linux/mm/backing-dev.c
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   1
   2#include <linux/wait.h>
   3#include <linux/backing-dev.h>
   4#include <linux/kthread.h>
   5#include <linux/freezer.h>
   6#include <linux/fs.h>
   7#include <linux/pagemap.h>
   8#include <linux/mm.h>
   9#include <linux/sched.h>
  10#include <linux/module.h>
  11#include <linux/writeback.h>
  12#include <linux/device.h>
  13#include <trace/events/writeback.h>
  14
  15static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
  16
  17struct backing_dev_info default_backing_dev_info = {
  18        .name           = "default",
  19        .ra_pages       = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
  20        .state          = 0,
  21        .capabilities   = BDI_CAP_MAP_COPY,
  22};
  23EXPORT_SYMBOL_GPL(default_backing_dev_info);
  24
  25struct backing_dev_info noop_backing_dev_info = {
  26        .name           = "noop",
  27        .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
  28};
  29EXPORT_SYMBOL_GPL(noop_backing_dev_info);
  30
  31static struct class *bdi_class;
  32
  33/*
  34 * bdi_lock protects updates to bdi_list and bdi_pending_list, as well as
  35 * reader side protection for bdi_pending_list. bdi_list has RCU reader side
  36 * locking.
  37 */
  38DEFINE_SPINLOCK(bdi_lock);
  39LIST_HEAD(bdi_list);
  40LIST_HEAD(bdi_pending_list);
  41
  42void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
  43{
  44        if (wb1 < wb2) {
  45                spin_lock(&wb1->list_lock);
  46                spin_lock_nested(&wb2->list_lock, 1);
  47        } else {
  48                spin_lock(&wb2->list_lock);
  49                spin_lock_nested(&wb1->list_lock, 1);
  50        }
  51}
  52
  53#ifdef CONFIG_DEBUG_FS
  54#include <linux/debugfs.h>
  55#include <linux/seq_file.h>
  56
  57static struct dentry *bdi_debug_root;
  58
  59static void bdi_debug_init(void)
  60{
  61        bdi_debug_root = debugfs_create_dir("bdi", NULL);
  62}
  63
  64static int bdi_debug_stats_show(struct seq_file *m, void *v)
  65{
  66        struct backing_dev_info *bdi = m->private;
  67        struct bdi_writeback *wb = &bdi->wb;
  68        unsigned long background_thresh;
  69        unsigned long dirty_thresh;
  70        unsigned long bdi_thresh;
  71        unsigned long nr_dirty, nr_io, nr_more_io;
  72        struct inode *inode;
  73
  74        nr_dirty = nr_io = nr_more_io = 0;
  75        spin_lock(&wb->list_lock);
  76        list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
  77                nr_dirty++;
  78        list_for_each_entry(inode, &wb->b_io, i_wb_list)
  79                nr_io++;
  80        list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
  81                nr_more_io++;
  82        spin_unlock(&wb->list_lock);
  83
  84        global_dirty_limits(&background_thresh, &dirty_thresh);
  85        bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
  86
  87#define K(x) ((x) << (PAGE_SHIFT - 10))
  88        seq_printf(m,
  89                   "BdiWriteback:       %10lu kB\n"
  90                   "BdiReclaimable:     %10lu kB\n"
  91                   "BdiDirtyThresh:     %10lu kB\n"
  92                   "DirtyThresh:        %10lu kB\n"
  93                   "BackgroundThresh:   %10lu kB\n"
  94                   "BdiDirtied:         %10lu kB\n"
  95                   "BdiWritten:         %10lu kB\n"
  96                   "BdiWriteBandwidth:  %10lu kBps\n"
  97                   "b_dirty:            %10lu\n"
  98                   "b_io:               %10lu\n"
  99                   "b_more_io:          %10lu\n"
 100                   "bdi_list:           %10u\n"
 101                   "state:              %10lx\n",
 102                   (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
 103                   (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
 104                   K(bdi_thresh),
 105                   K(dirty_thresh),
 106                   K(background_thresh),
 107                   (unsigned long) K(bdi_stat(bdi, BDI_DIRTIED)),
 108                   (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
 109                   (unsigned long) K(bdi->write_bandwidth),
 110                   nr_dirty,
 111                   nr_io,
 112                   nr_more_io,
 113                   !list_empty(&bdi->bdi_list), bdi->state);
 114#undef K
 115
 116        return 0;
 117}
 118
