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_SAME: 203 split = blk_bio_write_same_split(q, *bio, bs, &nsegs); 204 break; 205 default: 206 split = blk_bio_segment_split(q, *bio, q->bio_split, &nsegs); 207 break; 208 } 209 210 /* physical segments can be figured out during splitting */ 211 res = split ? split : *bio; 212 res->bi_phys_segments = nsegs; 213 bio_set_flag(res, BIO_SEG_VALID); 214 215 if (split) { 216 /* there isn't chance to merge the splitted bio */ 217 split->bi_opf |= REQ_NOMERGE; 218 219 bio_chain(split, *bio); 220 trace_block_split(q, split, (*bio)->bi_iter.bi_sector); 221 generic_make_request(*bio); 222 *bio = split; 223 } 224 } 225 EXPORT_SYMBOL(blk_queue_split); 226 227 static unsigned int __blk_recalc_rq_segments(struct request_queue *q, 228 struct bio *bio, 229 bool no_sg_merge) 230 { 231 struct bio_vec bv, bvprv = { NULL }; 232 int cluster, prev = 0; 233 unsigned int seg_size, nr_phys_segs; 234 struct bio *fbio, *bbio; 235 struct bvec_iter iter; 236 237 if (!bio) 238 return 0; 239 240 /* 241 * This should probably be returning 0, but blk_add_request_payload() 242 * (Christoph!!!!) 243 */ 244 if (bio_op(bio) == REQ_OP_DISCARD || bio_op(bio) == REQ_OP_SECURE_ERASE) 245 return 1; 246 247 if (bio_op(bio) == REQ_OP_WRITE_SAME) 248 return 1; 249 250 fbio = bio; 251 cluster = blk_queue_cluster(q); 252 seg_size = 0; 253 nr_phys_segs = 0; 254 for_each_bio(bio) { 255 bio_for_each_segment(bv, bio, iter) { 256 /* 257 * If SG merging is disabled, each bio vector is 258 * a segment 259 */ 260 if (no_sg_merge) 261 goto new_segment; 262 263 if (prev && cluster) { 264 if (seg_size + bv.bv_len 265 > queue_max_segment_size(q)) 266 goto new_segment; 267 if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv)) 268 goto new_segment; 269 if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv)) 270 goto new_segment; 271 272 seg_size += bv.bv_len; 273 bvprv = bv; 274 continue; 275 } 276 new_segment: 277 if (nr_phys_segs == 1 && seg_size > 278 fbio->bi_seg_front_size) 279 fbio->bi_seg_front_size = seg_size; 280 281 nr_phys_segs++; 282 bvprv = bv; 283 prev = 1; 284 seg_size = bv.bv_len; 285 } 286 bbio = bio; 287 } 288 289 if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size) 290 fbio->bi_seg_front_size = seg_size; 291 if (seg_size > bbio->bi_seg_back_size) 292 bbio->bi_seg_back_size = seg_size; 293 294 return nr_phys_segs; 295 } 296 297 void blk_recalc_rq_segments(struct request *rq) 298 { 299 bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE, 300 &rq->q->queue_flags); 301 302 rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio, 303 no_sg_merge); 304 } 305 306 void blk_recount_segments(struct request_queue *q, struct bio *bio) 307 { 308 unsigned short seg_cnt; 309 310 /* estimate segment number by bi_vcnt for non-cloned bio */ 311 if (bio_flagged(bio, BIO_CLONED)) 312 seg_cnt = bio_segments(bio); 313 else 314 seg_cnt = bio->bi_vcnt; 315 316 if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) && 317 (seg_cnt < queue_max_segments(q))) 318 bio->bi_phys_segments = seg_cnt; 319 else { 320 struct bio *nxt = bio->bi_next; 321 322 bio->bi_next = NULL; 323 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false); 324 bio->bi_next = nxt; 325 } 326 327 bio_set_flag(bio, BIO_SEG_VALID); 328 } 329 EXPORT_SYMBOL(blk_recount_segments); 330 331 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, 332 struct bio *nxt) 333 { 334 struct bio_vec end_bv = { NULL }, nxt_bv; 335 336 if (!blk_queue_cluster(q)) 337 return 0; 338 339 if (bio->bi_seg_back_size + nxt->bi_seg_front_size > 340 queue_max_segment_size(q)) 341 return 0; 342 343 if (!bio_has_data(bio)) 344 return 1; 345 346 bio_get_last_bvec(bio, &end_bv); 347 bio_get_first_bvec(nxt, &nxt_bv); 348 349 if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv)) 350 return 0; 351 352 /* 353 * bio and nxt are contiguous in memory; check if the queue allows 354 * these two to be merged into one 355 */ 356 if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv)) 357 return 1; 358 359 return 0; 360 } 361 362 static inline void 363 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, 364 struct scatterlist *sglist, struct bio_vec *bvprv, 365 struct scatterlist **sg, int *nsegs, int *cluster) 366 { 367 368 int nbytes = bvec->bv_len; 369 370 if (*sg && *cluster) { 371 if ((*sg)->length + nbytes > queue_max_segment_size(q)) 372 goto new_segment; 373 374 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) 375 goto new_segment; 376 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) 377 goto new_segment; 378 379 (*sg)->length += nbytes; 380 } else { 381 new_segment: 382 if (!