writeback: remove unnecessary init_timer call
[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         get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi);
85
86 #define K(x) ((x) << (PAGE_SHIFT - 10))
87         seq_printf(m,
88                    "BdiWriteback:     %8lu kB\n"
89                    "BdiReclaimable:   %8lu kB\n"
90                    "BdiDirtyThresh:   %8lu kB\n"
91                    "DirtyThresh:      %8lu kB\n"
92                    "BackgroundThresh: %8lu kB\n"
93                    "b_dirty:          %8lu\n"
94                    "b_io:             %8lu\n"
95                    "b_more_io:        %8lu\n"
96                    "bdi_list:         %8u\n"
97                    "state:            %8lx\n",
98                    (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
99                    (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
100                    K(bdi_thresh), K(dirty_thresh),
101                    K(background_thresh), nr_dirty, nr_io, nr_more_io,
102                    !list_empty(&bdi->bdi_list), bdi->state);
103 #undef K
104
105         return 0;
106 }
107
108 static int bdi_debug_stats_open(struct inode *inode, struct file *file)
109 {
110         return single_open(file, bdi_debug_stats_show, inode->i_private);
111 }
112
113 static const struct file_operations bdi_debug_stats_fops = {
114         .open           = bdi_debug_stats_open,
115         .read           = seq_read,
116         .llseek         = seq_lseek,
117         .release        = single_release,
118 };
119
120 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
121 {
122         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
123         bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
124                                                bdi, &bdi_debug_stats_fops);
125 }
126
127 static void bdi_debug_unregister(struct backing_dev_info *bdi)
128 {
129         debugfs_remove(bdi->debug_stats);
130         debugfs_remove(bdi->debug_dir);
131 }
132 #else
133 static inline void bdi_debug_init(void)
134 {
135 }
136 static inline void bdi_debug_register(struct backing_dev_info *bdi,
137                                       const char *name)
138 {
139 }
140 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
141 {
142 }
143 #endif
144
145 static ssize_t read_ahead_kb_store(struct device *dev,
146                                   struct device_attribute *attr,
147                                   const char *buf, size_t count)
148 {
149         struct backing_dev_info *bdi = dev_get_drvdata(dev);
150         char *end;
151         unsigned long read_ahead_kb;
152         ssize_t ret = -EINVAL;
153
154         read_ahead_kb = simple_strtoul(buf, &end, 10);
155         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
156                 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
157                 ret = count;
158         }
159         return ret;
160 }
161
162 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
163
164 #define BDI_SHOW(name, expr)                                            \
165 static ssize_t name##_show(struct device *dev,                          \
166                            struct device_attribute *attr, char *page)   \
167 {                                                                       \
168         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
169                                                                         \
170         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
171 }
172
173 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
174
175 static ssize_t min_ratio_store(struct device *dev,
176                 struct device_attribute *attr, const char *buf, size_t count)
177 {
178         struct backing_dev_info *bdi = dev_get_drvdata(dev);
179         char *end;
180         unsigned int ratio;
181         ssize_t ret = -EINVAL;
182
183         ratio = simple_strtoul(buf, &end, 10);
184         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
185                 ret = bdi_set_min_ratio(bdi, ratio);
186                 if (!ret)
187                         ret = count;
188         }
189         return ret;
190 }
191 BDI_SHOW(min_ratio, bdi->min_ratio)
192
193 static ssize_t max_ratio_store(struct device *dev,
194                 struct device_attribute *attr, const char *buf, size_t count)
195 {
196         struct backing_dev_info *bdi = dev_get_drvdata(dev);
197         char *end;
198         unsigned int ratio;
199         ssize_t ret = -EINVAL;
200
201         ratio = simple_strtoul(buf, &end, 10);
202         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
