PCI: Fix regression in pci_restore_state(), v3
[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 struct backing_dev_info default_backing_dev_info = {
18         .name           = "default",
19         .ra_pages       = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
20         .state          = 0,
21         .capabilities   = BDI_CAP_MAP_COPY,
22 };
23 EXPORT_SYMBOL_GPL(default_backing_dev_info);
24
25 struct backing_dev_info noop_backing_dev_info = {
26         .name           = "noop",
27         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
28 };
29 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
30
31 static struct class *bdi_class;
32
33 /*
34  * bdi_lock protects updates to bdi_list and bdi_pending_list, as well as
35  * reader side protection for bdi_pending_list. bdi_list has RCU reader side
36  * locking.
37  */
38 DEFINE_SPINLOCK(bdi_lock);
39 LIST_HEAD(bdi_list);
40 LIST_HEAD(bdi_pending_list);
41
42 static struct task_struct *sync_supers_tsk;
43 static struct timer_list sync_supers_timer;
44
45 static int bdi_sync_supers(void *);
46 static void sync_supers_timer_fn(unsigned long);
47
48 void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
49 {
50         if (wb1 < wb2) {
51                 spin_lock(&wb1->list_lock);
52                 spin_lock_nested(&wb2->list_lock, 1);
53         } else {
54                 spin_lock(&wb2->list_lock);
55                 spin_lock_nested(&wb1->list_lock, 1);
56         }
57 }
58
59 #ifdef CONFIG_DEBUG_FS
60 #include <linux/debugfs.h>
61 #include <linux/seq_file.h>
62
63 static struct dentry *bdi_debug_root;
64
65 static void bdi_debug_init(void)
66 {
67         bdi_debug_root = debugfs_create_dir("bdi", NULL);
68 }
69
70 static int bdi_debug_stats_show(struct seq_file *m, void *v)
71 {
72         struct backing_dev_info *bdi = m->private;
73         struct bdi_writeback *wb = &bdi->wb;
74         unsigned long background_thresh;
75         unsigned long dirty_thresh;
76         unsigned long bdi_thresh;
77         unsigned long nr_dirty, nr_io, nr_more_io;
78         struct inode *inode;
79
80         nr_dirty = nr_io = nr_more_io = 0;
81         spin_lock(&wb->list_lock);
82         list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
83                 nr_dirty++;
84         list_for_each_entry(inode, &wb->b_io, i_wb_list)
85                 nr_io++;
86         list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
87                 nr_more_io++;
88         spin_unlock(&wb->list_lock);
89
90         global_dirty_limits(&background_thresh, &dirty_thresh);
91         bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
92
93 #define K(x) ((x) << (PAGE_SHIFT - 10))
94         seq_printf(m,
95                    "BdiWriteback:       %10lu kB\n"
96                    "BdiReclaimable:     %10lu kB\n"
97                    "BdiDirtyThresh:     %10lu kB\n"
98                    "DirtyThresh:        %10lu kB\n"
99                    "BackgroundThresh:   %10lu kB\n"
100                    "BdiDirtied:         %10lu kB\n"
101                    "BdiWritten:         %10lu kB\n"
102                    "BdiWriteBandwidth:  %10lu kBps\n"
103                    "b_dirty:            %10lu\n"
104                    "b_io:               %10lu\n"
105                    "b_more_io:          %10lu\n"
106                    "bdi_list:           %10u\n"
107                    "state:              %10lx\n",
108                    (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
109                    (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
110                    K(bdi_thresh),
111                    K(dirty_thresh),
112                    K(background_thresh),
113                    (unsigned long) K(bdi_stat(bdi, BDI_DIRTIED)),
114                    (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
115                    (unsigned long) K(bdi->write_bandwidth),
116                    nr_dirty,
117                    nr_io,
118                    nr_more_io,
119                    !list_empty(&bdi->bdi_list), bdi->state);
120 #undef K
121
122         return 0;
123 }
124
125 static int bdi_debug_stats_open(struct inode *inode, struct file *file)
126 {
127         return single_open(file, bdi_debug_stats_show, inode->i_private);
128 }
129
130 static const struct file_operations bdi_debug_stats_fops = {
131         .open           = bdi_debug_stats_open,
132         .read           = seq_read,
133         .llseek         = seq_lseek,
134         .release        = single_release,
135 };
136
137 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
138 {
139         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
140         bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
