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 };
  33 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
  34
  35 static struct class *bdi_class;
  36
  37 /*
  38  * bdi_lock protects updates to bdi_list and bdi_pending_list, as well as
  39  * reader side protection for bdi_pending_list. bdi_list has RCU reader side
  40  * locking.
  41  */
  42 DEFINE_SPINLOCK(bdi_lock);
  43 LIST_HEAD(bdi_list);
  44 LIST_HEAD(bdi_pending_list);
  45
  46 static struct task_struct *sync_supers_tsk;
  47 static struct timer_list sync_supers_timer;
  48
  49 static int bdi_sync_supers(void *);
  50 static void sync_supers_timer_fn(unsigned long);
  51 static void arm_supers_timer(void);
  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_mask:          %8lx\n"
 109                    "wb_list:          %8u\n"
 110                    "wb_cnt:           %8u\n",
 111                    (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
 112                    (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
 113                    K(bdi_thresh), K(dirty_thresh),
 114                    K(background_thresh), nr_wb, nr_dirty, nr_io, nr_more_io,
 115                    !list_empty(&bdi->bdi_list), bdi->state, bdi->wb_mask,
 116                    !list_empty(&bdi->wb_list), bdi->wb_cnt);
 117 #undef K
 118
 119         return 0;
 120 }
 121
 122 static int bdi_debug_stats_open(struct inode *inode, struct file *file)
 123 {
 124         return single_open(file, bdi_debug_stats_show, inode->i_private);
 125 }
 126
 127 static const struct file_operations bdi_debug_stats_fops = {
 128         .open           = bdi_debug_stats_open,
 129         .read           = seq_read,
 130         .llseek         = seq_lseek,
 131         .release        = single_release,
 132 };
 133
 134 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
 135 {
 136         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
 137         bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
 138                                                bdi, &bdi_debug_stats_fops);
 139 }
 140
 141 static void bdi_debug_unregister(struct backing_dev_info *bdi)
 142 {
 143         debugfs_remove(bdi->debug_stats);
 144         debugfs_remove(bdi->debug_dir);
 145 }
 146 #else
 147 static inline void bdi_debug_init(void)
 148 {
 149 }
 150 static inline void bdi_debug_register(struct backing_dev_info *bdi,
 151                                       const char *name)
 152 {
 153 }
 154 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
 155 {
 156 }
 157 #endif
 158
 159 static ssize_t read_ahead_kb_store(struct device *dev,
 160                                   struct device_attribute *attr,
 161                                   const char *buf, size_t count)
 162 {
 163         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 164         char *end;
 165         unsigned long read_ahead_kb;
 166         ssize_t ret = -EINVAL;
 167
 168         read_ahead_kb = simple_strtoul(buf, &end, 10);
 169         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
 170                 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
 171                 ret = count;
 172         }
 173         return ret;
 174 }
 175
 176 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
 177
 178 #define BDI_SHOW(name, expr)                                            \
 179 static ssize_t name##_show(struct device *dev,                          \
 180                            struct device_attribute *attr, char *page)   \
 181 {                                                                       \
 182         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
 183                                                                         \
 184         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
 185 }
 186
 187 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
 188
 189 static ssize_t min_ratio_store(struct device *dev,
 190                 struct device_attribute *attr, const char *buf, size_t count)
 191 {
 192         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 193         char *end;
 194         unsigned int ratio;
 195         ssize_t ret = -EINVAL;
