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 struct backing_dev_info default_backing_dev_info = {
  18         .name           = "default",
  19         .ra_pages       = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
  20         .state          = 0,
  21         .capabilities   = BDI_CAP_MAP_COPY,
  22 };
  23 EXPORT_SYMBOL_GPL(default_backing_dev_info);
  24
  25 struct backing_dev_info noop_backing_dev_info = {
  26         .name           = "noop",
  27         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
  28 };
  29 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
  30
  31 static struct class *bdi_class;
  32
  33 /*
  34  * bdi_lock protects updates to bdi_list and bdi_pending_list, as well as
  35  * reader side protection for bdi_pending_list. bdi_list has RCU reader side
  36  * locking.
  37  */
  38 DEFINE_SPINLOCK(bdi_lock);
  39 LIST_HEAD(bdi_list);
  40 LIST_HEAD(bdi_pending_list);
  41
  42 static struct task_struct *sync_supers_tsk;
  43 static struct timer_list sync_supers_timer;
  44
  45 static int bdi_sync_supers(void *);
  46 static void sync_supers_timer_fn(unsigned long);
  47
  48 void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
  49 {
  50         if (wb1 < wb2) {
  51                 spin_lock(&wb1->list_lock);
  52                 spin_lock_nested(&wb2->list_lock, 1);
  53         } else {
  54                 spin_lock(&wb2->list_lock);
  55                 spin_lock_nested(&wb1->list_lock, 1);
  56         }
  57 }
  58
  59 #ifdef CONFIG_DEBUG_FS
  60 #include <linux/debugfs.h>
  61 #include <linux/seq_file.h>
  62
  63 static struct dentry *bdi_debug_root;
  64
  65 static void bdi_debug_init(void)
  66 {
  67         bdi_debug_root = debugfs_create_dir("bdi", NULL);
  68 }
  69
  70 static int bdi_debug_stats_show(struct seq_file *m, void *v)
  71 {
  72         struct backing_dev_info *bdi = m->private;
  73         struct bdi_writeback *wb = &bdi->wb;
  74         unsigned long background_thresh;
  75         unsigned long dirty_thresh;
  76         unsigned long bdi_thresh;
  77         unsigned long nr_dirty, nr_io, nr_more_io;
  78         struct inode *inode;
  79
  80         nr_dirty = nr_io = nr_more_io = 0;
  81         spin_lock(&wb->list_lock);
  82         list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
  83                 nr_dirty++;
  84         list_for_each_entry(inode, &wb->b_io, i_wb_list)
  85                 nr_io++;
  86         list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
  87                 nr_more_io++;
  88         spin_unlock(&wb->list_lock);
  89
  90         global_dirty_limits(&background_thresh, &dirty_thresh);
  91         bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
  92
  93 #define K(x) ((x) << (PAGE_SHIFT - 10))
  94         seq_printf(m,
  95                    "BdiWriteback:       %10lu kB\n"
  96                    "BdiReclaimable:     %10lu kB\n"
  97                    "BdiDirtyThresh:     %10lu kB\n"
  98                    "DirtyThresh:        %10lu kB\n"
  99                    "BackgroundThresh:   %10lu kB\n"
 100                    "BdiWritten:         %10lu kB\n"
 101                    "BdiWriteBandwidth:  %10lu kBps\n"
 102                    "b_dirty:            %10lu\n"
 103                    "b_io:               %10lu\n"
 104                    "b_more_io:          %10lu\n"
 105                    "bdi_list:           %10u\n"
 106                    "state:              %10lx\n",
 107                    (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
 108                    (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
 109                    K(bdi_thresh),
 110                    K(dirty_thresh),
 111                    K(background_thresh),
 112                    (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
 113                    (unsigned long) K(bdi->write_bandwidth),
 114                    nr_dirty,
 115                    nr_io,
 116                    nr_more_io,
 117                    !list_empty(&bdi->bdi_list), bdi->state);
 118 #undef K
 119
 120         return 0;
 121 }
 122
 123 static int bdi_debug_stats_open(struct inode *inode, struct file *file)
 124 {
 125         return single_open(file, bdi_debug_stats_show, inode->i_private);
 126 }
 127
 128 static const struct file_operations bdi_debug_stats_fops = {
 129         .open           = bdi_debug_stats_open,
 130         .read           = seq_read,
 131         .llseek         = seq_lseek,
 132         .release        = single_release,
 133 };
 134
 135 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
 136 {
 137         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
 138         bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
