1 /* 2 * Functions related to segment and merge handling 3 */ 4 #include <linux/kernel.h> 5 #include <linux/module.h> 6 #include <linux/bio.h> 7 #include <linux/blkdev.h> 8 #include <linux/scatterlist.h> 9 10 #include "blk.h" 11 12 static unsigned int __blk_recalc_rq_segments(struct request_queue *q, 13 struct bio *bio, 14 bool no_sg_merge) 15 { 16 struct bio_vec bv, bvprv = { NULL }; 17 int cluster, high, highprv = 1; 18 unsigned int seg_size, nr_phys_segs; 19 struct bio *fbio, *bbio; 20 struct bvec_iter iter; 21 22 if (!bio) 23 return 0; 24 25 /* 26 * This should probably be returning 0, but blk_add_request_payload() 27 * (Christoph!!!!) 28 */ 29 if (bio->bi_rw & REQ_DISCARD) 30 return 1; 31 32 if (bio->bi_rw & REQ_WRITE_SAME) 33 return 1; 34 35 fbio = bio; 36 cluster = blk_queue_cluster(q); 37 seg_size = 0; 38 nr_phys_segs = 0; 39 high = 0; 40 for_each_bio(bio) { 41 bio_for_each_segment(bv, bio, iter) { 42 /* 43 * If SG merging is disabled, each bio vector is 44 * a segment 45 */ 46 if (no_sg_merge) 47 goto new_segment; 48 49 /* 50 * the trick here is making sure that a high page is 51 * never considered part of another segment, since 52 * that might change with the bounce page. 53 */ 54 high = page_to_pfn(bv.bv_page) > queue_bounce_pfn(q); 55 if (!high && !highprv && cluster) { 56 if (seg_size + bv.bv_len 57 > queue_max_segment_size(q)) 58 goto new_segment; 59 if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv)) 60 goto new_segment; 61 if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv)) 62 goto new_segment; 63 64 seg_size += bv.bv_len; 65 bvprv = bv; 66 continue; 67 } 68 new_segment: 69 if (nr_phys_segs == 1 && seg_size > 70 fbio->bi_seg_front_size) 71 fbio->bi_seg_front_size = seg_size; 72 73 nr_phys_segs++; 74 bvprv = bv; 75 seg_size = bv.bv_len; 76 highprv = high; 77 } 78 bbio = bio; 79 } 80 81 if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size) 82 fbio->bi_seg_front_size = seg_size; 83 if (seg_size > bbio->bi_seg_back_size) 84 bbio->bi_seg_back_size = seg_size; 85 86 return nr_phys_segs; 87 } 88 89 void blk_recalc_rq_segments(struct request *rq) 90 { 91 bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE, 92 &rq->q->queue_flags); 93 94 rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio, 95 no_sg_merge); 96 } 97 98 void blk_recount_segments(struct request_queue *q, struct bio *bio) 99 { 100 unsigned short seg_cnt; 101 102 /* estimate segment number by bi_vcnt for non-cloned bio */ 103 if (bio_flagged(bio, BIO_CLONED)) 104 seg_cnt = bio_segments(bio); 105 else 106 seg_cnt = bio->bi_vcnt; 107 108 if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) && 109 (seg_cnt < queue_max_segments(q))) 110 bio->bi_phys_segments = seg_cnt; 111 else { 112 struct bio *nxt = bio->bi_next; 113 114 bio->bi_next = NULL; 115 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false); 116 bio->bi_next = nxt; 117 } 118 119 bio->bi_flags |= (1 << BIO_SEG_VALID); 120 } 121 EXPORT_SYMBOL(blk_recount_segments); 122 123 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, 124 struct bio *nxt) 125 { 126 struct bio_vec end_bv = { NULL }, nxt_bv; 127 struct bvec_iter iter; 128 129 if (!blk_queue_cluster(q)) 130 return 0; 131 132 if (bio->bi_seg_back_size + nxt->bi_seg_front_size > 133 queue_max_segment_size(q)) 134 return 0; 135 136 if (!bio_has_data(bio)) 137 return 1; 138 139 bio_for_each_segment(end_bv, bio, iter) 140 if (end_bv.bv_len == iter.bi_size) 141 break; 142 143 nxt_bv = bio_iovec(nxt); 144 145 if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv)) 146 return 0; 147 148 /* 149 * bio and nxt are contiguous in memory; check if the queue allows 150 * these two to be merged into one 151 */ 152 if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv)) 153 return 1; 154 155 return 0; 156 } 157 158 static inline void 159 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, 160 struct scatterlist *sglist, struct bio_vec *bvprv, 161 struct scatterlist **sg, int *nsegs, int *cluster) 162 { 163 164 int nbytes = bvec->bv_len; 165 166 if (*sg && *cluster) { 167 if ((*sg)->length + nbytes > queue_max_segment_size(q)) 168 goto new_segment; 169 170 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) 171 goto new_segment; 172 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) 173 goto new_segment; 174 175 (*sg)->length += nbytes; 176 } else { 177 new_segment: 178 if (!