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_rw_flagged(bio, BIO_RW_DISCARD) != 83 bio_rw_flagged(rq->bio, BIO_RW_DISCARD)) 84 return 0; 85 86 /* 87 * different data direction or already started, don't merge 88 */ 89 if (bio_data_dir(bio) != rq_data_dir(rq)) 90 return 0; 91 92 /* 93 * must be same device and not a special request 94 */ 95 if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special) 96 return 0; 97 98 /* 99 * only merge integrity protected bio into ditto rq 100 */ 101 if (bio_integrity(bio) != blk_integrity_rq(rq)) 102 return 0; 103 104 if (!elv_iosched_allow_merge(rq, bio)) 105 return 0; 106 107 return 1; 108 } 109 EXPORT_SYMBOL(elv_rq_merge_ok); 110 111 static inline int elv_try_merge(struct request *__rq, struct bio *bio) 112 { 113 int ret = ELEVATOR_NO_MERGE; 114 115 /* 116 * we can merge and sequence is ok, check if it's possible 117 */ 118 if (elv_rq_merge_ok(__rq, bio)) { 119 if (blk_rq_pos(__rq) + blk_rq_sectors(__rq) == bio->bi_sector) 120 ret = ELEVATOR_BACK_MERGE; 121 else if (blk_rq_pos(__rq) - bio_sectors(bio) == bio->bi_sector) 122 ret = ELEVATOR_FRONT_MERGE; 123 } 124 125 return ret; 126 } 127 128 static struct elevator_type *elevator_find(const char *name) 129 { 130 struct elevator_type *e; 131 132 list_for_each_entry(e, &elv_list, list) { 133 if (!strcmp(e->elevator_name, name)) 134 return e; 135 } 136 137 return NULL; 138 } 139 140 static void elevator_put(struct elevator_type *e) 141 { 142 module_put(e->elevator_owner); 143 } 144 145 static struct elevator_type *elevator_get(const char *name) 146 { 147 struct elevator_type *e; 148 149 spin_lock(&elv_list_lock); 150 151 e = elevator_find(name); 152 if (!e) { 153 char elv[ELV_NAME_MAX + strlen("-iosched")]; 154 155 spin_unlock(&elv_list_lock); 156 157 snprintf(elv, sizeof(elv), "%s-iosched", name); 158 159 request_module("%s", elv); 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_HARDBARRIER | REQ_STARTED; 428 list_for_each_prev(entry, &q->queue_head) { 429 struct request *pos = list_entry_rq(entry); 430 431 if (blk_discard_rq(rq) != blk_discard_rq(pos)) 432 break; 433 if (rq_data_dir(rq) != rq_data_dir(pos)) 434 break; 435 if (pos->cmd_flags & stop_flags) 436 break; 437 if (blk_rq_pos(rq) >= boundary) { 438 if (blk_rq_pos(pos) < boundary) 439 continue; 440 } else { 441 if (blk_rq_pos(pos) >= boundary) 442 break; 443 } 444 if (blk_rq_pos(rq) >= blk_rq_pos(pos)) 445 break; 446 } 447 448 list_add(&rq->queuelist, entry); 449 } 450 EXPORT_SYMBOL(elv_dispatch_sort); 451 452 /* 453 * Insert rq into dispatch queue of q. Queue lock must be held on 454 * entry. rq is added to the back of the dispatch queue. To be used by 455 * specific elevators. 456 */ 457 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq) 458 { 459 if (q->last_merge == rq) 460 q->last_merge = NULL; 461 462 elv_rqhash_del(q, rq); 463 464 q->nr_sorted--; 465 466 q->end_sector = rq_end_sector(rq); 467 q->boundary_rq = rq; 468 list_add_tail(&rq->queuelist, &q->queue_head); 469 } 470 EXPORT_SYMBOL(elv_dispatch_add_tail); 471 472 int elv_merge(struct request_queue *q, struct request **req, struct bio *bio) 473 { 474 struct elevator_queue *e = q->elevator; 475 struct request *__rq; 476 int ret; 477 478 /* 479 * Levels of merges: 480 * nomerges: No merges at all attempted 481 * noxmerges: Only simple one-hit cache try 482 * merges: All merge tries attempted 483 */ 484 if (blk_queue_nomerges(q)) 485 return ELEVATOR_NO_MERGE; 486 487 /* 488 * First try one-hit cache. 