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/blk-integrity.h> 10 #include <linux/scatterlist.h> 11 #include <linux/part_stat.h> 12 #include <linux/blk-cgroup.h> 13 14 #include <trace/events/block.h> 15 16 #include "blk.h" 17 #include "blk-mq-sched.h" 18 #include "blk-rq-qos.h" 19 #include "blk-throttle.h" 20 21 static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv) 22 { 23 *bv = mp_bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter); 24 } 25 26 static inline void bio_get_last_bvec(struct bio *bio, struct bio_vec *bv) 27 { 28 struct bvec_iter iter = bio->bi_iter; 29 int idx; 30 31 bio_get_first_bvec(bio, bv); 32 if (bv->bv_len == bio->bi_iter.bi_size) 33 return; /* this bio only has a single bvec */ 34 35 bio_advance_iter(bio, &iter, iter.bi_size); 36 37 if (!iter.bi_bvec_done) 38 idx = iter.bi_idx - 1; 39 else /* in the middle of bvec */ 40 idx = iter.bi_idx; 41 42 *bv = bio->bi_io_vec[idx]; 43 44 /* 45 * iter.bi_bvec_done records actual length of the last bvec 46 * if this bio ends in the middle of one io vector 47 */ 48 if (iter.bi_bvec_done) 49 bv->bv_len = iter.bi_bvec_done; 50 } 51 52 static inline bool bio_will_gap(struct request_queue *q, 53 struct request *prev_rq, struct bio *prev, struct bio *next) 54 { 55 struct bio_vec pb, nb; 56 57 if (!bio_has_data(prev) || !queue_virt_boundary(q)) 58 return false; 59 60 /* 61 * Don't merge if the 1st bio starts with non-zero offset, otherwise it 62 * is quite difficult to respect the sg gap limit. We work hard to 63 * merge a huge number of small single bios in case of mkfs. 64 */ 65 if (prev_rq) 66 bio_get_first_bvec(prev_rq->bio, &pb); 67 else 68 bio_get_first_bvec(prev, &pb); 69 if (pb.bv_offset & queue_virt_boundary(q)) 70 return true; 71 72 /* 73 * We don't need to worry about the situation that the merged segment 74 * ends in unaligned virt boundary: 75 * 76 * - if 'pb' ends aligned, the merged segment ends aligned 77 * - if 'pb' ends unaligned, the next bio must include 78 * one single bvec of 'nb', otherwise the 'nb' can't 79 * merge with 'pb' 80 */ 81 bio_get_last_bvec(prev, &pb); 82 bio_get_first_bvec(next, &nb); 83 if (biovec_phys_mergeable(q, &pb, &nb)) 84 return false; 85 return __bvec_gap_to_prev(&q->limits, &pb, nb.bv_offset); 86 } 87 88 static inline bool req_gap_back_merge(struct request *req, struct bio *bio) 89 { 90 return bio_will_gap(req->q, req, req->biotail, bio); 91 } 92 93 static inline bool req_gap_front_merge(struct request *req, struct bio *bio) 94 { 95 return bio_will_gap(req->q, NULL, bio, req->bio); 96 } 97 98 /* 99 * The max size one bio can handle is UINT_MAX becasue bvec_iter.bi_size 100 * is defined as 'unsigned int', meantime it has to be aligned to with the 101 * logical block size, which is the minimum accepted unit by hardware. 102 */ 103 static unsigned int bio_allowed_max_sectors(const struct queue_limits *lim) 104 { 105 return round_down(UINT_MAX, lim->logical_block_size) >> SECTOR_SHIFT; 106 } 107 108 static struct bio *bio_split_discard(struct bio *bio, 109 const struct queue_limits *lim, 110 unsigned *nsegs, struct bio_set *bs) 111 { 112 unsigned int max_discard_sectors, granularity; 113 sector_t tmp; 114 unsigned split_sectors; 115 116 *nsegs = 1; 117 118 /* Zero-sector (unknown) and one-sector granularities are the same. */ 119 granularity = max(lim->discard_granularity >> 9, 1U); 120 121 max_discard_sectors = 122 min(lim->max_discard_sectors, bio_allowed_max_sectors(lim)); 123 max_discard_sectors -= max_discard_sectors % granularity; 124 125 if (unlikely(!max_discard_sectors)) { 126 /* XXX: warn */ 127 return NULL; 128 } 129 130 if (bio_sectors(bio) <= max_discard_sectors) 131 return NULL; 132 133 split_sectors = max_discard_sectors; 134 135 /* 136 * If the next starting sector would be misaligned, stop the discard at 137 * the previous aligned sector. 