driver
 426                          * would be buggy, so force clear the
 427                          * termination bit to avoid doing a full
 428                          * sg_init_table() in drivers for each command.
 429                          */
 430                         sg_unmark_end(*sg);
 431                         *sg = sg_next(*sg);
 432                 }
 433
 434                 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
 435                 (*nsegs)++;
 436         }
 437         *bvprv = *bvec;
 438 }
 439
 440 static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv,
 441                 struct scatterlist *sglist, struct scatterlist **sg)
 442 {
 443         *sg = sglist;
 444         sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
 445         return 1;
 446 }
 447
 448 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
 449                              struct scatterlist *sglist,
 450                              struct scatterlist **sg)
 451 {
 452         struct bio_vec bvec, bvprv = { NULL };
 453         struct bvec_iter iter;
 454         int nsegs = 0;
 455
 456         for_each_bio(bio)
 457                 bio_for_each_segment(bvec, bio, iter)
 458                         __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
 459                                              &nsegs);
 460
 461         return nsegs;
 462 }
 463
 464 /*
 465  * map a request to scatterlist, return number of sg entries setup. Caller
 466  * must make sure sg can hold rq->nr_phys_segments entries
 467  */
 468 int blk_rq_map_sg(struct request_queue *q, struct request *rq,
 469                   struct scatterlist *sglist)
 470 {
 471         struct scatterlist *sg = NULL;
 472         int nsegs = 0;
 473
 474         if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
 475                 nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg);
 476         else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME)
 477                 nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg);
 478         else if (rq->bio)
 479                 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
 480
 481         if (unlikely(rq->rq_flags & RQF_COPY_USER) &&
 482             (blk_rq_bytes(rq) & q->dma_pad_mask)) {
 483                 unsigned int pad_len =
 484                         (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
 485
 486                 sg->length += pad_len;
 487                 rq->extra_len += pad_len;
 488         }
 489
 490         if (q->dma_drain_size && q->dma_drain_needed(rq)) {
 491                 if (op_is_write(req_op(rq)))
 492                         memset(q->dma_drain_buffer, 0, q->dma_drain_size);
 493
 494                 sg_unmark_end(sg);
 495                 sg = sg_next(sg);
 496                 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
 497                             q->dma_drain_size,
 498                             ((unsigned long)q->dma_drain_buffer) &
 499                             (PAGE_SIZE - 1));
 500                 nsegs++;
 501                 rq->extra_len += q->dma_drain_size;
 502         }
 503
 504         if (sg)
 505                 sg_mark_end(sg);
 506
 507         /*
 508          * Something must have been wrong if the figured number of
 509          * segment is bigger than number of req's physical segments
 510          */
 511         WARN_ON(nsegs > blk_rq_nr_phys_segments(rq));
 512
 513         return nsegs;
 514 }
 515 EXPORT_SYMBOL(blk_rq_map_sg);
 516
 517 static inline int ll_new_hw_segment(struct request_queue *q,
 518                                     struct request *req,
 519                                     struct bio *bio)
 520 {
 521         int nr_phys_segs = bio_phys_segments(q, bio);
 522
 523         if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
 524                 goto no_merge;
 525
 526         if (blk_integrity_merge_bio(q, req, bio) == false)
 527                 goto no_merge;
 528
 529         /*
 530          * This will form the start of a new hw segment.  Bump both
 531          * counters.
 532          */
 533         req->nr_phys_segments += nr_phys_segs;
 534         return 1;
 535
 536 no_merge:
 537         req_set_nomerge(q, req);
 538         return 0;
 539 }
 540
 541 int ll_back_merge_fn(struct request_queue *q, struct request *req,
 542                      struct bio *bio)
 543 {
 544         if (req_gap_back_merge(req, bio))
 545                 return 0;
 546         if (blk_integrity_rq(req) &&
 547             integrity_req_gap_back_merge(req, bio))
 548                 return 0;
 549         if (blk_rq_sectors(req) + bio_sectors(bio) >
 550             blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
 551                 req_set_nomerge(q, req);
 552                 return 0;
 553         }
 554         if (!bio_flagged(req->biotail, BIO_SEG_VALID))
 555                 blk_recount_segments(q, req->biotail);
 556         if (!bio_flagged(bio, BIO_SEG_VALID))
 557                 blk_recount_segments(q, bio);
 558
 559         return ll_new_hw_segment(q, req, bio);
 560 }
 561
 562 int ll_front_merge_fn(struct request_queue *q, struct request *req,
 563                       struct bio *bio)
 564 {
 565
 566         if (req_gap_front_merge(req, bio))
 567                 return 0;
 568         if (blk_integrity_rq(req) &&
 569             integrity_req_gap_front_merge(req, bio))
 570                 return 0;
 571         if (blk_rq_sectors(req) + bio_sectors(bio) >
 572             blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
 573                 req_set_nomerge(q, req);
 574                 return 0;
 575         }
 576         if (!bio_flagged(bio, BIO_SEG_VALID))
 577                 blk_recount_segments(q, bio);
 578         if (!bio_flagged(req->bio, BIO_SEG_VALID))
 579                 blk_recount_segments(q, req->bio);
 580
 581         return ll_new_hw_segment(q, req, bio);
 582 }
 583
 584 static bool req_attempt_discard_merge(struct request_queue *q, struct request *req,
 585                 struct request *next)
 586 {
 587         unsigned short segments = blk_rq_nr_discard_segments(req);
 588
 589         if (segments >= queue_max_discard_segments(q))
 590                 goto no_merge;
 591         if (blk_rq_sectors(req) + bio_sectors(next->bio) >
 592             blk_rq_get_max_sectors(req, blk_rq_pos(req)))
 593                 goto no_merge;
 594
 595         req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next);
 596         return true;
 597 no_merge:
 598         req_set_nomerge(q, req);
 599         return false;
 600 }
 601
 602 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
 603                                 struct request *next)
 604 {
 605         int total_phys_segments;
 606         unsigned int seg_size =
 607                 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
 608
 609         if (req_gap_back_merge(req, next->bio))
 610                 return 0;
 611
 612         /*
 613          * Will it become too large?
