Merge branch 'fixes-for-3.6' of git://git.kernel.org/pub/scm/linux/kernel/git/coolone...
[platform/adaptation/renesas_rcar/renesas_kernel.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 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 void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
43 {
44         if (wb1 < wb2) {
45                 spin_lock(&wb1->list_lock);
46                 spin_lock_nested(&wb2->list_lock, 1);
47         } else {
48                 spin_lock(&wb2->list_lock);
49                 spin_lock_nested(&wb1->list_lock, 1);
50         }
51 }
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;
72         struct inode *inode;
73
74         nr_dirty = nr_io = nr_more_io = 0;
75         spin_lock(&wb->list_lock);
76         list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
77                 nr_dirty++;
78         list_for_each_entry(inode, &wb->b_io, i_wb_list)
79                 nr_io++;
80         list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
81                 nr_more_io++;
82         spin_unlock(&wb->list_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:       %10lu kB\n"
90                    "BdiReclaimable:     %10lu kB\n"
91                    "BdiDirtyThresh:     %10lu kB\n"
92                    "DirtyThresh:        %10lu kB\n"
93                    "BackgroundThresh:   %10lu kB\n"
94                    "BdiDirtied:         %10lu kB\n"
95                    "BdiWritten:         %10lu kB\n"
96                    "BdiWriteBandwidth:  %10lu kBps\n"
97                    "b_dirty:            %10lu\n"
98                    "b_io:               %10lu\n"
99                    "b_more_io:          %10lu\n"
100                    "bdi_list:           %10u\n"
101                    "state:              %10lx\n",
102                    (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
103                    (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
104                    K(bdi_thresh),
105                    K(dirty_thresh),
106                    K(background_thresh),
107                    (unsigned long) K(bdi_stat(bdi, BDI_DIRTIED)),
108                    (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
109                    (unsigned long) K(bdi->write_bandwidth),
110                    nr_dirty,
111                    nr_io,
112                    nr_more_io,
113                    !list_empty(&bdi->bdi_list), bdi->state);
114 #undef K
115
116         return 0;
117 }
118
119 static int bdi_debug_stats_open(struct inode *inode, struct file *file)
120 {
121         return single_open(file, bdi_debug_stats_show, inode->i_private);
122 }
123
124 static const struct file_operations bdi_debug_stats_fops = {
125         .open           = bdi_debug_stats_open,
126         .read           = seq_read,
127         .llseek         = seq_lseek,
128         .release        = single_release,
129 };
130
131 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
132 {
133         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
134         bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
135                                                bdi, &bdi_debug_stats_fops);
136 }
137
138 static void bdi_debug_unregister(struct backing_dev_info *bdi)
139 {
140         debugfs_remove(bdi->debug_stats);
141         debugfs_remove(bdi->debug_dir);
142 }
143 #else
144 static inline void bdi_debug_init(void)
145 {
146 }
147 static inline void bdi_debug_register(struct backing_dev_info *bdi,
148                                       const char *name)
149 {
150 }
151 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
152 {
153 }
154 #endif
155
156 static ssize_t read_ahead_kb_store(struct device *dev,
157                                   struct device_attribute *attr,
158                                   const char *buf, size_t count)
159 {
160         struct backing_dev_info *bdi = dev_get_drvdata(dev);
161         char *end;
162         unsigned long read_ahead_kb;
163         ssize_t ret = -EINVAL;
164
165         read_ahead_kb = simple_strtoul(buf, &end, 10);
166         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
167                 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
168                 ret = count;
169         }
170         return ret;
171 }
172
173 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
174
175 #define BDI_SHOW(name, expr)                                            \
176 static ssize_t name##_show(struct device *dev,                          \
