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 void req_set_nomerge(struct request_queue *q, struct request *req) 486 { 487 req->cmd_flags |= REQ_NOMERGE; 488 if (req == q->last_merge) 489 q->last_merge = NULL; 490 } 491 492 static inline int ll_new_hw_segment(struct request_queue *q, 493 struct request *req, 494 struct bio *bio) 495 { 496 int nr_phys_segs = bio_phys_segments(q, bio); 497 498 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) 499 goto no_merge; 500 501 if (blk_integrity_merge_bio(q, req, bio) == false) 502 goto no_merge; 503 504 /* 505 * This will form the start of a new hw segment. Bump both 506 * counters. 507 */ 508 req->nr_phys_segments += nr_phys_segs; 509 return 1; 510 511 no_merge: 512 req_set_nomerge(q, req); 513 return 0; 514 } 515 516 int ll_back_merge_fn(struct request_queue *q, struct request *req, 517 struct bio *bio) 518 { 519 if (req_gap_back_merge(req, bio)) 520 return 0; 521 if (blk_integrity_rq(req) && 522 integrity_req_gap_back_merge(req, bio)) 523 return 0; 524 if (blk_rq_sectors(req) + bio_sectors(bio) > 525 blk_rq_get_max_sectors(req, blk_rq_pos(req))) { 526 req_set_nomerge(q, req); 527 return 0; 528 } 529 if (!bio_flagged(req->biotail, BIO_SEG_VALID)) 530 blk_recount_segments(q, req->biotail); 531 if (!bio_flagged(bio, BIO_SEG_VALID)) 532 blk_recount_segments(q, bio); 533 534 return ll_new_hw_segment(q, req, bio); 535 } 536 537 int ll_front_merge_fn(struct request_queue *q, struct request *req, 538 struct bio *bio) 539 { 540 541 if (req_gap_front_merge(req, bio)) 542 return 0; 543 if (blk_integrity_rq(req) && 544 integrity_req_gap_front_merge(req, bio)) 545 return 0; 546 if (blk_rq_sectors(req) + bio_sectors(bio) > 547 blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { 548 req_set_nomerge(q, req); 549 return 0; 550 } 551 if (!bio_flagged(bio, BIO_SEG_VALID)) 552 blk_recount_segments(q, bio); 553 if (!bio_flagged(req->bio, BIO_SEG_VALID)) 554 blk_recount_segments(q, req->bio); 555 556 return ll_new_hw_segment(q, req, bio); 557 } 558 559 /* 560 * blk-mq uses req->special to carry normal driver per-request payload, it 561 * does not indicate a prepared command that we cannot merge with. 562 */ 563 static bool req_no_special_merge(struct request *req) 564 { 565 struct request_queue *q = req->q; 566 567 return !q->mq_ops && req->special; 568 } 569 570 static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 571 struct request *next) 572 { 573 int total_phys_segments; 574 unsigned int seg_size = 575 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; 576 577 /* 578 * First check if the either of the requests are re-queued 579 * requests. Can't merge them if they are. 580 */ 581 if (req_no_special_merge(req) || req_no_special_merge(next)) 582 return 0; 583 584 if (req_gap_back_merge(req, next->bio)) 585 return 0; 586 587 /* 588 * Will it become too large? 589 */ 590 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 591 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 592 return 0; 593 594 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 595 if (blk_phys_contig_segment(q, req->biotail, next->bio)) { 596 if (req->nr_phys_segments == 1) 597 req->bio->bi_seg_front_size = seg_size; 598 if (next->nr_phys_segments == 1) 599 next->biotail->bi_seg_back_size = seg_size; 600 total_phys_segments--; 601 } 602 603 if (total_phys_segments > queue_max_segments(q)) 604 return 0; 605 606 if (blk_integrity_merge_rq(q, req, next) == false) 607 return 0; 608 609 /* Merge is OK... */ 610 req->nr_phys_segments = total_phys_segments; 611 return 1; 612 } 613 614 /** 615 * blk_rq_set_mixed_merge - mark a request as mixed merge 616 * @rq: request to mark as mixed merge 617 * 618 * Description: 619 * @rq is about to be mixed merged. Make sure the attributes 620 * which can be mixed are set in each bio and mark @rq as mixed 621 * merged. 