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