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 static inline bool bio_will_gap(struct request_queue *q, 16 struct request *prev_rq, struct bio *prev, struct bio *next) 17 { 18 struct bio_vec pb, nb; 19 20 if (!bio_has_data(prev) || !queue_virt_boundary(q)) 21 return false; 22 23 /* 24 * Don't merge if the 1st bio starts with non-zero offset, otherwise it 25 * is quite difficult to respect the sg gap limit. We work hard to 26 * merge a huge number of small single bios in case of mkfs. 27 */ 28 if (prev_rq) 29 bio_get_first_bvec(prev_rq->bio, &pb); 30 else 31 bio_get_first_bvec(prev, &pb); 32 if (pb.bv_offset & queue_virt_boundary(q)) 33 return true; 34 35 /* 36 * We don't need to worry about the situation that the merged segment 37 * ends in unaligned virt boundary: 38 * 39 * - if 'pb' ends aligned, the merged segment ends aligned 40 * - if 'pb' ends unaligned, the next bio must include 41 * one single bvec of 'nb', otherwise the 'nb' can't 42 * merge with 'pb' 43 */ 44 bio_get_last_bvec(prev, &pb); 45 bio_get_first_bvec(next, &nb); 46 if (biovec_phys_mergeable(q, &pb, &nb)) 47 return false; 48 return __bvec_gap_to_prev(q, &pb, nb.bv_offset); 49 } 50 51 static inline bool req_gap_back_merge(struct request *req, struct bio *bio) 52 { 53 return bio_will_gap(req->q, req, req->biotail, bio); 54 } 55 56 static inline bool req_gap_front_merge(struct request *req, struct bio *bio) 57 { 58 return bio_will_gap(req->q, NULL, bio, req->bio); 59 } 60 61 static struct bio *blk_bio_discard_split(struct request_queue *q, 62 struct bio *bio, 63 struct bio_set *bs, 64 unsigned *nsegs) 65 { 66 unsigned int max_discard_sectors, granularity; 67 int alignment; 68 sector_t tmp; 69 unsigned split_sectors; 70 71 *nsegs = 1; 72 73 /* Zero-sector (unknown) and one-sector granularities are the same. */ 74 granularity = max(q->limits.discard_granularity >> 9, 1U); 75 76 max_discard_sectors = min(q->limits.max_discard_sectors, 77 bio_allowed_max_sectors(q)); 78 max_discard_sectors -= max_discard_sectors % granularity; 79 80 if (unlikely(!max_discard_sectors)) { 81 /* XXX: warn */ 82 return NULL; 83 } 84 85 if (bio_sectors(bio) <= max_discard_sectors) 86 return NULL; 87 88 split_sectors = max_discard_sectors; 89 90 /* 91 * If the next starting sector would be misaligned, stop the discard at 92 * the previous aligned sector. 93 */ 94 alignment = (q->limits.discard_alignment >> 9) % granularity; 95 96 tmp = bio->bi_iter.bi_sector + split_sectors - alignment; 97 tmp = sector_div(tmp, granularity); 98 99 if (split_sectors > tmp) 100 split_sectors -= tmp; 101 102 return bio_split(bio, split_sectors, GFP_NOIO, bs); 103 } 104 105 static struct bio *blk_bio_write_zeroes_split(struct request_queue *q, 106 struct bio *bio, struct bio_set *bs, unsigned *nsegs) 107 { 108 *nsegs = 0; 109 110 if (!q->limits.max_write_zeroes_sectors) 111 return NULL; 112 113 if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors) 114 return NULL; 115 116 return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs); 117 } 118 119 static struct bio *blk_bio_write_same_split(struct request_queue *q, 120 struct bio *bio, 121 struct bio_set *bs, 122 unsigned *nsegs) 123 { 124 *nsegs = 1; 125 126 if (!q->limits.max_write_same_sectors) 127 return NULL; 128 129 if (bio_sectors(bio) <= q->limits.max_write_same_sectors) 130 return NULL; 131 132 return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs); 133 } 134 135 /* 136 * Return the maximum number of sectors from the start of a bio that may be 137 * submitted as a single request to a block device. If enough sectors remain, 138 * align the end to the physical block size. Otherwise align the end to the 139 * logical block size. This approach minimizes the number of non-aligned 140 * requests that are submitted to a block device if the start of a bio is not 141 * aligned to a physical block boundary. 