138 */ 139 tmp = bio->bi_iter.bi_sector + split_sectors - 140 ((lim->discard_alignment >> 9) % granularity); 141 tmp = sector_div(tmp, granularity); 142 143 if (split_sectors > tmp) 144 split_sectors -= tmp; 145 146 return bio_split(bio, split_sectors, GFP_NOIO, bs); 147 } 148 149 static struct bio *bio_split_write_zeroes(struct bio *bio, 150 const struct queue_limits *lim, 151 unsigned *nsegs, struct bio_set *bs) 152 { 153 *nsegs = 0; 154 if (!lim->max_write_zeroes_sectors) 155 return NULL; 156 if (bio_sectors(bio) <= lim->max_write_zeroes_sectors) 157 return NULL; 158 return bio_split(bio, lim->max_write_zeroes_sectors, GFP_NOIO, bs); 159 } 160 161 /* 162 * Return the maximum number of sectors from the start of a bio that may be 163 * submitted as a single request to a block device. If enough sectors remain, 164 * align the end to the physical block size. Otherwise align the end to the 165 * logical block size. This approach minimizes the number of non-aligned 166 * requests that are submitted to a block device if the start of a bio is not 167 * aligned to a physical block boundary. 168 */ 169 static inline unsigned get_max_io_size(struct bio *bio, 170 const struct queue_limits *lim) 171 { 172 unsigned pbs = lim->physical_block_size >> SECTOR_SHIFT; 173 unsigned lbs = lim->logical_block_size >> SECTOR_SHIFT; 174 unsigned max_sectors = lim->max_sectors, start, end; 175 176 if (lim->chunk_sectors) { 177 max_sectors = min(max_sectors, 178 blk_chunk_sectors_left(bio->bi_iter.bi_sector, 179 lim->chunk_sectors)); 180 } 181 182 start = bio->bi_iter.bi_sector & (pbs - 1); 183 end = (start + max_sectors) & ~(pbs - 1); 184 if (end > start) 185 return end - start; 186 return max_sectors & ~(lbs - 1); 187 } 188 189 /** 190 * get_max_segment_size() - maximum number of bytes to add as a single segment 191 * @lim: Request queue limits. 192 * @start_page: See below. 193 * @offset: Offset from @start_page where to add a segment. 194 * 195 * Returns the maximum number of bytes that can be added as a single segment. 196 */ 197 static inline unsigned get_max_segment_size(const struct queue_limits *lim, 198 struct page *start_page, unsigned long offset) 199 { 200 unsigned long mask = lim->seg_boundary_mask; 201 202 offset = mask & (page_to_phys(start_page) + offset); 203 204 /* 205 * Prevent an overflow if mask = ULONG_MAX and offset = 0 by adding 1 206 * after having calculated the minimum. 207 */ 208 return min(mask - offset, (unsigned long)lim->max_segment_size - 1) + 1; 209 } 210 211 /** 212 * bvec_split_segs - verify whether or not a bvec should be split in the middle 213 * @lim: [in] queue limits to split based on 214 * @bv: [in] bvec to examine 215 * @nsegs: [in,out] Number of segments in the bio being built. Incremented 216 * by the number of segments from @bv that may be appended to that 217 * bio without exceeding @max_segs 218 * @bytes: [in,out] Number of bytes in the bio being built. Incremented 219 * by the number of bytes from @bv that may be appended to that 220 * bio without exceeding @max_bytes 221 * @max_segs: [in] upper bound for *@nsegs 222 * @max_bytes: [in] upper bound for *@bytes 223 * 224 * When splitting a bio, it can happen that a bvec is encountered that is too 225 * big to fit in a single segment and hence that it has to be split in the 226 * middle. This function verifies whether or not that should happen. The value 227 * %true is returned if and only if appending the entire @bv to a bio with 228 * *@nsegs segments and *@sectors sectors would make that bio unacceptable for 229 * the block driver. 230 */ 231 static bool bvec_split_segs(const struct queue_limits *lim, 232 const struct bio_vec *bv, unsigned *nsegs, unsigned *bytes, 233 unsigned max_segs, unsigned max_bytes) 234 { 235 unsigned max_len = min(max_bytes, UINT_MAX) - *bytes; 236 unsigned len = min(bv->bv_len, max_len); 237 unsigned total_len = 0; 238 unsigned seg_size = 0; 239 240 while (len && *nsegs < max_segs) { 241 seg_size = get_max_segment_size(lim, bv->bv_page, 242 bv->bv_offset + total_len); 243 seg_size = min(seg_size, len); 244 245 (*nsegs)++; 246 total_len += seg_size; 247 len -= seg_size; 248 249 if ((bv->bv_offset + total_len) & lim->virt_boundary_mask) 250 break; 251 } 252 253 *bytes += total_len; 254 255 /* tell the caller to split the bvec if it is too big to fit */ 256 return len > 0 || bv->bv_len > max_len; 257 } 258 259 /** 260 * bio_split_rw - split a bio in two bios 261 * @bio: [in] bio to be split 262 * @lim: [in] queue limits to split based on 263 * @segs: [out] number of segments in the bio with the first half of the sectors 264 * @bs: [in] bio set to allocate the clone from 265 * @max_bytes: [in] maximum number of bytes per bio 266 * 267 * Clone @bio, update the bi_iter of the clone to represent the first sectors 268 * of @bio and update @bio->bi_iter to represent the remaining sectors. The 269 * following is guaranteed for the cloned bio: 270 * - That it has at most @max_bytes worth of data 271 * - That it has at most queue_max_segments(@q) segments. 