489 */ 490 if (q->last_merge) { 491 ret = elv_try_merge(q->last_merge, bio); 492 if (ret != ELEVATOR_NO_MERGE) { 493 *req = q->last_merge; 494 return ret; 495 } 496 } 497 498 if (blk_queue_noxmerges(q)) 499 return ELEVATOR_NO_MERGE; 500 501 /* 502 * See if our hash lookup can find a potential backmerge. 503 */ 504 __rq = elv_rqhash_find(q, bio->bi_sector); 505 if (__rq && elv_rq_merge_ok(__rq, bio)) { 506 *req = __rq; 507 return ELEVATOR_BACK_MERGE; 508 } 509 510 if (e->ops->elevator_merge_fn) 511 return e->ops->elevator_merge_fn(q, req, bio); 512 513 return ELEVATOR_NO_MERGE; 514 } 515 516 void elv_merged_request(struct request_queue *q, struct request *rq, int type) 517 { 518 struct elevator_queue *e = q->elevator; 519 520 if (e->ops->elevator_merged_fn) 521 e->ops->elevator_merged_fn(q, rq, type); 522 523 if (type == ELEVATOR_BACK_MERGE) 524 elv_rqhash_reposition(q, rq); 525 526 q->last_merge = rq; 527 } 528 529 void elv_merge_requests(struct request_queue *q, struct request *rq, 530 struct request *next) 531 { 532 struct elevator_queue *e = q->elevator; 533 534 if (e->ops->elevator_merge_req_fn) 535 e->ops->elevator_merge_req_fn(q, rq, next); 536 537 elv_rqhash_reposition(q, rq); 538 elv_rqhash_del(q, next); 539 540 q->nr_sorted--; 541 q->last_merge = rq; 542 } 543 544 void elv_bio_merged(struct request_queue *q, struct request *rq, 545 struct bio *bio) 546 { 547 struct elevator_queue *e = q->elevator; 548 549 if (e->ops->elevator_bio_merged_fn) 550 e->ops->elevator_bio_merged_fn(q, rq, bio); 551 } 552 553 void elv_requeue_request(struct request_queue *q, struct request *rq) 554 { 555 /* 556 * it already went through dequeue, we need to decrement the 557 * in_flight count again 558 */ 559 if (blk_account_rq(rq)) { 560 q->in_flight[rq_is_sync(rq)]--; 561 if (blk_sorted_rq(rq)) 562 elv_deactivate_rq(q, rq); 563 } 564 565 rq->cmd_flags &= ~REQ_STARTED; 566 567 elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE); 568 } 569 570 void elv_drain_elevator(struct request_queue *q) 571 { 572 static int printed; 573 while (q->elevator->ops->elevator_dispatch_fn(q, 1)) 574 ; 575 if (q->nr_sorted == 0) 576 return; 577 if (printed++ < 10) { 578 printk(KERN_ERR "%s: forced dispatching is broken " 579 "(nr_sorted=%u), please report this\n", 580 q->elevator->elevator_type->elevator_name, q->nr_sorted); 581 } 582 } 583 584 /* 585 * Call with queue lock held, interrupts disabled 586 */ 587 void elv_quiesce_start(struct request_queue *q) 588 { 589 if (!q->elevator) 590 return; 591 592 queue_flag_set(QUEUE_FLAG_ELVSWITCH, q); 593 594 /* 595 * make sure we don't have any requests in flight 596 */ 597 elv_drain_elevator(q); 598 while (q->rq.elvpriv) { 599 __blk_run_queue(q); 600 spin_unlock_irq(q->queue_lock); 601 msleep(10); 602 spin_lock_irq(q->queue_lock); 603 elv_drain_elevator(q); 604 } 605 } 606 607 void elv_quiesce_end(struct request_queue *q) 608 { 609 queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q); 610 } 611 612 void elv_insert(struct request_queue *q, struct request *rq, int where) 613 { 614 struct list_head *pos; 615 unsigned ordseq; 616 int unplug_it = 1; 617 618 trace_block_rq_insert(q, rq); 619 620 rq->q = q; 621 622 switch (where) { 623 case ELEVATOR_INSERT_FRONT: 624 rq->cmd_flags |= REQ_SOFTBARRIER; 625 626 list_add(&rq->queuelist, &q->queue_head); 627 break; 628 629 case ELEVATOR_INSERT_BACK: 630 rq->cmd_flags |= REQ_SOFTBARRIER; 631 elv_drain_elevator(q); 632 list_add_tail(&rq->queuelist, &q->queue_head); 633 /* 634 * We kick the queue here for the following reasons. 