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 /* 16 * Check if the two bvecs from two bios can be merged to one segment. If yes, 17 * no need to check gap between the two bios since the 1st bio and the 1st bvec 18 * in the 2nd bio can be handled in one segment. 19 */ 20 static inline bool bios_segs_mergeable(struct request_queue *q, 21 struct bio *prev, struct bio_vec *prev_last_bv, 22 struct bio_vec *next_first_bv) 23 { 24 if (!biovec_phys_mergeable(q, prev_last_bv, next_first_bv)) 25 return false; 26 if (prev->bi_seg_back_size + next_first_bv->bv_len > 27 queue_max_segment_size(q)) 28 return false; 29 return true; 30 } 31 32 static inline bool bio_will_gap(struct request_queue *q, 33 struct request *prev_rq, struct bio *prev, struct bio *next) 34 { 35 struct bio_vec pb, nb; 36 37 if (!bio_has_data(prev) || !queue_virt_boundary(q)) 38 return false; 39 40 /* 41 * Don't merge if the 1st bio starts with non-zero offset, otherwise it 42 * is quite difficult to respect the sg gap limit. We work hard to 43 * merge a huge number of small single bios in case of mkfs. 44 */ 45 if (prev_rq) 46 bio_get_first_bvec(prev_rq->bio, &pb); 47 else 48 bio_get_first_bvec(prev, &pb); 49 if (pb.bv_offset & queue_virt_boundary(q)) 50 return true; 51 52 /* 53 * We don't need to worry about the situation that the merged segment 54 * ends in unaligned virt boundary: 55 * 56 * - if 'pb' ends aligned, the merged segment ends aligned 57 * - if 'pb' ends unaligned, the next bio must include 58 * one single bvec of 'nb', otherwise the 'nb' can't 59 * merge with 'pb' 60 */ 61 bio_get_last_bvec(prev, &pb); 62 bio_get_first_bvec(next, &nb); 63 if (bios_segs_mergeable(q, prev, &pb, &nb)) 64 return false; 65 return __bvec_gap_to_prev(q, &pb, nb.bv_offset); 66 } 67 68 static inline bool req_gap_back_merge(struct request *req, struct bio *bio) 69 { 70 return bio_will_gap(req->q, req, req->biotail, bio); 71 } 72 73 static inline bool req_gap_front_merge(struct request *req, struct bio *bio) 74 { 75 return bio_will_gap(req->q, NULL, bio, req->bio); 76 } 77 78 static struct bio *blk_bio_discard_split(struct request_queue *q, 79 struct bio *bio, 80 struct bio_set *bs, 81 unsigned *nsegs) 82 { 83 unsigned int max_discard_sectors, granularity; 84 int alignment; 85 sector_t tmp; 86 unsigned split_sectors; 87 88 *nsegs = 1; 89 90 /* Zero-sector (unknown) and one-sector granularities are the same. */ 91 granularity = max(q->limits.discard_granularity >> 9, 1U); 92 93 max_discard_sectors = min(q->limits.max_discard_sectors, 94 bio_allowed_max_sectors(q)); 95 max_discard_sectors -= max_discard_sectors % granularity; 96 97 if (unlikely(!max_discard_sectors)) { 98 /* XXX: warn */ 99 return NULL; 100 } 101 102 if (bio_sectors(bio) <= max_discard_sectors) 103 return NULL; 104 105 split_sectors = max_discard_sectors; 106 107 /* 108 * If the next starting sector would be misaligned, stop the discard at 109 * the previous aligned sector. 