c2bf86f470ed0044ab7366d5e6ea95a4aea2adf2
[linux-2.6.git] / mm / backing-dev.c
1
2 #include <linux/wait.h>
3 #include <linux/backing-dev.h>
4 #include <linux/kthread.h>
5 #include <linux/freezer.h>
6 #include <linux/fs.h>
7 #include <linux/pagemap.h>
8 #include <linux/mm.h>
9 #include <linux/sched.h>
10 #include <linux/module.h>
11 #include <linux/writeback.h>
12 #include <linux/device.h>
13 #include <trace/events/writeback.h>
14
15 static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
16
17 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
18 {
19 }
20 EXPORT_SYMBOL(default_unplug_io_fn);
21
22 struct backing_dev_info default_backing_dev_info = {
23         .name           = "default",
24         .ra_pages       = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
25         .state          = 0,
26         .capabilities   = BDI_CAP_MAP_COPY,
27         .unplug_io_fn   = default_unplug_io_fn,
28 };
29 EXPORT_SYMBOL_GPL(default_backing_dev_info);
30
31 struct backing_dev_info noop_backing_dev_info = {
32         .name           = "noop",
33 };
34 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
35
36 static struct class *bdi_class;
37
38 /*
39  * bdi_lock protects updates to bdi_list and bdi_pending_list, as well as
40  * reader side protection for bdi_pending_list. bdi_list has RCU reader side
41  * locking.
42  */
43 DEFINE_SPINLOCK(bdi_lock);
44 LIST_HEAD(bdi_list);
45 LIST_HEAD(bdi_pending_list);
46
47 static struct task_struct *sync_supers_tsk;
48 static struct timer_list sync_supers_timer;
49
50 static int bdi_sync_supers(void *);
51 static void sync_supers_timer_fn(unsigned long);
52
53 #ifdef CONFIG_DEBUG_FS
54 #include <linux/debugfs.h>
55 #include <linux/seq_file.h>
56
57 static struct dentry *bdi_debug_root;
58
59 static void bdi_debug_init(void)
60 {
61         bdi_debug_root = debugfs_create_dir("bdi", NULL);
62 }
63
64 static int bdi_debug_stats_show(struct seq_file *m, void *v)
65 {
66         struct backing_dev_info *bdi = m->private;
67         struct bdi_writeback *wb = &bdi->wb;
68         unsigned long background_thresh;
69         unsigned long dirty_thresh;
70         unsigned long bdi_thresh;
71         unsigned long nr_dirty, nr_io, nr_more_io, nr_wb;
72         struct inode *inode;
73
74         nr_wb = nr_dirty = nr_io = nr_more_io = 0;
75         spin_lock(&inode_lock);
76         list_for_each_entry(inode, &wb->b_dirty, i_list)
77                 nr_dirty++;
78         list_for_each_entry(inode, &wb->b_io, i_list)
79                 nr_io++;
80         list_for_each_entry(inode, &wb->b_more_io, i_list)
81                 nr_more_io++;
82         spin_unlock(&inode_lock);
83
84         global_dirty_limits(&background_thresh, &dirty_thresh);
85         bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
86
87 #define K(x) ((x) << (PAGE_SHIFT - 10))
88         seq_printf(m,
89                    "BdiWriteback:     %8lu kB\n"
90                    "BdiReclaimable:   %8lu kB\n"
91                    "BdiDirtyThresh:   %8lu kB\n"
92                    "DirtyThresh:      %8lu kB\n"
93                    "BackgroundThresh: %8lu kB\n"
94                    "b_dirty:          %8lu\n"
95                    "b_io:             %8lu\n"
96                    "b_more_io:        %8lu\n"
97                    "bdi_list:         %8u\n"
98                    "state:            %8lx\n",
99                    (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
100                    (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
101                    K(bdi_thresh), K(dirty_thresh),
102                    K(background_thresh), nr_dirty, nr_io, nr_more_io,
103                    !list_empty(&bdi->bdi_list), bdi->state);
104 #undef K
105
106         return 0;
107 }
108
109 static int bdi_debug_stats_open(struct inode *inode, struct file *file)
110 {
111         return single_open(file, bdi_debug_stats_show, inode->i_private);
112 }
113
114 static const struct file_operations bdi_debug_stats_fops = {
115         .open           = bdi_debug_stats_open,
116         .read           = seq_read,
117         .llseek         = seq_lseek,
118         .release        = single_release,
119 };
120
121 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
122 {
123         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
124         bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
125                                                bdi, &bdi_debug_stats_fops);
126 }
127
128 static void bdi_debug_unregister(struct backing_dev_info *bdi)
129 {
130         debugfs_remove(bdi->debug_stats);
131         debugfs_remove(bdi->debug_dir);
132 }
133 #else
134 static inline void bdi_debug_init(void)
135 {
136 }