272 * 273 * Except for discard requests the cloned bio will point at the bi_io_vec of 274 * the original bio. It is the responsibility of the caller to ensure that the 275 * original bio is not freed before the cloned bio. The caller is also 276 * responsible for ensuring that @bs is only destroyed after processing of the 277 * split bio has finished. 278 */ 279 static struct bio *bio_split_rw(struct bio *bio, const struct queue_limits *lim, 280 unsigned *segs, struct bio_set *bs, unsigned max_bytes) 281 { 282 struct bio_vec bv, bvprv, *bvprvp = NULL; 283 struct bvec_iter iter; 284 unsigned nsegs = 0, bytes = 0; 285 286 bio_for_each_bvec(bv, bio, iter) { 287 /* 288 * If the queue doesn't support SG gaps and adding this 289 * offset would create a gap, disallow it. 290 */ 291 if (bvprvp && bvec_gap_to_prev(lim, bvprvp, bv.bv_offset)) 292 goto split; 293 294 if (nsegs < lim->max_segments && 295 bytes + bv.bv_len <= max_bytes && 296 bv.bv_offset + bv.bv_len <= PAGE_SIZE) { 297 nsegs++; 298 bytes += bv.bv_len; 299 } else { 300 if (bvec_split_segs(lim, &bv, &nsegs, &bytes, 301 lim->max_segments, max_bytes)) 302 goto split; 303 } 304 305 bvprv = bv; 306 bvprvp = &bvprv; 307 } 308 309 *segs = nsegs; 310 return NULL; 311 split: 312 *segs = nsegs; 313 314 /* 315 * Individual bvecs might not be logical block aligned. Round down the 316 * split size so that each bio is properly block size aligned, even if 317 * we do not use the full hardware limits. 318 */ 319 bytes = ALIGN_DOWN(bytes, lim->logical_block_size); 320 321 /* 322 * Bio splitting may cause subtle trouble such as hang when doing sync 323 * iopoll in direct IO routine. Given performance gain of iopoll for 324 * big IO can be trival, disable iopoll when split needed. 325 */ 326 bio_clear_polled(bio); 327 return bio_split(bio, bytes >> SECTOR_SHIFT, GFP_NOIO, bs); 328 } 329 330 /** 331 * __bio_split_to_limits - split a bio to fit the queue limits 332 * @bio: bio to be split 333 * @lim: queue limits to split based on 334 * @nr_segs: returns the number of segments in the returned bio 335 * 336 * Check if @bio needs splitting based on the queue limits, and if so split off 337 * a bio fitting the limits from the beginning of @bio and return it. @bio is 338 * shortened to the remainder and re-submitted. 339 * 340 * The split bio is allocated from @q->bio_split, which is provided by the 341 * block layer. 342 */ 343 struct bio *__bio_split_to_limits(struct bio *bio, 344 const struct queue_limits *lim, 345 unsigned int *nr_segs) 346 { 347 struct bio_set *bs = &bio->bi_bdev->bd_disk->bio_split; 348 struct bio *split; 349 350 switch (bio_op(bio)) { 351 case REQ_OP_DISCARD: 352 case REQ_OP_SECURE_ERASE: 353 split = bio_split_discard(bio, lim, nr_segs, bs); 354 break; 355 case REQ_OP_WRITE_ZEROES: 356 split = bio_split_write_zeroes(bio, lim, nr_segs, bs); 357 break; 358 default: 359 split = bio_split_rw(bio, lim, nr_segs, bs, 360 get_max_io_size(bio, lim) << SECTOR_SHIFT); 361 if (IS_ERR(split)) 362 return NULL; 363 break; 364 } 365 366 if (split) { 367 /* there isn't chance to merge the split bio */ 368 split->bi_opf |= REQ_NOMERGE; 369 370 blkcg_bio_issue_init(split); 371 bio_chain(split, bio); 372 trace_block_split(split, bio->bi_iter.bi_sector); 373 submit_bio_noacct(bio); 374 return split; 375 } 376 return bio; 377 } 378 379 /** 380 * bio_split_to_limits - split a bio to fit the queue limits 381 * @bio: bio to be split 382 * 383 * Check if @bio needs splitting based on the queue limits of @bio->bi_bdev, and 384 * if so split off a bio fitting the limits from the beginning of @bio and 385 * return it. @bio is shortened to the remainder and re-submitted. 386 * 387 * The split bio is allocated from @q->bio_split, which is provided by the 388 * block layer. 