block/blk-merge.c

   1 /*
   2  * Functions related to segment and merge handling
   3  */
   4 #include <linux/kernel.h>
   5 #include <linux/module.h>
   6 #include <linux/bio.h>
   7 #include <linux/blkdev.h>
   8 #include <linux/scatterlist.h>
   9
  10 #include <trace/events/block.h>
  11
  12 #include "blk.h"
  13
  14 static struct bio *blk_bio_discard_split(struct request_queue *q,
  15                                          struct bio *bio,
  16                                          struct bio_set *bs,
  17                                          unsigned *nsegs)
  18 {
  19         unsigned int max_discard_sectors, granularity;
  20         int alignment;
  21         sector_t tmp;
  22         unsigned split_sectors;
  23
  24         *nsegs = 1;
  25
  26         /* Zero-sector (unknown) and one-sector granularities are the same.  */
  27         granularity = max(q->limits.discard_granularity >> 9, 1U);
  28
  29         max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
  30         max_discard_sectors -= max_discard_sectors % granularity;
  31
  32         if (unlikely(!max_discard_sectors)) {
  33                 /* XXX: warn */
  34                 return NULL;
  35         }
  36
  37         if (bio_sectors(bio) <= max_discard_sectors)
  38                 return NULL;
  39
  40         split_sectors = max_discard_sectors;
  41
  42         /*
  43          * If the next starting sector would be misaligned, stop the discard at
  44          * the previous aligned sector.
  45          */
  46         alignment = (q->limits.discard_alignment >> 9) % granularity;
  47
  48         tmp = bio->bi_iter.bi_sector + split_sectors - alignment;
  49         tmp = sector_div(tmp, granularity);
  50
  51         if (split_sectors > tmp)
  52                 split_sectors -= tmp;
  53
  54         return bio_split(bio, split_sectors, GFP_NOIO, bs);
  55 }
  56
  57 static struct bio *blk_bio_write_same_split(struct request_queue *q,
  58                                             struct bio *bio,
  59                                             struct bio_set *bs,
  60                                             unsigned *nsegs)
  61 {
  62         *nsegs = 1;
  63
  64         if (!q->limits.max_write_same_sectors)
  65                 return NULL;
  66
  67         if (bio_sectors(bio) <= q->limits.max_write_same_sectors)
  68                 return NULL;
  69
  70         return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
  71 }
  72
  73 static inline unsigned get_max_io_size(struct request_queue *q,
  74                                        struct bio *bio)
  75 {
  76         unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);
  77         unsigned mask = queue_logical_block_size(q) - 1;
  78
  79         /* aligned to logical block size */
  80         sectors &= ~(mask >> 9);
  81
  82         return sectors;
  83 }
  84
  85 static struct bio *blk_bio_segment_split(struct request_queue *q,
  86                                          struct bio *bio,
  87                                          struct bio_set *bs,
  88                                          unsigned *segs)
  89 {
  90         struct bio_vec bv, bvprv, *bvprvp = NULL;
  91         struct bvec_iter iter;
  92         unsigned seg_size = 0, nsegs = 0, sectors = 0;
  93         unsigned front_seg_size = bio->bi_seg_front_size;
  94         bool do_split = true;
  95         struct bio *new = NULL;
  96         const unsigned max_sectors = get_max_io_size(q, bio);
  97         unsigned bvecs = 0;
  98
  99         bio_for_each_segment(bv, bio, iter) {
 100                 /*
 101                  * With arbitrary bio size, the incoming bio may be very
 102                  * big. We have to split the bio into small bios so that
 103                  * each holds at most BIO_MAX_PAGES bvecs because
 104                  * bio_clone() can fail to allocate big bvecs.
 105                  *
 106                  * It should have been better to apply the limit per
 107                  * request queue in which bio_clone() is involved,
 108                  * instead of globally. The biggest blocker is the
 109                  * bio_clone() in bio bounce.
