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 bio_chain(split, *bio); 276 trace_block_split(q, split, (*bio)->bi_iter.bi_sector); 277 generic_make_request(*bio); 278 *bio = split; 279 } 280 } 281 EXPORT_SYMBOL(blk_queue_split); 282 283 static unsigned int __blk_recalc_rq_segments(struct request_queue *q, 284 struct bio *bio, 285 bool no_sg_merge) 286 { 287 struct bio_vec bv, bvprv = { NULL }; 288 int prev = 0; 289 unsigned int seg_size, nr_phys_segs; 290 struct bio *fbio, *bbio; 291 struct bvec_iter iter; 292 293 if (!bio) 294 return 0; 295 296 switch (bio_op(bio)) { 297 case REQ_OP_DISCARD: 298 case REQ_OP_SECURE_ERASE: 299 case REQ_OP_WRITE_ZEROES: 300 return 0; 301 case REQ_OP_WRITE_SAME: 302 return 1; 303 } 304 305 fbio = bio; 306 seg_size = 0; 307 nr_phys_segs = 0; 308 for_each_bio(bio) { 309 bio_for_each_segment(bv, bio, iter) { 310 /* 311 * If SG merging is disabled, each bio vector is 312 * a segment 313 */ 314 if (no_sg_merge) 315 goto new_segment; 316 317 if (prev) { 318 if (seg_size + bv.bv_len 319 > queue_max_segment_size(q)) 320 goto new_segment; 321 if (!biovec_phys_mergeable(q, &bvprv, &bv)) 322 goto new_segment; 323 324 seg_size += bv.bv_len; 325 bvprv = bv; 326 continue; 327 } 328 new_segment: 329 if (nr_phys_segs == 1 && seg_size > 330 fbio->bi_seg_front_size) 331 fbio->bi_seg_front_size = seg_size; 332 333 nr_phys_segs++; 334 bvprv = bv; 335 prev = 1; 336 seg_size = bv.bv_len; 337 } 338 bbio = bio; 339 } 340 341 if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size) 342 fbio->bi_seg_front_size = seg_size; 343 if (seg_size > bbio->bi_seg_back_size) 344 bbio->bi_seg_back_size = seg_size; 345 346 return nr_phys_segs; 347 } 348 349 void blk_recalc_rq_segments(struct request *rq) 350 { 351 bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE, 352 &rq->q->queue_flags); 353 354 rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio, 355 no_sg_merge); 356 } 357 358 void blk_recount_segments(struct request_queue *q, struct bio *bio) 359 { 360 unsigned short seg_cnt; 361 362 /* estimate segment number by bi_vcnt for non-cloned bio */ 363 if (bio_flagged(bio, BIO_CLONED)) 364 seg_cnt = bio_segments(bio); 365 else 366 seg_cnt = bio->bi_vcnt; 367 368 if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) && 369 (seg_cnt < queue_max_segments(q))) 370 bio->bi_phys_segments = seg_cnt; 371 else { 372 struct bio *nxt = bio->bi_next; 373 374 bio->bi_next = NULL; 375 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false); 376 bio->bi_next = nxt; 377 } 378 379 bio_set_flag(bio, BIO_SEG_VALID); 380 } 381 382 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, 383 struct bio *nxt) 384 { 385 struct bio_vec end_bv = { NULL }, nxt_bv; 386 387 if (bio->bi_seg_back_size + nxt->bi_seg_front_size > 388 queue_max_segment_size(q)) 389 return 0; 390 391 if (!bio_has_data(bio)) 392 return 1; 393 394 bio_get_last_bvec(bio, &end_bv); 395 bio_get_first_bvec(nxt, &nxt_bv); 396 397 return biovec_phys_mergeable(q, &end_bv, &nxt_bv); 398 } 399 400 static inline void 401 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, 402 struct scatterlist *sglist, struct bio_vec *bvprv, 403 struct scatterlist **sg, int *nsegs) 404 { 405 406 int nbytes = bvec->bv_len; 407 408 if (*sg) { 409 if ((*sg)->length + nbytes > queue_max_segment_size(q)) 410 goto new_segment; 411 if (!biovec_phys_mergeable(q, bvprv, bvec)) 412 goto new_segment; 413 414 (*sg)->length += nbytes; 415 } else { 416 new_segment: 417 if (!*sg) 418 *sg = sglist; 419 else { 420 /* 421 * If the driver previously mapped a shorter 422 * list, we could see a termination bit 423 * prematurely unless it fully inits the sg 424 * table on each mapping. We KNOW that there 425 * must be more entries here or the driver 426 * would be buggy, so force clear the 427 * termination bit to avoid doing a full 428 * sg_init_table() in drivers for each command. 