*sg) 179 *sg = sglist; 180 else { 181 /* 182 * If the driver previously mapped a shorter 183 * list, we could see a termination bit 184 * prematurely unless it fully inits the sg 185 * table on each mapping. We KNOW that there 186 * must be more entries here or the driver 187 * would be buggy, so force clear the 188 * termination bit to avoid doing a full 189 * sg_init_table() in drivers for each command. 190 */ 191 sg_unmark_end(*sg); 192 *sg = sg_next(*sg); 193 } 194 195 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); 196 (*nsegs)++; 197 } 198 *bvprv = *bvec; 199 } 200 201 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 202 struct scatterlist *sglist, 203 struct scatterlist **sg) 204 { 205 struct bio_vec bvec, bvprv = { NULL }; 206 struct bvec_iter iter; 207 int nsegs, cluster; 208 209 nsegs = 0; 210 cluster = blk_queue_cluster(q); 211 212 if (bio->bi_rw & REQ_DISCARD) { 213 /* 214 * This is a hack - drivers should be neither modifying the 215 * biovec, nor relying on bi_vcnt - but because of 216 * blk_add_request_payload(), a discard bio may or may not have 217 * a payload we need to set up here (thank you Christoph) and 218 * bi_vcnt is really the only way of telling if we need to. 219 */ 220 221 if (bio->bi_vcnt) 222 goto single_segment; 223 224 return 0; 225 } 226 227 if (bio->bi_rw & REQ_WRITE_SAME) { 228 single_segment: 229 *sg = sglist; 230 bvec = bio_iovec(bio); 231 sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset); 232 return 1; 233 } 234 235 for_each_bio(bio) 236 bio_for_each_segment(bvec, bio, iter) 237 __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg, 238 &nsegs, &cluster); 239 240 return nsegs; 241 } 242 243 /* 244 * map a request to scatterlist, return number of sg entries setup. Caller 245 * must make sure sg can hold rq->nr_phys_segments entries 246 */ 247 int blk_rq_map_sg(struct request_queue *q, struct request *rq, 248 struct scatterlist *sglist) 249 { 250 struct scatterlist *sg = NULL; 251 int nsegs = 0; 252 253 if (rq->bio) 254 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg); 255 256 if (unlikely(rq->cmd_flags & REQ_COPY_USER) && 257 (blk_rq_bytes(rq) & q->dma_pad_mask)) { 258 unsigned int pad_len = 259 (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1; 260 261 sg->length += pad_len; 262 rq->extra_len += pad_len; 263 } 264 265 if (q->dma_drain_size && q->dma_drain_needed(rq)) { 266 if (rq->cmd_flags & REQ_WRITE) 267 memset(q->dma_drain_buffer, 0, q->dma_drain_size); 268 269 sg->page_link &= ~0x02; 270 sg = sg_next(sg); 271 sg_set_page(sg, virt_to_page(q->dma_drain_buffer), 272 q->dma_drain_size, 273 ((unsigned long)q->dma_drain_buffer) & 274 (PAGE_SIZE - 1)); 275 nsegs++; 276 rq->extra_len += q->dma_drain_size; 277 } 278 279 if (sg) 280 sg_mark_end(sg); 281 282 return nsegs; 283 } 284 EXPORT_SYMBOL(blk_rq_map_sg); 285 286 static inline int ll_new_hw_segment(struct request_queue *q, 287 struct request *req, 288 struct bio *bio) 289 { 290 int nr_phys_segs = bio_phys_segments(q, bio); 291 292 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) 293 goto no_merge; 294 295 if (blk_integrity_merge_bio(q, req, bio) == false) 296 goto no_merge; 297 298 /* 299 * This will form the start of a new hw segment. Bump both 300 * counters. 