635 * - The elevator might have returned NULL previously 636 * to delay requests and returned them now. As the 637 * queue wasn't empty before this request, ll_rw_blk 638 * won't run the queue on return, resulting in hang. 639 * - Usually, back inserted requests won't be merged 640 * with anything. There's no point in delaying queue 641 * processing. 642 */ 643 __blk_run_queue(q); 644 break; 645 646 case ELEVATOR_INSERT_SORT: 647 BUG_ON(!blk_fs_request(rq) && !blk_discard_rq(rq)); 648 rq->cmd_flags |= REQ_SORTED; 649 q->nr_sorted++; 650 if (rq_mergeable(rq)) { 651 elv_rqhash_add(q, rq); 652 if (!q->last_merge) 653 q->last_merge = rq; 654 } 655 656 /* 657 * Some ioscheds (cfq) run q->request_fn directly, so 658 * rq cannot be accessed after calling 659 * elevator_add_req_fn. 660 */ 661 q->elevator->ops->elevator_add_req_fn(q, rq); 662 break; 663 664 case ELEVATOR_INSERT_REQUEUE: 665 /* 666 * If ordered flush isn't in progress, we do front 667 * insertion; otherwise, requests should be requeued 668 * in ordseq order. 669 */ 670 rq->cmd_flags |= REQ_SOFTBARRIER; 671 672 /* 673 * Most requeues happen because of a busy condition, 674 * don't force unplug of the queue for that case. 675 */ 676 unplug_it = 0; 677 678 if (q->ordseq == 0) { 679 list_add(&rq->queuelist, &q->queue_head); 680 break; 681 } 682 683 ordseq = blk_ordered_req_seq(rq); 684 685 list_for_each(pos, &q->queue_head) { 686 struct request *pos_rq = list_entry_rq(pos); 687 if (ordseq <= blk_ordered_req_seq(pos_rq)) 688 break; 689 } 690 691 list_add_tail(&rq->queuelist, pos); 692 break; 693 694 default: 695 printk(KERN_ERR "%s: bad insertion point %d\n", 696 __func__, where); 697 BUG(); 698 } 699 700 if (unplug_it && blk_queue_plugged(q)) { 701 int nrq = q->rq.count[BLK_RW_SYNC] + q->rq.count[BLK_RW_ASYNC] 702 - queue_in_flight(q); 703 704 if (nrq >= q->unplug_thresh) 705 __generic_unplug_device(q); 706 } 707 } 708 709 void __elv_add_request(struct request_queue *q, struct request *rq, int where, 710 int plug) 711 { 712 if (q->ordcolor) 713 rq->cmd_flags |= REQ_ORDERED_COLOR; 714 715 if (rq->cmd_flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) { 716 /* 717 * toggle ordered color 718 */ 719 if (blk_barrier_rq(rq)) 720 q->ordcolor ^= 1; 721 722 /* 723 * barriers implicitly indicate back insertion 724 */ 725 if (where == ELEVATOR_INSERT_SORT) 726 where = ELEVATOR_INSERT_BACK; 727 728 /* 729 * this request is scheduling boundary, update 730 * end_sector 731 */ 732 if (blk_fs_request(rq) || blk_discard_rq(rq)) { 733 q->end_sector = rq_end_sector(rq); 734 q->boundary_rq = rq; 735 } 736 } else if (!