linux/block/elevator.c
<<
>>
Prefs
   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/blktrace_api.h>
  35#include <linux/hash.h>
  36#include <linux/uaccess.h>
  37#include <linux/pm_runtime.h>
  38
  39#include <trace/events/block.h>
  40
  41#include "blk.h"
  42#include "blk-cgroup.h"
  43
  44static DEFINE_SPINLOCK(elv_list_lock);
  45static LIST_HEAD(elv_list);
  46
  47/*
  48 * Merge hash stuff.
  49 */
  50#define rq_hash_key(rq)         (blk_rq_pos(rq) + blk_rq_sectors(rq))
  51
  52/*
  53 * Query io scheduler to see if the current process issuing bio may be
  54 * merged with rq.
  55 */
  56static int elv_iosched_allow_merge(struct request *rq, struct bio *bio)
  57{
  58        struct request_queue *q = rq->q;
  59        struct elevator_queue *e = q->elevator;
  60
  61        if (e->type->ops.elevator_allow_merge_fn)
  62                return e->type->ops.elevator_allow_merge_fn(q, rq, bio);
  63
  64        return 1;
  65}
  66
  67/*
  68 * can we safely merge with this request?
  69 */
  70bool elv_rq_merge_ok(struct request *rq, struct bio *bio)
  71{
  72        if (!blk_rq_merge_ok(rq, bio))
  73                return 0;
  74
  75        if (!elv_iosched_allow_merge(rq, bio))
  76                return 0;
  77
  78        return 1;
  79}
  80EXPORT_SYMBOL(elv_rq_merge_ok);
  81
  82static struct elevator_type *elevator_find(const char *name)
  83{
  84        struct elevator_type *e;
  85
  86        list_for_each_entry(e, &elv_list, list) {
  87                if (!strcmp(e->elevator_name, name))
  88                        return e;
  89        }
  90
  91        return NULL;
  92}
  93
  94static void elevator_put(struct elevator_type *e)
  95{
  96        module_put(e->elevator_owner);
  97}
  98
  99static struct elevator_type *elevator_get(const char *name, bool try_loading)
 100{
 101        struct elevator_type *e;
 102
 103        spin_lock(&elv_list_lock);
 104
 105        e = elevator_find(name);
 106        if (!e && try_loading) {
 107                spin_unlock(&elv_list_lock);
 108                request_module("%s-iosched", name);
 109                spin_lock(&elv_list_lock);
 110                e = elevator_find(name);
 111        }
 112
 113        if (e && !try_module_get(e->elevator_owner))
 114                e = NULL;
 115
 116        spin_unlock(&elv_list_lock);
 117
 118        return e;
 119}
 120
 121static char chosen_elevator[ELV_NAME_MAX];
 122
 123static int __init elevator_setup(char *str)
 124{
 125        /*
 126         * Be backwards-compatible with previous kernels, so users
 127         * won't get the wrong elevator.
 128         */
 129        strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
 130        return 1;
 131}
 132
 133__setup("elevator=", elevator_setup);
 134
 135/* called during boot to load the elevator chosen by the elevator param */
 136void __init load_default_elevator_module(void)
 137{
 138        struct elevator_type *e;
 139
 140        if (!chosen_elevator[0])
 141                return;
 142
 143        spin_lock(&elv_list_lock);
 144        e = elevator_find(chosen_elevator);
 145        spin_unlock(&elv_list_lock);
 146
 147        if (!e)
 148                request_module("%s-iosched", chosen_elevator);
 149}
 150
 151static struct kobj_type elv_ktype;
 152
 153static struct elevator_queue *elevator_alloc(struct request_queue *q,
 154                                  struct elevator_type *e)
 155{
 156        struct elevator_queue *eq;
 157
 158        eq = kmalloc_node(sizeof(*eq), GFP_KERNEL | __GFP_ZERO, q->node);
 159        if (unlikely(!eq))
 160                goto err;
 161
 162        eq->type = e;
 163        kobject_init(&eq->kobj, &elv_ktype);
 164        mutex_init(&eq->sysfs_lock);
 165        hash_init(eq->hash);
 166
 167        return eq;
 168err:
 169        kfree(eq);
 170        elevator_put(e);
 171        return NULL;
 172}
 173
 174static void elevator_release(struct kobject *kobj)
 175{
 176        struct elevator_queue *e;
 177
 178        e = container_of(kobj, struct elevator_queue, kobj);
 179        elevator_put(e->type);
 180        kfree(e);
 181}
 182
 183int elevator_init(struct request_queue *q, char *name)
 184{
 185        struct elevator_type *e = NULL;
 186        int err;
 187
 188        if (unlikely(q->elevator))
 189                return 0;
 190
 191        INIT_LIST_HEAD(&q->queue_head);
 192        q->last_merge = NULL;
 193        q->end_sector = 0;
 194        q->boundary_rq = NULL;
 195
 196        if (name) {
 197                e = elevator_get(name, true);
 198                if (!e)
 199                        return -EINVAL;
 200        }
 201
 202        /*
 203         * Use the default elevator specified by config boot param or
 204         * config option.  Don't try to load modules as we could be running
 205         * off async and request_module() isn't allowed from async.