622 */ 623 void blk_rq_set_mixed_merge(struct request *rq) 624 { 625 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; 626 struct bio *bio; 627 628 if (rq->rq_flags & RQF_MIXED_MERGE) 629 return; 630 631 /* 632 * @rq will no longer represent mixable attributes for all the 633 * contained bios. It will just track those of the first one. 634 * Distributes the attributs to each bio. 635 */ 636 for (bio = rq->bio; bio; bio = bio->bi_next) { 637 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 638 (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 639 bio->bi_opf |= ff; 640 } 641 rq->rq_flags |= RQF_MIXED_MERGE; 642 } 643 644 static void blk_account_io_merge(struct request *req) 645 { 646 if (blk_do_io_stat(req)) { 647 struct hd_struct *part; 648 int cpu; 649 650 cpu = part_stat_lock(); 651 part = req->part; 652 653 part_round_stats(cpu, part); 654 part_dec_in_flight(part, rq_data_dir(req)); 655 656 hd_struct_put(part); 657 part_stat_unlock(); 658 } 659 } 660 661 /* 662 * Has to be called with the request spinlock acquired 663 */ 664 static int attempt_merge(struct request_queue *q, struct request *req, 665 struct request *next) 666 { 667 if (!rq_mergeable(req) || !rq_mergeable(next)) 668 return 0; 669 670 if (req_op(req) != req_op(next)) 671 return 0; 672 673 /* 674 * not contiguous 675 */ 676 if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)) 677 return 0; 678 679 if (rq_data_dir(req) != rq_data_dir(next) 680 || req->rq_disk != next->rq_disk 681 || req_no_special_merge(next)) 682 return 0; 683 684 if (req_op(req) == REQ_OP_WRITE_SAME && 685 !blk_write_same_mergeable(req->bio, next->bio)) 686 return 0; 687 688 /* 689 * If we are allowed to merge, then append bio list 690 * from next to rq and release next. merge_requests_fn 691 * will have updated segment counts, update sector 692 * counts here. 693 */ 694 if (!ll_merge_requests_fn(q, req, next)) 695 return 0; 696 697 /* 698 * If failfast settings disagree or any of the two is already 699 * a mixed merge, mark both as mixed before proceeding. This 700 * makes sure that all involved bios have mixable attributes 701 * set properly. 702 */ 703 if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || 704 (req->cmd_flags & REQ_FAILFAST_MASK) != 705 (next->cmd_flags & REQ_FAILFAST_MASK)) { 706 blk_rq_set_mixed_merge(req); 707 blk_rq_set_mixed_merge(next); 708 } 709 710 /* 711 * At this point we have either done a back merge 712 * or front merge. We need the smaller start_time of 713 * the merged requests to be the current request 714 * for accounting purposes. 715 */ 716 if (time_after(req->start_time, next->start_time)) 717 req->start_time = next->start_time; 718 719 req->biotail->bi_next = next->bio; 720 req->biotail = next->biotail; 721 722 req->__data_len += blk_rq_bytes(next); 723 724 elv_merge_requests(q, req, next); 725 726 /* 727 * 'next' is going away, so update stats accordingly 728 */ 729 blk_account_io_merge(next); 730 731 req->ioprio = ioprio_best(req->ioprio, next->ioprio); 732 if (blk_rq_cpu_valid(next)) 733 req->cpu = next->cpu; 734 735 /* owner-ship of bio passed from next to req */ 736 next->bio = NULL; 737 __blk_put_request(q, next); 738 return 1; 739 } 740 741 int attempt_back_merge(struct request_queue *q, struct request *rq) 742 { 743 struct request *next = elv_latter_request(q, rq); 744 745 if (next) 746 return attempt_merge(q, rq, next); 747 748 return 0; 749 } 750 751 int attempt_front_merge(struct request_queue *q, struct request *rq) 752 { 753 struct request *prev = elv_former_request(q, rq); 754 755 if (prev) 756 return attempt_merge(q, prev, rq); 757 758 return 0; 759 } 760 761 int blk_attempt_req_merge(struct request_queue *q, struct request *rq, 762 struct request *next) 763 { 764 struct elevator_queue *e = q->elevator; 765 766 if (e->type->ops.elevator_allow_rq_merge_fn) 767 if (!e->type->ops.elevator_allow_rq_merge_fn(q, rq, next)) 768 return 0; 769 770 return attempt_merge(q, rq, next); 771 } 772 773 bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 774 { 775 if (!rq_mergeable(rq) || !bio_mergeable(bio)) 776 return false; 777 778 if (req_op(rq) != bio_op(bio)) 779 return false; 780 781 /* different data direction or already started, don't merge */ 782 if (bio_data_dir(bio) != rq_data_dir(rq)) 783 return false; 784 785 /* must be same device and not a special request */ 786 if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq)) 787 return false; 788 789 /* only merge integrity protected bio into ditto rq */ 790 if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 791 return false; 792 793 /* must be using the same buffer */ 794 if (req_op(rq) == REQ_OP_WRITE_SAME && 795 !blk_write_same_mergeable(rq->bio, bio)) 796 return false; 797 798 return true; 799 } 800 801 int blk_try_merge(struct request *rq, struct bio *bio) 802 { 803 if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 804 return ELEVATOR_BACK_MERGE; 805 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 806 return ELEVATOR_FRONT_MERGE; 807 return ELEVATOR_NO_MERGE; 808 } 809