142 */ 143 static inline unsigned get_max_io_size(struct request_queue *q, 144 struct bio *bio) 145 { 146 unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector); 147 unsigned max_sectors = sectors; 148 unsigned pbs = queue_physical_block_size(q) >> SECTOR_SHIFT; 149 unsigned lbs = queue_logical_block_size(q) >> SECTOR_SHIFT; 150 unsigned start_offset = bio->bi_iter.bi_sector & (pbs - 1); 151 152 max_sectors += start_offset; 153 max_sectors &= ~(pbs - 1); 154 if (max_sectors > start_offset) 155 return max_sectors - start_offset; 156 157 return sectors & (lbs - 1); 158 } 159 160 static inline unsigned get_max_segment_size(const struct request_queue *q, 161 struct page *start_page, 162 unsigned long offset) 163 { 164 unsigned long mask = queue_segment_boundary(q); 165 166 offset = mask & (page_to_phys(start_page) + offset); 167 168 /* 169 * overflow may be triggered in case of zero page physical address 170 * on 32bit arch, use queue's max segment size when that happens. 171 */ 172 return min_not_zero(mask - offset + 1, 173 (unsigned long)queue_max_segment_size(q)); 174 } 175 176 /** 177 * bvec_split_segs - verify whether or not a bvec should be split in the middle 178 * @q: [in] request queue associated with the bio associated with @bv 179 * @bv: [in] bvec to examine 180 * @nsegs: [in,out] Number of segments in the bio being built. Incremented 181 * by the number of segments from @bv that may be appended to that 182 * bio without exceeding @max_segs 183 * @sectors: [in,out] Number of sectors in the bio being built. Incremented 184 * by the number of sectors from @bv that may be appended to that 185 * bio without exceeding @max_sectors 186 * @max_segs: [in] upper bound for *@nsegs 187 * @max_sectors: [in] upper bound for *@sectors 188 * 189 * When splitting a bio, it can happen that a bvec is encountered that is too 190 * big to fit in a single segment and hence that it has to be split in the 191 * middle. This function verifies whether or not that should happen. The value 192 * %true is returned if and only if appending the entire @bv to a bio with 193 * *@nsegs segments and *@sectors sectors would make that bio unacceptable for 194 * the block driver. 195 */ 196 static bool bvec_split_segs(const struct request_queue *q, 197 const struct bio_vec *bv, unsigned *nsegs, 198 unsigned *sectors, unsigned max_segs, 199 unsigned max_sectors) 200 { 201 unsigned max_len = (min(max_sectors, UINT_MAX >> 9) - *sectors) << 9; 202 unsigned len = min(bv->bv_len, max_len); 203 unsigned total_len = 0; 204 unsigned seg_size = 0; 205 206 while (len && *nsegs < max_segs) { 207 seg_size = get_max_segment_size(q, bv->bv_page, 208 bv->bv_offset + total_len); 209 seg_size = min(seg_size, len); 210 211 (*nsegs)++; 212 total_len += seg_size; 213 len -= seg_size; 214 215 if ((bv->bv_offset + total_len) & queue_virt_boundary(q)) 216 break; 217 } 218 219 *sectors += total_len >> 9; 220 221 /* tell the caller to split the bvec if it is too big to fit */ 222 return len > 0 || bv->bv_len > max_len; 223 } 224 225 /** 226 * blk_bio_segment_split - split a bio in two bios 227 * @q: [in] request queue pointer 228 * @bio: [in] bio to be split 229 * @bs: [in] bio set to allocate the clone from 230 * @segs: [out] number of segments in the bio with the first half of the sectors 231 * 232 * Clone @bio, update the bi_iter of the clone to represent the first sectors 233 * of @bio and update @bio->bi_iter to represent the remaining sectors. The 234 * following is guaranteed for the cloned bio: 235 * - That it has at most get_max_io_size(@q, @bio) sectors. 236 * - That it has at most queue_max_segments(@q) segments. 