389 */ 390 struct bio *bio_split_to_limits(struct bio *bio) 391 { 392 const struct queue_limits *lim = &bdev_get_queue(bio->bi_bdev)->limits; 393 unsigned int nr_segs; 394 395 if (bio_may_exceed_limits(bio, lim)) 396 return __bio_split_to_limits(bio, lim, &nr_segs); 397 return bio; 398 } 399 EXPORT_SYMBOL(bio_split_to_limits); 400 401 unsigned int blk_recalc_rq_segments(struct request *rq) 402 { 403 unsigned int nr_phys_segs = 0; 404 unsigned int bytes = 0; 405 struct req_iterator iter; 406 struct bio_vec bv; 407 408 if (!rq->bio) 409 return 0; 410 411 switch (bio_op(rq->bio)) { 412 case REQ_OP_DISCARD: 413 case REQ_OP_SECURE_ERASE: 414 if (queue_max_discard_segments(rq->q) > 1) { 415 struct bio *bio = rq->bio; 416 417 for_each_bio(bio) 418 nr_phys_segs++; 419 return nr_phys_segs; 420 } 421 return 1; 422 case REQ_OP_WRITE_ZEROES: 423 return 0; 424 default: 425 break; 426 } 427 428 rq_for_each_bvec(bv, rq, iter) 429 bvec_split_segs(&rq->q->limits, &bv, &nr_phys_segs, &bytes, 430 UINT_MAX, UINT_MAX); 431 return nr_phys_segs; 432 } 433 434 static inline struct scatterlist *blk_next_sg(struct scatterlist **sg, 435 struct scatterlist *sglist) 436 { 437 if (!*sg) 438 return sglist; 439 440 /* 441 * If the driver previously mapped a shorter list, we could see a 442 * termination bit prematurely unless it fully inits the sg table 443 * on each mapping. We KNOW that there must be more entries here 444 * or the driver would be buggy, so force clear the termination bit 445 * to avoid doing a full sg_init_table() in drivers for each command. 446 */ 447 sg_unmark_end(*sg); 448 return sg_next(*sg); 449 } 450 451 static unsigned blk_bvec_map_sg(struct request_queue *q, 452 struct bio_vec *bvec, struct scatterlist *sglist, 453 struct scatterlist **sg) 454 { 455 unsigned nbytes = bvec->bv_len; 456 unsigned nsegs = 0, total = 0; 457 458 while (nbytes > 0) { 459 unsigned offset = bvec->bv_offset + total; 460 unsigned len = min(get_max_segment_size(&q->limits, 461 bvec->bv_page, offset), nbytes); 462 struct page *page = bvec->bv_page; 463 464 /* 465 * Unfortunately a fair number of drivers barf on scatterlists 466 * that have an offset larger than PAGE_SIZE, despite other 467 * subsystems dealing with that invariant just fine. For now 468 * stick to the legacy format where we never present those from 469 * the block layer, but the code below should be removed once 470 * these offenders (mostly MMC/SD drivers) are fixed. 471 */ 472 page += (offset >> PAGE_SHIFT); 473 offset &= ~PAGE_MASK; 474 475 *sg = blk_next_sg(sg, sglist); 476 sg_set_page(*sg, page, len, offset); 477 478 total += len; 479 nbytes -= len; 480 nsegs++; 481 } 482 483 return nsegs; 484 } 485 486 static inline int __blk_bvec_map_sg(struct bio_vec bv, 487 struct scatterlist *sglist, struct scatterlist **sg) 488 { 489 *sg = blk_next_sg(sg, sglist); 490 sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); 491 return 1; 492 } 493 494 /* only try to merge bvecs into one sg if they are from two bios */ 495 static inline bool 496 __blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec, 497 struct bio_vec *bvprv, struct scatterlist **sg) 498 { 499 500 int nbytes = bvec->bv_len; 501 502 if (!*sg) 503 return false; 504 505 if ((*sg)->length + nbytes > queue_max_segment_size(q)) 506 return false; 507 508 if (!biovec_phys_mergeable(q, bvprv, bvec)) 509 return false; 510 511 (*sg)->length += nbytes; 512 513 return true; 514 } 515 516 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 517 struct scatterlist *sglist, 518 struct scatterlist **sg) 519 { 520 struct bio_vec bvec, bvprv = { NULL }; 521 struct bvec_iter iter; 522 int nsegs = 0; 523 bool new_bio = false; 524 525 for_each_bio(bio) { 526 bio_for_each_bvec(bvec, bio, iter) { 527 /* 528 * Only try to merge bvecs from two bios given we 529 * have done bio internal merge when adding pages 530 * to bio 531 */ 532 if (new_bio && 533 __blk_segment_map_sg_merge(q, &bvec, &bvprv, sg)) 534 goto next_bvec; 535 536 if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE) 537 nsegs += __blk_bvec_map_sg(bvec, sglist, sg); 538 else 539 nsegs += blk_bvec_map_sg(q, &bvec, sglist, sg); 540 next_bvec: 541 new_bio = false; 542 } 543 if (likely(bio->bi_iter.bi_size)) { 