 196
 197         ratio = simple_strtoul(buf, &end, 10);
 198         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
 199                 ret = bdi_set_min_ratio(bdi, ratio);
 200                 if (!ret)
 201                         ret = count;
 202         }
 203         return ret;
 204 }
 205 BDI_SHOW(min_ratio, bdi->min_ratio)
 206
 207 static ssize_t max_ratio_store(struct device *dev,
 208                 struct device_attribute *attr, const char *buf, size_t count)
 209 {
 210         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 211         char *end;
 212         unsigned int ratio;
 213         ssize_t ret = -EINVAL;
 214
 215         ratio = simple_strtoul(buf, &end, 10);
 216         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
 217                 ret = bdi_set_max_ratio(bdi, ratio);
 218                 if (!ret)
 219                         ret = count;
 220         }
 221         return ret;
 222 }
 223 BDI_SHOW(max_ratio, bdi->max_ratio)
 224
 225 #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
 226
 227 static struct device_attribute bdi_dev_attrs[] = {
 228         __ATTR_RW(read_ahead_kb),
 229         __ATTR_RW(min_ratio),
 230         __ATTR_RW(max_ratio),
 231         __ATTR_NULL,
 232 };
 233
 234 static __init int bdi_class_init(void)
 235 {
 236         bdi_class = class_create(THIS_MODULE, "bdi");
 237         if (IS_ERR(bdi_class))
 238                 return PTR_ERR(bdi_class);
 239
 240         bdi_class->dev_attrs = bdi_dev_attrs;
 241         bdi_debug_init();
 242         return 0;
 243 }
 244 postcore_initcall(bdi_class_init);
 245
 246 static int __init default_bdi_init(void)
 247 {
 248         int err;
 249
 250         sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
 251         BUG_ON(IS_ERR(sync_supers_tsk));
 252
 253         init_timer(&sync_supers_timer);
 254         setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
 255         arm_supers_timer();
 256
 257         err = bdi_init(&default_backing_dev_info);
 258         if (!err)
 259                 bdi_register(&default_backing_dev_info, NULL, "default");
 260
 261         return err;
 262 }
 263 subsys_initcall(default_bdi_init);
 264
 265 static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
 266 {
 267         memset(wb, 0, sizeof(*wb));
 268
 269         wb->bdi = bdi;
 270         wb->last_old_flush = jiffies;
 271         INIT_LIST_HEAD(&wb->b_dirty);
 272         INIT_LIST_HEAD(&wb->b_io);
 273         INIT_LIST_HEAD(&wb->b_more_io);
 274 }
 275
 276 static void bdi_task_init(struct backing_dev_info *bdi,
 277                           struct bdi_writeback *wb)
 278 {
 279         struct task_struct *tsk = current;
 280
 281         spin_lock(&bdi->wb_lock);
 282         list_add_tail_rcu(&wb->list, &bdi->wb_list);
 283         spin_unlock(&bdi->wb_lock);
 284
 285         tsk->flags |= PF_FLUSHER | PF_SWAPWRITE;
 286         set_freezable();
 287
 288         /*
 289          * Our parent may run at a different priority, just set us to normal
 290          */
 291         set_user_nice(tsk, 0);
 292 }
 293
 294 static int bdi_start_fn(void *ptr)
 295 {
 296         struct bdi_writeback *wb = ptr;
 297         struct backing_dev_info *bdi = wb->bdi;
 298         int ret;
 299
 300         /*
 301          * Add us to the active bdi_list
 302          */
 303         spin_lock_bh(&bdi_lock);
 304         list_add_rcu(&bdi->bdi_list, &bdi_list);
 305         spin_unlock_bh(&bdi_lock);
 306
 307         bdi_task_init(bdi, wb);
 308
 309         /*
 310          * Clear pending bit and wakeup anybody waiting to tear us down
 311          */
 312         clear_bit(BDI_pending, &bdi->state);
 313         smp_mb__after_clear_bit();
 314         wake_up_bit(&bdi->state, BDI_pending);
 315
 316         ret = bdi_writeback_task(wb);
 317
 318         /*
 319          * Remove us from the list
 320          */
 321         spin_lock(&bdi->wb_lock);
 322         list_del_rcu(&wb->list);
 323         spin_unlock(&bdi->wb_lock);
 324
 325         /*
 326          * Flush any work that raced with us exiting. No new work
 327          * will be added, since this bdi isn't discoverable anymore.
