1 /* 2 * Block device elevator/IO-scheduler. 3 * 4 * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE 5 * 6 * 30042000 Jens Axboe <axboe@kernel.dk> : 7 * 8 * Split the elevator a bit so that it is possible to choose a different 9 * one or even write a new "plug in". There are three pieces: 10 * - elevator_fn, inserts a new request in the queue list 11 * - elevator_merge_fn, decides whether a new buffer can be merged with 12 * an existing request 13 * - elevator_dequeue_fn, called when a request is taken off the active list 14 * 15 * 20082000 Dave Jones <davej@suse.de> : 16 * Removed tests for max-bomb-segments, which was breaking elvtune 17 * when run without -bN 18 * 19 * Jens: 20 * - Rework again to work with bio instead of buffer_heads 21 * - loose bi_dev comparisons, partition handling is right now 22 * - completely modularize elevator setup and teardown 23 * 24 */ 25 #include <linux/kernel.h> 26 #include <linux/fs.h> 27 #include <linux/blkdev.h> 28 #include <linux/elevator.h> 29 #include <linux/bio.h> 30 #include <linux/module.h> 31 #include <linux/slab.h> 32 #include <linux/init.h> 33 #include <linux/compiler.h> 34 #include <linux/delay.h> 35 #include <linux/blktrace_api.h> 36 #include <linux/hash.h> 37 #include <linux/uaccess.h> 38 39 #include <trace/events/block.h> 40 41 #include "blk.h" 42 43 static DEFINE_SPINLOCK(elv_list_lock); 44 static LIST_HEAD(elv_list); 45 46 /* 47 * Merge hash stuff. 48 */ 49 static const int elv_hash_shift = 6; 50 #define ELV_HASH_BLOCK(sec) ((sec) >> 3) 51 #define ELV_HASH_FN(sec) \ 52 (hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift)) 53 #define ELV_HASH_ENTRIES (1 << elv_hash_shift) 54 #define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq)) 55 56 /* 57 * Query io scheduler to see if the current process issuing bio may be 58 * merged with rq. 59 */ 60 static int elv_iosched_allow_merge(struct request *rq, struct bio *bio) 61 { 62 struct request_queue *q = rq->q; 63 struct elevator_queue *e = q->elevator; 64 65 if (e->ops->elevator_allow_merge_fn) 66 return e->ops->elevator_allow_merge_fn(q, rq, bio); 67 68 return 1; 69 } 70 71 /* 72 * can we safely merge with this request? 73 */ 74 int elv_rq_merge_ok(struct request *rq, struct bio *bio) 75 { 76 if (!rq_mergeable(rq)) 77 return 0; 78 79 /* 80 * Don't merge file system requests and discard requests 81 */ 82 if ((bio->bi_rw & REQ_DISCARD) != (rq->bio->bi_rw & REQ_DISCARD)) 83 return 0; 84 85 /* 86 * Don't merge discard requests and secure discard requests 87 */ 88 if ((bio->bi_rw & REQ_SECURE) != (rq->bio->bi_rw & REQ_SECURE)) 89 return 0; 90 91 /* 92 * different data direction or already started, don't merge 93 */ 94 if (bio_data_dir(bio) != rq_data_dir(rq)) 95 return 0; 96 97 /* 98 * must be same device and not a special request 99 */ 100 if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special) 101 return 0; 102 103 /* 104 * only merge integrity protected bio into ditto rq 105 */ 106 if (bio_integrity(bio) != blk_integrity_rq(rq)) 107 return 0; 108 109 if (!elv_iosched_allow_merge(rq, bio)) 110 return 0; 111 112 return 1; 113 } 114 EXPORT_SYMBOL(elv_rq_merge_ok); 115 116 int elv_try_merge(struct request *__rq, struct bio *bio) 117 { 118 int ret = ELEVATOR_NO_MERGE; 119 120 /* 121 * we can merge and sequence is ok, check if it's possible 122 */ 123 if (elv_rq_merge_ok(__rq, bio)) { 124 if (blk_rq_pos(__rq) + blk_rq_sectors(__rq) == bio->bi_sector) 125 ret = ELEVATOR_BACK_MERGE; 126 else if (blk_rq_pos(__rq) - bio_sectors(bio) == bio->bi_sector) 