177                            struct device_attribute *attr, char *page)   \
178 {                                                                       \
179         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
180                                                                         \
181         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
182 }
183
184 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
185
186 static ssize_t min_ratio_store(struct device *dev,
187                 struct device_attribute *attr, const char *buf, size_t count)
188 {
189         struct backing_dev_info *bdi = dev_get_drvdata(dev);
190         char *end;
191         unsigned int ratio;
192         ssize_t ret = -EINVAL;
193
194         ratio = simple_strtoul(buf, &end, 10);
195         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
196                 ret = bdi_set_min_ratio(bdi, ratio);
197                 if (!ret)
198                         ret = count;
199         }
200         return ret;
201 }
202 BDI_SHOW(min_ratio, bdi->min_ratio)
203
204 static ssize_t max_ratio_store(struct device *dev,
205                 struct device_attribute *attr, const char *buf, size_t count)
206 {
207         struct backing_dev_info *bdi = dev_get_drvdata(dev);
208         char *end;
209         unsigned int ratio;
210         ssize_t ret = -EINVAL;
211
212         ratio = simple_strtoul(buf, &end, 10);
213         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
214                 ret = bdi_set_max_ratio(bdi, ratio);
215                 if (!ret)
216                         ret = count;
217         }
218         return ret;
219 }
220 BDI_SHOW(max_ratio, bdi->max_ratio)
221
222 #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
223
224 static struct device_attribute bdi_dev_attrs[] = {
225         __ATTR_RW(read_ahead_kb),
226         __ATTR_RW(min_ratio),
227         __ATTR_RW(max_ratio),
228         __ATTR_NULL,
229 };
230
231 static __init int bdi_class_init(void)
232 {
233         bdi_class = class_create(THIS_MODULE, "bdi");
234         if (IS_ERR(bdi_class))
235                 return PTR_ERR(bdi_class);
236
237         bdi_class->dev_attrs = bdi_dev_attrs;
238         bdi_debug_init();
239         return 0;
240 }
241 postcore_initcall(bdi_class_init);
242
243 static int __init default_bdi_init(void)
244 {
245         int err;
246
247         err = bdi_init(&default_backing_dev_info);
248         if (!err)
249                 bdi_register(&default_backing_dev_info, NULL, "default");
250         err = bdi_init(&noop_backing_dev_info);
251
252         return err;
253 }
254 subsys_initcall(default_bdi_init);
255
256 int bdi_has_dirty_io(struct backing_dev_info *bdi)
257 {
258         return wb_has_dirty_io(&bdi->wb);
259 }
260
261 static void wakeup_timer_fn(unsigned long data)
262 {
263         struct backing_dev_info *bdi = (struct backing_dev_info *)data;
264
265         spin_lock_bh(&bdi->wb_lock);
266         if (bdi->wb.task) {
267                 trace_writeback_wake_thread(bdi);
268                 wake_up_process(bdi->wb.task);
269         } else if (bdi->dev) {
270                 /*
271                  * When bdi tasks are inactive for long time, they are killed.
272                  * In this case we have to wake-up the forker thread which
273                  * should create and run the bdi thread.
274                  */
275                 trace_writeback_wake_forker_thread(bdi);
276                 wake_up_process(default_backing_dev_info.wb.task);
277         }
278         spin_unlock_bh(&bdi->wb_lock);
279 }
280
281 /*
282  * This function is used when the first inode for this bdi is marked dirty. It
283  * wakes-up the corresponding bdi thread which should then take care of the
284  * periodic background write-out of dirty inodes. Since the write-out would
285  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
286  * set up a timer which wakes the bdi thread up later.
287  *
288  * Note, we wouldn't bother setting up the timer, but this function is on the
289  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
290  * by delaying the wake-up.
291  */
292 void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
293 {
294         unsigned long timeout;
295
296         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
297         mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout);
298 }
299
300 /*
301  * Calculate the longest interval (jiffies) bdi threads are allowed to be
302  * inactive.