*sg) 383 *sg = sglist; 384 else { 385 /* 386 * If the driver previously mapped a shorter 387 * list, we could see a termination bit 388 * prematurely unless it fully inits the sg 389 * table on each mapping. We KNOW that there 390 * must be more entries here or the driver 391 * would be buggy, so force clear the 392 * termination bit to avoid doing a full 393 * sg_init_table() in drivers for each command. 394 */ 395 sg_unmark_end(*sg); 396 *sg = sg_next(*sg); 397 } 398 399 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); 400 (*nsegs)++; 401 } 402 *bvprv = *bvec; 403 } 404 405 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 406 struct scatterlist *sglist, 407 struct scatterlist **sg) 408 { 409 struct bio_vec bvec, bvprv = { NULL }; 410 struct bvec_iter iter; 411 int nsegs, cluster; 412 413 nsegs = 0; 414 cluster = blk_queue_cluster(q); 415 416 switch (bio_op(bio)) { 417 case REQ_OP_DISCARD: 418 case REQ_OP_SECURE_ERASE: 419 /* 420 * This is a hack - drivers should be neither modifying the 421 * biovec, nor relying on bi_vcnt - but because of 422 * blk_add_request_payload(), a discard bio may or may not have 423 * a payload we need to set up here (thank you Christoph) and 424 * bi_vcnt is really the only way of telling if we need to. 425 */ 426 if (!bio->bi_vcnt) 427 return 0; 428 /* Fall through */ 429 case REQ_OP_WRITE_SAME: 430 *sg = sglist; 431 bvec = bio_iovec(bio); 432 sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset); 433 return 1; 434 default: 435 break; 436 } 437 438 for_each_bio(bio) 439 bio_for_each_segment(bvec, bio, iter) 440 __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg, 441 &nsegs, &cluster); 442 443 return nsegs; 444 } 445 446 /* 447 * map a request to scatterlist, return number of sg entries setup. Caller 448 * must make sure sg can hold rq->nr_phys_segments entries 449 */ 450 int blk_rq_map_sg(struct request_queue *q, struct request *rq, 451 struct scatterlist *sglist) 452 { 453 struct scatterlist *sg = NULL; 454 int nsegs = 0; 455 456 if (rq->bio) 457 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg); 458 459 if (unlikely(rq->cmd_flags & REQ_COPY_USER) && 460 (blk_rq_bytes(rq) & q->dma_pad_mask)) { 461 unsigned int pad_len = 462 (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1; 463 464 sg->length += pad_len; 465 rq->extra_len += pad_len; 466 } 467 468 if (q->dma_drain_size && q->dma_drain_needed(rq)) { 469 if (op_is_write(req_op(rq))) 470 memset(q->dma_drain_buffer, 0, q->dma_drain_size); 471 472 sg_unmark_end(sg); 473 sg = sg_next(sg); 474 sg_set_page(sg, virt_to_page(q->dma_drain_buffer), 475 q->dma_drain_size, 476 ((unsigned long)q->dma_drain_buffer) & 477 (PAGE_SIZE - 1)); 478 nsegs++; 479 rq->extra_len += q->dma_drain_size; 480 } 481 482 if (sg) 483 sg_mark_end(sg); 484 485 /* 486 * Something must have been wrong if the figured number of 487 * segment is bigger than number of req's physical segments 488 */ 489 WARN_ON(nsegs > rq->nr_phys_segments); 490 491 return nsegs; 492 } 493 EXPORT_SYMBOL(blk_rq_map_sg); 494 495 static inline int ll_new_hw_segment(struct request_queue *q, 496 struct request *req, 497 struct bio *bio) 498 { 499 int nr_phys_segs = bio_phys_segments(q, bio); 500 501 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) 502 goto no_merge; 503 504 if (blk_integrity_merge_bio(q, req, bio) == false) 505 goto no_merge; 506 507 /* 508 * This will form the start of a new hw segment. Bump both 509 * counters. 