110 */ 111 alignment = (q->limits.discard_alignment >> 9) % granularity; 112 113 tmp = bio->bi_iter.bi_sector + split_sectors - alignment; 114 tmp = sector_div(tmp, granularity); 115 116 if (split_sectors > tmp) 117 split_sectors -= tmp; 118 119 return bio_split(bio, split_sectors, GFP_NOIO, bs); 120 } 121 122 static struct bio *blk_bio_write_zeroes_split(struct request_queue *q, 123 struct bio *bio, struct bio_set *bs, unsigned *nsegs) 124 { 125 *nsegs = 1; 126 127 if (!q->limits.max_write_zeroes_sectors) 128 return NULL; 129 130 if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors) 131 return NULL; 132 133 return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs); 134 } 135 136 static struct bio *blk_bio_write_same_split(struct request_queue *q, 137 struct bio *bio, 138 struct bio_set *bs, 139 unsigned *nsegs) 140 { 141 *nsegs = 1; 142 143 if (!q->limits.max_write_same_sectors) 144 return NULL; 145 146 if (bio_sectors(bio) <= q->limits.max_write_same_sectors) 147 return NULL; 148 149 return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs); 150 } 151 152 static inline unsigned get_max_io_size(struct request_queue *q, 153 struct bio *bio) 154 { 155 unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector); 156 unsigned mask = queue_logical_block_size(q) - 1; 157 158 /* aligned to logical block size */ 159 sectors &= ~(mask >> 9); 160 161 return sectors; 162 } 163 164 static struct bio *blk_bio_segment_split(struct request_queue *q, 165 struct bio *bio, 166 struct bio_set *bs, 167 unsigned *segs) 168 { 169 struct bio_vec bv, bvprv, *bvprvp = NULL; 170 struct bvec_iter iter; 171 unsigned seg_size = 0, nsegs = 0, sectors = 0; 172 unsigned front_seg_size = bio->bi_seg_front_size; 173 bool do_split = true; 174 struct bio *new = NULL; 175 const unsigned max_sectors = get_max_io_size(q, bio); 176 177 bio_for_each_segment(bv, bio, iter) { 178 /* 179 * If the queue doesn't support SG gaps and adding this 180 * offset would create a gap, disallow it. 181 */ 182 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset)) 183 goto split; 184 185 if (sectors + (bv.bv_len >> 9) > max_sectors) { 186 /* 187 * Consider this a new segment if we're splitting in 188 * the middle of this vector. 189 */ 190 if (nsegs < queue_max_segments(q) && 191 sectors < max_sectors) { 192 nsegs++; 193 sectors = max_sectors; 194 } 195 goto split; 196 } 197 198 if (bvprvp) { 199 if (seg_size + bv.bv_len > queue_max_segment_size(q)) 200 goto new_segment; 201 if (!biovec_phys_mergeable(q, bvprvp, &bv)) 202 goto new_segment; 203 204 seg_size += bv.bv_len; 205 bvprv = bv; 206 bvprvp = &bvprv; 207 sectors += bv.bv_len >> 9; 208 209 continue; 210 } 211 new_segment: 212 if (nsegs == queue_max_segments(q)) 213 goto split; 214 215 if (nsegs == 1 && seg_size > front_seg_size) 216 front_seg_size = seg_size; 217 218 nsegs++; 219 bvprv = bv; 220 bvprvp = &bvprv; 221 seg_size = bv.bv_len; 222 sectors += bv.bv_len >> 9; 223 224 } 225 226 do_split = false; 227 split: 228 *segs = nsegs; 229 230 if (do_split) { 231 new = bio_split(bio, sectors, GFP_NOIO, bs); 232 if (new) 233 bio = new; 234 } 235 236 if (nsegs == 1 && seg_size > front_seg_size) 237 front_seg_size = seg_size; 238 bio->bi_seg_front_size = front_seg_size; 239 if (seg_size > bio->bi_seg_back_size) 240 bio->bi_seg_back_size = seg_size; 241 242 return do_split ? new : NULL; 243 } 244 245 void blk_queue_split(struct request_queue *q, struct bio **bio) 246 { 247 struct bio *split, *res; 248 unsigned nsegs; 249 250 switch (bio_op(*bio)) { 251 case REQ_OP_DISCARD: 252 case REQ_OP_SECURE_ERASE: 253 split = blk_bio_discard_split(q, *bio, &q->bio_split, &nsegs); 254 break; 255 case REQ_OP_WRITE_ZEROES: 256 split = blk_bio_write_zeroes_split(q, *bio, &q->bio_split, &nsegs); 257 break; 258 case REQ_OP_WRITE_SAME: 259 split = blk_bio_write_same_split(q, *bio, &q->bio_split, &nsegs); 