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