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 if (sectors) 132 goto split; 133 /* Make this single bvec as the 1st segment */ 134 } 135 136 if (bvprvp && blk_queue_cluster(q)) { 137 if (seg_size + bv.bv_len > queue_max_segment_size(q)) 138 goto new_segment; 139 if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv)) 140 goto new_segment; 141 if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv)) 142 goto new_segment; 143 144 seg_size += bv.bv_len; 145 bvprv = bv; 146 bvprvp = &bvprv; 147 sectors += bv.bv_len >> 9; 148 149 if (nsegs == 1 && seg_size > front_seg_size) 150 front_seg_size = seg_size; 151 continue; 152 } 153 new_segment: 154 if (nsegs == queue_max_segments(q)) 155 goto split; 156 157 nsegs++; 158 bvprv = bv; 159 bvprvp = &bvprv; 160 seg_size = bv.bv_len; 161 sectors += bv.bv_len >> 9; 162 163 if (nsegs == 1 && seg_size > front_seg_size) 164 front_seg_size = seg_size; 165 } 166 167 do_split = false; 168 split: 169 *segs = nsegs; 170 171 if (do_split) { 172 new = bio_split(bio, sectors, GFP_NOIO, bs); 173 if (new) 174 bio = new; 175 } 176 177 bio->bi_seg_front_size = front_seg_size; 178 if (seg_size > bio->bi_seg_back_size) 179 bio->bi_seg_back_size = seg_size; 180 181 return do_split ? new : NULL; 182 } 183 184 void blk_queue_split(struct request_queue *q, struct bio **bio) 185 { 186 struct bio *split, *res; 187 unsigned nsegs; 188 189 switch (bio_op(*bio)) { 190 case REQ_OP_DISCARD: 191 case REQ_OP_SECURE_ERASE: 192 split = blk_bio_discard_split(q, *bio, q->bio_split, &nsegs); 193 break; 194 case REQ_OP_WRITE_ZEROES: 195 split = blk_bio_write_zeroes_split(q, *bio, q->bio_split, &nsegs); 196 break; 197 case REQ_OP_WRITE_SAME: 198 split = blk_bio_write_same_split(q, *bio, q->bio_split, &nsegs); 199 break; 200 default: 201 split = blk_bio_segment_split(q, *bio, q->bio_split, &nsegs); 202 break; 203 } 204 205 /* physical segments can be figured out during splitting */ 206 res = split ? split : *bio; 207 res->bi_phys_segments = nsegs; 208 bio_set_flag(res, BIO_SEG_VALID); 209 210 if (split) { 211 /* there isn't chance to merge the splitted bio */ 212 split->bi_opf |= REQ_NOMERGE; 213 214 bio_chain(split, *bio); 215 trace_block_split(q, split, (*bio)->bi_iter.bi_sector); 216 generic_make_request(*bio); 217 *bio = split; 218 } 219 } 220 EXPORT_SYMBOL(blk_queue_split); 221 222 static unsigned int __blk_recalc_rq_segments(struct request_queue *q, 223 struct bio *bio, 224 bool no_sg_merge) 225 { 226 struct bio_vec bv, bvprv = { NULL }; 227 int cluster, prev = 0; 228 unsigned int seg_size, nr_phys_segs; 229 struct bio *fbio, *bbio; 230 struct bvec_iter iter; 231 232 if (!bio) 233 return 0; 234 235 switch (bio_op(bio)) { 236 case REQ_OP_DISCARD: 237 case REQ_OP_SECURE_ERASE: 238 case REQ_OP_WRITE_ZEROES: 239 return 0; 240 case REQ_OP_WRITE_SAME: 241 return 1; 242 } 243 244 fbio = bio; 245 cluster = blk_queue_cluster(q); 246 seg_size = 0; 247 nr_phys_segs = 0; 248 for_each_bio(bio) { 249 bio_for_each_segment(bv, bio, iter) { 250 /* 251 * If SG merging is disabled, each bio vector is 252 * a segment 253 */ 254 if (no_sg_merge) 255 goto new_segment; 256 257 if (prev && cluster) { 258 if (seg_size + bv.bv_len 259 > queue_max_segment_size(q)) 260 goto new_segment; 261 if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv)) 262 goto new_segment; 263 if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv)) 264 goto new_segment; 265 266 seg_size += bv.bv_len; 267 bvprv = bv; 268 continue; 269 } 270 new_segment: 271 if (nr_phys_segs == 1 && seg_size > 272 fbio->bi_seg_front_size) 273 fbio->bi_seg_front_size = seg_size; 274 275 nr_phys_segs++; 276 bvprv = bv; 277 prev = 1; 278 seg_size = bv.bv_len; 279 } 280 bbio = bio; 281 } 282 283 if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size) 284 fbio->bi_seg_front_size = seg_size; 285 if (seg_size > bbio->bi_seg_back_size) 286 bbio->bi_seg_back_size = seg_size; 287 288 return nr_phys_segs; 289 } 290 291 void blk_recalc_rq_segments(struct request *rq) 292 { 293 bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE, 294 &rq->q->queue_flags); 295 296 rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio, 297 no_sg_merge); 298 } 299 300 void blk_recount_segments(struct request_queue *q, struct bio *bio) 301 { 302 unsigned short seg_cnt; 303 304 /* estimate segment number by bi_vcnt for non-cloned bio */ 305 if (bio_flagged(bio, BIO_CLONED)) 306 seg_cnt = bio_segments(bio); 307 else 308 seg_cnt = bio->bi_vcnt; 309 310 if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) && 311 (seg_cnt < queue_max_segments(q))) 312 bio->bi_phys_segments = seg_cnt; 313 else { 314 struct bio *nxt = bio->bi_next; 315 316 bio->bi_next = NULL; 317 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false); 318 bio->bi_next = nxt; 319 } 320 321 bio_set_flag(bio, BIO_SEG_VALID); 322 } 323 EXPORT_SYMBOL(blk_recount_segments); 324 325 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, 326 struct bio *nxt) 327 { 328 struct bio_vec end_bv = { NULL }, nxt_bv; 329 330 if (!blk_queue_cluster(q)) 331 return 0; 332 333 if (bio->bi_seg_back_size + nxt->bi_seg_front_size > 334 queue_max_segment_size(q)) 335 return 0; 336 337 if (!bio_has_data(bio)) 338 return 1; 339 340 bio_get_last_bvec(bio, &end_bv); 341 bio_get_first_bvec(nxt, &nxt_bv); 342 343 if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv)) 344 return 0; 345 346 /* 347 * bio and nxt are contiguous in memory; check if the queue allows 348 * these two to be merged into one 349 */ 350 if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv)) 351 return 1; 352 353 return 0; 354 } 355 356 static inline void 357 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, 358 struct scatterlist *sglist, struct bio_vec *bvprv, 359 struct scatterlist **sg, int *nsegs, int *cluster) 360 { 361 362 int nbytes = bvec->bv_len; 363 364 if (*sg && *cluster) { 365 if ((*sg)->length + nbytes > queue_max_segment_size(q)) 366 goto new_segment; 367 368 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) 369 goto new_segment; 370 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) 371 goto new_segment; 372 373 (*sg)->length += nbytes; 374 } else { 375 new_segment: 376 if (!*sg) 377 *sg = sglist; 378 else { 379 /* 380 * If the driver previously mapped a shorter 381 * list, we could see a termination bit 382 * prematurely unless it fully inits the sg 383 * table on each mapping. We KNOW that there 384 * must be more entries here or the driver 385 * would be buggy, so force clear the 386 * termination bit to avoid doing a full 387 * sg_init_table() in drivers for each command. 