260 break; 261 default: 262 split = blk_bio_segment_split(q, *bio, &q->bio_split, &nsegs); 263 break; 264 } 265 266 /* physical segments can be figured out during splitting */ 267 res = split ? split : *bio; 268 res->bi_phys_segments = nsegs; 269 bio_set_flag(res, BIO_SEG_VALID); 270 271 if (split) { 272 /* there isn't chance to merge the splitted bio */ 273 split->bi_opf |= REQ_NOMERGE; 274 275 /* 276 * Since we're recursing into make_request here, ensure 277 * that we mark this bio as already having entered the queue. 278 * If not, and the queue is going away, we can get stuck 279 * forever on waiting for the queue reference to drop. But 280 * that will never happen, as we're already holding a 281 * reference to it. 282 */ 283 bio_set_flag(*bio, BIO_QUEUE_ENTERED); 284 285 bio_chain(split, *bio); 286 trace_block_split(q, split, (*bio)->bi_iter.bi_sector); 287 generic_make_request(*bio); 288 *bio = split; 289 } 290 } 291 EXPORT_SYMBOL(blk_queue_split); 292 293 static unsigned int __blk_recalc_rq_segments(struct request_queue *q, 294 struct bio *bio, 295 bool no_sg_merge) 296 { 297 struct bio_vec bv, bvprv = { NULL }; 298 int prev = 0; 299 unsigned int seg_size, nr_phys_segs; 300 struct bio *fbio, *bbio; 301 struct bvec_iter iter; 302 303 if (!bio) 304 return 0; 305 306 switch (bio_op(bio)) { 307 case REQ_OP_DISCARD: 308 case REQ_OP_SECURE_ERASE: 309 case REQ_OP_WRITE_ZEROES: 310 return 0; 311 case REQ_OP_WRITE_SAME: 312 return 1; 313 } 314 315 fbio = bio; 316 seg_size = 0; 317 nr_phys_segs = 0; 318 for_each_bio(bio) { 319 bio_for_each_segment(bv, bio, iter) { 320 /* 321 * If SG merging is disabled, each bio vector is 322 * a segment 323 */ 324 if (no_sg_merge) 325 goto new_segment; 326 327 if (prev) { 328 if (seg_size + bv.bv_len 329 > queue_max_segment_size(q)) 330 goto new_segment; 331 if (!biovec_phys_mergeable(q, &bvprv, &bv)) 332 goto new_segment; 333 334 seg_size += bv.bv_len; 335 bvprv = bv; 336 continue; 337 } 338 new_segment: 339 if (nr_phys_segs == 1 && seg_size > 340 fbio->bi_seg_front_size) 341 fbio->bi_seg_front_size = seg_size; 342 343 nr_phys_segs++; 344 bvprv = bv; 345 prev = 1; 346 seg_size = bv.bv_len; 347 } 348 bbio = bio; 349 } 350 351 if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size) 352 fbio->bi_seg_front_size = seg_size; 353 if (seg_size > bbio->bi_seg_back_size) 354 bbio->bi_seg_back_size = seg_size; 355 356 return nr_phys_segs; 357 } 358 359 void blk_recalc_rq_segments(struct request *rq) 360 { 361 bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE, 362 &rq->q->queue_flags); 363 364 rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio, 365 no_sg_merge); 366 } 367 368 void blk_recount_segments(struct request_queue *q, struct bio *bio) 369 { 370 unsigned short seg_cnt = bio_segments(bio); 371 372 if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) && 373 (seg_cnt < queue_max_segments(q))) 374 bio->bi_phys_segments = seg_cnt; 375 else { 376 struct bio *nxt = bio->bi_next; 377 378 bio->bi_next = NULL; 379 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false); 380 bio->bi_next = nxt; 381 } 382 383 bio_set_flag(bio, BIO_SEG_VALID); 384 } 385 386 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, 387 struct bio *nxt) 388 { 389 struct bio_vec end_bv = { NULL }, nxt_bv; 390 391 if (bio->bi_seg_back_size + nxt->bi_seg_front_size > 392 queue_max_segment_size(q)) 393 