137 static inline void bdi_debug_register(struct backing_dev_info *bdi,
138                                       const char *name)
139 {
140 }
141 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
142 {
143 }
144 #endif
145
146 static ssize_t read_ahead_kb_store(struct device *dev,
147                                   struct device_attribute *attr,
148                                   const char *buf, size_t count)
149 {
150         struct backing_dev_info *bdi = dev_get_drvdata(dev);
151         char *end;
152         unsigned long read_ahead_kb;
153         ssize_t ret = -EINVAL;
154
155         read_ahead_kb = simple_strtoul(buf, &end, 10);
156         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
157                 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
158                 ret = count;
159         }
160         return ret;
161 }
162
163 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
164
165 #define BDI_SHOW(name, expr)                                            \
166 static ssize_t name##_show(struct device *dev,                          \
167                            struct device_attribute *attr, char *page)   \
168 {                                                                       \
169         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
170                                                                         \
171         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
172 }
173
174 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
175
176 static ssize_t min_ratio_store(struct device *dev,
177                 struct device_attribute *attr, const char *buf, size_t count)
178 {
179         struct backing_dev_info *bdi = dev_get_drvdata(dev);
180         char *end;
181         unsigned int ratio;
182         ssize_t ret = -EINVAL;
183
184         ratio = simple_strtoul(buf, &end, 10);
185         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
186                 ret = bdi_set_min_ratio(bdi, ratio);
187                 if (!ret)
188                         ret = count;
189         }
190         return ret;
191 }
192 BDI_SHOW(min_ratio, bdi->min_ratio)
193
194 static ssize_t max_ratio_store(struct device *dev,
195                 struct device_attribute *attr, const char *buf, size_t count)
196 {
197         struct backing_dev_info *bdi = dev_get_drvdata(dev);
198         char *end;
199         unsigned int ratio;
200         ssize_t ret = -EINVAL;
201
202         ratio = simple_strtoul(buf, &end, 10);
203         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
204                 ret = bdi_set_max_ratio(bdi, ratio);
205                 if (!ret)
206                         ret = count;
207         }
208         return ret;
209 }
210 BDI_SHOW(max_ratio, bdi->max_ratio)
211
212 #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
213
214 static struct device_attribute bdi_dev_attrs[] = {
215         __ATTR_RW(read_ahead_kb),
216         __ATTR_RW(min_ratio),
217         __ATTR_RW(max_ratio),
218         __ATTR_NULL,
219 };
220
221 static __init int bdi_class_init(void)
222 {
223         bdi_class = class_create(THIS_MODULE, "bdi");
224         if (IS_ERR(bdi_class))
225                 return PTR_ERR(bdi_class);
226
227         bdi_class->dev_attrs = bdi_dev_attrs;
228         bdi_debug_init();
229         return 0;
230 }
231 postcore_initcall(bdi_class_init);
232
233 static int __init default_bdi_init(void)
234 {
235         int err;
236
237         sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
238         BUG_ON(IS_ERR(sync_supers_tsk));
239
240         setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
241         bdi_arm_supers_timer();
242
243         err = bdi_init(&default_backing_dev_info);
244         if (!err)
245                 bdi_register(&default_backing_dev_info, NULL, "default");
246
247         return err;
248 }
249 subsys_initcall(default_bdi_init);
250
251 int bdi_has_dirty_io(struct backing_dev_info *bdi)
252 {
253         return wb_has_dirty_io(&bdi->wb);
254 }
255
256 static void bdi_flush_io(struct backing_dev_info *bdi)
257 {
258         struct writeback_control wbc = {
259                 .sync_mode              = WB_SYNC_NONE,
260                 .older_than_this        = NULL,
261                 .range_cyclic           = 1,
262                 .nr_to_write            = 1024,
263         };
264
265         writeback_inodes_wb(&bdi->wb, &wbc);
266 }
267
268 /*
269  * kupdated() used to do this. We cannot do it from the bdi_forker_thread()
270  * or we risk deadlocking on ->s_umount. The longer term solution would be
271  * to implement sync_supers_bdi() or similar and simply do it from the
272  * bdi writeback thread individually.