303  */
304 static unsigned long bdi_longest_inactive(void)
305 {
306         unsigned long interval;
307
308         interval = msecs_to_jiffies(dirty_writeback_interval * 10);
309         return max(5UL * 60 * HZ, interval);
310 }
311
312 /*
313  * Clear pending bit and wakeup anybody waiting for flusher thread creation or
314  * shutdown
315  */
316 static void bdi_clear_pending(struct backing_dev_info *bdi)
317 {
318         clear_bit(BDI_pending, &bdi->state);
319         smp_mb__after_clear_bit();
320         wake_up_bit(&bdi->state, BDI_pending);
321 }
322
323 static int bdi_forker_thread(void *ptr)
324 {
325         struct bdi_writeback *me = ptr;
326
327         current->flags |= PF_SWAPWRITE;
328         set_freezable();
329
330         /*
331          * Our parent may run at a different priority, just set us to normal
332          */
333         set_user_nice(current, 0);
334
335         for (;;) {
336                 struct task_struct *task = NULL;
337                 struct backing_dev_info *bdi;
338                 enum {
339                         NO_ACTION,   /* Nothing to do */
340                         FORK_THREAD, /* Fork bdi thread */
341                         KILL_THREAD, /* Kill inactive bdi thread */
342                 } action = NO_ACTION;
343
344                 /*
345                  * Temporary measure, we want to make sure we don't see
346                  * dirty data on the default backing_dev_info
347                  */
348                 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
349                         del_timer(&me->wakeup_timer);
350                         wb_do_writeback(me, 0);
351                 }
352
353                 spin_lock_bh(&bdi_lock);
354                 /*
355                  * In the following loop we are going to check whether we have
356                  * some work to do without any synchronization with tasks
357                  * waking us up to do work for them. Set the task state here
358                  * so that we don't miss wakeups after verifying conditions.
359                  */
360                 set_current_state(TASK_INTERRUPTIBLE);
361
362                 list_for_each_entry(bdi, &bdi_list, bdi_list) {
363                         bool have_dirty_io;
364
365                         if (!bdi_cap_writeback_dirty(bdi) ||
366                              bdi_cap_flush_forker(bdi))
367                                 continue;
368
369                         WARN(!test_bit(BDI_registered, &bdi->state),
370                              "bdi %p/%s is not registered!\n", bdi, bdi->name);
371
372                         have_dirty_io = !list_empty(&bdi->work_list) ||
373                                         wb_has_dirty_io(&bdi->wb);
374
375                         /*
376                          * If the bdi has work to do, but the thread does not
377                          * exist - create it.
378                          */
379                         if (!bdi->wb.task && have_dirty_io) {
380                                 /*
381                                  * Set the pending bit - if someone will try to
382                                  * unregister this bdi - it'll wait on this bit.
383                                  */
384                                 set_bit(BDI_pending, &bdi->state);
385                                 action = FORK_THREAD;
386                                 break;
387                         }
388
389                         spin_lock(&bdi->wb_lock);
390
391                         /*
392                          * If there is no work to do and the bdi thread was
393                          * inactive long enough - kill it. The wb_lock is taken
394                          * to make sure no-one adds more work to this bdi and
395                          * wakes the bdi thread up.
396                          */
397                         if (bdi->wb.task && !have_dirty_io &&
398                             time_after(jiffies, bdi->wb.last_active +
399                                                 bdi_longest_inactive())) {
400                                 task = bdi->wb.task;
401                                 bdi->wb.task = NULL;
402                                 spin_unlock(&bdi->wb_lock);
403                                 set_bit(BDI_pending, &bdi->state);
404                                 action = KILL_THREAD;
405                                 break;
406                         }
407                         spin_unlock(&bdi->wb_lock);
408                 }
409                 spin_unlock_bh(&bdi_lock);
410
411                 /* Keep working if default bdi still has things to do */
412                 if (!list_empty(&me->bdi->work_list))
413                         __set_current_state(TASK_RUNNING);
414
415                 switch (action) {
416                 case FORK_THREAD:
417                         __set_current_state(TASK_RUNNING);
418                         task = kthread_create(bdi_writeback_thread, &bdi->wb,
419                                               "flush-%s", dev_name(bdi->dev));
420                         if (IS_ERR(task)) {
421                                 /*
422                                  * If thread creation fails, force writeout of
423                                  * the bdi from the thread. Hopefully 1024 is
424                                  * large enough for efficient IO.