 110                  *
 111                  * If bio is splitted by this reason, we should have
 112                  * allowed to continue bios merging, but don't do
 113                  * that now for making the change simple.
 114                  *
 115                  * TODO: deal with bio bounce's bio_clone() gracefully
 116                  * and convert the global limit into per-queue limit.
 117                  */
 118                 if (bvecs++ >= BIO_MAX_PAGES)
 119                         goto split;
 120
 121                 /*
 122                  * If the queue doesn't support SG gaps and adding this
 123                  * offset would create a gap, disallow it.
 124                  */
 125                 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
 126                         goto split;
 127
 128                 if (sectors + (bv.bv_len >> 9) > max_sectors) {
 129                         /*
 130                          * Consider this a new segment if we're splitting in
 131                          * the middle of this vector.
 132                          */
 133                         if (nsegs < queue_max_segments(q) &&
 134                             sectors < max_sectors) {
 135                                 nsegs++;
 136                                 sectors = max_sectors;
 137                         }
 138                         if (sectors)
 139                                 goto split;
 140                         /* Make this single bvec as the 1st segment */
 141                 }
 142
 143                 if (bvprvp && blk_queue_cluster(q)) {
 144                         if (seg_size + bv.bv_len > queue_max_segment_size(q))
 145                                 goto new_segment;
 146                         if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv))
 147                                 goto new_segment;
 148                         if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv))
 149                                 goto new_segment;
 150
 151                         seg_size += bv.bv_len;
 152                         bvprv = bv;
 153                         bvprvp = &bvprv;
 154                         sectors += bv.bv_len >> 9;
 155
 156                         if (nsegs == 1 && seg_size > front_seg_size)
 157                                 front_seg_size = seg_size;
 158                         continue;
 159                 }
 160 new_segment:
 161                 if (nsegs == queue_max_segments(q))
 162                         goto split;
 163
 164                 nsegs++;
 165                 bvprv = bv;
 166                 bvprvp = &bvprv;
 167                 seg_size = bv.bv_len;
 168                 sectors += bv.bv_len >> 9;
 169
 170                 if (nsegs == 1 && seg_size > front_seg_size)
 171                         front_seg_size = seg_size;
 172         }
 173
 174         do_split = false;
 175 split:
 176         *segs = nsegs;
 177
 178         if (do_split) {
 179                 new = bio_split(bio, sectors, GFP_NOIO, bs);
 180                 if (new)
 181                         bio = new;
 182         }
 183
 184         bio->bi_seg_front_size = front_seg_size;
 185         if (seg_size > bio->bi_seg_back_size)
 186                 bio->bi_seg_back_size = seg_size;
 187
 188         return do_split ? new : NULL;
 189 }
 190
 191 void blk_queue_split(struct request_queue *q, struct bio **bio,
 192                      struct bio_set *bs)
 193 {
 194         struct bio *split, *res;
 195         unsigned nsegs;
 196
 197         switch (bio_op(*bio)) {
 198         case REQ_OP_DISCARD:
 199         case REQ_OP_SECURE_ERASE:
 200                 split = blk_bio_discard_split(q, *bio, bs, &nsegs);
 201                 break;
 202         case REQ_OP_WRITE_ZEROES:
 203                 split = NULL;
 204                 nsegs = (*bio)->bi_phys_segments;
 205                 break;
 206         case REQ_OP_WRITE_SAME:
 207                 split = blk_bio_write_same_split(q, *bio, bs, &nsegs);
 208                 break;
 209         default:
 210                 split = blk_bio_segment_split(q, *bio, q->bio_split, &nsegs);
 211                 break;
 212         }
 213
 214         /* physical segments can be figured out during splitting */
 215         res = split ? split : *bio;
 216         res->bi_phys_segments = nsegs;
 217         bio_set_flag(res, BIO_SEG_VALID);
 218
 219         if (split) {
 220                 /* there isn't chance to merge the splitted bio */
 221                 split->bi_opf |= REQ_NOMERGE;
 222
 223                 bio_chain(split, *bio);
 224                 trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
 225                 generic_make_request(*bio);
 226                 *bio = split;
 227         }
 228 }
 229 EXPORT_SYMBOL(blk_queue_split);
 230
 231 static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
 232                                              struct bio *bio,
 233                                              bool no_sg_merge)
 234 {
 235         struct bio_vec bv, bvprv = { NULL };
 236         int cluster, prev = 0;
 237         unsigned int seg_size, nr_phys_segs;
 238         struct bio *fbio, *bbio;
 239         struct bvec_iter iter;
 240
 241         if (!bio)
 242                 return 0;
 243
 244         /*
 245          * This should probably be returning 0, but blk_add_request_payload()
 246          * (Christoph!!!!)
