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
  14 static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
  15
  16 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
  17 {
  18 }
  19 EXPORT_SYMBOL(default_unplug_io_fn);
  20
  21 struct backing_dev_info default_backing_dev_info = {
  22         .name           = "default",
  23         .ra_pages       = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
  24         .state          = 0,
  25         .capabilities   = BDI_CAP_MAP_COPY,
  26         .unplug_io_fn   = default_unplug_io_fn,
  27 };
  28 EXPORT_SYMBOL_GPL(default_backing_dev_info);
  29
  30 struct backing_dev_info noop_backing_dev_info = {
  31         .name           = "noop",
  32         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
  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_task(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;
  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         /*
  77          * inode lock is enough here, the bdi->wb_list is protected by
  78          * RCU on the reader side
  79          */
  80         nr_wb = nr_dirty = nr_io = nr_more_io = 0;
  81         spin_lock(&inode_lock);
  82         list_for_each_entry(wb, &bdi->wb_list, list) {
  83                 nr_wb++;
  84                 list_for_each_entry(inode, &wb->b_dirty, i_list)
  85                         nr_dirty++;
  86                 list_for_each_entry(inode, &wb->b_io, i_list)
  87                         nr_io++;
  88                 list_for_each_entry(inode, &wb->b_more_io, i_list)
  89                         nr_more_io++;
  90         }
  91         spin_unlock(&inode_lock);
  92
  93         get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi);
  94
  95 #define K(x) ((x) << (PAGE_SHIFT - 10))
  96         seq_printf(m,
  97                    "BdiWriteback:     %8lu kB\n"
  98                    "BdiReclaimable:   %8lu kB\n"
  99                    "BdiDirtyThresh:   %8lu kB\n"
 100                    "DirtyThresh:      %8lu kB\n"
 101                    "BackgroundThresh: %8lu kB\n"
 102                    "WritebackThreads: %8lu\n"
 103                    "b_dirty:          %8lu\n"
 104                    "b_io:             %8lu\n"
 105                    "b_more_io:        %8lu\n"
 106                    "bdi_list:         %8u\n"
 107                    "state:            %8lx\n"
 108                    "wb_list:          %8u\n",
 109                    (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
 110                    (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
 111                    K(bdi_thresh), K(dirty_thresh),
 112                    K(background_thresh), nr_wb, nr_dirty, nr_io, nr_more_io,
 113                    !list_empty(&bdi->bdi_list), bdi->state,
 114                    !list_empty(&bdi->wb_list));
 115 #undef K
 116
 117         return 0;
 118 }
 119
 120 static int bdi_debug_stats_open(struct inode *inode, struct file *file)
 121 {
 122         return single_open(file, bdi_debug_stats_show, inode->i_private);
 123 }
 124
 125 static const struct file_operations bdi_debug_stats_fops = {
 126         .open           = bdi_debug_stats_open,
 127         .read           = seq_read,
 128         .llseek         = seq_lseek,
 129         .release        = single_release,
 130 };
 131
 132 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
 133 {
 134         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
 135         bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
 136                                                bdi, &bdi_debug_stats_fops);
 137 }
 138
 139 static void bdi_debug_unregister(struct backing_dev_info *bdi)
 140 {
 141         debugfs_remove(bdi->debug_stats);
 142         debugfs_remove(bdi->debug_dir);
 143 }
 144 #else
 145 static inline void bdi_debug_init(void)
 146 {
 147 }
 148 static inline void bdi_debug_register(struct backing_dev_info *bdi,
 149                                       const char *name)
 150 {
 151 }
 152 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
 153 {
 154 }
 155 #endif
 156
 157 static ssize_t read_ahead_kb_store(struct device *dev,
 158                                   struct device_attribute *attr,
 159                                   const char *buf, size_t count)
 160 {
 161         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 162         char *end;
 163         unsigned long read_ahead_kb;
 164         ssize_t ret = -EINVAL;
 165
 166         read_ahead_kb = simple_strtoul(buf, &end, 10);
 167         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
 168                 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
 169                 ret = count;
 170         }
 171         return ret;
 172 }
 173
 174 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
 175
 176 #define BDI_SHOW(name, expr)                                            \