return 0; 394 395 if (!bio_has_data(bio)) 396 return 1; 397 398 bio_get_last_bvec(bio, &end_bv); 399 bio_get_first_bvec(nxt, &nxt_bv); 400 401 return biovec_phys_mergeable(q, &end_bv, &nxt_bv); 402 } 403 404 static inline void 405 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, 406 struct scatterlist *sglist, struct bio_vec *bvprv, 407 struct scatterlist **sg, int *nsegs) 408 { 409 410 int nbytes = bvec->bv_len; 411 412 if (*sg) { 413 if ((*sg)->length + nbytes > queue_max_segment_size(q)) 414 goto new_segment; 415 if (!biovec_phys_mergeable(q, bvprv, bvec)) 416 goto new_segment; 417 418 (*sg)->length += nbytes; 419 } else { 420 new_segment: 421 if (!*sg) 422 *sg = sglist; 423 else { 424 /* 425 * If the driver previously mapped a shorter 426 * list, we could see a termination bit 427 * prematurely unless it fully inits the sg 428 * table on each mapping. We KNOW that there 429 * must be more entries here or the driver 430 * would be buggy, so force clear the 431 * termination bit to avoid doing a full 432 * sg_init_table() in drivers for each command. 433 */ 434 sg_unmark_end(*sg); 435 *sg = sg_next(*sg); 436 } 437 438 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); 439 (*nsegs)++; 440 } 441 *bvprv = *bvec; 442 } 443 444 static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv, 445 struct scatterlist *sglist, struct scatterlist **sg) 446 { 447 *sg = sglist; 448 sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); 449 return 1; 450 } 451 452 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 453 struct scatterlist *sglist, 454 struct scatterlist **sg) 455 { 456 struct bio_vec bvec, bvprv = { NULL }; 457 struct bvec_iter iter; 458 int nsegs = 0; 459 460 for_each_bio(bio) 461 bio_for_each_segment(bvec, bio, iter) 462 __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg, 463 &nsegs); 464 465 return nsegs; 466 } 467 468 /* 469 * map a request to scatterlist, return number of sg entries setup. Caller 470 * must make sure sg can hold rq->nr_phys_segments entries 471 */ 472 int blk_rq_map_sg(struct request_queue *q, struct request *rq, 473 struct scatterlist *sglist) 474 { 475 struct scatterlist *sg = NULL; 476 int nsegs = 0; 477 478 if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) 479 nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg); 480 else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME) 481 nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg); 482 else if (rq->bio) 483 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg); 484 485 if (unlikely(rq->rq_flags & RQF_COPY_USER) && 486 (blk_rq_bytes(rq) & q->dma_pad_mask)) { 487 unsigned int pad_len = 488 (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1; 489 490 sg->length += pad_len; 491 rq->extra_len += pad_len; 492 } 493 494 if (q->dma_drain_size && q->dma_drain_needed(rq)) { 495 if (op_is_write(req_op(rq))) 496 memset(q->dma_drain_buffer, 0, q->dma_drain_size); 497 498 sg_unmark_end(sg); 499 sg = sg_next(sg); 500 sg_set_page(sg, virt_to_page(q->dma_drain_buffer), 501 q->dma_drain_size, 502 ((unsigned long)q->dma_drain_buffer) & 503 (PAGE_SIZE - 1)); 504 nsegs++; 505 rq->extra_len += q->dma_drain_size; 506 } 507 508 if (sg) 509 sg_mark_end(sg); 510 511 /* 512 * Something must have been wrong if the figured number of 513 * segment is bigger than number of req's physical segments 514 */ 515 WARN_ON(nsegs > blk_rq_nr_phys_segments(rq)); 516 517 return nsegs; 518 } 519 EXPORT_SYMBOL(blk_rq_map_sg); 520 521 static inline int ll_new_hw_segment(struct request_queue *q, 522 struct request *req, 523 struct bio *bio) 524 { 525 int nr_phys_segs = bio_phys_segments(q, bio); 526 527 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) 528 goto no_merge; 529 530 if (blk_integrity_merge_bio(q, req, bio) == false) 531 goto no_merge; 532 533 /* 534 * This will form the start of a new hw segment. Bump both 535 * counters. 