141                                                bdi, &bdi_debug_stats_fops);
142 }
143
144 static void bdi_debug_unregister(struct backing_dev_info *bdi)
145 {
146         debugfs_remove(bdi->debug_stats);
147         debugfs_remove(bdi->debug_dir);
148 }
149 #else
150 static inline void bdi_debug_init(void)
151 {
152 }
153 static inline void bdi_debug_register(struct backing_dev_info *bdi,
154                                       const char *name)
155 {
156 }
157 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
158 {
159 }
160 #endif
161
162 static ssize_t read_ahead_kb_store(struct device *dev,
163                                   struct device_attribute *attr,
164                                   const char *buf, size_t count)
165 {
166         struct backing_dev_info *bdi = dev_get_drvdata(dev);
167         char *end;
168         unsigned long read_ahead_kb;
169         ssize_t ret = -EINVAL;
170
171         read_ahead_kb = simple_strtoul(buf, &end, 10);
172         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
173                 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
174                 ret = count;
175         }
176         return ret;
177 }
178
179 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
180
181 #define BDI_SHOW(name, expr)                                            \
182 static ssize_t name##_show(struct device *dev,                          \
183                            struct device_attribute *attr, char *page)   \
184 {                                                                       \
185         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
186                                                                         \
187         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
188 }
189
190 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
191
192 static ssize_t min_ratio_store(struct device *dev,
193                 struct device_attribute *attr, const char *buf, size_t count)
194 {
195         struct backing_dev_info *bdi = dev_get_drvdata(dev);
196         char *end;
197         unsigned int ratio;
198         ssize_t ret = -EINVAL;
199
200         ratio = simple_strtoul(buf, &end, 10);
201         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
202                 ret = bdi_set_min_ratio(bdi, ratio);
203                 if (!ret)
204                         ret = count;
205         }
206         return ret;
207 }
208 BDI_SHOW(min_ratio, bdi->min_ratio)
209
210 static ssize_t max_ratio_store(struct device *dev,
211                 struct device_attribute *attr, const char *buf, size_t count)
212 {
213         struct backing_dev_info *bdi = dev_get_drvdata(dev);
214         char *end;
215         unsigned int ratio;
216         ssize_t ret = -EINVAL;
217
218         ratio = simple_strtoul(buf, &end, 10);
219         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
220                 ret = bdi_set_max_ratio(bdi, ratio);
221                 if (!ret)
222                         ret = count;
223         }
224         return ret;
225 }
226 BDI_SHOW(max_ratio, bdi->max_ratio)
227
228 #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
229
230 static struct device_attribute bdi_dev_attrs[] = {
231         __ATTR_RW(read_ahead_kb),
232         __ATTR_RW(min_ratio),
233         __ATTR_RW(max_ratio),
234         __ATTR_NULL,
235 };
236
237 static __init int bdi_class_init(void)
238 {
239         bdi_class = class_create(THIS_MODULE, "bdi");
240         if (IS_ERR(bdi_class))
241                 return PTR_ERR(bdi_class);
242
243         bdi_class->dev_attrs = bdi_dev_attrs;
244         bdi_debug_init();
245         return 0;
246 }
247 postcore_initcall(bdi_class_init);
248
249 static int __init default_bdi_init(void)
250 {
251         int err;
252
253         sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
254         BUG_ON(IS_ERR(sync_supers_tsk));
255
256         setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
257         bdi_arm_supers_timer();
258
259         err = bdi_init(&default_backing_dev_info);
260         if (!err)
261                 bdi_register(&default_backing_dev_info, NULL, "default");
262         err = bdi_init(&noop_backing_dev_info);
263
264         return err;
265 }
266 subsys_initcall(default_bdi_init);
267
268 int bdi_has_dirty_io(struct backing_dev_info *bdi)
269 {
270         return wb_has_dirty_io(&bdi->wb);
271 }
272
273 /*
274  * kupdated() used to do this. We cannot do it from the bdi_forker_thread()
275  * or we risk deadlocking on ->s_umount. The longer term solution would be
276  * to implement sync_supers_bdi() or similar and simply do it from the
277  * bdi writeback thread individually.
