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 unsigned get_max_segment_size(struct request_queue *q, 165 unsigned offset) 166 { 167 unsigned long mask = queue_segment_boundary(q); 168 169 /* default segment boundary mask means no boundary limit */ 170 if (mask == BLK_SEG_BOUNDARY_MASK) 171 return queue_max_segment_size(q); 172 173 return min_t(unsigned long, mask - (mask & offset) + 1, 174 queue_max_segment_size(q)); 175 } 176 177 /* 178 * Split the bvec @bv into segments, and update all kinds of 179 * variables. 180 */ 181 static bool bvec_split_segs(struct request_queue *q, struct bio_vec *bv, 182 unsigned *nsegs, unsigned *last_seg_size, 183 unsigned *front_seg_size, unsigned *sectors, unsigned max_segs) 184 { 185 unsigned len = bv->bv_len; 186 unsigned total_len = 0; 187 unsigned new_nsegs = 0, seg_size = 0; 188 189 /* 190 * Multi-page bvec may be too big to hold in one segment, so the 191 * current bvec has to be splitted as multiple segments. 192 */ 193 while (len && new_nsegs + *nsegs < max_segs) { 194 seg_size = get_max_segment_size(q, bv->bv_offset + total_len); 195 seg_size = min(seg_size, len); 196 197 new_nsegs++; 198 total_len += seg_size; 199 len -= seg_size; 200 201 if ((bv->bv_offset + total_len) & queue_virt_boundary(q)) 202 break; 203 } 204 205 if (!new_nsegs) 206 return !!len; 207 208 /* update front segment size */ 209 if (!*nsegs) { 210 unsigned first_seg_size; 211 212 if (new_nsegs == 1) 213 first_seg_size = get_max_segment_size(q, bv->bv_offset); 214 else 215 first_seg_size = queue_max_segment_size(q); 216 217 if (*front_seg_size < first_seg_size) 218 *front_seg_size = first_seg_size; 219 } 220 221 /* update other varibles */ 222 *last_seg_size = seg_size; 223 *nsegs += new_nsegs; 224 if (sectors) 225 *sectors += total_len >> 9; 226 227 /* split in the middle of the bvec if len != 0 */ 228 return !!len; 229 } 230 231 static struct bio *blk_bio_segment_split(struct request_queue *q, 232 struct bio *bio, 233 struct bio_set *bs, 234 unsigned *segs) 235 { 236 struct bio_vec bv, bvprv, *bvprvp = NULL; 237 struct bvec_iter iter; 238 unsigned seg_size = 0, nsegs = 0, sectors = 0; 239 unsigned front_seg_size = bio->bi_seg_front_size; 240 bool do_split = true; 241 struct bio *new = NULL; 242 const unsigned max_sectors = get_max_io_size(q, bio); 243 const unsigned max_segs = queue_max_segments(q); 244 245 bio_for_each_bvec(bv, bio, iter) { 246 /* 247 * If the queue doesn't support SG gaps and adding this 248 * offset would create a gap, disallow it. 249 */ 250 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset)) 251 goto split; 252 253 if (sectors + (bv.bv_len >> 9) > max_sectors) { 254 /* 255 * Consider this a new segment if we're splitting in 256 * the middle of this vector. 257 */ 258 if (nsegs < max_segs && 259 sectors < max_sectors) { 260 /* split in the middle of bvec */ 261 bv.bv_len = (max_sectors - sectors) << 9; 262 bvec_split_segs(q, &bv, &nsegs, 263 &seg_size, 264 &front_seg_size, 265 §ors, max_segs); 266 } 267 goto split; 268 } 269 270 if (nsegs == max_segs) 271 goto split; 272 273 bvprv = bv; 274 bvprvp = &bvprv; 275 276 if (bv.bv_offset + bv.bv_len <= PAGE_SIZE) { 277 nsegs++; 278 seg_size = bv.bv_len; 279 sectors += bv.bv_len >> 9; 280 if (nsegs == 1 && seg_size > front_seg_size) 281 front_seg_size = seg_size; 282 } else if (bvec_split_segs(q, &bv, &nsegs, &seg_size, 283 &front_seg_size, §ors, max_segs)) { 284 goto split; 285 } 286 } 287 288 do_split = false; 289 split: 290 *segs = nsegs; 291 292 if (do_split) { 293 new = bio_split(bio, sectors, GFP_NOIO, bs); 294 if (new) 295 bio = new; 296 } 297 298 bio->bi_seg_front_size = front_seg_size; 299 if (seg_size > bio->bi_seg_back_size) 300 bio->bi_seg_back_size = seg_size; 301 302 return do_split ? new : NULL; 303 } 304 305 void blk_queue_split(struct request_queue *q, struct bio **bio) 306 { 307 struct bio *split, *res; 308 unsigned nsegs; 309 310 switch (bio_op(*bio)) { 311 case REQ_OP_DISCARD: 312 case REQ_OP_SECURE_ERASE: 313 split = blk_bio_discard_split(q, *bio, &q->bio_split, &nsegs); 314 break; 315 case REQ_OP_WRITE_ZEROES: 316 split = blk_bio_write_zeroes_split(q, *bio, &q->bio_split, &nsegs); 317 break; 318 case REQ_OP_WRITE_SAME: 319 split = blk_bio_write_same_split(q, *bio, &q->bio_split, &nsegs); 320 break; 321 default: 322 split = blk_bio_segment_split(q, *bio, &q->bio_split, &nsegs); 323 break; 324 } 325 326 /* physical segments can be figured out during splitting */ 327 res = split ? split : *bio; 328 res->bi_phys_segments = nsegs; 329 bio_set_flag(res, BIO_SEG_VALID); 330 331 if (split) { 332 /* there isn't chance to merge the splitted bio */ 333 split->bi_opf |= REQ_NOMERGE; 334 335 /* 336 * Since we're recursing into make_request here, ensure 337 * that we mark this bio as already having entered the queue. 338 * If not, and the queue is going away, we can get stuck 339 * forever on waiting for the queue reference to drop. But 340 * that will never happen, as we're already holding a 341 * reference to it. 342 */ 343 bio_set_flag(*bio, BIO_QUEUE_ENTERED); 344 345 bio_chain(split, *bio); 346 trace_block_split(q, split, (*bio)->bi_iter.bi_sector); 347 generic_make_request(*bio); 348 *bio = split; 349 } 350 } 351 EXPORT_SYMBOL(blk_queue_split); 352 353 static unsigned int __blk_recalc_rq_segments(struct request_queue *q, 354 struct bio *bio) 355 { 356 struct bio_vec bv, bvprv = { NULL }; 357 int prev = 0; 358 unsigned int seg_size, nr_phys_segs; 359 unsigned front_seg_size; 360 struct bio *fbio, *bbio; 361 struct bvec_iter iter; 362 363 if (!bio) 364 return 0; 365 366 front_seg_size = bio->bi_seg_front_size; 367 368 switch (bio_op(bio)) { 369 case REQ_OP_DISCARD: 370 case REQ_OP_SECURE_ERASE: 371 case REQ_OP_WRITE_ZEROES: 372 return 0; 373 case REQ_OP_WRITE_SAME: 374 return 1; 375 } 376 377 fbio = bio; 378 seg_size = 0; 379 nr_phys_segs = 0; 380 for_each_bio(bio) { 381 bio_for_each_bvec(bv, bio, iter) { 382 if (prev) { 383 if (seg_size + bv.bv_len 384 > queue_max_segment_size(q)) 385 goto new_segment; 386 if (!biovec_phys_mergeable(q, &bvprv, &bv)) 387 goto new_segment; 388 389 seg_size += bv.bv_len; 390 bvprv = bv; 391 392 if (nr_phys_segs == 1 && seg_size > 393 front_seg_size) 394 front_seg_size = seg_size; 395 396 continue; 397 } 398 new_segment: 399 bvprv = bv; 400 prev = 1; 401 bvec_split_segs(q, &bv, &nr_phys_segs, &seg_size, 402 &front_seg_size, NULL, UINT_MAX); 403 } 404 bbio = bio; 405 } 406 407 fbio->bi_seg_front_size = front_seg_size; 408 if (seg_size > bbio->bi_seg_back_size) 409 bbio->bi_seg_back_size = seg_size; 410 411 return nr_phys_segs; 412 } 413 414 void blk_recalc_rq_segments(struct request *rq) 415 { 416 rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio); 417 } 418 419 void blk_recount_segments(struct request_queue *q, struct bio *bio) 420 { 421 struct bio *nxt = bio->bi_next; 422 423 bio->bi_next = NULL; 424 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio); 425 bio->bi_next = nxt; 426 427 bio_set_flag(bio, BIO_SEG_VALID); 428 } 429 430 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, 431 struct bio *nxt) 432 { 433 struct bio_vec end_bv = { NULL }, nxt_bv; 434 435 if (bio->bi_seg_back_size + nxt->bi_seg_front_size > 436 queue_max_segment_size(q)) 437 return 0; 438 439 if (!bio_has_data(bio)) 440 return 1; 441 442 bio_get_last_bvec(bio, &end_bv); 443 bio_get_first_bvec(nxt, &nxt_bv); 444 445 return biovec_phys_mergeable(q, &end_bv, &nxt_bv); 446 } 447 448 static inline struct scatterlist *blk_next_sg(struct scatterlist **sg, 449 struct scatterlist *sglist) 450 { 451 if (!