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/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
  43static DEFINE_SPINLOCK(elv_list_lock);
  44static LIST_HEAD(elv_list);
  45
  46/*
  47 * Merge hash stuff.
  48 */
  49static 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 */
  60static 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 */
  74int 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}
 109EXPORT_SYMBOL(elv_rq_merge_ok);
 110
 111static 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
 128static 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
 140static void elevator_put(struct elevator_type *e)
 141{
 142        module_put(e->elevator_owner);
 143}
 144
 145static 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                sprintf(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
 172static void *elevator_init_queue(struct request_queue *q,
 173                                 struct elevator_queue *eq)
 174{
 175        return eq->ops->elevator_init_fn(q);
 176}
 177
 178static 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
 185static char chosen_elevator[16];
 186
 187static 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
 199static struct kobj_type elv_ktype;
 200
 201static 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;
 225err:
 226        kfree(eq);
 227        elevator_put(e);
 228        return NULL;
 229}
 230
 231static 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
 241int elevator_init(struct request_queue *q, char *name)
 242{
 243        struct elevator_type *e = NULL;
 244        struct elevator_queue *eq;
 245        int ret = 0;
 246        void *data;
 247
 248        INIT_LIST_HEAD(&q->queue_head);
 249        q->last_merge = NULL;
 250        q->end_sector = 0;
 251        q->boundary_rq = NULL;
 252
 253        if (name) {
 254                e = elevator_get(name);
 255                if (!e)
 256                        return -EINVAL;
 257        }
 258
 259        if (!e && *chosen_elevator) {
 260                e = elevator_get(chosen_elevator);
 261                if (!e)
 262                        printk(KERN_ERR "I/O scheduler %s not found\n",
 263                                                        chosen_elevator);
 264        }
 265
 266        if (!e) {
 267                e = elevator_get(CONFIG_DEFAULT_IOSCHED);
 268                if (!e) {
 269                        printk(KERN_ERR
 270                                "Default I/O scheduler not found. " \
 271                                "Using noop.\n");
 272                        e = elevator_get("noop");
 273                }
 274        }
 275
 276        eq = elevator_alloc(q, e);
 277        if (!eq)
 278                return -ENOMEM;
 279
 280        data = elevator_init_queue(q, eq);
 281        if (!data) {
 282                kobject_put(&eq->kobj);
 283                return -ENOMEM;
 284        }
 285
 286        elevator_attach(q, eq, data);
 287        return ret;
 288}
 289EXPORT_SYMBOL(elevator_init);
 290
 291void elevator_exit(struct elevator_queue *e)
 292{
 293        mutex_lock(&e->sysfs_lock);
 294        if (e->ops->elevator_exit_fn)
 295                e->ops->elevator_exit_fn(e);
 296        e->ops = NULL;
 297        mutex_unlock(&e->sysfs_lock);
 298
 299        kobject_put(&e->kobj);
 300}
 301EXPORT_SYMBOL(elevator_exit);
 302
 303static inline void __elv_rqhash_del(struct request *rq)
 304{
 305        hlist_del_init(&rq->hash);
 306}
 307
 308static void elv_rqhash_del(struct request_queue *q, struct request *rq)
 309{
 310        if (ELV_ON_HASH(rq))
 311                __elv_rqhash_del(rq);
 312}
 313
 314static void elv_rqhash_add(struct request_queue *q, struct request *rq)
 315{
 316        struct elevator_queue *e = q->elevator;
 317
 318        BUG_ON(ELV_ON_HASH(rq));
 319        hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
 320}
 321
 322static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
 323{
 324        __elv_rqhash_del(rq);
 325        elv_rqhash_add(q, rq);
 326}
 327
 328static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
 329{
 330        struct elevator_queue *e = q->elevator;
 331        struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
 332        struct hlist_node *entry, *next;
 333        struct request *rq;
 334
 335        hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
 336                BUG_ON(!ELV_ON_HASH(rq));
 337
 338                if (unlikely(!rq_mergeable(rq))) {
 339                        __elv_rqhash_del(rq);
 340                        continue;
 341                }
 342
 343                if (rq_hash_key(rq) == offset)
 344                        return rq;
 345        }
 346
 347        return NULL;
 348}
 349
 350/*
 351 * RB-tree support functions for inserting/lookup/removal of requests
 352 * in a sorted RB tree.
