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 static void bdi_add_default_flusher_thread(struct backing_dev_info *bdi);
  54
  55 #ifdef CONFIG_DEBUG_FS
  56 #include <linux/debugfs.h>
  57 #include <linux/seq_file.h>
  58
  59 static struct dentry *bdi_debug_root;
  60
  61 static void bdi_debug_init(void)
  62 {
  63         bdi_debug_root = debugfs_create_dir("bdi", NULL);
  64 }
  65
  66 static int bdi_debug_stats_show(struct seq_file *m, void *v)
  67 {
  68         struct backing_dev_info *bdi = m->private;
  69         struct bdi_writeback *wb = &bdi->wb;
  70         unsigned long background_thresh;
  71         unsigned long dirty_thresh;
  72         unsigned long bdi_thresh;
  73         unsigned long nr_dirty, nr_io, nr_more_io, nr_wb;
  74         struct inode *inode;
  75
  76         nr_wb = nr_dirty = nr_io = nr_more_io = 0;
  77         spin_lock(&inode_lock);
  78         list_for_each_entry(inode, &wb->b_dirty, i_list)
  79                 nr_dirty++;
  80         list_for_each_entry(inode, &wb->b_io, i_list)
  81                 nr_io++;
  82         list_for_each_entry(inode, &wb->b_more_io, i_list)
  83                 nr_more_io++;
  84         spin_unlock(&inode_lock);
  85
  86         get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi);
  87
  88 #define K(x) ((x) << (PAGE_SHIFT - 10))
  89         seq_printf(m,
  90                    "BdiWriteback:     %8lu kB\n"
  91                    "BdiReclaimable:   %8lu kB\n"
  92                    "BdiDirtyThresh:   %8lu kB\n"
  93                    "DirtyThresh:      %8lu kB\n"
  94                    "BackgroundThresh: %8lu kB\n"
  95                    "b_dirty:          %8lu\n"
  96                    "b_io:             %8lu\n"
  97                    "b_more_io:        %8lu\n"
  98                    "bdi_list:         %8u\n"
  99                    "state:            %8lx\n",
 100                    (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
 101                    (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
 102                    K(bdi_thresh), K(dirty_thresh),
 103                    K(background_thresh), nr_dirty, nr_io, nr_more_io,
 104                    !list_empty(&bdi->bdi_list), bdi->state);
 105 #undef K
 106
 107         return 0;
 108 }
 109
 110 static int bdi_debug_stats_open(struct inode *inode, struct file *file)
 111 {
 112         return single_open(file, bdi_debug_stats_show, inode->i_private);
 113 }
 114
 115 static const struct file_operations bdi_debug_stats_fops = {
 116         .open           = bdi_debug_stats_open,
 117         .read           = seq_read,
 118         .llseek         = seq_lseek,
 119         .release        = single_release,
 120 };
 121
 122 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
 123 {
 124         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
 125         bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
 126                                                bdi, &bdi_debug_stats_fops);
 127 }
 128
 129 static void bdi_debug_unregister(struct backing_dev_info *bdi)
 130 {
 131         debugfs_remove(bdi->debug_stats);
 132         debugfs_remove(bdi->debug_dir);
 133 }
 134 #else
 135 static inline void bdi_debug_init(void)
 136 {
 137 }
 138 static inline void bdi_debug_register(struct backing_dev_info *bdi,
 139                                       const char *name)
 140 {
 141 }
 142 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
 143 {
 144 }
 145 #endif
 146
 147 static ssize_t read_ahead_kb_store(struct device *dev,
 148                                   struct device_attribute *attr,
 149                                   const char *buf, size_t count)
 150 {
 151         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 152         char *end;
 153         unsigned long read_ahead_kb;
 154         ssize_t ret = -EINVAL;
 155
 156         read_ahead_kb = simple_strtoul(buf, &end, 10);
 157         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
 158                 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
 159                 ret = count;
 160         }
 161         return ret;
 162 }
 163
 164 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
 165
 166 #define BDI_SHOW(name, expr)                                            \
 167 static ssize_t name##_show(struct device *dev,                          \