278  */
279 static int bdi_sync_supers(void *unused)
280 {
281         set_user_nice(current, 0);
282
283         while (!kthread_should_stop()) {
284                 set_current_state(TASK_INTERRUPTIBLE);
285                 schedule();
286
287                 /*
288                  * Do this periodically, like kupdated() did before.
289                  */
290                 sync_supers();
291         }
292
293         return 0;
294 }
295
296 void bdi_arm_supers_timer(void)
297 {
298         unsigned long next;
299
300         if (!dirty_writeback_interval)
301                 return;
302
303         next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
304         mod_timer(&sync_supers_timer, round_jiffies_up(next));
305 }
306
307 static void sync_supers_timer_fn(unsigned long unused)
308 {
309         wake_up_process(sync_supers_tsk);
310         bdi_arm_supers_timer();
311 }
312
313 static void wakeup_timer_fn(unsigned long data)
314 {
315         struct backing_dev_info *bdi = (struct backing_dev_info *)data;
316
317         spin_lock_bh(&bdi->wb_lock);
318         if (bdi->wb.task) {
319                 trace_writeback_wake_thread(bdi);
320                 wake_up_process(bdi->wb.task);
321         } else if (bdi->dev) {
322                 /*
323                  * When bdi tasks are inactive for long time, they are killed.
324                  * In this case we have to wake-up the forker thread which
325                  * should create and run the bdi thread.
326                  */
327                 trace_writeback_wake_forker_thread(bdi);
328                 wake_up_process(default_backing_dev_info.wb.task);
329         }
330         spin_unlock_bh(&bdi->wb_lock);
331 }
332
333 /*
334  * This function is used when the first inode for this bdi is marked dirty. It
335  * wakes-up the corresponding bdi thread which should then take care of the
336  * periodic background write-out of dirty inodes. Since the write-out would
337  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
338  * set up a timer which wakes the bdi thread up later.
339  *
340  * Note, we wouldn't bother setting up the timer, but this function is on the
341  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
342  * by delaying the wake-up.
343  */
344 void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
345 {
346         unsigned long timeout;
347
348         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
349         mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout);
350 }
351
352 /*
353  * Calculate the longest interval (jiffies) bdi threads are allowed to be
354  * inactive.
355  */
356 static unsigned long bdi_longest_inactive(void)
357 {
358         unsigned long interval;
359
360         interval = msecs_to_jiffies(dirty_writeback_interval * 10);
361         return max(5UL * 60 * HZ, interval);
362 }
363
364 /*
365  * Clear pending bit and wakeup anybody waiting for flusher thread creation or
366  * shutdown
367  */
368 static void bdi_clear_pending(struct backing_dev_info *bdi)
369 {
370         clear_bit(BDI_pending, &bdi->state);
371         smp_mb__after_clear_bit();
372         wake_up_bit(&bdi->state, BDI_pending);
373 }
374
375 static int bdi_forker_thread(void *ptr)
376 {
377         struct bdi_writeback *me = ptr;
378
379         current->flags |= PF_SWAPWRITE;
380         set_freezable();
381
382         /*
383          * Our parent may run at a different priority, just set us to normal
384          */
385         set_user_nice(current, 0);
386
387         for (;;) {
388                 struct task_struct *task = NULL;
389                 struct backing_dev_info *bdi;
390                 enum {
391                         NO_ACTION,   /* Nothing to do */
392                         FORK_THREAD, /* Fork bdi thread */
393                         KILL_THREAD, /* Kill inactive bdi thread */
394                 } action = NO_ACTION;
395
396                 /*
397                  * Temporary measure, we want to make sure we don't see
398                  * dirty data on the default backing_dev_info
399                  */
400                 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
401                         del_timer(&me->wakeup_timer);
402                         wb_do_writeback(me, 0);
403                 }
404
405                 spin_lock_bh(&bdi_lock);
406                 /*
407                  * In the following loop we are going to check whether we have
408                  * some work to do without any synchronization with tasks
409                  * waking us up to do work for them. Set the task state here
410                  * so that we don't miss wakeups after verifying conditions.