 353 */
 354struct request *elv_rb_add(struct rb_root *root, struct request *rq)
 355{
 356        struct rb_node **p = &root->rb_node;
 357        struct rb_node *parent = NULL;
 358        struct request *__rq;
 359
 360        while (*p) {
 361                parent = *p;
 362                __rq = rb_entry(parent, struct request, rb_node);
 363
 364                if (blk_rq_pos(rq) < blk_rq_pos(__rq))
 365                        p = &(*p)->rb_left;
 366                else if (blk_rq_pos(rq) > blk_rq_pos(__rq))
 367                        p = &(*p)->rb_right;
 368                else
 369                        return __rq;
 370        }
 371
 372        rb_link_node(&rq->rb_node, parent, p);
 373        rb_insert_color(&rq->rb_node, root);
 374        return NULL;
 375}
 376EXPORT_SYMBOL(elv_rb_add);
 377
 378void elv_rb_del(struct rb_root *root, struct request *rq)
 379{
 380        BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
 381        rb_erase(&rq->rb_node, root);
 382        RB_CLEAR_NODE(&rq->rb_node);
 383}
 384EXPORT_SYMBOL(elv_rb_del);
 385
 386struct request *elv_rb_find(struct rb_root *root, sector_t sector)
 387{
 388        struct rb_node *n = root->rb_node;
 389        struct request *rq;
 390
 391        while (n) {
 392                rq = rb_entry(n, struct request, rb_node);
 393
 394                if (sector < blk_rq_pos(rq))
 395                        n = n->rb_left;
 396                else if (sector > blk_rq_pos(rq))
 397                        n = n->rb_right;
 398                else
 399                        return rq;
 400        }
 401
 402        return NULL;
 403}
 404EXPORT_SYMBOL(elv_rb_find);
 405
 406/*
 407 * Insert rq into dispatch queue of q.  Queue lock must be held on
 408 * entry.  rq is sort instead into the dispatch queue. To be used by
 409 * specific elevators.
 410 */
 411void elv_dispatch_sort(struct request_queue *q, struct request *rq)
 412{
 413        sector_t boundary;
 414        struct list_head *entry;
 415        int stop_flags;
 416
 417        if (q->last_merge == rq)
 418                q->last_merge = NULL;
 419
 420        elv_rqhash_del(q, rq);
 421
 422        q->nr_sorted--;
 423
 424        boundary = q->end_sector;
 425        stop_flags = REQ_SOFTBARRIER | REQ_HARDBARRIER | REQ_STARTED;
 426        list_for_each_prev(entry, &q->queue_head) {
 427                struct request *pos = list_entry_rq(entry);
 428
 429                if (blk_discard_rq(rq) != blk_discard_rq(pos))
 430                        break;
 431                if (rq_data_dir(rq) != rq_data_dir(pos))
 432                        break;
 433                if (pos->cmd_flags & stop_flags)
 434                        break;
 435                if (blk_rq_pos(rq) >= boundary) {
 436                        if (blk_rq_pos(pos) < boundary)
 437                                continue;
 438                } else {
 439                        if (blk_rq_pos(pos) >= boundary)
 440                                break;
 441                }
 442                if (blk_rq_pos(rq) >= blk_rq_pos(pos))
 443                        break;
 444        }
 445
 446        list_add(&rq->queuelist, entry);
 447}
 448EXPORT_SYMBOL(elv_dispatch_sort);
 449
 450/*
 451 * Insert rq into dispatch queue of q.  Queue lock must be held on
 452 * entry.  rq is added to the back of the dispatch queue. To be used by
 453 * specific elevators.
 454 */
 455void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
 456{
 457        if (q->last_merge == rq)
 458                q->last_merge = NULL;
 459
 460        elv_rqhash_del(q, rq);
 461
 462        q->nr_sorted--;
 463
 464        q->end_sector = rq_end_sector(rq);
 465        q->boundary_rq = rq;
 466        list_add_tail(&rq->queuelist, &q->queue_head);
 467}
 468EXPORT_SYMBOL(elv_dispatch_add_tail);
 469
 470int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
 471{
 472        struct elevator_queue *e = q->elevator;
 473        struct request *__rq;
 474        int ret;
 475
 476        /*
 477         * First try one-hit cache.