127 ret = ELEVATOR_FRONT_MERGE; 128 } 129 130 return ret; 131 } 132 133 static struct elevator_type *elevator_find(const char *name) 134 { 135 struct elevator_type *e; 136 137 list_for_each_entry(e, &elv_list, list) { 138 if (!strcmp(e->elevator_name, name)) 139 return e; 140 } 141 142 return NULL; 143 } 144 145 static void elevator_put(struct elevator_type *e) 146 { 147 module_put(e->elevator_owner); 148 } 149 150 static struct elevator_type *elevator_get(const char *name) 151 { 152 struct elevator_type *e; 153 154 spin_lock(&elv_list_lock); 155 156 e = elevator_find(name); 157 if (!e) { 158 spin_unlock(&elv_list_lock); 159 request_module("%s-iosched", name); 160 spin_lock(&elv_list_lock); 161 e = elevator_find(name); 162 } 163 164 if (e && !try_module_get(e->elevator_owner)) 165 e = NULL; 166 167 spin_unlock(&elv_list_lock); 168 169 return e; 170 } 171 172 static void *elevator_init_queue(struct request_queue *q, 173 struct elevator_queue *eq) 174 { 175 return eq->ops->elevator_init_fn(q); 176 } 177 178 static void elevator_attach(struct request_queue *q, struct elevator_queue *eq, 179 void *data) 180 { 181 q->elevator = eq; 182 eq->elevator_data = data; 183 } 184 185 static char chosen_elevator[16]; 186 187 static int __init elevator_setup(char *str) 188 { 189 /* 190 * Be backwards-compatible with previous kernels, so users 191 * won't get the wrong elevator. 192 */ 193 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1); 194 return 1; 195 } 196 197 __setup("elevator=", elevator_setup); 198 199 static struct kobj_type elv_ktype; 200 201 static struct elevator_queue *elevator_alloc(struct request_queue *q, 202 struct elevator_type *e) 203 { 204 struct elevator_queue *eq; 205 int i; 206 207 eq = kmalloc_node(sizeof(*eq), GFP_KERNEL | __GFP_ZERO, q->node); 208 if (unlikely(!eq)) 209 goto err; 210 211 eq->ops = &e->ops; 212 eq->elevator_type = e; 213 kobject_init(&eq->kobj, &elv_ktype); 214 mutex_init(&eq->sysfs_lock); 215 216 eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES, 217 GFP_KERNEL, q->node); 218 if (!eq->hash) 219 goto err; 220 221 for (i = 0; i < ELV_HASH_ENTRIES; i++) 222 INIT_HLIST_HEAD(&eq->hash[i]); 223 224 return eq; 225 err: 226 kfree(eq); 227 elevator_put(e); 228 return NULL; 229 } 230 231 static void elevator_release(struct kobject *kobj) 232 { 233 struct elevator_queue *e; 234 235 e = container_of(kobj, struct elevator_queue, kobj); 236 elevator_put(e->elevator_type); 237 kfree(e->hash); 238 kfree(e); 239 } 240 241 int elevator_init(struct request_queue *q, char *name) 242 { 243 struct elevator_type *e = NULL; 244 struct elevator_queue *eq; 245 void *data; 246 247 if (unlikely(q->elevator)) 248 return 0; 249 250 INIT_LIST_HEAD(&q->queue_head); 251 q->last_merge = NULL; 252 q->end_sector = 0; 253 q->boundary_rq = NULL; 254 255 if (name) { 256 e = elevator_get(name); 257 if (!e) 258 return -EINVAL; 259 } 260 261 if (!e && *chosen_elevator) { 262 e = elevator_get(chosen_elevator); 263 if (!e) 264 printk(KERN_ERR "I/O scheduler %s not found\n", 265 chosen_elevator); 266 } 267 268 if (!e) { 269 e = elevator_get(CONFIG_DEFAULT_IOSCHED); 270 if (!e) { 271 printk(KERN_ERR 272 "Default I/O scheduler not found. " \ 273 "Using noop.