 119static int bdi_debug_stats_open(struct inode *inode, struct file *file)
 120{
 121        return single_open(file, bdi_debug_stats_show, inode->i_private);
 122}
 123
 124static const struct file_operations bdi_debug_stats_fops = {
 125        .open           = bdi_debug_stats_open,
 126        .read           = seq_read,
 127        .llseek         = seq_lseek,
 128        .release        = single_release,
 129};
 130
 131static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
 132{
 133        bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
 134        bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
 135                                               bdi, &bdi_debug_stats_fops);
 136}
 137
 138static void bdi_debug_unregister(struct backing_dev_info *bdi)
 139{
 140        debugfs_remove(bdi->debug_stats);
 141        debugfs_remove(bdi->debug_dir);
 142}
 143#else
 144static inline void bdi_debug_init(void)
 145{
 146}
 147static inline void bdi_debug_register(struct backing_dev_info *bdi,
 148                                      const char *name)
 149{
 150}
 151static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
 152{
 153}
 154#endif
 155
 156static ssize_t read_ahead_kb_store(struct device *dev,
 157                                  struct device_attribute *attr,
 158                                  const char *buf, size_t count)
 159{
 160        struct backing_dev_info *bdi = dev_get_drvdata(dev);
 161        unsigned long read_ahead_kb;
 162        ssize_t ret;
 163
 164        ret = kstrtoul(buf, 10, &read_ahead_kb);
 165        if (ret < 0)
 166                return ret;
 167
 168        bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
 169
 170        return count;
 171}
 172
 173#define K(pages) ((pages) << (PAGE_SHIFT - 10))
 174
 175#define BDI_SHOW(name, expr)                                            \
 176static ssize_t name##_show(struct device *dev,                          \
 177                           struct device_attribute *attr, char *page)   \
 178{                                                                       \
 179        struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
 180                                                                        \
 181        return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
 182}
 183
 184BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
 185
 186static ssize_t min_ratio_store(struct device *dev,
 187                struct device_attribute *attr, const char *buf, size_t count)
 188{
 189        struct backing_dev_info *bdi = dev_get_drvdata(dev);
 190        unsigned int ratio;
 191        ssize_t ret;
 192
 193        ret = kstrtouint(buf, 10, &ratio);
 194        if (ret < 0)
 195                return ret;
 196
 197        ret = bdi_set_min_ratio(bdi, ratio);
 198        if (!ret)
 199                ret = count;
 200
 201        return ret;
 202}
 203BDI_SHOW(min_ratio, bdi->min_ratio)
 204
 205static ssize_t max_ratio_store(struct device *dev,
 206                struct device_attribute *attr, const char *buf, size_t count)
 207{
 208        struct backing_dev_info *bdi = dev_get_drvdata(dev);
 209        unsigned int ratio;
 210        ssize_t ret;
 211
 212        ret = kstrtouint(buf, 10, &ratio);
 213        if (ret < 0)
 214                return ret;
 215
 216        ret = bdi_set_max_ratio(bdi, ratio);
 217        if (!ret)
 218                ret = count;
 219
 220        return ret;
 221}
 222BDI_SHOW(max_ratio, bdi->max_ratio)
 223
 224static ssize_t stable_pages_required_show(struct device *dev,
 225                                          struct device_attribute *attr,
 226                                          char *page)
 227{
 228        struct backing_dev_info *bdi = dev_get_drvdata(dev);
 229
 230        return snprintf(page, PAGE_SIZE-1, "%d\n",
 231                        bdi_cap_stable_pages_required(bdi) ? 1 : 0);
 232}
 233
 234#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
 235
 236static struct device_attribute bdi_dev_attrs[] = {
 237        __ATTR_RW(read_ahead_kb),
 238        __ATTR_RW(min_ratio),
 239        __ATTR_RW(max_ratio),
 240        __ATTR_RO(stable_pages_required),
 241        __ATTR_NULL,
 242};
 243
 244static __init int bdi_class_init(void)
 245{
 246        bdi_class = class_create(THIS_MODULE, "bdi");
 247        if (IS_ERR(bdi_class))
 248                return PTR_ERR(bdi_class);
 249