203                 ret = bdi_set_max_ratio(bdi, ratio);
204                 if (!ret)
205                         ret = count;
206         }
207         return ret;
208 }
209 BDI_SHOW(max_ratio, bdi->max_ratio)
210
211 #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
212
213 static struct device_attribute bdi_dev_attrs[] = {
214         __ATTR_RW(read_ahead_kb),
215         __ATTR_RW(min_ratio),
216         __ATTR_RW(max_ratio),
217         __ATTR_NULL,
218 };
219
220 static __init int bdi_class_init(void)
221 {
222         bdi_class = class_create(THIS_MODULE, "bdi");
223         if (IS_ERR(bdi_class))
224                 return PTR_ERR(bdi_class);
225
226         bdi_class->dev_attrs = bdi_dev_attrs;
227         bdi_debug_init();
228         return 0;
229 }
230 postcore_initcall(bdi_class_init);
231
232 static int __init default_bdi_init(void)
233 {
234         int err;
235
236         sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
237         BUG_ON(IS_ERR(sync_supers_tsk));
238
239         setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
240         bdi_arm_supers_timer();
241
242         err = bdi_init(&default_backing_dev_info);
243         if (!err)
244                 bdi_register(&default_backing_dev_info, NULL, "default");
245
246         return err;
247 }
248 subsys_initcall(default_bdi_init);
249
250 int bdi_has_dirty_io(struct backing_dev_info *bdi)
251 {
252         return wb_has_dirty_io(&bdi->wb);
253 }
254
255 static void bdi_flush_io(struct backing_dev_info *bdi)
256 {
257         struct writeback_control wbc = {
258                 .sync_mode              = WB_SYNC_NONE,
259                 .older_than_this        = NULL,
260                 .range_cyclic           = 1,
261                 .nr_to_write            = 1024,
262         };
263
264         writeback_inodes_wb(&bdi->wb, &wbc);
265 }
266
267 /*
268  * kupdated() used to do this. We cannot do it from the bdi_forker_thread()
269  * or we risk deadlocking on ->s_umount. The longer term solution would be
270  * to implement sync_supers_bdi() or similar and simply do it from the
271  * bdi writeback thread individually.
272  */
273 static int bdi_sync_supers(void *unused)
274 {
275         set_user_nice(current, 0);
276
277         while (!kthread_should_stop()) {
278                 set_current_state(TASK_INTERRUPTIBLE);
279                 schedule();
280
281                 /*
282                  * Do this periodically, like kupdated() did before.
283                  */
284                 sync_supers();
285         }
286
287         return 0;
288 }
289
290 void bdi_arm_supers_timer(void)
291 {
292         unsigned long next;
293
294         if (!dirty_writeback_interval)
295                 return;
296
297         next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
298         mod_timer(&sync_supers_timer, round_jiffies_up(next));
299 }
300
301 static void sync_supers_timer_fn(unsigned long unused)
302 {
303         wake_up_process(sync_supers_tsk);
304         bdi_arm_supers_timer();
305 }
306
307 static void wakeup_timer_fn(unsigned long data)
308 {
309         struct backing_dev_info *bdi = (struct backing_dev_info *)data;
310
311         spin_lock_bh(&bdi->wb_lock);
312         if (bdi->wb.task) {
313                 wake_up_process(bdi->wb.task);
314         } else {
315                 /*
316                  * When bdi tasks are inactive for long time, they are killed.
317                  * In this case we have to wake-up the forker thread which
318                  * should create and run the bdi thread.
319                  */
320                 wake_up_process(default_backing_dev_info.wb.task);
321         }
322         spin_unlock_bh(&bdi->wb_lock);
323 }
324
325 /*
326  * This function is used when the first inode for this bdi is marked dirty. It
327  * wakes-up the corresponding bdi thread which should then take care of the
328  * periodic background write-out of dirty inodes. Since the write-out would
329  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
330  * set up a timer which wakes the bdi thread up later.
331  *
332  * Note, we wouldn't bother setting up the timer, but this function is on the
333  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
334  * by delaying the wake-up.
335  */
336 void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
337 {
338         unsigned long timeout;
339
340         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
341         mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout);
342 }
343
344 /*
345  * Calculate the longest interval (jiffies) bdi threads are allowed to be
346  * inactive.