 247          */
 248         switch (bio_op(bio)) {
 249         case REQ_OP_DISCARD:
 250         case REQ_OP_SECURE_ERASE:
 251         case REQ_OP_WRITE_SAME:
 252         case REQ_OP_WRITE_ZEROES:
 253                 return 1;
 254         default:
 255                 break;
 256         }
 257
 258         fbio = bio;
 259         cluster = blk_queue_cluster(q);
 260         seg_size = 0;
 261         nr_phys_segs = 0;
 262         for_each_bio(bio) {
 263                 bio_for_each_segment(bv, bio, iter) {
 264                         /*
 265                          * If SG merging is disabled, each bio vector is
 266                          * a segment
 267                          */
 268                         if (no_sg_merge)
 269                                 goto new_segment;
 270
 271                         if (prev && cluster) {
 272                                 if (seg_size + bv.bv_len
 273                                     > queue_max_segment_size(q))
 274                                         goto new_segment;
 275                                 if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv))
 276                                         goto new_segment;
 277                                 if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv))
 278                                         goto new_segment;
 279
 280                                 seg_size += bv.bv_len;
 281                                 bvprv = bv;
 282                                 continue;
 283                         }
 284 new_segment:
 285                         if (nr_phys_segs == 1 && seg_size >
 286                             fbio->bi_seg_front_size)
 287                                 fbio->bi_seg_front_size = seg_size;
 288
 289                         nr_phys_segs++;
 290                         bvprv = bv;
 291                         prev = 1;
 292                         seg_size = bv.bv_len;
 293                 }
 294                 bbio = bio;
 295         }
 296
 297         if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
 298                 fbio->bi_seg_front_size = seg_size;
 299         if (seg_size > bbio->bi_seg_back_size)
 300                 bbio->bi_seg_back_size = seg_size;
 301
 302         return nr_phys_segs;
 303 }
 304
 305 void blk_recalc_rq_segments(struct request *rq)
 306 {
 307         bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
 308                         &rq->q->queue_flags);
 309
 310         rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio,
 311                         no_sg_merge);
 312 }
 313
 314 void blk_recount_segments(struct request_queue *q, struct bio *bio)
 315 {
 316         unsigned short seg_cnt;
 317
 318         /* estimate segment number by bi_vcnt for non-cloned bio */
 319         if (bio_flagged(bio, BIO_CLONED))
 320                 seg_cnt = bio_segments(bio);
 321         else
 322                 seg_cnt = bio->bi_vcnt;
 323
 324         if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
 325                         (seg_cnt < queue_max_segments(q)))
 326                 bio->bi_phys_segments = seg_cnt;
 327         else {
 328                 struct bio *nxt = bio->bi_next;
 329
 330                 bio->bi_next = NULL;
 331                 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
 332                 bio->bi_next = nxt;
 333         }
 334
 335         bio_set_flag(bio, BIO_SEG_VALID);
 336 }
 337 EXPORT_SYMBOL(blk_recount_segments);
 338
 339 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
 340                                    struct bio *nxt)