 250        bdi_class->dev_attrs = bdi_dev_attrs;
 251        bdi_debug_init();
 252        return 0;
 253}
 254postcore_initcall(bdi_class_init);
 255
 256static int __init default_bdi_init(void)
 257{
 258        int err;
 259
 260        err = bdi_init(&default_backing_dev_info);
 261        if (!err)
 262                bdi_register(&default_backing_dev_info, NULL, "default");
 263        err = bdi_init(&noop_backing_dev_info);
 264
 265        return err;
 266}
 267subsys_initcall(default_bdi_init);
 268
 269int bdi_has_dirty_io(struct backing_dev_info *bdi)
 270{
 271        return wb_has_dirty_io(&bdi->wb);
 272}
 273
 274static void wakeup_timer_fn(unsigned long data)
 275{
 276        struct backing_dev_info *bdi = (struct backing_dev_info *)data;
 277
 278        spin_lock_bh(&bdi->wb_lock);
 279        if (bdi->wb.task) {
 280                trace_writeback_wake_thread(bdi);
 281                wake_up_process(bdi->wb.task);
 282        } else if (bdi->dev) {
 283                /*
 284                 * When bdi tasks are inactive for long time, they are killed.
 285                 * In this case we have to wake-up the forker thread which
 286                 * should create and run the bdi thread.
 287                 */
 288                trace_writeback_wake_forker_thread(bdi);
 289                wake_up_process(default_backing_dev_info.wb.task);
 290        }
 291        spin_unlock_bh(&bdi->wb_lock);
 292}
 293
 294/*
 295 * This function is used when the first inode for this bdi is marked dirty. It
 296 * wakes-up the corresponding bdi thread which should then take care of the
 297 * periodic background write-out of dirty inodes. Since the write-out would
 298 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
 299 * set up a timer which wakes the bdi thread up later.
 300 *
 301 * Note, we wouldn't bother setting up the timer, but this function is on the
 302 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
 303 * by delaying the wake-up.
 304 */
 305void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
 306{
 307        unsigned long timeout;
 308
 309        timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
 310        mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout);
 311}
 312
 313/*
 314 * Calculate the longest interval (jiffies) bdi threads are allowed to be
 315 * inactive.
 316 */
 317static unsigned long bdi_longest_inactive(void)
 318{
 319        unsigned long interval;
 320
 321        interval = msecs_to_jiffies(dirty_writeback_interval * 10);
 322        return max(5UL * 60 * HZ, interval);
 323}
 324
 325/*
 326 * Clear pending bit and wakeup anybody waiting for flusher thread creation or
 327 * shutdown
 328 */
 329static void bdi_clear_pending(struct backing_dev_info *bdi)
 330{
 331        clear_bit(BDI_pending, &bdi->state);
 332        smp_mb__after_clear_bit();
 333        wake_up_bit(&bdi->state, BDI_pending);
 334}
 335
 336static int bdi_forker_thread(void *ptr)
 337{
 338        struct bdi_writeback *me = ptr;
 339
 340        current->flags |= PF_SWAPWRITE;
 341        set_freezable();
 342
 343        /*
 344         * Our parent may run at a different priority, just set us to normal
 345         */
 346        set_user_nice(current, 0);
 347
 348        for (;;) {
 349                struct task_struct *task = NULL;
 350                struct backing_dev_info *bdi;
 351                enum {
 352                        NO_ACTION,   /* Nothing to do */
 353                        FORK_THREAD, /* Fork bdi thread */
 354                        KILL_THREAD, /* Kill inactive bdi thread */
 355                } action = NO_ACTION;
 356
 357                /*
 358                 * Temporary measure, we want to make sure we don't see
 359                 * dirty data on the default backing_dev_info
 360                 */
 361                if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
 362                        del_timer(&me->wakeup_timer);
 363                        wb_do_writeback(me, 0);
 364                }
 365
 366                spin_lock_bh(&bdi_lock);
 367                /*
 368                 * In the following loop we are going to check whether we have
 369                 * some work to do without any synchronization with tasks
 370                 * waking us up to do work for them. Set the task state here
 371                 * so that we don't miss wakeups after verifying conditions.