237 * 238 * Except for discard requests the cloned bio will point at the bi_io_vec of 239 * the original bio. It is the responsibility of the caller to ensure that the 240 * original bio is not freed before the cloned bio. The caller is also 241 * responsible for ensuring that @bs is only destroyed after processing of the 242 * split bio has finished. 243 */ 244 static struct bio *blk_bio_segment_split(struct request_queue *q, 245 struct bio *bio, 246 struct bio_set *bs, 247 unsigned *segs) 248 { 249 struct bio_vec bv, bvprv, *bvprvp = NULL; 250 struct bvec_iter iter; 251 unsigned nsegs = 0, sectors = 0; 252 const unsigned max_sectors = get_max_io_size(q, bio); 253 const unsigned max_segs = queue_max_segments(q); 254 255 bio_for_each_bvec(bv, bio, iter) { 256 /* 257 * If the queue doesn't support SG gaps and adding this 258 * offset would create a gap, disallow it. 259 */ 260 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset)) 261 goto split; 262 263 if (nsegs < max_segs && 264 sectors + (bv.bv_len >> 9) <= max_sectors && 265 bv.bv_offset + bv.bv_len <= PAGE_SIZE) { 266 nsegs++; 267 sectors += bv.bv_len >> 9; 268 } else if (bvec_split_segs(q, &bv, &nsegs, §ors, max_segs, 269 max_sectors)) { 270 goto split; 271 } 272 273 bvprv = bv; 274 bvprvp = &bvprv; 275 } 276 277 *segs = nsegs; 278 return NULL; 279 split: 280 *segs = nsegs; 281 return bio_split(bio, sectors, GFP_NOIO, bs); 282 } 283 284 /** 285 * __blk_queue_split - split a bio and submit the second half 286 * @q: [in] request queue pointer 287 * @bio: [in, out] bio to be split 288 * @nr_segs: [out] number of segments in the first bio 289 * 290 * Split a bio into two bios, chain the two bios, submit the second half and 291 * store a pointer to the first half in *@bio. If the second bio is still too 292 * big it will be split by a recursive call to this function. Since this 293 * function may allocate a new bio from @q->bio_split, it is the responsibility 294 * of the caller to ensure that @q is only released after processing of the 295 * split bio has finished. 296 */ 297 void __blk_queue_split(struct request_queue *q, struct bio **bio, 298 unsigned int *nr_segs) 299 { 300 struct bio *split = NULL; 301 302 switch (bio_op(*bio)) { 303 case REQ_OP_DISCARD: 304 case REQ_OP_SECURE_ERASE: 305 split = blk_bio_discard_split(q, *bio, &q->bio_split, nr_segs); 306 break; 307 case REQ_OP_WRITE_ZEROES: 308 split = blk_bio_write_zeroes_split(q, *bio, &q->bio_split, 309 nr_segs); 310 break; 311 case REQ_OP_WRITE_SAME: 312 split = blk_bio_write_same_split(q, *bio, &q->bio_split, 313 nr_segs); 314 break; 315 default: 316 /* 317 * All drivers must accept single-segments bios that are <= 318 * PAGE_SIZE. This is a quick and dirty check that relies on 319 * the fact that bi_io_vec[0] is always valid if a bio has data. 320 * The check might lead to occasional false negatives when bios 321 * are cloned, but compared to the performance impact of cloned 322 * bios themselves the loop below doesn't matter anyway. 323 */ 324 if (!q->limits.chunk_sectors && 325 (*bio)->bi_vcnt == 1 && 326 ((*bio)->bi_io_vec[0].bv_len + 327 (*bio)->bi_io_vec[0].bv_offset) <= PAGE_SIZE) { 328 *nr_segs = 1; 329 break; 330 } 331 split = blk_bio_segment_split(q, *bio, &q->bio_split, nr_segs); 332 break; 333 } 334 335 if (split) { 336 /* there isn't chance to merge the splitted bio */ 337 split->bi_opf |= REQ_NOMERGE; 338 339 /* 340 * Since we're recursing into make_request here, ensure 341 * that we mark this bio as already having entered the queue. 342 * If not, and the queue is going away, we can get stuck 343 * forever on waiting for the queue reference to drop. But 344 * that will never happen, as we're already holding a 345 * reference to it. 346 */ 347 bio_set_flag(*bio, BIO_QUEUE_ENTERED); 348 349 bio_chain(split, *bio); 350 trace_block_split(q, split, (*bio)->bi_iter.bi_sector); 351 generic_make_request(*bio); 352 *bio = split; 353 } 354 } 355 356 /** 357 * blk_queue_split - split a bio and submit the second half 358 * @q: [in] request queue pointer 359 * @bio: [in, out] bio to be split 360 * 361 * Split a bio into two bios, chains the two bios, submit the second half and 362 * store a pointer to the first half in *@bio. Since this function may allocate 363 * a new bio from @q->bio_split, it is the responsibility of the caller to 364 * ensure that @q is only released after processing of the split bio has 365 * finished. 