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                 /*
 405                  * In the following loop we are going to check whether we have
 406                  * some work to do without any synchronization with tasks
 407                  * waking us up to do work for them. So we have to set task
 408                  * state already here so that we don't miss wakeups coming
 409                  * after we verify some condition.
 410                  */
 411                 set_current_state(TASK_INTERRUPTIBLE);
 412
 413                 list_for_each_entry(bdi, &bdi_list, bdi_list) {
 414                         bool have_dirty_io;
 415
 416                         if (!bdi_cap_writeback_dirty(bdi) ||
 417                              bdi_cap_flush_forker(bdi))
 418                                 continue;
 419
 420                         WARN(!test_bit(BDI_registered, &bdi->state),
 421                              "bdi %p/%s is not registered!\n", bdi, bdi->name);
 422
 423                         have_dirty_io = !list_empty(&bdi->work_list) ||
 424                                         wb_has_dirty_io(&bdi->wb);
 425
 426                         /*
 427                          * If the bdi has work to do, but the thread does not
 428                          * exist - create it.
 429                          */
 430                         if (!bdi->wb.task && have_dirty_io) {
 431                                 /*
 432                                  * Set the pending bit - if someone will try to
 433                                  * unregister this bdi - it'll wait on this bit.
 434                                  */
 435                                 set_bit(BDI_pending, &bdi->state);
 436                                 action = FORK_THREAD;
 437                                 break;
 438                         }
 439
 440                         spin_lock(&bdi->wb_lock);
 441
 442                         /*
 443                          * If there is no work to do and the bdi thread was
 444                          * inactive long enough - kill it. The wb_lock is taken
 445                          * to make sure no-one adds more work to this bdi and
 446                          * wakes the bdi thread up.
 447                          */
 448                         if (bdi->wb.task && !have_dirty_io &&
 449                             time_after(jiffies, bdi->wb.last_active +
 450                                                 bdi_longest_inactive())) {
 451                                 task = bdi->wb.task;
 452                                 bdi->wb.task = NULL;
 453                                 spin_unlock(&bdi->wb_lock);
 454                                 set_bit(BDI_pending, &bdi->state);
 455                                 action = KILL_THREAD;
 456                                 break;
 457                         }
 458                         spin_unlock(&bdi->wb_lock);
 459                 }
 460                 spin_unlock_bh(&bdi_lock);
 461
 462                 /* Keep working if default bdi still has things to do */
 463                 if (!list_empty(&me->bdi->work_list))
 464                         __set_current_state(TASK_RUNNING);
 465
 466                 switch (action) {
 467                 case FORK_THREAD:
 468                         __set_current_state(TASK_RUNNING);
 469                         task = kthread_create(bdi_writeback_thread, &bdi->wb,
 470                                               "flush-%s", dev_name(bdi->dev));
 471                         if (IS_ERR(task)) {
 472                                 /*
 473                                  * If thread creation fails, force writeout of
 474                                  * the bdi from the thread. Hopefully 1024 is
 475                                  * large enough for efficient IO.
 476                                  */
 477                                 writeback_inodes_wb(&bdi->wb, 1024);
 478                         } else {
 479                                 /*
 480                                  * The spinlock makes sure we do not lose
 481                                  * wake-ups when racing with 'bdi_queue_work()'.
 482                                  * And as soon as the bdi thread is visible, we
 483                                  * can start it.
 484                                  */
 485                                 spin_lock_bh(&bdi->wb_lock);
 486                                 bdi->wb.task = task;
 487                                 spin_unlock_bh(&bdi->wb_lock);
 488                                 wake_up_process(task);
 489                         }
 490                         bdi_clear_pending(bdi);
 491                         break;
 492
 493                 case KILL_THREAD:
 494                         __set_current_state(TASK_RUNNING);
 495                         kthread_stop(task);
 496                         bdi_clear_pending(bdi);
 497                         break;
 498
 499                 case NO_ACTION:
 500                         if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
 501                                 /*
 502                                  * There are no dirty data. The only thing we
 503                                  * should now care about is checking for
 504                                  * inactive bdi threads and killing them. Thus,
 505                                  * let's sleep for longer time, save energy and
 506                                  * be friendly for battery-driven devices.