*sg) 452 return sglist; 453 454 /* 455 * If the driver previously mapped a shorter list, we could see a 456 * termination bit prematurely unless it fully inits the sg table 457 * on each mapping. We KNOW that there must be more entries here 458 * or the driver would be buggy, so force clear the termination bit 459 * to avoid doing a full sg_init_table() in drivers for each command. 460 */ 461 sg_unmark_end(*sg); 462 return sg_next(*sg); 463 } 464 465 static unsigned blk_bvec_map_sg(struct request_queue *q, 466 struct bio_vec *bvec, struct scatterlist *sglist, 467 struct scatterlist **sg) 468 { 469 unsigned nbytes = bvec->bv_len; 470 unsigned nsegs = 0, total = 0, offset = 0; 471 472 while (nbytes > 0) { 473 unsigned seg_size; 474 struct page *pg; 475 unsigned idx; 476 477 *sg = blk_next_sg(sg, sglist); 478 479 seg_size = get_max_segment_size(q, bvec->bv_offset + total); 480 seg_size = min(nbytes, seg_size); 481 482 offset = (total + bvec->bv_offset) % PAGE_SIZE; 483 idx = (total + bvec->bv_offset) / PAGE_SIZE; 484 pg = bvec_nth_page(bvec->bv_page, idx); 485 486 sg_set_page(*sg, pg, seg_size, offset); 487 488 total += seg_size; 489 nbytes -= seg_size; 490 nsegs++; 491 } 492 493 return nsegs; 494 } 495 496 static inline void 497 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, 498 struct scatterlist *sglist, struct bio_vec *bvprv, 499 struct scatterlist **sg, int *nsegs) 500 { 501 502 int nbytes = bvec->bv_len; 503 504 if (*sg) { 505 if ((*sg)->length + nbytes > queue_max_segment_size(q)) 506 goto new_segment; 507 if (!biovec_phys_mergeable(q, bvprv, bvec)) 508 goto new_segment; 509 510 (*sg)->length += nbytes; 511 } else { 512 new_segment: 513 if (bvec->bv_offset + bvec->bv_len <= PAGE_SIZE) { 514 *sg = blk_next_sg(sg, sglist); 515 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); 516 (*nsegs) += 1; 517 } else 518 (*nsegs) += blk_bvec_map_sg(q, bvec, sglist, sg); 519 } 520 *bvprv = *bvec; 521 } 522 523 static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv, 524 struct scatterlist *sglist, struct scatterlist **sg) 525 { 526 *sg = sglist; 527 sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); 528 return 1; 529 } 530 531 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 532 struct scatterlist *sglist, 533 struct scatterlist **sg) 534 { 535 struct bio_vec bvec, bvprv = { NULL }; 536 struct bvec_iter iter; 537 int nsegs = 0; 538 539 for_each_bio(bio) 540 bio_for_each_bvec(bvec, bio, iter) 541 __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg, 542 &nsegs); 543 544 return nsegs; 545 } 546 547 /* 548 * map a request to scatterlist, return number of sg entries setup. Caller 549 * must make sure sg can hold rq->nr_phys_segments entries 550 */ 551 int blk_rq_map_sg(struct request_queue *q, struct request *rq, 552 struct scatterlist *sglist) 553 { 554 struct scatterlist *sg = NULL; 555 int nsegs = 0; 556 557 if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) 558 nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg); 559 else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME) 560 nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg); 561 else if (rq->bio) 562 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg); 563 564 if (unlikely(rq->rq_flags & RQF_COPY_USER) && 565 (blk_rq_bytes(rq) & q->dma_pad_mask)) { 566 unsigned int pad_len = 567 (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1; 568 569 sg->length += pad_len; 570 rq->extra_len += pad_len; 571 } 572 573 if (q->dma_drain_size && q->dma_drain_needed(rq)) { 574 if (op_is_write(req_op(rq))) 575 memset(q->dma_drain_buffer, 0, q->dma_drain_size); 576 577 sg_unmark_end(sg); 578 sg = sg_next(sg); 579 sg_set_page(sg, virt_to_page(q->dma_drain_buffer), 580 q->dma_drain_size, 581 ((unsigned long)q->dma_drain_buffer) & 582 (PAGE_SIZE - 1)); 583 nsegs++; 584 rq->extra_len += q->dma_drain_size; 585 } 586 587 if (sg) 588 sg_mark_end(sg); 589 590 /* 591 * Something must have been wrong if the figured number of 592 * segment is bigger than number of req's physical segments 593 */ 594 WARN_ON(nsegs > blk_rq_nr_phys_segments(rq)); 595 596 return nsegs; 597 } 598 EXPORT_SYMBOL(blk_rq_map_sg); 599 600 static inline int ll_new_hw_segment(struct request_queue *q, 601 struct request *req, 602 struct bio *bio) 603 { 604 int nr_phys_segs = bio_phys_segments(q, bio); 605 606 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) 607 goto no_merge; 608 609 if (blk_integrity_merge_bio(q, req, bio) == false) 610 goto no_merge; 611 612 /* 613 * This will form the start of a new hw segment. Bump both 614 * counters. 615 */ 616 req->nr_phys_segments += nr_phys_segs; 617 return 1; 618 619 no_merge: 620 req_set_nomerge(q, req); 621 return 0; 622 } 623 624 int ll_back_merge_fn(struct request_queue *q, struct request *req, 625 struct bio *bio) 626 { 627 if (req_gap_back_merge(req, bio)) 628 return 0; 629 if (blk_integrity_rq(req) && 630 integrity_req_gap_back_merge(req, bio)) 631 return 0; 632 if (blk_rq_sectors(req) + bio_sectors(bio) > 633 blk_rq_get_max_sectors(req, blk_rq_pos(req))) { 634 req_set_nomerge(q, req); 635 return 0; 636 } 637 if (!bio_flagged(req->biotail, BIO_SEG_VALID)) 638 blk_recount_segments(q, req->biotail); 639 if (!bio_flagged(bio, BIO_SEG_VALID)) 640 blk_recount_segments(q, bio); 641 642 return ll_new_hw_segment(q, req, bio); 643 } 644 645 int ll_front_merge_fn(struct request_queue *q, struct request *req, 646 struct bio *bio) 647 { 648 649 if (req_gap_front_merge(req, bio)) 650 return 0; 651 if (blk_integrity_rq(req) && 652 integrity_req_gap_front_merge(req, bio)) 653 return 0; 654 if (blk_rq_sectors(req) + bio_sectors(bio) > 655 blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { 656 req_set_nomerge(q, req); 657 return 0; 658 } 659 if (!bio_flagged(bio, BIO_SEG_VALID)) 660 blk_recount_segments(q, bio); 661 if (!bio_flagged(req->bio, BIO_SEG_VALID)) 662 blk_recount_segments(q, req->bio); 663 664 return ll_new_hw_segment(q, req, bio); 665 } 666 667 static bool req_attempt_discard_merge(struct request_queue *q, struct request *req, 668 struct request *next) 669 { 670 unsigned short segments = blk_rq_nr_discard_segments(req); 671 672 if (segments >= queue_max_discard_segments(q)) 673 goto no_merge; 674 if (blk_rq_sectors(req) + bio_sectors(next->bio) > 675 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 676 goto no_merge; 677 678 req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next); 679 return true; 680 no_merge: 681 req_set_nomerge(q, req); 682 return false; 683 } 684 685 static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 686 struct request *next) 687 { 688 int total_phys_segments; 689 unsigned int seg_size = 690 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; 691 692 if (req_gap_back_merge(req, next->bio)) 693 return 0; 694 695 /* 696 * Will it become too large? 