510 */ 511 req->nr_phys_segments += nr_phys_segs; 512 return 1; 513 514 no_merge: 515 req->cmd_flags |= REQ_NOMERGE; 516 if (req == q->last_merge) 517 q->last_merge = NULL; 518 return 0; 519 } 520 521 int ll_back_merge_fn(struct request_queue *q, struct request *req, 522 struct bio *bio) 523 { 524 if (req_gap_back_merge(req, bio)) 525 return 0; 526 if (blk_integrity_rq(req) && 527 integrity_req_gap_back_merge(req, bio)) 528 return 0; 529 if (blk_rq_sectors(req) + bio_sectors(bio) > 530 blk_rq_get_max_sectors(req, blk_rq_pos(req))) { 531 req->cmd_flags |= REQ_NOMERGE; 532 if (req == q->last_merge) 533 q->last_merge = NULL; 534 return 0; 535 } 536 if (!bio_flagged(req->biotail, BIO_SEG_VALID)) 537 blk_recount_segments(q, req->biotail); 538 if (!bio_flagged(bio, BIO_SEG_VALID)) 539 blk_recount_segments(q, bio); 540 541 return ll_new_hw_segment(q, req, bio); 542 } 543 544 int ll_front_merge_fn(struct request_queue *q, struct request *req, 545 struct bio *bio) 546 { 547 548 if (req_gap_front_merge(req, bio)) 549 return 0; 550 if (blk_integrity_rq(req) && 551 integrity_req_gap_front_merge(req, bio)) 552 return 0; 553 if (blk_rq_sectors(req) + bio_sectors(bio) > 554 blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { 555 req->cmd_flags |= REQ_NOMERGE; 556 if (req == q->last_merge) 557 q->last_merge = NULL; 558 return 0; 559 } 560 if (!bio_flagged(bio, BIO_SEG_VALID)) 561 blk_recount_segments(q, bio); 562 if (!bio_flagged(req->bio, BIO_SEG_VALID)) 563 blk_recount_segments(q, req->bio); 564 565 return ll_new_hw_segment(q, req, bio); 566 } 567 568 /* 569 * blk-mq uses req->special to carry normal driver per-request payload, it 570 * does not indicate a prepared command that we cannot merge with. 571 */ 572 static bool req_no_special_merge(struct request *req) 573 { 574 struct request_queue *q = req->q; 575 576 return !q->mq_ops && req->special; 577 } 578 579 static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 580 struct request *next) 581 { 582 int total_phys_segments; 583 unsigned int seg_size = 584 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; 585 586 /* 587 * First check if the either of the requests are re-queued 588 * requests. Can't merge them if they are. 589 */ 590 if (req_no_special_merge(req) || req_no_special_merge(next)) 591 return 0; 592 593 if (req_gap_back_merge(req, next->bio)) 594 return 0; 595 596 /* 597 * Will it become too large? 598 */ 599 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 600 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 601 return 0; 602 603 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 604 if (blk_phys_contig_segment(q, req->biotail, next->bio)) { 605 if (req->nr_phys_segments == 1) 606 req->bio->bi_seg_front_size = seg_size; 607 if (next->nr_phys_segments == 1) 608 next->biotail->bi_seg_back_size = seg_size; 609 total_phys_segments--; 610 } 611 612 if (total_phys_segments > queue_max_segments(q)) 613 return 0; 614 615 if (blk_integrity_merge_rq(q, req, next) == false) 616 return 0; 617 618 /* Merge is OK... */ 619 req->nr_phys_segments = total_phys_segments; 620 return 1; 621 } 622 623 /** 624 * blk_rq_set_mixed_merge - mark a request as mixed merge 625 * @rq: request to mark as mixed merge 626 * 627 * Description: 628 * @rq is about to be mixed merged. Make sure the attributes 629 * which can be mixed are set in each bio and mark @rq as mixed 630 * merged. 631 */ 632 void blk_rq_set_mixed_merge(struct request *rq) 633 { 634 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; 635 struct bio *bio; 636 637 if (rq->cmd_flags & REQ_MIXED_MERGE) 638 return; 639 640 /* 641 * @rq will no longer represent mixable attributes for all the 642 * contained bios. It will just track those of the first one. 643 * Distributes the attributs to each bio. 644 */ 645 for (bio = rq->bio; bio; bio = bio->bi_next) { 646 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 647 (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 648 bio->bi_opf |= ff; 649 } 650 rq->cmd_flags |= REQ_MIXED_MERGE; 651 } 652 653 static void blk_account_io_merge(struct request *req) 654 { 655 if (blk_do_io_stat(req)) { 656 struct hd_struct *part; 657 int cpu; 658 659 cpu = part_stat_lock(); 660 part = req->part; 661 662 part_round_stats(cpu, part); 663 part_dec_in_flight(part, rq_data_dir(req)); 