 177 static ssize_t name##_show(struct device *dev,                          \
 178                            struct device_attribute *attr, char *page)   \
 179 {                                                                       \
 180         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
 181                                                                         \
 182         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
 183 }
 184
 185 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
 186
 187 static ssize_t min_ratio_store(struct device *dev,
 188                 struct device_attribute *attr, const char *buf, size_t count)
 189 {
 190         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 191         char *end;
 192         unsigned int ratio;
 193         ssize_t ret = -EINVAL;
 194
 195         ratio = simple_strtoul(buf, &end, 10);
 196         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
 197                 ret = bdi_set_min_ratio(bdi, ratio);
 198                 if (!ret)
 199                         ret = count;
 200         }
 201         return ret;
 202 }
 203 BDI_SHOW(min_ratio, bdi->min_ratio)
 204
 205 static 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         char *end;
 210         unsigned int ratio;
 211         ssize_t ret = -EINVAL;
 212
 213         ratio = simple_strtoul(buf, &end, 10);
 214         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
 215                 ret = bdi_set_max_ratio(bdi, ratio);
 216                 if (!ret)
 217                         ret = count;
 218         }
 219         return ret;
 220 }
 221 BDI_SHOW(max_ratio, bdi->max_ratio)
 222
 223 #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
 224
 225 static struct device_attribute bdi_dev_attrs[] = {
 226         __ATTR_RW(read_ahead_kb),
 227         __ATTR_RW(min_ratio),
 228         __ATTR_RW(max_ratio),
 229         __ATTR_NULL,
 230 };
 231
 232 static __init int bdi_class_init(void)
 233 {
 234         bdi_class = class_create(THIS_MODULE, "bdi");
 235         if (IS_ERR(bdi_class))
 236                 return PTR_ERR(bdi_class);
 237
 238         bdi_class->dev_attrs = bdi_dev_attrs;
 239         bdi_debug_init();
 240         return 0;
 241 }
 242 postcore_initcall(bdi_class_init);
 243
 244 static int __init default_bdi_init(void)
 245 {
 246         int err;
 247
 248         sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
 249         BUG_ON(IS_ERR(sync_supers_tsk));
 250
 251         init_timer(&sync_supers_timer);
 252         setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
 253         bdi_arm_supers_timer();
 254
 255         err = bdi_init(&default_backing_dev_info);
 256         if (!err)
 257                 bdi_register(&default_backing_dev_info, NULL, "default");
 258         err = bdi_init(&noop_backing_dev_info);
 259
 260         return err;
 261 }
 262 subsys_initcall(default_bdi_init);
 263
 264 static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
 265 {
 266         memset(wb, 0, sizeof(*wb));
 267
 268         wb->bdi = bdi;
 269         wb->last_old_flush = jiffies;
 270         INIT_LIST_HEAD(&wb->b_dirty);
 271         INIT_LIST_HEAD(&wb->b_io);
 272         INIT_LIST_HEAD(&wb->b_more_io);
 273 }
 274
 275 static void bdi_task_init(struct backing_dev_info *bdi,
 276                           struct bdi_writeback *wb)
 277 {
 278         struct task_struct *tsk = current;
 279
 280         spin_lock(&bdi->wb_lock);
 281         list_add_tail_rcu(&wb->list, &bdi->wb_list);
 282         spin_unlock(&bdi->wb_lock);
 283
 284         tsk->flags |= PF_FLUSHER | PF_SWAPWRITE;
 285         set_freezable();
 286
 287         /*
 288          * Our parent may run at a different priority, just set us to normal
 289          */
 290         set_user_nice(tsk, 0);
 291 }
 292
 293 static int bdi_start_fn(void *ptr)
 294 {
 295         struct bdi_writeback *wb = ptr;
 296         struct backing_dev_info *bdi = wb->bdi;
 297         int ret;
 298
 299         /*
 300          * Add us to the active bdi_list
 301          */
 302         spin_lock_bh(&bdi_lock);
 303         list_add_rcu(&bdi->bdi_list, &bdi_list);
 304         spin_unlock_bh(&bdi_lock);
 305
 306         bdi_task_init(bdi, wb);
 307
 308         /*
 309          * Clear pending bit and wakeup anybody waiting to tear us down
 310          */
 311         clear_bit(BDI_pending, &bdi->state);
 312         smp_mb__after_clear_bit();
 313         wake_up_bit(&bdi->state, BDI_pending);
 314
 315         ret = bdi_writeback_task(wb);
 316
 317         /*
 318          * Remove us from the list
 319          */
 320         spin_lock(&bdi->wb_lock);
 321         list_del_rcu(&wb->list);
 322         spin_unlock(&bdi->wb_lock);
 323
 324         /*
 325          * Flush any work that raced with us exiting. No new work
 326          * will be added, since this bdi isn't discoverable anymore.