 139                                                bdi, &bdi_debug_stats_fops);
 140 }
 141
 142 static void bdi_debug_unregister(struct backing_dev_info *bdi)
 143 {
 144         debugfs_remove(bdi->debug_stats);
 145         debugfs_remove(bdi->debug_dir);
 146 }
 147 #else
 148 static inline void bdi_debug_init(void)
 149 {
 150 }
 151 static inline void bdi_debug_register(struct backing_dev_info *bdi,
 152                                       const char *name)
 153 {
 154 }
 155 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
 156 {
 157 }
 158 #endif
 159
 160 static ssize_t read_ahead_kb_store(struct device *dev,
 161                                   struct device_attribute *attr,
 162                                   const char *buf, size_t count)
 163 {
 164         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 165         char *end;
 166         unsigned long read_ahead_kb;
 167         ssize_t ret = -EINVAL;
 168
 169         read_ahead_kb = simple_strtoul(buf, &end, 10);
 170         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
 171                 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
 172                 ret = count;
 173         }
 174         return ret;
 175 }
 176
 177 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
 178
 179 #define BDI_SHOW(name, expr)                                            \
 180 static ssize_t name##_show(struct device *dev,                          \
 181                            struct device_attribute *attr, char *page)   \
 182 {                                                                       \
 183         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
 184                                                                         \
 185         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
 186 }
 187
 188 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
 189
 190 static ssize_t min_ratio_store(struct device *dev,
 191                 struct device_attribute *attr, const char *buf, size_t count)
 192 {
 193         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 194         char *end;
 195         unsigned int ratio;
 196         ssize_t ret = -EINVAL;
 197
 198         ratio = simple_strtoul(buf, &end, 10);
 199         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
 200                 ret = bdi_set_min_ratio(bdi, ratio);
 201                 if (!ret)
 202                         ret = count;
 203         }
 204         return ret;
 205 }
 206 BDI_SHOW(min_ratio, bdi->min_ratio)
 207
 208 static ssize_t max_ratio_store(struct device *dev,
 209                 struct device_attribute *attr, const char *buf, size_t count)
 210 {
 211         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 212         char *end;
 213         unsigned int ratio;
 214         ssize_t ret = -EINVAL;
 215
 216         ratio = simple_strtoul(buf, &end, 10);
 217         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
 218                 ret = bdi_set_max_ratio(bdi, ratio);
 219                 if (!ret)
 220                         ret = count;
 221         }
 222         return ret;
 223 }
 224 BDI_SHOW(max_ratio, bdi->max_ratio)
 225
 226 #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
 227
 228 static struct device_attribute bdi_dev_attrs[] = {
 229         __ATTR_RW(read_ahead_kb),
 230         __ATTR_RW(min_ratio),
 231         __ATTR_RW(max_ratio),
 232         __ATTR_NULL,
 233 };
 234
 235 static __init int bdi_class_init(void)
 236 {
 237         bdi_class = class_create(THIS_MODULE, "bdi");
 238         if (IS_ERR(bdi_class))
 239                 return PTR_ERR(bdi_class);
 240
 241         bdi_class->dev_attrs = bdi_dev_attrs;
 242         bdi_debug_init();
 243         return 0;
 244 }
 245 postcore_initcall(bdi_class_init);
 246
 247 static int __init default_bdi_init(void)
 248 {
 249         int err;
 250
 251         sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
 252         BUG_ON(IS_ERR(sync_supers_tsk));
 253
 254         setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
 255         bdi_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         err = bdi_init(&noop_backing_dev_info);
 261
 262         return err;
 263 }
 264 subsys_initcall(default_bdi_init);
 265
 266 int bdi_has_dirty_io(struct backing_dev_info *bdi)
 267 {
 268         return wb_has_dirty_io(&bdi->wb);
 269 }
 270
 271 /*
 272  * kupdated() used to do this. We cannot do it from the bdi_forker_thread()
 273  * or we risk deadlocking on ->s_umount. The longer term solution would be
 274  * to implement sync_supers_bdi() or similar and simply do it from the
 275  * bdi writeback thread individually.