(rq->cmd_flags & REQ_ELVPRIV) && 737 where == ELEVATOR_INSERT_SORT) 738 where = ELEVATOR_INSERT_BACK; 739 740 if (plug) 741 blk_plug_device(q); 742 743 elv_insert(q, rq, where); 744 } 745 EXPORT_SYMBOL(__elv_add_request); 746 747 void elv_add_request(struct request_queue *q, struct request *rq, int where, 748 int plug) 749 { 750 unsigned long flags; 751 752 spin_lock_irqsave(q->queue_lock, flags); 753 __elv_add_request(q, rq, where, plug); 754 spin_unlock_irqrestore(q->queue_lock, flags); 755 } 756 EXPORT_SYMBOL(elv_add_request); 757 758 int elv_queue_empty(struct request_queue *q) 759 { 760 struct elevator_queue *e = q->elevator; 761 762 if (!list_empty(&q->queue_head)) 763 return 0; 764 765 if (e->ops->elevator_queue_empty_fn) 766 return e->ops->elevator_queue_empty_fn(q); 767 768 return 1; 769 } 770 EXPORT_SYMBOL(elv_queue_empty); 771 772 struct request *elv_latter_request(struct request_queue *q, struct request *rq) 773 { 774 struct elevator_queue *e = q->elevator; 775 776 if (e->ops->elevator_latter_req_fn) 777 return e->ops->elevator_latter_req_fn(q, rq); 778 return NULL; 779 } 780 781 struct request *elv_former_request(struct request_queue *q, struct request *rq) 782 { 783 struct elevator_queue *e = q->elevator; 784 785 if (e->ops->elevator_former_req_fn) 786 return e->ops->elevator_former_req_fn(q, rq); 787 return NULL; 788 } 789 790 int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) 791 { 792 struct elevator_queue *e = q->elevator; 793 794 if (e->ops->elevator_set_req_fn) 795 return e->ops->elevator_set_req_fn(q, rq, gfp_mask); 796 797 rq->elevator_private = NULL; 798 return 0; 799 } 800 801 void elv_put_request(struct request_queue *q, struct request *rq) 802 { 803 struct elevator_queue *e = q->elevator; 804 805 if (e->ops->elevator_put_req_fn) 806 e->ops->elevator_put_req_fn(rq); 807 } 808 809 int elv_may_queue(struct request_queue *q, int rw) 810 { 811 struct elevator_queue *e = q->elevator; 812 813 if (e->ops->elevator_may_queue_fn) 814 return e->ops->elevator_may_queue_fn(q, rw); 815 816 return ELV_MQUEUE_MAY; 817 } 818 819 void elv_abort_queue(struct request_queue *q) 820 { 821 struct request *rq; 822 823 while (!list_empty(&q->queue_head)) { 824 rq = list_entry_rq(q->queue_head.next); 825 rq->cmd_flags |= REQ_QUIET; 826 trace_block_rq_abort(q, rq); 827 /* 828 * Mark this request as started so we don't trigger 829 * any debug logic in the end I/O path. 830 */ 831 blk_start_request(rq); 832 __blk_end_request_all(rq, -EIO); 833 } 834 } 835 EXPORT_SYMBOL(elv_abort_queue); 836 837 void elv_completed_request(struct request_queue *q, struct request *rq) 838 { 839 struct elevator_queue *e = q->elevator; 840 841 /* 842 * request is released from the driver, io must be done 843 */ 844 if (blk_account_rq(rq)) { 845 q->in_flight[rq_is_sync(rq)]--; 846 if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn) 847 e->ops->elevator_completed_req_fn(q, rq); 848 } 849 850 /* 851 * Check if the queue is waiting for fs requests to be 852 * drained for flush sequence. 853 */ 854 if (unlikely(q->ordseq)) { 855 struct request *next = NULL; 856 857 if (!list_empty(&q->queue_head)) 858 next = list_entry_rq(q->queue_head.next); 859 860 if (!queue_in_flight(q) && 861 blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN && 862 (!next || blk_ordered_req_seq(next) > QUEUE_ORDSEQ_DRAIN)) { 863 blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0); 864 __blk_run_queue(q); 865 } 866 } 867 } 868 869 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr) 870 871 static ssize_t 872 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page) 873 { 874 struct elv_fs_entry *entry = to_elv(attr); 875 struct elevator_queue *e; 876 ssize_t error; 877 878 if (!entry->show) 879 return -EIO; 