429 */ 430 sg_unmark_end(*sg); 431 *sg = sg_next(*sg); 432 } 433 434 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); 435 (*nsegs)++; 436 } 437 *bvprv = *bvec; 438 } 439 440 static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv, 441 struct scatterlist *sglist, struct scatterlist **sg) 442 { 443 *sg = sglist; 444 sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); 445 return 1; 446 } 447 448 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 449 struct scatterlist *sglist, 450 struct scatterlist **sg) 451 { 452 struct bio_vec bvec, bvprv = { NULL }; 453 struct bvec_iter iter; 454 int nsegs = 0; 455 456 for_each_bio(bio) 457 bio_for_each_segment(bvec, bio, iter) 458 __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg, 459 &nsegs); 460 461 return nsegs; 462 } 463 464 /* 465 * map a request to scatterlist, return number of sg entries setup. Caller 466 * must make sure sg can hold rq->nr_phys_segments entries 467 */ 468 int blk_rq_map_sg(struct request_queue *q, struct request *rq, 469 struct scatterlist *sglist) 470 { 471 struct scatterlist *sg = NULL; 472 int nsegs = 0; 473 474 if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) 475 nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg); 476 else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME) 477 nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg); 478 else if (rq->bio) 479 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg); 480 481 if (unlikely(rq->rq_flags & RQF_COPY_USER) && 482 (blk_rq_bytes(rq) & q->dma_pad_mask)) { 483 unsigned int pad_len = 484 (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1; 485 486 sg->length += pad_len; 487 rq->extra_len += pad_len; 488 } 489 490 if (q->dma_drain_size && q->dma_drain_needed(rq)) { 491 if (op_is_write(req_op(rq))) 492 memset(q->dma_drain_buffer, 0, q->dma_drain_size); 493 494 sg_unmark_end(sg); 495 sg = sg_next(sg); 496 sg_set_page(sg, virt_to_page(q->dma_drain_buffer), 497 q->dma_drain_size, 498 ((unsigned long)q->dma_drain_buffer) & 499 (PAGE_SIZE - 1)); 500 nsegs++; 501 rq->extra_len += q->dma_drain_size; 502 } 503 504 if (sg) 505 sg_mark_end(sg); 506 507 /* 508 * Something must have been wrong if the figured number of 509 * segment is bigger than number of req's physical segments 510 */ 511 WARN_ON(nsegs > blk_rq_nr_phys_segments(rq)); 512 513 return nsegs; 514 } 515 EXPORT_SYMBOL(blk_rq_map_sg); 516 517 static inline int ll_new_hw_segment(struct request_queue *q, 518 struct request *req, 519 struct bio *bio) 520 { 521 int nr_phys_segs = bio_phys_segments(q, bio); 522 523 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) 524 goto no_merge; 525 526 if (blk_integrity_merge_bio(q, req, bio) == false) 527 goto no_merge; 528 529 /* 530 * This will form the start of a new hw segment. Bump both 531 * counters. 532 */ 533 req->nr_phys_segments += nr_phys_segs; 534 return 1; 535 536 no_merge: 537 req_set_nomerge(q, req); 538 return 0; 539 } 540 541 int ll_back_merge_fn(struct request_queue *q, struct request *req, 542 struct bio *bio) 543 { 544 if (req_gap_back_merge(req, bio)) 545 return 0; 546 if (blk_integrity_rq(req) && 547 integrity_req_gap_back_merge(req, bio)) 548 return 0; 549 if (blk_rq_sectors(req) + bio_sectors(bio) > 550 blk_rq_get_max_sectors(req, blk_rq_pos(req))) { 551 req_set_nomerge(q, req); 552 return 0; 553 } 554 if (!bio_flagged(req->biotail, BIO_SEG_VALID)) 555 blk_recount_segments(q, req->biotail); 556 if (!bio_flagged(bio, BIO_SEG_VALID)) 557 blk_recount_segments(q, bio); 558 559 return ll_new_hw_segment(q, req, bio); 560 } 561 562 int ll_front_merge_fn(struct request_queue *q, struct request *req, 563 struct bio *bio) 564 { 565 566 if (req_gap_front_merge(req, bio)) 567 return 0; 568 if (blk_integrity_rq(req) && 569 integrity_req_gap_front_merge(req, bio)) 570 return 0; 571 if (blk_rq_sectors(req) + bio_sectors(bio) > 572 blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { 573 req_set_nomerge(q, req); 574 return 0; 575 } 576 if (!bio_flagged(bio, BIO_SEG_VALID)) 577 blk_recount_segments(q, bio); 578 if (!bio_flagged(req->bio, BIO_SEG_VALID)) 579 blk_recount_segments(q, req->bio); 580 581 return ll_new_hw_segment(q, req, bio); 582 } 583 584 static bool req_attempt_discard_merge(struct request_queue *q, struct request *req, 585 struct request *next) 586 { 587 