388 */ 389 sg_unmark_end(*sg); 390 *sg = sg_next(*sg); 391 } 392 393 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); 394 (*nsegs)++; 395 } 396 *bvprv = *bvec; 397 } 398 399 static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv, 400 struct scatterlist *sglist, struct scatterlist **sg) 401 { 402 *sg = sglist; 403 sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); 404 return 1; 405 } 406 407 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 408 struct scatterlist *sglist, 409 struct scatterlist **sg) 410 { 411 struct bio_vec bvec, bvprv = { NULL }; 412 struct bvec_iter iter; 413 int cluster = blk_queue_cluster(q), nsegs = 0; 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->rq_flags & RQF_SPECIAL_PAYLOAD) 434 nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg); 435 else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME) 436 nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg); 437 else if (rq->bio) 438 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg); 439 440 if (unlikely(rq->rq_flags & RQF_COPY_USER) && 441 (blk_rq_bytes(rq) & q->dma_pad_mask)) { 442 unsigned int pad_len = 443 (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1; 444 445 sg->length += pad_len; 446 rq->extra_len += pad_len; 447 } 448 449 if (q->dma_drain_size && q->dma_drain_needed(rq)) { 450 if (op_is_write(req_op(rq))) 451 memset(q->dma_drain_buffer, 0, q->dma_drain_size); 452 453 sg_unmark_end(sg); 454 sg = sg_next(sg); 455 sg_set_page(sg, virt_to_page(q->dma_drain_buffer), 456 q->dma_drain_size, 457 ((unsigned long)q->dma_drain_buffer) & 458 (PAGE_SIZE - 1)); 459 nsegs++; 460 rq->extra_len += q->dma_drain_size; 461 } 462 463 if (sg) 464 sg_mark_end(sg); 465 466 /* 467 * Something must have been wrong if the figured number of 468 * segment is bigger than number of req's physical segments 469 */ 470 WARN_ON(nsegs > blk_rq_nr_phys_segments(rq)); 471 472 return nsegs; 473 } 474 EXPORT_SYMBOL(blk_rq_map_sg); 475 476 static inline int ll_new_hw_segment(struct request_queue *q, 477 struct request *req, 478 struct bio *bio) 479 { 480 int nr_phys_segs = bio_phys_segments(q, bio); 481 482 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) 483 goto no_merge; 484 485 if (blk_integrity_merge_bio(q, req, bio) == false) 486 goto no_merge; 487 488 /* 489 * This will form the start of a new hw segment. Bump both 490 * counters. 491 */ 492 req->nr_phys_segments += nr_phys_segs; 493 return 1; 494 495 no_merge: 496 req_set_nomerge(q, req); 497 return 0; 498 } 499 500 int ll_back_merge_fn(struct request_queue *q, struct request *req, 501 struct bio *bio) 502 { 503 if (req_gap_back_merge(req, bio)) 504 return 0; 505 if (blk_integrity_rq(req) && 506 integrity_req_gap_back_merge(req, bio)) 507 return 0; 508 if (blk_rq_sectors(req) + bio_sectors(bio) > 509 blk_rq_get_max_sectors(req, blk_rq_pos(req))) { 510 req_set_nomerge(q, req); 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, bio->bi_iter.bi_sector)) { 532 req_set_nomerge(q, req); 533 return 0; 534 } 535 if (!bio_flagged(bio, BIO_SEG_VALID)) 536 blk_recount_segments(q, bio); 537 if (!bio_flagged(req->bio, BIO_SEG_VALID)) 538 blk_recount_segments(q, req->bio); 539 540 return ll_new_hw_segment(q, req, bio); 541 } 542 543 /* 544 * blk-mq uses req->special to carry normal driver per-request payload, it 545 * does not indicate a prepared command that we cannot merge with. 546 */ 547 static bool req_no_special_merge(struct request *req) 548 { 549 struct request_queue *q = req->q; 550 551 return !q->mq_ops && req->special; 552 } 553 554 static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 555 struct request *next) 556 { 557 int total_phys_segments; 558 unsigned int seg_size = 559 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; 560 561 /* 562 * First check if the either of the requests are re-queued 563 * requests. Can't merge them if they are. 564 */ 565 if (req_no_special_merge(req) || req_no_special_merge(next)) 566 return 0; 567 568 if (req_gap_back_merge(req, next->bio)) 569 return 0; 570 571 /* 572 * Will it become too large? 