 478         */
 479        if (q->last_merge) {
 480                ret = elv_try_merge(q->last_merge, bio);
 481                if (ret != ELEVATOR_NO_MERGE) {
 482                        *req = q->last_merge;
 483                        return ret;
 484                }
 485        }
 486
 487        if (blk_queue_nomerges(q))
 488                return ELEVATOR_NO_MERGE;
 489
 490        /*
 491         * See if our hash lookup can find a potential backmerge.
 492         */
 493        __rq = elv_rqhash_find(q, bio->bi_sector);
 494        if (__rq && elv_rq_merge_ok(__rq, bio)) {
 495                *req = __rq;
 496                return ELEVATOR_BACK_MERGE;
 497        }
 498
 499        if (e->ops->elevator_merge_fn)
 500                return e->ops->elevator_merge_fn(q, req, bio);
 501
 502        return ELEVATOR_NO_MERGE;
 503}
 504
 505void elv_merged_request(struct request_queue *q, struct request *rq, int type)
 506{
 507        struct elevator_queue *e = q->elevator;
 508
 509        if (e->ops->elevator_merged_fn)
 510                e->ops->elevator_merged_fn(q, rq, type);
 511
 512        if (type == ELEVATOR_BACK_MERGE)
 513                elv_rqhash_reposition(q, rq);
 514
 515        q->last_merge = rq;
 516}
 517
 518void elv_merge_requests(struct request_queue *q, struct request *rq,
 519                             struct request *next)
 520{
 521        struct elevator_queue *e = q->elevator;
 522
 523        if (e->ops->elevator_merge_req_fn)
 524                e->ops->elevator_merge_req_fn(q, rq, next);
 525
 526        elv_rqhash_reposition(q, rq);
 527        elv_rqhash_del(q, next);
 528
 529        q->nr_sorted--;
 530        q->last_merge = rq;
 531}
 532
 533void elv_requeue_request(struct request_queue *q, struct request *rq)
 534{
 535        /*
 536         * it already went through dequeue, we need to decrement the
 537         * in_flight count again
 538         */
 539        if (blk_account_rq(rq)) {
 540                q->in_flight[rq_is_sync(rq)]--;
 541                if (blk_sorted_rq(rq))
 542                        elv_deactivate_rq(q, rq);
 543        }
 544
 545        rq->cmd_flags &= ~REQ_STARTED;
 546
 547        elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
 548}
 549
 550void elv_drain_elevator(struct request_queue *q)
 551{
 552        static int printed;
 553        while (q->elevator->ops->elevator_dispatch_fn(q, 1))
 554                ;
 555        if (q->nr_sorted == 0)
 556                return;
 557        if (printed++ < 10) {
 558                printk(KERN_ERR "%s: forced dispatching is broken "
 559                       "(nr_sorted=%u), please report this\n",
 560                       q->elevator->elevator_type->elevator_name, q->nr_sorted);
 561        }
 562}
 563
 564/*
 565 * Call with queue lock held, interrupts disabled
 566 */
 567void elv_quiesce_start(struct request_queue *q)
 568{
 569        if (!q->elevator)
 570                return;
 571
 572        queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
 573
 574        /*
 575         * make sure we don't have any requests in flight
 576         */
 577        elv_drain_elevator(q);
 578        while (q->rq.elvpriv) {
 579                __blk_run_queue(q);
 580                spin_unlock_irq(q->queue_lock);
 581                msleep(10);
 582                spin_lock_irq(q->queue_lock);
 583                elv_drain_elevator(q);
 584        }
 585}
 586
 587void elv_quiesce_end(struct request_queue *q)
 588{
 589        queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
 590}
 591
 592void elv_insert(struct request_queue *q, struct request *rq, int where)
 593{
 594        struct list_head *pos;
 595        unsigned ordseq;
 596        int unplug_it = 1;
 597
 598        trace_block_rq_insert(q, rq);
 599
 600        rq->q = q;
 601
 602        switch (where) {
 603        case ELEVATOR_INSERT_FRONT:
 604                rq->cmd_flags |= REQ_SOFTBARRIER;
 605
 606                list_add(&rq->queuelist, &q->queue_head);
 607                break;
 608
 609        case ELEVATOR_INSERT_BACK:
 610                rq->cmd_flags |= REQ_SOFTBARRIER;
 611                elv_drain_elevator(q);
 612                list_add_tail(&rq->queuelist, &q->queue_head);
 613                /*
 614                 * We kick the queue here for the following reasons.
