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, &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 static struct bio *blk_bio_discard_split(struct request_queue *q, 99 struct bio *bio, 100 struct bio_set *bs, 101 unsigned *nsegs) 102 { 103 unsigned int max_discard_sectors, granularity; 104 int alignment; 105 sector_t tmp; 106 unsigned split_sectors; 107 108 *nsegs = 1; 109 110 /* Zero-sector (unknown) and one-sector granularities are the same. */ 111 granularity = max(q->limits.discard_granularity >> 9, 1U); 112 113 max_discard_sectors = min(q->limits.max_discard_sectors, 114 bio_allowed_max_sectors(q)); 115 max_discard_sectors -= max_discard_sectors % granularity; 116 117 if (unlikely(!max_discard_sectors)) { 118 /* XXX: warn */ 119 return NULL; 120 } 121 122 if (bio_sectors(bio) <= max_discard_sectors) 123 return NULL; 124 125 split_sectors = max_discard_sectors; 126 127 /* 128 * If the next starting sector would be misaligned, stop the discard at 129 * the previous aligned sector. 130 */ 131 alignment = (q->limits.discard_alignment >> 9) % granularity; 132 133 tmp = bio->bi_iter.bi_sector + split_sectors - alignment; 134 tmp = sector_div(tmp, granularity); 135 136 if (split_sectors > tmp) 137 split_sectors -= tmp; 138 139 return bio_split(bio, split_sectors, GFP_NOIO, bs); 140 } 141 142 static struct bio *blk_bio_write_zeroes_split(struct request_queue *q, 143 struct bio *bio, struct bio_set *bs, unsigned *nsegs) 144 { 145 *nsegs = 0; 146 147 if (!q->limits.max_write_zeroes_sectors) 148 return NULL; 149 150 if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors) 151 return NULL; 152 153 return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs); 154 } 155 156 /* 157 * Return the maximum number of sectors from the start of a bio that may be 158 * submitted as a single request to a block device. If enough sectors remain, 159 * align the end to the physical block size. Otherwise align the end to the 160 * logical block size. This approach minimizes the number of non-aligned 161 * requests that are submitted to a block device if the start of a bio is not 162 * aligned to a physical block boundary. 163 */ 164 static inline unsigned get_max_io_size(struct request_queue *q, 165 struct bio *bio) 166 { 167 unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector, 0); 168 unsigned max_sectors = sectors; 169 unsigned pbs = queue_physical_block_size(q) >> SECTOR_SHIFT; 170 unsigned lbs = queue_logical_block_size(q) >> SECTOR_SHIFT; 171 unsigned start_offset = bio->bi_iter.bi_sector & (pbs - 1); 172 173 max_sectors += start_offset; 174 max_sectors &= ~(pbs - 1); 175 if (max_sectors > start_offset) 176 return max_sectors - start_offset; 177 178 return sectors & ~(lbs - 1); 179 } 180 181 static inline unsigned get_max_segment_size(const struct request_queue *q, 182 struct page *start_page, 183 unsigned long offset) 184 { 185 unsigned long mask = queue_segment_boundary(q); 186 187 offset = mask & (page_to_phys(start_page) + offset); 188 189 /* 190 * overflow may be triggered in case of zero page physical address 191 * on 32bit arch, use queue's max segment size when that happens. 192 */ 193 return min_not_zero(mask - offset + 1, 194 (unsigned long)queue_max_segment_size(q)); 195 } 196 197 /** 198 * bvec_split_segs - verify whether or not a bvec should be split in the middle 199 * @q: [in] request queue associated with the bio associated with @bv 200 * @bv: [in] bvec to examine 201 * @nsegs: [in,out] Number of segments in the bio being built. Incremented 202 * by the number of segments from @bv that may be appended to that 203 * bio without exceeding @max_segs 204 * @bytes: [in,out] Number of bytes in the bio being built. Incremented 205 * by the number of bytes from @bv that may be appended to that 206 * bio without exceeding @max_bytes 207 * @max_segs: [in] upper bound for *@nsegs 208 * @max_bytes: [in] upper bound for *@bytes 209 * 210 * When splitting a bio, it can happen that a bvec is encountered that is too 211 * big to fit in a single segment and hence that it has to be split in the 212 * middle. This function verifies whether or not that should happen. The value 213 * %true is returned if and only if appending the entire @bv to a bio with 214 * *@nsegs segments and *@sectors sectors would make that bio unacceptable for 215 * the block driver. 