697 */ 698 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 699 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 700 return 0; 701 702 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 703 if (blk_phys_contig_segment(q, req->biotail, next->bio)) { 704 if (req->nr_phys_segments == 1) 705 req->bio->bi_seg_front_size = seg_size; 706 if (next->nr_phys_segments == 1) 707 next->biotail->bi_seg_back_size = seg_size; 708 total_phys_segments--; 709 } 710 711 if (total_phys_segments > queue_max_segments(q)) 712 return 0; 713 714 if (blk_integrity_merge_rq(q, req, next) == false) 715 return 0; 716 717 /* Merge is OK... */ 718 req->nr_phys_segments = total_phys_segments; 719 return 1; 720 } 721 722 /** 723 * blk_rq_set_mixed_merge - mark a request as mixed merge 724 * @rq: request to mark as mixed merge 725 * 726 * Description: 727 * @rq is about to be mixed merged. Make sure the attributes 728 * which can be mixed are set in each bio and mark @rq as mixed 729 * merged. 730 */ 731 void blk_rq_set_mixed_merge(struct request *rq) 732 { 733 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; 734 struct bio *bio; 735 736 if (rq->rq_flags & RQF_MIXED_MERGE) 737 return; 738 739 /* 740 * @rq will no longer represent mixable attributes for all the 741 * contained bios. It will just track those of the first one. 742 * Distributes the attributs to each bio. 743 */ 744 for (bio = rq->bio; bio; bio = bio->bi_next) { 745 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 746 (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 747 bio->bi_opf |= ff; 748 } 749 rq->rq_flags |= RQF_MIXED_MERGE; 750 } 751 752 static void blk_account_io_merge(struct request *req) 753 { 754 if (blk_do_io_stat(req)) { 755 struct hd_struct *part; 756 757 part_stat_lock(); 758 part = req->part; 759 760 part_dec_in_flight(req->q, part, rq_data_dir(req)); 761 762 hd_struct_put(part); 763 part_stat_unlock(); 764 } 765 } 766 /* 767 * Two cases of handling DISCARD merge: 768 * If max_discard_segments > 1, the driver takes every bio 769 * as a range and send them to controller together. The ranges 770 * needn't to be contiguous. 771 * Otherwise, the bios/requests will be handled as same as 772 * others which should be contiguous. 773 */ 774 static inline bool blk_discard_mergable(struct request *req) 775 { 776 if (req_op(req) == REQ_OP_DISCARD && 777 queue_max_discard_segments(req->q) > 1) 778 return true; 779 return false; 780 } 781 782 static enum elv_merge blk_try_req_merge(struct request *req, 783 struct request *next) 784 { 785 if (blk_discard_mergable(req)) 786 return ELEVATOR_DISCARD_MERGE; 787 else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) 788 return ELEVATOR_BACK_MERGE; 789 790 return ELEVATOR_NO_MERGE; 791 } 792 793 /* 794 * For non-mq, this has to be called with the request spinlock acquired. 795 * For mq with scheduling, the appropriate queue wide lock should be held. 796 */ 797 static struct request *attempt_merge(struct request_queue *q, 798 struct request *req, struct request *next) 799 { 800 if (!rq_mergeable(req) || !rq_mergeable(next)) 801 return NULL; 802 803 if (req_op(req) != req_op(next)) 804 return NULL; 805 806 if (rq_data_dir(req) != rq_data_dir(next) 807 || req->rq_disk != next->rq_disk) 808 return NULL; 809 810 if (req_op(req) == REQ_OP_WRITE_SAME && 811 !blk_write_same_mergeable(req->bio, next->bio)) 812 return NULL; 813 814 /* 815 * Don't allow merge of different write hints, or for a hint with 816 * non-hint IO. 817 */ 818 if (req->write_hint != next->write_hint) 819 return NULL; 820 821 if (req->ioprio != next->ioprio) 822 return NULL; 823 824 /* 825 * If we are allowed to merge, then append bio list 826 * from next to rq and release next. merge_requests_fn 827 * will have updated segment counts, update sector 828 * counts here. Handle DISCARDs separately, as they 829 * have separate settings. 