 328          */
 329         if (!list_empty(&bdi->work_list))
 330                 wb_do_writeback(wb, 1);
 331
 332         wb->task = NULL;
 333         return ret;
 334 }
 335
 336 int bdi_has_dirty_io(struct backing_dev_info *bdi)
 337 {
 338         return wb_has_dirty_io(&bdi->wb);
 339 }
 340
 341 static void bdi_flush_io(struct backing_dev_info *bdi)
 342 {
 343         struct writeback_control wbc = {
 344                 .bdi                    = bdi,
 345                 .sync_mode              = WB_SYNC_NONE,
 346                 .older_than_this        = NULL,
 347                 .range_cyclic           = 1,
 348                 .nr_to_write            = 1024,
 349         };
 350
 351         writeback_inodes_wbc(&wbc);
 352 }
 353
 354 /*
 355  * kupdated() used to do this. We cannot do it from the bdi_forker_task()
 356  * or we risk deadlocking on ->s_umount. The longer term solution would be
 357  * to implement sync_supers_bdi() or similar and simply do it from the
 358  * bdi writeback tasks individually.
 359  */
 360 static int bdi_sync_supers(void *unused)
 361 {
 362         set_user_nice(current, 0);
 363
 364         while (!kthread_should_stop()) {
 365                 set_current_state(TASK_INTERRUPTIBLE);
 366                 schedule();
 367
 368                 /*
 369                  * Do this periodically, like kupdated() did before.
 370                  */
 371                 sync_supers();
 372         }
 373
 374         return 0;
 375 }
 376
 377 static void arm_supers_timer(void)
 378 {
 379         unsigned long next;
 380
 381         next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
 382         mod_timer(&sync_supers_timer, round_jiffies_up(next));
 383 }
 384
 385 static void sync_supers_timer_fn(unsigned long unused)
 386 {
 387         wake_up_process(sync_supers_tsk);
 388         arm_supers_timer();
 389 }
 390
 391 static int bdi_forker_task(void *ptr)
 392 {
 393         struct bdi_writeback *me = ptr;
 394
 395         bdi_task_init(me->bdi, me);
 396
 397         for (;;) {
 398                 struct backing_dev_info *bdi, *tmp;
 399                 struct bdi_writeback *wb;
 400
 401                 /*
 402                  * Temporary measure, we want to make sure we don't see
 403                  * dirty data on the default backing_dev_info
 404                  */
 405                 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list))
 406                         wb_do_writeback(me, 0);
 407
 408                 spin_lock_bh(&bdi_lock);
 409
 410                 /*
 411                  * Check if any existing bdi's have dirty data without
 412                  * a thread registered. If so, set that up.
 413                  */
 414                 list_for_each_entry_safe(bdi, tmp, &bdi_list, bdi_list) {
 415                         if (bdi->wb.task)
 416                                 continue;
 417                         if (list_empty(&bdi->work_list) &&
 418                             !bdi_has_dirty_io(bdi))
 419                                 continue;
 420
 421                         bdi_add_default_flusher_task(bdi);
 422                 }
 423
 424                 set_current_state(TASK_INTERRUPTIBLE);
 425
 426                 if (list_empty(&bdi_pending_list)) {
 427                         unsigned long wait;
 428
 429                         spin_unlock_bh(&bdi_lock);
 430                         wait = msecs_to_jiffies(dirty_writeback_interval * 10);
 431                         schedule_timeout(wait);
 432                         try_to_freeze();
 433                         continue;
 434                 }
 435
 436                 __set_current_state(TASK_RUNNING);
 437
 438                 /*
 439                  * This is our real job - check for pending entries in
 440                  * bdi_pending_list, and create the tasks that got added
 441                  */
 442                 bdi = list_entry(bdi_pending_list.next, struct backing_dev_info,
 443                                  bdi_list);
 444                 list_del_init(&bdi->bdi_list);
 445                 spin_unlock_bh(&bdi_lock);
 446
 447                 wb = &bdi->wb;
 448                 wb->task = kthread_run(bdi_start_fn, wb, "flush-%s",
 449                                         dev_name(bdi->dev));
 450                 /*
 451                  * If task creation fails, then readd the bdi to
 452                  * the pending list and force writeout of the bdi
 453                  * from this forker thread. That will free some memory
 454                  * and we can try again.