536 */ 537 req->nr_phys_segments += nr_phys_segs; 538 return 1; 539 540 no_merge: 541 req_set_nomerge(q, req); 542 return 0; 543 } 544 545 int ll_back_merge_fn(struct request_queue *q, struct request *req, 546 struct bio *bio) 547 { 548 if (req_gap_back_merge(req, bio)) 549 return 0; 550 if (blk_integrity_rq(req) && 551 integrity_req_gap_back_merge(req, bio)) 552 return 0; 553 if (blk_rq_sectors(req) + bio_sectors(bio) > 554 blk_rq_get_max_sectors(req, blk_rq_pos(req))) { 555 req_set_nomerge(q, req); 556 return 0; 557 } 558 if (!bio_flagged(req->biotail, BIO_SEG_VALID)) 559 blk_recount_segments(q, req->biotail); 560 if (!bio_flagged(bio, BIO_SEG_VALID)) 561 blk_recount_segments(q, bio); 562 563 return ll_new_hw_segment(q, req, bio); 564 } 565 566 int ll_front_merge_fn(struct request_queue *q, struct request *req, 567 struct bio *bio) 568 { 569 570 if (req_gap_front_merge(req, bio)) 571 return 0; 572 if (blk_integrity_rq(req) && 573 integrity_req_gap_front_merge(req, bio)) 574 return 0; 575 if (blk_rq_sectors(req) + bio_sectors(bio) > 576 blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { 577 req_set_nomerge(q, req); 578 return 0; 579 } 580 if (!bio_flagged(bio, BIO_SEG_VALID)) 581 blk_recount_segments(q, bio); 582 if (!bio_flagged(req->bio, BIO_SEG_VALID)) 583 blk_recount_segments(q, req->bio); 584 585 return ll_new_hw_segment(q, req, bio); 586 } 587 588 static bool req_attempt_discard_merge(struct request_queue *q, struct request *req, 589 struct request *next) 590 { 591 unsigned short segments = blk_rq_nr_discard_segments(req); 592 593 if (segments >= queue_max_discard_segments(q)) 594 goto no_merge; 595 if (blk_rq_sectors(req) + bio_sectors(next->bio) > 596 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 597 goto no_merge; 598 599 req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next); 600 return true; 601 no_merge: 602 req_set_nomerge(q, req); 603 return false; 604 } 605 606 static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 607 struct request *next) 608 { 609 int total_phys_segments; 610 unsigned int seg_size = 611 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; 612 613 if (req_gap_back_merge(req, next->bio)) 614 return 0; 615 616 /* 617 * Will it become too large? 618 */ 619 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 620 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 621 return 0; 622 623 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 624 if (blk_phys_contig_segment(q, req->biotail, next->bio)) { 625 if (req->nr_phys_segments == 1) 626 req->bio->bi_seg_front_size = seg_size; 627 if (next->nr_phys_segments == 1) 628 next->biotail->bi_seg_back_size = seg_size; 629 total_phys_segments--; 630 } 631 632 if (total_phys_segments > queue_max_segments(q)) 633 return 0; 634 635 if (blk_integrity_merge_rq(q, req, next) == false) 636 return 0; 637 638 /* Merge is OK... */ 639 req->nr_phys_segments = total_phys_segments; 640 return 1; 641 } 642 643 /** 644 * blk_rq_set_mixed_merge - mark a request as mixed merge 645 * @rq: request to mark as mixed merge 646 * 647 * Description: 648 * @rq is about to be mixed merged. Make sure the attributes 649 * which can be mixed are set in each bio and mark @rq as mixed 650 * merged. 