216 */ 217 static bool bvec_split_segs(const struct request_queue *q, 218 const struct bio_vec *bv, unsigned *nsegs, 219 unsigned *bytes, unsigned max_segs, 220 unsigned max_bytes) 221 { 222 unsigned max_len = min(max_bytes, UINT_MAX) - *bytes; 223 unsigned len = min(bv->bv_len, max_len); 224 unsigned total_len = 0; 225 unsigned seg_size = 0; 226 227 while (len && *nsegs < max_segs) { 228 seg_size = get_max_segment_size(q, bv->bv_page, 229 bv->bv_offset + total_len); 230 seg_size = min(seg_size, len); 231 232 (*nsegs)++; 233 total_len += seg_size; 234 len -= seg_size; 235 236 if ((bv->bv_offset + total_len) & queue_virt_boundary(q)) 237 break; 238 } 239 240 *bytes += total_len; 241 242 /* tell the caller to split the bvec if it is too big to fit */ 243 return len > 0 || bv->bv_len > max_len; 244 } 245 246 /** 247 * blk_bio_segment_split - split a bio in two bios 248 * @q: [in] request queue pointer 249 * @bio: [in] bio to be split 250 * @bs: [in] bio set to allocate the clone from 251 * @segs: [out] number of segments in the bio with the first half of the sectors 252 * 253 * Clone @bio, update the bi_iter of the clone to represent the first sectors 254 * of @bio and update @bio->bi_iter to represent the remaining sectors. The 255 * following is guaranteed for the cloned bio: 256 * - That it has at most get_max_io_size(@q, @bio) sectors. 257 * - That it has at most queue_max_segments(@q) segments. 258 * 259 * Except for discard requests the cloned bio will point at the bi_io_vec of 260 * the original bio. It is the responsibility of the caller to ensure that the 261 * original bio is not freed before the cloned bio. The caller is also 262 * responsible for ensuring that @bs is only destroyed after processing of the 263 * split bio has finished. 264 */ 265 static struct bio *blk_bio_segment_split(struct request_queue *q, 266 struct bio *bio, 267 struct bio_set *bs, 268 unsigned *segs) 269 { 270 struct bio_vec bv, bvprv, *bvprvp = NULL; 271 struct bvec_iter iter; 272 unsigned nsegs = 0, bytes = 0; 273 const unsigned max_bytes = get_max_io_size(q, bio) << 9; 274 const unsigned max_segs = queue_max_segments(q); 275 276 bio_for_each_bvec(bv, bio, iter) { 277 /* 278 * If the queue doesn't support SG gaps and adding this 279 * offset would create a gap, disallow it. 280 */ 281 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset)) 282 goto split; 283 284 if (nsegs < max_segs && 285 bytes + bv.bv_len <= max_bytes && 286 bv.bv_offset + bv.bv_len <= PAGE_SIZE) { 287 nsegs++; 288 bytes += bv.bv_len; 289 } else if (bvec_split_segs(q, &bv, &nsegs, &bytes, max_segs, 290 max_bytes)) { 291 goto split; 292 } 293 294 bvprv = bv; 295 bvprvp = &bvprv; 296 } 297 298 *segs = nsegs; 299 return NULL; 300 split: 301 *segs = nsegs; 302 303 /* 304 * Individual bvecs might not be logical block aligned. Round down the 305 * split size so that each bio is properly block size aligned, even if 306 * we do not use the full hardware limits. 307 */ 308 bytes = ALIGN_DOWN(bytes, queue_logical_block_size(q)); 309 310 /* 311 * Bio splitting may cause subtle trouble such as hang when doing sync 312 * iopoll in direct IO routine. Given performance gain of iopoll for 313 * big IO can be trival, disable iopoll when split needed. 