 276  */
 277 static int bdi_sync_supers(void *unused)
 278 {
 279         set_user_nice(current, 0);
 280
 281         while (!kthread_should_stop()) {
 282                 set_current_state(TASK_INTERRUPTIBLE);
 283                 schedule();
 284
 285                 /*
 286                  * Do this periodically, like kupdated() did before.
 287                  */
 288                 sync_supers();
 289         }
 290
 291         return 0;
 292 }
 293
 294 void bdi_arm_supers_timer(void)
 295 {
 296         unsigned long next;
 297
 298         if (!dirty_writeback_interval)
 299                 return;
 300
 301         next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
 302         mod_timer(&sync_supers_timer, round_jiffies_up(next));
 303 }
 304
 305 static void sync_supers_timer_fn(unsigned long unused)
 306 {
 307         wake_up_process(sync_supers_tsk);
 308         bdi_arm_supers_timer();
 309 }
 310
 311 static void wakeup_timer_fn(unsigned long data)
 312 {
 313         struct backing_dev_info *bdi = (struct backing_dev_info *)data;
 314
 315         spin_lock_bh(&bdi->wb_lock);
 316         if (bdi->wb.task) {
 317                 trace_writeback_wake_thread(bdi);
 318                 wake_up_process(bdi->wb.task);
 319         } else {
 320                 /*
 321                  * When bdi tasks are inactive for long time, they are killed.
 322                  * In this case we have to wake-up the forker thread which
 323                  * should create and run the bdi thread.
 324                  */
 325                 trace_writeback_wake_forker_thread(bdi);
 326                 wake_up_process(default_backing_dev_info.wb.task);
 327         }
 328         spin_unlock_bh(&bdi->wb_lock);
 329 }
 330
 331 /*
 332  * This function is used when the first inode for this bdi is marked dirty. It
 333  * wakes-up the corresponding bdi thread which should then take care of the
 334  * periodic background write-out of dirty inodes. Since the write-out would
 335  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
 336  * set up a timer which wakes the bdi thread up later.
 337  *
 338  * Note, we wouldn't bother setting up the timer, but this function is on the
 339  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
 340  * by delaying the wake-up.
 341  */
 342 void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
 343 {
 344         unsigned long timeout;
 345
 346         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
 347         mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout);
 348 }
 349
 350 /*
 351  * Calculate the longest interval (jiffies) bdi threads are allowed to be
 352  * inactive.