544 bvprv = bvec; 545 new_bio = true; 546 } 547 } 548 549 return nsegs; 550 } 551 552 /* 553 * map a request to scatterlist, return number of sg entries setup. Caller 554 * must make sure sg can hold rq->nr_phys_segments entries 555 */ 556 int __blk_rq_map_sg(struct request_queue *q, struct request *rq, 557 struct scatterlist *sglist, struct scatterlist **last_sg) 558 { 559 int nsegs = 0; 560 561 if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) 562 nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, last_sg); 563 else if (rq->bio) 564 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg); 565 566 if (*last_sg) 567 sg_mark_end(*last_sg); 568 569 /* 570 * Something must have been wrong if the figured number of 571 * segment is bigger than number of req's physical segments 572 */ 573 WARN_ON(nsegs > blk_rq_nr_phys_segments(rq)); 574 575 return nsegs; 576 } 577 EXPORT_SYMBOL(__blk_rq_map_sg); 578 579 static inline unsigned int blk_rq_get_max_segments(struct request *rq) 580 { 581 if (req_op(rq) == REQ_OP_DISCARD) 582 return queue_max_discard_segments(rq->q); 583 return queue_max_segments(rq->q); 584 } 585 586 static inline unsigned int blk_rq_get_max_sectors(struct request *rq, 587 sector_t offset) 588 { 589 struct request_queue *q = rq->q; 590 unsigned int max_sectors; 591 592 if (blk_rq_is_passthrough(rq)) 593 return q->limits.max_hw_sectors; 594 595 max_sectors = blk_queue_get_max_sectors(q, req_op(rq)); 596 if (!q->limits.chunk_sectors || 597 req_op(rq) == REQ_OP_DISCARD || 598 req_op(rq) == REQ_OP_SECURE_ERASE) 599 return max_sectors; 600 return min(max_sectors, 601 blk_chunk_sectors_left(offset, q->limits.chunk_sectors)); 602 } 603 604 static inline int ll_new_hw_segment(struct request *req, struct bio *bio, 605 unsigned int nr_phys_segs) 606 { 607 if (!blk_cgroup_mergeable(req, bio)) 608 goto no_merge; 609 610 if (blk_integrity_merge_bio(req->q, req, bio) == false) 611 goto no_merge; 612 613 /* discard request merge won't add new segment */ 614 if (req_op(req) == REQ_OP_DISCARD) 615 return 1; 616 617 if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req)) 618 goto no_merge; 619 620 /* 621 * This will form the start of a new hw segment. Bump both 622 * counters. 623 */ 624 req->nr_phys_segments += nr_phys_segs; 625 return 1; 626 627 no_merge: 628 req_set_nomerge(req->q, req); 629 return 0; 630 } 631 632 int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs) 633 { 634 if (req_gap_back_merge(req, bio)) 635 return 0; 636 if (blk_integrity_rq(req) && 637 integrity_req_gap_back_merge(req, bio)) 638 return 0; 639 if (!bio_crypt_ctx_back_mergeable(req, bio)) 640 return 0; 641 if (blk_rq_sectors(req) + bio_sectors(bio) > 642 blk_rq_get_max_sectors(req, blk_rq_pos(req))) { 643 req_set_nomerge(req->q, req); 644 return 0; 645 } 646 647 return ll_new_hw_segment(req, bio, nr_segs); 648 } 649 650 static int ll_front_merge_fn(struct request *req, struct bio *bio, 651 unsigned int nr_segs) 652 { 653 if (req_gap_front_merge(req, bio)) 654 return 0; 655 if (blk_integrity_rq(req) && 656 integrity_req_gap_front_merge(req, bio)) 657 return 0; 658 if (!bio_crypt_ctx_front_mergeable(req, bio)) 659 return 0; 660 if (blk_rq_sectors(req) + bio_sectors(bio) > 661 blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { 662 req_set_nomerge(req->q, req); 663 return 0; 664 } 665 666 return ll_new_hw_segment(req, bio, nr_segs); 667 } 668 669 static bool req_attempt_discard_merge(struct request_queue *q, struct request *req, 670 struct request *next) 671 { 672 unsigned short segments = blk_rq_nr_discard_segments(req); 673 674 if (segments >= queue_max_discard_segments(q)) 675 goto no_merge; 676 if (blk_rq_sectors(req) + bio_sectors(next->bio) > 677 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 678 goto no_merge; 679 680 req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next); 681 return true; 682 no_merge: 683 req_set_nomerge(q, req); 684 return false; 685 } 686 687 static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 688 struct request *next) 689 { 690 int total_phys_segments; 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 (total_phys_segments > blk_rq_get_max_segments(req)) 704 return 0; 705 706 if (!blk_cgroup_mergeable(req, next->bio)) 707 return 0; 708 709 if (blk_integrity_merge_rq(q, req, next) == false) 710 return 0; 711 712 if (!bio_crypt_ctx_merge_rq(req, next)) 713 return 0; 714 715 /* Merge is OK... */ 716 req->nr_phys_segments = total_phys_segments; 717 return 1; 718 } 719 720 /** 721 * blk_rq_set_mixed_merge - mark a request as mixed merge 722 * @rq: request to mark as mixed merge 723 * 724 * Description: 725 * @rq is about to be mixed merged. Make sure the attributes 726 * which can be mixed are set in each bio and mark @rq as mixed 727 * merged. 