314 */ 315 bio_clear_polled(bio); 316 return bio_split(bio, bytes >> SECTOR_SHIFT, GFP_NOIO, bs); 317 } 318 319 /** 320 * __blk_queue_split - split a bio and submit the second half 321 * @q: [in] request_queue new bio is being queued at 322 * @bio: [in, out] bio to be split 323 * @nr_segs: [out] number of segments in the first bio 324 * 325 * Split a bio into two bios, chain the two bios, submit the second half and 326 * store a pointer to the first half in *@bio. If the second bio is still too 327 * big it will be split by a recursive call to this function. Since this 328 * function may allocate a new bio from q->bio_split, it is the responsibility 329 * of the caller to ensure that q->bio_split is only released after processing 330 * of the split bio has finished. 331 */ 332 void __blk_queue_split(struct request_queue *q, struct bio **bio, 333 unsigned int *nr_segs) 334 { 335 struct bio *split = NULL; 336 337 switch (bio_op(*bio)) { 338 case REQ_OP_DISCARD: 339 case REQ_OP_SECURE_ERASE: 340 split = blk_bio_discard_split(q, *bio, &q->bio_split, nr_segs); 341 break; 342 case REQ_OP_WRITE_ZEROES: 343 split = blk_bio_write_zeroes_split(q, *bio, &q->bio_split, 344 nr_segs); 345 break; 346 default: 347 split = blk_bio_segment_split(q, *bio, &q->bio_split, nr_segs); 348 break; 349 } 350 351 if (split) { 352 /* there isn't chance to merge the splitted bio */ 353 split->bi_opf |= REQ_NOMERGE; 354 355 bio_chain(split, *bio); 356 trace_block_split(split, (*bio)->bi_iter.bi_sector); 357 submit_bio_noacct(*bio); 358 *bio = split; 359 } 360 } 361 362 /** 363 * blk_queue_split - split a bio and submit the second half 364 * @bio: [in, out] bio to be split 365 * 366 * Split a bio into two bios, chains the two bios, submit the second half and 367 * store a pointer to the first half in *@bio. Since this function may allocate 368 * a new bio from q->bio_split, it is the responsibility of the caller to ensure 369 * that q->bio_split is only released after processing of the split bio has 370 * finished. 371 */ 372 void blk_queue_split(struct bio **bio) 373 { 374 struct request_queue *q = bdev_get_queue((*bio)->bi_bdev); 375 unsigned int nr_segs; 376 377 if (blk_may_split(q, *bio)) 378 __blk_queue_split(q, bio, &nr_segs); 379 } 380 EXPORT_SYMBOL(blk_queue_split); 381 382 unsigned int blk_recalc_rq_segments(struct request *rq) 383 { 384 unsigned int nr_phys_segs = 0; 385 unsigned int bytes = 0; 386 struct req_iterator iter; 387 struct bio_vec bv; 388 389 if (!rq->bio) 390 return 0; 391 392 switch (bio_op(rq->bio)) { 393 case REQ_OP_DISCARD: 394 case REQ_OP_SECURE_ERASE: 395 if (queue_max_discard_segments(rq->q) > 1) { 396 struct bio *bio = rq->bio; 397 398 for_each_bio(bio) 399 nr_phys_segs++; 400 return nr_phys_segs; 401 } 402 return 1; 403 case REQ_OP_WRITE_ZEROES: 404 return 0; 405 } 406 407 rq_for_each_bvec(bv, rq, iter) 408 bvec_split_segs(rq->q, &bv, &nr_phys_segs, &bytes, 409 UINT_MAX, UINT_MAX); 410 return nr_phys_segs; 411 } 412 413 static inline struct scatterlist *blk_next_sg(struct scatterlist **sg, 414 struct scatterlist *sglist) 415 { 416 if (!*sg) 417 return sglist; 418 419 /* 420 * If the driver previously mapped a shorter list, we could see a 421 * termination bit prematurely unless it fully inits the sg table 422 * on each mapping. We KNOW that there must be more entries here 423 * or the driver would be buggy, so force clear the termination bit 424 * to avoid doing a full sg_init_table() in drivers for each command. 425 */ 426 sg_unmark_end(*sg); 427 return sg_next(*sg); 428 } 429 430 static unsigned blk_bvec_map_sg(struct request_queue *q, 431 struct bio_vec *bvec, struct scatterlist *sglist, 432 struct scatterlist **sg) 433 { 434 unsigned nbytes = bvec->bv_len; 435 unsigned nsegs = 0, total = 0; 436 437 while (nbytes > 0) { 438 unsigned offset = bvec->bv_offset + total; 439 unsigned len = min(get_max_segment_size(q, bvec->bv_page, 440 offset), nbytes); 441 struct page *page = bvec->bv_page; 442 443 /* 444 * Unfortunately a fair number of drivers barf on scatterlists 445 * that have an offset larger than PAGE_SIZE, despite other 446 * subsystems dealing with that invariant just fine. For now 447 * stick to the legacy format where we never present those from 448 * the block layer, but the code below should be removed once 449 * these offenders (mostly MMC/SD drivers) are fixed. 