 206         */
 207        if (!e && *chosen_elevator) {
 208                e = elevator_get(chosen_elevator, false);
 209                if (!e)
 210                        printk(KERN_ERR "I/O scheduler %s not found\n",
 211                                                        chosen_elevator);
 212        }
 213
 214        if (!e) {
 215                e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);
 216                if (!e) {
 217                        printk(KERN_ERR
 218                                "Default I/O scheduler not found. " \
 219                                "Using noop.\n");
 220                        e = elevator_get("noop", false);
 221                }
 222        }
 223
 224        q->elevator = elevator_alloc(q, e);
 225        if (!q->elevator)
 226                return -ENOMEM;
 227
 228        err = e->ops.elevator_init_fn(q);
 229        if (err) {
 230                kobject_put(&q->elevator->kobj);
 231                return err;
 232        }
 233
 234        return 0;
 235}
 236EXPORT_SYMBOL(elevator_init);
 237
 238void elevator_exit(struct elevator_queue *e)
 239{
 240        mutex_lock(&e->sysfs_lock);
 241        if (e->type->ops.elevator_exit_fn)
 242                e->type->ops.elevator_exit_fn(e);
 243        mutex_unlock(&e->sysfs_lock);
 244
 245        kobject_put(&e->kobj);
 246}
 247EXPORT_SYMBOL(elevator_exit);
 248
 249static inline void __elv_rqhash_del(struct request *rq)
 250{
 251        hash_del(&rq->hash);
 252}
 253
 254static void elv_rqhash_del(struct request_queue *q, struct request *rq)
 255{
 256        if (ELV_ON_HASH(rq))
 257                __elv_rqhash_del(rq);
 258}
 259
 260static void elv_rqhash_add(struct request_queue *q, struct request *rq)
 261{
 262        struct elevator_queue *e = q->elevator;
 263
 264        BUG_ON(ELV_ON_HASH(rq));
 265        hash_add(e->hash, &rq->hash, rq_hash_key(rq));
 266}
 267
 268static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
 269{
 270        __elv_rqhash_del(rq);
 271        elv_rqhash_add(q, rq);
 272}
 273
 274static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
 275{
 276        struct elevator_queue *e = q->elevator;
 277        struct hlist_node *next;
 278        struct request *rq;
 279
 280        hash_for_each_possible_safe(e->hash, rq, next, hash, offset) {
 281                BUG_ON(!ELV_ON_HASH(rq));
 282
 283                if (unlikely(!rq_mergeable(rq))) {
 284                        __elv_rqhash_del(rq);
 285                        continue;
 286                }
 287
 288                if (rq_hash_key(rq) == offset)
 289                        return rq;
 290        }
 291
 292        return NULL;
 293}
 294
 295/*
 296 * RB-tree support functions for inserting/lookup/removal of requests
 297 * in a sorted RB tree.