 341 {
 342         struct bio_vec end_bv = { NULL }, nxt_bv;
 343
 344         if (!blk_queue_cluster(q))
 345                 return 0;
 346
 347         if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
 348             queue_max_segment_size(q))
 349                 return 0;
 350
 351         if (!bio_has_data(bio))
 352                 return 1;
 353
 354         bio_get_last_bvec(bio, &end_bv);
 355         bio_get_first_bvec(nxt, &nxt_bv);
 356
 357         if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv))
 358                 return 0;
 359
 360         /*
 361          * bio and nxt are contiguous in memory; check if the queue allows
 362          * these two to be merged into one
 363          */
 364         if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv))
 365                 return 1;
 366
 367         return 0;
 368 }
 369
 370 static inline void
 371 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
 372                      struct scatterlist *sglist, struct bio_vec *bvprv,
 373                      struct scatterlist **sg, int *nsegs, int *cluster)
 374 {
 375
 376         int nbytes = bvec->bv_len;
 377
 378         if (*sg && *cluster) {
 379                 if ((*sg)->length + nbytes > queue_max_segment_size(q))
 380                         goto new_segment;
 381
 382                 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
 383                         goto new_segment;
 384                 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
 385                         goto new_segment;
 386
 387                 (*sg)->length += nbytes;
 388         } else {
 389 new_segment:
 390                 if (!*sg)
 391                         *sg = sglist;
 392                 else {
 393                         /*
 394                          * If the driver previously mapped a shorter
 395                          * list, we could see a termination bit
 396                          * prematurely unless it fully inits the sg
 397                          * table on each mapping. We KNOW that there
 398                          * must be more entries here or the driver
 399                          * would be buggy, so force clear the
 400                          * termination bit to avoid doing a full
 401                          * sg_init_table() in drivers for each command.
 402                          */
 403                         sg_unmark_end(*sg);
 404                         *sg = sg_next(*sg);
 405                 }
 406
 407                 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
 408                 (*nsegs)++;
 409         }
 410         *bvprv = *bvec;
 411 }
 412
 413 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
 414                              struct scatterlist *sglist,
 415                              struct scatterlist **sg)
 416 {
 417         struct bio_vec bvec, bvprv = { NULL };
 418         struct bvec_iter iter;
 419         int nsegs, cluster;
 420
 421         nsegs = 0;
 422         cluster = blk_queue_cluster(q);
 423
 424         switch (bio_op(bio)) {
 425         case REQ_OP_DISCARD:
 426         case REQ_OP_SECURE_ERASE:
 427         case REQ_OP_WRITE_ZEROES:
 428                 /*
 429                  * This is a hack - drivers should be neither modifying the
 430                  * biovec, nor relying on bi_vcnt - but because of
 431                  * blk_add_request_payload(), a discard bio may or may not have
 432                  * a payload we need to set up here (thank you Christoph) and
 433                  * bi_vcnt is really the only way of telling if we need to.