728 */ 729 void blk_rq_set_mixed_merge(struct request *rq) 730 { 731 blk_opf_t ff = rq->cmd_flags & REQ_FAILFAST_MASK; 732 struct bio *bio; 733 734 if (rq->rq_flags & RQF_MIXED_MERGE) 735 return; 736 737 /* 738 * @rq will no longer represent mixable attributes for all the 739 * contained bios. It will just track those of the first one. 740 * Distributes the attributs to each bio. 741 */ 742 for (bio = rq->bio; bio; bio = bio->bi_next) { 743 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 744 (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 745 bio->bi_opf |= ff; 746 } 747 rq->rq_flags |= RQF_MIXED_MERGE; 748 } 749 750 static void blk_account_io_merge_request(struct request *req) 751 { 752 if (blk_do_io_stat(req)) { 753 part_stat_lock(); 754 part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); 755 part_stat_unlock(); 756 } 757 } 758 759 static enum elv_merge blk_try_req_merge(struct request *req, 760 struct request *next) 761 { 762 if (blk_discard_mergable(req)) 763 return ELEVATOR_DISCARD_MERGE; 764 else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) 765 return ELEVATOR_BACK_MERGE; 766 767 return ELEVATOR_NO_MERGE; 768 } 769 770 /* 771 * For non-mq, this has to be called with the request spinlock acquired. 772 * For mq with scheduling, the appropriate queue wide lock should be held. 773 */ 774 static struct request *attempt_merge(struct request_queue *q, 775 struct request *req, struct request *next) 776 { 777 if (!rq_mergeable(req) || !rq_mergeable(next)) 778 return NULL; 779 780 if (req_op(req) != req_op(next)) 781 return NULL; 782 783 if (rq_data_dir(req) != rq_data_dir(next)) 784 return NULL; 785 786 if (req->ioprio != next->ioprio) 787 return NULL; 788 789 /* 790 * If we are allowed to merge, then append bio list 791 * from next to rq and release next. merge_requests_fn 792 * will have updated segment counts, update sector 793 * counts here. Handle DISCARDs separately, as they 794 * have separate settings. 795 */ 796 797 switch (blk_try_req_merge(req, next)) { 798 case ELEVATOR_DISCARD_MERGE: 799 if (!req_attempt_discard_merge(q, req, next)) 800 return NULL; 801 break; 802 case ELEVATOR_BACK_MERGE: 803 if (!ll_merge_requests_fn(q, req, next)) 804 return NULL; 805 break; 806 default: 807 return NULL; 808 } 809 810 /* 811 * If failfast settings disagree or any of the two is already 812 * a mixed merge, mark both as mixed before proceeding. This 813 * makes sure that all involved bios have mixable attributes 814 * set properly. 815 */ 816 if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || 817 (req->cmd_flags & REQ_FAILFAST_MASK) != 818 (next->cmd_flags & REQ_FAILFAST_MASK)) { 819 blk_rq_set_mixed_merge(req); 820 blk_rq_set_mixed_merge(next); 821 } 822 823 /* 824 * At this point we have either done a back merge or front merge. We 825 * need the smaller start_time_ns of the merged requests to be the 826 * current request for accounting purposes. 827 */ 828 if (next->start_time_ns < req->start_time_ns) 829 req->start_time_ns = next->start_time_ns; 830 831 req->biotail->bi_next = next->bio; 832 req->biotail = next->biotail; 833 834 req->__data_len += blk_rq_bytes(next); 835 836 if (!blk_discard_mergable(req)) 837 elv_merge_requests(q, req, next); 838 839 /* 840 * 'next' is going away, so update stats accordingly 841 */ 842 blk_account_io_merge_request(next); 843 844 trace_block_rq_merge(next); 845 846 /* 847 * ownership of bio passed from next to req, return 'next' for 848 * the caller to free 849 */ 850 next->bio = NULL; 851 return next; 852 } 853 854 static struct request *attempt_back_merge(struct request_queue *q, 855 struct request *rq) 856 { 857 struct request *next = elv_latter_request(q, rq); 858 859 if (next) 860 return attempt_merge(q, rq, next); 861 862 return NULL; 863 } 864 865 static struct request *attempt_front_merge(struct request_queue *q, 866 struct request *rq) 867 { 868 struct request *prev = elv_former_request(q, rq); 869 870 if (prev) 871 return attempt_merge(q, prev, rq); 872 873 return NULL; 874 } 875 876 /* 877 * Try to merge 'next' into 'rq'. Return true if the merge happened, false 878 * otherwise. The caller is responsible for freeing 'next' if the merge 879 * happened. 