mm/backing-dev.c

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