unsigned short segments = blk_rq_nr_discard_segments(req); 588 589 if (segments >= queue_max_discard_segments(q)) 590 goto no_merge; 591 if (blk_rq_sectors(req) + bio_sectors(next->bio) > 592 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 593 goto no_merge; 594 595 req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next); 596 return true; 597 no_merge: 598 req_set_nomerge(q, req); 599 return false; 600 } 601 602 static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 603 struct request *next) 604 { 605 int total_phys_segments; 606 unsigned int seg_size = 607 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; 608 609 if (req_gap_back_merge(req, next->bio)) 610 return 0; 611 612 /* 613 * Will it become too large? 614 */ 615 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 616 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 617 return 0; 618 619 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 620 if (blk_phys_contig_segment(q, req->biotail, next->bio)) { 621 if (req->nr_phys_segments == 1) 622 req->bio->bi_seg_front_size = seg_size; 623 if (next->nr_phys_segments == 1) 624 next->biotail->bi_seg_back_size = seg_size; 625 total_phys_segments--; 626 } 627 628 if (total_phys_segments > queue_max_segments(q)) 629 return 0; 630 631 if (blk_integrity_merge_rq(q, req, next) == false) 632 return 0; 633 634 /* Merge is OK... */ 635 req->nr_phys_segments = total_phys_segments; 636 return 1; 637 } 638 639 /** 640 * blk_rq_set_mixed_merge - mark a request as mixed merge 641 * @rq: request to mark as mixed merge 642 * 643 * Description: 644 * @rq is about to be mixed merged. Make sure the attributes 645 * which can be mixed are set in each bio and mark @rq as mixed 646 * merged. 647 */ 648 void blk_rq_set_mixed_merge(struct request *rq) 649 { 650 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; 651 struct bio *bio; 652 653 if (rq->rq_flags & RQF_MIXED_MERGE) 654 return; 655 656 /* 657 * @rq will no longer represent mixable attributes for all the 658 * contained bios. It will just track those of the first one. 659 * Distributes the attributs to each bio. 660 */ 661 for (bio = rq->bio; bio; bio = bio->bi_next) { 662 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 663 (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 664 bio->bi_opf |= ff; 665 } 666 rq->rq_flags |= RQF_MIXED_MERGE; 667 } 668 669 static void blk_account_io_merge(struct request *req) 670 { 671 if (blk_do_io_stat(req)) { 672 struct hd_struct *part; 673 674 part_stat_lock(); 675 part = req->part; 676 677 part_dec_in_flight(req->q, part, rq_data_dir(req)); 678 679 hd_struct_put(part); 680 part_stat_unlock(); 681 } 682 } 683 /* 684 * Two cases of handling DISCARD merge: 685 * If max_discard_segments > 1, the driver takes every bio 686 * as a range and send them to controller together. The ranges 687 * needn't to be contiguous. 688 * Otherwise, the bios/requests will be handled as same as 689 * others which should be contiguous. 690 */ 691 static inline bool blk_discard_mergable(struct request *req) 692 { 693 if (req_op(req) == REQ_OP_DISCARD && 694 queue_max_discard_segments(req->q) > 1) 695 return true; 696 return false; 697 } 698 699 static enum elv_merge blk_try_req_merge(struct request *req, 700 struct request *next) 701 { 702 if (blk_discard_mergable(req)) 703 return ELEVATOR_DISCARD_MERGE; 704 else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) 705 return ELEVATOR_BACK_MERGE; 706 707 return ELEVATOR_NO_MERGE; 708 } 709 710 /* 711 * For non-mq, this has to be called with the request spinlock acquired. 712 * For mq with scheduling, the appropriate queue wide lock should be held. 713 */ 714 static struct request *attempt_merge(struct request_queue *q, 715 struct request *req, struct request *next) 716 { 717 if (!rq_mergeable(req) || !rq_mergeable(next)) 718 return NULL; 719 720 if (req_op(req) != req_op(next)) 721 return NULL; 722 723 if (rq_data_dir(req) != rq_data_dir(next) 724 || req->rq_disk != next->rq_disk) 725 return NULL; 726 727 if (req_op(req) == REQ_OP_WRITE_SAME && 728 !blk_write_same_mergeable(req->bio, next->bio)) 729 return NULL; 730 731 /* 732 * Don't allow merge of different write hints, or for a hint with 733 * non-hint IO. 734 */ 735 if (req->write_hint != next->write_hint) 736 return NULL; 737 738 if (req->ioprio != next->ioprio) 739 return NULL; 740 741 /* 742 * If we are allowed to merge, then append bio list 743 * from next to rq and release next. merge_requests_fn 744 * will have updated segment counts, update sector 745 * counts here. Handle DISCARDs separately, as they 746 * have separate settings. 