1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Functions related to segment and merge handling 4 */ 5 #include <linux/kernel.h> 6 #include <linux/module.h> 7 #include <linux/bio.h> 8 #include <linux/blkdev.h> 9 #include <linux/scatterlist.h> 10 11 #include <trace/events/block.h> 12 13 #include "blk.h" 14 15 static struct bio *blk_bio_discard_split(struct request_queue *q, 16 struct bio *bio, 17 struct bio_set *bs, 18 unsigned *nsegs) 19 { 20 unsigned int max_discard_sectors, granularity; 21 int alignment; 22 sector_t tmp; 23 unsigned split_sectors; 24 25 *nsegs = 1; 26 27 /* Zero-sector (unknown) and one-sector granularities are the same. */ 28 granularity = max(q->limits.discard_granularity >> 9, 1U); 29 30 max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9); 31 max_discard_sectors -= max_discard_sectors % granularity; 32 33 if (unlikely(!max_discard_sectors)) { 34 /* XXX: warn */ 35 return NULL; 36 } 37 38 if (bio_sectors(bio) <= max_discard_sectors) 39 return NULL; 40 41 split_sectors = max_discard_sectors; 42 43 /* 44 * If the next starting sector would be misaligned, stop the discard at 45 * the previous aligned sector. 46 */ 47 alignment = (q->limits.discard_alignment >> 9) % granularity; 48 49 tmp = bio->bi_iter.bi_sector + split_sectors - alignment; 50 tmp = sector_div(tmp, granularity); 51 52 if (split_sectors > tmp) 53 split_sectors -= tmp; 54 55 return bio_split(bio, split_sectors, GFP_NOIO, bs); 56 } 57 58 static struct bio *blk_bio_write_zeroes_split(struct request_queue *q, 59 struct bio *bio, struct bio_set *bs, unsigned *nsegs) 60 { 61 *nsegs = 1; 62 63 if (!q->limits.max_write_zeroes_sectors) 64 return NULL; 65 66 if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors) 67 return NULL; 68 69 return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs); 70 } 71 72 static struct bio *blk_bio_write_same_split(struct request_queue *q, 73 struct bio *bio, 74 struct bio_set *bs, 75 unsigned *nsegs) 76 { 77 *nsegs = 1; 78 79 if (!q->limits.max_write_same_sectors) 80 return NULL; 81 82 if (bio_sectors(bio) <= q->limits.max_write_same_sectors) 83 return NULL; 84 85 return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs); 86 } 87 88 static inline unsigned get_max_io_size(struct request_queue *q, 89 struct bio *bio) 90 { 91 unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector); 92 unsigned mask = queue_logical_block_size(q) - 1; 93 94 /* aligned to logical block size */ 95 sectors &= ~(mask >> 9); 96 97 return sectors; 98 } 99 100 static struct bio *blk_bio_segment_split(struct request_queue *q, 101 struct bio *bio, 102 struct bio_set *bs, 103 unsigned *segs) 104 { 105 struct bio_vec bv, bvprv, *bvprvp = NULL; 106 struct bvec_iter iter; 107 unsigned seg_size = 0, nsegs = 0, sectors = 0; 108 unsigned front_seg_size = bio->bi_seg_front_size; 109 bool do_split = true; 110 struct bio *new = NULL; 111 const unsigned max_sectors = get_max_io_size(q, bio); 112 113 bio_for_each_segment(bv, bio, iter) { 114 /* 115 * If the queue doesn't support SG gaps and adding this 116 * offset would create a gap, disallow it. 117 */ 118 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset)) 119 goto split; 120 121 if (sectors + (bv.bv_len >> 9) > max_sectors) { 122 /* 123 * Consider this a new segment if we're splitting in 124 * the middle of this vector. 