347  */
348 static unsigned long bdi_longest_inactive(void)
349 {
350         unsigned long interval;
351
352         interval = msecs_to_jiffies(dirty_writeback_interval * 10);
353         return max(5UL * 60 * HZ, interval);
354 }
355
356 static int bdi_forker_thread(void *ptr)
357 {
358         struct bdi_writeback *me = ptr;
359
360         current->flags |= PF_FLUSHER | PF_SWAPWRITE;
361         set_freezable();
362
363         /*
364          * Our parent may run at a different priority, just set us to normal
365          */
366         set_user_nice(current, 0);
367
368         for (;;) {
369                 struct task_struct *task = NULL;
370                 struct backing_dev_info *bdi;
371                 enum {
372                         NO_ACTION,   /* Nothing to do */
373                         FORK_THREAD, /* Fork bdi thread */
374                         KILL_THREAD, /* Kill inactive bdi thread */
375                 } action = NO_ACTION;
376
377                 /*
378                  * Temporary measure, we want to make sure we don't see
379                  * dirty data on the default backing_dev_info
380                  */
381                 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
382                         del_timer(&me->wakeup_timer);
383                         wb_do_writeback(me, 0);
384                 }
385
386                 spin_lock_bh(&bdi_lock);
387                 set_current_state(TASK_INTERRUPTIBLE);
388
389                 list_for_each_entry(bdi, &bdi_list, bdi_list) {
390                         bool have_dirty_io;
391
392                         if (!bdi_cap_writeback_dirty(bdi) ||
393                              bdi_cap_flush_forker(bdi))
394                                 continue;
395
396                         WARN(!test_bit(BDI_registered, &bdi->state),
397                              "bdi %p/%s is not registered!\n", bdi, bdi->name);
398
399                         have_dirty_io = !list_empty(&bdi->work_list) ||
400                                         wb_has_dirty_io(&bdi->wb);
401
402                         /*
403                          * If the bdi has work to do, but the thread does not
404                          * exist - create it.
405                          */
406                         if (!bdi->wb.task && have_dirty_io) {
407                                 /*
408                                  * Set the pending bit - if someone will try to
409                                  * unregister this bdi - it'll wait on this bit.
410                                  */
411                                 set_bit(BDI_pending, &bdi->state);
412                                 action = FORK_THREAD;
413                                 break;
414                         }
415
416                         spin_lock_bh(&bdi->wb_lock);
417                         /*
418                          * If there is no work to do and the bdi thread was
419                          * inactive long enough - kill it. The wb_lock is taken
420                          * to make sure no-one adds more work to this bdi and
421                          * wakes the bdi thread up.
422                          */
423                         if (bdi->wb.task && !have_dirty_io &&
424                             time_after(jiffies, bdi->wb.last_active +
425                                                 bdi_longest_inactive())) {
426                                 task = bdi->wb.task;
427                                 bdi->wb.task = NULL;
428                                 spin_unlock(&bdi->wb_lock);
429                                 set_bit(BDI_pending, &bdi->state);
430                                 action = KILL_THREAD;
431                                 break;
432                         }
433                         spin_unlock_bh(&bdi->wb_lock);
434                 }
435                 spin_unlock_bh(&bdi_lock);
436
437                 /* Keep working if default bdi still has things to do */
438                 if (!list_empty(&me->bdi->work_list))
439                         __set_current_state(TASK_RUNNING);
440
441                 switch (action) {
442                 case FORK_THREAD:
443                         __set_current_state(TASK_RUNNING);
444                         task = kthread_run(bdi_writeback_thread, &bdi->wb, "flush-%s",
445                                            dev_name(bdi->dev));
446                         if (IS_ERR(task)) {
447                                 /*
448                                  * If thread creation fails, force writeout of
449                                  * the bdi from the thread.
450                                  */
451                                 bdi_flush_io(bdi);
452                         } else {
453                                 /*
454                                  * The spinlock makes sure we do not lose
455                                  * wake-ups when racing with 'bdi_queue_work()'.
456                                  */
457                                 spin_lock_bh(&bdi->wb_lock);
458                                 bdi->wb.task = task;
459                                 spin_unlock_bh(&bdi->wb_lock);
460                         }
461                         break;
462
463                 case KILL_THREAD:
464                         __set_current_state(TASK_RUNNING);
465                         kthread_stop(task);
466                         break;
467
468                 case NO_ACTION:
469                         if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
470                                 /*
471                                  * There are no dirty data. The only thing we
472                                  * should now care about is checking for
473                                  * inactive bdi threads and killing them. Thus,
474                                  * let's sleep for longer time, save energy and
475                                  * be friendly for battery-driven devices.