366 */ 367 void blk_queue_split(struct request_queue *q, struct bio **bio) 368 { 369 unsigned int nr_segs; 370 371 __blk_queue_split(q, bio, &nr_segs); 372 } 373 EXPORT_SYMBOL(blk_queue_split); 374 375 unsigned int blk_recalc_rq_segments(struct request *rq) 376 { 377 unsigned int nr_phys_segs = 0; 378 unsigned int nr_sectors = 0; 379 struct req_iterator iter; 380 struct bio_vec bv; 381 382 if (!rq->bio) 383 return 0; 384 385 switch (bio_op(rq->bio)) { 386 case REQ_OP_DISCARD: 387 case REQ_OP_SECURE_ERASE: 388 case REQ_OP_WRITE_ZEROES: 389 return 0; 390 case REQ_OP_WRITE_SAME: 391 return 1; 392 } 393 394 rq_for_each_bvec(bv, rq, iter) 395 bvec_split_segs(rq->q, &bv, &nr_phys_segs, &nr_sectors, 396 UINT_MAX, UINT_MAX); 397 return nr_phys_segs; 398 } 399 400 static inline struct scatterlist *blk_next_sg(struct scatterlist **sg, 401 struct scatterlist *sglist) 402 { 403 if (!*sg) 404 return sglist; 405 406 /* 407 * If the driver previously mapped a shorter list, we could see a 408 * termination bit prematurely unless it fully inits the sg table 409 * on each mapping. We KNOW that there must be more entries here 410 * or the driver would be buggy, so force clear the termination bit 411 * to avoid doing a full sg_init_table() in drivers for each command. 412 */ 413 sg_unmark_end(*sg); 414 return sg_next(*sg); 415 } 416 417 static unsigned blk_bvec_map_sg(struct request_queue *q, 418 struct bio_vec *bvec, struct scatterlist *sglist, 419 struct scatterlist **sg) 420 { 421 unsigned nbytes = bvec->bv_len; 422 unsigned nsegs = 0, total = 0; 423 424 while (nbytes > 0) { 425 unsigned offset = bvec->bv_offset + total; 426 unsigned len = min(get_max_segment_size(q, bvec->bv_page, 427 offset), nbytes); 428 struct page *page = bvec->bv_page; 429 430 /* 431 * Unfortunately a fair number of drivers barf on scatterlists 432 * that have an offset larger than PAGE_SIZE, despite other 433 * subsystems dealing with that invariant just fine. For now 434 * stick to the legacy format where we never present those from 435 * the block layer, but the code below should be removed once 436 * these offenders (mostly MMC/SD drivers) are fixed. 437 */ 438 page += (offset >> PAGE_SHIFT); 439 offset &= ~PAGE_MASK; 440 441 *sg = blk_next_sg(sg, sglist); 442 sg_set_page(*sg, page, len, offset); 443 444 total += len; 445 nbytes -= len; 446 nsegs++; 447 } 448 449 return nsegs; 450 } 451 452 static inline int __blk_bvec_map_sg(struct bio_vec bv, 453 struct scatterlist *sglist, struct scatterlist **sg) 454 { 455 *sg = blk_next_sg(sg, sglist); 456 sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); 457 return 1; 458 } 459 460 /* only try to merge bvecs into one sg if they are from two bios */ 461 static inline bool 462 __blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec, 463 struct bio_vec *bvprv, struct scatterlist **sg) 464 { 465 466 int nbytes = bvec->bv_len; 467 468 if (!