651 */ 652 void blk_rq_set_mixed_merge(struct request *rq) 653 { 654 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; 655 struct bio *bio; 656 657 if (rq->rq_flags & RQF_MIXED_MERGE) 658 return; 659 660 /* 661 * @rq will no longer represent mixable attributes for all the 662 * contained bios. It will just track those of the first one. 663 * Distributes the attributs to each bio. 664 */ 665 for (bio = rq->bio; bio; bio = bio->bi_next) { 666 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 667 (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 668 bio->bi_opf |= ff; 669 } 670 rq->rq_flags |= RQF_MIXED_MERGE; 671 } 672 673 static void blk_account_io_merge(struct request *req) 674 { 675 if (blk_do_io_stat(req)) { 676 struct hd_struct *part; 677 678 part_stat_lock(); 679 part = req->part; 680 681 part_dec_in_flight(req->q, part, rq_data_dir(req)); 682 683 hd_struct_put(part); 684 part_stat_unlock(); 685 } 686 } 687 /* 688 * Two cases of handling DISCARD merge: 689 * If max_discard_segments > 1, the driver takes every bio 690 * as a range and send them to controller together. The ranges 691 * needn't to be contiguous. 692 * Otherwise, the bios/requests will be handled as same as 693 * others which should be contiguous. 694 */ 695 static inline bool blk_discard_mergable(struct request *req) 696 { 697 if (req_op(req) == REQ_OP_DISCARD && 698 queue_max_discard_segments(req->q) > 1) 699 return true; 700 return false; 701 } 702 703 static enum elv_merge blk_try_req_merge(struct request *req, 704 struct request *next) 705 { 706 if (blk_discard_mergable(req)) 707 return ELEVATOR_DISCARD_MERGE; 708 else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) 709 return ELEVATOR_BACK_MERGE; 710 711 return ELEVATOR_NO_MERGE; 712 } 713 714 /* 715 * For non-mq, this has to be called with the request spinlock acquired. 716 * For mq with scheduling, the appropriate queue wide lock should be held. 717 */ 718 static struct request *attempt_merge(struct request_queue *q, 719 struct request *req, struct request *next) 720 { 721 if (!rq_mergeable(req) || !rq_mergeable(next)) 722 return NULL; 723 724 if (req_op(req) != req_op(next)) 725 return NULL; 726 727 if (rq_data_dir(req) != rq_data_dir(next) 728 || req->rq_disk != next->rq_disk) 729 return NULL; 730 731 if (req_op(req) == REQ_OP_WRITE_SAME && 732 !blk_write_same_mergeable(req->bio, next->bio)) 733 return NULL; 734 735 /* 736 * Don't allow merge of different write hints, or for a hint with 737 * non-hint IO. 738 */ 739 if (req->write_hint != next->write_hint) 740 return NULL; 741 742 if (req->ioprio != next->ioprio) 743 return NULL; 744 745 /* 746 * If we are allowed to merge, then append bio list 747 * from next to rq and release next. merge_requests_fn 748 * will have updated segment counts, update sector 749 * counts here. Handle DISCARDs separately, as they 750 * have separate settings. 