880 881 e = container_of(kobj, struct elevator_queue, kobj); 882 mutex_lock(&e->sysfs_lock); 883 error = e->ops ? entry->show(e, page) : -ENOENT; 884 mutex_unlock(&e->sysfs_lock); 885 return error; 886 } 887 888 static ssize_t 889 elv_attr_store(struct kobject *kobj, struct attribute *attr, 890 const char *page, size_t length) 891 { 892 struct elv_fs_entry *entry = to_elv(attr); 893 struct elevator_queue *e; 894 ssize_t error; 895 896 if (!entry->store) 897 return -EIO; 898 899 e = container_of(kobj, struct elevator_queue, kobj); 900 mutex_lock(&e->sysfs_lock); 901 error = e->ops ? entry->store(e, page, length) : -ENOENT; 902 mutex_unlock(&e->sysfs_lock); 903 return error; 904 } 905 906 static const struct sysfs_ops elv_sysfs_ops = { 907 .show = elv_attr_show, 908 .store = elv_attr_store, 909 }; 910 911 static struct kobj_type elv_ktype = { 912 .sysfs_ops = &elv_sysfs_ops, 913 .release = elevator_release, 914 }; 915 916 int elv_register_queue(struct request_queue *q) 917 { 918 struct elevator_queue *e = q->elevator; 919 int error; 920 921 error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched"); 922 if (!error) { 923 struct elv_fs_entry *attr = e->elevator_type->elevator_attrs; 924 if (attr) { 925 while (attr->attr.name) { 926 if (sysfs_create_file(&e->kobj, &attr->attr)) 927 break; 928 attr++; 929 } 930 } 931 kobject_uevent(&e->kobj, KOBJ_ADD); 932 } 933 return error; 934 } 935 EXPORT_SYMBOL(elv_register_queue); 936 937 static void __elv_unregister_queue(struct elevator_queue *e) 938 { 939 kobject_uevent(&e->kobj, KOBJ_REMOVE); 940 kobject_del(&e->kobj); 941 } 942 943 void elv_unregister_queue(struct request_queue *q) 944 { 945 if (q) 946 __elv_unregister_queue(q->elevator); 947 } 948 EXPORT_SYMBOL(elv_unregister_queue); 949 950 void elv_register(struct elevator_type *e) 951 { 952 char *def = ""; 953 954 spin_lock(&elv_list_lock); 955 BUG_ON(elevator_find(e->elevator_name)); 956 list_add_tail(&e->list, &elv_list); 957 spin_unlock(&elv_list_lock); 958 959 if (!strcmp(e->elevator_name, chosen_elevator) || 960 (!*chosen_elevator && 961 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED))) 962 def = " (default)"; 963 964 printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name, 965 def); 966 } 967 EXPORT_SYMBOL_GPL(elv_register); 968 969 void elv_unregister(struct elevator_type *e) 970 { 971 struct task_struct *g, *p; 972 973 /* 974 * Iterate every thread in the process to remove the io contexts. 975 */ 976 if (e->ops.trim) { 977 read_lock(&tasklist_lock); 978 do_each_thread(g, p) { 979 task_lock(p); 980 if (p->io_context) 981 e->ops.trim(p->io_context); 982 task_unlock(p); 983 } while_each_thread(g, p); 984 read_unlock(&tasklist_lock); 985 } 986 987 spin_lock(&elv_list_lock); 988 list_del_init(&e->list); 989 spin_unlock(&elv_list_lock); 990 } 991 EXPORT_SYMBOL_GPL(elv_unregister); 992 993 /* 994 * switch to new_e io scheduler. be careful not to introduce deadlocks - 995 * we don't free the old io scheduler, before we have allocated what we 996 * need for the new one. this way we have a chance of going back to the old 997 * one, if the new one fails init for some reason. 