 327          */
 328         if (!list_empty(&bdi->work_list))
 329                 wb_do_writeback(wb, 1);
 330
 331         wb->task = NULL;
 332         return ret;
 333 }
 334
 335 int bdi_has_dirty_io(struct backing_dev_info *bdi)
 336 {
 337         return wb_has_dirty_io(&bdi->wb);
 338 }
 339
 340 static void bdi_flush_io(struct backing_dev_info *bdi)
 341 {
 342         struct writeback_control wbc = {
 343                 .sync_mode              = WB_SYNC_NONE,
 344                 .older_than_this        = NULL,
 345                 .range_cyclic           = 1,
 346                 .nr_to_write            = 1024,
 347         };
 348
 349         writeback_inodes_wb(&bdi->wb, &wbc);
 350 }
 351
 352 /*
 353  * kupdated() used to do this. We cannot do it from the bdi_forker_task()
 354  * or we risk deadlocking on ->s_umount. The longer term solution would be
 355  * to implement sync_supers_bdi() or similar and simply do it from the
 356  * bdi writeback tasks individually.
 357  */
 358 static int bdi_sync_supers(void *unused)
 359 {
 360         set_user_nice(current, 0);
 361
 362         while (!kthread_should_stop()) {
 363                 set_current_state(TASK_INTERRUPTIBLE);
 364                 schedule();
 365
 366                 /*
 367                  * Do this periodically, like kupdated() did before.
 368                  */
 369                 sync_supers();
 370         }
 371
 372         return 0;
 373 }
 374
 375 void bdi_arm_supers_timer(void)
 376 {
 377         unsigned long next;
 378
 379         if (!dirty_writeback_interval)
 380                 return;
 381
 382         next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
 383         mod_timer(&sync_supers_timer, round_jiffies_up(next));
 384 }
 385
 386 static void sync_supers_timer_fn(unsigned long unused)
 387 {
 388         wake_up_process(sync_supers_tsk);
 389         bdi_arm_supers_timer();
 390 }
 391
 392 static int bdi_forker_task(void *ptr)
 393 {
 394         struct bdi_writeback *me = ptr;
 395
 396         bdi_task_init(me->bdi, me);
 397
 398         for (;;) {
 399                 struct backing_dev_info *bdi, *tmp;
 400                 struct bdi_writeback *wb;
 401
 402                 /*
 403                  * Temporary measure, we want to make sure we don't see
 404                  * dirty data on the default backing_dev_info
 405                  */
 406                 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list))
 407                         wb_do_writeback(me, 0);
 408
 409                 spin_lock_bh(&bdi_lock);
 410
 411                 /*
 412                  * Check if any existing bdi's have dirty data without
 413                  * a thread registered. If so, set that up.