 353  */
 354 static unsigned long bdi_longest_inactive(void)
 355 {
 356         unsigned long interval;
 357
 358         interval = msecs_to_jiffies(dirty_writeback_interval * 10);
 359         return max(5UL * 60 * HZ, interval);
 360 }
 361
 362 /*
 363  * Clear pending bit and wakeup anybody waiting for flusher thread creation or
 364  * shutdown
 365  */
 366 static void bdi_clear_pending(struct backing_dev_info *bdi)
 367 {
 368         clear_bit(BDI_pending, &bdi->state);
 369         smp_mb__after_clear_bit();
 370         wake_up_bit(&bdi->state, BDI_pending);
 371 }
 372
 373 static int bdi_forker_thread(void *ptr)
 374 {
 375         struct bdi_writeback *me = ptr;
 376
 377         current->flags |= PF_SWAPWRITE;
 378         set_freezable();
 379
 380         /*
 381          * Our parent may run at a different priority, just set us to normal
 382          */
 383         set_user_nice(current, 0);
 384
 385         for (;;) {
 386                 struct task_struct *task = NULL;
 387                 struct backing_dev_info *bdi;
 388                 enum {
 389                         NO_ACTION,   /* Nothing to do */
 390                         FORK_THREAD, /* Fork bdi thread */
 391                         KILL_THREAD, /* Kill inactive bdi thread */
 392                 } action = NO_ACTION;
 393
 394                 /*
 395                  * Temporary measure, we want to make sure we don't see
 396                  * dirty data on the default backing_dev_info
 397                  */
 398                 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
 399                         del_timer(&me->wakeup_timer);
 400                         wb_do_writeback(me, 0);
 401                 }
 402
 403                 spin_lock_bh(&bdi_lock);
 404                 set_current_state(TASK_INTERRUPTIBLE);
 405
 406                 list_for_each_entry(bdi, &bdi_list, bdi_list) {
 407                         bool have_dirty_io;
 408
 409                         if (!bdi_cap_writeback_dirty(bdi) ||
 410                              bdi_cap_flush_forker(bdi))
 411                                 continue;
 412
 413                         WARN(!test_bit(BDI_registered, &bdi->state),
 414                              "bdi %p/%s is not registered!\n", bdi, bdi->name);
 415
 416                         have_dirty_io = !list_empty(&bdi->work_list) ||
 417                                         wb_has_dirty_io(&bdi->wb);
 418
 419                         /*
 420                          * If the bdi has work to do, but the thread does not
 421                          * exist - create it.
 422                          */
 423                         if (!bdi->wb.task && have_dirty_io) {
 424                                 /*
 425                                  * Set the pending bit - if someone will try to
 426                                  * unregister this bdi - it'll wait on this bit.
 427                                  */
 428                                 set_bit(BDI_pending, &bdi->state);
 429                                 action = FORK_THREAD;
 430                                 break;
 431                         }
 432
 433                         spin_lock(&bdi->wb_lock);
 434
 435                         /*
 436                          * If there is no work to do and the bdi thread was
 437                          * inactive long enough - kill it. The wb_lock is taken
 438                          * to make sure no-one adds more work to this bdi and
 439                          * wakes the bdi thread up.
 440                          */
 441                         if (bdi->wb.task && !have_dirty_io &&
 442                             time_after(jiffies, bdi->wb.last_active +
 443                                                 bdi_longest_inactive())) {
 444                                 task = bdi->wb.task;
 445                                 bdi->wb.task = NULL;
 446                                 spin_unlock(&bdi->wb_lock);
 447                                 set_bit(BDI_pending, &bdi->state);
 448                                 action = KILL_THREAD;
 449                                 break;
 450                         }
 451                         spin_unlock(&bdi->wb_lock);
 452                 }
 453                 spin_unlock_bh(&bdi_lock);
 454
 455                 /* Keep working if default bdi still has things to do */
 456                 if (!list_empty(&me->bdi->work_list))
 457                         __set_current_state(TASK_RUNNING);
 458
 459                 switch (action) {
 460                 case FORK_THREAD:
 461                         __set_current_state(TASK_RUNNING);
 462                         task = kthread_create(bdi_writeback_thread, &bdi->wb,
 463                                               "flush-%s", dev_name(bdi->dev));
 464                         if (IS_ERR(task)) {
 465                                 /*
 466                                  * If thread creation fails, force writeout of
 467                                  * the bdi from the thread. Hopefully 1024 is
 468                                  * large enough for efficient IO.
 469                                  */
 470                                 writeback_inodes_wb(&bdi->wb, 1024);
 471                         } else {
 472                                 /*
 473                                  * The spinlock makes sure we do not lose
 474                                  * wake-ups when racing with 'bdi_queue_work()'.
 475                                  * And as soon as the bdi thread is visible, we
 476                                  * can start it.