450 */ 451 page += (offset >> PAGE_SHIFT); 452 offset &= ~PAGE_MASK; 453 454 *sg = blk_next_sg(sg, sglist); 455 sg_set_page(*sg, page, len, offset); 456 457 total += len; 458 nbytes -= len; 459 nsegs++; 460 } 461 462 return nsegs; 463 } 464 465 static inline int __blk_bvec_map_sg(struct bio_vec bv, 466 struct scatterlist *sglist, struct scatterlist **sg) 467 { 468 *sg = blk_next_sg(sg, sglist); 469 sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); 470 return 1; 471 } 472 473 /* only try to merge bvecs into one sg if they are from two bios */ 474 static inline bool 475 __blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec, 476 struct bio_vec *bvprv, struct scatterlist **sg) 477 { 478 479 int nbytes = bvec->bv_len; 480 481 if (!*sg) 482 return false; 483 484 if ((*sg)->length + nbytes > queue_max_segment_size(q)) 485 return false; 486 487 if (!biovec_phys_mergeable(q, bvprv, bvec)) 488 return false; 489 490 (*sg)->length += nbytes; 491 492 return true; 493 } 494 495 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 496 struct scatterlist *sglist, 497 struct scatterlist **sg) 498 { 499 struct bio_vec bvec, bvprv = { NULL }; 500 struct bvec_iter iter; 501 int nsegs = 0; 502 bool new_bio = false; 503 504 for_each_bio(bio) { 505 bio_for_each_bvec(bvec, bio, iter) { 506 /* 507 * Only try to merge bvecs from two bios given we 508 * have done bio internal merge when adding pages 509 * to bio 510 */ 511 if (new_bio && 512 __blk_segment_map_sg_merge(q, &bvec, &bvprv, sg)) 513 goto next_bvec; 514 515 if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE) 516 nsegs += __blk_bvec_map_sg(bvec, sglist, sg); 517 else 518 nsegs += blk_bvec_map_sg(q, &bvec, sglist, sg); 519 next_bvec: 520 new_bio = false; 521 } 522 if (likely(bio->bi_iter.bi_size)) { 523 bvprv = bvec; 524 new_bio = true; 525 } 526 } 527 528 return nsegs; 529 } 530 531 /* 532 * map a request to scatterlist, return number of sg entries setup. Caller 533 * must make sure sg can hold rq->nr_phys_segments entries 534 */ 535 int __blk_rq_map_sg(struct request_queue *q, struct request *rq, 536 struct scatterlist *sglist, struct scatterlist **last_sg) 537 { 538 int nsegs = 0; 539 540 if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) 541 nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, last_sg); 542 else if (rq->bio) 543 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg); 544 545 if (*last_sg) 546 sg_mark_end(*last_sg); 547 548 /* 549 * Something must have been wrong if the figured number of 550 * segment is bigger than number of req's physical segments 551 */ 552 WARN_ON(nsegs > blk_rq_nr_phys_segments(rq)); 553 554 return nsegs; 555 } 556 EXPORT_SYMBOL(__blk_rq_map_sg); 557 558 static inline unsigned int blk_rq_get_max_segments(struct request *rq) 559 { 560 if (req_op(rq) == REQ_OP_DISCARD) 561 return queue_max_discard_segments(rq->q); 562 return queue_max_segments(rq->q); 563 } 564 565 static inline unsigned int blk_rq_get_max_sectors(struct request *rq, 566 sector_t offset) 567 { 568 struct request_queue *q = rq->q; 569 570 if (blk_rq_is_passthrough(rq)) 571 return q->limits.max_hw_sectors; 572 573 if (!q->limits.chunk_sectors || 574 req_op(rq) == REQ_OP_DISCARD || 575 req_op(rq) == REQ_OP_SECURE_ERASE) 576 return blk_queue_get_max_sectors(q, req_op(rq)); 577 578 return min(blk_max_size_offset(q, offset, 0), 579 blk_queue_get_max_sectors(q, req_op(rq))); 580 } 581 582 static inline int ll_new_hw_segment(struct request *req, struct bio *bio, 583 unsigned int nr_phys_segs) 584 { 585 if (!blk_cgroup_mergeable(req, bio)) 586 goto no_merge; 587 588 if (blk_integrity_merge_bio(req->q, req, bio) == false) 589 goto no_merge; 590 591 /* discard request merge won't add new segment */ 592 if (req_op(req) == REQ_OP_DISCARD) 593 return 1; 594 595 if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req)) 596 goto no_merge; 597 598 /* 599 * This will form the start of a new hw segment. Bump both 600 * counters. 