block/elevator.c

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