 477                                  */
 478                                 spin_lock_bh(&bdi->wb_lock);
 479                                 bdi->wb.task = task;
 480                                 spin_unlock_bh(&bdi->wb_lock);
 481                                 wake_up_process(task);
 482                         }
 483                         bdi_clear_pending(bdi);
 484                         break;
 485
 486                 case KILL_THREAD:
 487                         __set_current_state(TASK_RUNNING);
 488                         kthread_stop(task);
 489                         bdi_clear_pending(bdi);
 490                         break;
 491
 492                 case NO_ACTION:
 493                         if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
 494                                 /*
 495                                  * There are no dirty data. The only thing we
 496                                  * should now care about is checking for
 497                                  * inactive bdi threads and killing them. Thus,
 498                                  * let's sleep for longer time, save energy and
 499                                  * be friendly for battery-driven devices.
 500                                  */
 501                                 schedule_timeout(bdi_longest_inactive());
 502                         else
 503                                 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
 504                         try_to_freeze();
 505                         break;
 506                 }
 507         }
 508
 509         return 0;
 510 }
 511
 512 /*
 513  * Remove bdi from bdi_list, and ensure that it is no longer visible
 514  */
 515 static void bdi_remove_from_list(struct backing_dev_info *bdi)
 516 {
 517         spin_lock_bh(&bdi_lock);
 518         list_del_rcu(&bdi->bdi_list);
 519         spin_unlock_bh(&bdi_lock);
 520
 521         synchronize_rcu_expedited();
 522 }
 523
 524 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 525                 const char *fmt, ...)
 526 {
 527         va_list args;
 528         struct device *dev;
 529
 530         if (bdi->dev)   /* The driver needs to use separate queues per device */
 531                 return 0;
 532
 533         va_start(args, fmt);
 534         dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
 535         va_end(args);
 536         if (IS_ERR(dev))
 537                 return PTR_ERR(dev);
 538
 539         bdi->dev = dev;
 540
 541         /*
 542          * Just start the forker thread for our default backing_dev_info,
 543          * and add other bdi's to the list. They will get a thread created
 544          * on-demand when they need it.
 545          */
 546         if (bdi_cap_flush_forker(bdi)) {
 547                 struct bdi_writeback *wb = &bdi->wb;
 548
 549                 wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
 550                                                 dev_name(dev));
 551                 if (IS_ERR(wb->task))
 552                         return PTR_ERR(wb->task);
 553         }
 554
 555         bdi_debug_register(bdi, dev_name(dev));
 556         set_bit(BDI_registered, &bdi->state);
 557
 558         spin_lock_bh(&bdi_lock);
 559         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
 560         spin_unlock_bh(&bdi_lock);
 561
 562         trace_writeback_bdi_register(bdi);
 563         return 0;
 564 }
 565 EXPORT_SYMBOL(bdi_register);
 566
 567 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
 568 {
 569         return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
 570 }
 571 EXPORT_SYMBOL(bdi_register_dev);
 572
 573 /*
 574  * Remove bdi from the global list and shutdown any threads we have running
 575  */
 576 static void bdi_wb_shutdown(struct backing_dev_info *bdi)
 577 {
 578         if (!bdi_cap_writeback_dirty(bdi))
 579                 return;
 580
 581         /*
 582          * Make sure nobody finds us on the bdi_list anymore
 583          */
 584         bdi_remove_from_list(bdi);
 585
 586         /*
 587          * If setup is pending, wait for that to complete first
 588          */
 589         wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
 590                         TASK_UNINTERRUPTIBLE);
 591
 592         /*
 593          * Finally, kill the kernel thread. We don't need to be RCU
 594          * safe anymore, since the bdi is gone from visibility. Force
 595          * unfreeze of the thread before calling kthread_stop(), otherwise
 596          * it would never exet if it is currently stuck in the refrigerator.
