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 /* 214 * Since we're recursing into make_request here, ensure 215 * that we mark this bio as already having entered the queue. 216 * If not, and the queue is going away, we can get stuck 217 * forever on waiting for the queue reference to drop. But 218 * that will never happen, as we're already holding a 219 * reference to it. 220 */ 221 bio_set_flag(*bio, BIO_QUEUE_ENTERED); 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 switch (bio_op(bio)) { 245 case REQ_OP_DISCARD: 246 case REQ_OP_SECURE_ERASE: 247 case REQ_OP_WRITE_ZEROES: 248 return 0; 249 case REQ_OP_WRITE_SAME: 250 return 1; 251 } 252 253 fbio = bio; 254 cluster = blk_queue_cluster(q); 255 seg_size = 0; 256 nr_phys_segs = 0; 257 for_each_bio(bio) { 258 bio_for_each_segment(bv, bio, iter) { 259 /* 260 * If SG merging is disabled, each bio vector is 261 * a segment 262 */ 263 if (no_sg_merge) 264 goto new_segment; 265 266 if (prev && cluster) { 267 if (seg_size + bv.bv_len 268 > queue_max_segment_size(q)) 269 goto new_segment; 270 if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv)) 271 goto new_segment; 272 if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv)) 273 goto new_segment; 274 275 seg_size += bv.bv_len; 276 bvprv = bv; 277 continue; 278 } 279 new_segment: 280 if (nr_phys_segs == 1 && seg_size > 281 fbio->bi_seg_front_size) 282 fbio->bi_seg_front_size = seg_size; 283 284 nr_phys_segs++; 285 bvprv = bv; 286 prev = 1; 287 seg_size = bv.bv_len; 288 } 289 bbio = bio; 290 } 291 292 if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size) 293 fbio->bi_seg_front_size = seg_size; 294 if (seg_size > bbio->bi_seg_back_size) 295 bbio->bi_seg_back_size = seg_size; 296 297 return nr_phys_segs; 298 } 299 300 void blk_recalc_rq_segments(struct request *rq) 301 { 302 bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE, 303 &rq->q->queue_flags); 304 305 rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio, 306 no_sg_merge); 307 } 308 309 void blk_recount_segments(struct request_queue *q, struct bio *bio) 310 { 311 unsigned short seg_cnt; 312 313 /* estimate segment number by bi_vcnt for non-cloned bio */ 314 if (bio_flagged(bio, BIO_CLONED)) 315 seg_cnt = bio_segments(bio); 316 else 317 seg_cnt = bio->bi_vcnt; 318 319 if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) && 320 (seg_cnt < queue_max_segments(q))) 321 bio->bi_phys_segments = seg_cnt; 322 else { 323 struct bio *nxt = bio->bi_next; 324 325 bio->bi_next = NULL; 326 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false); 327 bio->bi_next = nxt; 328 } 329 330 bio_set_flag(bio, BIO_SEG_VALID); 331 } 332 EXPORT_SYMBOL(blk_recount_segments); 333 334 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, 335 struct bio *nxt) 336 { 337 struct bio_vec end_bv = { NULL }, nxt_bv; 338 339 if (!blk_queue_cluster(q)) 340 return 0; 341 342 if (bio->bi_seg_back_size + nxt->bi_seg_front_size > 343 queue_max_segment_size(q)) 344 return 0; 345 346 if (!bio_has_data(bio)) 347 return 1; 348 349 bio_get_last_bvec(bio, &end_bv); 350 bio_get_first_bvec(nxt, &nxt_bv); 351 352 if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv)) 353 return 0; 354 355 /* 356 * bio and nxt are contiguous in memory; check if the queue allows 357 * these two to be merged into one 358 */ 359 if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv)) 360 return 1; 361 362 return 0; 363 } 364 365 static inline void 366 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, 367 struct scatterlist *sglist, struct bio_vec *bvprv, 368 struct scatterlist **sg, int *nsegs, int *cluster) 369 { 370 371 int nbytes = bvec->bv_len; 372 373 if (*sg && *cluster) { 374 if ((*sg)->length + nbytes > queue_max_segment_size(q)) 375 goto new_segment; 376 377 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) 378 goto new_segment; 379 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) 380 goto new_segment; 381 382 (*sg)->length += nbytes; 383 } else { 384 new_segment: 385 if (!*sg) 386 *sg = sglist; 387 else { 388 /* 389 * If the driver previously mapped a shorter 390 * list, we could see a termination bit 391 * prematurely unless it fully inits the sg 392 * table on each mapping. We KNOW that there 393 * must be more entries here or the driver 394 * would be buggy, so force clear the 395 * termination bit to avoid doing a full 396 * sg_init_table() in drivers for each command. 