\n"); 274 e = elevator_get("noop"); 275 } 276 } 277 278 eq = elevator_alloc(q, e); 279 if (!eq) 280 return -ENOMEM; 281 282 data = elevator_init_queue(q, eq); 283 if (!data) { 284 kobject_put(&eq->kobj); 285 return -ENOMEM; 286 } 287 288 elevator_attach(q, eq, data); 289 return 0; 290 } 291 EXPORT_SYMBOL(elevator_init); 292 293 void elevator_exit(struct elevator_queue *e) 294 { 295 mutex_lock(&e->sysfs_lock); 296 if (e->ops->elevator_exit_fn) 297 e->ops->elevator_exit_fn(e); 298 e->ops = NULL; 299 mutex_unlock(&e->sysfs_lock); 300 301 kobject_put(&e->kobj); 302 } 303 EXPORT_SYMBOL(elevator_exit); 304 305 static inline void __elv_rqhash_del(struct request *rq) 306 { 307 hlist_del_init(&rq->hash); 308 } 309 310 static void elv_rqhash_del(struct request_queue *q, struct request *rq) 311 { 312 if (ELV_ON_HASH(rq)) 313 __elv_rqhash_del(rq); 314 } 315 316 static void elv_rqhash_add(struct request_queue *q, struct request *rq) 317 { 318 struct elevator_queue *e = q->elevator; 319 320 BUG_ON(ELV_ON_HASH(rq)); 321 hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]); 322 } 323 324 static void elv_rqhash_reposition(struct request_queue *q, struct request *rq) 325 { 326 __elv_rqhash_del(rq); 327 elv_rqhash_add(q, rq); 328 } 329 330 static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset) 331 { 332 struct elevator_queue *e = q->elevator; 333 struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)]; 334 struct hlist_node *entry, *next; 335 struct request *rq; 336 337 hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) { 338 BUG_ON(!ELV_ON_HASH(rq)); 339 340 if (unlikely(!rq_mergeable(rq))) { 341 __elv_rqhash_del(rq); 342 continue; 343 } 344 345 if (rq_hash_key(rq) == offset) 346 return rq; 347 } 348 349 return NULL; 350 } 351 352 /* 353 * RB-tree support functions for inserting/lookup/removal of requests 354 * in a sorted RB tree. 355 */ 356 struct request *elv_rb_add(struct rb_root *root, struct request *rq) 357 { 358 struct rb_node **p = &root->rb_node; 359 struct rb_node *parent = NULL; 360 struct request *__rq; 361 362 while (*p) { 363 parent = *p; 364 __rq = rb_entry(parent, struct request, rb_node); 365 366 if (blk_rq_pos(rq) < blk_rq_pos(__rq)) 367 p = &(*p)->rb_left; 368 else if (blk_rq_pos(rq) > blk_rq_pos(__rq)) 369 p = &(*p)->rb_right; 370 else 371 return __rq; 372 } 373 374 rb_link_node(&rq->rb_node, parent, p); 375 rb_insert_color(&rq->rb_node, root); 376 return NULL; 377 } 378 EXPORT_SYMBOL(elv_rb_add); 379 380 void elv_rb_del(struct rb_root *root, struct request *rq) 381 { 382 BUG_ON(RB_EMPTY_NODE(&rq->rb_node)); 383 rb_erase(&rq->rb_node, root); 384 RB_CLEAR_NODE(&rq->rb_node); 385 } 386 EXPORT_SYMBOL(elv_rb_del); 387 388 struct request *elv_rb_find(struct rb_root *root, sector_t sector) 389 { 390 struct rb_node *n = root->rb_node; 391 struct request *rq; 392 393 while (n) { 394 rq = rb_entry(n, struct request, rb_node); 395 396 if (sector < blk_rq_pos(rq)) 397 n = n->rb_left; 398 else if (sector > blk_rq_pos(rq)) 399 n = n->rb_right; 400 else 401 return rq; 402 } 403 404 return NULL; 405 } 406 EXPORT_SYMBOL(elv_rb_find); 407 408 /* 409 * Insert rq into dispatch queue of q. Queue lock must be held on 410 * entry. rq is sort instead into the dispatch queue. To be used by 411 * specific elevators. 