 615                 * - The elevator might have returned NULL previously
 616                 *   to delay requests and returned them now.  As the
 617                 *   queue wasn't empty before this request, ll_rw_blk
 618                 *   won't run the queue on return, resulting in hang.
 619                 * - Usually, back inserted requests won't be merged
 620                 *   with anything.  There's no point in delaying queue
 621                 *   processing.
 622                 */
 623                __blk_run_queue(q);
 624                break;
 625
 626        case ELEVATOR_INSERT_SORT:
 627                BUG_ON(!blk_fs_request(rq) && !blk_discard_rq(rq));
 628                rq->cmd_flags |= REQ_SORTED;
 629                q->nr_sorted++;
 630                if (rq_mergeable(rq)) {
 631                        elv_rqhash_add(q, rq);
 632                        if (!q->last_merge)
 633                                q->last_merge = rq;
 634                }
 635
 636                /*
 637                 * Some ioscheds (cfq) run q->request_fn directly, so
 638                 * rq cannot be accessed after calling
 639                 * elevator_add_req_fn.
 640                 */
 641                q->elevator->ops->elevator_add_req_fn(q, rq);
 642                break;
 643
 644        case ELEVATOR_INSERT_REQUEUE:
 645                /*
 646                 * If ordered flush isn't in progress, we do front
 647                 * insertion; otherwise, requests should be requeued
 648                 * in ordseq order.
 649                 */
 650                rq->cmd_flags |= REQ_SOFTBARRIER;
 651
 652                /*
 653                 * Most requeues happen because of a busy condition,
 654                 * don't force unplug of the queue for that case.
 655                 */
 656                unplug_it = 0;
 657
 658                if (q->ordseq == 0) {
 659                        list_add(&rq->queuelist, &q->queue_head);
 660                        break;
 661                }
 662
 663                ordseq = blk_ordered_req_seq(rq);
 664
 665                list_for_each(pos, &q->queue_head) {
 666                        struct request *pos_rq = list_entry_rq(pos);
 667                        if (ordseq <= blk_ordered_req_seq(pos_rq))
 668                                break;
 669                }
 670
 671                list_add_tail(&rq->queuelist, pos);
 672                break;
 673
 674        default:
 675                printk(KERN_ERR "%s: bad insertion point %d\n",
 676                       __func__, where);
 677                BUG();
 678        }
 679
 680        if (unplug_it && blk_queue_plugged(q)) {
 681                int nrq = q->rq.count[BLK_RW_SYNC] + q->rq.count[BLK_RW_ASYNC]
 682                                - queue_in_flight(q);
 683
 684                if (nrq >= q->unplug_thresh)
 685                        __generic_unplug_device(q);
 686        }
 687}
 688
 689void __elv_add_request(struct request_queue *q, struct request *rq, int where,
 690                       int plug)
 691{
 692        if (q->ordcolor)
 693                rq->cmd_flags |= REQ_ORDERED_COLOR;
 694
 695        if (rq->cmd_flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
 696                /*
 697                 * toggle ordered color
 698                 */
 699                if (blk_barrier_rq(rq))
 700                        q->ordcolor ^= 1;
 701
 702                /*
 703                 * barriers implicitly indicate back insertion
 704                 */
 705                if (where == ELEVATOR_INSERT_SORT)
 706                        where = ELEVATOR_INSERT_BACK;
 707
 708                /*
 709                 * this request is scheduling boundary, update
 710                 * end_sector
 711                 */
 712                if (blk_fs_request(rq) || blk_discard_rq(rq)) {