425                                  */
426                                 writeback_inodes_wb(&bdi->wb, 1024,
427                                                     WB_REASON_FORKER_THREAD);
428                         } else {
429                                 /*
430                                  * The spinlock makes sure we do not lose
431                                  * wake-ups when racing with 'bdi_queue_work()'.
432                                  * And as soon as the bdi thread is visible, we
433                                  * can start it.
434                                  */
435                                 spin_lock_bh(&bdi->wb_lock);
436                                 bdi->wb.task = task;
437                                 spin_unlock_bh(&bdi->wb_lock);
438                                 wake_up_process(task);
439                         }
440                         bdi_clear_pending(bdi);
441                         break;
442
443                 case KILL_THREAD:
444                         __set_current_state(TASK_RUNNING);
445                         kthread_stop(task);
446                         bdi_clear_pending(bdi);
447                         break;
448
449                 case NO_ACTION:
450                         if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
451                                 /*
452                                  * There are no dirty data. The only thing we
453                                  * should now care about is checking for
454                                  * inactive bdi threads and killing them. Thus,
455                                  * let's sleep for longer time, save energy and
456                                  * be friendly for battery-driven devices.
457                                  */
458                                 schedule_timeout(bdi_longest_inactive());
459                         else
460                                 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
461                         try_to_freeze();
462                         break;
463                 }
464         }
465
466         return 0;
467 }
468
469 /*
470  * Remove bdi from bdi_list, and ensure that it is no longer visible
471  */
472 static void bdi_remove_from_list(struct backing_dev_info *bdi)
473 {
474         spin_lock_bh(&bdi_lock);
475         list_del_rcu(&bdi->bdi_list);
476         spin_unlock_bh(&bdi_lock);
477
478         synchronize_rcu_expedited();
479 }
480
481 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
482                 const char *fmt, ...)
483 {
484         va_list args;
485         struct device *dev;
486
487         if (bdi->dev)   /* The driver needs to use separate queues per device */
488                 return 0;
489
490         va_start(args, fmt);
491         dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
492         va_end(args);
493         if (IS_ERR(dev))
494                 return PTR_ERR(dev);
495
496         bdi->dev = dev;
497
498         /*
499          * Just start the forker thread for our default backing_dev_info,
500          * and add other bdi's to the list. They will get a thread created
501          * on-demand when they need it.
502          */
503         if (bdi_cap_flush_forker(bdi)) {
504                 struct bdi_writeback *wb = &bdi->wb;
505
506                 wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
507                                                 dev_name(dev));
508                 if (IS_ERR(wb->task))
509                         return PTR_ERR(wb->task);
510         }
511
512         bdi_debug_register(bdi, dev_name(dev));
513         set_bit(BDI_registered, &bdi->state);
514
515         spin_lock_bh(&bdi_lock);
516         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
517         spin_unlock_bh(&bdi_lock);
518
519         trace_writeback_bdi_register(bdi);
520         return 0;
521 }
522 EXPORT_SYMBOL(bdi_register);
523
524 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
525 {
526         return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
527 }
528 EXPORT_SYMBOL(bdi_register_dev);
529
530 /*
531  * Remove bdi from the global list and shutdown any threads we have running
532  */
533 static void bdi_wb_shutdown(struct backing_dev_info *bdi)
534 {
535         struct task_struct *task;
536
537         if (!bdi_cap_writeback_dirty(bdi))
538                 return;
539
540         /*
541          * Make sure nobody finds us on the bdi_list anymore
542          */
543         bdi_remove_from_list(bdi);
544
545         /*
546          * If setup is pending, wait for that to complete first
547          */
548         wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
549                         TASK_UNINTERRUPTIBLE);
550
551         /*
552          * Finally, kill the kernel thread. We don't need to be RCU
553          * safe anymore, since the bdi is gone from visibility.