412 */ 413 void elv_dispatch_sort(struct request_queue *q, struct request *rq) 414 { 415 sector_t boundary; 416 struct list_head *entry; 417 int stop_flags; 418 419 if (q->last_merge == rq) 420 q->last_merge = NULL; 421 422 elv_rqhash_del(q, rq); 423 424 q->nr_sorted--; 425 426 boundary = q->end_sector; 427 stop_flags = REQ_SOFTBARRIER | REQ_STARTED; 428 list_for_each_prev(entry, &q->queue_head) { 429 struct request *pos = list_entry_rq(entry); 430 431 if ((rq->cmd_flags & REQ_DISCARD) != 432 (pos->cmd_flags & REQ_DISCARD)) 433 break; 434 if (rq_data_dir(rq) != rq_data_dir(pos)) 435 break; 436 if (pos->cmd_flags & stop_flags) 437 break; 438 if (blk_rq_pos(rq) >= boundary) { 439 if (blk_rq_pos(pos) < boundary) 440 continue; 441 } else { 442 if (blk_rq_pos(pos) >= boundary) 443 break; 444 } 445 if (blk_rq_pos(rq) >= blk_rq_pos(pos)) 446 break; 447 } 448 449 list_add(&rq->queuelist, entry); 450 } 451 EXPORT_SYMBOL(elv_dispatch_sort); 452 453 /* 454 * Insert rq into dispatch queue of q. Queue lock must be held on 455 * entry. rq is added to the back of the dispatch queue. To be used by 456 * specific elevators. 457 */ 458 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq) 459 { 460 if (q->last_merge == rq) 461 q->last_merge = NULL; 462 463 elv_rqhash_del(q, rq); 464 465 q->nr_sorted--; 466 467 q->end_sector = rq_end_sector(rq); 468 q->boundary_rq = rq; 469 list_add_tail(&rq->queuelist, &q->queue_head); 470 } 471 EXPORT_SYMBOL(elv_dispatch_add_tail); 472 473 int elv_merge(struct request_queue *q, struct request **req, struct bio *bio) 474 { 475 struct elevator_queue *e = q->elevator; 476 struct request *__rq; 477 int ret; 478 479 /* 480 * Levels of merges: 481 * nomerges: No merges at all attempted 482 * noxmerges: Only simple one-hit cache try 483 * merges: All merge tries attempted 484 */ 485 if (blk_queue_nomerges(q)) 486 return ELEVATOR_NO_MERGE; 487 488 /* 489 * First try one-hit cache. 490 */ 491 if (q->last_merge) { 492 ret = elv_try_merge(q->last_merge, bio); 493 if (ret != ELEVATOR_NO_MERGE) { 494 *req = q->last_merge; 495 return ret; 496 } 497 } 498 499 if (blk_queue_noxmerges(q)) 500 return ELEVATOR_NO_MERGE; 501 502 /* 503 * See if our hash lookup can find a potential backmerge. 504 */ 505 __rq = elv_rqhash_find(q, bio->bi_sector); 506 if (__rq && elv_rq_merge_ok(__rq, bio)) { 507 *req = __rq; 508 return ELEVATOR_BACK_MERGE; 509 } 510 511 if (e->ops->elevator_merge_fn) 512 return e->ops->elevator_merge_fn(q, req, bio); 513 514 return ELEVATOR_NO_MERGE; 515 } 516 517 /* 518 * Attempt to do an insertion back merge. Only check for the case where 519 * we can append 'rq' to an existing request, so we can throw 'rq' away 520 * afterwards. 521 * 522 * Returns true if we merged, false otherwise 523 */ 524 static bool elv_attempt_insert_merge(struct request_queue *q, 525 struct request *rq) 526 { 527 struct request *__rq; 528 529 if (blk_queue_nomerges(q)) 530 return false; 531 532 /* 533 * First try one-hit cache. 534 */ 535 if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq)) 536 return true; 537 538 if (blk_queue_noxmerges(q)) 539 return false; 540 541 /* 542 * See if our hash lookup can find a potential backmerge. 543 */ 544 __rq = elv_rqhash_find(q, blk_rq_pos(rq)); 545 if (__rq && blk_attempt_req_merge(q, __rq, rq)) 546 return true; 547 548 return false; 549 } 550 551 void elv_merged_request(struct request_queue *q, struct request *rq, int type) 552 { 553 struct elevator_queue *e = q->elevator; 554 555 if (e->ops->elevator_merged_fn) 556 e->ops->elevator_merged_fn(q, rq, type); 557 558 if (type == ELEVATOR_BACK_MERGE) 559 elv_rqhash_reposition(q, rq); 560 561 q->last_merge = rq; 562 } 563 564 void elv_merge_requests(struct request_queue *q, struct request *rq, 565 struct request *next) 566 { 567 struct elevator_queue *e = q->elevator; 568 const int next_sorted = next->cmd_flags & REQ_SORTED; 569 570 if (next_sorted && e->ops->elevator_merge_req_fn) 571 e->ops->elevator_merge_req_fn(q, rq, next); 572 573 