 168                            struct device_attribute *attr, char *page)   \
 169 {                                                                       \
 170         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
 171                                                                         \
 172         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
 173 }
 174
 175 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
 176
 177 static ssize_t min_ratio_store(struct device *dev,
 178                 struct device_attribute *attr, const char *buf, size_t count)
 179 {
 180         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 181         char *end;
 182         unsigned int ratio;
 183         ssize_t ret = -EINVAL;
 184
 185         ratio = simple_strtoul(buf, &end, 10);
 186         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
 187                 ret = bdi_set_min_ratio(bdi, ratio);
 188                 if (!ret)
 189                         ret = count;
 190         }
 191         return ret;
 192 }
 193 BDI_SHOW(min_ratio, bdi->min_ratio)
 194
 195 static ssize_t max_ratio_store(struct device *dev,
 196                 struct device_attribute *attr, const char *buf, size_t count)
 197 {
 198         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 199         char *end;
 200         unsigned int ratio;
 201         ssize_t ret = -EINVAL;
 202
 203         ratio = simple_strtoul(buf, &end, 10);
 204         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
 205                 ret = bdi_set_max_ratio(bdi, ratio);
 206                 if (!ret)
 207                         ret = count;
 208         }
 209         return ret;
 210 }
 211 BDI_SHOW(max_ratio, bdi->max_ratio)
 212
 213 #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
 214
 215 static struct device_attribute bdi_dev_attrs[] = {
 216         __ATTR_RW(read_ahead_kb),
 217         __ATTR_RW(min_ratio),
 218         __ATTR_RW(max_ratio),
 219         __ATTR_NULL,
 220 };
 221
 222 static __init int bdi_class_init(void)
 223 {
 224         bdi_class = class_create(THIS_MODULE, "bdi");
 225         if (IS_ERR(bdi_class))
 226                 return PTR_ERR(bdi_class);
 227
 228         bdi_class->dev_attrs = bdi_dev_attrs;
 229         bdi_debug_init();
 230         return 0;
 231 }
 232 postcore_initcall(bdi_class_init);
 233
 234 static int __init default_bdi_init(void)
 235 {
 236         int err;
 237
 238         sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
 239         BUG_ON(IS_ERR(sync_supers_tsk));
 240
 241         init_timer(&sync_supers_timer);
 242         setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
 243         bdi_arm_supers_timer();
 244
 245         err = bdi_init(&default_backing_dev_info);
 246         if (!err)
 247                 bdi_register(&default_backing_dev_info, NULL, "default");
 248
 249         return err;
 250 }
 251 subsys_initcall(default_bdi_init);
 252
 253 static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
 254 {
 255         memset(wb, 0, sizeof(*wb));
 256
 257         wb->bdi = bdi;
 258         wb->last_old_flush = jiffies;
 259         INIT_LIST_HEAD(&wb->b_dirty);
 260         INIT_LIST_HEAD(&wb->b_io);
 261         INIT_LIST_HEAD(&wb->b_more_io);
 262 }
 263
 264 int bdi_has_dirty_io(struct backing_dev_info *bdi)
 265 {
 266         return wb_has_dirty_io(&bdi->wb);
 267 }
 268
 269 static void bdi_flush_io(struct backing_dev_info *bdi)
 270 {
 271         struct writeback_control wbc = {
 272                 .sync_mode              = WB_SYNC_NONE,
 273                 .older_than_this        = NULL,
 274                 .range_cyclic           = 1,
 275                 .nr_to_write            = 1024,
 276         };
 277
 278         writeback_inodes_wb(&bdi->wb, &wbc);
 279 }
 280
 281 /*
 282  * kupdated() used to do this. We cannot do it from the bdi_forker_thread()
 283  * or we risk deadlocking on ->s_umount. The longer term solution would be
 284  * to implement sync_supers_bdi() or similar and simply do it from the
 285  * bdi writeback thread individually.
 286  */
 287 static int bdi_sync_supers(void *unused)
 288 {
 289         set_user_nice(current, 0);
 290
 291         while (!kthread_should_stop()) {
 292                 set_current_state(TASK_INTERRUPTIBLE);
 293                 schedule();
 294
 295                 /*
 296                  * Do this periodically, like kupdated() did before.
