4b3e9f17ee21850c58d0319e5852b4630160db99
[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         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
34 };
35 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
36
37 static struct class *bdi_class;
38
39 /*
40  * bdi_lock protects updates to bdi_list and bdi_pending_list, as well as
41  * reader side protection for bdi_pending_list. bdi_list has RCU reader side
42  * locking.
43  */
44 DEFINE_SPINLOCK(bdi_lock);
45 LIST_HEAD(bdi_list);
46 LIST_HEAD(bdi_pending_list);
47
48 static struct task_struct *sync_supers_tsk;
49 static struct timer_list sync_supers_timer;
50
51 static int bdi_sync_supers(void *);
52 static void sync_supers_timer_fn(unsigned long);
53
54 #ifdef CONFIG_DEBUG_FS
55 #include <linux/debugfs.h>
56 #include <linux/seq_file.h>
57
58 static struct dentry *bdi_debug_root;
59
60 static void bdi_debug_init(void)
61 {
62         bdi_debug_root = debugfs_create_dir("bdi", NULL);
63 }
64
65 static int bdi_debug_stats_show(struct seq_file *m, void *v)
66 {
67         struct backing_dev_info *bdi = m->private;
68         struct bdi_writeback *wb = &bdi->wb;
69         unsigned long background_thresh;
70         unsigned long dirty_thresh;
71         unsigned long bdi_thresh;
72         unsigned long nr_dirty, nr_io, nr_more_io, nr_wb;
73         struct inode *inode;
74
75         nr_wb = nr_dirty = nr_io = nr_more_io = 0;
76         spin_lock(&inode_wb_list_lock);
77         list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
78                 nr_dirty++;
79         list_for_each_entry(inode, &wb->b_io, i_wb_list)
80                 nr_io++;
81         list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
82                 nr_more_io++;
83         spin_unlock(&inode_wb_list_lock);
84
85         global_dirty_limits(&background_thresh, &dirty_thresh);
86         bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
87
88 #define K(x) ((x) << (PAGE_SHIFT - 10))
89         seq_printf(m,
90                    "BdiWriteback:     %8lu kB\n"
91                    "BdiReclaimable:   %8lu kB\n"
92                    "BdiDirtyThresh:   %8lu kB\n"
93                    "DirtyThresh:      %8lu kB\n"
94                    "BackgroundThresh: %8lu kB\n"
95                    "b_dirty:          %8lu\n"
96                    "b_io:             %8lu\n"
97                    "b_more_io:        %8lu\n"
98                    "bdi_list:         %8u\n"
99                    "state:            %8lx\n",
100                    (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
101                    (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
102                    K(bdi_thresh), K(dirty_thresh),
103                    K(background_thresh), nr_dirty, nr_io, nr_more_io,
104                    !list_empty(&bdi->bdi_list), bdi->state);
105 #undef K
106
107         return 0;
108 }
109
110 static int bdi_debug_stats_open(struct inode *inode, struct file *file)
111 {
112         return single_open(file, bdi_debug_stats_show, inode->i_private);
113 }
114
115 static const struct file_operations bdi_debug_stats_fops = {
116         .open           = bdi_debug_stats_open,
117         .read           = seq_read,
118         .llseek         = seq_lseek,
119         .release        = single_release,
120 };
121
122 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
123 {
124         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
125         bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
126                                                bdi, &bdi_debug_stats_fops);
127 }
128
129 static void bdi_debug_unregister(struct backing_dev_info *bdi)
130 {
131         debugfs_remove(bdi->debug_stats);
132         debugfs_remove(bdi->debug_dir);
133 }
134 #else
135 static inline void bdi_debug_init(void)
136 {
137 }
138 static inline void bdi_debug_register(struct backing_dev_info *bdi,
139                                       const char *name)
140 {
141 }
142 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
143 {
144 }
145 #endif
146
147 static ssize_t read_ahead_kb_store(struct device *dev,
148                                   struct device_attribute *attr,
149                                   const char *buf, size_t count)
150 {
151         struct backing_dev_info *bdi = dev_get_drvdata(dev);
152         char *end;
153         unsigned long read_ahead_kb;
154         ssize_t ret = -EINVAL;
155
156         read_ahead_kb = simple_strtoul(buf, &end, 10);