 507                                  */
 508                                 schedule_timeout(bdi_longest_inactive());
 509                         else
 510                                 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
 511                         try_to_freeze();
 512                         break;
 513                 }
 514         }
 515
 516         return 0;
 517 }
 518
 519 /*
 520  * Remove bdi from bdi_list, and ensure that it is no longer visible
 521  */
 522 static void bdi_remove_from_list(struct backing_dev_info *bdi)
 523 {
 524         spin_lock_bh(&bdi_lock);
 525         list_del_rcu(&bdi->bdi_list);
 526         spin_unlock_bh(&bdi_lock);
 527
 528         synchronize_rcu_expedited();
 529 }
 530
 531 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 532                 const char *fmt, ...)
 533 {
 534         va_list args;
 535         struct device *dev;
 536
 537         if (bdi->dev)   /* The driver needs to use separate queues per device */
 538                 return 0;
 539
 540         va_start(args, fmt);
 541         dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
 542         va_end(args);
 543         if (IS_ERR(dev))
 544                 return PTR_ERR(dev);
 545
 546         bdi->dev = dev;
 547
 548         /*
 549          * Just start the forker thread for our default backing_dev_info,
 550          * and add other bdi's to the list. They will get a thread created
 551          * on-demand when they need it.
 552          */
 553         if (bdi_cap_flush_forker(bdi)) {
 554                 struct bdi_writeback *wb = &bdi->wb;
 555
 556                 wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
 557                                                 dev_name(dev));
 558                 if (IS_ERR(wb->task))
 559                         return PTR_ERR(wb->task);
 560         }
 561
 562         bdi_debug_register(bdi, dev_name(dev));
 563         set_bit(BDI_registered, &bdi->state);
 564
 565         spin_lock_bh(&bdi_lock);
 566         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
 567         spin_unlock_bh(&bdi_lock);
 568
 569         trace_writeback_bdi_register(bdi);
 570         return 0;
 571 }
 572 EXPORT_SYMBOL(bdi_register);
 573
 574 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
 575 {
 576         return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
 577 }
 578 EXPORT_SYMBOL(bdi_register_dev);
 579
 580 /*
 581  * Remove bdi from the global list and shutdown any threads we have running
 582  */
 583 static void bdi_wb_shutdown(struct backing_dev_info *bdi)
 584 {
 585         if (!bdi_cap_writeback_dirty(bdi))
 586                 return;
 587
 588         /*
 589          * Make sure nobody finds us on the bdi_list anymore
 590          */
 591         bdi_remove_from_list(bdi);
 592
 593         /*
 594          * If setup is pending, wait for that to complete first
 595          */
 596         wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
 597                         TASK_UNINTERRUPTIBLE);
 598
 599         /*
 600          * Finally, kill the kernel thread. We don't need to be RCU
 601          * safe anymore, since the bdi is gone from visibility. Force
 602          * unfreeze of the thread before calling kthread_stop(), otherwise
 603          * it would never exet if it is currently stuck in the refrigerator.