 297                  */
 298                 sync_supers();
 299         }
 300
 301         return 0;
 302 }
 303
 304 void bdi_arm_supers_timer(void)
 305 {
 306         unsigned long next;
 307
 308         if (!dirty_writeback_interval)
 309                 return;
 310
 311         next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
 312         mod_timer(&sync_supers_timer, round_jiffies_up(next));
 313 }
 314
 315 static void sync_supers_timer_fn(unsigned long unused)
 316 {
 317         wake_up_process(sync_supers_tsk);
 318         bdi_arm_supers_timer();
 319 }
 320
 321 static int bdi_forker_thread(void *ptr)
 322 {
 323         struct bdi_writeback *me = ptr;
 324
 325         current->flags |= PF_FLUSHER | PF_SWAPWRITE;
 326         set_freezable();
 327
 328         /*
 329          * Our parent may run at a different priority, just set us to normal
 330          */
 331         set_user_nice(current, 0);
 332
 333         for (;;) {
 334                 struct task_struct *task;
 335                 struct backing_dev_info *bdi, *tmp;
 336
 337                 /*
 338                  * Temporary measure, we want to make sure we don't see
 339                  * dirty data on the default backing_dev_info
 340                  */
 341                 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list))
 342                         wb_do_writeback(me, 0);
 343
 344                 spin_lock_bh(&bdi_lock);
 345                 set_current_state(TASK_INTERRUPTIBLE);
 346
 347                 /*
 348                  * Check if any existing bdi's have dirty data without
 349                  * a thread registered. If so, set that up.
 350                  */
 351                 list_for_each_entry_safe(bdi, tmp, &bdi_list, bdi_list) {
 352                         if (bdi->wb.task)
 353                                 continue;
 354                         if (list_empty(&bdi->work_list) &&
 355                             !bdi_has_dirty_io(bdi))
 356                                 continue;
 357
 358                         bdi_add_default_flusher_thread(bdi);
 359                 }
 360
 361                 /* Keep working if default bdi still has things to do */
 362                 if (!list_empty(&me->bdi->work_list))
 363                         __set_current_state(TASK_RUNNING);
 364
 365                 if (list_empty(&bdi_pending_list)) {
 366                         unsigned long wait;
 367
 368                         spin_unlock_bh(&bdi_lock);
 369                         wait = msecs_to_jiffies(dirty_writeback_interval * 10);
 370                         if (wait)
 371                                 schedule_timeout(wait);
 372                         else
 373                                 schedule();
 374                         try_to_freeze();
 375                         continue;
 376                 }
 377
 378                 __set_current_state(TASK_RUNNING);
 379
 380                 /*
 381                  * This is our real job - check for pending entries in
 382                  * bdi_pending_list, and create the threads that got added
 383                  */
 384                 bdi = list_entry(bdi_pending_list.next, struct backing_dev_info,
 385                                  bdi_list);
 386                 list_del_init(&bdi->bdi_list);
 387                 spin_unlock_bh(&bdi_lock);
 388
 389                 task = kthread_run(bdi_writeback_thread, &bdi->wb, "flush-%s",
 390                                    dev_name(bdi->dev));
 391                 if (IS_ERR(task)) {
 392                         /*
 393                          * If thread creation fails, then readd the bdi back to
 394                          * the list and force writeout of the bdi from this
 395                          * forker thread. That will free some memory and we can
 396                          * try again. Add it to the tail so we get a chance to
 397                          * flush other bdi's to free memory.
 398                          */
 399                         spin_lock_bh(&bdi_lock);
 400                         list_add_tail(&bdi->bdi_list, &bdi_pending_list);
 401                         spin_unlock_bh(&bdi_lock);
 402
 403                         bdi_flush_io(bdi);
 404                 } else
 405                         bdi->wb.task = task;
 406         }
 407
 408         return 0;
 409 }
 410
 411 static void bdi_add_to_pending(struct rcu_head *head)
 412 {
 413         struct backing_dev_info *bdi;
 414
 415         bdi = container_of(head, struct backing_dev_info, rcu_head);
 416         INIT_LIST_HEAD(&bdi->bdi_list);
 417
 418         spin_lock(&bdi_lock);
 419         list_add_tail(&bdi->bdi_list, &bdi_pending_list);
 420         spin_unlock(&bdi_lock);
 421
 422         /*
 423          * We are now on the pending list, wake up bdi_forker_task()
 424          * to finish the job and add us back to the active bdi_list
 425          */
 426         wake_up_process(default_backing_dev_info.wb.task);
 427 }
 428
 429 /*
 430  * Add the default flusher thread that gets created for any bdi
 431  * that has dirty data pending writeout
 432  */
 433 static void bdi_add_default_flusher_thread(struct backing_dev_info *bdi)
 434 {
 435         if (!bdi_cap_writeback_dirty(bdi))
 436                 return;
 437
 438         if (WARN_ON(!test_bit(BDI_registered, &bdi->state))) {
 439                 printk(KERN_ERR "bdi %p/%s is not registered!\n",
 440                                                         bdi, bdi->name);
 441                 return;
 442         }
 443
 444         /*
 445          * Check with the helper whether to proceed adding a thread. Will only
 446          * abort if we two or more simultanous calls to
 447          * bdi_add_default_flusher_thread() occured, further additions will
 448          * block waiting for previous additions to finish.