 372                 */
 373                set_current_state(TASK_INTERRUPTIBLE);
 374
 375                list_for_each_entry(bdi, &bdi_list, bdi_list) {
 376                        bool have_dirty_io;
 377
 378                        if (!bdi_cap_writeback_dirty(bdi) ||
 379                             bdi_cap_flush_forker(bdi))
 380                                continue;
 381
 382                        WARN(!test_bit(BDI_registered, &bdi->state),
 383                             "bdi %p/%s is not registered!\n", bdi, bdi->name);
 384
 385                        have_dirty_io = !list_empty(&bdi->work_list) ||
 386                                        wb_has_dirty_io(&bdi->wb);
 387
 388                        /*
 389                         * If the bdi has work to do, but the thread does not
 390                         * exist - create it.
 391                         */
 392                        if (!bdi->wb.task && have_dirty_io) {
 393                                /*
 394                                 * Set the pending bit - if someone will try to
 395                                 * unregister this bdi - it'll wait on this bit.
 396                                 */
 397                                set_bit(BDI_pending, &bdi->state);
 398                                action = FORK_THREAD;
 399                                break;
 400                        }
 401
 402                        spin_lock(&bdi->wb_lock);
 403
 404                        /*
 405                         * If there is no work to do and the bdi thread was
 406                         * inactive long enough - kill it. The wb_lock is taken
 407                         * to make sure no-one adds more work to this bdi and
 408                         * wakes the bdi thread up.
 409                         */
 410                        if (bdi->wb.task && !have_dirty_io &&
 411                            time_after(jiffies, bdi->wb.last_active +
 412                                                bdi_longest_inactive())) {
 413                                task = bdi->wb.task;
 414                                bdi->wb.task = NULL;
 415                                spin_unlock(&bdi->wb_lock);
 416                                set_bit(BDI_pending, &bdi->state);
 417                                action = KILL_THREAD;
 418                                break;
 419                        }
 420                        spin_unlock(&bdi->wb_lock);
 421                }
 422                spin_unlock_bh(&bdi_lock);
 423
 424                /* Keep working if default bdi still has things to do */
 425                if (!list_empty(&me->bdi->work_list))
 426                        __set_current_state(TASK_RUNNING);
 427
 428                switch (action) {
 429                case FORK_THREAD:
 430                        __set_current_state(TASK_RUNNING);
 431                        task = kthread_create(bdi_writeback_thread, &bdi->wb,
 432                                              "flush-%s", dev_name(bdi->dev));
 433                        if (IS_ERR(task)) {
 434                                /*
 435                                 * If thread creation fails, force writeout of
 436                                 * the bdi from the thread. Hopefully 1024 is
 437                                 * large enough for efficient IO.
 438                                 */
 439                                writeback_inodes_wb(&bdi->wb, 1024,
 440                                                    WB_REASON_FORKER_THREAD);
 441                        } else {
 442                                /*
 443                                 * The spinlock makes sure we do not lose
 444                                 * wake-ups when racing with 'bdi_queue_work()'.
 445                                 * And as soon as the bdi thread is visible, we
 446                                 * can start it.
 447                                 */
 448                                spin_lock_bh(&bdi->wb_lock);
 449                                bdi->wb.task = task;
 450                                spin_unlock_bh(&bdi->wb_lock);
 451                                wake_up_process(task);
 452                        }
 453                        bdi_clear_pending(bdi);
 454                        break;
 455
 456                case KILL_THREAD:
 457                        __set_current_state(TASK_RUNNING);
 458                        kthread_stop(task);
 459                        bdi_clear_pending(bdi);
 460                        break;
 461
 462                case NO_ACTION:
 463                        if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
 464                                /*
 465                                 * There are no dirty data. The only thing we
 466                                 * should now care about is checking for
 467                                 * inactive bdi threads and killing them. Thus,
 468                                 * let's sleep for longer time, save energy and
 469                                 * be friendly for battery-driven devices.