273  */
274 static int bdi_sync_supers(void *unused)
275 {
276         set_user_nice(current, 0);
277
278         while (!kthread_should_stop()) {
279                 set_current_state(TASK_INTERRUPTIBLE);
280                 schedule();
281
282                 /*
283                  * Do this periodically, like kupdated() did before.
284                  */
285                 sync_supers();
286         }
287
288         return 0;
289 }
290
291 void bdi_arm_supers_timer(void)
292 {
293         unsigned long next;
294
295         if (!dirty_writeback_interval)
296                 return;
297
298         next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
299         mod_timer(&sync_supers_timer, round_jiffies_up(next));
300 }
301
302 static void sync_supers_timer_fn(unsigned long unused)
303 {
304         wake_up_process(sync_supers_tsk);
305         bdi_arm_supers_timer();
306 }
307
308 static void wakeup_timer_fn(unsigned long data)
309 {
310         struct backing_dev_info *bdi = (struct backing_dev_info *)data;
311
312         spin_lock_bh(&bdi->wb_lock);
313         if (bdi->wb.task) {
314                 trace_writeback_wake_thread(bdi);
315                 wake_up_process(bdi->wb.task);
316         } else {
317                 /*
318                  * When bdi tasks are inactive for long time, they are killed.
319                  * In this case we have to wake-up the forker thread which
320                  * should create and run the bdi thread.
321                  */
322                 trace_writeback_wake_forker_thread(bdi);
323                 wake_up_process(default_backing_dev_info.wb.task);
324         }
325         spin_unlock_bh(&bdi->wb_lock);
326 }
327
328 /*
329  * This function is used when the first inode for this bdi is marked dirty. It
330  * wakes-up the corresponding bdi thread which should then take care of the
331  * periodic background write-out of dirty inodes. Since the write-out would
332  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
333  * set up a timer which wakes the bdi thread up later.
334  *
335  * Note, we wouldn't bother setting up the timer, but this function is on the
336  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
337  * by delaying the wake-up.
338  */
339 void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
340 {
341         unsigned long timeout;
342
343         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
344         mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout);
345 }
346
347 /*
348  * Calculate the longest interval (jiffies) bdi threads are allowed to be
349  * inactive.
350  */
351 static unsigned long bdi_longest_inactive(void)
352 {
353         unsigned long interval;
354
355         interval = msecs_to_jiffies(dirty_writeback_interval * 10);
356         return max(5UL * 60 * HZ, interval);
357 }
358
359 static int bdi_forker_thread(void *ptr)
360 {
361         struct bdi_writeback *me = ptr;
362
363         current->flags |= PF_FLUSHER | PF_SWAPWRITE;
364         set_freezable();
365
366         /*
367          * Our parent may run at a different priority, just set us to normal
368          */
369         set_user_nice(current, 0);
370
371         for (;;) {
372                 struct task_struct *task = NULL;
373                 struct backing_dev_info *bdi;
374                 enum {
375                         NO_ACTION,   /* Nothing to do */
376                         FORK_THREAD, /* Fork bdi thread */
377                         KILL_THREAD, /* Kill inactive bdi thread */
378                 } action = NO_ACTION;
379
380                 /*
381                  * Temporary measure, we want to make sure we don't see
382                  * dirty data on the default backing_dev_info
383                  */
384                 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
385                         del_timer(&me->wakeup_timer);
386                         wb_do_writeback(me, 0);
387                 }
388
389                 spin_lock_bh(&bdi_lock);
390                 set_current_state(TASK_INTERRUPTIBLE);
391
392                 list_for_each_entry(bdi, &bdi_list, bdi_list) {
393                         bool have_dirty_io;
394
395                         if (!bdi_cap_writeback_dirty(bdi) ||
396                              bdi_cap_flush_forker(bdi))
397                                 continue;
398
399                         WARN(!test_bit(BDI_registered, &bdi->state),
400                              "bdi %p/%s is not registered!\n", bdi, bdi->name);
401
402                         have_dirty_io = !list_empty(&bdi->work_list) ||
403                                         wb_has_dirty_io(&bdi->wb);
404
405                         /*
406                          * If the bdi has work to do, but the thread does not
407                          * exist - create it.