397 */ 398 sg_unmark_end(*sg); 399 *sg = sg_next(*sg); 400 } 401 402 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); 403 (*nsegs)++; 404 } 405 *bvprv = *bvec; 406 } 407 408 static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv, 409 struct scatterlist *sglist, struct scatterlist **sg) 410 { 411 *sg = sglist; 412 sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); 413 return 1; 414 } 415 416 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 417 struct scatterlist *sglist, 418 struct scatterlist **sg) 419 { 420 struct bio_vec bvec, bvprv = { NULL }; 421 struct bvec_iter iter; 422 int cluster = blk_queue_cluster(q), nsegs = 0; 423 424 for_each_bio(bio) 425 bio_for_each_segment(bvec, bio, iter) 426 __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg, 427 &nsegs, &cluster); 428 429 return nsegs; 430 } 431 432 /* 433 * map a request to scatterlist, return number of sg entries setup. Caller 434 * must make sure sg can hold rq->nr_phys_segments entries 435 */ 436 int blk_rq_map_sg(struct request_queue *q, struct request *rq, 437 struct scatterlist *sglist) 438 { 439 struct scatterlist *sg = NULL; 440 int nsegs = 0; 441 442 if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) 443 nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg); 444 else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME) 445 nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg); 446 else if (rq->bio) 447 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg); 448 449 if (unlikely(rq->rq_flags & RQF_COPY_USER) && 450 (blk_rq_bytes(rq) & q->dma_pad_mask)) { 451 unsigned int pad_len = 452 (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1; 453 454 sg->length += pad_len; 455 rq->extra_len += pad_len; 456 } 457 458 if (q->dma_drain_size && q->dma_drain_needed(rq)) { 459 if (op_is_write(req_op(rq))) 460 memset(q->dma_drain_buffer, 0, q->dma_drain_size); 461 462 sg_unmark_end(sg); 463 sg = sg_next(sg); 464 sg_set_page(sg, virt_to_page(q->dma_drain_buffer), 465 q->dma_drain_size, 466 ((unsigned long)q->dma_drain_buffer) & 467 (PAGE_SIZE - 1)); 468 nsegs++; 469 rq->extra_len += q->dma_drain_size; 470 } 471 472 if (sg) 473 sg_mark_end(sg); 474 475 /* 476 * Something must have been wrong if the figured number of 477 * segment is bigger than number of req's physical segments 478 */ 479 WARN_ON(nsegs > blk_rq_nr_phys_segments(rq)); 480 481 return nsegs; 482 } 483 EXPORT_SYMBOL(blk_rq_map_sg); 484 485 static inline int ll_new_hw_segment(struct request_queue *q, 486 struct request *req, 487 struct bio *bio) 488 { 489 int nr_phys_segs = bio_phys_segments(q, bio); 490 491 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) 492 goto no_merge; 493 494 if (blk_integrity_merge_bio(q, req, bio) == false) 495 goto no_merge; 496 497 /* 498 * This will form the start of a new hw segment. Bump both 499 * counters. 500 */ 501 req->nr_phys_segments += nr_phys_segs; 502 return 1; 503 504 no_merge: 505 req_set_nomerge(q, req); 506 return 0; 507 } 508 509 int ll_back_merge_fn(struct request_queue *q, struct request *req, 510 struct bio *bio) 511 { 512 if (req_gap_back_merge(req, bio)) 513 return 0; 514 if (blk_integrity_rq(req) && 515 integrity_req_gap_back_merge(req, bio)) 516 return 0; 517 if (blk_rq_sectors(req) + bio_sectors(bio) > 518 blk_rq_get_max_sectors(req, blk_rq_pos(req))) { 519 req_set_nomerge(q, req); 520 return 0; 521 } 522 if (!bio_flagged(req->biotail, BIO_SEG_VALID)) 523 blk_recount_segments(q, req->biotail); 524 if (!bio_flagged(bio, BIO_SEG_VALID)) 525 blk_recount_segments(q, bio); 526 527 return ll_new_hw_segment(q, req, bio); 528 } 529 530 int ll_front_merge_fn(struct request_queue *q, struct request *req, 531 struct bio *bio) 532 { 533 534 if (req_gap_front_merge(req, bio)) 535 return 0; 536 if (blk_integrity_rq(req) && 537 integrity_req_gap_front_merge(req, bio)) 538 return 0; 539 if (blk_rq_sectors(req) + bio_sectors(bio) > 540 blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { 541 req_set_nomerge(q, req); 542 return 0; 543 } 544 if (!bio_flagged(bio, BIO_SEG_VALID)) 545 blk_recount_segments(q, bio); 546 if (!bio_flagged(req->bio, BIO_SEG_VALID)) 547 