elv_rqhash_reposition(q, rq); 574 575 if (next_sorted) { 576 elv_rqhash_del(q, next); 577 q->nr_sorted--; 578 } 579 580 q->last_merge = rq; 581 } 582 583 void elv_bio_merged(struct request_queue *q, struct request *rq, 584 struct bio *bio) 585 { 586 struct elevator_queue *e = q->elevator; 587 588 if (e->ops->elevator_bio_merged_fn) 589 e->ops->elevator_bio_merged_fn(q, rq, bio); 590 } 591 592 void elv_requeue_request(struct request_queue *q, struct request *rq) 593 { 594 /* 595 * it already went through dequeue, we need to decrement the 596 * in_flight count again 597 */ 598 if (blk_account_rq(rq)) { 599 q->in_flight[rq_is_sync(rq)]--; 600 if (rq->cmd_flags & REQ_SORTED) 601 elv_deactivate_rq(q, rq); 602 } 603 604 rq->cmd_flags &= ~REQ_STARTED; 605 606 __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE); 607 } 608 609 void elv_drain_elevator(struct request_queue *q) 610 { 611 static int printed; 612 while (q->elevator->ops->elevator_dispatch_fn(q, 1)) 613 ; 614 if (q->nr_sorted == 0) 615 return; 616 if (printed++ < 10) { 617 printk(KERN_ERR "%s: forced dispatching is broken " 618 "(nr_sorted=%u), please report this\n", 619 q->elevator->elevator_type->elevator_name, q->nr_sorted); 620 } 621 } 622 623 /* 624 * Call with queue lock held, interrupts disabled 625 */ 626 void elv_quiesce_start(struct request_queue *q) 627 { 628 if (!q->elevator) 629 return; 630 631 queue_flag_set(QUEUE_FLAG_ELVSWITCH, q); 632 633 /* 634 * make sure we don't have any requests in flight 635 */ 636 elv_drain_elevator(q); 637 while (q->rq.elvpriv) { 638 __blk_run_queue(q); 639 spin_unlock_irq(q->queue_lock); 640 msleep(10); 641 spin_lock_irq(q->queue_lock); 642 elv_drain_elevator(q); 643 } 644 } 645 646 void elv_quiesce_end(struct request_queue *q) 647 { 648 queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q); 649 } 650 651 void __elv_add_request(struct request_queue *q, struct request *rq, int where) 652 { 653 trace_block_rq_insert(q, rq); 654 655 rq->q = q; 656 657 if (rq->cmd_flags & REQ_SOFTBARRIER) { 658 /* barriers are scheduling boundary, update end_sector */ 659 if (rq->cmd_type == REQ_TYPE_FS || 660 (rq->cmd_flags & REQ_DISCARD)) { 661 q->end_sector = rq_end_sector(rq); 662 q->boundary_rq = rq; 663 } 664 } else if (!(rq->cmd_flags & REQ_ELVPRIV) && 665 (where == ELEVATOR_INSERT_SORT || 666 where == ELEVATOR_INSERT_SORT_MERGE)) 667 where = ELEVATOR_INSERT_BACK; 668 669 switch (where) { 670 case ELEVATOR_INSERT_REQUEUE: 671 case ELEVATOR_INSERT_FRONT: 672 rq->cmd_flags |= REQ_SOFTBARRIER; 673 list_add(&rq->queuelist, &q->queue_head); 674 break; 675 676 case ELEVATOR_INSERT_BACK: 677 rq->cmd_flags |= REQ_SOFTBARRIER; 678 elv_drain_elevator(q); 679 list_add_tail(&rq->queuelist, &q->queue_head); 680 /* 681 * We kick the queue here for the following reasons. 682 * - The elevator might have returned NULL previously 683 * to delay requests and returned them now. As the 684 * queue wasn't empty before this request, ll_rw_blk 685 * won't run the queue on return, resulting in hang. 686 * - Usually, back inserted requests won't be merged 687 * with anything. There's no point in delaying queue 688 * processing. 689 */ 690 __blk_run_queue(q); 691 break; 692 693 case ELEVATOR_INSERT_SORT_MERGE: 694 /* 695 * If we succeed in merging this request with one in the 696 * queue already, we are done - rq has now been freed, 697 * so no need to do anything further. 698 */ 699 if (elv_attempt_insert_merge(q, rq)) 700 break; 701 case ELEVATOR_INSERT_SORT: 702 BUG_ON(rq->cmd_type != REQ_TYPE_FS && 703 !