125 */ 126 if (nsegs < queue_max_segments(q) && 127 sectors < max_sectors) { 128 nsegs++; 129 sectors = max_sectors; 130 } 131 goto split; 132 } 133 134 if (bvprvp && blk_queue_cluster(q)) { 135 if (seg_size + bv.bv_len > queue_max_segment_size(q)) 136 goto new_segment; 137 if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv)) 138 goto new_segment; 139 if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv)) 140 goto new_segment; 141 142 seg_size += bv.bv_len; 143 bvprv = bv; 144 bvprvp = &bvprv; 145 sectors += bv.bv_len >> 9; 146 147 continue; 148 } 149 new_segment: 150 if (nsegs == queue_max_segments(q)) 151 goto split; 152 153 if (nsegs == 1 && seg_size > front_seg_size) 154 front_seg_size = seg_size; 155 156 nsegs++; 157 bvprv = bv; 158 bvprvp = &bvprv; 159 seg_size = bv.bv_len; 160 sectors += bv.bv_len >> 9; 161 162 } 163 164 do_split = false; 165 split: 166 *segs = nsegs; 167 168 if (do_split) { 169 new = bio_split(bio, sectors, GFP_NOIO, bs); 170 if (new) 171 bio = new; 172 } 173 174 if (nsegs == 1 && seg_size > front_seg_size) 175 front_seg_size = seg_size; 176 bio->bi_seg_front_size = front_seg_size; 177 if (seg_size > bio->bi_seg_back_size) 178 bio->bi_seg_back_size = seg_size; 179 180 return do_split ? new : NULL; 181 } 182 183 void blk_queue_split(struct request_queue *q, struct bio **bio) 184 { 185 struct bio *split, *res; 186 unsigned nsegs; 187 188 switch (bio_op(*bio)) { 189 case REQ_OP_DISCARD: 190 case REQ_OP_SECURE_ERASE: 191 split = blk_bio_discard_split(q, *bio, q->bio_split, &nsegs); 192 break; 193 case REQ_OP_WRITE_ZEROES: 194 split = blk_bio_write_zeroes_split(q, *bio, q->bio_split, &nsegs); 195 break; 196 case REQ_OP_WRITE_SAME: 197 split = blk_bio_write_same_split(q, *bio, q->bio_split, &nsegs); 198 break; 199 default: 200 split = blk_bio_segment_split(q, *bio, q->bio_split, &nsegs); 201 break; 202 } 203 204 /* physical segments can be figured out during splitting */ 205 res = split ? split : *bio; 206 res->bi_phys_segments = nsegs; 207 bio_set_flag(res, BIO_SEG_VALID); 208 209 if (split) { 210 /* there isn't chance to merge the splitted bio */ 211 split->bi_opf |= REQ_NOMERGE; 212 213 bio_chain(split, *bio); 214 trace_block_split(q, split, (*bio)->bi_iter.bi_sector); 215 generic_make_request(*bio); 216 *bio = split; 217 } 218 } 219 EXPORT_SYMBOL(blk_queue_split); 220 221 static unsigned int __blk_recalc_rq_segments(struct request_queue *q, 222 struct bio *bio, 223 bool no_sg_merge) 224 { 225 struct bio_vec bv, bvprv = { NULL }; 226 int cluster, prev = 0; 227 unsigned int seg_size, nr_phys_segs; 228 struct bio *fbio, *bbio; 229 struct bvec_iter iter; 230 231 if (!bio) 232 return 0; 233 234 switch (bio_op(bio)) { 235 case REQ_OP_DISCARD: 236 case REQ_OP_SECURE_ERASE: 237 case REQ_OP_WRITE_ZEROES: 238 return 0; 239 case REQ_OP_WRITE_SAME: 240 return 1; 241 } 242 243 fbio = bio; 244 cluster = blk_queue_cluster(q); 245 seg_size = 0; 246 nr_phys_segs = 0; 247 for_each_bio(bio) { 248 bio_for_each_segment(bv, bio, iter) { 249 /* 250 * If SG merging is disabled, each bio vector is 251 * a segment 252 */ 253 if (no_sg_merge) 254 goto new_segment; 255 256 if (prev && cluster) { 257 if (seg_size + bv.bv_len 258 > queue_max_segment_size(q)) 259 goto new_segment; 260 if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv)) 261 goto new_segment; 262 if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv)) 263 goto new_segment; 264 265 seg_size += bv.bv_len; 266 bvprv = bv; 267 continue; 268 } 269 new_segment: 270 if (nr_phys_segs == 1 && seg_size > 271 fbio->bi_seg_front_size) 272 fbio->bi_seg_front_size = seg_size; 273 274 nr_phys_segs++; 275 bvprv = bv; 276 prev = 1; 277 seg_size = bv.bv_len; 278 } 279 bbio = bio; 280 } 281 282 if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size) 283 fbio->bi_seg_front_size = seg_size; 284 if (seg_size > bbio->bi_seg_back_size) 285 bbio->bi_seg_back_size = seg_size; 286 287 return nr_phys_segs; 288 } 289 290 void blk_recalc_rq_segments(struct request *rq) 291 { 292 bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE, 293 &rq->q->queue_flags); 294 295 rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio, 296 no_sg_merge); 297 } 298 299 void blk_recount_segments(struct request_queue *q, struct bio *bio) 300 { 301 unsigned short seg_cnt; 302 303 /* estimate segment number by bi_vcnt for non-cloned bio */ 304 if (bio_flagged(bio, BIO_CLONED)) 305 seg_cnt = bio_segments(bio); 306 else 307 seg_cnt = bio->bi_vcnt; 308 309 if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) && 310 (seg_cnt < queue_max_segments(q))) 311 bio->bi_phys_segments = seg_cnt; 312 else { 313 struct bio *nxt = bio->bi_next; 314 315 bio->bi_next = NULL; 316 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false); 317 bio->bi_next = nxt; 318 } 319 320 bio_set_flag(bio, BIO_SEG_VALID); 321 } 322 EXPORT_SYMBOL(blk_recount_segments); 323 324 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, 325 struct bio *nxt) 326 { 327 struct bio_vec end_bv = { NULL }, nxt_bv; 328 329 if (!blk_queue_cluster(q)) 330 return 0; 331 332 if (bio->bi_seg_back_size + nxt->bi_seg_front_size > 333 queue_max_segment_size(q)) 334 return 0; 335 336 if (!bio_has_data(bio)) 337 return 1; 338 339 bio_get_last_bvec(bio, &end_bv); 340 bio_get_first_bvec(nxt, &nxt_bv); 341 342 if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv)) 343 return 0; 344 345 /* 346 * bio and nxt are contiguous in memory; check if the queue allows 347 * these two to be merged into one 348 */ 349 if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv)) 350 return 1; 351 352 return 0; 353 } 354 355 static inline void 356 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, 357 struct scatterlist *sglist, struct bio_vec *bvprv, 358 struct scatterlist **sg, int *nsegs, int *cluster) 359 { 360 361 int nbytes = bvec->bv_len; 362 363 if (*sg && *cluster) { 364 if ((*sg)->length + nbytes > queue_max_segment_size(q)) 365 goto new_segment; 366 367 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) 368 goto new_segment; 369 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) 370 goto new_segment; 371 372 (*sg)->length += nbytes; 373 } else { 374 new_segment: 375 if (!*sg) 376 *sg = sglist; 377 else { 378 /* 379 * If the driver previously mapped a shorter 380 * list, we could see a termination bit 381 * prematurely unless it fully inits the sg 382 * table on each mapping. We KNOW that there 383 * must be more entries here or the driver 384 * would be buggy, so force clear the 385 * termination bit to avoid doing a full 386 * sg_init_table() in drivers for each command. 387 */ 388 sg_unmark_end(*sg); 389 *sg = sg_next(*sg); 390 } 391 392 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); 393 (*nsegs)++; 394 } 395 *bvprv = *bvec; 396 } 397 398 static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv, 399 struct scatterlist *sglist, struct scatterlist **sg) 400 { 401 *sg = sglist; 402 sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); 403 return 1; 404 } 405 406 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 407 struct scatterlist *sglist, 408 struct scatterlist **sg) 409 { 410 struct bio_vec bvec, bvprv = { NULL }; 411 struct bvec_iter iter; 412 int cluster = blk_queue_cluster(q), nsegs = 0; 413 414 for_each_bio(bio) 415 bio_for_each_segment(bvec, bio, iter) 416 __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg, 417 &nsegs, &cluster); 418 419 return nsegs; 420 } 421 422 /* 423 * map a request to scatterlist, return number of sg entries setup. Caller 424 * must make sure sg can hold rq->nr_phys_segments entries 425 */ 426 int blk_rq_map_sg(struct request_queue *q, struct request *rq, 427 struct scatterlist *sglist) 428 { 429 struct scatterlist *sg = NULL; 430 int nsegs = 0; 431 432 if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) 433 nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg); 434 else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME) 435 nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg); 436 else if (rq->bio) 437 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg); 438 439 if (unlikely(rq->rq_flags & RQF_COPY_USER) && 440 (blk_rq_bytes(rq) & q->dma_pad_mask)) { 441 unsigned int pad_len = 442 (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1; 443 444 sg->length += pad_len; 445 rq->extra_len += pad_len; 446 } 447 448 if (q->dma_drain_size && q->dma_drain_needed(rq)) { 449 if (op_is_write(req_op(rq))) 450 memset(q->dma_drain_buffer, 0, q->dma_drain_size); 451 452 sg_unmark_end(sg); 453 sg = sg_next(sg); 454 sg_set_page(sg, virt_to_page(q->dma_drain_buffer), 455 q->dma_drain_size, 456 ((unsigned long)q->dma_drain_buffer) & 457 (PAGE_SIZE - 1)); 458 nsegs++; 459 rq->extra_len += q->dma_drain_size; 460 } 461 462 if (sg) 463 sg_mark_end(sg); 464 465 /* 466 * Something must have been wrong if the figured number of 467 * segment is bigger than number of req's physical segments 468 */ 469 WARN_ON(nsegs > blk_rq_nr_phys_segments(rq)); 470 471 return nsegs; 472 } 473 EXPORT_SYMBOL(blk_rq_map_sg); 474 475 static inline int ll_new_hw_segment(struct request_queue *q, 476 struct request *req, 477 struct bio *bio) 478 { 479 int nr_phys_segs = bio_phys_segments(q, bio); 480 481 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) 482 goto no_merge; 483 484 if (blk_integrity_merge_bio(q, req, bio) == false) 485 goto no_merge; 486 487 /* 488 * This will form the start of a new hw segment. Bump both 489 * counters. 490 */ 491 req->nr_phys_segments += nr_phys_segs; 492 return 1; 493 494 no_merge: 495 req_set_nomerge(q, req); 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_set_nomerge(q, req); 510 return 0; 511 } 512 if (!bio_flagged(req->biotail, BIO_SEG_VALID)) 513 blk_recount_segments(q, req->biotail); 514 if (!bio_flagged(bio, BIO_SEG_VALID)) 515 blk_recount_segments(q, bio); 516 517 return ll_new_hw_segment(q, req, bio); 518 } 519 520 int ll_front_merge_fn(struct request_queue *q, struct request *req, 521 struct bio *bio) 522 { 523 524 if (req_gap_front_merge(req, bio)) 525 return 0; 526 if (blk_integrity_rq(req) && 527 integrity_req_gap_front_merge(req, bio)) 528 return 0; 529 if (blk_rq_sectors(req) + bio_sectors(bio) > 530 blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { 531 req_set_nomerge(q, req); 532 return 0; 533 } 534 if (!bio_flagged(bio, BIO_SEG_VALID)) 535 blk_recount_segments(q, bio); 536 if (!bio_flagged(req->bio, BIO_SEG_VALID)) 537 blk_recount_segments(q, req->bio); 538 539 return ll_new_hw_segment(q, req, bio); 540 } 541 542 /* 543 * blk-mq uses req->special to carry normal driver per-request payload, it 544 * does not indicate a prepared command that we cannot merge with. 545 */ 546 static bool req_no_special_merge(struct request *req) 547 { 548 struct request_queue *q = req->q; 549 550 return !q->mq_ops && req->special; 551 } 552 553 static bool req_attempt_discard_merge(struct request_queue *q, struct request *req, 554 struct request *next) 555 { 556 unsigned short segments = blk_rq_nr_discard_segments(req); 557 558 if (segments >= queue_max_discard_segments(q)) 559 goto no_merge; 560 if (blk_rq_sectors(req) + bio_sectors(next->bio) > 561 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 562 goto no_merge; 563 564 req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next); 565 return true; 566 no_merge: 567 req_set_nomerge(q, req); 568 return false; 569 } 570 571 static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 572 struct request *next) 573 { 574 int total_phys_segments; 575 unsigned int seg_size = 576 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; 577 578 /* 579 * First check if the either of the requests are re-queued 580 * requests. Can't merge them if they are. 581 */ 582 if (req_no_special_merge(req) || req_no_special_merge(next)) 583 return 0; 584 585 if (req_gap_back_merge(req, next->bio)) 586 return 0; 587 588 /* 589 * Will it become too large? 