 434                  */
 435                 if (!bio->bi_vcnt)
 436                         return 0;
 437                 /* Fall through */
 438         case REQ_OP_WRITE_SAME:
 439                 *sg = sglist;
 440                 bvec = bio_iovec(bio);
 441                 sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset);
 442                 return 1;
 443         default:
 444                 break;
 445         }
 446
 447         for_each_bio(bio)
 448                 bio_for_each_segment(bvec, bio, iter)
 449                         __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
 450                                              &nsegs, &cluster);
 451
 452         return nsegs;
 453 }
 454
 455 /*
 456  * map a request to scatterlist, return number of sg entries setup. Caller
 457  * must make sure sg can hold rq->nr_phys_segments entries
 458  */
 459 int blk_rq_map_sg(struct request_queue *q, struct request *rq,
 460                   struct scatterlist *sglist)
 461 {
 462         struct scatterlist *sg = NULL;
 463         int nsegs = 0;
 464
 465         if (rq->bio)
 466                 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
 467
 468         if (unlikely(rq->rq_flags & RQF_COPY_USER) &&
 469             (blk_rq_bytes(rq) & q->dma_pad_mask)) {
 470                 unsigned int pad_len =
 471                         (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
 472
 473                 sg->length += pad_len;
 474                 rq->extra_len += pad_len;
 475         }
 476
 477         if (q->dma_drain_size && q->dma_drain_needed(rq)) {
 478                 if (op_is_write(req_op(rq)))
 479                         memset(q->dma_drain_buffer, 0, q->dma_drain_size);
 480
 481                 sg_unmark_end(sg);
 482                 sg = sg_next(sg);
 483                 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
 484                             q->dma_drain_size,
 485                             ((unsigned long)q->dma_drain_buffer) &
 486                             (PAGE_SIZE - 1));
 487                 nsegs++;
 488                 rq->extra_len += q->dma_drain_size;
 489         }
 490
 491         if (sg)
 492                 sg_mark_end(sg);
 493
 494         /*
 495          * Something must have been wrong if the figured number of
 496          * segment is bigger than number of req's physical segments
 497          */
 498         WARN_ON(nsegs > rq->nr_phys_segments);
 499
 500         return nsegs;
 501 }
 502 EXPORT_SYMBOL(blk_rq_map_sg);
 503
 504 static inline int ll_new_hw_segment(struct request_queue *q,
 505                                     struct request *req,
 506                                     struct bio *bio)
 507 {
 508         int nr_phys_segs = bio_phys_segments(q, bio);
 509
 510         if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
 511                 goto no_merge;
 512
 513         if (blk_integrity_merge_bio(q, req, bio) == false)
 514                 goto no_merge;
 515
 516         /*
 517          * This will form the start of a new hw segment.  Bump both
 518          * counters.
 519          */
 520         req->nr_phys_segments += nr_phys_segs;
 521         return 1;
 522
 523 no_merge:
 524         req->cmd_flags |= REQ_NOMERGE;
 525         if (req == q->last_merge)
 526                 q->last_merge = NULL;
 527         return 0;
 528 }
 529
 530 int ll_back_merge_fn(struct request_queue *q, struct request *req,
 531                      struct bio *bio)
 532 {
 533         if (req_gap_back_merge(req, bio))
 534                 return 0;
 535         if (blk_integrity_rq(req) &&
 536             integrity_req_gap_back_merge(req, bio))
 537                 return 0;
 538         if (blk_rq_sectors(req) + bio_sectors(bio) >
 539             blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
 540                 req->cmd_flags |= REQ_NOMERGE;
 541                 if (req == q->last_merge)
 542                         q->last_merge = NULL;
 543                 return 0;
 544         }
 545         if (!bio_flagged(req->biotail, BIO_SEG_VALID))
 546                 blk_recount_segments(q, req->biotail);
 547         if (!bio_flagged(bio, BIO_SEG_VALID))
 548                 blk_recount_segments(q, bio);
 549
 550         return ll_new_hw_segment(q, req, bio);
 551 }
 552
 553 int ll_front_merge_fn(struct request_queue *q, struct request *req,
 554                       struct bio *bio)
 555 {
 556
 557         if (req_gap_front_merge(req, bio))
 558                 return 0;
 559         if (blk_integrity_rq(req) &&
 560             integrity_req_gap_front_merge(req, bio))
 561                 return 0;
 562         if (blk_rq_sectors(req) + bio_sectors(bio) >
 563             blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
 564                 req->cmd_flags |= REQ_NOMERGE;
 565                 if (req == q->last_merge)
 566                         q->last_merge = NULL;
 567                 return 0;
 568         }
 569         if (!bio_flagged(bio, BIO_SEG_VALID))
 570                 blk_recount_segments(q, bio);
 571         if (!bio_flagged(req->bio, BIO_SEG_VALID))
 572                 blk_recount_segments(q, req->bio);
 573
 574         return ll_new_hw_segment(q, req, bio);
 575 }
 576
 577 /*
 578  * blk-mq uses req->special to carry normal driver per-request payload, it
 579  * does not indicate a prepared command that we cannot merge with.
