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 switch (bio_op(*bio)) { 176 case REQ_OP_DISCARD: 177 case REQ_OP_SECURE_ERASE: 178 split = blk_bio_discard_split(q, *bio, bs, &nsegs); 179 break; 180 case REQ_OP_WRITE_SAME: 181 split = blk_bio_write_same_split(q, *bio, bs, &nsegs); 182 break; 183 default: 184 split = blk_bio_segment_split(q, *bio, q->bio_split, &nsegs); 185 break; 186 } 187 188 /* physical segments can be figured out during splitting */ 189 res = split ? split : *bio; 190 res->bi_phys_segments = nsegs; 191 bio_set_flag(res, BIO_SEG_VALID); 192 193 if (split) { 194 /* there isn't chance to merge the splitted bio */ 195 split->bi_opf |= REQ_NOMERGE; 196 197 bio_chain(split, *bio); 198 trace_block_split(q, split, (*bio)->bi_iter.bi_sector); 199 generic_make_request(*bio); 200 *bio = split; 201 } 202 } 203 EXPORT_SYMBOL(blk_queue_split); 204 205 static unsigned int __blk_recalc_rq_segments(struct request_queue *q, 206 struct bio *bio, 207 bool no_sg_merge) 208 { 209 struct bio_vec bv, bvprv = { NULL }; 210 int cluster, prev = 0; 211 unsigned int seg_size, nr_phys_segs; 212 struct bio *fbio, *bbio; 213 struct bvec_iter iter; 214 215 if (!bio) 216 return 0; 217 218 /* 219 * This should probably be returning 0, but blk_add_request_payload() 220 * (Christoph!!!!) 221 */ 222 if (bio_op(bio) == REQ_OP_DISCARD || bio_op(bio) == REQ_OP_SECURE_ERASE) 223 return 1; 224 225 if (bio_op(bio) == REQ_OP_WRITE_SAME) 226 return 1; 227 228 fbio = bio; 229 cluster = blk_queue_cluster(q); 230 seg_size = 0; 231 nr_phys_segs = 0; 232 for_each_bio(bio) { 233 bio_for_each_segment(bv, bio, iter) { 234 /* 235 * If SG merging is disabled, each bio vector is 236 * a segment 237 */ 238 if (no_sg_merge) 239 goto new_segment; 240 241 if (prev && cluster) { 242 if (seg_size + bv.bv_len 243 > queue_max_segment_size(q)) 244 goto new_segment; 245 if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv)) 246 goto new_segment; 247 if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv)) 248 goto new_segment; 249 250 seg_size += bv.bv_len; 251 bvprv = bv; 252 continue; 253 } 254 new_segment: 255 if (nr_phys_segs == 1 && seg_size > 256 fbio->bi_seg_front_size) 257 fbio->bi_seg_front_size = seg_size; 258 259 nr_phys_segs++; 260 bvprv = bv; 261 prev = 1; 262 seg_size = bv.bv_len; 263 } 264 bbio = bio; 265 } 266 267 if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size) 268 fbio->bi_seg_front_size = seg_size; 269 if (seg_size > bbio->bi_seg_back_size) 270 bbio->bi_seg_back_size = seg_size; 271 272 return nr_phys_segs; 273 } 274 275 void blk_recalc_rq_segments(struct request *rq) 276 { 277 bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE, 278 &rq->q->queue_flags); 279 280 rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio, 281 no_sg_merge); 282 } 283 284 void blk_recount_segments(struct request_queue *q, struct bio *bio) 285 { 286 unsigned short seg_cnt; 287 288 /* estimate segment number by bi_vcnt for non-cloned bio */ 289 if (bio_flagged(bio, BIO_CLONED)) 290 seg_cnt = bio_segments(bio); 291 else 292 seg_cnt = bio->bi_vcnt; 293 294 if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) && 295 (seg_cnt < queue_max_segments(q))) 296 bio->bi_phys_segments = seg_cnt; 297 else { 298 struct bio *nxt = bio->bi_next; 299 300 bio->bi_next = NULL; 301 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false); 302 bio->bi_next = nxt; 303 } 304 305 bio_set_flag(bio, BIO_SEG_VALID); 306 } 307 EXPORT_SYMBOL(blk_recount_segments); 308 309 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, 310 struct bio *nxt) 311 { 312 struct bio_vec end_bv = { NULL }, nxt_bv; 313 314 if (!blk_queue_cluster(q)) 315 return 0; 316 317 if (bio->bi_seg_back_size + nxt->bi_seg_front_size > 318 queue_max_segment_size(q)) 319 return 0; 320 321 if (!bio_has_data(bio)) 322 return 1; 323 324 bio_get_last_bvec(bio, &end_bv); 325 bio_get_first_bvec(nxt, &nxt_bv); 326 327 if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv)) 328 return 0; 329 330 /* 331 * bio and nxt are contiguous in memory; check if the queue allows 332 * these two to be merged into one 333 */ 334 if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv)) 335 return 1; 336 337 return 0; 338 } 339 340 static inline void 341 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, 342 struct scatterlist *sglist, struct bio_vec *bvprv, 343 struct scatterlist **sg, int *nsegs, int *cluster) 344 { 345 346 int nbytes = bvec->bv_len; 347 348 if (*sg && *cluster) { 349 if ((*sg)->length + nbytes > queue_max_segment_size(q)) 350 goto new_segment; 351 352 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) 353 goto new_segment; 354 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) 355 goto new_segment; 356 357 (*sg)->length += nbytes; 358 } else { 359 new_segment: 360 if (!