601 */ 602 req->nr_phys_segments += nr_phys_segs; 603 return 1; 604 605 no_merge: 606 req_set_nomerge(req->q, req); 607 return 0; 608 } 609 610 int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs) 611 { 612 if (req_gap_back_merge(req, bio)) 613 return 0; 614 if (blk_integrity_rq(req) && 615 integrity_req_gap_back_merge(req, bio)) 616 return 0; 617 if (!bio_crypt_ctx_back_mergeable(req, bio)) 618 return 0; 619 if (blk_rq_sectors(req) + bio_sectors(bio) > 620 blk_rq_get_max_sectors(req, blk_rq_pos(req))) { 621 req_set_nomerge(req->q, req); 622 return 0; 623 } 624 625 return ll_new_hw_segment(req, bio, nr_segs); 626 } 627 628 static int ll_front_merge_fn(struct request *req, struct bio *bio, 629 unsigned int nr_segs) 630 { 631 if (req_gap_front_merge(req, bio)) 632 return 0; 633 if (blk_integrity_rq(req) && 634 integrity_req_gap_front_merge(req, bio)) 635 return 0; 636 if (!bio_crypt_ctx_front_mergeable(req, bio)) 637 return 0; 638 if (blk_rq_sectors(req) + bio_sectors(bio) > 639 blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { 640 req_set_nomerge(req->q, req); 641 return 0; 642 } 643 644 return ll_new_hw_segment(req, bio, nr_segs); 645 } 646 647 static bool req_attempt_discard_merge(struct request_queue *q, struct request *req, 648 struct request *next) 649 { 650 unsigned short segments = blk_rq_nr_discard_segments(req); 651 652 if (segments >= queue_max_discard_segments(q)) 653 goto no_merge; 654 if (blk_rq_sectors(req) + bio_sectors(next->bio) > 655 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 656 goto no_merge; 657 658 req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next); 659 return true; 660 no_merge: 661 req_set_nomerge(q, req); 662 return false; 663 } 664 665 static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 666 struct request *next) 667 { 668 int total_phys_segments; 669 670 if (req_gap_back_merge(req, next->bio)) 671 return 0; 672 673 /* 674 * Will it become too large? 675 */ 676 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 677 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 678 return 0; 679 680 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 681 if (total_phys_segments > blk_rq_get_max_segments(req)) 682 return 0; 683 684 if (!blk_cgroup_mergeable(req, next->bio)) 685 return 0; 686 687 if (blk_integrity_merge_rq(q, req, next) == false) 688 return 0; 689 690 if (!bio_crypt_ctx_merge_rq(req, next)) 691 return 0; 692 693 /* Merge is OK... */ 694 req->nr_phys_segments = total_phys_segments; 695 return 1; 696 } 697 698 /** 699 * blk_rq_set_mixed_merge - mark a request as mixed merge 700 * @rq: request to mark as mixed merge 701 * 702 * Description: 703 * @rq is about to be mixed merged. Make sure the attributes 704 * which can be mixed are set in each bio and mark @rq as mixed 705 * merged. 