573 */ 574 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 575 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 576 return 0; 577 578 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 579 if (blk_phys_contig_segment(q, req->biotail, next->bio)) { 580 if (req->nr_phys_segments == 1) 581 req->bio->bi_seg_front_size = seg_size; 582 if (next->nr_phys_segments == 1) 583 next->biotail->bi_seg_back_size = seg_size; 584 total_phys_segments--; 585 } 586 587 if (total_phys_segments > queue_max_segments(q)) 588 return 0; 589 590 if (blk_integrity_merge_rq(q, req, next) == false) 591 return 0; 592 593 /* Merge is OK... */ 594 req->nr_phys_segments = total_phys_segments; 595 return 1; 596 } 597 598 /** 599 * blk_rq_set_mixed_merge - mark a request as mixed merge 600 * @rq: request to mark as mixed merge 601 * 602 * Description: 603 * @rq is about to be mixed merged. Make sure the attributes 604 * which can be mixed are set in each bio and mark @rq as mixed 605 * merged. 606 */ 607 void blk_rq_set_mixed_merge(struct request *rq) 608 { 609 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; 610 struct bio *bio; 611 612 if (rq->rq_flags & RQF_MIXED_MERGE) 613 return; 614 615 /* 616 * @rq will no longer represent mixable attributes for all the 617 * contained bios. It will just track those of the first one. 618 * Distributes the attributs to each bio. 619 */ 620 for (bio = rq->bio; bio; bio = bio->bi_next) { 621 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 622 (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 623 bio->bi_opf |= ff; 624 } 625 rq->rq_flags |= RQF_MIXED_MERGE; 626 } 627 628 static void blk_account_io_merge(struct request *req) 629 { 630 if (blk_do_io_stat(req)) { 631 struct hd_struct *part; 632 int cpu; 633 634 cpu = part_stat_lock(); 635 part = req->part; 636 637 part_round_stats(req->q, cpu, part); 638 part_dec_in_flight(req->q, part, rq_data_dir(req)); 639 640 hd_struct_put(part); 641 part_stat_unlock(); 642 } 643 } 644 645 /* 646 * For non-mq, this has to be called with the request spinlock acquired. 647 * For mq with scheduling, the appropriate queue wide lock should be held. 648 */ 649 static struct request *attempt_merge(struct request_queue *q, 650 struct request *req, struct request *next) 651 { 652 if (!q->mq_ops) 653 lockdep_assert_held(q->queue_lock); 654 655 if (!rq_mergeable(req) || !rq_mergeable(next)) 656 return NULL; 657 658 if (req_op(req) != req_op(next)) 659 return NULL; 660 661 /* 662 * not contiguous 663 */ 664 if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)) 665 return NULL; 666 667 if (rq_data_dir(req) != rq_data_dir(next) 668 || req->rq_disk != next->rq_disk 669 || req_no_special_merge(next)) 670 return NULL; 671 672 if (req_op(req) == REQ_OP_WRITE_SAME && 673 !blk_write_same_mergeable(req->bio, next->bio)) 674 return NULL; 675 676 /* 677 * Don't allow merge of different write hints, or for a hint with 678 * non-hint IO. 679 */ 680 if (req->write_hint != next->write_hint) 681 return NULL; 682 683 /* 684 * If we are allowed to merge, then append bio list 685 * from next to rq and release next. merge_requests_fn 686 * will have updated segment counts, update sector 687 * counts here. 688 */ 689 if (!ll_merge_requests_fn(q, req, next)) 690 return NULL; 691 692 /* 693 * If failfast settings disagree or any of the two is already 694 * a mixed merge, mark both as mixed before proceeding. This 695 * makes sure that all involved bios have mixable attributes 696 * set properly. 