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 unsigned bvecs = 0; 98 99 bio_for_each_segment(bv, bio, iter) { 100 /* 101 * With arbitrary bio size, the incoming bio may be very 102 * big. We have to split the bio into small bios so that 103 * each holds at most BIO_MAX_PAGES bvecs because 104 * bio_clone() can fail to allocate big bvecs. 105 * 106 * It should have been better to apply the limit per 107 * request queue in which bio_clone() is involved, 108 * instead of globally. The biggest blocker is the 109 * bio_clone() in bio bounce. 110 * 111 * If bio is splitted by this reason, we should have 112 * allowed to continue bios merging, but don't do 113 * that now for making the change simple. 114 * 115 * TODO: deal with bio bounce's bio_clone() gracefully 116 * and convert the global limit into per-queue limit. 117 */ 118 if (bvecs++ >= BIO_MAX_PAGES) 119 goto split; 120 121 /* 122 * If the queue doesn't support SG gaps and adding this 123 * offset would create a gap, disallow it. 124 */ 125 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset)) 126 goto split; 127 128 if (sectors + (bv.bv_len >> 9) > max_sectors) { 129 /* 130 * Consider this a new segment if we're splitting in 131 * the middle of this vector. 132 */ 133 if (nsegs < queue_max_segments(q) && 134 sectors < max_sectors) { 135 nsegs++; 136 sectors = max_sectors; 137 } 138 if (sectors) 139 goto split; 140 /* Make this single bvec as the 1st segment */ 141 } 142 143 if (bvprvp && blk_queue_cluster(q)) { 144 if (seg_size + bv.bv_len > queue_max_segment_size(q)) 145 goto new_segment; 146 if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv)) 147 goto new_segment; 148 if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv)) 149 goto new_segment; 150 151 seg_size += bv.bv_len; 152 bvprv = bv; 153 bvprvp = &bvprv; 154 sectors += bv.bv_len >> 9; 155 156 if (nsegs == 1 && seg_size > front_seg_size) 157 front_seg_size = seg_size; 158 continue; 159 } 160 new_segment: 161 if (nsegs == queue_max_segments(q)) 162 goto split; 163 164 nsegs++; 165 bvprv = bv; 166 bvprvp = &bvprv; 167 seg_size = bv.bv_len; 168 sectors += bv.bv_len >> 9; 169 170 if (nsegs == 1 && seg_size > front_seg_size) 171 front_seg_size = seg_size; 172 } 173 174 do_split = false; 175 split: 176 *segs = nsegs; 177 178 if (do_split) { 179 new = bio_split(bio, sectors, GFP_NOIO, bs); 180 if (new) 181 bio = new; 182 } 183 184 bio->bi_seg_front_size = front_seg_size; 185 if (seg_size > bio->bi_seg_back_size) 186 bio->bi_seg_back_size = seg_size; 187 188 return do_split ? new : NULL; 189 } 190 191 void blk_queue_split(struct request_queue *q, struct bio **bio, 192 struct bio_set *bs) 193 { 194 struct bio *split, *res; 195 unsigned nsegs; 196 197 switch (bio_op(*bio)) { 198 case REQ_OP_DISCARD: 199 case REQ_OP_SECURE_ERASE: 200 split = blk_bio_discard_split(q, *bio, bs, &nsegs); 201 break; 202 case REQ_OP_WRITE_ZEROES: 203 split = NULL; 204 nsegs = (*bio)->bi_phys_segments; 205 break; 206 case REQ_OP_WRITE_SAME: 207 split = blk_bio_write_same_split(q, *bio, bs, &nsegs); 208 break; 209 default: 210 split = blk_bio_segment_split(q, *bio, q->bio_split, &nsegs); 211 break; 212 } 213 214 /* physical segments can be figured out during splitting */ 215 res = split ? split : *bio; 216 res->bi_phys_segments = nsegs; 217 bio_set_flag(res, BIO_SEG_VALID); 218 219 if (split) { 220 /* there isn't chance to merge the splitted bio */ 221 split->bi_opf |= REQ_NOMERGE; 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 int ll_merge_requests_fn(struct request_queue *q, struct request *req, 564 struct request *next) 565 { 566 int total_phys_segments; 567 unsigned int seg_size = 568 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; 569 570 /* 571 * First check if the either of the requests are re-queued 572 * requests. Can't merge them if they are. 573 */ 574 if (req_no_special_merge(req) || req_no_special_merge(next)) 575 return 0; 576 577 if (req_gap_back_merge(req, next->bio)) 578 return 0; 579 580 /* 581 * Will it become too large? 582 */ 583 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 584 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 585 return 0; 586 587 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 588 if (blk_phys_contig_segment(q, req->biotail, next->bio)) { 589 if (req->nr_phys_segments == 1) 590 req->bio->bi_seg_front_size = seg_size; 591 if (next->nr_phys_segments == 1) 592 next->biotail->bi_seg_back_size = seg_size; 593 total_phys_segments--; 594 } 595 596 if (total_phys_segments > queue_max_segments(q)) 597 return 0; 598 599 if (blk_integrity_merge_rq(q, req, next) == false) 600 return 0; 601 602 /* Merge is OK... */ 603 req->nr_phys_segments = total_phys_segments; 604 return 1; 605 } 606 607 /** 608 * blk_rq_set_mixed_merge - mark a request as mixed merge 609 * @rq: request to mark as mixed merge 610 * 611 * Description: 612 * @rq is about to be mixed merged. Make sure the attributes 613 * which can be mixed are set in each bio and mark @rq as mixed 614 * merged. 