*sg) 361 *sg = sglist; 362 else { 363 /* 364 * If the driver previously mapped a shorter 365 * list, we could see a termination bit 366 * prematurely unless it fully inits the sg 367 * table on each mapping. We KNOW that there 368 * must be more entries here or the driver 369 * would be buggy, so force clear the 370 * termination bit to avoid doing a full 371 * sg_init_table() in drivers for each command. 372 */ 373 sg_unmark_end(*sg); 374 *sg = sg_next(*sg); 375 } 376 377 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); 378 (*nsegs)++; 379 } 380 *bvprv = *bvec; 381 } 382 383 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 384 struct scatterlist *sglist, 385 struct scatterlist **sg) 386 { 387 struct bio_vec bvec, bvprv = { NULL }; 388 struct bvec_iter iter; 389 int nsegs, cluster; 390 391 nsegs = 0; 392 cluster = blk_queue_cluster(q); 393 394 switch (bio_op(bio)) { 395 case REQ_OP_DISCARD: 396 case REQ_OP_SECURE_ERASE: 397 /* 398 * This is a hack - drivers should be neither modifying the 399 * biovec, nor relying on bi_vcnt - but because of 400 * blk_add_request_payload(), a discard bio may or may not have 401 * a payload we need to set up here (thank you Christoph) and 402 * bi_vcnt is really the only way of telling if we need to. 403 */ 404 if (!bio->bi_vcnt) 405 return 0; 406 /* Fall through */ 407 case REQ_OP_WRITE_SAME: 408 *sg = sglist; 409 bvec = bio_iovec(bio); 410 sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset); 411 return 1; 412 default: 413 break; 414 } 415 416 for_each_bio(bio) 417 bio_for_each_segment(bvec, bio, iter) 418 __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg, 419 &nsegs, &cluster); 420 421 return nsegs; 422 } 423 424 /* 425 * map a request to scatterlist, return number of sg entries setup. Caller 426 * must make sure sg can hold rq->nr_phys_segments entries 427 */ 428 int blk_rq_map_sg(struct request_queue *q, struct request *rq, 429 struct scatterlist *sglist) 430 { 431 struct scatterlist *sg = NULL; 432 int nsegs = 0; 433 434 if (rq->bio) 435 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg); 436 437 if (unlikely(rq->cmd_flags & REQ_COPY_USER) && 438 (blk_rq_bytes(rq) & q->dma_pad_mask)) { 439 unsigned int pad_len = 440 (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1; 441 442 sg->length += pad_len; 443 rq->extra_len += pad_len; 444 } 445 446 if (q->dma_drain_size && q->dma_drain_needed(rq)) { 447 if (op_is_write(req_op(rq))) 448 memset(q->dma_drain_buffer, 0, q->dma_drain_size); 449 450 sg_unmark_end(sg); 451 sg = sg_next(sg); 452 sg_set_page(sg, virt_to_page(q->dma_drain_buffer), 453 q->dma_drain_size, 454 ((unsigned long)q->dma_drain_buffer) & 455 (PAGE_SIZE - 1)); 456 nsegs++; 457 rq->extra_len += q->dma_drain_size; 458 } 459 460 if (sg) 461 sg_mark_end(sg); 462 463 /* 464 * Something must have been wrong if the figured number of 465 * segment is bigger than number of req's physical segments 466 */ 467 WARN_ON(nsegs > rq->nr_phys_segments); 468 469 return nsegs; 470 } 471 EXPORT_SYMBOL(blk_rq_map_sg); 472 473 static inline int ll_new_hw_segment(struct request_queue *q, 474 struct request *req, 475 struct bio *bio) 476 { 477 int nr_phys_segs = bio_phys_segments(q, bio); 478 479 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) 480 goto no_merge; 481 482 if (blk_integrity_merge_bio(q, req, bio) == false) 483 goto no_merge; 484 485 /* 486 * This will form the start of a new hw segment. Bump both 487 * counters. 