 298 */
 299void elv_rb_add(struct rb_root *root, struct request *rq)
 300{
 301        struct rb_node **p = &root->rb_node;
 302        struct rb_node *parent = NULL;
 303        struct request *__rq;
 304
 305        while (*p) {
 306                parent = *p;
 307                __rq = rb_entry(parent, struct request, rb_node);
 308
 309                if (blk_rq_pos(rq) < blk_rq_pos(__rq))
 310                        p = &(*p)->rb_left;
 311                else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
 312                        p = &(*p)->rb_right;
 313        }
 314
 315        rb_link_node(&rq->rb_node, parent, p);
 316        rb_insert_color(&rq->rb_node, root);
 317}
 318EXPORT_SYMBOL(elv_rb_add);
 319
 320void elv_rb_del(struct rb_root *root, struct request *rq)
 321{
 322        BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
 323        rb_erase(&rq->rb_node, root);
 324        RB_CLEAR_NODE(&rq->rb_node);
 325}
 326EXPORT_SYMBOL(elv_rb_del);
 327
 328struct request *elv_rb_find(struct rb_root *root, sector_t sector)
 329{
 330        struct rb_node *n = root->rb_node;
 331        struct request *rq;
 332
 333        while (n) {
 334                rq = rb_entry(n, struct request, rb_node);
 335
 336                if (sector < blk_rq_pos(rq))
 337                        n = n->rb_left;
 338                else if (sector > blk_rq_pos(rq))
 339                        n = n->rb_right;
 340                else
 341                        return rq;
 342        }
 343
 344        return NULL;
 345}
 346EXPORT_SYMBOL(elv_rb_find);
 347
 348/*
 349 * Insert rq into dispatch queue of q.  Queue lock must be held on
 350 * entry.  rq is sort instead into the dispatch queue. To be used by
 351 * specific elevators.
 352 */
 353void elv_dispatch_sort(struct request_queue *q, struct request *rq)
 354{
 355        sector_t boundary;
 356        struct list_head *entry;
 357        int stop_flags;
 358
 359        if (q->last_merge == rq)
 360                q->last_merge = NULL;
 361
 362        elv_rqhash_del(q, rq);
 363
 364        q->nr_sorted--;
 365
 366        boundary = q->end_sector;
 367        stop_flags = REQ_SOFTBARRIER | REQ_STARTED;
 368        list_for_each_prev(entry, &q->queue_head) {
 369                struct request *pos = list_entry_rq(entry);
 370
 371                if ((rq->cmd_flags & REQ_DISCARD) !=
 372                    (pos->cmd_flags & REQ_DISCARD))
 373                        break;
 374                if (rq_data_dir(rq) != rq_data_dir(pos))
 375                        break;
 376                if (pos->cmd_flags & stop_flags)
 377                        break;
 378                if (blk_rq_pos(rq) >= boundary) {
 379                        if (blk_rq_pos(pos) < boundary)
 380                                continue;
 381                } else {
 382                        if (blk_rq_pos(pos) >= boundary)
 383                                break;
 384                }
 385                if (blk_rq_pos(rq) >= blk_rq_pos(pos))
 386                        break;
 387        }
 388
 389        list_add(&rq->queuelist, entry);
 390}
 391EXPORT_SYMBOL(elv_dispatch_sort);
 392
 393/*
 394 * Insert rq into dispatch queue of q.  Queue lock must be held on
 395 * entry.  rq is added to the back of the dispatch queue. To be used by
 396 * specific elevators.
 397 */
 398void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
 399{
 400        if (q->last_merge == rq)
 401                q->last_merge = NULL;
 402
 403        elv_rqhash_del(q, rq);
 404
 405        q->nr_sorted--;
 406
 407        q->end_sector = rq_end_sector(rq);
 408        q->boundary_rq = rq;
 409        list_add_tail(&rq->queuelist, &q->queue_head);
 410}
 411EXPORT_SYMBOL(elv_dispatch_add_tail);
 412
 413int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
 414{
 415        struct elevator_queue *e = q->elevator;
 416        struct request *__rq;
 417        int ret;
 418
 419        /*
 420         * Levels of merges:
 421         *      nomerges:  No merges at all attempted
 422         *      noxmerges: Only simple one-hit cache try
 423         *      merges:    All merge tries attempted
 424         */
 425        if (blk_queue_nomerges(q))
 426                return ELEVATOR_NO_MERGE;
 427
 428        /*
 429         * First try one-hit cache.