*sg) 469 return false; 470 471 if ((*sg)->length + nbytes > queue_max_segment_size(q)) 472 return false; 473 474 if (!biovec_phys_mergeable(q, bvprv, bvec)) 475 return false; 476 477 (*sg)->length += nbytes; 478 479 return true; 480 } 481 482 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 483 struct scatterlist *sglist, 484 struct scatterlist **sg) 485 { 486 struct bio_vec uninitialized_var(bvec), bvprv = { NULL }; 487 struct bvec_iter iter; 488 int nsegs = 0; 489 bool new_bio = false; 490 491 for_each_bio(bio) { 492 bio_for_each_bvec(bvec, bio, iter) { 493 /* 494 * Only try to merge bvecs from two bios given we 495 * have done bio internal merge when adding pages 496 * to bio 497 */ 498 if (new_bio && 499 __blk_segment_map_sg_merge(q, &bvec, &bvprv, sg)) 500 goto next_bvec; 501 502 if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE) 503 nsegs += __blk_bvec_map_sg(bvec, sglist, sg); 504 else 505 nsegs += blk_bvec_map_sg(q, &bvec, sglist, sg); 506 next_bvec: 507 new_bio = false; 508 } 509 if (likely(bio->bi_iter.bi_size)) { 510 bvprv = bvec; 511 new_bio = true; 512 } 513 } 514 515 return nsegs; 516 } 517 518 /* 519 * map a request to scatterlist, return number of sg entries setup. Caller 520 * must make sure sg can hold rq->nr_phys_segments entries 521 */ 522 int __blk_rq_map_sg(struct request_queue *q, struct request *rq, 523 struct scatterlist *sglist, struct scatterlist **last_sg) 524 { 525 int nsegs = 0; 526 527 if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) 528 nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, last_sg); 529 else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME) 530 nsegs = __blk_bvec_map_sg(bio_iovec(rq->bio), sglist, last_sg); 531 else if (rq->bio) 532 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg); 533 534 if (blk_rq_bytes(rq) && (blk_rq_bytes(rq) & q->dma_pad_mask)) { 535 unsigned int pad_len = 536 (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1; 537 538 (*last_sg)->length += pad_len; 539 rq->extra_len += pad_len; 540 } 541 542 if (q->dma_drain_size && q->dma_drain_needed(rq)) { 543 if (op_is_write(req_op(rq))) 544 memset(q->dma_drain_buffer, 0, q->dma_drain_size); 545 546 sg_unmark_end(*last_sg); 547 *last_sg = sg_next(*last_sg); 548 sg_set_page(*last_sg, virt_to_page(q->dma_drain_buffer), 549 q->dma_drain_size, 550 ((unsigned long)q->dma_drain_buffer) & 551 (PAGE_SIZE - 1)); 552 nsegs++; 553 rq->extra_len += q->dma_drain_size; 554 } 555 556 if (*last_sg) 557 sg_mark_end(*last_sg); 558 559 /* 560 * Something must have been wrong if the figured number of 561 * segment is bigger than number of req's physical segments 562 */ 563 WARN_ON(nsegs > blk_rq_nr_phys_segments(rq)); 564 565 return nsegs; 566 } 567 EXPORT_SYMBOL(__blk_rq_map_sg); 568 569 static inline int ll_new_hw_segment(struct request *req, struct bio *bio, 570 unsigned int nr_phys_segs) 571 { 572 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(req->q)) 573 goto no_merge; 574 575 if (blk_integrity_merge_bio(req->q, req, bio) == false) 576 goto no_merge; 577 578 /* 579 * This will form the start of a new hw segment. Bump both 580 * counters. 581 */ 582 req->nr_phys_segments += nr_phys_segs; 583 return 1; 584 585 no_merge: 586 req_set_nomerge(req->q, req); 587 return 0; 588 } 589 590 int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs) 591 { 592 if (req_gap_back_merge(req, bio)) 593 return 0; 594 if (blk_integrity_rq(req) && 595 integrity_req_gap_back_merge(req, bio)) 596 return 0; 597 if (blk_rq_sectors(req) + bio_sectors(bio) > 598 blk_rq_get_max_sectors(req, blk_rq_pos(req))) { 599 req_set_nomerge(req->q, req); 600 return 0; 601 } 602 603 return ll_new_hw_segment(req, bio, nr_segs); 604 } 605 606 int ll_front_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs) 607 { 608 if (req_gap_front_merge(req, bio)) 609 return 0; 610 if (blk_integrity_rq(req) && 611 integrity_req_gap_front_merge(req, bio)) 612 return 0; 613 if (blk_rq_sectors(req) + bio_sectors(bio) > 614 blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) { 615 req_set_nomerge(req->q, req); 616 return 0; 617 } 618 619 return ll_new_hw_segment(req, bio, nr_segs); 620 } 621 622 static bool req_attempt_discard_merge(struct request_queue *q, struct request *req, 623 struct request *next) 624 { 625 unsigned short segments = blk_rq_nr_discard_segments(req); 