 455                  */
 456                 if (IS_ERR(wb->task)) {
 457                         wb->task = NULL;
 458
 459                         /*
 460                          * Add this 'bdi' to the back, so we get
 461                          * a chance to flush other bdi's to free
 462                          * memory.
 463                          */
 464                         spin_lock_bh(&bdi_lock);
 465                         list_add_tail(&bdi->bdi_list, &bdi_pending_list);
 466                         spin_unlock_bh(&bdi_lock);
 467
 468                         bdi_flush_io(bdi);
 469                 }
 470         }
 471
 472         return 0;
 473 }
 474
 475 static void bdi_add_to_pending(struct rcu_head *head)
 476 {
 477         struct backing_dev_info *bdi;
 478
 479         bdi = container_of(head, struct backing_dev_info, rcu_head);
 480         INIT_LIST_HEAD(&bdi->bdi_list);
 481
 482         spin_lock(&bdi_lock);
 483         list_add_tail(&bdi->bdi_list, &bdi_pending_list);
 484         spin_unlock(&bdi_lock);
 485
 486         /*
 487          * We are now on the pending list, wake up bdi_forker_task()
 488          * to finish the job and add us back to the active bdi_list
 489          */
 490         wake_up_process(default_backing_dev_info.wb.task);
 491 }
 492
 493 /*
 494  * Add the default flusher task that gets created for any bdi
 495  * that has dirty data pending writeout
 496  */
 497 void static bdi_add_default_flusher_task(struct backing_dev_info *bdi)
 498 {
 499         if (!bdi_cap_writeback_dirty(bdi))
 500                 return;
 501
 502         if (WARN_ON(!test_bit(BDI_registered, &bdi->state))) {
 503                 printk(KERN_ERR "bdi %p/%s is not registered!\n",
 504                                                         bdi, bdi->name);
 505                 return;
 506         }
 507
 508         /*
 509          * Check with the helper whether to proceed adding a task. Will only
 510          * abort if we two or more simultanous calls to
 511          * bdi_add_default_flusher_task() occured, further additions will block
 512          * waiting for previous additions to finish.
 513          */
 514         if (!test_and_set_bit(BDI_pending, &bdi->state)) {
 515                 list_del_rcu(&bdi->bdi_list);
 516
 517                 /*
 518                  * We must wait for the current RCU period to end before
 519                  * moving to the pending list. So schedule that operation
 520                  * from an RCU callback.
 521                  */
 522                 call_rcu(&bdi->rcu_head, bdi_add_to_pending);
 523         }
 524 }
 525
 526 /*
 527  * Remove bdi from bdi_list, and ensure that it is no longer visible
 528  */
 529 static void bdi_remove_from_list(struct backing_dev_info *bdi)
 530 {
 531         spin_lock_bh(&bdi_lock);
 532         list_del_rcu(&bdi->bdi_list);
 533         spin_unlock_bh(&bdi_lock);
 534
 535         synchronize_rcu();
 536 }
 537
 538 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 539                 const char *fmt, ...)
 540 {
 541         va_list args;
 542         int ret = 0;
 543         struct device *dev;
 544
 545         if (bdi->dev)   /* The driver needs to use separate queues per device */
 546                 goto exit;
 547
 548         va_start(args, fmt);
 549         dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
 550         va_end(args);
 551         if (IS_ERR(dev)) {
 552                 ret = PTR_ERR(dev);
 553                 goto exit;
 554         }
 555
 556         spin_lock_bh(&bdi_lock);
 557         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
 558         spin_unlock_bh(&bdi_lock);
 559
 560         bdi->dev = dev;
 561
 562         /*
 563          * Just start the forker thread for our default backing_dev_info,
 564          * and add other bdi's to the list. They will get a thread created
 565          * on-demand when they need it.