 430         */
 431        if (q->last_merge && elv_rq_merge_ok(q->last_merge, bio)) {
 432                ret = blk_try_merge(q->last_merge, bio);
 433                if (ret != ELEVATOR_NO_MERGE) {
 434                        *req = q->last_merge;
 435                        return ret;
 436                }
 437        }
 438
 439        if (blk_queue_noxmerges(q))
 440                return ELEVATOR_NO_MERGE;
 441
 442        /*
 443         * See if our hash lookup can find a potential backmerge.
 444         */
 445        __rq = elv_rqhash_find(q, bio->bi_sector);
 446        if (__rq && elv_rq_merge_ok(__rq, bio)) {
 447                *req = __rq;
 448                return ELEVATOR_BACK_MERGE;
 449        }
 450
 451        if (e->type->ops.elevator_merge_fn)
 452                return e->type->ops.elevator_merge_fn(q, req, bio);
 453
 454        return ELEVATOR_NO_MERGE;
 455}
 456
 457/*
 458 * Attempt to do an insertion back merge. Only check for the case where
 459 * we can append 'rq' to an existing request, so we can throw 'rq' away
 460 * afterwards.
 461 *
 462 * Returns true if we merged, false otherwise
 463 */
 464static bool elv_attempt_insert_merge(struct request_queue *q,
 465                                     struct request *rq)
 466{
 467        struct request *__rq;
 468        bool ret;
 469
 470        if (blk_queue_nomerges(q))
 471                return false;
 472
 473        /*
 474         * First try one-hit cache.
 475         */
 476        if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq))
 477                return true;
 478
 479        if (blk_queue_noxmerges(q))
 480                return false;
 481
 482        ret = false;
 483        /*
 484         * See if our hash lookup can find a potential backmerge.
 485         */
 486        while (1) {
 487                __rq = elv_rqhash_find(q, blk_rq_pos(rq));
 488                if (!__rq || !blk_attempt_req_merge(q, __rq, rq))
 489                        break;
 490
 491                /* The merged request could be merged with others, try again */
 492                ret = true;
 493                rq = __rq;
 494        }
 495
 496        return ret;
 497}
 498
 499void elv_merged_request(struct request_queue *q, struct request *rq, int type)
 500{
 501        struct elevator_queue *e = q->elevator;
 502
 503        if (e->type->ops.elevator_merged_fn)
 504                e->type->ops.elevator_merged_fn(q, rq, type);
 505
 506        if (type == ELEVATOR_BACK_MERGE)
 507                elv_rqhash_reposition(q, rq);
 508
 509        q->last_merge = rq;
 510}
 511
 512void elv_merge_requests(struct request_queue *q, struct request *rq,
 513                             struct request *next)
 514{
 515        struct elevator_queue *e = q->elevator;
 516        const int next_sorted = next->cmd_flags & REQ_SORTED;
 517
 518        if (next_sorted && e->type->ops.elevator_merge_req_fn)
 519                e->type->ops.elevator_merge_req_fn(q, rq, next);
 520
 521        elv_rqhash_reposition(q, rq);
 522
 523        if (next_sorted) {
 524                elv_rqhash_del(q, next);
 525                q->nr_sorted--;
 526        }
 527
 528        q->last_merge = rq;
 529}
 530
 531void elv_bio_merged(struct request_queue *q, struct request *rq,
 532                        struct bio *bio)
 533{
 534        struct elevator_queue *e = q->elevator;
 535
 536        if (e->type->ops.elevator_bio_merged_fn)
 537                e->type->ops.elevator_bio_merged_fn(q, rq, bio);
 538}
 539
 540#ifdef CONFIG_PM_RUNTIME
 541static void blk_pm_requeue_request(struct request *rq)
 542{
 543        if (rq->q->dev && !(rq->cmd_flags & REQ_PM))
 544                rq->q->nr_pending--;
 545}
 546
 547static void blk_pm_add_request(struct request_queue *q, struct request *rq)