590 */ 591 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 592 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 593 return 0; 594 595 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 596 if (blk_phys_contig_segment(q, req->biotail, next->bio)) { 597 if (req->nr_phys_segments == 1) 598 req->bio->bi_seg_front_size = seg_size; 599 if (next->nr_phys_segments == 1) 600 next->biotail->bi_seg_back_size = seg_size; 601 total_phys_segments--; 602 } 603 604 if (total_phys_segments > queue_max_segments(q)) 605 return 0; 606 607 if (blk_integrity_merge_rq(q, req, next) == false) 608 return 0; 609 610 /* Merge is OK... */ 611 req->nr_phys_segments = total_phys_segments; 612 return 1; 613 } 614 615 /** 616 * blk_rq_set_mixed_merge - mark a request as mixed merge 617 * @rq: request to mark as mixed merge 618 * 619 * Description: 620 * @rq is about to be mixed merged. Make sure the attributes 621 * which can be mixed are set in each bio and mark @rq as mixed 622 * merged. 623 */ 624 void blk_rq_set_mixed_merge(struct request *rq) 625 { 626 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; 627 struct bio *bio; 628 629 if (rq->rq_flags & RQF_MIXED_MERGE) 630 return; 631 632 /* 633 * @rq will no longer represent mixable attributes for all the 634 * contained bios. It will just track those of the first one. 635 * Distributes the attributs to each bio. 636 */ 637 for (bio = rq->bio; bio; bio = bio->bi_next) { 638 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 639 (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 640 bio->bi_opf |= ff; 641 } 642 rq->rq_flags |= RQF_MIXED_MERGE; 643 } 644 645 static void blk_account_io_merge(struct request *req) 646 { 647 if (blk_do_io_stat(req)) { 648 struct hd_struct *part; 649 int cpu; 650 651 cpu = part_stat_lock(); 652 part = req->part; 653 654 part_round_stats(req->q, cpu, part); 655 part_dec_in_flight(req->q, part, rq_data_dir(req)); 656 657 hd_struct_put(part); 658 part_stat_unlock(); 659 } 660 } 661 662 /* 663 * For non-mq, this has to be called with the request spinlock acquired. 664 * For mq with scheduling, the appropriate queue wide lock should be held. 665 */ 666 static struct request *attempt_merge(struct request_queue *q, 667 struct request *req, struct request *next) 668 { 669 if (!q->mq_ops) 670 lockdep_assert_held(q->queue_lock); 671 672 if (!rq_mergeable(req) || !rq_mergeable(next)) 673 return NULL; 674 675 if (req_op(req) != req_op(next)) 676 return NULL; 677 678 /* 679 * not contiguous 680 */ 681 if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)) 682 return NULL; 683 684 if (rq_data_dir(req) != rq_data_dir(next) 685 || req->rq_disk != next->rq_disk 686 || req_no_special_merge(next)) 687 return NULL; 688 689 if (req_op(req) == REQ_OP_WRITE_SAME && 690 !blk_write_same_mergeable(req->bio, next->bio)) 691 return NULL; 692 693 /* 694 * Don't allow merge of different write hints, or for a hint with 695 * non-hint IO. 696 */ 697 if (req->write_hint != next->write_hint) 698 return NULL; 699 700 /* 701 * If we are allowed to merge, then append bio list 702 * from next to rq and release next. merge_requests_fn 703 * will have updated segment counts, update sector 704 * counts here. Handle DISCARDs separately, as they 705 * have separate settings. 