408                          */
409                         if (!bdi->wb.task && have_dirty_io) {
410                                 /*
411                                  * Set the pending bit - if someone will try to
412                                  * unregister this bdi - it'll wait on this bit.
413                                  */
414                                 set_bit(BDI_pending, &bdi->state);
415                                 action = FORK_THREAD;
416                                 break;
417                         }
418
419                         spin_lock(&bdi->wb_lock);
420
421                         /*
422                          * If there is no work to do and the bdi thread was
423                          * inactive long enough - kill it. The wb_lock is taken
424                          * to make sure no-one adds more work to this bdi and
425                          * wakes the bdi thread up.
426                          */
427                         if (bdi->wb.task && !have_dirty_io &&
428                             time_after(jiffies, bdi->wb.last_active +
429                                                 bdi_longest_inactive())) {
430                                 task = bdi->wb.task;
431                                 bdi->wb.task = NULL;
432                                 spin_unlock(&bdi->wb_lock);
433                                 set_bit(BDI_pending, &bdi->state);
434                                 action = KILL_THREAD;
435                                 break;
436                         }
437                         spin_unlock(&bdi->wb_lock);
438                 }
439                 spin_unlock_bh(&bdi_lock);
440
441                 /* Keep working if default bdi still has things to do */
442                 if (!list_empty(&me->bdi->work_list))
443                         __set_current_state(TASK_RUNNING);
444
445                 switch (action) {
446                 case FORK_THREAD:
447                         __set_current_state(TASK_RUNNING);
448                         task = kthread_create(bdi_writeback_thread, &bdi->wb,
449                                               "flush-%s", dev_name(bdi->dev));
450                         if (IS_ERR(task)) {
451                                 /*
452                                  * If thread creation fails, force writeout of
453                                  * the bdi from the thread.
454                                  */
455                                 bdi_flush_io(bdi);
456                         } else {
457                                 /*
458                                  * The spinlock makes sure we do not lose
459                                  * wake-ups when racing with 'bdi_queue_work()'.
460                                  * And as soon as the bdi thread is visible, we
461                                  * can start it.
462                                  */
463                                 spin_lock_bh(&bdi->wb_lock);
464                                 bdi->wb.task = task;
465                                 spin_unlock_bh(&bdi->wb_lock);
466                                 wake_up_process(task);
467                         }
468                         break;
469
470                 case KILL_THREAD:
471                         __set_current_state(TASK_RUNNING);
472                         kthread_stop(task);
473                         break;
474
475                 case NO_ACTION:
476                         if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
477                                 /*
478                                  * There are no dirty data. The only thing we
479                                  * should now care about is checking for
480                                  * inactive bdi threads and killing them. Thus,
481                                  * let's sleep for longer time, save energy and
482                                  * be friendly for battery-driven devices.
483                                  */
484                                 schedule_timeout(bdi_longest_inactive());
485                         else
486                                 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
487                         try_to_freeze();
488                         /* Back to the main loop */
489                         continue;
490                 }
491
492                 /*
493                  * Clear pending bit and wakeup anybody waiting to tear us down.
