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