706 */ 707 void blk_rq_set_mixed_merge(struct request *rq) 708 { 709 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; 710 struct bio *bio; 711 712 if (rq->rq_flags & RQF_MIXED_MERGE) 713 return; 714 715 /* 716 * @rq will no longer represent mixable attributes for all the 717 * contained bios. It will just track those of the first one. 718 * Distributes the attributs to each bio. 719 */ 720 for (bio = rq->bio; bio; bio = bio->bi_next) { 721 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 722 (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 723 bio->bi_opf |= ff; 724 } 725 rq->rq_flags |= RQF_MIXED_MERGE; 726 } 727 728 static void blk_account_io_merge_request(struct request *req) 729 { 730 if (blk_do_io_stat(req)) { 731 part_stat_lock(); 732 part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); 733 part_stat_unlock(); 734 } 735 } 736 737 static enum elv_merge blk_try_req_merge(struct request *req, 738 struct request *next) 739 { 740 if (blk_discard_mergable(req)) 741 return ELEVATOR_DISCARD_MERGE; 742 else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) 743 return ELEVATOR_BACK_MERGE; 744 745 return ELEVATOR_NO_MERGE; 746 } 747 748 /* 749 * For non-mq, this has to be called with the request spinlock acquired. 750 * For mq with scheduling, the appropriate queue wide lock should be held. 751 */ 752 static struct request *attempt_merge(struct request_queue *q, 753 struct request *req, struct request *next) 754 { 755 if (!rq_mergeable(req) || !rq_mergeable(next)) 756 return NULL; 757 758 if (req_op(req) != req_op(next)) 759 return NULL; 760 761 if (rq_data_dir(req) != rq_data_dir(next)) 762 return NULL; 763 764 if (req->ioprio != next->ioprio) 765 return NULL; 766 767 /* 768 * If we are allowed to merge, then append bio list 769 * from next to rq and release next. merge_requests_fn 770 * will have updated segment counts, update sector 771 * counts here. Handle DISCARDs separately, as they 772 * have separate settings. 773 */ 774 775 switch (blk_try_req_merge(req, next)) { 776 case ELEVATOR_DISCARD_MERGE: 777 if (!req_attempt_discard_merge(q, req, next)) 778 return NULL; 779 break; 780 case ELEVATOR_BACK_MERGE: 781 if (!ll_merge_requests_fn(q, req, next)) 782 return NULL; 783 break; 784 default: 785 return NULL; 786 } 787 788 /* 789 * If failfast settings disagree or any of the two is already 790 * a mixed merge, mark both as mixed before proceeding. This 791 * makes sure that all involved bios have mixable attributes 792 * set properly. 793 */ 794 if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || 795 (req->cmd_flags & REQ_FAILFAST_MASK) != 796 (next->cmd_flags & REQ_FAILFAST_MASK)) { 797 blk_rq_set_mixed_merge(req); 798 blk_rq_set_mixed_merge(next); 799 } 800 801 /* 802 * At this point we have either done a back merge or front merge. We 803 * need the smaller start_time_ns of the merged requests to be the 804 * current request for accounting purposes. 805 */ 806 if (next->start_time_ns < req->start_time_ns) 807 req->start_time_ns = next->start_time_ns; 808 809 req->biotail->bi_next = next->bio; 810 req->biotail = next->biotail; 811 812 req->__data_len += blk_rq_bytes(next); 813 814 if (!blk_discard_mergable(req)) 815 elv_merge_requests(q, req, next); 816 817 /* 818 * 'next' is going away, so update stats accordingly 819 */ 820 blk_account_io_merge_request(next); 821 822 trace_block_rq_merge(next); 823 824 /* 825 * ownership of bio passed from next to req, return 'next' for 826 * the caller to free 827 */ 828 next->bio = NULL; 829 return next; 830 } 831 832 static struct request *attempt_back_merge(struct request_queue *q, 833 struct request *rq) 834 { 835 struct request *next = elv_latter_request(q, rq); 836 837 if (next) 838 return attempt_merge(q, rq, next); 839 840 return NULL; 841 } 842 843 static struct request *attempt_front_merge(struct request_queue *q, 844 struct request *rq) 845 { 846 struct request *prev = elv_former_request(q, rq); 847 848 if (prev) 849 return attempt_merge(q, prev, rq); 850 851 return NULL; 852 } 853 854 /* 855 * Try to merge 'next' into 'rq'. Return true if the merge happened, false 856 * otherwise. The caller is responsible for freeing 'next' if the merge 857 * happened. 