880 */ 881 bool blk_attempt_req_merge(struct request_queue *q, struct request *rq, 882 struct request *next) 883 { 884 return attempt_merge(q, rq, next); 885 } 886 887 bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 888 { 889 if (!rq_mergeable(rq) || !bio_mergeable(bio)) 890 return false; 891 892 if (req_op(rq) != bio_op(bio)) 893 return false; 894 895 /* different data direction or already started, don't merge */ 896 if (bio_data_dir(bio) != rq_data_dir(rq)) 897 return false; 898 899 /* don't merge across cgroup boundaries */ 900 if (!blk_cgroup_mergeable(rq, bio)) 901 return false; 902 903 /* only merge integrity protected bio into ditto rq */ 904 if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 905 return false; 906 907 /* Only merge if the crypt contexts are compatible */ 908 if (!bio_crypt_rq_ctx_compatible(rq, bio)) 909 return false; 910 911 if (rq->ioprio != bio_prio(bio)) 912 return false; 913 914 return true; 915 } 916 917 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) 918 { 919 if (blk_discard_mergable(rq)) 920 return ELEVATOR_DISCARD_MERGE; 921 else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 922 return ELEVATOR_BACK_MERGE; 923 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 924 return ELEVATOR_FRONT_MERGE; 925 return ELEVATOR_NO_MERGE; 926 } 927 928 static void blk_account_io_merge_bio(struct request *req) 929 { 930 if (!blk_do_io_stat(req)) 931 return; 932 933 part_stat_lock(); 934 part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); 935 part_stat_unlock(); 936 } 937 938 enum bio_merge_status { 939 BIO_MERGE_OK, 940 BIO_MERGE_NONE, 941 BIO_MERGE_FAILED, 942 }; 943 944 static enum bio_merge_status bio_attempt_back_merge(struct request *req, 945 struct bio *bio, unsigned int nr_segs) 946 { 947 const blk_opf_t ff = bio->bi_opf & REQ_FAILFAST_MASK; 948 949 if (!ll_back_merge_fn(req, bio, nr_segs)) 950 return BIO_MERGE_FAILED; 951 952 trace_block_bio_backmerge(bio); 953 rq_qos_merge(req->q, req, bio); 954 955 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) 956 blk_rq_set_mixed_merge(req); 957 958 req->biotail->bi_next = bio; 959 req->biotail = bio; 960 req->__data_len += bio->bi_iter.bi_size; 961 962 bio_crypt_free_ctx(bio); 963 964 blk_account_io_merge_bio(req); 965 return BIO_MERGE_OK; 966 } 967 968 static enum bio_merge_status bio_attempt_front_merge(struct request *req, 969 struct bio *bio, unsigned int nr_segs) 970 { 971 const blk_opf_t ff = bio->bi_opf & REQ_FAILFAST_MASK; 972 973 if (!ll_front_merge_fn(req, bio, nr_segs)) 974 return BIO_MERGE_FAILED; 975 976 trace_block_bio_frontmerge(bio); 977 rq_qos_merge(req->q, req, bio); 978 979 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) 980 blk_rq_set_mixed_merge(req); 981 982 bio->bi_next = req->bio; 983 req->bio = bio; 984 985 req->__sector = bio->bi_iter.bi_sector; 986 req->__data_len += bio->bi_iter.bi_size; 987 988 bio_crypt_do_front_merge(req, bio); 989 990 blk_account_io_merge_bio(req); 991 return BIO_MERGE_OK; 992 } 993 994 static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q, 995 struct request *req, struct bio *bio) 996 { 997 unsigned short segments = blk_rq_nr_discard_segments(req); 998 999 if (segments >= queue_max_discard_segments(q)) 1000 goto no_merge; 1001 if (blk_rq_sectors(req) + bio_sectors(bio) > 1002 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 1003 goto no_merge; 1004 1005 rq_qos_merge(q, req, bio); 1006 1007 req->biotail->bi_next = bio; 1008 req->biotail = bio; 1009 req->__data_len += bio->bi_iter.bi_size; 1010 req->nr_phys_segments = segments + 1; 1011 1012 blk_account_io_merge_bio(req); 1013 return BIO_MERGE_OK; 1014 no_merge: 1015 