 614          */
 615         if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
 616             blk_rq_get_max_sectors(req, blk_rq_pos(req)))
 617                 return 0;
 618
 619         total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
 620         if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
 621                 if (req->nr_phys_segments == 1)
 622                         req->bio->bi_seg_front_size = seg_size;
 623                 if (next->nr_phys_segments == 1)
 624                         next->biotail->bi_seg_back_size = seg_size;
 625                 total_phys_segments--;
 626         }
 627
 628         if (total_phys_segments > queue_max_segments(q))
 629                 return 0;
 630
 631         if (blk_integrity_merge_rq(q, req, next) == false)
 632                 return 0;
 633
 634         /* Merge is OK... */
 635         req->nr_phys_segments = total_phys_segments;
 636         return 1;
 637 }
 638
 639 /**
 640  * blk_rq_set_mixed_merge - mark a request as mixed merge
 641  * @rq: request to mark as mixed merge
 642  *
 643  * Description:
 644  *     @rq is about to be mixed merged.  Make sure the attributes
 645  *     which can be mixed are set in each bio and mark @rq as mixed
 646  *     merged.
 647  */
 648 void blk_rq_set_mixed_merge(struct request *rq)
 649 {
 650         unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
 651         struct bio *bio;
 652
 653         if (rq->rq_flags & RQF_MIXED_MERGE)
 654                 return;
 655
 656         /*
 657          * @rq will no longer represent mixable attributes for all the
 658          * contained bios.  It will just track those of the first one.
 659          * Distributes the attributs to each bio.
 660          */
 661         for (bio = rq->bio; bio; bio = bio->bi_next) {
 662                 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) &&
 663                              (bio->bi_opf & REQ_FAILFAST_MASK) != ff);
 664                 bio->bi_opf |= ff;
 665         }
 666         rq->rq_flags |= RQF_MIXED_MERGE;
 667 }
 668
 669 static void blk_account_io_merge(struct request *req)
 670 {
 671         if (blk_do_io_stat(req)) {
 672                 struct hd_struct *part;
 673
 674                 part_stat_lock();
 675                 part = req->part;
 676
 677                 part_dec_in_flight(req->q, part, rq_data_dir(req));
 678
 679                 hd_struct_put(part);
 680                 part_stat_unlock();
 681         }
 682 }
 683 /*
 684  * Two cases of handling DISCARD merge:
 685  * If max_discard_segments > 1, the driver takes every bio
 686  * as a range and send them to controller together. The ranges
 687  * needn't to be contiguous.
 688  * Otherwise, the bios/requests will be handled as same as
 689  * others which should be contiguous.
 690  */
 691 static inline bool blk_discard_mergable(struct request *req)
 692 {
 693         if (req_op(req) == REQ_OP_DISCARD &&
 694             queue_max_discard_segments(req->q) > 1)
 695                 return true;
 696         return false;
 697 }
 698
 699 static enum elv_merge blk_try_req_merge(struct request *req,
 700                                         struct request *next)
 701 {
 702         if (blk_discard_mergable(req))
 703                 return ELEVATOR_DISCARD_MERGE;
 704         else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next))
 705                 return ELEVATOR_BACK_MERGE;
 706
 707         return ELEVATOR_NO_MERGE;
 708 }
 709
 710 /*
 711  * For non-mq, this has to be called with the request spinlock acquired.
 712  * For mq with scheduling, the appropriate queue wide lock should be held.
 713  */
 714 static struct request *attempt_merge(struct request_queue *q,
 715                                      struct request *req, struct request *next)
 716 {
 717         if (!rq_mergeable(req) || !rq_mergeable(next))
 718                 return NULL;
 719
 720         if (req_op(req) != req_op(next))
 721                 return NULL;
 722
 723         if (rq_data_dir(req) != rq_data_dir(next)
 724             || req->rq_disk != next->rq_disk)
 725                 return NULL;
 726
 727         if (req_op(req) == REQ_OP_WRITE_SAME &&
 728             !blk_write_same_mergeable(req->bio, next->bio))
 729                 return NULL;
 730
 731         /*
 732          * Don't allow merge of different write hints, or for a hint with
 733          * non-hint IO.