(rq->cmd_flags & REQ_DISCARD)); 704 rq->cmd_flags |= REQ_SORTED; 705 q->nr_sorted++; 706 if (rq_mergeable(rq)) { 707 elv_rqhash_add(q, rq); 708 if (!q->last_merge) 709 q->last_merge = rq; 710 } 711 712 /* 713 * Some ioscheds (cfq) run q->request_fn directly, so 714 * rq cannot be accessed after calling 715 * elevator_add_req_fn. 716 */ 717 q->elevator->ops->elevator_add_req_fn(q, rq); 718 break; 719 720 case ELEVATOR_INSERT_FLUSH: 721 rq->cmd_flags |= REQ_SOFTBARRIER; 722 blk_insert_flush(rq); 723 break; 724 default: 725 printk(KERN_ERR "%s: bad insertion point %d\n", 726 __func__, where); 727 BUG(); 728 } 729 } 730 EXPORT_SYMBOL(__elv_add_request); 731 732 void elv_add_request(struct request_queue *q, struct request *rq, int where) 733 { 734 unsigned long flags; 735 736 spin_lock_irqsave(q->queue_lock, flags); 737 __elv_add_request(q, rq, where); 738 spin_unlock_irqrestore(q->queue_lock, flags); 739 } 740 EXPORT_SYMBOL(elv_add_request); 741 742 struct request *elv_latter_request(struct request_queue *q, struct request *rq) 743 { 744 struct elevator_queue *e = q->elevator; 745 746 if (e->ops->elevator_latter_req_fn) 747 return e->ops->elevator_latter_req_fn(q, rq); 748 return NULL; 749 } 750 751 struct request *elv_former_request(struct request_queue *q, struct request *rq) 752 { 753 struct elevator_queue *e = q->elevator; 754 755 if (e->ops->elevator_former_req_fn) 756 return e->ops->elevator_former_req_fn(q, rq); 757 return NULL; 758 } 759 760 int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) 761 { 762 struct elevator_queue *e = q->elevator; 763 764 if (e->ops->elevator_set_req_fn) 765 return e->ops->elevator_set_req_fn(q, rq, gfp_mask); 766 767 rq->elevator_private[0] = NULL; 768 return 0; 769 } 770 771 void elv_put_request(struct request_queue *q, struct request *rq) 772 { 773 struct elevator_queue *e = q->elevator; 774 775 if (e->ops->elevator_put_req_fn) 776 e->ops->elevator_put_req_fn(rq); 777 } 778 779 int elv_may_queue(struct request_queue *q, int rw) 780 { 781 struct elevator_queue *e = q->elevator; 782 783 if (e->ops->elevator_may_queue_fn) 784 return e->ops->elevator_may_queue_fn(q, rw); 785 786 return ELV_MQUEUE_MAY; 787 } 788 789 void elv_abort_queue(struct request_queue *q) 790 { 791 struct request *rq; 792 793 blk_abort_flushes(q); 794 795 while (!list_empty(&q->queue_head)) { 796 rq = list_entry_rq(q->queue_head.next); 797 rq->cmd_flags |= REQ_QUIET; 798 trace_block_rq_abort(q, rq); 799 /* 800 * Mark this request as started so we don't trigger 801 * any debug logic in the end I/O path. 802 */ 803 blk_start_request(rq); 804 __blk_end_request_all(rq, -EIO); 805 } 806 } 807 EXPORT_SYMBOL(elv_abort_queue); 808 809 void elv_completed_request(struct request_queue *q, struct request *rq) 810 { 811 struct elevator_queue *e = q->elevator; 812 813 /* 814 * request is released from the driver, io must be done 815 */ 816 if (blk_account_rq(rq)) { 817 q->in_flight[rq_is_sync(rq)]--; 818 if ((rq->cmd_flags & REQ_SORTED) && 819 e->ops->elevator_completed_req_fn) 820 e->ops->elevator_completed_req_fn(q, rq); 821 } 822 } 823 824 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr) 825 826 static ssize_t 827 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page) 828 { 829 struct elv_fs_entry *entry = to_elv(attr); 830 struct elevator_queue *e; 831 ssize_t error; 832 833 if (!entry->show) 834 return -EIO; 835 836 e = container_of(kobj, struct elevator_queue, kobj); 837 mutex_lock(&e->sysfs_lock); 