 470                                 */
 471                                schedule_timeout(bdi_longest_inactive());
 472                        else
 473                                schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
 474                        try_to_freeze();
 475                        break;
 476                }
 477        }
 478
 479        return 0;
 480}
 481
 482/*
 483 * Remove bdi from bdi_list, and ensure that it is no longer visible
 484 */
 485static void bdi_remove_from_list(struct backing_dev_info *bdi)
 486{
 487        spin_lock_bh(&bdi_lock);
 488        list_del_rcu(&bdi->bdi_list);
 489        spin_unlock_bh(&bdi_lock);
 490
 491        synchronize_rcu_expedited();
 492}
 493
 494int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 495                const char *fmt, ...)
 496{
 497        va_list args;
 498        struct device *dev;
 499
 500        if (bdi->dev)   /* The driver needs to use separate queues per device */
 501                return 0;
 502
 503        va_start(args, fmt);
 504        dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
 505        va_end(args);
 506        if (IS_ERR(dev))
 507                return PTR_ERR(dev);
 508
 509        bdi->dev = dev;
 510
 511        /*
 512         * Just start the forker thread for our default backing_dev_info,
 513         * and add other bdi's to the list. They will get a thread created
 514         * on-demand when they need it.
 515         */
 516        if (bdi_cap_flush_forker(bdi)) {
 517                struct bdi_writeback *wb = &bdi->wb;
 518
 519                wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
 520                                                dev_name(dev));
 521                if (IS_ERR(wb->task))
 522                        return PTR_ERR(wb->task);
 523        }
 524
 525        bdi_debug_register(bdi, dev_name(dev));
 526        set_bit(BDI_registered, &bdi->state);
 527
 528        spin_lock_bh(&bdi_lock);
 529        list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
 530        spin_unlock_bh(&bdi_lock);
 531
 532        trace_writeback_bdi_register(bdi);
 533        return 0;
 534}
 535EXPORT_SYMBOL(bdi_register);
 536
 537int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
 538{
 539        return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
 540}
 541EXPORT_SYMBOL(bdi_register_dev);
 542
 543/*
 544 * Remove bdi from the global list and shutdown any threads we have running
 545 */
 546static void bdi_wb_shutdown(struct backing_dev_info *bdi)
 547{
 548        struct task_struct *task;
 549
 550        if (!bdi_cap_writeback_dirty(bdi))
 551                return;
 552
 553        /*
 554         * Make sure nobody finds us on the bdi_list anymore
 555         */
 556        bdi_remove_from_list(bdi);
 557
 558        /*
 559         * If setup is pending, wait for that to complete first
 560         */
 561        wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
 562                        TASK_UNINTERRUPTIBLE);
 563
 564        /*
 565         * Finally, kill the kernel thread. We don't need to be RCU
 566         * safe anymore, since the bdi is gone from visibility.
 567         */
 568        spin_lock_bh(&bdi->wb_lock);
 569        task = bdi->wb.task;
 570        bdi->wb.task = NULL;
 571        spin_unlock_bh(&bdi->wb_lock);
 572
 573        if (task)
 574                kthread_stop(task);
 575}
 576
 577/*
 578 * This bdi is going away now, make sure that no super_blocks point to it
 579 */
 580static void bdi_prune_sb(struct backing_dev_info *bdi)
 581{
 582        struct super_block *sb;
 583
 584        spin_lock(&sb_lock);
 585        list_for_each_entry(sb, &super_blocks, s_list) {
 586                if (sb->s_bdi == bdi)
 587                        sb->s_bdi = &default_backing_dev_info;
 588        }
 589        spin_unlock(&sb_lock);
 590}
 591
 592void bdi_unregister(struct backing_dev_info *bdi)
 593{
 594        struct device *dev = bdi->dev;
 595
 596        if (dev) {
 597                bdi_set_min_ratio(bdi, 0);
 598                trace_writeback_bdi_unregister(bdi);
 599                bdi_prune_sb(bdi);
 600                del_timer_sync(&bdi->wb.wakeup_timer);
 601
 602                if (!bdi_cap_flush_forker(bdi))
 603                        bdi_wb_shutdown(bdi);
 604                bdi_debug_unregister(bdi);
 605
 606                spin_lock_bh(&bdi->wb_lock);
 607                bdi->dev = NULL;
 608                spin_unlock_bh(&bdi->wb_lock);
 609
 610                device_unregister(dev);
 611        }
 612}
 613EXPORT_SYMBOL(bdi_unregister);
 614
 615static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
 616{
 617        memset(wb, 0, sizeof(*wb));
 618
 619        wb->bdi = bdi;
 620        wb->last_old_flush = jiffies;
 621        INIT_LIST_HEAD(&wb->b_dirty);
 622        INIT_LIST_HEAD(&wb->b_io);
 623        INIT_LIST_HEAD(&wb->b_more_io);
 624        spin_lock_init(&wb->list_lock);