 713                        q->end_sector = rq_end_sector(rq);
 714                        q->boundary_rq = rq;
 715                }
 716        } else if (!(rq->cmd_flags & REQ_ELVPRIV) &&
 717                    where == ELEVATOR_INSERT_SORT)
 718                where = ELEVATOR_INSERT_BACK;
 719
 720        if (plug)
 721                blk_plug_device(q);
 722
 723        elv_insert(q, rq, where);
 724}
 725EXPORT_SYMBOL(__elv_add_request);
 726
 727void elv_add_request(struct request_queue *q, struct request *rq, int where,
 728                     int plug)
 729{
 730        unsigned long flags;
 731
 732        spin_lock_irqsave(q->queue_lock, flags);
 733        __elv_add_request(q, rq, where, plug);
 734        spin_unlock_irqrestore(q->queue_lock, flags);
 735}
 736EXPORT_SYMBOL(elv_add_request);
 737
 738int elv_queue_empty(struct request_queue *q)
 739{
 740        struct elevator_queue *e = q->elevator;
 741
 742        if (!list_empty(&q->queue_head))
 743                return 0;
 744
 745        if (e->ops->elevator_queue_empty_fn)
 746                return e->ops->elevator_queue_empty_fn(q);
 747
 748        return 1;
 749}
 750EXPORT_SYMBOL(elv_queue_empty);
 751
 752struct request *elv_latter_request(struct request_queue *q, struct request *rq)
 753{
 754        struct elevator_queue *e = q->elevator;
 755
 756        if (e->ops->elevator_latter_req_fn)
 757                return e->ops->elevator_latter_req_fn(q, rq);
 758        return NULL;
 759}
 760
 761struct request *elv_former_request(struct request_queue *q, struct request *rq)
 762{
 763        struct elevator_queue *e = q->elevator;
 764
 765        if (e->ops->elevator_former_req_fn)
 766                return e->ops->elevator_former_req_fn(q, rq);
 767        return NULL;
 768}
 769
 770int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
 771{
 772        struct elevator_queue *e = q->elevator;
 773
 774        if (e->ops->elevator_set_req_fn)
 775                return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
 776
 777        rq->elevator_private = NULL;
 778        return 0;
 779}
 780
 781void elv_put_request(struct request_queue *q, struct request *rq)
 782{
 783        struct elevator_queue *e = q->elevator;
 784
 785        if (e->ops->elevator_put_req_fn)
 786                e->ops->elevator_put_req_fn(rq);
 787}
 788
 789int elv_may_queue(struct request_queue *q, int rw)
 790{
 791        struct elevator_queue *e = q->elevator;
 792
 793        if (e->ops->elevator_may_queue_fn)
 794                return e->ops->elevator_may_queue_fn(q, rw);
 795
 796        return ELV_MQUEUE_MAY;
 797}
 798
 799void elv_abort_queue(struct request_queue *q)
 800{
 801        struct request *rq;
 802
 803        while (!list_empty(&q->queue_head)) {
 804                rq = list_entry_rq(q->queue_head.next);
 805                rq->cmd_flags |= REQ_QUIET;
 806                trace_block_rq_abort(q, rq);
 807                /*
 808                 * Mark this request as started so we don't trigger
 809                 * any debug logic in the end I/O path.
 810                 */
 811                blk_start_request(rq);
 812                __blk_end_request_all(rq, -EIO);
 813        }
 814}
 815EXPORT_SYMBOL(elv_abort_queue);
 816
 817void elv_completed_request(struct request_queue *q, struct request *rq)
 818{
 819        struct elevator_queue *e = q->elevator;
 820
 821        /*
 822         * request is released from the driver, io must be done
 823         */
 824        if (blk_account_rq(rq)) {
 825                q->in_flight[rq_is_sync(rq)]--;
 826                if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
 827                        e->ops->elevator_completed_req_fn(q, rq);
 828        }
 829
 830        /*
 831         * Check if the queue is waiting for fs requests to be
 832         * drained for flush sequence.