494                  */
495                 clear_bit(BDI_pending, &bdi->state);
496                 smp_mb__after_clear_bit();
497                 wake_up_bit(&bdi->state, BDI_pending);
498         }
499
500         return 0;
501 }
502
503 /*
504  * Remove bdi from bdi_list, and ensure that it is no longer visible
505  */
506 static void bdi_remove_from_list(struct backing_dev_info *bdi)
507 {
508         spin_lock_bh(&bdi_lock);
509         list_del_rcu(&bdi->bdi_list);
510         spin_unlock_bh(&bdi_lock);
511
512         synchronize_rcu();
513 }
514
515 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
516                 const char *fmt, ...)
517 {
518         va_list args;
519         struct device *dev;
520
521         if (bdi->dev)   /* The driver needs to use separate queues per device */
522                 return 0;
523
524         va_start(args, fmt);
525         dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
526         va_end(args);
527         if (IS_ERR(dev))
528                 return PTR_ERR(dev);
529
530         bdi->dev = dev;
531
532         /*
533          * Just start the forker thread for our default backing_dev_info,
534          * and add other bdi's to the list. They will get a thread created
535          * on-demand when they need it.
536          */
537         if (bdi_cap_flush_forker(bdi)) {
538                 struct bdi_writeback *wb = &bdi->wb;
539
540                 wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
541                                                 dev_name(dev));
542                 if (IS_ERR(wb->task))
543                         return PTR_ERR(wb->task);
544         }
545
546         bdi_debug_register(bdi, dev_name(dev));
547         set_bit(BDI_registered, &bdi->state);
548
549         spin_lock_bh(&bdi_lock);
550         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
551         spin_unlock_bh(&bdi_lock);
552
553         trace_writeback_bdi_register(bdi);
554         return 0;
555 }
556 EXPORT_SYMBOL(bdi_register);
557
558 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
559 {
560         return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
561 }
562 EXPORT_SYMBOL(bdi_register_dev);
563
564 /*
565  * Remove bdi from the global list and shutdown any threads we have running
566  */
567 static void bdi_wb_shutdown(struct backing_dev_info *bdi)
568 {
569         if (!bdi_cap_writeback_dirty(bdi))
570                 return;
571
572         /*
573          * Make sure nobody finds us on the bdi_list anymore
574          */
575         bdi_remove_from_list(bdi);
576
577         /*
578          * If setup is pending, wait for that to complete first
579          */
580         wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
581                         TASK_UNINTERRUPTIBLE);
582
583         /*
584          * Finally, kill the kernel thread. We don't need to be RCU
585          * safe anymore, since the bdi is gone from visibility. Force
586          * unfreeze of the thread before calling kthread_stop(), otherwise
587          * it would never exet if it is currently stuck in the refrigerator.
588          */
589         if (bdi->wb.task) {
590                 thaw_process(bdi->wb.task);
591                 kthread_stop(bdi->wb.task);
592         }
593 }
594
595 /*
596  * This bdi is going away now, make sure that no super_blocks point to it
597  */
598 static void bdi_prune_sb(struct backing_dev_info *bdi)
599 {
600         struct super_block *sb;
601
602         spin_lock(&sb_lock);
603         list_for_each_entry(sb, &super_blocks, s_list) {
604                 if (sb->s_bdi == bdi)
605                         sb->s_bdi = NULL;
606         }
607         spin_unlock(&sb_lock);
608 }
609
610 void bdi_unregister(struct backing_dev_info *bdi)
611 {
612         if (bdi->dev) {
613                 trace_writeback_bdi_unregister(bdi);
614                 bdi_prune_sb(bdi);
615                 del_timer_sync(&bdi->wb.wakeup_timer);
616
617                 if (!bdi_cap_flush_forker(bdi))
618                         bdi_wb_shutdown(bdi);
619                 bdi_debug_unregister(bdi);
620                 device_unregister(bdi->dev);
621                 bdi->dev = NULL;
622         }
623 }
624 EXPORT_SYMBOL(bdi_unregister);
625
626 static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
627 {
628         memset(wb, 0, sizeof(*wb));
629
630         wb->bdi = bdi;
631         wb->last_old_flush = jiffies;