 414                  */
 415                 list_for_each_entry_safe(bdi, tmp, &bdi_list, bdi_list) {
 416                         if (bdi->wb.task)
 417                                 continue;
 418                         if (list_empty(&bdi->work_list) &&
 419                             !bdi_has_dirty_io(bdi))
 420                                 continue;
 421
 422                         bdi_add_default_flusher_task(bdi);
 423                 }
 424
 425                 set_current_state(TASK_INTERRUPTIBLE);
 426
 427                 if (list_empty(&bdi_pending_list)) {
 428                         unsigned long wait;
 429
 430                         spin_unlock_bh(&bdi_lock);
 431                         wait = msecs_to_jiffies(dirty_writeback_interval * 10);
 432                         if (wait)
 433                                 schedule_timeout(wait);
 434                         else
 435                                 schedule();
 436                         try_to_freeze();
 437                         continue;
 438                 }
 439
 440                 __set_current_state(TASK_RUNNING);
 441
 442                 /*
 443                  * This is our real job - check for pending entries in
 444                  * bdi_pending_list, and create the tasks that got added
 445                  */
 446                 bdi = list_entry(bdi_pending_list.next, struct backing_dev_info,
 447                                  bdi_list);
 448                 list_del_init(&bdi->bdi_list);
 449                 spin_unlock_bh(&bdi_lock);
 450
 451                 wb = &bdi->wb;
 452                 wb->task = kthread_run(bdi_start_fn, wb, "flush-%s",
 453                                         dev_name(bdi->dev));
 454                 /*
 455                  * If task creation fails, then readd the bdi to
 456                  * the pending list and force writeout of the bdi
 457                  * from this forker thread. That will free some memory
 458                  * and we can try again.
 459                  */
 460                 if (IS_ERR(wb->task)) {
 461                         wb->task = NULL;
 462
 463                         /*
 464                          * Add this 'bdi' to the back, so we get
 465                          * a chance to flush other bdi's to free
 466                          * memory.
 467                          */
 468                         spin_lock_bh(&bdi_lock);
 469                         list_add_tail(&bdi->bdi_list, &bdi_pending_list);
 470                         spin_unlock_bh(&bdi_lock);
 471
 472                         bdi_flush_io(bdi);
 473                 }
 474         }
 475
 476         return 0;
 477 }
 478
 479 static void bdi_add_to_pending(struct rcu_head *head)
 480 {
 481         struct backing_dev_info *bdi;
 482
 483         bdi = container_of(head, struct backing_dev_info, rcu_head);
 484         INIT_LIST_HEAD(&bdi->bdi_list);
 485
 486         spin_lock(&bdi_lock);
 487         list_add_tail(&bdi->bdi_list, &bdi_pending_list);
 488         spin_unlock(&bdi_lock);
 489
 490         /*
 491          * We are now on the pending list, wake up bdi_forker_task()
 492          * to finish the job and add us back to the active bdi_list
 493          */
 494         wake_up_process(default_backing_dev_info.wb.task);
 495 }
 496
 497 /*
 498  * Add the default flusher task that gets created for any bdi
 499  * that has dirty data pending writeout
 500  */
 501 void static bdi_add_default_flusher_task(struct backing_dev_info *bdi)
 502 {
 503         if (!bdi_cap_writeback_dirty(bdi))
 504                 return;
 505
 506         if (WARN_ON(!test_bit(BDI_registered, &bdi->state))) {
 507                 printk(KERN_ERR "bdi %p/%s is not registered!\n",
 508                                                         bdi, bdi->name);
 509                 return;
 510         }
 511
 512         /*
 513          * Check with the helper whether to proceed adding a task. Will only
 514          * abort if we two or more simultanous calls to
 515          * bdi_add_default_flusher_task() occured, further additions will block
 516          * waiting for previous additions to finish.
 517          */
 518         if (!test_and_set_bit(BDI_pending, &bdi->state)) {
 519                 list_del_rcu(&bdi->bdi_list);
 520
 521                 /*
 522                  * We must wait for the current RCU period to end before
 523                  * moving to the pending list. So schedule that operation
 524                  * from an RCU callback.
 525                  */
 526                 call_rcu(&bdi->rcu_head, bdi_add_to_pending);
 527         }
 528 }
 529
 530 /*
 531  * Remove bdi from bdi_list, and ensure that it is no longer visible
 532  */
 533 static void bdi_remove_from_list(struct backing_dev_info *bdi)
 534 {
 535         spin_lock_bh(&bdi_lock);
 536         list_del_rcu(&bdi->bdi_list);
 537         spin_unlock_bh(&bdi_lock);
 538
 539         synchronize_rcu();
 540 }
 541
 542 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 543                 const char *fmt, ...)