626 627 if (segments >= queue_max_discard_segments(q)) 628 goto no_merge; 629 if (blk_rq_sectors(req) + bio_sectors(next->bio) > 630 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 631 goto no_merge; 632 633 req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next); 634 return true; 635 no_merge: 636 req_set_nomerge(q, req); 637 return false; 638 } 639 640 static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 641 struct request *next) 642 { 643 int total_phys_segments; 644 645 if (req_gap_back_merge(req, next->bio)) 646 return 0; 647 648 /* 649 * Will it become too large? 650 */ 651 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 652 blk_rq_get_max_sectors(req, blk_rq_pos(req))) 653 return 0; 654 655 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 656 if (total_phys_segments > queue_max_segments(q)) 657 return 0; 658 659 if (blk_integrity_merge_rq(q, req, next) == false) 660 return 0; 661 662 /* Merge is OK... */ 663 req->nr_phys_segments = total_phys_segments; 664 return 1; 665 } 666 667 /** 668 * blk_rq_set_mixed_merge - mark a request as mixed merge 669 * @rq: request to mark as mixed merge 670 * 671 * Description: 672 * @rq is about to be mixed merged. Make sure the attributes 673 * which can be mixed are set in each bio and mark @rq as mixed 674 * merged. 675 */ 676 void blk_rq_set_mixed_merge(struct request *rq) 677 { 678 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; 679 struct bio *bio; 680 681 if (rq->rq_flags & RQF_MIXED_MERGE) 682 return; 683 684 /* 685 * @rq will no longer represent mixable attributes for all the 686 * contained bios. It will just track those of the first one. 687 * Distributes the attributs to each bio. 688 */ 689 for (bio = rq->bio; bio; bio = bio->bi_next) { 690 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) && 691 (bio->bi_opf & REQ_FAILFAST_MASK) != ff); 692 bio->bi_opf |= ff; 693 } 694 rq->rq_flags |= RQF_MIXED_MERGE; 695 } 696 697 static void blk_account_io_merge(struct request *req) 698 { 699 if (blk_do_io_stat(req)) { 700 struct hd_struct *part; 701 702 part_stat_lock(); 703 part = req->part; 704 705 part_dec_in_flight(req->q, part, rq_data_dir(req)); 706 707 hd_struct_put(part); 708 part_stat_unlock(); 709 } 710 } 711 /* 712 * Two cases of handling DISCARD merge: 713 * If max_discard_segments > 1, the driver takes every bio 714 * as a range and send them to controller together. The ranges 715 * needn't to be contiguous. 716 * Otherwise, the bios/requests will be handled as same as 717 * others which should be contiguous. 718 */ 719 static inline bool blk_discard_mergable(struct request *req) 720 { 721 if (req_op(req) == REQ_OP_DISCARD && 722 queue_max_discard_segments(req->q) > 1) 723 return true; 724 return false; 725 } 726 727 static enum elv_merge blk_try_req_merge(struct request *req, 728 struct request *next) 729 { 730 if (blk_discard_mergable(req)) 731 return ELEVATOR_DISCARD_MERGE; 732 else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) 733 return ELEVATOR_BACK_MERGE; 734 735 return ELEVATOR_NO_MERGE; 736 } 737 738 /* 739 * For non-mq, this has to be called with the request spinlock acquired. 740 * For mq with scheduling, the appropriate queue wide lock should be held. 741 */ 742 static struct request *attempt_merge(struct request_queue *q, 743 struct request *req, struct request *next) 744 { 745 if (!rq_mergeable(req) || !rq_mergeable(next)) 746 return NULL; 747 748 if (req_op(req) != req_op(next)) 749 return NULL; 750 751 if (rq_data_dir(req) != rq_data_dir(next) 752 || req->rq_disk != next->rq_disk) 753 return NULL; 754 755 if (req_op(req) == REQ_OP_WRITE_SAME && 756 !blk_write_same_mergeable(req->bio, next->bio)) 757 return NULL; 758 759 /* 760 * Don't allow merge of different write hints, or for a hint with 761 * non-hint IO. 762 */ 763 if (req->write_hint != next->write_hint) 764 return NULL; 765 766 if (req->ioprio != next->ioprio) 767 return NULL; 768 769 /* 770 * If we are allowed to merge, then append bio list 771 * from next to rq and release next. merge_requests_fn 772 * will have updated segment counts, update sector 773 * counts here. Handle DISCARDs separately, as they 774 * have separate settings. 