157         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
158                 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
159                 ret = count;
160         }
161         return ret;
162 }
163
164 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
165
166 #define BDI_SHOW(name, expr)                                            \
167 static ssize_t name##_show(struct device *dev,                          \
168                            struct device_attribute *attr, char *page)   \
169 {                                                                       \
170         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
171                                                                         \
172         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
173 }
174
175 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
176
177 static ssize_t min_ratio_store(struct device *dev,
178                 struct device_attribute *attr, const char *buf, size_t count)
179 {
180         struct backing_dev_info *bdi = dev_get_drvdata(dev);
181         char *end;
182         unsigned int ratio;
183         ssize_t ret = -EINVAL;
184
185         ratio = simple_strtoul(buf, &end, 10);
186         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
187                 ret = bdi_set_min_ratio(bdi, ratio);
188                 if (!ret)
189                         ret = count;
190         }
191         return ret;
192 }
193 BDI_SHOW(min_ratio, bdi->min_ratio)
194
195 static ssize_t max_ratio_store(struct device *dev,
196                 struct device_attribute *attr, const char *buf, size_t count)
197 {
198         struct backing_dev_info *bdi = dev_get_drvdata(dev);
199         char *end;
200         unsigned int ratio;
201         ssize_t ret = -EINVAL;
202
203         ratio = simple_strtoul(buf, &end, 10);
204         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
205                 ret = bdi_set_max_ratio(bdi, ratio);
206                 if (!ret)
207                         ret = count;
208         }
209         return ret;
210 }
211 BDI_SHOW(max_ratio, bdi->max_ratio)
212
213 #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
214
215 static struct device_attribute bdi_dev_attrs[] = {
216         __ATTR_RW(read_ahead_kb),
217         __ATTR_RW(min_ratio),
218         __ATTR_RW(max_ratio),
219         __ATTR_NULL,
220 };
221
222 static __init int bdi_class_init(void)
223 {
224         bdi_class = class_create(THIS_MODULE, "bdi");
225         if (IS_ERR(bdi_class))
226                 return PTR_ERR(bdi_class);
227
228         bdi_class->dev_attrs = bdi_dev_attrs;
229         bdi_debug_init();
230         return 0;
231 }
232 postcore_initcall(bdi_class_init);
233
234 static int __init default_bdi_init(void)
235 {
236         int err;
237
238         sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
239         BUG_ON(IS_ERR(sync_supers_tsk));
240
241         setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
242         bdi_arm_supers_timer();
243
244         err = bdi_init(&default_backing_dev_info);
245         if (!err)
246                 bdi_register(&default_backing_dev_info, NULL, "default");
247         err = bdi_init(&noop_backing_dev_info);
248
249         return err;
250 }
251 subsys_initcall(default_bdi_init);
252
253 int bdi_has_dirty_io(struct backing_dev_info *bdi)
254 {
255         return wb_has_dirty_io(&bdi->wb);
256 }
257
258 static void bdi_flush_io(struct backing_dev_info *bdi)
259 {
260         struct writeback_control wbc = {
261                 .sync_mode              = WB_SYNC_NONE,
262                 .older_than_this        = NULL,
263                 .range_cyclic           = 1,
264                 .nr_to_write            = 1024,
265         };
266
267         writeback_inodes_wb(&bdi->wb, &wbc);
268 }
269
270 /*
271  * kupdated() used to do this. We cannot do it from the bdi_forker_thread()
272  * or we risk deadlocking on ->s_umount. The longer term solution would be
273  * to implement sync_supers_bdi() or similar and simply do it from the
274  * bdi writeback thread individually.
275  */
276 static int bdi_sync_supers(void *unused)
277 {
278         set_user_nice(current, 0);
279
280         while (!kthread_should_stop()) {
281                 set_current_state(TASK_INTERRUPTIBLE);
282                 schedule();
283
284                 /*
285                  * Do this periodically, like kupdated() did before.