411                  */
412                 set_current_state(TASK_INTERRUPTIBLE);
413
414                 list_for_each_entry(bdi, &bdi_list, bdi_list) {
415                         bool have_dirty_io;
416
417                         if (!bdi_cap_writeback_dirty(bdi) ||
418                              bdi_cap_flush_forker(bdi))
419                                 continue;
420
421                         WARN(!test_bit(BDI_registered, &bdi->state),
422                              "bdi %p/%s is not registered!\n", bdi, bdi->name);
423
424                         have_dirty_io = !list_empty(&bdi->work_list) ||
425                                         wb_has_dirty_io(&bdi->wb);
426
427                         /*
428                          * If the bdi has work to do, but the thread does not
429                          * exist - create it.
430                          */
431                         if (!bdi->wb.task && have_dirty_io) {
432                                 /*
433                                  * Set the pending bit - if someone will try to
434                                  * unregister this bdi - it'll wait on this bit.
435                                  */
436                                 set_bit(BDI_pending, &bdi->state);
437                                 action = FORK_THREAD;
438                                 break;
439                         }
440
441                         spin_lock(&bdi->wb_lock);
442
443                         /*
444                          * If there is no work to do and the bdi thread was
445                          * inactive long enough - kill it. The wb_lock is taken
446                          * to make sure no-one adds more work to this bdi and
447                          * wakes the bdi thread up.
448                          */
449                         if (bdi->wb.task && !have_dirty_io &&
450                             time_after(jiffies, bdi->wb.last_active +
451                                                 bdi_longest_inactive())) {
452                                 task = bdi->wb.task;
453                                 bdi->wb.task = NULL;
454                                 spin_unlock(&bdi->wb_lock);
455                                 set_bit(BDI_pending, &bdi->state);
456                                 action = KILL_THREAD;
457                                 break;
458                         }
459                         spin_unlock(&bdi->wb_lock);
460                 }
461                 spin_unlock_bh(&bdi_lock);
462
463                 /* Keep working if default bdi still has things to do */
464                 if (!list_empty(&me->bdi->work_list))
465                         __set_current_state(TASK_RUNNING);
466
467                 switch (action) {
468                 case FORK_THREAD:
469                         __set_current_state(TASK_RUNNING);
470                         task = kthread_create(bdi_writeback_thread, &bdi->wb,
471                                               "flush-%s", dev_name(bdi->dev));
472                         if (IS_ERR(task)) {
473                                 /*
474                                  * If thread creation fails, force writeout of
475                                  * the bdi from the thread. Hopefully 1024 is
476                                  * large enough for efficient IO.
477                                  */
478                                 writeback_inodes_wb(&bdi->wb, 1024,
479                                                     WB_REASON_FORKER_THREAD);
480                         } else {
481                                 /*
482                                  * The spinlock makes sure we do not lose
483                                  * wake-ups when racing with 'bdi_queue_work()'.
484                                  * And as soon as the bdi thread is visible, we
485                                  * can start it.
486                                  */
487                                 spin_lock_bh(&bdi->wb_lock);
488                                 bdi->wb.task = task;
489                                 spin_unlock_bh(&bdi->wb_lock);
490                                 wake_up_process(task);
491                         }
492                         bdi_clear_pending(bdi);
493                         break;
494
495                 case KILL_THREAD:
496                         __set_current_state(TASK_RUNNING);
497                         kthread_stop(task);
498                         bdi_clear_pending(bdi);
499                         break;
500
501                 case NO_ACTION:
502                         if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
503                                 /*
504                                  * There are no dirty data. The only thing we
505                                  * should now care about is checking for
506                                  * inactive bdi threads and killing them. Thus,
507                                  * let's sleep for longer time, save energy and
508                                  * be friendly for battery-driven devices.
509                                  */
510                                 schedule_timeout(bdi_longest_inactive());
511                         else
512                                 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
513                         try_to_freeze();
514                         break;
515                 }
516         }
517
518         return 0;
519 }
520
521 /*
522  * Remove bdi from bdi_list, and ensure that it is no longer visible
523  */
524 static void bdi_remove_from_list(struct backing_dev_info *bdi)
525 {
526         spin_lock_bh(&bdi_lock);
527         list_del_rcu(&bdi->bdi_list);
528         spin_unlock_bh(&bdi_lock);
529
530         synchronize_rcu_expedited();
531 }
532
533 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
534                 const char *fmt, ...)