 548{
 549        if (q->dev && !(rq->cmd_flags & REQ_PM) && q->nr_pending++ == 0 &&
 550            (q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING))
 551                pm_request_resume(q->dev);
 552}
 553#else
 554static inline void blk_pm_requeue_request(struct request *rq) {}
 555static inline void blk_pm_add_request(struct request_queue *q,
 556                                      struct request *rq)
 557{
 558}
 559#endif
 560
 561void elv_requeue_request(struct request_queue *q, struct request *rq)
 562{
 563        /*
 564         * it already went through dequeue, we need to decrement the
 565         * in_flight count again
 566         */
 567        if (blk_account_rq(rq)) {
 568                q->in_flight[rq_is_sync(rq)]--;
 569                if (rq->cmd_flags & REQ_SORTED)
 570                        elv_deactivate_rq(q, rq);
 571        }
 572
 573        rq->cmd_flags &= ~REQ_STARTED;
 574
 575        blk_pm_requeue_request(rq);
 576
 577        __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
 578}
 579
 580void elv_drain_elevator(struct request_queue *q)
 581{
 582        static int printed;
 583
 584        lockdep_assert_held(q->queue_lock);
 585
 586        while (q->elevator->type->ops.elevator_dispatch_fn(q, 1))
 587                ;
 588        if (q->nr_sorted && printed++ < 10) {
 589                printk(KERN_ERR "%s: forced dispatching is broken "
 590                       "(nr_sorted=%u), please report this\n",
 591                       q->elevator->type->elevator_name, q->nr_sorted);
 592        }
 593}
 594
 595void __elv_add_request(struct request_queue *q, struct request *rq, int where)
 596{
 597        trace_block_rq_insert(q, rq);
 598
 599        blk_pm_add_request(q, rq);
 600
 601        rq->q = q;
 602
 603        if (rq->cmd_flags & REQ_SOFTBARRIER) {
 604                /* barriers are scheduling boundary, update end_sector */
 605                if (rq->cmd_type == REQ_TYPE_FS) {
 606                        q->end_sector = rq_end_sector(rq);
 607                        q->boundary_rq = rq;
 608                }
 609        } else if (!(rq->cmd_flags & REQ_ELVPRIV) &&
 610                    (where == ELEVATOR_INSERT_SORT ||
 611                     where == ELEVATOR_INSERT_SORT_MERGE))
 612                where = ELEVATOR_INSERT_BACK;
 613
 614        switch (where) {
 615        case ELEVATOR_INSERT_REQUEUE:
 616        case ELEVATOR_INSERT_FRONT:
 617                rq->cmd_flags |= REQ_SOFTBARRIER;
 618                list_add(&rq->queuelist, &q->queue_head);
 619                break;
 620
 621        case ELEVATOR_INSERT_BACK:
 622                rq->cmd_flags |= REQ_SOFTBARRIER;
 623                elv_drain_elevator(q);
 624                list_add_tail(&rq->queuelist, &q->queue_head);
 625                /*
 626                 * We kick the queue here for the following reasons.
 627                 * - The elevator might have returned NULL previously
 628                 *   to delay requests and returned them now.  As the
 629                 *   queue wasn't empty before this request, ll_rw_blk
 630                 *   won't run the queue on return, resulting in hang.
 631                 * - Usually, back inserted requests won't be merged
 632                 *   with anything.  There's no point in delaying queue
 633                 *   processing.
 634                 */
 635                __blk_run_queue(q);
 636                break;
 637
 638        case ELEVATOR_INSERT_SORT_MERGE:
 639                /*
 640                 * If we succeed in merging this request with one in the
 641                 * queue already, we are done - rq has now been freed,
 642                 * so no need to do anything further.