286                  */
287                 sync_supers();
288         }
289
290         return 0;
291 }
292
293 void bdi_arm_supers_timer(void)
294 {
295         unsigned long next;
296
297         if (!dirty_writeback_interval)
298                 return;
299
300         next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
301         mod_timer(&sync_supers_timer, round_jiffies_up(next));
302 }
303
304 static void sync_supers_timer_fn(unsigned long unused)
305 {
306         wake_up_process(sync_supers_tsk);
307         bdi_arm_supers_timer();
308 }
309
310 static void wakeup_timer_fn(unsigned long data)
311 {
312         struct backing_dev_info *bdi = (struct backing_dev_info *)data;
313
314         spin_lock_bh(&bdi->wb_lock);
315         if (bdi->wb.task) {
316                 trace_writeback_wake_thread(bdi);
317                 wake_up_process(bdi->wb.task);
318         } else {
319                 /*
320                  * When bdi tasks are inactive for long time, they are killed.
321                  * In this case we have to wake-up the forker thread which
322                  * should create and run the bdi thread.
323                  */
324                 trace_writeback_wake_forker_thread(bdi);
325                 wake_up_process(default_backing_dev_info.wb.task);
326         }
327         spin_unlock_bh(&bdi->wb_lock);
328 }
329
330 /*
331  * This function is used when the first inode for this bdi is marked dirty. It
332  * wakes-up the corresponding bdi thread which should then take care of the
333  * periodic background write-out of dirty inodes. Since the write-out would
334  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
335  * set up a timer which wakes the bdi thread up later.
336  *
337  * Note, we wouldn't bother setting up the timer, but this function is on the
338  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
339  * by delaying the wake-up.
340  */
341 void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
342 {
343         unsigned long timeout;
344
345         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
346         mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout);
347 }
348
349 /*
350  * Calculate the longest interval (jiffies) bdi threads are allowed to be
351  * inactive.
352  */
353 static unsigned long bdi_longest_inactive(void)
354 {
355         unsigned long interval;
356
357         interval = msecs_to_jiffies(dirty_writeback_interval * 10);
358         return max(5UL * 60 * HZ, interval);
359 }
360
361 static int bdi_forker_thread(void *ptr)
362 {
363         struct bdi_writeback *me = ptr;
364
365         current->flags |= PF_SWAPWRITE;
366         set_freezable();
367
368         /*
369          * Our parent may run at a different priority, just set us to normal
370          */
371         set_user_nice(current, 0);
372
373         for (;;) {
374                 struct task_struct *task = NULL;
375                 struct backing_dev_info *bdi;
376                 enum {
377                         NO_ACTION,   /* Nothing to do */
378                         FORK_THREAD, /* Fork bdi thread */
379                         KILL_THREAD, /* Kill inactive bdi thread */
380                 } action = NO_ACTION;
381
382                 /*
383                  * Temporary measure, we want to make sure we don't see
384                  * dirty data on the default backing_dev_info
385                  */
386                 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
387                         del_timer(&me->wakeup_timer);
388                         wb_do_writeback(me, 0);
389                 }
390
391                 spin_lock_bh(&bdi_lock);
392                 set_current_state(TASK_INTERRUPTIBLE);
393
394                 list_for_each_entry(bdi, &bdi_list, bdi_list) {
395                         bool have_dirty_io;
396
397                         if (!bdi_cap_writeback_dirty(bdi) ||
398                              bdi_cap_flush_forker(bdi))
399                                 continue;
400
401                         WARN(!test_bit(BDI_registered, &bdi->state),
402                              "bdi %p/%s is not registered!\n", bdi, bdi->name);
403
404                         have_dirty_io = !list_empty(&bdi->work_list) ||
405                                         wb_has_dirty_io(&bdi->wb);
406
407                         /*
408                          * If the bdi has work to do, but the thread does not
409                          * exist - create it.
410                          */
411                         if (!bdi->wb.task && have_dirty_io) {
412                                 /*
413                                  * Set the pending bit - if someone will try to
414                                  * unregister this bdi - it'll wait on this bit.
415                                  */
416                                 set_bit(BDI_pending, &bdi->state);
417                                 action = FORK_THREAD;
418                                 break;
419                         }
420
421                         spin_lock(&bdi->wb_lock);
422
423                         /*
424                          * If there is no work to do and the bdi thread was
425                          * inactive long enough - kill it. The wb_lock is taken
426                          * to make sure no-one adds more work to this bdi and
427                          * wakes the bdi thread up.