 566          */
 567         if (bdi_cap_flush_forker(bdi)) {
 568                 struct bdi_writeback *wb = &bdi->wb;
 569
 570                 wb->task = kthread_run(bdi_forker_task, wb, "bdi-%s",
 571                                                 dev_name(dev));
 572                 if (IS_ERR(wb->task)) {
 573                         wb->task = NULL;
 574                         ret = -ENOMEM;
 575
 576                         bdi_remove_from_list(bdi);
 577                         goto exit;
 578                 }
 579         }
 580
 581         bdi_debug_register(bdi, dev_name(dev));
 582         set_bit(BDI_registered, &bdi->state);
 583 exit:
 584         return ret;
 585 }
 586 EXPORT_SYMBOL(bdi_register);
 587
 588 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
 589 {
 590         return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
 591 }
 592 EXPORT_SYMBOL(bdi_register_dev);
 593
 594 /*
 595  * Remove bdi from the global list and shutdown any threads we have running
 596  */
 597 static void bdi_wb_shutdown(struct backing_dev_info *bdi)
 598 {
 599         struct bdi_writeback *wb;
 600
 601         if (!bdi_cap_writeback_dirty(bdi))
 602                 return;
 603
 604         /*
 605          * If setup is pending, wait for that to complete first
 606          */
 607         wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
 608                         TASK_UNINTERRUPTIBLE);
 609
 610         /*
 611          * Make sure nobody finds us on the bdi_list anymore
 612          */
 613         bdi_remove_from_list(bdi);
 614
 615         /*
 616          * Finally, kill the kernel threads. We don't need to be RCU
 617          * safe anymore, since the bdi is gone from visibility. Force
 618          * unfreeze of the thread before calling kthread_stop(), otherwise
 619          * it would never exet if it is currently stuck in the refrigerator.
 620          */
 621         list_for_each_entry(wb, &bdi->wb_list, list) {
 622                 thaw_process(wb->task);
 623                 kthread_stop(wb->task);
 624         }
 625 }
 626
 627 /*
 628  * This bdi is going away now, make sure that no super_blocks point to it
 629  */
 630 static void bdi_prune_sb(struct backing_dev_info *bdi)
 631 {
 632         struct super_block *sb;
 633
 634         spin_lock(&sb_lock);
 635         list_for_each_entry(sb, &super_blocks, s_list) {
 636                 if (sb->s_bdi == bdi)
 637                         sb->s_bdi = NULL;
 638         }
 639         spin_unlock(&sb_lock);
 640 }
 641
 642 void bdi_unregister(struct backing_dev_info *bdi)
 643 {
 644         if (bdi->dev) {
 645                 bdi_prune_sb(bdi);
 646
 647                 if (!bdi_cap_flush_forker(bdi))
 648                         bdi_wb_shutdown(bdi);
 649                 bdi_debug_unregister(bdi);
 650                 device_unregister(bdi->dev);
 651                 bdi->dev = NULL;
 652         }
 653 }
 654 EXPORT_SYMBOL(bdi_unregister);
 655
 656 int bdi_init(struct backing_dev_info *bdi)
 657 {
 658         int i, err;
 659
 660         bdi->dev = NULL;
 661
 662         bdi->min_ratio = 0;
 663         bdi->max_ratio = 100;
 664         bdi->max_prop_frac = PROP_FRAC_BASE;
 665         spin_lock_init(&bdi->wb_lock);
 666         INIT_RCU_HEAD(&bdi->rcu_head);
 667         INIT_LIST_HEAD(&bdi->bdi_list);
 668         INIT_LIST_HEAD(&bdi->wb_list);
 669         INIT_LIST_HEAD(&bdi->work_list);
 670
 671         bdi_wb_init(&bdi->wb, bdi);
 672
 673         /*
 674          * Just one thread support for now, hard code mask and count
 675          */
 676         bdi->wb_mask = 1;
 677         bdi->wb_cnt = 1;
 678
 679         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
 680                 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