 643                 */
 644                if (elv_attempt_insert_merge(q, rq))
 645                        break;
 646        case ELEVATOR_INSERT_SORT:
 647                BUG_ON(rq->cmd_type != REQ_TYPE_FS);
 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->type->ops.elevator_add_req_fn(q, rq);
 662                break;
 663
 664        case ELEVATOR_INSERT_FLUSH:
 665                rq->cmd_flags |= REQ_SOFTBARRIER;
 666                blk_insert_flush(rq);
 667                break;
 668        default:
 669                printk(KERN_ERR "%s: bad insertion point %d\n",
 670                       __func__, where);
 671                BUG();
 672        }
 673}
 674EXPORT_SYMBOL(__elv_add_request);
 675
 676void elv_add_request(struct request_queue *q, struct request *rq, int where)
 677{
 678        unsigned long flags;
 679
 680        spin_lock_irqsave(q->queue_lock, flags);
 681        __elv_add_request(q, rq, where);
 682        spin_unlock_irqrestore(q->queue_lock, flags);
 683}
 684EXPORT_SYMBOL(elv_add_request);
 685
 686struct request *elv_latter_request(struct request_queue *q, struct request *rq)
 687{
 688        struct elevator_queue *e = q->elevator;
 689
 690        if (e->type->ops.elevator_latter_req_fn)
 691                return e->type->ops.elevator_latter_req_fn(q, rq);
 692        return NULL;
 693}
 694
 695struct request *elv_former_request(struct request_queue *q, struct request *rq)
 696{
 697        struct elevator_queue *e = q->elevator;
 698
 699        if (e->type->ops.elevator_former_req_fn)
 700                return e->type->ops.elevator_former_req_fn(q, rq);
 701        return NULL;
 702}
 703
 704int elv_set_request(struct request_queue *q, struct request *rq,
 705                    struct bio *bio, gfp_t gfp_mask)
 706{
 707        struct elevator_queue *e = q->elevator;
 708
 709        if (e->type->ops.elevator_set_req_fn)
 710                return e->type->ops.elevator_set_req_fn(q, rq, bio, gfp_mask);
 711        return 0;
 712}
 713
 714void elv_put_request(struct request_queue *q, struct request *rq)
 715{
 716        struct elevator_queue *e = q->elevator;
 717
 718        if (e->type->ops.elevator_put_req_fn)
 719                e->type->ops.elevator_put_req_fn(rq);
 720}
 721
 722int elv_may_queue(struct request_queue *q, int rw)
 723{
 724        struct elevator_queue *e = q->elevator;
 725
 726        if (e->type->ops.elevator_may_queue_fn)
 727                return e->type->ops.elevator_may_queue_fn(q, rw);
 728
 729        return ELV_MQUEUE_MAY;
 730}
 731
 732void elv_abort_queue(struct request_queue *q)
 733{
 734        struct request *rq;
 735
 736        blk_abort_flushes(q);
 737
 738        while (!list_empty(&q->queue_head)) {
 739                rq = list_entry_rq(q->queue_head.next);
 740                rq->cmd_flags |= REQ_QUIET;
 741                trace_block_rq_abort(q, rq);
 742                /*
 743                 * Mark this request as started so we don't trigger
 744                 * any debug logic in the end I/O path.
 745                 */
 746                blk_start_request(rq);
 747                __blk_end_request_all(rq, -EIO);
 748        }
 749}
 750EXPORT_SYMBOL(elv_abort_queue);
 751
 752void elv_completed_request(struct request_queue *q, struct request *rq)
 753{
 754        struct elevator_queue *e = q->elevator;
 755
 756        /*
 757         * request is released from the driver, io must be done
 758         */
 759        if (blk_account_rq(rq)) {
 760                q->in_flight[rq_is_sync(rq)]--;
 761                if ((rq->cmd_flags & REQ_SORTED) &&
 762                    e->type->ops.elevator_completed_req_fn)
 763                        e->type->ops.elevator_completed_req_fn(q, rq);
 764        }
 765}
 766
 767#define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
 768
 769static ssize_t
 770elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
 771{
 772        struct elv_fs_entry *entry = to_elv(attr);
 773        struct elevator_queue *e;
 774        ssize_t error;
 775
 776        if (!entry->show)
 777                return -EIO;
 778
 779        e = container_of(kobj, struct elevator_queue, kobj);
 780        mutex_lock(&e->sysfs_lock);
 781        error = e->type ? entry->show(e, page) : -ENOENT;
 782        mutex_unlock(&e->sysfs_lock);
 783        return error;
 784}
 785
 786static ssize_t
 787elv_attr_store(struct kobject *kobj, struct attribute *attr,
 788               const char *page, size_t length)
 789{
 790        struct elv_fs_entry *entry = to_elv(attr);
 791        struct elevator_queue *e;
 792        ssize_t error;
 793
 794        if (!entry->store)
 795                return -EIO;
 796
 797        e = container_of(kobj, struct elevator_queue, kobj);