830 */ 831 832 switch (blk_try_req_merge(req, next)) { 833 case ELEVATOR_DISCARD_MERGE: 834 if (!req_attempt_discard_merge(q, req, next)) 835 return NULL; 836 break; 837 case ELEVATOR_BACK_MERGE: 838 if (!ll_merge_requests_fn(q, req, next)) 839 return NULL; 840 break; 841 default: 842 return NULL; 843 } 844 845 /* 846 * If failfast settings disagree or any of the two is already 847 * a mixed merge, mark both as mixed before proceeding. This 848 * makes sure that all involved bios have mixable attributes 849 * set properly. 850 */ 851 if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || 852 (req->cmd_flags & REQ_FAILFAST_MASK) != 853 (next->cmd_flags & REQ_FAILFAST_MASK)) { 854 blk_rq_set_mixed_merge(req); 855 blk_rq_set_mixed_merge(next); 856 } 857 858 /* 859 * At this point we have either done a back merge or front merge. We 860 * need the smaller start_time_ns of the merged requests to be the 861 * current request for accounting purposes. 862 */ 863 if (next->start_time_ns < req->start_time_ns) 864 req->start_time_ns = next->start_time_ns; 865 866 req->biotail->bi_next = next->bio; 867 req->biotail = next->biotail; 868 869 req->__data_len += blk_rq_bytes(next); 870 871 if (!blk_discard_mergable(req)) 872 elv_merge_requests(q, req, next); 873 874 /* 875 * 'next' is going away, so update stats accordingly 876 */ 877 blk_account_io_merge(next); 878 879 /* 880 * ownership of bio passed from next to req, return 'next' for 881 * the caller to free 882 */ 883 next->bio = NULL; 884 return next; 885 } 886 887 struct request *attempt_back_merge(struct request_queue *q, struct request *rq) 888 { 889 struct request *next = elv_latter_request(q, rq); 890 891 if (next) 892 return attempt_merge(q, rq, next); 893 894 return NULL; 895 } 896 897 struct request *attempt_front_merge(struct request_queue *q, struct request *rq) 898 { 899 struct request *prev = elv_former_request(q, rq); 900 901 if (prev) 902 return attempt_merge(q, prev, rq); 903 904 return NULL; 905 } 906 907 int blk_attempt_req_merge(struct request_queue *q, struct request *rq, 908 struct request *next) 909 { 910 struct request *free; 911 912 free = attempt_merge(q, rq, next); 913 if (free) { 914 blk_put_request(free); 915 return 1; 916 } 917 918 return 0; 919 } 920 921 bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 922 { 923 if (!rq_mergeable(rq) || !bio_mergeable(bio)) 924 return false; 925 926 if (req_op(rq) != bio_op(bio)) 927 return false; 928 929 /* different data direction or already started, don't merge */ 930 if (bio_data_dir(bio) != rq_data_dir(rq)) 931 return false; 932 933 /* must be same device */ 934 if (rq->rq_disk != bio->bi_disk) 935 return false; 936 937 /* only merge integrity protected bio into ditto rq */ 938 if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 939 return false; 940 941 /* must be using the same buffer */ 942 if (req_op(rq) == REQ_OP_WRITE_SAME && 943 !blk_write_same_mergeable(rq->bio, bio)) 944 return false; 945 946 /* 947 * Don't allow merge of different write hints, or for a hint with 948 * non-hint IO. 949 */ 950 if (rq->write_hint != bio->bi_write_hint) 951 return false; 952 953 if (rq->ioprio != bio_prio(bio)) 954 return false; 955 956 return true; 957 } 958 959 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) 960 { 961 if (blk_discard_mergable(rq)) 962 return ELEVATOR_DISCARD_MERGE; 963 else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 964 return ELEVATOR_BACK_MERGE; 965 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 966 return ELEVATOR_FRONT_MERGE; 967 return ELEVATOR_NO_MERGE; 968 } 969