998 */ 999 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) 1000 { 1001 struct elevator_queue *old_elevator, *e; 1002 void *data; 1003 1004 /* 1005 * Allocate new elevator 1006 */ 1007 e = elevator_alloc(q, new_e); 1008 if (!e) 1009 return 0; 1010 1011 data = elevator_init_queue(q, e); 1012 if (!data) { 1013 kobject_put(&e->kobj); 1014 return 0; 1015 } 1016 1017 /* 1018 * Turn on BYPASS and drain all requests w/ elevator private data 1019 */ 1020 spin_lock_irq(q->queue_lock); 1021 elv_quiesce_start(q); 1022 1023 /* 1024 * Remember old elevator. 1025 */ 1026 old_elevator = q->elevator; 1027 1028 /* 1029 * attach and start new elevator 1030 */ 1031 elevator_attach(q, e, data); 1032 1033 spin_unlock_irq(q->queue_lock); 1034 1035 __elv_unregister_queue(old_elevator); 1036 1037 if (elv_register_queue(q)) 1038 goto fail_register; 1039 1040 /* 1041 * finally exit old elevator and turn off BYPASS. 1042 */ 1043 elevator_exit(old_elevator); 1044 spin_lock_irq(q->queue_lock); 1045 elv_quiesce_end(q); 1046 spin_unlock_irq(q->queue_lock); 1047 1048 blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name); 1049 1050 return 1; 1051 1052 fail_register: 1053 /* 1054 * switch failed, exit the new io scheduler and reattach the old 1055 * one again (along with re-adding the sysfs dir) 1056 */ 1057 elevator_exit(e); 1058 q->elevator = old_elevator; 1059 elv_register_queue(q); 1060 1061 spin_lock_irq(q->queue_lock); 1062 queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q); 1063 spin_unlock_irq(q->queue_lock); 1064 1065 return 0; 1066 } 1067 1068 ssize_t elv_iosched_store(struct request_queue *q, const char *name, 1069 size_t count) 1070 { 1071 char elevator_name[ELV_NAME_MAX]; 1072 struct elevator_type *e; 1073 1074 if (!q->elevator) 1075 return count; 1076 1077 strlcpy(elevator_name, name, sizeof(elevator_name)); 1078 e = elevator_get(strstrip(elevator_name)); 1079 if (!e) { 1080 printk(KERN_ERR "elevator: type %s not found\n", elevator_name); 1081 return -EINVAL; 1082 } 1083 1084 if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) { 1085 elevator_put(e); 1086 return count; 1087 } 1088 1089 if (!elevator_switch(q, e)) 1090 printk(KERN_ERR "elevator: switch to %s failed\n", 1091 elevator_name); 1092 return count; 1093 } 1094 1095 ssize_t elv_iosched_show(struct request_queue *q, char *name) 1096 { 1097 struct elevator_queue *e = q->elevator; 1098 struct elevator_type *elv; 1099 struct elevator_type *__e; 1100 int len = 0; 1101 1102 if (!q->elevator || !blk_queue_stackable(q)) 1103 return sprintf(name, "none\n"); 1104 1105 elv = e->elevator_type; 1106 1107 spin_lock(&elv_list_lock); 1108 list_for_each_entry(__e, &elv_list, list) { 1109 if (!strcmp(elv->elevator_name, __e->elevator_name)) 1110 len += sprintf(name+len, "[%s] ", elv->elevator_name); 1111 else 1112 len += sprintf(name+len, "%s ", __e->elevator_name); 1113 } 1114 spin_unlock(&elv_list_lock); 1115 1116 len += sprintf(len+name, "\n"); 1117 return len; 1118 } 1119 1120 struct request *elv_rb_former_request(struct request_queue *q, 1121 struct request *rq) 1122 { 1123 struct rb_node *rbprev = rb_prev(&rq->rb_node); 1124 1125 if (rbprev) 1126 return rb_entry_rq(rbprev); 1127 1128 return NULL; 1129 } 1130 EXPORT_SYMBOL(elv_rb_former_request); 1131 1132 struct request *elv_rb_latter_request(struct request_queue *q, 1133 struct request *rq) 1134 { 1135 struct rb_node *rbnext = rb_next(&rq->rb_node); 1136 1137 if (rbnext) 1138 return rb_entry_rq(rbnext); 1139 1140 return NULL; 1141 } 1142 EXPORT_SYMBOL(elv_rb_latter_request); 1143