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