 604          */
 605         if (bdi->wb.task) {
 606                 thaw_process(bdi->wb.task);
 607                 kthread_stop(bdi->wb.task);
 608         }
 609 }
 610
 611 /*
 612  * This bdi is going away now, make sure that no super_blocks point to it
 613  */
 614 static void bdi_prune_sb(struct backing_dev_info *bdi)
 615 {
 616         struct super_block *sb;
 617
 618         spin_lock(&sb_lock);
 619         list_for_each_entry(sb, &super_blocks, s_list) {
 620                 if (sb->s_bdi == bdi)
 621                         sb->s_bdi = &default_backing_dev_info;
 622         }
 623         spin_unlock(&sb_lock);
 624 }
 625
 626 void bdi_unregister(struct backing_dev_info *bdi)
 627 {
 628         if (bdi->dev) {
 629                 bdi_set_min_ratio(bdi, 0);
 630                 trace_writeback_bdi_unregister(bdi);
 631                 bdi_prune_sb(bdi);
 632                 del_timer_sync(&bdi->wb.wakeup_timer);
 633
 634                 if (!bdi_cap_flush_forker(bdi))
 635                         bdi_wb_shutdown(bdi);
 636                 bdi_debug_unregister(bdi);
 637                 device_unregister(bdi->dev);
 638                 bdi->dev = NULL;
 639         }
 640 }
 641 EXPORT_SYMBOL(bdi_unregister);
 642
 643 static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
 644 {
 645         memset(wb, 0, sizeof(*wb));
 646
 647         wb->bdi = bdi;
 648         wb->last_old_flush = jiffies;
 649         INIT_LIST_HEAD(&wb->b_dirty);
 650         INIT_LIST_HEAD(&wb->b_io);
 651         INIT_LIST_HEAD(&wb->b_more_io);
 652         spin_lock_init(&wb->list_lock);
 653         setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
 654 }
 655
 656 /*
 657  * Initial write bandwidth: 100 MB/s
 658  */
 659 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
 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_LIST_HEAD(&bdi->bdi_list);
 672         INIT_LIST_HEAD(&bdi->work_list);
 673
 674         bdi_wb_init(&bdi->wb, bdi);
 675
 676         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
 677                 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
 678                 if (err)
 679                         goto err;
 680         }
 681
 682         bdi->dirty_exceeded = 0;
 683
 684         bdi->bw_time_stamp = jiffies;
 685         bdi->written_stamp = 0;
 686
 687         bdi->write_bandwidth = INIT_BW;
 688         bdi->avg_write_bandwidth = INIT_BW;
 689
 690         err = prop_local_init_percpu(&bdi->completions);
 691
 692         if (err) {
 693 err:
 694                 while (i--)
 695                         percpu_counter_destroy(&bdi->bdi_stat[i]);
 696         }
 697
 698         return err;
 699 }
 700 EXPORT_SYMBOL(bdi_init);
 701
 702 void bdi_destroy(struct backing_dev_info *bdi)
 703 {
 704         int i;
 705
 706         /*
 707          * Splice our entries to the default_backing_dev_info, if this
 708          * bdi disappears
 709          */
 710         if (bdi_has_dirty_io(bdi)) {
 711                 struct bdi_writeback *dst = &default_backing_dev_info.wb;
 712
 713                 bdi_lock_two(&bdi->wb, dst);
 714                 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
 715                 list_splice(&bdi->wb.b_io, &dst->b_io);
 716                 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
 717                 spin_unlock(&bdi->wb.list_lock);
 718                 spin_unlock(&dst->list_lock);
 719         }
 720
 721         bdi_unregister(bdi);
 722
 723         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
 724                 percpu_counter_destroy(&bdi->bdi_stat[i]);
 725
 726         prop_local_destroy_percpu(&bdi->completions);
 727 }
 728 EXPORT_SYMBOL(bdi_destroy);
 729
 730 /*
 731  * For use from filesystems to quickly init and register a bdi associated
 732  * with dirty writeback
 733  */
 734 int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
 735                            unsigned int cap)
 736 {
 737         char tmp[32];
 738         int err;
 739
 740         bdi->name = name;
 741         bdi->capabilities = cap;
 742         err = bdi_init(bdi);
 743         if (err)
 744                 return err;
 745
 746         sprintf(tmp, "%.28s%s", name, "-%d");
 747         err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
 748         if (err) {
 749                 bdi_destroy(bdi);
 750                 return err;