858 */ 859 bool blk_attempt_req_merge(struct request_queue *q, struct request *rq, 860 struct request *next) 861 { 862 return attempt_merge(q, rq, next); 863 } 864 865 bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 866 { 867 if (!rq_mergeable(rq) || !bio_mergeable(bio)) 868 return false; 869 870 if (req_op(rq) != bio_op(bio)) 871 return false; 872 873 /* different data direction or already started, don't merge */ 874 if (bio_data_dir(bio) != rq_data_dir(rq)) 875 return false; 876 877 /* don't merge across cgroup boundaries */ 878 if (!blk_cgroup_mergeable(rq, bio)) 879 return false; 880 881 /* only merge integrity protected bio into ditto rq */ 882 if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 883 return false; 884 885 /* Only merge if the crypt contexts are compatible */ 886 if (!bio_crypt_rq_ctx_compatible(rq, bio)) 887 return false; 888 889 if (rq->ioprio != bio_prio(bio)) 890 return false; 891 892 return true; 893 } 894 895 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) 896 { 897 if (blk_discard_mergable(rq)) 898 return ELEVATOR_DISCARD_MERGE; 899 else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 900 return ELEVATOR_BACK_MERGE; 901 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 902 return ELEVATOR_FRONT_MERGE; 903 return ELEVATOR_NO_MERGE; 904 } 905 906 static void blk_account_io_merge_bio(struct request *req) 907 { 908 if (!blk_do_io_stat(req)) 909 return; 910 911 part_stat_lock(); 912 part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); 913 part_stat_unlock(); 914 } 915 916 enum bio_merge_status { 917 BIO_MERGE_OK, 918 BIO_MERGE_NONE, 919 BIO_MERGE_FAILED, 920 }; 921 922 static enum bio_merge_status bio_attempt_back_merge(struct request *req, 923 struct bio *bio, unsigned int nr_segs) 924 { 925 const int ff = bio->bi_opf & REQ_FAILFAST_MASK; 926 927 if (!ll_back_merge_fn(req, bio, nr_segs)) 928 return BIO_MERGE_FAILED; 929 930 trace_block_bio_backmerge(bio); 931 rq_qos_merge(req->q, req, bio); 932 933 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) 934 blk_rq_set_mixed_merge(req); 935 936 req->biotail->bi_next = bio; 937 req->biotail = bio; 938 req->__data_len += bio->bi_iter.bi_size; 939 940 bio_crypt_free_ctx(bio); 941 942 blk_account_io_merge_bio(req); 943 return BIO_MERGE_OK; 944 } 945 946 static enum bio_merge_status bio_attempt_front_merge(struct request *req, 947 struct bio *bio, unsigned int nr_segs) 948 { 949 const int ff = bio->bi_opf & REQ_FAILFAST_MASK; 950 951 if (!ll_front_merge_fn(req, bio, nr_segs)) 952 return BIO_MERGE_FAILED; 953 954 trace_block_bio_frontmerge(bio); 955 rq_qos_merge(req->q, req, bio); 956 957 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) 958 blk_rq_set_mixed_merge(req); 959 960 bio->bi_next = req->bio; 961 req->bio = bio; 962 963 req->__sector = bio->bi_iter.bi_sector; 964 req->__data_len += bio->bi_iter.bi_size; 965 966 bio_crypt_do_front_merge(req, bio); 967 968 blk_account_io_merge_bio(req); 969 return BIO_MERGE_OK; 970 } 971 972 static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q, 973 struct request *req, struct bio *bio) 974 { 975 unsigned short segments = blk_rq_nr_discard_segments(req); 976 977 if (segments >= queue_max_discard_segments(q)) 978 goto no_merge; 979 if (blk_rq_sectors(req) + bio_sectors(bio) > 980 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 981 goto no_merge; 982 983 rq_qos_merge(q, req, bio); 984 985 req->biotail->bi_next = bio; 986 req->biotail = bio; 987 req->__data_len += bio->bi_iter.bi_size; 988 req->nr_phys_segments = segments + 1; 989 990 blk_account_io_merge_bio(req); 991 return BIO_MERGE_OK; 992 no_merge: 993 req_set_nomerge(q, req); 994 return BIO_MERGE_FAILED; 995 } 996 997 static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q, 998 struct request *rq, 999 struct bio *bio, 1000 unsigned int nr_segs, 1001 bool sched_allow_merge) 1002 { 1003 if (!blk_rq_merge_ok(rq, bio)) 1004 return BIO_MERGE_NONE; 1005 1006 switch (blk_try_merge(rq, bio)) { 1007 case ELEVATOR_BACK_MERGE: 