775 */ 776 777 switch (blk_try_req_merge(req, next)) { 778 case ELEVATOR_DISCARD_MERGE: 779 if (!req_attempt_discard_merge(q, req, next)) 780 return NULL; 781 break; 782 case ELEVATOR_BACK_MERGE: 783 if (!ll_merge_requests_fn(q, req, next)) 784 return NULL; 785 break; 786 default: 787 return NULL; 788 } 789 790 /* 791 * If failfast settings disagree or any of the two is already 792 * a mixed merge, mark both as mixed before proceeding. This 793 * makes sure that all involved bios have mixable attributes 794 * set properly. 795 */ 796 if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || 797 (req->cmd_flags & REQ_FAILFAST_MASK) != 798 (next->cmd_flags & REQ_FAILFAST_MASK)) { 799 blk_rq_set_mixed_merge(req); 800 blk_rq_set_mixed_merge(next); 801 } 802 803 /* 804 * At this point we have either done a back merge or front merge. We 805 * need the smaller start_time_ns of the merged requests to be the 806 * current request for accounting purposes. 807 */ 808 if (next->start_time_ns < req->start_time_ns) 809 req->start_time_ns = next->start_time_ns; 810 811 req->biotail->bi_next = next->bio; 812 req->biotail = next->biotail; 813 814 req->__data_len += blk_rq_bytes(next); 815 816 if (!blk_discard_mergable(req)) 817 elv_merge_requests(q, req, next); 818 819 /* 820 * 'next' is going away, so update stats accordingly 821 */ 822 blk_account_io_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 struct request *attempt_back_merge(struct request_queue *q, struct request *rq) 833 { 834 struct request *next = elv_latter_request(q, rq); 835 836 if (next) 837 return attempt_merge(q, rq, next); 838 839 return NULL; 840 } 841 842 struct request *attempt_front_merge(struct request_queue *q, struct request *rq) 843 { 844 struct request *prev = elv_former_request(q, rq); 845 846 if (prev) 847 return attempt_merge(q, prev, rq); 848 849 return NULL; 850 } 851 852 int blk_attempt_req_merge(struct request_queue *q, struct request *rq, 853 struct request *next) 854 { 855 struct request *free; 856 857 free = attempt_merge(q, rq, next); 858 if (free) { 859 blk_put_request(free); 860 return 1; 861 } 862 863 return 0; 864 } 865 866 bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 867 { 868 if (!rq_mergeable(rq) || !bio_mergeable(bio)) 869 return false; 870 871 if (req_op(rq) != bio_op(bio)) 872 return false; 873 874 /* different data direction or already started, don't merge */ 875 if (bio_data_dir(bio) != rq_data_dir(rq)) 876 return false; 877 878 /* must be same device */ 879 if (rq->rq_disk != bio->bi_disk) 880 return false; 881 882 /* only merge integrity protected bio into ditto rq */ 883 if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 884 return false; 885 886 /* must be using the same buffer */ 887 if (req_op(rq) == REQ_OP_WRITE_SAME && 888 !blk_write_same_mergeable(rq->bio, bio)) 889 return false; 890 891 /* 892 * Don't allow merge of different write hints, or for a hint with 893 * non-hint IO. 894 */ 895 if (rq->write_hint != bio->bi_write_hint) 896 return false; 897 898 if (rq->ioprio != bio_prio(bio)) 899 return false; 900 901 return true; 902 } 903 904 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) 905 { 906 if (blk_discard_mergable(rq)) 907 return ELEVATOR_DISCARD_MERGE; 908 else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 909 return ELEVATOR_BACK_MERGE; 910 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 911 return ELEVATOR_FRONT_MERGE; 912 return ELEVATOR_NO_MERGE; 913 } 914