554          */
555         spin_lock_bh(&bdi->wb_lock);
556         task = bdi->wb.task;
557         bdi->wb.task = NULL;
558         spin_unlock_bh(&bdi->wb_lock);
559
560         if (task)
561                 kthread_stop(task);
562 }
563
564 /*
565  * This bdi is going away now, make sure that no super_blocks point to it
566  */
567 static void bdi_prune_sb(struct backing_dev_info *bdi)
568 {
569         struct super_block *sb;
570
571         spin_lock(&sb_lock);
572         list_for_each_entry(sb, &super_blocks, s_list) {
573                 if (sb->s_bdi == bdi)
574                         sb->s_bdi = &default_backing_dev_info;
575         }
576         spin_unlock(&sb_lock);
577 }
578
579 void bdi_unregister(struct backing_dev_info *bdi)
580 {
581         struct device *dev = bdi->dev;
582
583         if (dev) {
584                 bdi_set_min_ratio(bdi, 0);
585                 trace_writeback_bdi_unregister(bdi);
586                 bdi_prune_sb(bdi);
587                 del_timer_sync(&bdi->wb.wakeup_timer);
588
589                 if (!bdi_cap_flush_forker(bdi))
590                         bdi_wb_shutdown(bdi);
591                 bdi_debug_unregister(bdi);
592
593                 spin_lock_bh(&bdi->wb_lock);
594                 bdi->dev = NULL;
595                 spin_unlock_bh(&bdi->wb_lock);
596
597                 device_unregister(dev);
598         }
599 }
600 EXPORT_SYMBOL(bdi_unregister);
601
602 static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
603 {
604         memset(wb, 0, sizeof(*wb));
605
606         wb->bdi = bdi;
607         wb->last_old_flush = jiffies;
608         INIT_LIST_HEAD(&wb->b_dirty);
609         INIT_LIST_HEAD(&wb->b_io);
610         INIT_LIST_HEAD(&wb->b_more_io);
611         spin_lock_init(&wb->list_lock);
612         setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
613 }
614
615 /*
616  * Initial write bandwidth: 100 MB/s
617  */
618 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
619
620 int bdi_init(struct backing_dev_info *bdi)
621 {
622         int i, err;
623
624         bdi->dev = NULL;
625
626         bdi->min_ratio = 0;
627         bdi->max_ratio = 100;
628         bdi->max_prop_frac = FPROP_FRAC_BASE;
629         spin_lock_init(&bdi->wb_lock);
630         INIT_LIST_HEAD(&bdi->bdi_list);
631         INIT_LIST_HEAD(&bdi->work_list);
632
633         bdi_wb_init(&bdi->wb, bdi);
634
635         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
636                 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
637                 if (err)
638                         goto err;
639         }
640
641         bdi->dirty_exceeded = 0;
642
643         bdi->bw_time_stamp = jiffies;
644         bdi->written_stamp = 0;
645
646         bdi->balanced_dirty_ratelimit = INIT_BW;
647         bdi->dirty_ratelimit = INIT_BW;
648         bdi->write_bandwidth = INIT_BW;
649         bdi->avg_write_bandwidth = INIT_BW;
650
651         err = fprop_local_init_percpu(&bdi->completions);
652
653         if (err) {
654 err:
655                 while (i--)
656                         percpu_counter_destroy(&bdi->bdi_stat[i]);
657         }
658
659         return err;
660 }
661 EXPORT_SYMBOL(bdi_init);
662
663 void bdi_destroy(struct backing_dev_info *bdi)
664 {
665         int i;
666
667         /*
668          * Splice our entries to the default_backing_dev_info, if this
669          * bdi disappears
670          */
671         if (bdi_has_dirty_io(bdi)) {
672                 struct bdi_writeback *dst = &default_backing_dev_info.wb;
673
674                 bdi_lock_two(&bdi->wb, dst);
675                 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
676                 list_splice(&bdi->wb.b_io, &dst->b_io);
677                 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
678                 spin_unlock(&bdi->wb.list_lock);
679                 spin_unlock(&dst->list_lock);
680         }
681
682         bdi_unregister(bdi);
683
684         /*
685          * If bdi_unregister() had already been called earlier, the
686          * wakeup_timer could still be armed because bdi_prune_sb()
687          * can race with the bdi_wakeup_thread_delayed() calls from
688          * __mark_inode_dirty().