301 */ 302 req->nr_phys_segments += nr_phys_segs; 303 return 1; 304 305 no_merge: 306 req->cmd_flags |= REQ_NOMERGE; 307 if (req == q->last_merge) 308 q->last_merge = NULL; 309 return 0; 310 } 311 312 int ll_back_merge_fn(struct request_queue *q, struct request *req, 313 struct bio *bio) 314 { 315 if (blk_rq_sectors(req) + bio_sectors(bio) > 316 blk_rq_get_max_sectors(req)) { 317 req->cmd_flags |= REQ_NOMERGE; 318 if (req == q->last_merge) 319 q->last_merge = NULL; 320 return 0; 321 } 322 if (!bio_flagged(req->biotail, BIO_SEG_VALID)) 323 blk_recount_segments(q, req->biotail); 324 if (!bio_flagged(bio, BIO_SEG_VALID)) 325 blk_recount_segments(q, bio); 326 327 return ll_new_hw_segment(q, req, bio); 328 } 329 330 int ll_front_merge_fn(struct request_queue *q, struct request *req, 331 struct bio *bio) 332 { 333 if (blk_rq_sectors(req) + bio_sectors(bio) > 334 blk_rq_get_max_sectors(req)) { 335 req->cmd_flags |= REQ_NOMERGE; 336 if (req == q->last_merge) 337 q->last_merge = NULL; 338 return 0; 339 } 340 if (!bio_flagged(bio, BIO_SEG_VALID)) 341 blk_recount_segments(q, bio); 342 if (!bio_flagged(req->bio, BIO_SEG_VALID)) 343 blk_recount_segments(q, req->bio); 344 345 return ll_new_hw_segment(q, req, bio); 346 } 347 348 /* 349 * blk-mq uses req->special to carry normal driver per-request payload, it 350 * does not indicate a prepared command that we cannot merge with. 351 */ 352 static bool req_no_special_merge(struct request *req) 353 { 354 struct request_queue *q = req->q; 355 356 return !q->mq_ops && req->special; 357 } 358 359 static int req_gap_to_prev(struct request *req, struct request *next) 360 { 361 struct bio *prev = req->biotail; 362 363 return bvec_gap_to_prev(&prev->bi_io_vec[prev->bi_vcnt - 1], 364 next->bio->bi_io_vec[0].bv_offset); 365 } 366 367 static int ll_merge_requests_fn(struct request_queue *q, struct request *req, 368 struct request *next) 369 { 370 int total_phys_segments; 371 unsigned int seg_size = 372 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size; 373 374 /* 375 * First check if the either of the requests are re-queued 376 * requests. Can't merge them if they are. 377 */ 378 if (req_no_special_merge(req) || req_no_special_merge(next)) 379 return 0; 380 381 if (test_bit(QUEUE_FLAG_SG_GAPS, &q->queue_flags) && 382 req_gap_to_prev(req, next)) 383 return 0; 384 385 /* 386 * Will it become too large? 387 */ 388 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > 389 blk_rq_get_max_sectors(req)) 390 return 0; 391 392 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; 393 if (blk_phys_contig_segment(q, req->biotail, next->bio)) { 394 if (req->nr_phys_segments == 1) 395 req->bio->bi_seg_front_size = seg_size; 396 if (next->nr_phys_segments == 1) 397 next->biotail->bi_seg_back_size = seg_size; 398 total_phys_segments--; 399 } 400 401 if (total_phys_segments > queue_max_segments(q)) 402 return 0; 403 404 if (blk_integrity_merge_rq(q, req, next) == false) 405 return 0; 406 407 /* Merge is OK... */ 408 req->nr_phys_segments = total_phys_segments; 409 return 1; 410 } 411 412 /** 413 * blk_rq_set_mixed_merge - mark a request as mixed merge 414 * @rq: request to mark as mixed merge 415 * 416 * Description: 417 * @rq is about to be mixed merged. Make sure the attributes 418 * which can be mixed are set in each bio and mark @rq as mixed 419 * merged. 420 */ 421 void blk_rq_set_mixed_merge(struct request *rq) 422 { 423 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; 424 struct bio *bio; 425 426 if (rq->cmd_flags & REQ_MIXED_MERGE) 427 return; 428 429 /* 430 * @rq will no longer represent mixable attributes for all the 431 * contained bios. It will just track those of the first one. 432 * Distributes the attributs to each bio. 433 */ 434 for (bio = rq->bio; bio; bio = bio->bi_next) { 435 WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) && 436 (bio->bi_rw & REQ_FAILFAST_MASK) != ff); 437 bio->bi_rw |= ff; 438 } 439 rq->cmd_flags |= REQ_MIXED_MERGE; 440 } 441 442 static void blk_account_io_merge(struct request *req) 443 { 444 if (blk_do_io_stat(req)) { 445 struct hd_struct *part; 446 int cpu; 447 448 cpu = part_stat_lock(); 449 part = req->part; 450 451 part_round_stats(cpu, part); 452 part_dec_in_flight(part, rq_data_dir(req)); 453 454 hd_struct_put(part); 455 part_stat_unlock(); 456 } 457 } 458 459 /* 460 * Has to be called with the request spinlock acquired 461 */ 462 static int attempt_merge(struct request_queue *q, struct request *req, 463 struct request *next) 464 { 465 if (!rq_mergeable(req) || !rq_mergeable(next)) 466 return 0; 467 468 if (!blk_check_merge_flags(req->cmd_flags, next->cmd_flags)) 469 return 0; 470 471 /* 472 * not contiguous 473 */ 474 if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)) 475 return 0; 476 477 if (rq_data_dir(req) != rq_data_dir(next) 478 || req->rq_disk != next->rq_disk 479 || req_no_special_merge(next)) 480 return 0; 481 482 if (req->cmd_flags & REQ_WRITE_SAME && 483 !blk_write_same_mergeable(req->bio, next->bio)) 484 return 0; 485 486 /* 487 * If we are allowed to merge, then append bio list 488 * from next to rq and release next. merge_requests_fn 489 * will have updated segment counts, update sector 490 * counts here. 491 */ 492 if (!ll_merge_requests_fn(q, req, next)) 493 return 0; 494 495 /* 496 * If failfast settings disagree or any of the two is already 497 * a mixed merge, mark both as mixed before proceeding. This 498 * makes sure that all involved bios have mixable attributes 499 * set properly. 500 */ 501 if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE || 502 (req->cmd_flags & REQ_FAILFAST_MASK) != 503 (next->cmd_flags & REQ_FAILFAST_MASK)) { 504 blk_rq_set_mixed_merge(req); 505 blk_rq_set_mixed_merge(next); 506 } 507 508 /* 509 * At this point we have either done a back merge 510 * or front merge. We need the smaller start_time of 511 * the merged requests to be the current request 512 * for accounting purposes. 513 */ 514 if (time_after(req->start_time, next->start_time)) 515 req->start_time = next->start_time; 516 517 req->biotail->bi_next = next->bio; 518 req->biotail = next->biotail; 519 520 req->__data_len += blk_rq_bytes(next); 521 522 elv_merge_requests(q, req, next); 523 524 /* 525 * 'next' is going away, so update stats accordingly 526 */ 527 blk_account_io_merge(next); 528 529 req->ioprio = ioprio_best(req->ioprio, next->ioprio); 530 if (blk_rq_cpu_valid(next)) 531 req->cpu = next->cpu; 532 533 /* owner-ship of bio passed from next to req */ 534 next->bio = NULL; 535 __blk_put_request(q, next); 536 return 1; 537 } 538 539 int attempt_back_merge(struct request_queue *q, struct request *rq) 540 { 541 struct request *next = elv_latter_request(q, rq); 542 543 if (next) 544 return attempt_merge(q, rq, next); 545 546 return 0; 547 } 548 549 int attempt_front_merge(struct request_queue *q, struct request *rq) 550 { 551 struct request *prev = elv_former_request(q, rq); 552 553 if (prev) 554 return attempt_merge(q, prev, rq); 555 556 return 0; 557 } 558 559 int blk_attempt_req_merge(struct request_queue *q, struct request *rq, 560 struct request *next) 561 { 562 return attempt_merge(q, rq, next); 563 } 564 565 bool blk_rq_merge_ok(struct request *rq, struct bio *bio) 566 { 567 struct request_queue *q = rq->q; 568 569 if (!rq_mergeable(rq) || !bio_mergeable(bio)) 570 return false; 571 572 if (!blk_check_merge_flags(rq->cmd_flags, bio->bi_rw)) 573 return false; 574 575 /* different data direction or already started, don't merge */ 576 if (bio_data_dir(bio) != rq_data_dir(rq)) 577 return false; 578 579 /* must be same device and not a special request */ 580 if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq)) 581 return false; 582 583 /* only merge integrity protected bio into ditto rq */ 584 if (blk_integrity_merge_bio(rq->q, rq, bio) == false) 585 return false; 586 587 /* must be using the same buffer */ 588 if (rq->cmd_flags & REQ_WRITE_SAME && 589 !blk_write_same_mergeable(rq->bio, bio)) 590 return false; 591 592 if (q->queue_flags & (1 << QUEUE_FLAG_SG_GAPS)) { 593 struct bio_vec *bprev; 594 595 bprev = &rq->biotail->bi_io_vec[rq->biotail->bi_vcnt - 1]; 596 if (bvec_gap_to_prev(bprev, bio->bi_io_vec[0].bv_offset)) 597 return false; 598 } 599 600 return true; 601 } 602 603 int blk_try_merge(struct request *rq, struct bio *bio) 604 { 605 if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) 606 return ELEVATOR_BACK_MERGE; 607 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) 608 return ELEVATOR_FRONT_MERGE; 609 return ELEVATOR_NO_MERGE; 610 } 611