 798        mutex_lock(&e->sysfs_lock);
 799        error = e->type ? entry->store(e, page, length) : -ENOENT;
 800        mutex_unlock(&e->sysfs_lock);
 801        return error;
 802}
 803
 804static const struct sysfs_ops elv_sysfs_ops = {
 805        .show   = elv_attr_show,
 806        .store  = elv_attr_store,
 807};
 808
 809static struct kobj_type elv_ktype = {
 810        .sysfs_ops      = &elv_sysfs_ops,
 811        .release        = elevator_release,
 812};
 813
 814int elv_register_queue(struct request_queue *q)
 815{
 816        struct elevator_queue *e = q->elevator;
 817        int error;
 818
 819        error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
 820        if (!error) {
 821                struct elv_fs_entry *attr = e->type->elevator_attrs;
 822                if (attr) {
 823                        while (attr->attr.name) {
 824                                if (sysfs_create_file(&e->kobj, &attr->attr))
 825                                        break;
 826                                attr++;
 827                        }
 828                }
 829                kobject_uevent(&e->kobj, KOBJ_ADD);
 830                e->registered = 1;
 831        }
 832        return error;
 833}
 834EXPORT_SYMBOL(elv_register_queue);
 835
 836void elv_unregister_queue(struct request_queue *q)
 837{
 838        if (q) {
 839                struct elevator_queue *e = q->elevator;
 840
 841                kobject_uevent(&e->kobj, KOBJ_REMOVE);
 842                kobject_del(&e->kobj);
 843                e->registered = 0;
 844        }
 845}
 846EXPORT_SYMBOL(elv_unregister_queue);
 847
 848int elv_register(struct elevator_type *e)
 849{
 850        char *def = "";
 851
 852        /* create icq_cache if requested */
 853        if (e->icq_size) {
 854                if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
 855                    WARN_ON(e->icq_align < __alignof__(struct io_cq)))
 856                        return -EINVAL;
 857
 858                snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
 859                         "%s_io_cq", e->elevator_name);
 860                e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
 861                                                 e->icq_align, 0, NULL);
 862                if (!e->icq_cache)
 863                        return -ENOMEM;
 864        }
 865
 866        /* register, don't allow duplicate names */
 867        spin_lock(&elv_list_lock);
 868        if (elevator_find(e->elevator_name)) {
 869                spin_unlock(&elv_list_lock);
 870                if (e->icq_cache)
 871                        kmem_cache_destroy(e->icq_cache);
 872                return -EBUSY;
 873        }
 874        list_add_tail(&e->list, &elv_list);
 875        spin_unlock(&elv_list_lock);
 876
 877        /* print pretty message */
 878        if (!strcmp(e->elevator_name, chosen_elevator) ||
 879                        (!*chosen_elevator &&
 880                         !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
 881                                def = " (default)";
 882
 883        printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
 884                                                                def);
 885        return 0;
 886}
 887EXPORT_SYMBOL_GPL(elv_register);
 888
 889void elv_unregister(struct elevator_type *e)
 890{
 891        /* unregister */
 892        spin_lock(&elv_list_lock);
 893        list_del_init(&e->list);
 894        spin_unlock(&elv_list_lock);
 895
 896        /*
 897         * Destroy icq_cache if it exists.  icq's are RCU managed.  Make
 898         * sure all RCU operations are complete before proceeding.
 899         */
 900        if (e->icq_cache) {
 901                rcu_barrier();
 902                kmem_cache_destroy(e->icq_cache);
 903                e->icq_cache = NULL;
 904        }
 905}
 906EXPORT_SYMBOL_GPL(elv_unregister);
 907
 908/*
 909 * switch to new_e io scheduler. be careful not to introduce deadlocks -
 910 * we don't free the old io scheduler, before we have allocated what we
 911 * need for the new one. this way we have a chance of going back to the old
 912 * one, if the new one fails init for some reason.
 913 */
 914static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 915{
 916        struct elevator_queue *old = q->elevator;
 917        bool registered = old->registered;
 918        int err;
 919
 920        /*
 921         * Turn on BYPASS and drain all requests w/ elevator private data.
 922         * Block layer doesn't call into a quiesced elevator - all requests
 923         * are directly put on the dispatch list without elevator data
 924         * using INSERT_BACK.  All requests have SOFTBARRIER set and no
 925         * merge happens either.