751 */ 752 753 switch (blk_try_req_merge(req, next)) { 754 case ELEVATOR_DISCARD_MERGE: 755 if (!req_attempt_discard_merge(q, req, next)) 756 return NULL; 757 break; 758 case ELEVATOR_BACK_MERGE: 759 if (!ll_merge_requests_fn(q, req, next)) 760 return NULL; 761 break; 762 default: 763 return NULL; 764 } 765 766 /* 767 * If failfast settings disagree or any of the two is already 768 * a mixed merge, mark both as mixed before proceeding. This 769 * makes sure that all involved bios have mixable attributes 770 * set properly. 771 */ 772 if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || 773 (req->cmd_flags & REQ_FAILFAST_MASK) != 774 (next->cmd_flags & REQ_FAILFAST_MASK)) { 775 blk_rq_set_mixed_merge(req); 776 blk_rq_set_mixed_merge(next); 777 } 778 779 /* 780 * At this point we have either done a back merge or front merge. We 781 * need the smaller start_time_ns of the merged requests to be the 782 * current request for accounting purposes. 783 */ 784 if (next->start_time_ns < req->start_time_ns) 785 req->start_time_ns = next->start_time_ns; 786 787 req->biotail->bi_next = next->bio; 788 req->biotail = next->biotail; 789 790 req->__data_len += blk_rq_bytes(next); 791 792 if (!blk_discard_mergable(req)) 793 elv_merge_requests(q, req, next); 794 795 /* 796 * 'next' is going away, so update stats accordingly 797 */ 798 blk_account_io_merge(next); 799 800 /* 801 * ownership of bio passed from next to req, return 'next' for 802 * the caller to free 803 */ 804 next->bio = NULL; 805 return next; 806 } 807 808 struct request *attempt_back_merge(struct request_queue *q, struct request *rq) 809 { 810 struct request *next = elv_latter_request(q, rq); 811 812 if (next) 813 return attempt_merge(q, rq, next); 814 815 return NULL; 816 } 817 818 struct request *attempt_front_merge(struct request_queue *q, struct request *rq) 819 { 820 struct request *prev = elv_former_request(q, rq); 821 822 if (prev) 823 return attempt_merge(q, prev, rq); 824 825 return NULL; 826 } 827 828 int blk_attempt_req_merge(struct request_queue *q, struct request *rq, 829 struct request *next) 830 { 831 struct request *free; 832 833 free = attempt_merge(q, rq, next); 834 if (free) { 835 blk_put_request(free); 836 return 1; 837 } 838 839 return 0; 840 } 841 842 bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 843 { 844 if (!rq_mergeable(rq) || !bio_mergeable(bio)) 845 return false; 846 847 if (req_op(rq) != bio_op(bio)) 848 return false; 849 850 /* different data direction or already started, don't merge */ 851 if (bio_data_dir(bio) != rq_data_dir(rq)) 852 return false; 853 854 /* must be same device */ 855 if (rq->rq_disk != bio->bi_disk) 856 return false; 857 858 /* only merge integrity protected bio into ditto rq */ 859 if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 860 return false; 861 862 /* must be using the same buffer */ 863 if (req_op(rq) == REQ_OP_WRITE_SAME && 864 !blk_write_same_mergeable(rq->bio, bio)) 865 return false; 866 867 /* 868 * Don't allow merge of different write hints, or for a hint with 869 * non-hint IO. 870 */ 871 if (rq->write_hint != bio->bi_write_hint) 872 return false; 873 874 if (rq->ioprio != bio_prio(bio)) 875 return false; 876 877 return true; 878 } 879 880 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) 881 { 882 if (blk_discard_mergable(rq)) 883 return ELEVATOR_DISCARD_MERGE; 884 else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 885 return ELEVATOR_BACK_MERGE; 886 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 887 return ELEVATOR_FRONT_MERGE; 888 return ELEVATOR_NO_MERGE; 889 } 890