706 */ 707 if (req_op(req) == REQ_OP_DISCARD) { 708 if (!req_attempt_discard_merge(q, req, next)) 709 return NULL; 710 } else if (!ll_merge_requests_fn(q, req, next)) 711 return NULL; 712 713 /* 714 * If failfast settings disagree or any of the two is already 715 * a mixed merge, mark both as mixed before proceeding. This 716 * makes sure that all involved bios have mixable attributes 717 * set properly. 718 */ 719 if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || 720 (req->cmd_flags & REQ_FAILFAST_MASK) != 721 (next->cmd_flags & REQ_FAILFAST_MASK)) { 722 blk_rq_set_mixed_merge(req); 723 blk_rq_set_mixed_merge(next); 724 } 725 726 /* 727 * At this point we have either done a back merge 728 * or front merge. We need the smaller start_time of 729 * the merged requests to be the current request 730 * for accounting purposes. 731 */ 732 if (time_after(req->start_time, next->start_time)) 733 req->start_time = next->start_time; 734 735 req->biotail->bi_next = next->bio; 736 req->biotail = next->biotail; 737 738 req->__data_len += blk_rq_bytes(next); 739 740 if (req_op(req) != REQ_OP_DISCARD) 741 elv_merge_requests(q, req, next); 742 743 /* 744 * 'next' is going away, so update stats accordingly 745 */ 746 blk_account_io_merge(next); 747 748 req->ioprio = ioprio_best(req->ioprio, next->ioprio); 749 if (blk_rq_cpu_valid(next)) 750 req->cpu = next->cpu; 751 752 /* 753 * ownership of bio passed from next to req, return 'next' for 754 * the caller to free 755 */ 756 next->bio = NULL; 757 return next; 758 } 759 760 struct request *attempt_back_merge(struct request_queue *q, struct request *rq) 761 { 762 struct request *next = elv_latter_request(q, rq); 763 764 if (next) 765 return attempt_merge(q, rq, next); 766 767 return NULL; 768 } 769 770 struct request *attempt_front_merge(struct request_queue *q, struct request *rq) 771 { 772 struct request *prev = elv_former_request(q, rq); 773 774 if (prev) 775 return attempt_merge(q, prev, rq); 776 777 return NULL; 778 } 779 780 int blk_attempt_req_merge(struct request_queue *q, struct request *rq, 781 struct request *next) 782 { 783 struct elevator_queue *e = q->elevator; 784 struct request *free; 785 786 if (!e->uses_mq && e->type->ops.sq.elevator_allow_rq_merge_fn) 787 if (!e->type->ops.sq.elevator_allow_rq_merge_fn(q, rq, next)) 788 return 0; 789 790 free = attempt_merge(q, rq, next); 791 if (free) { 792 __blk_put_request(q, free); 793 return 1; 794 } 795 796 return 0; 797 } 798 799 bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 800 { 801 if (!rq_mergeable(rq) || !bio_mergeable(bio)) 802 return false; 803 804 if (req_op(rq) != bio_op(bio)) 805 return false; 806 807 /* different data direction or already started, don't merge */ 808 if (bio_data_dir(bio) != rq_data_dir(rq)) 809 return false; 810 811 /* must be same device and not a special request */ 812 if (rq->rq_disk != bio->bi_disk || req_no_special_merge(rq)) 813 return false; 814 815 /* only merge integrity protected bio into ditto rq */ 816 if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 817 return false; 818 819 /* must be using the same buffer */ 820 if (req_op(rq) == REQ_OP_WRITE_SAME && 821 !blk_write_same_mergeable(rq->bio, bio)) 822 return false; 823 824 /* 825 * Don't allow merge of different write hints, or for a hint with 826 * non-hint IO. 827 */ 828 if (rq->write_hint != bio->bi_write_hint) 829 return false; 830 831 return true; 832 } 833 834 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) 835 { 836 if (req_op(rq) == REQ_OP_DISCARD && 837 queue_max_discard_segments(rq->q) > 1) 838 return ELEVATOR_DISCARD_MERGE; 839 else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 840 return ELEVATOR_BACK_MERGE; 841 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 842 return ELEVATOR_FRONT_MERGE; 843 return ELEVATOR_NO_MERGE; 844 } 845