488 */ 489 req->nr_phys_segments += nr_phys_segs; 490 return 1; 491 492 no_merge: 493 req->cmd_flags |= REQ_NOMERGE; 494 if (req == q->last_merge) 495 q->last_merge = NULL; 496 return 0; 497 } 498 499 int ll_back_merge_fn(struct request_queue *q, struct request *req, 500 struct bio *bio) 501 { 502 if (req_gap_back_merge(req, bio)) 503 return 0; 504 if (blk_integrity_rq(req) && 505 integrity_req_gap_back_merge(req, bio)) 506 return 0; 507 if (blk_rq_sectors(req) + bio_sectors(bio) > 508 blk_rq_get_max_sectors(req, blk_rq_pos(req))) { 509 req->cmd_flags |= REQ_NOMERGE; 510 if (req == q->last_merge) 511 q->last_merge = NULL; 512 return 0; 513 } 514 if (!bio_flagged(req->biotail, BIO_SEG_VALID)) 515 blk_recount_segments(q, req->biotail); 516 if (!bio_flagged(bio, BIO_SEG_VALID)) 517 blk_recount_segments(q, bio); 518 519 return ll_new_hw_segment(q, req, bio); 520 } 521 522 int ll_front_merge_fn(struct request_queue *q, struct request *req, 523 struct bio *bio) 524 { 525 526 if (req_gap_front_merge(req, bio)) 527 return 0; 528 if (blk_integrity_rq(req) && 529 integrity_req_gap_front_merge(req, bio)) 530 return 0; 531 if (blk_rq_sectors(req) + bio_sectors(bio) > 532 blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { 533 req->cmd_flags |= REQ_NOMERGE; 534 if (req == q->last_merge) 535 q->last_merge = NULL; 536 return 0; 537 } 538 if (!bio_flagged(bio, BIO_SEG_VALID)) 539 blk_recount_segments(q, bio); 540 if (!bio_flagged(req->bio, BIO_SEG_VALID)) 541 blk_recount_segments(q, req->bio); 542 543 return ll_new_hw_segment(q, req, bio); 544 } 545 546 /* 547 * blk-mq uses req->special to carry normal driver per-request payload, it 548 * does not indicate a prepared command that we cannot merge with. 549 */ 550 static bool req_no_special_merge(struct request *req) 551 { 552 struct request_queue *q = req->q; 553 554 return !q->mq_ops && req->special; 555 } 556 557 static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 558 struct request *next) 559 { 560 int total_phys_segments; 561 unsigned int seg_size = 562 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; 563 564 /* 565 * First check if the either of the requests are re-queued 566 * requests. Can't merge them if they are. 567 */ 568 if (req_no_special_merge(req) || req_no_special_merge(next)) 569 return 0; 570 571 if (req_gap_back_merge(req, next->bio)) 572 return 0; 573 574 /* 575 * Will it become too large? 576 */ 577 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 578 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 579 return 0; 580 581 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 582 if (blk_phys_contig_segment(q, req->biotail, next->bio)) { 583 if (req->nr_phys_segments == 1) 584 req->bio->bi_seg_front_size = seg_size; 585 if (next->nr_phys_segments == 1) 586 next->biotail->bi_seg_back_size = seg_size; 587 total_phys_segments--; 588 } 589 590 if (total_phys_segments > queue_max_segments(q)) 591 return 0; 592 593 if (blk_integrity_merge_rq(q, req, next) == false) 594 return 0; 595 596 /* Merge is OK... */ 597 req->nr_phys_segments = total_phys_segments; 598 return 1; 599 } 600 601 /** 602 * blk_rq_set_mixed_merge - mark a request as mixed merge 603 * @rq: request to mark as mixed merge 604 * 605 * Description: 606 * @rq is about to be mixed merged. Make sure the attributes 607 * which can be mixed are set in each bio and mark @rq as mixed 608 * merged. 609 */ 610 void blk_rq_set_mixed_merge(struct request *rq) 611 { 612 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; 613 struct bio *bio; 614 615 if (rq->cmd_flags & REQ_MIXED_MERGE) 616 return; 617 618 /* 619 * @rq will no longer represent mixable attributes for all the 620 * contained bios. It will just track those of the first one. 621 * Distributes the attributs to each bio. 622 */ 623 for (bio = rq->bio; bio; bio = bio->bi_next) { 624 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 625 (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 626 bio->bi_opf |= ff; 627 } 628 rq->cmd_flags |= REQ_MIXED_MERGE; 629 } 630 631 static void blk_account_io_merge(struct request *req) 632 { 633 if (blk_do_io_stat(req)) { 634 struct hd_struct *part; 635 int cpu; 636 637 cpu = part_stat_lock(); 638 part = req->part; 639 640 part_round_stats(cpu, part); 641 