 625        setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
 626}
 627
 628/*
 629 * Initial write bandwidth: 100 MB/s
 630 */
 631#define INIT_BW         (100 << (20 - PAGE_SHIFT))
 632
 633int bdi_init(struct backing_dev_info *bdi)
 634{
 635        int i, err;
 636
 637        bdi->dev = NULL;
 638
 639        bdi->min_ratio = 0;
 640        bdi->max_ratio = 100;
 641        bdi->max_prop_frac = FPROP_FRAC_BASE;
 642        spin_lock_init(&bdi->wb_lock);
 643        INIT_LIST_HEAD(&bdi->bdi_list);
 644        INIT_LIST_HEAD(&bdi->work_list);
 645
 646        bdi_wb_init(&bdi->wb, bdi);
 647
 648        for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
 649                err = percpu_counter_init(&bdi->bdi_stat[i], 0);
 650                if (err)
 651                        goto err;
 652        }
 653
 654        bdi->dirty_exceeded = 0;
 655
 656        bdi->bw_time_stamp = jiffies;
 657        bdi->written_stamp = 0;
 658
 659        bdi->balanced_dirty_ratelimit = INIT_BW;
 660        bdi->dirty_ratelimit = INIT_BW;
 661        bdi->write_bandwidth = INIT_BW;
 662        bdi->avg_write_bandwidth = INIT_BW;
 663
 664        err = fprop_local_init_percpu(&bdi->completions);
 665
 666        if (err) {
 667err:
 668                while (i--)
 669                        percpu_counter_destroy(&bdi->bdi_stat[i]);
 670        }
 671
 672        return err;
 673}
 674EXPORT_SYMBOL(bdi_init);
 675
 676void bdi_destroy(struct backing_dev_info *bdi)
 677{
 678        int i;
 679
 680        /*
 681         * Splice our entries to the default_backing_dev_info, if this
 682         * bdi disappears
 683         */
 684        if (bdi_has_dirty_io(bdi)) {
 685                struct bdi_writeback *dst = &default_backing_dev_info.wb;
 686
 687                bdi_lock_two(&bdi->wb, dst);
 688                list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
 689                list_splice(&bdi->wb.b_io, &dst->b_io);
 690                list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
 691                spin_unlock(&bdi->wb.list_lock);
 692                spin_unlock(&dst->list_lock);
 693        }
 694
 695        bdi_unregister(bdi);
 696
 697        /*
 698         * If bdi_unregister() had already been called earlier, the
 699         * wakeup_timer could still be armed because bdi_prune_sb()
 700         * can race with the bdi_wakeup_thread_delayed() calls from
 701         * __mark_inode_dirty().
 702         */
 703        del_timer_sync(&bdi->wb.wakeup_timer);
 704
 705        for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
 706                percpu_counter_destroy(&bdi->bdi_stat[i]);
 707
 708        fprop_local_destroy_percpu(&bdi->completions);
 709}
 710EXPORT_SYMBOL(bdi_destroy);
 711
 712/*
 713 * For use from filesystems to quickly init and register a bdi associated
 714 * with dirty writeback
 715 */
 716int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
 717                           unsigned int cap)
 718{
 719        char tmp[32];
 720        int err;
 721
 722        bdi->name = name;
 723        bdi->capabilities = cap;
 724        err = bdi_init(bdi);
 725        if (err)
 726                return err;
 727
 728        sprintf(tmp, "%.28s%s", name, "-%d");
 729        err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
 730        if (err) {
 731                bdi_destroy(bdi);
 732                return err;
 733        }
 734
 735        return 0;
 736}
 737EXPORT_SYMBOL(bdi_setup_and_register);
 738
 739static wait_queue_head_t congestion_wqh[2] = {
 740                __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
 741                __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
 742        };
 743static atomic_t nr_bdi_congested[2];
 744
 745void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
 746{
 747        enum bdi_state bit;
 748        wait_queue_head_t *wqh = &congestion_wqh[sync];
 749
 750        bit = sync ? BDI_sync_congested : BDI_async_congested;
 751        if (test_and_clear_bit(bit, &bdi->state))
 752                atomic_dec(&nr_bdi_congested[sync]);
 753        smp_mb__after_clear_bit();
 754        if (waitqueue_active(wqh))
 755                wake_up(wqh);
 756}
 757EXPORT_SYMBOL(clear_bdi_congested);
 758
 759void set_bdi_congested(struct backing_dev_info *bdi, int sync)
 760{
 761        enum bdi_state bit;
 762
 763        bit = sync ? BDI_sync_congested : BDI_async_congested;
 764        if (!test_and_set_bit(bit, &bdi->state))
 765                atomic_inc(&nr_bdi_congested[sync]);
 766}
 767EXPORT_SYMBOL(set_bdi_congested);
 768
 769/**
 770 * congestion_wait - wait for a backing_dev to become uncongested
 771 * @sync: SYNC or ASYNC IO
 772 * @timeout: timeout in jiffies
 773 *
 774 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
 775 * write congestion.  If no backing_devs are congested then just wait for the
 776 * next write to be completed.