697 */ 698 if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || 699 (req->cmd_flags & REQ_FAILFAST_MASK) != 700 (next->cmd_flags & REQ_FAILFAST_MASK)) { 701 blk_rq_set_mixed_merge(req); 702 blk_rq_set_mixed_merge(next); 703 } 704 705 /* 706 * At this point we have either done a back merge 707 * or front merge. We need the smaller start_time of 708 * the merged requests to be the current request 709 * for accounting purposes. 710 */ 711 if (time_after(req->start_time, next->start_time)) 712 req->start_time = next->start_time; 713 714 req->biotail->bi_next = next->bio; 715 req->biotail = next->biotail; 716 717 req->__data_len += blk_rq_bytes(next); 718 719 elv_merge_requests(q, req, next); 720 721 /* 722 * 'next' is going away, so update stats accordingly 723 */ 724 blk_account_io_merge(next); 725 726 req->ioprio = ioprio_best(req->ioprio, next->ioprio); 727 if (blk_rq_cpu_valid(next)) 728 req->cpu = next->cpu; 729 730 /* 731 * ownership of bio passed from next to req, return 'next' for 732 * the caller to free 733 */ 734 next->bio = NULL; 735 return next; 736 } 737 738 struct request *attempt_back_merge(struct request_queue *q, struct request *rq) 739 { 740 struct request *next = elv_latter_request(q, rq); 741 742 if (next) 743 return attempt_merge(q, rq, next); 744 745 return NULL; 746 } 747 748 struct request *attempt_front_merge(struct request_queue *q, struct request *rq) 749 { 750 struct request *prev = elv_former_request(q, rq); 751 752 if (prev) 753 return attempt_merge(q, prev, rq); 754 755 return NULL; 756 } 757 758 int blk_attempt_req_merge(struct request_queue *q, struct request *rq, 759 struct request *next) 760 { 761 struct elevator_queue *e = q->elevator; 762 struct request *free; 763 764 if (!e->uses_mq && e->type->ops.sq.elevator_allow_rq_merge_fn) 765 if (!e->type->ops.sq.elevator_allow_rq_merge_fn(q, rq, next)) 766 return 0; 767 768 free = attempt_merge(q, rq, next); 769 if (free) { 770 __blk_put_request(q, free); 771 return 1; 772 } 773 774 return 0; 775 } 776 777 bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 778 { 779 if (!rq_mergeable(rq) || !bio_mergeable(bio)) 780 return false; 781 782 if (req_op(rq) != bio_op(bio)) 783 return false; 784 785 /* different data direction or already started, don't merge */ 786 if (bio_data_dir(bio) != rq_data_dir(rq)) 787 return false; 788 789 /* must be same device and not a special request */ 790 if (rq->rq_disk != bio->bi_disk || req_no_special_merge(rq)) 791 return false; 792 793 /* only merge integrity protected bio into ditto rq */ 794 if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 795 return false; 796 797 /* must be using the same buffer */ 798 if (req_op(rq) == REQ_OP_WRITE_SAME && 799 !blk_write_same_mergeable(rq->bio, bio)) 800 return false; 801 802 /* 803 * Don't allow merge of different write hints, or for a hint with 804 * non-hint IO. 805 */ 806 if (rq->write_hint != bio->bi_write_hint) 807 return false; 808 809 return true; 810 } 811 812 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) 813 { 814 if (req_op(rq) == REQ_OP_DISCARD && 815 queue_max_discard_segments(rq->q) > 1) 816 return ELEVATOR_DISCARD_MERGE; 817 else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 818 return ELEVATOR_BACK_MERGE; 819 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 820 return ELEVATOR_FRONT_MERGE; 821 return ELEVATOR_NO_MERGE; 822 } 823