 926         */
 927        blk_queue_bypass_start(q);
 928
 929        /* unregister and clear all auxiliary data of the old elevator */
 930        if (registered)
 931                elv_unregister_queue(q);
 932
 933        spin_lock_irq(q->queue_lock);
 934        ioc_clear_queue(q);
 935        spin_unlock_irq(q->queue_lock);
 936
 937        /* allocate, init and register new elevator */
 938        err = -ENOMEM;
 939        q->elevator = elevator_alloc(q, new_e);
 940        if (!q->elevator)
 941                goto fail_init;
 942
 943        err = new_e->ops.elevator_init_fn(q);
 944        if (err) {
 945                kobject_put(&q->elevator->kobj);
 946                goto fail_init;
 947        }
 948
 949        if (registered) {
 950                err = elv_register_queue(q);
 951                if (err)
 952                        goto fail_register;
 953        }
 954
 955        /* done, kill the old one and finish */
 956        elevator_exit(old);
 957        blk_queue_bypass_end(q);
 958
 959        blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
 960
 961        return 0;
 962
 963fail_register:
 964        elevator_exit(q->elevator);
 965fail_init:
 966        /* switch failed, restore and re-register old elevator */
 967        q->elevator = old;
 968        elv_register_queue(q);
 969        blk_queue_bypass_end(q);
 970
 971        return err;
 972}
 973
 974/*
 975 * Switch this queue to the given IO scheduler.
 976 */
 977int elevator_change(struct request_queue *q, const char *name)
 978{
 979        char elevator_name[ELV_NAME_MAX];
 980        struct elevator_type *e;
 981
 982        if (!q->elevator)
 983                return -ENXIO;
 984
 985        strlcpy(elevator_name, name, sizeof(elevator_name));
 986        e = elevator_get(strstrip(elevator_name), true);
 987        if (!e) {
 988                printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
 989                return -EINVAL;
 990        }
 991
 992        if (!strcmp(elevator_name, q->elevator->type->elevator_name)) {
 993                elevator_put(e);
 994                return 0;
 995        }
 996
 997        return elevator_switch(q, e);
 998}
 999EXPORT_SYMBOL(elevator_change);
1000
1001ssize_t elv_iosched_store(struct request_queue *q, const char *name,
1002                          size_t count)
1003{
1004        int ret;
1005
1006        if (!q->elevator)
1007                return count;
1008
1009        ret = elevator_change(q, name);
1010        if (!ret)
1011                return count;
1012
1013        printk(KERN_ERR "elevator: switch to %s failed\n", name);
1014        return ret;
1015}
1016
1017ssize_t elv_iosched_show(struct request_queue *q, char *name)
1018{
1019        struct elevator_queue *e = q->elevator;
1020        struct elevator_type *elv;
1021        struct elevator_type *__e;
1022        int len = 0;
1023
1024        if (!q->elevator || !blk_queue_stackable(q))
1025                return sprintf(name, "none\n");
1026
1027        elv = e->type;
1028
1029        spin_lock(&elv_list_lock);
1030        list_for_each_entry(__e, &elv_list, list) {
1031                if (!strcmp(elv->elevator_name, __e->elevator_name))
1032                        len += sprintf(name+len, "[%s] ", elv->elevator_name);
1033                else
1034                        len += sprintf(name+len, "%s ", __e->elevator_name);
1035        }
1036        spin_unlock(&elv_list_lock);
1037
1038        len += sprintf(len+name, "\n");
1039        return len;
1040}
1041
1042struct request *elv_rb_former_request(struct request_queue *q,
1043                                      struct request *rq)
1044{
1045        struct rb_node *rbprev = rb_prev(&rq->rb_node);
1046
1047        if (rbprev)
1048                return rb_entry_rq(rbprev);
1049
1050        return NULL;
1051}
1052EXPORT_SYMBOL(elv_rb_former_request);
1053
1054struct request *elv_rb_latter_request(struct request_queue *q,
1055                                      struct request *rq)
1056{
1057        struct rb_node *rbnext = rb_next(&rq->rb_node);
1058
1059        if (rbnext)
1060                return rb_entry_rq(rbnext);
1061
1062        return NULL;
1063}
1064EXPORT_SYMBOL(elv_rb_latter_request);
1065
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.