 544 {
 545         va_list args;
 546         int ret = 0;
 547         struct device *dev;
 548
 549         if (bdi->dev)   /* The driver needs to use separate queues per device */
 550                 goto exit;
 551
 552         va_start(args, fmt);
 553         dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
 554         va_end(args);
 555         if (IS_ERR(dev)) {
 556                 ret = PTR_ERR(dev);
 557                 goto exit;
 558         }
 559
 560         spin_lock_bh(&bdi_lock);
 561         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
 562         spin_unlock_bh(&bdi_lock);
 563
 564         bdi->dev = dev;
 565
 566         /*
 567          * Just start the forker thread for our default backing_dev_info,
 568          * and add other bdi's to the list. They will get a thread created
 569          * on-demand when they need it.
 570          */
 571         if (bdi_cap_flush_forker(bdi)) {
 572                 struct bdi_writeback *wb = &bdi->wb;
 573
 574                 wb->task = kthread_run(bdi_forker_task, wb, "bdi-%s",
 575                                                 dev_name(dev));
 576                 if (IS_ERR(wb->task)) {
 577                         wb->task = NULL;
 578                         ret = -ENOMEM;
 579
 580                         bdi_remove_from_list(bdi);
 581                         goto exit;
 582                 }
 583         }
 584
 585         bdi_debug_register(bdi, dev_name(dev));
 586         set_bit(BDI_registered, &bdi->state);
 587 exit:
 588         return ret;
 589 }
 590 EXPORT_SYMBOL(bdi_register);
 591
 592 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
 593 {
 594         return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
 595 }
 596 EXPORT_SYMBOL(bdi_register_dev);
 597
 598 /*
 599  * Remove bdi from the global list and shutdown any threads we have running
 600  */
 601 static void bdi_wb_shutdown(struct backing_dev_info *bdi)
 602 {
 603         struct bdi_writeback *wb;
 604
 605         if (!bdi_cap_writeback_dirty(bdi))
 606                 return;
 607
 608         /*
 609          * If setup is pending, wait for that to complete first
 610          */
 611         wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
 612                         TASK_UNINTERRUPTIBLE);
 613
 614         /*
 615          * Make sure nobody finds us on the bdi_list anymore
 616          */
 617         bdi_remove_from_list(bdi);
 618
 619         /*
 620          * Finally, kill the kernel threads. We don't need to be RCU
 621          * safe anymore, since the bdi is gone from visibility. Force
 622          * unfreeze of the thread before calling kthread_stop(), otherwise
 623          * it would never exet if it is currently stuck in the refrigerator.
 624          */
 625         list_for_each_entry(wb, &bdi->wb_list, list) {
 626                 thaw_process(wb->task);
 627                 kthread_stop(wb->task);
 628         }
 629 }
 630
 631 /*
 632  * This bdi is going away now, make sure that no super_blocks point to it
 633  */
 634 static void bdi_prune_sb(struct backing_dev_info *bdi)
 635 {
 636         struct super_block *sb;
 637
 638         spin_lock(&sb_lock);
 639         list_for_each_entry(sb, &super_blocks, s_list) {
 640                 if (sb->s_bdi == bdi)
 641                         sb->s_bdi = NULL;
 642         }
 643         spin_unlock(&sb_lock);
 644 }
 645
 646 void bdi_unregister(struct backing_dev_info *bdi)
 647 {
 648         if (bdi->dev) {
 649                 bdi_set_min_ratio(bdi, 0);
 650                 bdi_prune_sb(bdi);
 651
 652                 if (!bdi_cap_flush_forker(bdi))
 653                         bdi_wb_shutdown(bdi);
 654                 bdi_debug_unregister(bdi);
 655                 device_unregister(bdi->dev);
 656                 bdi->dev = NULL;
 657         }
 658 }
 659 EXPORT_SYMBOL(bdi_unregister);
 660
 661 int bdi_init(struct backing_dev_info *bdi)
 662 {
 663         int i, err;
 664
 665         bdi->dev = NULL;
 666
 667         bdi->min_ratio = 0;
 668         bdi->max_ratio = 100;
 669         bdi->max_prop_frac = PROP_FRAC_BASE;
 670         spin_lock_init(&bdi->wb_lock);