part_dec_in_flight(part, rq_data_dir(req)); 642 643 hd_struct_put(part); 644 part_stat_unlock(); 645 } 646 } 647 648 /* 649 * Has to be called with the request spinlock acquired 650 */ 651 static int attempt_merge(struct request_queue *q, struct request *req, 652 struct request *next) 653 { 654 if (!rq_mergeable(req) || !rq_mergeable(next)) 655 return 0; 656 657 if (req_op(req) != req_op(next)) 658 return 0; 659 660 /* 661 * not contiguous 662 */ 663 if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)) 664 return 0; 665 666 if (rq_data_dir(req) != rq_data_dir(next) 667 || req->rq_disk != next->rq_disk 668 || req_no_special_merge(next)) 669 return 0; 670 671 if (req_op(req) == REQ_OP_WRITE_SAME && 672 !blk_write_same_mergeable(req->bio, next->bio)) 673 return 0; 674 675 /* 676 * If we are allowed to merge, then append bio list 677 * from next to rq and release next. merge_requests_fn 678 * will have updated segment counts, update sector 679 * counts here. 680 */ 681 if (!ll_merge_requests_fn(q, req, next)) 682 return 0; 683 684 /* 685 * If failfast settings disagree or any of the two is already 686 * a mixed merge, mark both as mixed before proceeding. This 687 * makes sure that all involved bios have mixable attributes 688 * set properly. 689 */ 690 if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE || 691 (req->cmd_flags & REQ_FAILFAST_MASK) != 692 (next->cmd_flags & REQ_FAILFAST_MASK)) { 693 blk_rq_set_mixed_merge(req); 694 blk_rq_set_mixed_merge(next); 695 } 696 697 /* 698 * At this point we have either done a back merge 699 * or front merge. We need the smaller start_time of 700 * the merged requests to be the current request 701 * for accounting purposes. 702 */ 703 if (time_after(req->start_time, next->start_time)) 704 req->start_time = next->start_time; 705 706 req->biotail->bi_next = next->bio; 707 req->biotail = next->biotail; 708 709 req->__data_len += blk_rq_bytes(next); 710 711 elv_merge_requests(q, req, next); 712 713 /* 714 * 'next' is going away, so update stats accordingly 715 */ 716 blk_account_io_merge(next); 717 718 req->ioprio = ioprio_best(req->ioprio, next->ioprio); 719 if (blk_rq_cpu_valid(next)) 720 req->cpu = next->cpu; 721 722 /* owner-ship of bio passed from next to req */ 723 next->bio = NULL; 724 __blk_put_request(q, next); 725 return 1; 726 } 727 728 int attempt_back_merge(struct request_queue *q, struct request *rq) 729 { 730 struct request *next = elv_latter_request(q, rq); 731 732 if (next) 733 return attempt_merge(q, rq, next); 734 735 return 0; 736 } 737 738 int attempt_front_merge(struct request_queue *q, struct request *rq) 739 { 740 struct request *prev = elv_former_request(q, rq); 741 742 if (prev) 743 return attempt_merge(q, prev, rq); 744 745 return 0; 746 } 747 748 int blk_attempt_req_merge(struct request_queue *q, struct request *rq, 749 struct request *next) 750 { 751 struct elevator_queue *e = q->elevator; 752 753 if (e->type->ops.elevator_allow_rq_merge_fn) 754 if (!e->type->ops.elevator_allow_rq_merge_fn(q, rq, next)) 755 return 0; 756 757 return attempt_merge(q, rq, next); 758 } 759 760 bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 761 { 762 if (!rq_mergeable(rq) || !bio_mergeable(bio)) 763 return false; 764 765 if (req_op(rq) != bio_op(bio)) 766 return false; 767 768 /* different data direction or already started, don't merge */ 769 if (bio_data_dir(bio) != rq_data_dir(rq)) 770 return false; 771 772 /* must be same device and not a special request */ 773 if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq)) 774 return false; 775 776 /* only merge integrity protected bio into ditto rq */ 777 if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 778 return false; 779 780 /* must be using the same buffer */ 781 if (req_op(rq) == REQ_OP_WRITE_SAME && 782 !blk_write_same_mergeable(rq->bio, bio)) 783 return false; 784 785 return true; 786 } 787 788 int blk_try_merge(struct request *rq, struct bio *bio) 789 { 790 if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 791 return ELEVATOR_BACK_MERGE; 792 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 793 return ELEVATOR_FRONT_MERGE; 794 return ELEVATOR_NO_MERGE; 795 } 796