838 error = e->ops ? entry->show(e, page) : -ENOENT; 839 mutex_unlock(&e->sysfs_lock); 840 return error; 841 } 842 843 static ssize_t 844 elv_attr_store(struct kobject *kobj, struct attribute *attr, 845 const char *page, size_t length) 846 { 847 struct elv_fs_entry *entry = to_elv(attr); 848 struct elevator_queue *e; 849 ssize_t error; 850 851 if (!entry->store) 852 return -EIO; 853 854 e = container_of(kobj, struct elevator_queue, kobj); 855 mutex_lock(&e->sysfs_lock); 856 error = e->ops ? entry->store(e, page, length) : -ENOENT; 857 mutex_unlock(&e->sysfs_lock); 858 return error; 859 } 860 861 static const struct sysfs_ops elv_sysfs_ops = { 862 .show = elv_attr_show, 863 .store = elv_attr_store, 864 }; 865 866 static struct kobj_type elv_ktype = { 867 .sysfs_ops = &elv_sysfs_ops, 868 .release = elevator_release, 869 }; 870 871 int elv_register_queue(struct request_queue *q) 872 { 873 struct elevator_queue *e = q->elevator; 874 int error; 875 876 error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched"); 877 if (!error) { 878 struct elv_fs_entry *attr = e->elevator_type->elevator_attrs; 879 if (attr) { 880 while (attr->attr.name) { 881 if (sysfs_create_file(&e->kobj, &attr->attr)) 882 break; 883 attr++; 884 } 885 } 886 kobject_uevent(&e->kobj, KOBJ_ADD); 887 e->registered = 1; 888 } 889 return error; 890 } 891 EXPORT_SYMBOL(elv_register_queue); 892 893 static void __elv_unregister_queue(struct elevator_queue *e) 894 { 895 kobject_uevent(&e->kobj, KOBJ_REMOVE); 896 kobject_del(&e->kobj); 897 e->registered = 0; 898 } 899 900 void elv_unregister_queue(struct request_queue *q) 901 { 902 if (q) 903 __elv_unregister_queue(q->elevator); 904 } 905 EXPORT_SYMBOL(elv_unregister_queue); 906 907 void elv_register(struct elevator_type *e) 908 { 909 char *def = ""; 910 911 spin_lock(&elv_list_lock); 912 BUG_ON(elevator_find(e->elevator_name)); 913 list_add_tail(&e->list, &elv_list); 914 spin_unlock(&elv_list_lock); 915 916 if (!strcmp(e->elevator_name, chosen_elevator) || 917 (!*chosen_elevator && 918 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED))) 919 def = " (default)"; 920 921 printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name, 922 def); 923 } 924 EXPORT_SYMBOL_GPL(elv_register); 925 926 void elv_unregister(struct elevator_type *e) 927 { 928 struct task_struct *g, *p; 929 930 /* 931 * Iterate every thread in the process to remove the io contexts. 932 */ 933 if (e->ops.trim) { 934 read_lock(&tasklist_lock); 935 do_each_thread(g, p) { 936 task_lock(p); 937 if (p->io_context) 938 e->ops.trim(p->io_context); 939 task_unlock(p); 940 } while_each_thread(g, p); 941 read_unlock(&tasklist_lock); 942 } 943 944 spin_lock(&elv_list_lock); 945 list_del_init(&e->list); 946 spin_unlock(&elv_list_lock); 947 } 948 EXPORT_SYMBOL_GPL(elv_unregister); 949 950 /* 951 * switch to new_e io scheduler. be careful not to introduce deadlocks - 952 * we don't free the old io scheduler, before we have allocated what we 953 * need for the new one. this way we have a chance of going back to the old 954 * one, if the new one fails init for some reason. 955 */ 956 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) 957 { 958 struct elevator_queue *old_elevator, *e; 959 void *data; 960 int err; 961 962 /* 963 * Allocate new elevator 964 */ 965 e = elevator_alloc(q, new_e); 966 if (!e) 967 return -ENOMEM; 968 969 data = elevator_init_queue(q, e); 970 if (!data) { 971 kobject_put(&e->kobj); 972 return -ENOMEM; 973 } 974 975 /* 976 * Turn on BYPASS and drain all requests w/ elevator private data 977 */ 978 spin_lock_irq(q->queue_lock); 979 elv_quiesce_start(q); 980 981 /* 982 * Remember old elevator. 