 734          */
 735         if (req->write_hint != next->write_hint)
 736                 return NULL;
 737
 738         if (req->ioprio != next->ioprio)
 739                 return NULL;
 740
 741         /*
 742          * If we are allowed to merge, then append bio list
 743          * from next to rq and release next. merge_requests_fn
 744          * will have updated segment counts, update sector
 745          * counts here. Handle DISCARDs separately, as they
 746          * have separate settings.
 747          */
 748
 749         switch (blk_try_req_merge(req, next)) {
 750         case ELEVATOR_DISCARD_MERGE:
 751                 if (!req_attempt_discard_merge(q, req, next))
 752                         return NULL;
 753                 break;
 754         case ELEVATOR_BACK_MERGE:
 755                 if (!ll_merge_requests_fn(q, req, next))
 756                         return NULL;
 757                 break;
 758         default:
 759                 return NULL;
 760         }
 761
 762         /*
 763          * If failfast settings disagree or any of the two is already
 764          * a mixed merge, mark both as mixed before proceeding.  This
 765          * makes sure that all involved bios have mixable attributes
 766          * set properly.
 767          */
 768         if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) ||
 769             (req->cmd_flags & REQ_FAILFAST_MASK) !=
 770             (next->cmd_flags & REQ_FAILFAST_MASK)) {
 771                 blk_rq_set_mixed_merge(req);
 772                 blk_rq_set_mixed_merge(next);
 773         }
 774
 775         /*
 776          * At this point we have either done a back merge or front merge. We
 777          * need the smaller start_time_ns of the merged requests to be the
 778          * current request for accounting purposes.
 779          */
 780         if (next->start_time_ns < req->start_time_ns)
 781                 req->start_time_ns = next->start_time_ns;
 782
 783         req->biotail->bi_next = next->bio;
 784         req->biotail = next->biotail;
 785
 786         req->__data_len += blk_rq_bytes(next);
 787
 788         if (!blk_discard_mergable(req))
 789                 elv_merge_requests(q, req, next);
 790
 791         /*
 792          * 'next' is going away, so update stats accordingly
 793          */
 794         blk_account_io_merge(next);
 795
 796         /*
 797          * ownership of bio passed from next to req, return 'next' for
 798          * the caller to free
 799          */
 800         next->bio = NULL;
 801         return next;
 802 }
 803
 804 struct request *attempt_back_merge(struct request_queue *q, struct request *rq)
 805 {
 806         struct request *next = elv_latter_request(q, rq);
 807
 808         if (next)
 809                 return attempt_merge(q, rq, next);
 810
 811         return NULL;
 812 }
 813
 814 struct request *attempt_front_merge(struct request_queue *q, struct request *rq)
 815 {
 816         struct request *prev = elv_former_request(q, rq);
 817
 818         if (prev)
 819                 return attempt_merge(q, prev, rq);
 820
 821         return NULL;
 822 }
 823
 824 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
 825                           struct request *next)
 826 {
 827         struct request *free;
 828
 829         free = attempt_merge(q, rq, next);
 830         if (free) {
 831                 blk_put_request(free);
 832                 return 1;
 833         }
 834
 835         return 0;
 836 }
 837
 838 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 839 {
 840         if (!rq_mergeable(rq) || !bio_mergeable(bio))
 841                 return false;
 842
 843         if (req_op(rq) != bio_op(bio))
 844                 return false;
 845
 846         /* different data direction or already started, don't merge */
 847         if (bio_data_dir(bio) != rq_data_dir(rq))
 848                 return false;
 849
 850         /* must be same device */
 851         if (rq->rq_disk != bio->bi_disk)
 852                 return false;
 853
 854         /* only merge integrity protected bio into ditto rq */
 855         if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
 856                 return false;
 857
 858         /* must be using the same buffer */
 859         if (req_op(rq) == REQ_OP_WRITE_SAME &&
 860             !blk_write_same_mergeable(rq->bio, bio))
 861                 return false;
 862
 863         /*
 864          * Don't allow merge of different write hints, or for a hint with
 865          * non-hint IO.
 866          */
 867         if (rq->write_hint != bio->bi_write_hint)
 868                 return false;
 869
 870         if (rq->ioprio != bio_prio(bio))
 871                 return false;
 872
 873         return true;
 874 }
 875
 876 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
 877 {
 878         if (blk_discard_mergable(rq))
 879                 return ELEVATOR_DISCARD_MERGE;
 880         else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
 881                 return ELEVATOR_BACK_MERGE;
 882         else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
 883                 return ELEVATOR_FRONT_MERGE;
 884         return ELEVATOR_NO_MERGE;
 885 }