 751         }
 752
 753         return 0;
 754 }
 755 EXPORT_SYMBOL(bdi_setup_and_register);
 756
 757 static wait_queue_head_t congestion_wqh[2] = {
 758                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
 759                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
 760         };
 761 static atomic_t nr_bdi_congested[2];
 762
 763 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
 764 {
 765         enum bdi_state bit;
 766         wait_queue_head_t *wqh = &congestion_wqh[sync];
 767
 768         bit = sync ? BDI_sync_congested : BDI_async_congested;
 769         if (test_and_clear_bit(bit, &bdi->state))
 770                 atomic_dec(&nr_bdi_congested[sync]);
 771         smp_mb__after_clear_bit();
 772         if (waitqueue_active(wqh))
 773                 wake_up(wqh);
 774 }
 775 EXPORT_SYMBOL(clear_bdi_congested);
 776
 777 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
 778 {
 779         enum bdi_state bit;
 780
 781         bit = sync ? BDI_sync_congested : BDI_async_congested;
 782         if (!test_and_set_bit(bit, &bdi->state))
 783                 atomic_inc(&nr_bdi_congested[sync]);
 784 }
 785 EXPORT_SYMBOL(set_bdi_congested);
 786
 787 /**
 788  * congestion_wait - wait for a backing_dev to become uncongested
 789  * @sync: SYNC or ASYNC IO
 790  * @timeout: timeout in jiffies
 791  *
 792  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
 793  * write congestion.  If no backing_devs are congested then just wait for the
 794  * next write to be completed.
 795  */
 796 long congestion_wait(int sync, long timeout)
 797 {
 798         long ret;
 799         unsigned long start = jiffies;
 800         DEFINE_WAIT(wait);
 801         wait_queue_head_t *wqh = &congestion_wqh[sync];
 802
 803         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
 804         ret = io_schedule_timeout(timeout);
 805         finish_wait(wqh, &wait);
 806
 807         trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
 808                                         jiffies_to_usecs(jiffies - start));
 809
 810         return ret;
 811 }
 812 EXPORT_SYMBOL(congestion_wait);
 813
 814 /**
 815  * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
 816  * @zone: A zone to check if it is heavily congested
 817  * @sync: SYNC or ASYNC IO
 818  * @timeout: timeout in jiffies
 819  *
 820  * In the event of a congested backing_dev (any backing_dev) and the given
 821  * @zone has experienced recent congestion, this waits for up to @timeout
 822  * jiffies for either a BDI to exit congestion of the given @sync queue
 823  * or a write to complete.
 824  *
 825  * In the absence of zone congestion, cond_resched() is called to yield
 826  * the processor if necessary but otherwise does not sleep.
 827  *
 828  * The return value is 0 if the sleep is for the full timeout. Otherwise,
 829  * it is the number of jiffies that were still remaining when the function
 830  * returned. return_value == timeout implies the function did not sleep.
 831  */
 832 long wait_iff_congested(struct zone *zone, int sync, long timeout)
 833 {
 834         long ret;
 835         unsigned long start = jiffies;
 836         DEFINE_WAIT(wait);
 837         wait_queue_head_t *wqh = &congestion_wqh[sync];
 838
 839         /*
 840          * If there is no congestion, or heavy congestion is not being
 841          * encountered in the current zone, yield if necessary instead
 842          * of sleeping on the congestion queue
 843          */
 844         if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
 845                         !zone_is_reclaim_congested(zone)) {
 846                 cond_resched();
 847
 848                 /* In case we scheduled, work out time remaining */
 849                 ret = timeout - (jiffies - start);
 850                 if (ret < 0)
 851                         ret = 0;
 852
 853                 goto out;
 854         }
 855
 856         /* Sleep until uncongested or a write happens */
 857         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
 858         ret = io_schedule_timeout(timeout);
 859         finish_wait(wqh, &wait);
 860
 861 out:
 862         trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
 863                                         jiffies_to_usecs(jiffies - start));
 864
 865         return ret;
 866 }
 867 EXPORT_SYMBOL(wait_iff_congested);