476                                  */
477                                 schedule_timeout(bdi_longest_inactive());
478                         else
479                                 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
480                         try_to_freeze();
481                         /* Back to the main loop */
482                         continue;
483                 }
484
485                 /*
486                  * Clear pending bit and wakeup anybody waiting to tear us down.
487                  */
488                 clear_bit(BDI_pending, &bdi->state);
489                 smp_mb__after_clear_bit();
490                 wake_up_bit(&bdi->state, BDI_pending);
491         }
492
493         return 0;
494 }
495
496 /*
497  * Remove bdi from bdi_list, and ensure that it is no longer visible
498  */
499 static void bdi_remove_from_list(struct backing_dev_info *bdi)
500 {
501         spin_lock_bh(&bdi_lock);
502         list_del_rcu(&bdi->bdi_list);
503         spin_unlock_bh(&bdi_lock);
504
505         synchronize_rcu();
506 }
507
508 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
509                 const char *fmt, ...)
510 {
511         va_list args;
512         int ret = 0;
513         struct device *dev;
514
515         if (bdi->dev)   /* The driver needs to use separate queues per device */
516                 goto exit;
517
518         va_start(args, fmt);
519         dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
520         va_end(args);
521         if (IS_ERR(dev)) {
522                 ret = PTR_ERR(dev);
523                 goto exit;
524         }
525
526         spin_lock_bh(&bdi_lock);
527         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
528         spin_unlock_bh(&bdi_lock);
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                         wb->task = NULL;
544                         ret = -ENOMEM;
545
546                         bdi_remove_from_list(bdi);
547                         goto exit;
548                 }
549         }
550
551         bdi_debug_register(bdi, dev_name(dev));
552         set_bit(BDI_registered, &bdi->state);
553         trace_writeback_bdi_register(bdi);
554 exit:
555         return ret;
556 }
557 EXPORT_SYMBOL(bdi_register);
558
559 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
560 {
561         return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
562 }
563 EXPORT_SYMBOL(bdi_register_dev);
564
565 /*
566  * Remove bdi from the global list and shutdown any threads we have running
567  */
568 static void bdi_wb_shutdown(struct backing_dev_info *bdi)
569 {
570         if (!bdi_cap_writeback_dirty(bdi))
571                 return;
572
573         /*
574          * Make sure nobody finds us on the bdi_list anymore
575          */
576         bdi_remove_from_list(bdi);
577
578         /*
579          * If setup is pending, wait for that to complete first
580          */
581         wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
582                         TASK_UNINTERRUPTIBLE);
583
584         /*
585          * Finally, kill the kernel thread. We don't need to be RCU
586          * safe anymore, since the bdi is gone from visibility. Force
587          * unfreeze of the thread before calling kthread_stop(), otherwise
588          * it would never exet if it is currently stuck in the refrigerator.
589          */
590         if (bdi->wb.task) {
591                 thaw_process(bdi->wb.task);
592                 kthread_stop(bdi->wb.task);
593         }
594 }
595
596 /*
597  * This bdi is going away now, make sure that no super_blocks point to it
598  */
599 static void bdi_prune_sb(struct backing_dev_info *bdi)
600 {
601         struct super_block *sb;
602
603         spin_lock(&sb_lock);
604         list_for_each_entry(sb, &super_blocks, s_list) {
605                 if (sb->s_bdi == bdi)
606                         sb->s_bdi = NULL;
607         }
608         spin_unlock(&sb_lock);
609 }
610
611 void bdi_unregister(struct backing_dev_info *bdi)
612 {
613         if (bdi->dev) {
614                 trace_writeback_bdi_unregister(bdi);
615                 bdi_prune_sb(bdi);
616                 del_timer_sync(&bdi->wb.wakeup_timer);
617
618                 if (!bdi_cap_flush_forker(bdi))
619                         bdi_wb_shutdown(bdi);
620                 bdi_debug_unregister(bdi);
621                 device_unregister(bdi->dev);
622                 bdi->dev = NULL;
623         }
624 }
625 EXPORT_SYMBOL(bdi_unregister);
626
627 static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