615 */ 616 void blk_rq_set_mixed_merge(struct request *rq) 617 { 618 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; 619 struct bio *bio; 620 621 if (rq->rq_flags & RQF_MIXED_MERGE) 622 return; 623 624 /* 625 * @rq will no longer represent mixable attributes for all the 626 * contained bios. It will just track those of the first one. 627 * Distributes the attributs to each bio. 628 */ 629 for (bio = rq->bio; bio; bio = bio->bi_next) { 630 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 631 (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 632 bio->bi_opf |= ff; 633 } 634 rq->rq_flags |= RQF_MIXED_MERGE; 635 } 636 637 static void blk_account_io_merge(struct request *req) 638 { 639 if (blk_do_io_stat(req)) { 640 struct hd_struct *part; 641 int cpu; 642 643 cpu = part_stat_lock(); 644 part = req->part; 645 646 part_round_stats(cpu, part); 647 part_dec_in_flight(part, rq_data_dir(req)); 648 649 hd_struct_put(part); 650 part_stat_unlock(); 651 } 652 } 653 654 /* 655 * For non-mq, this has to be called with the request spinlock acquired. 656 * For mq with scheduling, the appropriate queue wide lock should be held. 657 */ 658 static struct request *attempt_merge(struct request_queue *q, 659 struct request *req, struct request *next) 660 { 661 if (!rq_mergeable(req) || !rq_mergeable(next)) 662 return NULL; 663 664 if (req_op(req) != req_op(next)) 665 return NULL; 666 667 /* 668 * not contiguous 669 */ 670 if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)) 671 return NULL; 672 673 if (rq_data_dir(req) != rq_data_dir(next) 674 || req->rq_disk != next->rq_disk 675 || req_no_special_merge(next)) 676 return NULL; 677 678 if (req_op(req) == REQ_OP_WRITE_SAME && 679 !blk_write_same_mergeable(req->bio, next->bio)) 680 return NULL; 681 682 /* 683 * If we are allowed to merge, then append bio list 684 * from next to rq and release next. merge_requests_fn 685 * will have updated segment counts, update sector 686 * counts here. 687 */ 688 if (!ll_merge_requests_fn(q, req, next)) 689 return NULL; 690 691 /* 692 * If failfast settings disagree or any of the two is already 693 * a mixed merge, mark both as mixed before proceeding. This 694 * makes sure that all involved bios have mixable attributes 695 * set properly. 696 */ 697 if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || 698 (req->cmd_flags & REQ_FAILFAST_MASK) != 699 (next->cmd_flags & REQ_FAILFAST_MASK)) { 700 blk_rq_set_mixed_merge(req); 701 blk_rq_set_mixed_merge(next); 702 } 703 704 /* 705 * At this point we have either done a back merge 706 * or front merge. We need the smaller start_time of 707 * the merged requests to be the current request 708 * for accounting purposes. 709 */ 710 if (time_after(req->start_time, next->start_time)) 711 req->start_time = next->start_time; 712 713 req->biotail->bi_next = next->bio; 714 req->biotail = next->biotail; 715 716 req->__data_len += blk_rq_bytes(next); 717 718 elv_merge_requests(q, req, next); 719 720 /* 721 * 'next' is going away, so update stats accordingly 722 */ 723 blk_account_io_merge(next); 724 725 req->ioprio = ioprio_best(req->ioprio, next->ioprio); 726 if (blk_rq_cpu_valid(next)) 727 req->cpu = next->cpu; 728 729 /* 730 * ownership of bio passed from next to req, return 'next' for 731 * the caller to free 732 */ 733 next->bio = NULL; 734 return next; 735 } 736 737 struct request *attempt_back_merge(struct request_queue *q, struct request *rq) 738 { 739 struct request *next = elv_latter_request(q, rq); 740 741 if (next) 742 return attempt_merge(q, rq, next); 743 744 return NULL; 745 } 746 747 struct request *attempt_front_merge(struct request_queue *q, struct request *rq) 748 { 749 struct request *prev = elv_former_request(q, rq); 750 751 if (prev) 752 return attempt_merge(q, prev, rq); 753 754 return NULL; 755 } 756 757 int blk_attempt_req_merge(struct request_queue *q, struct request *rq, 758 struct request *next) 759 { 760 struct elevator_queue *e = q->elevator; 761 struct request *free; 762 763 if (!e->uses_mq && e->type->ops.sq.elevator_allow_rq_merge_fn) 764 if (!e->type->ops.sq.elevator_allow_rq_merge_fn(q, rq, next)) 765 return 0; 766 767 free = attempt_merge(q, rq, next); 768 if (free) { 769 __blk_put_request(q, free); 770 return 1; 771 } 772 773 return 0; 774 } 775 776 bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 777 { 778 if (!rq_mergeable(rq) || !bio_mergeable(bio)) 779 return false; 780 781 if (req_op(rq) != bio_op(bio)) 782 return false; 783 784 /* different data direction or already started, don't merge */ 785 if (bio_data_dir(bio) != rq_data_dir(rq)) 786 return false; 787 788 /* must be same device and not a special request */ 789 if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq)) 790 return false; 791 792 /* only merge integrity protected bio into ditto rq */ 793 if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 794 return false; 795 796 /* must be using the same buffer */ 797 if (req_op(rq) == REQ_OP_WRITE_SAME && 798 !blk_write_same_mergeable(rq->bio, bio)) 799 return false; 800 801 return true; 802 } 803 804 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) 805 { 806 if (req_op(rq) == REQ_OP_DISCARD && 807 queue_max_discard_segments(rq->q) > 1) 808 return ELEVATOR_DISCARD_MERGE; 809 else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 810 return ELEVATOR_BACK_MERGE; 811 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 812 return ELEVATOR_FRONT_MERGE; 813 return ELEVATOR_NO_MERGE; 814 } 815