 777 */
 778long congestion_wait(int sync, long timeout)
 779{
 780        long ret;
 781        unsigned long start = jiffies;
 782        DEFINE_WAIT(wait);
 783        wait_queue_head_t *wqh = &congestion_wqh[sync];
 784
 785        prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
 786        ret = io_schedule_timeout(timeout);
 787        finish_wait(wqh, &wait);
 788
 789        trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
 790                                        jiffies_to_usecs(jiffies - start));
 791
 792        return ret;
 793}
 794EXPORT_SYMBOL(congestion_wait);
 795
 796/**
 797 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
 798 * @zone: A zone to check if it is heavily congested
 799 * @sync: SYNC or ASYNC IO
 800 * @timeout: timeout in jiffies
 801 *
 802 * In the event of a congested backing_dev (any backing_dev) and the given
 803 * @zone has experienced recent congestion, this waits for up to @timeout
 804 * jiffies for either a BDI to exit congestion of the given @sync queue
 805 * or a write to complete.
 806 *
 807 * In the absence of zone congestion, cond_resched() is called to yield
 808 * the processor if necessary but otherwise does not sleep.
 809 *
 810 * The return value is 0 if the sleep is for the full timeout. Otherwise,
 811 * it is the number of jiffies that were still remaining when the function
 812 * returned. return_value == timeout implies the function did not sleep.
 813 */
 814long wait_iff_congested(struct zone *zone, int sync, long timeout)
 815{
 816        long ret;
 817        unsigned long start = jiffies;
 818        DEFINE_WAIT(wait);
 819        wait_queue_head_t *wqh = &congestion_wqh[sync];
 820
 821        /*
 822         * If there is no congestion, or heavy congestion is not being
 823         * encountered in the current zone, yield if necessary instead
 824         * of sleeping on the congestion queue
 825         */
 826        if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
 827                        !zone_is_reclaim_congested(zone)) {
 828                cond_resched();
 829
 830                /* In case we scheduled, work out time remaining */
 831                ret = timeout - (jiffies - start);
 832                if (ret < 0)
 833                        ret = 0;
 834
 835                goto out;
 836        }
 837
 838        /* Sleep until uncongested or a write happens */
 839        prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
 840        ret = io_schedule_timeout(timeout);
 841        finish_wait(wqh, &wait);
 842
 843out:
 844        trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
 845                                        jiffies_to_usecs(jiffies - start));
 846
 847        return ret;
 848}
 849EXPORT_SYMBOL(wait_iff_congested);
 850
 851int pdflush_proc_obsolete(struct ctl_table *table, int write,
 852                        void __user *buffer, size_t *lenp, loff_t *ppos)
 853{
 854        char kbuf[] = "0\n";
 855
 856        if (*ppos) {
 857                *lenp = 0;
 858                return 0;
 859        }
 860
 861        if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
 862                return -EFAULT;
 863        printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
 864                        table->procname);
 865
 866        *lenp = 2;
 867        *ppos += *lenp;
 868        return 2;
 869}
 870
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