 671         INIT_RCU_HEAD(&bdi->rcu_head);
 672         INIT_LIST_HEAD(&bdi->bdi_list);
 673         INIT_LIST_HEAD(&bdi->wb_list);
 674         INIT_LIST_HEAD(&bdi->work_list);
 675
 676         bdi_wb_init(&bdi->wb, bdi);
 677
 678         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
 679                 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
 680                 if (err)
 681                         goto err;
 682         }
 683
 684         bdi->dirty_exceeded = 0;
 685         err = prop_local_init_percpu(&bdi->completions);
 686
 687         if (err) {
 688 err:
 689                 while (i--)
 690                         percpu_counter_destroy(&bdi->bdi_stat[i]);
 691         }
 692
 693         return err;
 694 }
 695 EXPORT_SYMBOL(bdi_init);
 696
 697 void bdi_destroy(struct backing_dev_info *bdi)
 698 {
 699         int i;
 700
 701         /*
 702          * Splice our entries to the default_backing_dev_info, if this
 703          * bdi disappears
 704          */
 705         if (bdi_has_dirty_io(bdi)) {
 706                 struct bdi_writeback *dst = &default_backing_dev_info.wb;
 707
 708                 spin_lock(&inode_lock);
 709                 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
 710                 list_splice(&bdi->wb.b_io, &dst->b_io);
 711                 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
 712                 spin_unlock(&inode_lock);
 713         }
 714
 715         bdi_unregister(bdi);
 716
 717         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
 718                 percpu_counter_destroy(&bdi->bdi_stat[i]);
 719
 720         prop_local_destroy_percpu(&bdi->completions);
 721 }
 722 EXPORT_SYMBOL(bdi_destroy);
 723
 724 /*
 725  * For use from filesystems to quickly init and register a bdi associated
 726  * with dirty writeback
 727  */
 728 int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
 729                            unsigned int cap)
 730 {
 731         char tmp[32];
 732         int err;
 733
 734         bdi->name = name;
 735         bdi->capabilities = cap;
 736         err = bdi_init(bdi);
 737         if (err)
 738                 return err;
 739
 740         sprintf(tmp, "%.28s%s", name, "-%d");
 741         err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
 742         if (err) {
 743                 bdi_destroy(bdi);
 744                 return err;
 745         }
 746
 747         return 0;
 748 }
 749 EXPORT_SYMBOL(bdi_setup_and_register);
 750
 751 static wait_queue_head_t congestion_wqh[2] = {
 752                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
 753                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
 754         };
 755
 756 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
 757 {
 758         enum bdi_state bit;
 759         wait_queue_head_t *wqh = &congestion_wqh[sync];
 760
 761         bit = sync ? BDI_sync_congested : BDI_async_congested;
 762         clear_bit(bit, &bdi->state);
 763         smp_mb__after_clear_bit();
 764         if (waitqueue_active(wqh))
 765                 wake_up(wqh);
 766 }
 767 EXPORT_SYMBOL(clear_bdi_congested);
 768
 769 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
 770 {
 771         enum bdi_state bit;
 772
 773         bit = sync ? BDI_sync_congested : BDI_async_congested;
 774         set_bit(bit, &bdi->state);
 775 }
 776 EXPORT_SYMBOL(set_bdi_congested);
 777
 778 /**
 779  * congestion_wait - wait for a backing_dev to become uncongested
 780  * @sync: SYNC or ASYNC IO
 781  * @timeout: timeout in jiffies
 782  *
 783  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
 784  * write congestion.  If no backing_devs are congested then just wait for the
 785  * next write to be completed.
 786  */
 787 long congestion_wait(int sync, long timeout)
 788 {
 789         long ret;
 790         DEFINE_WAIT(wait);
 791         wait_queue_head_t *wqh = &congestion_wqh[sync];
 792
 793         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
 794         ret = io_schedule_timeout(timeout);
 795         finish_wait(wqh, &wait);
 796         return ret;
 797 }
 798 EXPORT_SYMBOL(congestion_wait);
 799