 833         */
 834        if (unlikely(q->ordseq)) {
 835                struct request *next = NULL;
 836
 837                if (!list_empty(&q->queue_head))
 838                        next = list_entry_rq(q->queue_head.next);
 839
 840                if (!queue_in_flight(q) &&
 841                    blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
 842                    (!next || blk_ordered_req_seq(next) > QUEUE_ORDSEQ_DRAIN)) {
 843                        blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
 844                        __blk_run_queue(q);
 845                }
 846        }
 847}
 848
 849#define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
 850
 851static ssize_t
 852elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
 853{
 854        struct elv_fs_entry *entry = to_elv(attr);
 855        struct elevator_queue *e;
 856        ssize_t error;
 857
 858        if (!entry->show)
 859                return -EIO;
 860
 861        e = container_of(kobj, struct elevator_queue, kobj);
 862        mutex_lock(&e->sysfs_lock);
 863        error = e->ops ? entry->show(e, page) : -ENOENT;
 864        mutex_unlock(&e->sysfs_lock);
 865        return error;
 866}
 867
 868static ssize_t
 869elv_attr_store(struct kobject *kobj, struct attribute *attr,
 870               const char *page, size_t length)
 871{
 872        struct elv_fs_entry *entry = to_elv(attr);
 873        struct elevator_queue *e;
 874        ssize_t error;
 875
 876        if (!entry->store)
 877                return -EIO;
 878
 879        e = container_of(kobj, struct elevator_queue, kobj);
 880        mutex_lock(&e->sysfs_lock);
 881        error = e->ops ? entry->store(e, page, length) : -ENOENT;
 882        mutex_unlock(&e->sysfs_lock);
 883        return error;
 884}
 885
 886static struct sysfs_ops elv_sysfs_ops = {
 887        .show   = elv_attr_show,
 888        .store  = elv_attr_store,
 889};
 890
 891static struct kobj_type elv_ktype = {
 892        .sysfs_ops      = &elv_sysfs_ops,
 893        .release        = elevator_release,
 894};
 895
 896int elv_register_queue(struct request_queue *q)
 897{
 898        struct elevator_queue *e = q->elevator;
 899        int error;
 900
 901        error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
 902        if (!error) {
 903                struct elv_fs_entry *attr = e->elevator_type->elevator_attrs;
 904                if (attr) {
 905                        while (attr->attr.name) {
 906                                if (sysfs_create_file(&e->kobj, &attr->attr))
 907                                        break;
 908                                attr++;
 909                        }
 910                }
 911                kobject_uevent(&e->kobj, KOBJ_ADD);
 912        }
 913        return error;
 914}
 915
 916static void __elv_unregister_queue(struct elevator_queue *e)
 917{
 918        kobject_uevent(&e->kobj, KOBJ_REMOVE);
 919        kobject_del(&e->kobj);
 920}
 921
 922void elv_unregister_queue(struct request_queue *q)
 923{
 924        if (q)
 925                __elv_unregister_queue(q->elevator);
 926}
 927
 928void elv_register(struct elevator_type *e)
 929{
 930        char *def = "";
 931
 932        spin_lock(&elv_list_lock);
 933        BUG_ON(elevator_find(e->elevator_name));
 934        list_add_tail(&e->list, &elv_list);
 935        spin_unlock(&elv_list_lock);
 936
 937        if (!strcmp(e->elevator_name, chosen_elevator) ||
 938                        (!*chosen_elevator &&
 939                         !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
 940                                def = " (default)";
 941
 942        printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
 943                                                                def);
 944}
 945EXPORT_SYMBOL_GPL(elv_register);
 946
 947void elv_unregister(struct elevator_type *e)
 948{
 949        struct task_struct *g, *p;
 950
 951        /*
 952         * Iterate every thread in the process to remove the io contexts.
 953         */
 954        if (e->ops.trim) {
 955                read_lock(&tasklist_lock);
 956                do_each_thread(g, p) {
 957                        task_lock(p);
 958                        if (p->io_context)
 959                                e->ops.trim(p->io_context);
 960                        task_unlock(p);
 961                } while_each_thread(g, p);
 962                read_unlock(&tasklist_lock);
 963        }
 964
 965        spin_lock(&elv_list_lock);
 966        list_del_init(&e->list);
 967        spin_unlock(&elv_list_lock);
 968}
 969EXPORT_SYMBOL_GPL(elv_unregister);
 970
 971/*
 972 * switch to new_e io scheduler. be careful not to introduce deadlocks -
 973 * we don't free the old io scheduler, before we have allocated what we
 974 * need for the new one. this way we have a chance of going back to the old
 975 * one, if the new one fails init for some reason.