 597          */
 598         if (bdi->wb.task) {
 599                 thaw_process(bdi->wb.task);
 600                 kthread_stop(bdi->wb.task);
 601         }
 602 }
 603
 604 /*
 605  * This bdi is going away now, make sure that no super_blocks point to it
 606  */
 607 static void bdi_prune_sb(struct backing_dev_info *bdi)
 608 {
 609         struct super_block *sb;
 610
 611         spin_lock(&sb_lock);
 612         list_for_each_entry(sb, &super_blocks, s_list) {
 613                 if (sb->s_bdi == bdi)
 614                         sb->s_bdi = &default_backing_dev_info;
 615         }
 616         spin_unlock(&sb_lock);
 617 }
 618
 619 void bdi_unregister(struct backing_dev_info *bdi)
 620 {
 621         if (bdi->dev) {
 622                 bdi_set_min_ratio(bdi, 0);
 623                 trace_writeback_bdi_unregister(bdi);
 624                 bdi_prune_sb(bdi);
 625                 del_timer_sync(&bdi->wb.wakeup_timer);
 626
 627                 if (!bdi_cap_flush_forker(bdi))
 628                         bdi_wb_shutdown(bdi);
 629                 bdi_debug_unregister(bdi);
 630                 device_unregister(bdi->dev);
 631                 bdi->dev = NULL;
 632         }
 633 }
 634 EXPORT_SYMBOL(bdi_unregister);
 635
 636 static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
 637 {
 638         memset(wb, 0, sizeof(*wb));
 639
 640         wb->bdi = bdi;
 641         wb->last_old_flush = jiffies;
 642         INIT_LIST_HEAD(&wb->b_dirty);
 643         INIT_LIST_HEAD(&wb->b_io);
 644         INIT_LIST_HEAD(&wb->b_more_io);
 645         spin_lock_init(&wb->list_lock);
 646         setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
 647 }
 648
 649 /*
 650  * Initial write bandwidth: 100 MB/s
 651  */
 652 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
 653
 654 int bdi_init(struct backing_dev_info *bdi)
 655 {
 656         int i, err;
 657
 658         bdi->dev = NULL;
 659
 660         bdi->min_ratio = 0;
 661         bdi->max_ratio = 100;
 662         bdi->max_prop_frac = PROP_FRAC_BASE;
 663         spin_lock_init(&bdi->wb_lock);
 664         INIT_LIST_HEAD(&bdi->bdi_list);
 665         INIT_LIST_HEAD(&bdi->work_list);
 666
 667         bdi_wb_init(&bdi->wb, bdi);
 668
 669         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
 670                 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
 671                 if (err)
 672                         goto err;
 673         }
 674
 675         bdi->dirty_exceeded = 0;
 676
 677         bdi->bw_time_stamp = jiffies;
 678         bdi->written_stamp = 0;
 679
 680         bdi->write_bandwidth = INIT_BW;
 681         bdi->avg_write_bandwidth = INIT_BW;
 682
 683         err = prop_local_init_percpu(&bdi->completions);
 684
 685         if (err) {
 686 err:
 687                 while (i--)
 688                         percpu_counter_destroy(&bdi->bdi_stat[i]);
 689         }
 690
 691         return err;
 692 }
 693 EXPORT_SYMBOL(bdi_init);
 694
 695 void bdi_destroy(struct backing_dev_info *bdi)
 696 {
 697         int i;
 698
 699         /*
 700          * Splice our entries to the default_backing_dev_info, if this
 701          * bdi disappears
 702          */
 703         if (bdi_has_dirty_io(bdi)) {
 704                 struct bdi_writeback *dst = &default_backing_dev_info.wb;
 705
 706                 bdi_lock_two(&bdi->wb, dst);
 707                 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
 708                 list_splice(&bdi->wb.b_io, &dst->b_io);
 709                 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
 710                 spin_unlock(&bdi->wb.list_lock);
 711                 spin_unlock(&dst->list_lock);
 712         }
 713
 714         bdi_unregister(bdi);
 715
 716         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
 717                 percpu_counter_destroy(&bdi->bdi_stat[i]);
 718
 719         prop_local_destroy_percpu(&bdi->completions);
 720 }
 721 EXPORT_SYMBOL(bdi_destroy);
 722
 723 /*
 724  * For use from filesystems to quickly init and register a bdi associated
 725  * with dirty writeback
 726  */
 727 int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
 728                            unsigned int cap)
 729 {
 730         char tmp[32];
 731         int err;
 732