 580  */
 581 static bool req_no_special_merge(struct request *req)
 582 {
 583         struct request_queue *q = req->q;
 584
 585         return !q->mq_ops && req->special;
 586 }
 587
 588 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
 589                                 struct request *next)
 590 {
 591         int total_phys_segments;
 592         unsigned int seg_size =
 593                 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
 594
 595         /*
 596          * First check if the either of the requests are re-queued
 597          * requests.  Can't merge them if they are.
 598          */
 599         if (req_no_special_merge(req) || req_no_special_merge(next))
 600                 return 0;
 601
 602         if (req_gap_back_merge(req, next->bio))
 603                 return 0;
 604
 605         /*
 606          * Will it become too large?
 607          */
 608         if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
 609             blk_rq_get_max_sectors(req, blk_rq_pos(req)))
 610                 return 0;
 611
 612         total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
 613         if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
 614                 if (req->nr_phys_segments == 1)
 615                         req->bio->bi_seg_front_size = seg_size;
 616                 if (next->nr_phys_segments == 1)
 617                         next->biotail->bi_seg_back_size = seg_size;
 618                 total_phys_segments--;
 619         }
 620
 621         if (total_phys_segments > queue_max_segments(q))
 622                 return 0;
 623
 624         if (blk_integrity_merge_rq(q, req, next) == false)
 625                 return 0;
 626
 627         /* Merge is OK... */
 628         req->nr_phys_segments = total_phys_segments;
 629         return 1;
 630 }
 631
 632 /**
 633  * blk_rq_set_mixed_merge - mark a request as mixed merge
 634  * @rq: request to mark as mixed merge
 635  *
 636  * Description:
 637  *     @rq is about to be mixed merged.  Make sure the attributes
 638  *     which can be mixed are set in each bio and mark @rq as mixed
 639  *     merged.
 640  */
 641 void blk_rq_set_mixed_merge(struct request *rq)
 642 {
 643         unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
 644         struct bio *bio;
 645
 646         if (rq->rq_flags & RQF_MIXED_MERGE)
 647                 return;
 648
 649         /*
 650          * @rq will no longer represent mixable attributes for all the
 651          * contained bios.  It will just track those of the first one.
 652          * Distributes the attributs to each bio.
 653          */
 654         for (bio = rq->bio; bio; bio = bio->bi_next) {
 655                 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) &&
 656                              (bio->bi_opf & REQ_FAILFAST_MASK) != ff);
 657                 bio->bi_opf |= ff;
 658         }
 659         rq->rq_flags |= RQF_MIXED_MERGE;
 660 }
 661
 662 static void blk_account_io_merge(struct request *req)
 663 {
 664         if (blk_do_io_stat(req)) {
 665                 struct hd_struct *part;
 666                 int cpu;
 667
 668                 cpu = part_stat_lock();
 669                 part = req->part;
 670
 671                 part_round_stats(cpu, part);
 672                 part_dec_in_flight(part, rq_data_dir(req));
 673
 674                 hd_struct_put(part);
 675                 part_stat_unlock();
 676         }
 677 }
 678
 679 /*
 680  * Has to be called with the request spinlock acquired
 681  */
 682 static int attempt_merge(struct request_queue *q, struct request *req,
 683                           struct request *next)
 684 {
 685         if (!rq_mergeable(req) || !rq_mergeable(next))
 686                 return 0;
 687
 688         if (req_op(req) != req_op(next))
 689                 return 0;
 690
 691         /*
 692          * not contiguous
 693          */
 694         if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
 695                 return 0;
 696
 697         if (rq_data_dir(req) != rq_data_dir(next)
 698             || req->rq_disk != next->rq_disk
 699             || req_no_special_merge(next))
 700                 return 0;
 701
 702         if (req_op(req) == REQ_OP_WRITE_SAME &&
 703             !blk_write_same_mergeable(req->bio, next->bio))
 704                 return 0;
 705
 706         /*
 707          * If we are allowed to merge, then append bio list
 708          * from next to rq and release next. merge_requests_fn
 709          * will have updated segment counts, update sector
 710          * counts here.