428                          */
429                         if (bdi->wb.task && !have_dirty_io &&
430                             time_after(jiffies, bdi->wb.last_active +
431                                                 bdi_longest_inactive())) {
432                                 task = bdi->wb.task;
433                                 bdi->wb.task = NULL;
434                                 spin_unlock(&bdi->wb_lock);
435                                 set_bit(BDI_pending, &bdi->state);
436                                 action = KILL_THREAD;
437                                 break;
438                         }
439                         spin_unlock(&bdi->wb_lock);
440                 }
441                 spin_unlock_bh(&bdi_lock);
442
443                 /* Keep working if default bdi still has things to do */
444                 if (!list_empty(&me->bdi->work_list))
445                         __set_current_state(TASK_RUNNING);
446
447                 switch (action) {
448                 case FORK_THREAD:
449                         __set_current_state(TASK_RUNNING);
450                         task = kthread_create(bdi_writeback_thread, &bdi->wb,
451                                               "flush-%s", dev_name(bdi->dev));
452                         if (IS_ERR(task)) {
453                                 /*
454                                  * If thread creation fails, force writeout of
455                                  * the bdi from the thread.
456                                  */
457                                 bdi_flush_io(bdi);
458                         } else {
459                                 /*
460                                  * The spinlock makes sure we do not lose
461                                  * wake-ups when racing with 'bdi_queue_work()'.
462                                  * And as soon as the bdi thread is visible, we
463                                  * can start it.
464                                  */
465                                 spin_lock_bh(&bdi->wb_lock);
466                                 bdi->wb.task = task;
467                                 spin_unlock_bh(&bdi->wb_lock);
468                                 wake_up_process(task);
469                         }
470                         break;
471
472                 case KILL_THREAD:
473                         __set_current_state(TASK_RUNNING);
474                         kthread_stop(task);
475                         break;
476
477                 case NO_ACTION:
478                         if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
479                                 /*
480                                  * There are no dirty data. The only thing we
481                                  * should now care about is checking for
482                                  * inactive bdi threads and killing them. Thus,
483                                  * let's sleep for longer time, save energy and
484                                  * be friendly for battery-driven devices.
485                                  */
486                                 schedule_timeout(bdi_longest_inactive());
487                         else
488                                 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
489                         try_to_freeze();
490                         /* Back to the main loop */
491                         continue;
492                 }
493
494                 /*
495                  * Clear pending bit and wakeup anybody waiting to tear us down.
496                  */
497                 clear_bit(BDI_pending, &bdi->state);
498                 smp_mb__after_clear_bit();
499                 wake_up_bit(&bdi->state, BDI_pending);
500         }
501
502         return 0;
503 }
504
505 /*
506  * Remove bdi from bdi_list, and ensure that it is no longer visible
507  */
508 static void bdi_remove_from_list(struct backing_dev_info *bdi)
509 {
510         spin_lock_bh(&bdi_lock);
511         list_del_rcu(&bdi->bdi_list);
512         spin_unlock_bh(&bdi_lock);
513
514         synchronize_rcu();
515 }
516
517 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
518                 const char *fmt, ...)
519 {
520         va_list args;
521         struct device *dev;
522
523         if (bdi->dev)   /* The driver needs to use separate queues per device */
524                 return 0;
525
526         va_start(args, fmt);
527         dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
528         va_end(args);
529         if (IS_ERR(dev))
530                 return PTR_ERR(dev);
531
532         bdi->dev = dev;
533
534         /*
535          * Just start the forker thread for our default backing_dev_info,
536          * and add other bdi's to the list. They will get a thread created
537          * on-demand when they need it.