689          */
690         del_timer_sync(&bdi->wb.wakeup_timer);
691
692         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
693                 percpu_counter_destroy(&bdi->bdi_stat[i]);
694
695         fprop_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 static atomic_t nr_bdi_congested[2];
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         if (test_and_clear_bit(bit, &bdi->state))
739                 atomic_dec(&nr_bdi_congested[sync]);
740         smp_mb__after_clear_bit();
741         if (waitqueue_active(wqh))
742                 wake_up(wqh);
743 }
744 EXPORT_SYMBOL(clear_bdi_congested);
745
746 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
747 {
748         enum bdi_state bit;
749
750         bit = sync ? BDI_sync_congested : BDI_async_congested;
751         if (!test_and_set_bit(bit, &bdi->state))
752                 atomic_inc(&nr_bdi_congested[sync]);
753 }
754 EXPORT_SYMBOL(set_bdi_congested);
755
756 /**
757  * congestion_wait - wait for a backing_dev to become uncongested
758  * @sync: SYNC or ASYNC IO
759  * @timeout: timeout in jiffies
760  *
761  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
762  * write congestion.  If no backing_devs are congested then just wait for the
763  * next write to be completed.
764  */
765 long congestion_wait(int sync, long timeout)
766 {
767         long ret;
768         unsigned long start = jiffies;
769         DEFINE_WAIT(wait);
770         wait_queue_head_t *wqh = &congestion_wqh[sync];
771
772         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
773         ret = io_schedule_timeout(timeout);
774         finish_wait(wqh, &wait);
775
776         trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
777                                         jiffies_to_usecs(jiffies - start));
778
779         return ret;
780 }
781 EXPORT_SYMBOL(congestion_wait);
782
783 /**
784  * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
785  * @zone: A zone to check if it is heavily congested
786  * @sync: SYNC or ASYNC IO
787  * @timeout: timeout in jiffies
788  *
789  * In the event of a congested backing_dev (any backing_dev) and the given
790  * @zone has experienced recent congestion, this waits for up to @timeout
791  * jiffies for either a BDI to exit congestion of the given @sync queue
792  * or a write to complete.
793  *
794  * In the absence of zone congestion, cond_resched() is called to yield
795  * the processor if necessary but otherwise does not sleep.
796  *
797  * The return value is 0 if the sleep is for the full timeout. Otherwise,
798  * it is the number of jiffies that were still remaining when the function
799  * returned. return_value == timeout implies the function did not sleep.
800  */
801 long wait_iff_congested(struct zone *zone, int sync, long timeout)
802 {
803         long ret;
804         unsigned long start = jiffies;
805         DEFINE_WAIT(wait);
806         wait_queue_head_t *wqh = &congestion_wqh[sync];
807
808         /*
809          * If there is no congestion, or heavy congestion is not being
810          * encountered in the current zone, yield if necessary instead
811          * of sleeping on the congestion queue
812          */
813         if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
814                         !zone_is_reclaim_congested(zone)) {
815                 cond_resched();
816
817                 /* In case we scheduled, work out time remaining */
818                 ret = timeout - (jiffies - start);
819                 if (ret < 0)
820                         ret = 0;
821
822                 goto out;
823         }
824
825         /* Sleep until uncongested or a write happens */
826         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
827         ret = io_schedule_timeout(timeout);
828         finish_wait(wqh, &wait);
829
830 out:
831         trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
832                                         jiffies_to_usecs(jiffies - start));
833
834         return ret;
835 }
836 EXPORT_SYMBOL(wait_iff_congested);
837
838 int pdflush_proc_obsolete(struct ctl_table *table, int write,
839                         void __user *buffer, size_t *lenp, loff_t *ppos)
840 {
841         char kbuf[] = "0\n";
842
843         if (*ppos) {
844                 *lenp = 0;
845                 return 0;
846         }
847
848         if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
849                 return -EFAULT;
850         printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
851                         table->procname);
852
853         *lenp = 2;
854         *ppos += *lenp;
855         return 2;
856 }