664 665 hd_struct_put(part); 666 part_stat_unlock(); 667 } 668 } 669 670 /* 671 * Has to be called with the request spinlock acquired 672 */ 673 static int attempt_merge(struct request_queue *q, struct request *req, 674 struct request *next) 675 { 676 if (!rq_mergeable(req) || !rq_mergeable(next)) 677 return 0; 678 679 if (req_op(req) != req_op(next)) 680 return 0; 681 682 /* 683 * not contiguous 684 */ 685 if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)) 686 return 0; 687 688 if (rq_data_dir(req) != rq_data_dir(next) 689 || req->rq_disk != next->rq_disk 690 || req_no_special_merge(next)) 691 return 0; 692 693 if (req_op(req) == REQ_OP_WRITE_SAME && 694 !blk_write_same_mergeable(req->bio, next->bio)) 695 return 0; 696 697 /* 698 * If we are allowed to merge, then append bio list 699 * from next to rq and release next. merge_requests_fn 700 * will have updated segment counts, update sector 701 * counts here. 702 */ 703 if (!ll_merge_requests_fn(q, req, next)) 704 return 0; 705 706 /* 707 * If failfast settings disagree or any of the two is already 708 * a mixed merge, mark both as mixed before proceeding. This 709 * makes sure that all involved bios have mixable attributes 710 * set properly. 711 */ 712 if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE || 713 (req->cmd_flags & REQ_FAILFAST_MASK) != 714 (next->cmd_flags & REQ_FAILFAST_MASK)) { 715 blk_rq_set_mixed_merge(req); 716 blk_rq_set_mixed_merge(next); 717 } 718 719 /* 720 * At this point we have either done a back merge 721 * or front merge. We need the smaller start_time of 722 * the merged requests to be the current request 723 * for accounting purposes. 724 */ 725 if (time_after(req->start_time, next->start_time)) 726 req->start_time = next->start_time; 727 728 req->biotail->bi_next = next->bio; 729 req->biotail = next->biotail; 730 731 req->__data_len += blk_rq_bytes(next); 732 733 elv_merge_requests(q, req, next); 734 735 /* 736 * 'next' is going away, so update stats accordingly 737 */ 738 blk_account_io_merge(next); 739 740 req->ioprio = ioprio_best(req->ioprio, next->ioprio); 741 if (blk_rq_cpu_valid(next)) 742 req->cpu = next->cpu; 743 744 /* owner-ship of bio passed from next to req */ 745 next->bio = NULL; 746 __blk_put_request(q, next); 747 return 1; 748 } 749 750 int attempt_back_merge(struct request_queue *q, struct request *rq) 751 { 752 struct request *next = elv_latter_request(q, rq); 753 754 if (next) 755 return attempt_merge(q, rq, next); 756 757 return 0; 758 } 759 760 int attempt_front_merge(struct request_queue *q, struct request *rq) 761 { 762 struct request *prev = elv_former_request(q, rq); 763 764 if (prev) 765 return attempt_merge(q, prev, rq); 766 767 return 0; 768 } 769 770 int blk_attempt_req_merge(struct request_queue *q, struct request *rq, 771 struct request *next) 772 { 773 struct elevator_queue *e = q->elevator; 774 775 if (e->type->ops.elevator_allow_rq_merge_fn) 776 if (!e->type->ops.elevator_allow_rq_merge_fn(q, rq, next)) 777 return 0; 778 779 return attempt_merge(q, rq, next); 780 } 781 782 bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 783 { 784 if (!rq_mergeable(rq) || !bio_mergeable(bio)) 785 return false; 786 787 if (req_op(rq) != bio_op(bio)) 788 return false; 789 790 /* different data direction or already started, don't merge */ 791 if (bio_data_dir(bio) != rq_data_dir(rq)) 792 return false; 793 794 /* must be same device and not a special request */ 795 if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq)) 796 return false; 797 798 /* only merge integrity protected bio into ditto rq */ 799 if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 800 return false; 801 802 /* must be using the same buffer */ 803 if (req_op(rq) == REQ_OP_WRITE_SAME && 804 !blk_write_same_mergeable(rq->bio, bio)) 805 return false; 806 807 return true; 808 } 809 810 int blk_try_merge(struct request *rq, struct bio *bio) 811 { 812 if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 813 return ELEVATOR_BACK_MERGE; 814 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 815 return ELEVATOR_FRONT_MERGE; 816 return ELEVATOR_NO_MERGE; 817 } 818