1008 if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) 1009 return bio_attempt_back_merge(rq, bio, nr_segs); 1010 break; 1011 case ELEVATOR_FRONT_MERGE: 1012 if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) 1013 return bio_attempt_front_merge(rq, bio, nr_segs); 1014 break; 1015 case ELEVATOR_DISCARD_MERGE: 1016 return bio_attempt_discard_merge(q, rq, bio); 1017 default: 1018 return BIO_MERGE_NONE; 1019 } 1020 1021 return BIO_MERGE_FAILED; 1022 } 1023 1024 /** 1025 * blk_attempt_plug_merge - try to merge with %current's plugged list 1026 * @q: request_queue new bio is being queued at 1027 * @bio: new bio being queued 1028 * @nr_segs: number of segments in @bio 1029 * from the passed in @q already in the plug list 1030 * 1031 * Determine whether @bio being queued on @q can be merged with the previous 1032 * request on %current's plugged list. Returns %true if merge was successful, 1033 * otherwise %false. 1034 * 1035 * Plugging coalesces IOs from the same issuer for the same purpose without 1036 * going through @q->queue_lock. As such it's more of an issuing mechanism 1037 * than scheduling, and the request, while may have elvpriv data, is not 1038 * added on the elevator at this point. In addition, we don't have 1039 * reliable access to the elevator outside queue lock. Only check basic 1040 * merging parameters without querying the elevator. 1041 * 1042 * Caller must ensure !blk_queue_nomerges(q) beforehand. 1043 */ 1044 bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio, 1045 unsigned int nr_segs) 1046 { 1047 struct blk_plug *plug; 1048 struct request *rq; 1049 1050 plug = blk_mq_plug(q, bio); 1051 if (!plug || rq_list_empty(plug->mq_list)) 1052 return false; 1053 1054 rq_list_for_each(&plug->mq_list, rq) { 1055 if (rq->q == q) { 1056 if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) == 1057 BIO_MERGE_OK) 1058 return true; 1059 break; 1060 } 1061 1062 /* 1063 * Only keep iterating plug list for merges if we have multiple 1064 * queues 1065 */ 1066 if (!plug->multiple_queues) 1067 break; 1068 } 1069 return false; 1070 } 1071 1072 /* 1073 * Iterate list of requests and see if we can merge this bio with any 1074 * of them. 1075 */ 1076 bool blk_bio_list_merge(struct request_queue *q, struct list_head *list, 1077 struct bio *bio, unsigned int nr_segs) 1078 { 1079 struct request *rq; 1080 int checked = 8; 1081 1082 list_for_each_entry_reverse(rq, list, queuelist) { 1083 if (!checked--) 1084 break; 1085 1086 switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) { 1087 case BIO_MERGE_NONE: 1088 continue; 1089 case BIO_MERGE_OK: 1090 return true; 1091 case BIO_MERGE_FAILED: 1092 return false; 1093 } 1094 1095 } 1096 1097 return false; 1098 } 1099 EXPORT_SYMBOL_GPL(blk_bio_list_merge); 1100 1101 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio, 1102 unsigned int nr_segs, struct request **merged_request) 1103 { 1104 struct request *rq; 1105 1106 switch (elv_merge(q, &rq, bio)) { 1107 case ELEVATOR_BACK_MERGE: 1108 if (!blk_mq_sched_allow_merge(q, rq, bio)) 1109 return false; 1110 if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK) 1111 return false; 1112 *merged_request = attempt_back_merge(q, rq); 1113 if (!*merged_request) 1114 elv_merged_request(q, rq, ELEVATOR_BACK_MERGE); 1115 return true; 1116 case ELEVATOR_FRONT_MERGE: 1117 if (!blk_mq_sched_allow_merge(q, rq, bio)) 1118 return false; 1119 if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK) 1120 return false; 1121 *merged_request = attempt_front_merge(q, rq); 1122 if (!*merged_request) 1123 elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE); 1124 return true; 1125 case ELEVATOR_DISCARD_MERGE: 1126 return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK; 1127 default: 1128 return false; 1129 } 1130 } 1131 EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge); 1132