538          */
539         if (bdi_cap_flush_forker(bdi)) {
540                 struct bdi_writeback *wb = &bdi->wb;
541
542                 wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
543                                                 dev_name(dev));
544                 if (IS_ERR(wb->task))
545                         return PTR_ERR(wb->task);
546         }
547
548         bdi_debug_register(bdi, dev_name(dev));
549         set_bit(BDI_registered, &bdi->state);
550
551         spin_lock_bh(&bdi_lock);
552         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
553         spin_unlock_bh(&bdi_lock);
554
555         trace_writeback_bdi_register(bdi);
556         return 0;
557 }
558 EXPORT_SYMBOL(bdi_register);
559
560 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
561 {
562         return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
563 }
564 EXPORT_SYMBOL(bdi_register_dev);
565
566 /*
567  * Remove bdi from the global list and shutdown any threads we have running
568  */
569 static void bdi_wb_shutdown(struct backing_dev_info *bdi)
570 {
571         if (!bdi_cap_writeback_dirty(bdi))
572                 return;
573
574         /*
575          * Make sure nobody finds us on the bdi_list anymore
576          */
577         bdi_remove_from_list(bdi);
578
579         /*
580          * If setup is pending, wait for that to complete first
581          */
582         wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
583                         TASK_UNINTERRUPTIBLE);
584
585         /*
586          * Finally, kill the kernel thread. We don't need to be RCU
587          * safe anymore, since the bdi is gone from visibility. Force
588          * unfreeze of the thread before calling kthread_stop(), otherwise
589          * it would never exet if it is currently stuck in the refrigerator.
590          */
591         if (bdi->wb.task) {
592                 thaw_process(bdi->wb.task);
593                 kthread_stop(bdi->wb.task);
594         }
595 }
596
597 /*
598  * This bdi is going away now, make sure that no super_blocks point to it
599  */
600 static void bdi_prune_sb(struct backing_dev_info *bdi)
601 {
602         struct super_block *sb;
603
604         spin_lock(&sb_lock);
605         list_for_each_entry(sb, &super_blocks, s_list) {
606                 if (sb->s_bdi == bdi)
607                         sb->s_bdi = NULL;
608         }
609         spin_unlock(&sb_lock);
610 }
611
612 void bdi_unregister(struct backing_dev_info *bdi)
613 {
614         if (bdi->dev) {
615                 trace_writeback_bdi_unregister(bdi);
616                 bdi_prune_sb(bdi);
617                 del_timer_sync(&bdi->wb.wakeup_timer);
618
619                 if (!bdi_cap_flush_forker(bdi))
620                         bdi_wb_shutdown(bdi);
621                 bdi_debug_unregister(bdi);
622                 device_unregister(bdi->dev);
623                 bdi->dev = NULL;
624         }
625 }
626 EXPORT_SYMBOL(bdi_unregister);
627
628 static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
629 {
630         memset(wb, 0, sizeof(*wb));
631
632         wb->bdi = bdi;
633         wb->last_old_flush = jiffies;
634         INIT_LIST_HEAD(&wb->b_dirty);
635         INIT_LIST_HEAD(&wb->b_io);
636         INIT_LIST_HEAD(&wb->b_more_io);
637         setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
638 }
639
640 int bdi_init(struct backing_dev_info *bdi)
641 {
642         int i, err;
643
644         bdi->dev = NULL;
645
646         bdi->min_ratio = 0;
647         bdi->max_ratio = 100;
648         bdi->max_prop_frac = PROP_FRAC_BASE;
649         spin_lock_init(&bdi->wb_lock);
650         INIT_LIST_HEAD(&bdi->bdi_list);
651         INIT_LIST_HEAD(&bdi->work_list);
652
653         bdi_wb_init(&bdi->wb, bdi);
654
655         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
656                 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
657                 if (err)
658                         goto err;
659         }
660
661         bdi->dirty_exceeded = 0;
662         err = prop_local_init_percpu(&bdi->completions);
663
664         if (err) {
665 err:
666                 while (i--)
667                         percpu_counter_destroy(&bdi->bdi_stat[i]);
668         }
669
670         return err;
671 }
672 EXPORT_SYMBOL(bdi_init);
673
674 void bdi_destroy(struct backing_dev_info *bdi)
675 {
676         int i;
677
678         /*
679          * Splice our entries to the default_backing_dev_info, if this
680          * bdi disappears
681          */
682         if (bdi_has_dirty_io(bdi)) {
683                 struct bdi_writeback *dst = &default_backing_dev_info.wb;
684
685                 spin_lock(&inode_wb_list_lock);
686                 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
687                 list_splice(&bdi->wb.b_io, &dst->b_io);
688                 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
689                 spin_unlock(&inode_wb_list_lock);
690         }
691
692         bdi_unregister(bdi);
693
694         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