628 {
629         memset(wb, 0, sizeof(*wb));
630
631         wb->bdi = bdi;
632         wb->last_old_flush = jiffies;
633         INIT_LIST_HEAD(&wb->b_dirty);
634         INIT_LIST_HEAD(&wb->b_io);
635         INIT_LIST_HEAD(&wb->b_more_io);
636         setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
637 }
638
639 int bdi_init(struct backing_dev_info *bdi)
640 {
641         int i, err;
642
643         bdi->dev = NULL;
644
645         bdi->min_ratio = 0;
646         bdi->max_ratio = 100;
647         bdi->max_prop_frac = PROP_FRAC_BASE;
648         spin_lock_init(&bdi->wb_lock);
649         INIT_LIST_HEAD(&bdi->bdi_list);
650         INIT_LIST_HEAD(&bdi->work_list);
651
652         bdi_wb_init(&bdi->wb, bdi);
653
654         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
655                 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
656                 if (err)
657                         goto err;
658         }
659
660         bdi->dirty_exceeded = 0;
661         err = prop_local_init_percpu(&bdi->completions);
662
663         if (err) {
664 err:
665                 while (i--)
666                         percpu_counter_destroy(&bdi->bdi_stat[i]);
667         }
668
669         return err;
670 }
671 EXPORT_SYMBOL(bdi_init);
672
673 void bdi_destroy(struct backing_dev_info *bdi)
674 {
675         int i;
676
677         /*
678          * Splice our entries to the default_backing_dev_info, if this
679          * bdi disappears
680          */
681         if (bdi_has_dirty_io(bdi)) {
682                 struct bdi_writeback *dst = &default_backing_dev_info.wb;
683
684                 spin_lock(&inode_lock);
685                 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
686                 list_splice(&bdi->wb.b_io, &dst->b_io);
687                 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
688                 spin_unlock(&inode_lock);
689         }
690
691         bdi_unregister(bdi);
692
693         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
694                 percpu_counter_destroy(&bdi->bdi_stat[i]);
695
696         prop_local_destroy_percpu(&bdi->completions);
697 }
698 EXPORT_SYMBOL(bdi_destroy);
699
700 /*
701  * For use from filesystems to quickly init and register a bdi associated
702  * with dirty writeback
703  */
704 int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
705                            unsigned int cap)
706 {
707         char tmp[32];
708         int err;
709
710         bdi->name = name;
711         bdi->capabilities = cap;
712         err = bdi_init(bdi);
713         if (err)
714                 return err;
715
716         sprintf(tmp, "%.28s%s", name, "-%d");
717         err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
718         if (err) {
719                 bdi_destroy(bdi);
720                 return err;
721         }
722
723         return 0;
724 }
725 EXPORT_SYMBOL(bdi_setup_and_register);
726
727 static wait_queue_head_t congestion_wqh[2] = {
728                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
729                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
730         };
731
732 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
733 {
734         enum bdi_state bit;
735         wait_queue_head_t *wqh = &congestion_wqh[sync];
736
737         bit = sync ? BDI_sync_congested : BDI_async_congested;
738         clear_bit(bit, &bdi->state);
739         smp_mb__after_clear_bit();
740         if (waitqueue_active(wqh))
741                 wake_up(wqh);
742 }
743 EXPORT_SYMBOL(clear_bdi_congested);
744
745 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
746 {
747         enum bdi_state bit;
748
749         bit = sync ? BDI_sync_congested : BDI_async_congested;
750         set_bit(bit, &bdi->state);
751 }
752 EXPORT_SYMBOL(set_bdi_congested);
753
754 /**
755  * congestion_wait - wait for a backing_dev to become uncongested
756  * @sync: SYNC or ASYNC IO
757  * @timeout: timeout in jiffies
758  *
759  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
760  * write congestion.  If no backing_devs are congested then just wait for the
761  * next write to be completed.
762  */
763 long congestion_wait(int sync, long timeout)
764 {
765         long ret;
766         DEFINE_WAIT(wait);
767         wait_queue_head_t *wqh = &congestion_wqh[sync];
768
769         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
770         ret = io_schedule_timeout(timeout);
771         finish_wait(wqh, &wait);
772         return ret;
773 }
774 EXPORT_SYMBOL(congestion_wait);
775