blk_recount_segments(q, req->bio); 548 549 return ll_new_hw_segment(q, req, bio); 550 } 551 552 /* 553 * blk-mq uses req->special to carry normal driver per-request payload, it 554 * does not indicate a prepared command that we cannot merge with. 555 */ 556 static bool req_no_special_merge(struct request *req) 557 { 558 struct request_queue *q = req->q; 559 560 return !q->mq_ops && req->special; 561 } 562 563 static bool req_attempt_discard_merge(struct request_queue *q, struct request *req, 564 struct request *next) 565 { 566 unsigned short segments = blk_rq_nr_discard_segments(req); 567 568 if (segments >= queue_max_discard_segments(q)) 569 goto no_merge; 570 if (blk_rq_sectors(req) + bio_sectors(next->bio) > 571 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 572 goto no_merge; 573 574 req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next); 575 return true; 576 no_merge: 577 req_set_nomerge(q, req); 578 return false; 579 } 580 581 static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 582 struct request *next) 583 { 584 int total_phys_segments; 585 unsigned int seg_size = 586 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; 587 588 /* 589 * First check if the either of the requests are re-queued 590 * requests. Can't merge them if they are. 591 */ 592 if (req_no_special_merge(req) || req_no_special_merge(next)) 593 return 0; 594 595 if (req_gap_back_merge(req, next->bio)) 596 return 0; 597 598 /* 599 * Will it become too large? 600 */ 601 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 602 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 603 return 0; 604 605 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 606 if (blk_phys_contig_segment(q, req->biotail, next->bio)) { 607 if (req->nr_phys_segments == 1) 608 req->bio->bi_seg_front_size = seg_size; 609 if (next->nr_phys_segments == 1) 610 next->biotail->bi_seg_back_size = seg_size; 611 total_phys_segments--; 612 } 613 614 if (total_phys_segments > queue_max_segments(q)) 615 return 0; 616 617 if (blk_integrity_merge_rq(q, req, next) == false) 618 return 0; 619 620 /* Merge is OK... */ 621 req->nr_phys_segments = total_phys_segments; 622 return 1; 623 } 624 625 /** 626 * blk_rq_set_mixed_merge - mark a request as mixed merge 627 * @rq: request to mark as mixed merge 628 * 629 * Description: 630 * @rq is about to be mixed merged. Make sure the attributes 631 * which can be mixed are set in each bio and mark @rq as mixed 632 * merged. 633 */ 634 void blk_rq_set_mixed_merge(struct request *rq) 635 { 636 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; 637 struct bio *bio; 638 639 if (rq->rq_flags & RQF_MIXED_MERGE) 640 return; 641 642 /* 643 * @rq will no longer represent mixable attributes for all the 644 * contained bios. It will just track those of the first one. 645 * Distributes the attributs to each bio. 646 */ 647 for (bio = rq->bio; bio; bio = bio->bi_next) { 648 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 649 (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 650 bio->bi_opf |= ff; 651 } 652 rq->rq_flags |= RQF_MIXED_MERGE; 653 } 654 655 static void blk_account_io_merge(struct request *req) 656 { 657 if (blk_do_io_stat(req)) { 658 struct hd_struct *part; 659 int cpu; 660 661 cpu = part_stat_lock(); 662 part = req->part; 663 664 part_round_stats(req->q, cpu, part); 665 part_dec_in_flight(req->q, part, rq_data_dir(req)); 666 667 hd_struct_put(part); 668 part_stat_unlock(); 669 } 670 } 671 672 /* 673 * For non-mq, this has to be called with the request spinlock acquired. 674 * For mq with scheduling, the appropriate queue wide lock should be held. 675 */ 676 static struct request *attempt_merge(struct request_queue *q, 677 struct request *req, struct request *next) 678 { 679 if (!q->mq_ops) 680 lockdep_assert_held(q->queue_lock); 681 682 if (!rq_mergeable(req) || !rq_mergeable(next)) 683 return NULL; 684 685 if (req_op(req) != req_op(next)) 686 return NULL; 687 688 /* 689 * not contiguous 690 */ 691 if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)) 692 return NULL; 693 694 if (rq_data_dir(req) != rq_data_dir(next) 695 || req->rq_disk != next->rq_disk 696 || req_no_special_merge(next)) 697 return NULL; 698 699 if (req_op(req) == REQ_OP_WRITE_SAME && 700 !blk_write_same_mergeable(req->bio, next->bio)) 701 return NULL; 702 703 /* 704 * Don't allow merge of different write hints, or for a hint with 705 * non-hint IO. 706 */ 707 if (req->write_hint != next->write_hint) 708 return NULL; 709 710 /* 711 * If we are allowed to merge, then append bio list 712 * from next to rq and release next. merge_requests_fn 713 * will have updated segment counts, update sector 714 * counts here. Handle DISCARDs separately, as they 715 * have separate settings. 