req_set_nomerge(q, req); 1016 return BIO_MERGE_FAILED; 1017 } 1018 1019 static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q, 1020 struct request *rq, 1021 struct bio *bio, 1022 unsigned int nr_segs, 1023 bool sched_allow_merge) 1024 { 1025 if (!blk_rq_merge_ok(rq, bio)) 1026 return BIO_MERGE_NONE; 1027 1028 switch (blk_try_merge(rq, bio)) { 1029 case ELEVATOR_BACK_MERGE: 1030 if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) 1031 return bio_attempt_back_merge(rq, bio, nr_segs); 1032 break; 1033 case ELEVATOR_FRONT_MERGE: 1034 if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) 1035 return bio_attempt_front_merge(rq, bio, nr_segs); 1036 break; 1037 case ELEVATOR_DISCARD_MERGE: 1038 return bio_attempt_discard_merge(q, rq, bio); 1039 default: 1040 return BIO_MERGE_NONE; 1041 } 1042 1043 return BIO_MERGE_FAILED; 1044 } 1045 1046 /** 1047 * blk_attempt_plug_merge - try to merge with %current's plugged list 1048 * @q: request_queue new bio is being queued at 1049 * @bio: new bio being queued 1050 * @nr_segs: number of segments in @bio 1051 * from the passed in @q already in the plug list 1052 * 1053 * Determine whether @bio being queued on @q can be merged with the previous 1054 * request on %current's plugged list. Returns %true if merge was successful, 1055 * otherwise %false. 1056 * 1057 * Plugging coalesces IOs from the same issuer for the same purpose without 1058 * going through @q->queue_lock. As such it's more of an issuing mechanism 1059 * than scheduling, and the request, while may have elvpriv data, is not 1060 * added on the elevator at this point. In addition, we don't have 1061 * reliable access to the elevator outside queue lock. Only check basic 1062 * merging parameters without querying the elevator. 1063 * 1064 * Caller must ensure !blk_queue_nomerges(q) beforehand. 1065 */ 1066 bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio, 1067 unsigned int nr_segs) 1068 { 1069 struct blk_plug *plug; 1070 struct request *rq; 1071 1072 plug = blk_mq_plug(bio); 1073 if (!plug || rq_list_empty(plug->mq_list)) 1074 return false; 1075 1076 rq_list_for_each(&plug->mq_list, rq) { 1077 if (rq->q == q) { 1078 if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) == 1079 BIO_MERGE_OK) 1080 return true; 1081 break; 1082 } 1083 1084 /* 1085 * Only keep iterating plug list for merges if we have multiple 1086 * queues 1087 */ 1088 if (!plug->multiple_queues) 1089 break; 1090 } 1091 return false; 1092 } 1093 1094 /* 1095 * Iterate list of requests and see if we can merge this bio with any 1096 * of them. 1097 */ 1098 bool blk_bio_list_merge(struct request_queue *q, struct list_head *list, 1099 struct bio *bio, unsigned int nr_segs) 1100 { 1101 struct request *rq; 1102 int checked = 8; 1103 1104 list_for_each_entry_reverse(rq, list, queuelist) { 1105 if (!checked--) 1106 break; 1107 1108 switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) { 1109 case BIO_MERGE_NONE: 1110 continue; 1111 case BIO_MERGE_OK: 1112 return true; 1113 case BIO_MERGE_FAILED: 1114 return false; 1115 } 1116 1117 } 1118 1119 return false; 1120 } 1121 EXPORT_SYMBOL_GPL(blk_bio_list_merge); 1122 1123 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio, 1124 unsigned int nr_segs, struct request **merged_request) 1125 { 1126 struct request *rq; 1127 1128 switch (elv_merge(q, &rq, bio)) { 1129 case ELEVATOR_BACK_MERGE: 1130 if (!blk_mq_sched_allow_merge(q, rq, bio)) 1131 return false; 1132 if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK) 1133 return false; 1134 *merged_request = attempt_back_merge(q, rq); 1135 if (!*merged_request) 1136 elv_merged_request(q, rq, ELEVATOR_BACK_MERGE); 1137 return true; 1138 case ELEVATOR_FRONT_MERGE: 1139 if (!blk_mq_sched_allow_merge(q, rq, bio)) 1140 return false; 1141 if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK) 1142 return false; 1143 *merged_request = attempt_front_merge(q, rq); 1144 if (!*merged_request) 1145 elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE); 1146 return true; 1147 case ELEVATOR_DISCARD_MERGE: 1148 return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK; 1149 default: 1150 return false; 1151 } 1152 } 1153 EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge); 1154