 711          */
 712         if (!ll_merge_requests_fn(q, req, next))
 713                 return 0;
 714
 715         /*
 716          * If failfast settings disagree or any of the two is already
 717          * a mixed merge, mark both as mixed before proceeding.  This
 718          * makes sure that all involved bios have mixable attributes
 719          * set properly.
 720          */
 721         if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) ||
 722             (req->cmd_flags & REQ_FAILFAST_MASK) !=
 723             (next->cmd_flags & REQ_FAILFAST_MASK)) {
 724                 blk_rq_set_mixed_merge(req);
 725                 blk_rq_set_mixed_merge(next);
 726         }
 727
 728         /*
 729          * At this point we have either done a back merge
 730          * or front merge. We need the smaller start_time of
 731          * the merged requests to be the current request
 732          * for accounting purposes.
 733          */
 734         if (time_after(req->start_time, next->start_time))
 735                 req->start_time = next->start_time;
 736
 737         req->biotail->bi_next = next->bio;
 738         req->biotail = next->biotail;
 739
 740         req->__data_len += blk_rq_bytes(next);
 741
 742         elv_merge_requests(q, req, next);
 743
 744         /*
 745          * 'next' is going away, so update stats accordingly
 746          */
 747         blk_account_io_merge(next);
 748
 749         req->ioprio = ioprio_best(req->ioprio, next->ioprio);
 750         if (blk_rq_cpu_valid(next))
 751                 req->cpu = next->cpu;
 752
 753         /* owner-ship of bio passed from next to req */
 754         next->bio = NULL;
 755         __blk_put_request(q, next);
 756         return 1;
 757 }
 758
 759 int attempt_back_merge(struct request_queue *q, struct request *rq)
 760 {
 761         struct request *next = elv_latter_request(q, rq);
 762
 763         if (next)
 764                 return attempt_merge(q, rq, next);
 765
 766         return 0;
 767 }
 768
 769 int attempt_front_merge(struct request_queue *q, struct request *rq)
 770 {
 771         struct request *prev = elv_former_request(q, rq);
 772
 773         if (prev)
 774                 return attempt_merge(q, prev, rq);
 775
 776         return 0;
 777 }
 778
 779 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
 780                           struct request *next)
 781 {
 782         struct elevator_queue *e = q->elevator;
 783
 784         if (e->type->ops.elevator_allow_rq_merge_fn)
 785                 if (!e->type->ops.elevator_allow_rq_merge_fn(q, rq, next))
 786                         return 0;
 787
 788         return attempt_merge(q, rq, next);
 789 }
 790
 791 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 792 {
 793         if (!rq_mergeable(rq) || !bio_mergeable(bio))
 794                 return false;
 795
 796         if (req_op(rq) != bio_op(bio))
 797                 return false;
 798
 799         /* different data direction or already started, don't merge */
 800         if (bio_data_dir(bio) != rq_data_dir(rq))
 801                 return false;
 802
 803         /* must be same device and not a special request */
 804         if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq))
 805                 return false;
 806
 807         /* only merge integrity protected bio into ditto rq */
 808         if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
 809                 return false;
 810
 811         /* must be using the same buffer */
 812         if (req_op(rq) == REQ_OP_WRITE_SAME &&
 813             !blk_write_same_mergeable(rq->bio, bio))
 814                 return false;
 815
 816         return true;
 817 }
 818
 819 int blk_try_merge(struct request *rq, struct bio *bio)
 820 {
 821         if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
 822                 return ELEVATOR_BACK_MERGE;
 823         else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
 824                 return ELEVATOR_FRONT_MERGE;
 825         return ELEVATOR_NO_MERGE;
 826 }