747 */ 748 749 switch (blk_try_req_merge(req, next)) { 750 case ELEVATOR_DISCARD_MERGE: 751 if (!req_attempt_discard_merge(q, req, next)) 752 return NULL; 753 break; 754 case ELEVATOR_BACK_MERGE: 755 if (!ll_merge_requests_fn(q, req, next)) 756 return NULL; 757 break; 758 default: 759 return NULL; 760 } 761 762 /* 763 * If failfast settings disagree or any of the two is already 764 * a mixed merge, mark both as mixed before proceeding. This 765 * makes sure that all involved bios have mixable attributes 766 * set properly. 767 */ 768 if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || 769 (req->cmd_flags & REQ_FAILFAST_MASK) != 770 (next->cmd_flags & REQ_FAILFAST_MASK)) { 771 blk_rq_set_mixed_merge(req); 772 blk_rq_set_mixed_merge(next); 773 } 774 775 /* 776 * At this point we have either done a back merge or front merge. We 777 * need the smaller start_time_ns of the merged requests to be the 778 * current request for accounting purposes. 779 */ 780 if (next->start_time_ns < req->start_time_ns) 781 req->start_time_ns = next->start_time_ns; 782 783 req->biotail->bi_next = next->bio; 784 req->biotail = next->biotail; 785 786 req->__data_len += blk_rq_bytes(next); 787 788 if (!blk_discard_mergable(req)) 789 elv_merge_requests(q, req, next); 790 791 /* 792 * 'next' is going away, so update stats accordingly 793 */ 794 blk_account_io_merge(next); 795 796 /* 797 * ownership of bio passed from next to req, return 'next' for 798 * the caller to free 799 */ 800 next->bio = NULL; 801 return next; 802 } 803 804 struct request *attempt_back_merge(struct request_queue *q, struct request *rq) 805 { 806 struct request *next = elv_latter_request(q, rq); 807 808 if (next) 809 return attempt_merge(q, rq, next); 810 811 return NULL; 812 } 813 814 struct request *attempt_front_merge(struct request_queue *q, struct request *rq) 815 { 816 struct request *prev = elv_former_request(q, rq); 817 818 if (prev) 819 return attempt_merge(q, prev, rq); 820 821 return NULL; 822 } 823 824 int blk_attempt_req_merge(struct request_queue *q, struct request *rq, 825 struct request *next) 826 { 827 struct request *free; 828 829 free = attempt_merge(q, rq, next); 830 if (free) { 831 blk_put_request(free); 832 return 1; 833 } 834 835 return 0; 836 } 837 838 bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 839 { 840 if (!rq_mergeable(rq) || !bio_mergeable(bio)) 841 return false; 842 843 if (req_op(rq) != bio_op(bio)) 844 return false; 845 846 /* different data direction or already started, don't merge */ 847 if (bio_data_dir(bio) != rq_data_dir(rq)) 848 return false; 849 850 /* must be same device */ 851 if (rq->rq_disk != bio->bi_disk) 852 return false; 853 854 /* only merge integrity protected bio into ditto rq */ 855 if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 856 return false; 857 858 /* must be using the same buffer */ 859 if (req_op(rq) == REQ_OP_WRITE_SAME && 860 !blk_write_same_mergeable(rq->bio, bio)) 861 return false; 862 863 /* 864 * Don't allow merge of different write hints, or for a hint with 865 * non-hint IO. 866 */ 867 if (rq->write_hint != bio->bi_write_hint) 868 return false; 869 870 if (rq->ioprio != bio_prio(bio)) 871 return false; 872 873 return true; 874 } 875 876 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) 877 { 878 if (blk_discard_mergable(rq)) 879 return ELEVATOR_DISCARD_MERGE; 880 else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 881 return ELEVATOR_BACK_MERGE; 882 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 883 return ELEVATOR_FRONT_MERGE; 884 return ELEVATOR_NO_MERGE; 885 } 886