716 */ 717 if (req_op(req) == REQ_OP_DISCARD) { 718 if (!req_attempt_discard_merge(q, req, next)) 719 return NULL; 720 } else if (!ll_merge_requests_fn(q, req, next)) 721 return NULL; 722 723 /* 724 * If failfast settings disagree or any of the two is already 725 * a mixed merge, mark both as mixed before proceeding. This 726 * makes sure that all involved bios have mixable attributes 727 * set properly. 728 */ 729 if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || 730 (req->cmd_flags & REQ_FAILFAST_MASK) != 731 (next->cmd_flags & REQ_FAILFAST_MASK)) { 732 blk_rq_set_mixed_merge(req); 733 blk_rq_set_mixed_merge(next); 734 } 735 736 /* 737 * At this point we have either done a back merge or front merge. We 738 * need the smaller start_time_ns of the merged requests to be the 739 * current request for accounting purposes. 740 */ 741 if (next->start_time_ns < req->start_time_ns) 742 req->start_time_ns = next->start_time_ns; 743 744 req->biotail->bi_next = next->bio; 745 req->biotail = next->biotail; 746 747 req->__data_len += blk_rq_bytes(next); 748 749 if (req_op(req) != REQ_OP_DISCARD) 750 elv_merge_requests(q, req, next); 751 752 /* 753 * 'next' is going away, so update stats accordingly 754 */ 755 blk_account_io_merge(next); 756 757 req->ioprio = ioprio_best(req->ioprio, next->ioprio); 758 if (blk_rq_cpu_valid(next)) 759 req->cpu = next->cpu; 760 761 /* 762 * ownership of bio passed from next to req, return 'next' for 763 * the caller to free 764 */ 765 next->bio = NULL; 766 return next; 767 } 768 769 struct request *attempt_back_merge(struct request_queue *q, struct request *rq) 770 { 771 struct request *next = elv_latter_request(q, rq); 772 773 if (next) 774 return attempt_merge(q, rq, next); 775 776 return NULL; 777 } 778 779 struct request *attempt_front_merge(struct request_queue *q, struct request *rq) 780 { 781 struct request *prev = elv_former_request(q, rq); 782 783 if (prev) 784 return attempt_merge(q, prev, rq); 785 786 return NULL; 787 } 788 789 int blk_attempt_req_merge(struct request_queue *q, struct request *rq, 790 struct request *next) 791 { 792 struct elevator_queue *e = q->elevator; 793 struct request *free; 794 795 if (!e->uses_mq && e->type->ops.sq.elevator_allow_rq_merge_fn) 796 if (!e->type->ops.sq.elevator_allow_rq_merge_fn(q, rq, next)) 797 return 0; 798 799 free = attempt_merge(q, rq, next); 800 if (free) { 801 __blk_put_request(q, free); 802 return 1; 803 } 804 805 return 0; 806 } 807 808 bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 809 { 810 if (!rq_mergeable(rq) || !bio_mergeable(bio)) 811 return false; 812 813 if (req_op(rq) != bio_op(bio)) 814 return false; 815 816 /* different data direction or already started, don't merge */ 817 if (bio_data_dir(bio) != rq_data_dir(rq)) 818 return false; 819 820 /* must be same device and not a special request */ 821 if (rq->rq_disk != bio->bi_disk || req_no_special_merge(rq)) 822 return false; 823 824 /* only merge integrity protected bio into ditto rq */ 825 if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 826 return false; 827 828 /* must be using the same buffer */ 829 if (req_op(rq) == REQ_OP_WRITE_SAME && 830 !blk_write_same_mergeable(rq->bio, bio)) 831 return false; 832 833 /* 834 * Don't allow merge of different write hints, or for a hint with 835 * non-hint IO. 836 */ 837 if (rq->write_hint != bio->bi_write_hint) 838 return false; 839 840 return true; 841 } 842 843 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) 844 { 845 if (req_op(rq) == REQ_OP_DISCARD && 846 queue_max_discard_segments(rq->q) > 1) 847 return ELEVATOR_DISCARD_MERGE; 848 else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 849 return ELEVATOR_BACK_MERGE; 850 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 851 return ELEVATOR_FRONT_MERGE; 852 return ELEVATOR_NO_MERGE; 853 } 854