 976 */
 977static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 978{
 979        struct elevator_queue *old_elevator, *e;
 980        void *data;
 981
 982        /*
 983         * Allocate new elevator
 984         */
 985        e = elevator_alloc(q, new_e);
 986        if (!e)
 987                return 0;
 988
 989        data = elevator_init_queue(q, e);
 990        if (!data) {
 991                kobject_put(&e->kobj);
 992                return 0;
 993        }
 994
 995        /*
 996         * Turn on BYPASS and drain all requests w/ elevator private data
 997         */
 998        spin_lock_irq(q->queue_lock);
 999        elv_quiesce_start(q);
1000
1001        /*
1002         * Remember old elevator.
1003         */
1004        old_elevator = q->elevator;
1005
1006        /*
1007         * attach and start new elevator
1008         */
1009        elevator_attach(q, e, data);
1010
1011        spin_unlock_irq(q->queue_lock);
1012
1013        __elv_unregister_queue(old_elevator);
1014
1015        if (elv_register_queue(q))
1016                goto fail_register;
1017
1018        /*
1019         * finally exit old elevator and turn off BYPASS.
1020         */
1021        elevator_exit(old_elevator);
1022        spin_lock_irq(q->queue_lock);
1023        elv_quiesce_end(q);
1024        spin_unlock_irq(q->queue_lock);
1025
1026        blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name);
1027
1028        return 1;
1029
1030fail_register:
1031        /*
1032         * switch failed, exit the new io scheduler and reattach the old
1033         * one again (along with re-adding the sysfs dir)
1034         */
1035        elevator_exit(e);
1036        q->elevator = old_elevator;
1037        elv_register_queue(q);
1038
1039        spin_lock_irq(q->queue_lock);
1040        queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
1041        spin_unlock_irq(q->queue_lock);
1042
1043        return 0;
1044}
1045
1046ssize_t elv_iosched_store(struct request_queue *q, const char *name,
1047                          size_t count)
1048{
1049        char elevator_name[ELV_NAME_MAX];
1050        struct elevator_type *e;
1051
1052        if (!q->elevator)
1053                return count;
1054
1055        strlcpy(elevator_name, name, sizeof(elevator_name));
1056        e = elevator_get(strstrip(elevator_name));
1057        if (!e) {
1058                printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
1059                return -EINVAL;
1060        }
1061
1062        if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
1063                elevator_put(e);
1064                return count;
1065        }
1066
1067        if (!elevator_switch(q, e))
1068                printk(KERN_ERR "elevator: switch to %s failed\n",
1069                                                        elevator_name);
1070        return count;
1071}
1072
1073ssize_t elv_iosched_show(struct request_queue *q, char *name)
1074{
1075        struct elevator_queue *e = q->elevator;
1076        struct elevator_type *elv;
1077        struct elevator_type *__e;
1078        int len = 0;
1079
1080        if (!q->elevator)
1081                return sprintf(name, "none\n");
1082
1083        elv = e->elevator_type;
1084
1085        spin_lock(&elv_list_lock);
1086        list_for_each_entry(__e, &elv_list, list) {
1087                if (!strcmp(elv->elevator_name, __e->elevator_name))
1088                        len += sprintf(name+len, "[%s] ", elv->elevator_name);
1089                else
1090                        len += sprintf(name+len, "%s ", __e->elevator_name);
1091        }
1092        spin_unlock(&elv_list_lock);
1093
1094        len += sprintf(len+name, "\n");
1095        return len;
1096}
1097
1098struct request *elv_rb_former_request(struct request_queue *q,
1099                                      struct request *rq)
1100{
1101        struct rb_node *rbprev = rb_prev(&rq->rb_node);
1102
1103        if (rbprev)
1104                return rb_entry_rq(rbprev);
1105
1106        return NULL;
1107}
1108EXPORT_SYMBOL(elv_rb_former_request);
1109
1110struct request *elv_rb_latter_request(struct request_queue *q,
1111                                      struct request *rq)
1112{
1113        struct rb_node *rbnext = rb_next(&rq->rb_node);
1114
1115        if (rbnext)
1116                return rb_entry_rq(rbnext);
1117
1118        return NULL;
1119}
1120EXPORT_SYMBOL(elv_rb_latter_request);
1121
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.