 733         bdi->name = name;
 734         bdi->capabilities = cap;
 735         err = bdi_init(bdi);
 736         if (err)
 737                 return err;
 738
 739         sprintf(tmp, "%.28s%s", name, "-%d");
 740         err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
 741         if (err) {
 742                 bdi_destroy(bdi);
 743                 return err;
 744         }
 745
 746         return 0;
 747 }
 748 EXPORT_SYMBOL(bdi_setup_and_register);
 749
 750 static wait_queue_head_t congestion_wqh[2] = {
 751                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
 752                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
 753         };
 754 static atomic_t nr_bdi_congested[2];
 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         if (test_and_clear_bit(bit, &bdi->state))
 763                 atomic_dec(&nr_bdi_congested[sync]);
 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         if (!test_and_set_bit(bit, &bdi->state))
 776                 atomic_inc(&nr_bdi_congested[sync]);
 777 }
 778 EXPORT_SYMBOL(set_bdi_congested);
 779
 780 /**
 781  * congestion_wait - wait for a backing_dev to become uncongested
 782  * @sync: SYNC or ASYNC IO
 783  * @timeout: timeout in jiffies
 784  *
 785  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
 786  * write congestion.  If no backing_devs are congested then just wait for the
 787  * next write to be completed.
 788  */
 789 long congestion_wait(int sync, long timeout)
 790 {
 791         long ret;
 792         unsigned long start = jiffies;
 793         DEFINE_WAIT(wait);
 794         wait_queue_head_t *wqh = &congestion_wqh[sync];
 795
 796         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
 797         ret = io_schedule_timeout(timeout);
 798         finish_wait(wqh, &wait);
 799
 800         trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
 801                                         jiffies_to_usecs(jiffies - start));
 802
 803         return ret;
 804 }
 805 EXPORT_SYMBOL(congestion_wait);
 806
 807 /**
 808  * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
 809  * @zone: A zone to check if it is heavily congested
 810  * @sync: SYNC or ASYNC IO
 811  * @timeout: timeout in jiffies
 812  *
 813  * In the event of a congested backing_dev (any backing_dev) and the given
 814  * @zone has experienced recent congestion, this waits for up to @timeout
 815  * jiffies for either a BDI to exit congestion of the given @sync queue
 816  * or a write to complete.
 817  *
 818  * In the absence of zone congestion, cond_resched() is called to yield
 819  * the processor if necessary but otherwise does not sleep.
 820  *
 821  * The return value is 0 if the sleep is for the full timeout. Otherwise,
 822  * it is the number of jiffies that were still remaining when the function
 823  * returned. return_value == timeout implies the function did not sleep.
 824  */
 825 long wait_iff_congested(struct zone *zone, int sync, long timeout)
 826 {
 827         long ret;
 828         unsigned long start = jiffies;
 829         DEFINE_WAIT(wait);
 830         wait_queue_head_t *wqh = &congestion_wqh[sync];
 831
 832         /*
 833          * If there is no congestion, or heavy congestion is not being
 834          * encountered in the current zone, yield if necessary instead
 835          * of sleeping on the congestion queue
 836          */
 837         if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
 838                         !zone_is_reclaim_congested(zone)) {
 839                 cond_resched();
 840
 841                 /* In case we scheduled, work out time remaining */
 842                 ret = timeout - (jiffies - start);
 843                 if (ret < 0)
 844                         ret = 0;
 845
 846                 goto out;
 847         }
 848
 849         /* Sleep until uncongested or a write happens */
 850         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
 851         ret = io_schedule_timeout(timeout);
 852         finish_wait(wqh, &wait);
 853
 854 out:
 855         trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
 856                                         jiffies_to_usecs(jiffies - start));
 857
 858         return ret;
 859 }
 860 EXPORT_SYMBOL(wait_iff_congested);