 449          */
 450         if (!test_and_set_bit(BDI_pending, &bdi->state)) {
 451                 list_del_rcu(&bdi->bdi_list);
 452
 453                 /*
 454                  * We must wait for the current RCU period to end before
 455                  * moving to the pending list. So schedule that operation
 456                  * from an RCU callback.
 457                  */
 458                 call_rcu(&bdi->rcu_head, bdi_add_to_pending);
 459         }
 460 }
 461
 462 /*
 463  * Remove bdi from bdi_list, and ensure that it is no longer visible
 464  */
 465 static void bdi_remove_from_list(struct backing_dev_info *bdi)
 466 {
 467         spin_lock_bh(&bdi_lock);
 468         list_del_rcu(&bdi->bdi_list);
 469         spin_unlock_bh(&bdi_lock);
 470
 471         synchronize_rcu();
 472 }
 473
 474 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 475                 const char *fmt, ...)
 476 {
 477         va_list args;
 478         int ret = 0;
 479         struct device *dev;
 480
 481         if (bdi->dev)   /* The driver needs to use separate queues per device */
 482                 goto exit;
 483
 484         va_start(args, fmt);
 485         dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
 486         va_end(args);
 487         if (IS_ERR(dev)) {
 488                 ret = PTR_ERR(dev);
 489                 goto exit;
 490         }
 491
 492         spin_lock_bh(&bdi_lock);
 493         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
 494         spin_unlock_bh(&bdi_lock);
 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                         wb->task = NULL;
 510                         ret = -ENOMEM;
 511
 512                         bdi_remove_from_list(bdi);
 513                         goto exit;
 514                 }
 515         }
 516
 517         bdi_debug_register(bdi, dev_name(dev));
 518         set_bit(BDI_registered, &bdi->state);
 519         trace_writeback_bdi_register(bdi);
 520 exit:
 521         return ret;
 522 }
 523 EXPORT_SYMBOL(bdi_register);
 524
 525 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
 526 {
 527         return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
 528 }
 529 EXPORT_SYMBOL(bdi_register_dev);
 530
 531 /*
 532  * Remove bdi from the global list and shutdown any threads we have running
 533  */
 534 static void bdi_wb_shutdown(struct backing_dev_info *bdi)
 535 {
 536         if (!bdi_cap_writeback_dirty(bdi))
 537                 return;
 538
 539         /*
 540          * If setup is pending, wait for that to complete first
 541          */
 542         wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
 543                         TASK_UNINTERRUPTIBLE);
 544
 545         /*
 546          * Make sure nobody finds us on the bdi_list anymore
 547          */
 548         bdi_remove_from_list(bdi);
 549
 550         /*
 551          * Finally, kill the kernel thread. We don't need to be RCU
 552          * safe anymore, since the bdi is gone from visibility. Force
 553          * unfreeze of the thread before calling kthread_stop(), otherwise
 554          * it would never exet if it is currently stuck in the refrigerator.