695                 percpu_counter_destroy(&bdi->bdi_stat[i]);
696
697         prop_local_destroy_percpu(&bdi->completions);
698 }
699 EXPORT_SYMBOL(bdi_destroy);
700
701 /*
702  * For use from filesystems to quickly init and register a bdi associated
703  * with dirty writeback
704  */
705 int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
706                            unsigned int cap)
707 {
708         char tmp[32];
709         int err;
710
711         bdi->name = name;
712         bdi->capabilities = cap;
713         err = bdi_init(bdi);
714         if (err)
715                 return err;
716
717         sprintf(tmp, "%.28s%s", name, "-%d");
718         err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
719         if (err) {
720                 bdi_destroy(bdi);
721                 return err;
722         }
723
724         return 0;
725 }
726 EXPORT_SYMBOL(bdi_setup_and_register);
727
728 static wait_queue_head_t congestion_wqh[2] = {
729                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
730                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
731         };
732 static atomic_t nr_bdi_congested[2];
733
734 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
735 {
736         enum bdi_state bit;
737         wait_queue_head_t *wqh = &congestion_wqh[sync];
738
739         bit = sync ? BDI_sync_congested : BDI_async_congested;
740         if (test_and_clear_bit(bit, &bdi->state))
741                 atomic_dec(&nr_bdi_congested[sync]);
742         smp_mb__after_clear_bit();
743         if (waitqueue_active(wqh))
744                 wake_up(wqh);
745 }
746 EXPORT_SYMBOL(clear_bdi_congested);
747
748 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
749 {
750         enum bdi_state bit;
751
752         bit = sync ? BDI_sync_congested : BDI_async_congested;
753         if (!test_and_set_bit(bit, &bdi->state))
754                 atomic_inc(&nr_bdi_congested[sync]);
755 }
756 EXPORT_SYMBOL(set_bdi_congested);
757
758 /**
759  * congestion_wait - wait for a backing_dev to become uncongested
760  * @sync: SYNC or ASYNC IO
761  * @timeout: timeout in jiffies
762  *
763  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
764  * write congestion.  If no backing_devs are congested then just wait for the
765  * next write to be completed.
766  */
767 long congestion_wait(int sync, long timeout)
768 {
769         long ret;
770         unsigned long start = jiffies;
771         DEFINE_WAIT(wait);
772         wait_queue_head_t *wqh = &congestion_wqh[sync];
773
774         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
775         ret = io_schedule_timeout(timeout);
776         finish_wait(wqh, &wait);
777
778         trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
779                                         jiffies_to_usecs(jiffies - start));
780
781         return ret;
782 }
783 EXPORT_SYMBOL(congestion_wait);
784
785 /**
786  * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
787  * @zone: A zone to check if it is heavily congested
788  * @sync: SYNC or ASYNC IO
789  * @timeout: timeout in jiffies
790  *
791  * In the event of a congested backing_dev (any backing_dev) and the given
792  * @zone has experienced recent congestion, this waits for up to @timeout
793  * jiffies for either a BDI to exit congestion of the given @sync queue
794  * or a write to complete.
795  *
796  * In the absense of zone congestion, cond_resched() is called to yield
797  * the processor if necessary but otherwise does not sleep.
798  *
799  * The return value is 0 if the sleep is for the full timeout. Otherwise,
800  * it is the number of jiffies that were still remaining when the function
801  * returned. return_value == timeout implies the function did not sleep.
802  */
803 long wait_iff_congested(struct zone *zone, int sync, long timeout)
804 {
805         long ret;
806         unsigned long start = jiffies;
807         DEFINE_WAIT(wait);
808         wait_queue_head_t *wqh = &congestion_wqh[sync];
809
810         /*
811          * If there is no congestion, or heavy congestion is not being
812          * encountered in the current zone, yield if necessary instead
813          * of sleeping on the congestion queue
814          */
815         if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
816                         !zone_is_reclaim_congested(zone)) {
817                 cond_resched();
818
819                 /* In case we scheduled, work out time remaining */
820                 ret = timeout - (jiffies - start);
821                 if (ret < 0)
822                         ret = 0;
823
824                 goto out;
825         }
826
827         /* Sleep until uncongested or a write happens */
828         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
829         ret = io_schedule_timeout(timeout);
830         finish_wait(wqh, &wait);
831
832 out:
833         trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
834                                         jiffies_to_usecs(jiffies - start));
835
836         return ret;
837 }
838 EXPORT_SYMBOL(wait_iff_congested);