 681                 if (err)
 682                         goto err;
 683         }
 684
 685         bdi->dirty_exceeded = 0;
 686         err = prop_local_init_percpu(&bdi->completions);
 687
 688         if (err) {
 689 err:
 690                 while (i--)
 691                         percpu_counter_destroy(&bdi->bdi_stat[i]);
 692         }
 693
 694         return err;
 695 }
 696 EXPORT_SYMBOL(bdi_init);
 697
 698 void bdi_destroy(struct backing_dev_info *bdi)
 699 {
 700         int i;
 701
 702         /*
 703          * Splice our entries to the default_backing_dev_info, if this
 704          * bdi disappears
 705          */
 706         if (bdi_has_dirty_io(bdi)) {
 707                 struct bdi_writeback *dst = &default_backing_dev_info.wb;
 708
 709                 spin_lock(&inode_lock);
 710                 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
 711                 list_splice(&bdi->wb.b_io, &dst->b_io);
 712                 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
 713                 spin_unlock(&inode_lock);
 714         }
 715
 716         bdi_unregister(bdi);
 717
 718         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
 719                 percpu_counter_destroy(&bdi->bdi_stat[i]);
 720
 721         prop_local_destroy_percpu(&bdi->completions);
 722 }
 723 EXPORT_SYMBOL(bdi_destroy);
 724
 725 /*
 726  * For use from filesystems to quickly init and register a bdi associated
 727  * with dirty writeback
 728  */
 729 int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
 730                            unsigned int cap)
 731 {
 732         char tmp[32];
 733         int err;
 734
 735         bdi->name = name;
 736         bdi->capabilities = cap;
 737         err = bdi_init(bdi);
 738         if (err)
 739                 return err;
 740
 741         sprintf(tmp, "%.28s%s", name, "-%d");
 742         err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
 743         if (err) {
 744                 bdi_destroy(bdi);
 745                 return err;
 746         }
 747
 748         return 0;
 749 }
 750 EXPORT_SYMBOL(bdi_setup_and_register);
 751
 752 static wait_queue_head_t congestion_wqh[2] = {
 753                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
 754                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
 755         };
 756
 757 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
 758 {
 759         enum bdi_state bit;
 760         wait_queue_head_t *wqh = &congestion_wqh[sync];
 761
 762         bit = sync ? BDI_sync_congested : BDI_async_congested;
 763         clear_bit(bit, &bdi->state);
 764         smp_mb__after_clear_bit();
 765         if (waitqueue_active(wqh))
 766                 wake_up(wqh);
 767 }
 768 EXPORT_SYMBOL(clear_bdi_congested);
 769
 770 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
 771 {
 772         enum bdi_state bit;
 773
 774         bit = sync ? BDI_sync_congested : BDI_async_congested;
 775         set_bit(bit, &bdi->state);
 776 }
 777 EXPORT_SYMBOL(set_bdi_congested);
 778
 779 /**
 780  * congestion_wait - wait for a backing_dev to become uncongested
 781  * @sync: SYNC or ASYNC IO
 782  * @timeout: timeout in jiffies
 783  *
 784  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
 785  * write congestion.  If no backing_devs are congested then just wait for the
 786  * next write to be completed.
 787  */
 788 long congestion_wait(int sync, long timeout)
 789 {
 790         long ret;
 791         DEFINE_WAIT(wait);
 792         wait_queue_head_t *wqh = &congestion_wqh[sync];
 793
 794         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
 795         ret = io_schedule_timeout(timeout);
 796         finish_wait(wqh, &wait);
 797         return ret;
 798 }
 799 EXPORT_SYMBOL(congestion_wait);
 800