 555          */
 556         if (bdi->wb.task) {
 557                 thaw_process(bdi->wb.task);
 558                 kthread_stop(bdi->wb.task);
 559         }
 560 }
 561
 562 /*
 563  * This bdi is going away now, make sure that no super_blocks point to it
 564  */
 565 static void bdi_prune_sb(struct backing_dev_info *bdi)
 566 {
 567         struct super_block *sb;
 568
 569         spin_lock(&sb_lock);
 570         list_for_each_entry(sb, &super_blocks, s_list) {
 571                 if (sb->s_bdi == bdi)
 572                         sb->s_bdi = NULL;
 573         }
 574         spin_unlock(&sb_lock);
 575 }
 576
 577 void bdi_unregister(struct backing_dev_info *bdi)
 578 {
 579         if (bdi->dev) {
 580                 trace_writeback_bdi_unregister(bdi);
 581                 bdi_prune_sb(bdi);
 582
 583                 if (!bdi_cap_flush_forker(bdi))
 584                         bdi_wb_shutdown(bdi);
 585                 bdi_debug_unregister(bdi);
 586                 device_unregister(bdi->dev);
 587                 bdi->dev = NULL;
 588         }
 589 }
 590 EXPORT_SYMBOL(bdi_unregister);
 591
 592 int bdi_init(struct backing_dev_info *bdi)
 593 {
 594         int i, err;
 595
 596         bdi->dev = NULL;
 597
 598         bdi->min_ratio = 0;
 599         bdi->max_ratio = 100;
 600         bdi->max_prop_frac = PROP_FRAC_BASE;
 601         spin_lock_init(&bdi->wb_lock);
 602         INIT_RCU_HEAD(&bdi->rcu_head);
 603         INIT_LIST_HEAD(&bdi->bdi_list);
 604         INIT_LIST_HEAD(&bdi->work_list);
 605
 606         bdi_wb_init(&bdi->wb, bdi);
 607
 608         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
 609                 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
 610                 if (err)
 611                         goto err;
 612         }
 613
 614         bdi->dirty_exceeded = 0;
 615         err = prop_local_init_percpu(&bdi->completions);
 616
 617         if (err) {
 618 err:
 619                 while (i--)
 620                         percpu_counter_destroy(&bdi->bdi_stat[i]);
 621         }
 622
 623         return err;
 624 }
 625 EXPORT_SYMBOL(bdi_init);
 626
 627 void bdi_destroy(struct backing_dev_info *bdi)
 628 {
 629         int i;
 630
 631         /*
 632          * Splice our entries to the default_backing_dev_info, if this
 633          * bdi disappears
 634          */
 635         if (bdi_has_dirty_io(bdi)) {
 636                 struct bdi_writeback *dst = &default_backing_dev_info.wb;
 637
 638                 spin_lock(&inode_lock);
 639                 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
 640                 list_splice(&bdi->wb.b_io, &dst->b_io);
 641                 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
 642                 spin_unlock(&inode_lock);
 643         }
 644
 645         bdi_unregister(bdi);
 646
 647         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
 648                 percpu_counter_destroy(&bdi->bdi_stat[i]);
 649
 650         prop_local_destroy_percpu(&bdi->completions);
 651 }
 652 EXPORT_SYMBOL(bdi_destroy);
 653
 654 /*
 655  * For use from filesystems to quickly init and register a bdi associated
 656  * with dirty writeback
 657  */
 658 int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
 659                            unsigned int cap)
 660 {
 661         char tmp[32];
 662         int err;
 663
 664         bdi->name = name;
 665         bdi->capabilities = cap;
 666         err = bdi_init(bdi);
 667         if (err)
 668                 return err;
 669
 670         sprintf(tmp, "%.28s%s", name, "-%d");
 671         err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
 672         if (err) {
 673                 bdi_destroy(bdi);
 674                 return err;
 675         }
 676
 677         return 0;
 678 }
 679 EXPORT_SYMBOL(bdi_setup_and_register);
 680
 681 static wait_queue_head_t congestion_wqh[2] = {
 682                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
 683                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
 684         };
 685
 686 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
 687 {
 688         enum bdi_state bit;
 689         wait_queue_head_t *wqh = &congestion_wqh[sync];
 690
 691         bit = sync ? BDI_sync_congested : BDI_async_congested;
 692         clear_bit(bit, &bdi->state);
 693         smp_mb__after_clear_bit();
 694         if (waitqueue_active(wqh))
 695                 wake_up(wqh);
 696 }
 697 EXPORT_SYMBOL(clear_bdi_congested);
 698
 699 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
 700 {
 701         enum bdi_state bit;
 702
 703         bit = sync ? BDI_sync_congested : BDI_async_congested;
 704         set_bit(bit, &bdi->state);
 705 }
 706 EXPORT_SYMBOL(set_bdi_congested);
 707
 708 /**
 709  * congestion_wait - wait for a backing_dev to become uncongested
 710  * @sync: SYNC or ASYNC IO
 711  * @timeout: timeout in jiffies
 712  *
 713  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
 714  * write congestion.  If no backing_devs are congested then just wait for the
 715  * next write to be completed.
 716  */
 717 long congestion_wait(int sync, long timeout)
 718 {
 719         long ret;
 720         DEFINE_WAIT(wait);
 721         wait_queue_head_t *wqh = &congestion_wqh[sync];
 722
 723         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
 724         ret = io_schedule_timeout(timeout);
 725         finish_wait(wqh, &wait);
 726         return ret;
 727 }
 728 EXPORT_SYMBOL(congestion_wait);
 729