983 */ 984 old_elevator = q->elevator; 985 986 /* 987 * attach and start new elevator 988 */ 989 elevator_attach(q, e, data); 990 991 spin_unlock_irq(q->queue_lock); 992 993 if (old_elevator->registered) { 994 __elv_unregister_queue(old_elevator); 995 996 err = elv_register_queue(q); 997 if (err) 998 goto fail_register; 999 } 1000 1001 /* 1002 * finally exit old elevator and turn off BYPASS. 1003 */ 1004 elevator_exit(old_elevator); 1005 spin_lock_irq(q->queue_lock); 1006 elv_quiesce_end(q); 1007 spin_unlock_irq(q->queue_lock); 1008 1009 blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name); 1010 1011 return 0; 1012 1013 fail_register: 1014 /* 1015 * switch failed, exit the new io scheduler and reattach the old 1016 * one again (along with re-adding the sysfs dir) 1017 */ 1018 elevator_exit(e); 1019 q->elevator = old_elevator; 1020 elv_register_queue(q); 1021 1022 spin_lock_irq(q->queue_lock); 1023 queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q); 1024 spin_unlock_irq(q->queue_lock); 1025 1026 return err; 1027 } 1028 1029 /* 1030 * Switch this queue to the given IO scheduler. 1031 */ 1032 int elevator_change(struct request_queue *q, const char *name) 1033 { 1034 char elevator_name[ELV_NAME_MAX]; 1035 struct elevator_type *e; 1036 1037 if (!q->elevator) 1038 return -ENXIO; 1039 1040 strlcpy(elevator_name, name, sizeof(elevator_name)); 1041 e = elevator_get(strstrip(elevator_name)); 1042 if (!e) { 1043 printk(KERN_ERR "elevator: type %s not found\n", elevator_name); 1044 return -EINVAL; 1045 } 1046 1047 if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) { 1048 elevator_put(e); 1049 return 0; 1050 } 1051 1052 return elevator_switch(q, e); 1053 } 1054 EXPORT_SYMBOL(elevator_change); 1055 1056 ssize_t elv_iosched_store(struct request_queue *q, const char *name, 1057 size_t count) 1058 { 1059 int ret; 1060 1061 if (!q->elevator) 1062 return count; 1063 1064 ret = elevator_change(q, name); 1065 if (!ret) 1066 return count; 1067 1068 printk(KERN_ERR "elevator: switch to %s failed\n", name); 1069 return ret; 1070 } 1071 1072 ssize_t elv_iosched_show(struct request_queue *q, char *name) 1073 { 1074 struct elevator_queue *e = q->elevator; 1075 struct elevator_type *elv; 1076 struct elevator_type *__e; 1077 int len = 0; 1078 1079 if (!q->elevator || !blk_queue_stackable(q)) 1080 return sprintf(name, "none\n"); 1081 1082 elv = e->elevator_type; 1083 1084 spin_lock(&elv_list_lock); 1085 list_for_each_entry(__e, &elv_list, list) { 1086 if (!strcmp(elv->elevator_name, __e->elevator_name)) 1087 len += sprintf(name+len, "[%s] ", elv->elevator_name); 1088 else 1089 len += sprintf(name+len, "%s ", __e->elevator_name); 1090 } 1091 spin_unlock(&elv_list_lock); 1092 1093 len += sprintf(len+name, "\n"); 1094 return len; 1095 } 1096 1097 struct request *elv_rb_former_request(struct request_queue *q, 1098 struct request *rq) 1099 { 1100 struct rb_node *rbprev = rb_prev(&rq->rb_node); 1101 1102 if (rbprev) 1103 return rb_entry_rq(rbprev); 1104 1105 return NULL; 1106 } 1107 EXPORT_SYMBOL(elv_rb_former_request); 1108 1109 struct request *elv_rb_latter_request(struct request_queue *q, 1110 struct request *rq) 1111 { 1112 struct rb_node *rbnext = rb_next(&rq->rb_node); 1113 1114 if (rbnext) 1115 return rb_entry_rq(rbnext); 1116 1117 return NULL; 1118 } 1119 EXPORT_SYMBOL(elv_rb_latter_request); 1120