632         INIT_LIST_HEAD(&wb->b_dirty);
633         INIT_LIST_HEAD(&wb->b_io);
634         INIT_LIST_HEAD(&wb->b_more_io);
635         setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
636 }
637
638 int bdi_init(struct backing_dev_info *bdi)
639 {
640         int i, err;
641
642         bdi->dev = NULL;
643
644         bdi->min_ratio = 0;
645         bdi->max_ratio = 100;
646         bdi->max_prop_frac = PROP_FRAC_BASE;
647         spin_lock_init(&bdi->wb_lock);
648         INIT_LIST_HEAD(&bdi->bdi_list);
649         INIT_LIST_HEAD(&bdi->work_list);
650
651         bdi_wb_init(&bdi->wb, bdi);
652
653         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
654                 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
655                 if (err)
656                         goto err;
657         }
658
659         bdi->dirty_exceeded = 0;
660         err = prop_local_init_percpu(&bdi->completions);
661
662         if (err) {
663 err:
664                 while (i--)
665                         percpu_counter_destroy(&bdi->bdi_stat[i]);
666         }
667
668         return err;
669 }
670 EXPORT_SYMBOL(bdi_init);
671
672 void bdi_destroy(struct backing_dev_info *bdi)
673 {
674         int i;
675
676         /*
677          * Splice our entries to the default_backing_dev_info, if this
678          * bdi disappears
679          */
680         if (bdi_has_dirty_io(bdi)) {
681                 struct bdi_writeback *dst = &default_backing_dev_info.wb;
682
683                 spin_lock(&inode_lock);
684                 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
685                 list_splice(&bdi->wb.b_io, &dst->b_io);
686                 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
687                 spin_unlock(&inode_lock);
688         }
689
690         bdi_unregister(bdi);
691
692         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
693                 percpu_counter_destroy(&bdi->bdi_stat[i]);
694
695         prop_local_destroy_percpu(&bdi->completions);
696 }
697 EXPORT_SYMBOL(bdi_destroy);
698
699 /*
700  * For use from filesystems to quickly init and register a bdi associated
701  * with dirty writeback
702  */
703 int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
704                            unsigned int cap)
705 {
706         char tmp[32];
707         int err;
708
709         bdi->name = name;
710         bdi->capabilities = cap;
711         err = bdi_init(bdi);
712         if (err)
713                 return err;
714
715         sprintf(tmp, "%.28s%s", name, "-%d");
716         err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
717         if (err) {
718                 bdi_destroy(bdi);
719                 return err;
720         }
721
722         return 0;
723 }
724 EXPORT_SYMBOL(bdi_setup_and_register);
725
726 static wait_queue_head_t congestion_wqh[2] = {
727                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
728                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
729         };
730
731 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
732 {
733         enum bdi_state bit;
734         wait_queue_head_t *wqh = &congestion_wqh[sync];
735
736         bit = sync ? BDI_sync_congested : BDI_async_congested;
737         clear_bit(bit, &bdi->state);
738         smp_mb__after_clear_bit();
739         if (waitqueue_active(wqh))
740                 wake_up(wqh);
741 }
742 EXPORT_SYMBOL(clear_bdi_congested);
743
744 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
745 {
746         enum bdi_state bit;
747
748         bit = sync ? BDI_sync_congested : BDI_async_congested;
749         set_bit(bit, &bdi->state);
750 }
751 EXPORT_SYMBOL(set_bdi_congested);
752
753 /**
754  * congestion_wait - wait for a backing_dev to become uncongested
755  * @sync: SYNC or ASYNC IO
756  * @timeout: timeout in jiffies
757  *
758  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
759  * write congestion.  If no backing_devs are congested then just wait for the
760  * next write to be completed.
761  */
762 long congestion_wait(int sync, long timeout)
763 {
764         long ret;
765         DEFINE_WAIT(wait);
766         wait_queue_head_t *wqh = &congestion_wqh[sync];
767
768         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
769         ret = io_schedule_timeout(timeout);
770         finish_wait(wqh, &wait);
771         return ret;
772 }
773 EXPORT_SYMBOL(congestion_wait);
774