535 {
536         va_list args;
537         struct device *dev;
538
539         if (bdi->dev)   /* The driver needs to use separate queues per device */
540                 return 0;
541
542         va_start(args, fmt);
543         dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
544         va_end(args);
545         if (IS_ERR(dev))
546                 return PTR_ERR(dev);
547
548         bdi->dev = dev;
549
550         /*
551          * Just start the forker thread for our default backing_dev_info,
552          * and add other bdi's to the list. They will get a thread created
553          * on-demand when they need it.
554          */
555         if (bdi_cap_flush_forker(bdi)) {
556                 struct bdi_writeback *wb = &bdi->wb;
557
558                 wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
559                                                 dev_name(dev));
560                 if (IS_ERR(wb->task))
561                         return PTR_ERR(wb->task);
562         }
563
564         bdi_debug_register(bdi, dev_name(dev));
565         set_bit(BDI_registered, &bdi->state);
566
567         spin_lock_bh(&bdi_lock);
568         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
569         spin_unlock_bh(&bdi_lock);
570
571         trace_writeback_bdi_register(bdi);
572         return 0;
573 }
574 EXPORT_SYMBOL(bdi_register);
575
576 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
577 {
578         return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
579 }
580 EXPORT_SYMBOL(bdi_register_dev);
581
582 /*
583  * Remove bdi from the global list and shutdown any threads we have running
584  */
585 static void bdi_wb_shutdown(struct backing_dev_info *bdi)
586 {
587         struct task_struct *task;
588
589         if (!bdi_cap_writeback_dirty(bdi))
590                 return;
591
592         /*
593          * Make sure nobody finds us on the bdi_list anymore
594          */
595         bdi_remove_from_list(bdi);
596
597         /*
598          * If setup is pending, wait for that to complete first
599          */
600         wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
601                         TASK_UNINTERRUPTIBLE);
602
603         /*
604          * Finally, kill the kernel thread. We don't need to be RCU
605          * safe anymore, since the bdi is gone from visibility.
606          */
607         spin_lock_bh(&bdi->wb_lock);
608         task = bdi->wb.task;
609         bdi->wb.task = NULL;
610         spin_unlock_bh(&bdi->wb_lock);
611
612         if (task)
613                 kthread_stop(task);
614 }
615
616 /*
617  * This bdi is going away now, make sure that no super_blocks point to it
618  */
619 static void bdi_prune_sb(struct backing_dev_info *bdi)
620 {
621         struct super_block *sb;
622
623         spin_lock(&sb_lock);
624         list_for_each_entry(sb, &super_blocks, s_list) {
625                 if (sb->s_bdi == bdi)
626                         sb->s_bdi = &default_backing_dev_info;
627         }
628         spin_unlock(&sb_lock);
629 }
630
631 void bdi_unregister(struct backing_dev_info *bdi)
632 {
633         struct device *dev = bdi->dev;
634
635         if (dev) {
636                 bdi_set_min_ratio(bdi, 0);
637                 trace_writeback_bdi_unregister(bdi);
638                 bdi_prune_sb(bdi);
639                 del_timer_sync(&bdi->wb.wakeup_timer);
640
641                 if (!bdi_cap_flush_forker(bdi))
642                         bdi_wb_shutdown(bdi);
643                 bdi_debug_unregister(bdi);
644
645                 spin_lock_bh(&bdi->wb_lock);
646                 bdi->dev = NULL;
647                 spin_unlock_bh(&bdi->wb_lock);
648
649                 device_unregister(dev);
650         }
651 }
652 EXPORT_SYMBOL(bdi_unregister);
653
654 static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
655 {
656         memset(wb, 0, sizeof(*wb));
657
658         wb->bdi = bdi;
659         wb->last_old_flush = jiffies;
660         INIT_LIST_HEAD(&wb->b_dirty);
661         INIT_LIST_HEAD(&wb->b_io);
662         INIT_LIST_HEAD(&wb->b_more_io);
663         spin_lock_init(&wb->list_lock);
664         setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
665 }
666
667 /*
668  * Initial write bandwidth: 100 MB/s
669  */
670 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
671
672 int bdi_init(struct backing_dev_info *bdi)
673 {
674         int i, err;
675
676         bdi->dev = NULL;
677
678         bdi->min_ratio = 0;
679         bdi->max_ratio = 100;
680         bdi->max_prop_frac = PROP_FRAC_BASE;
681         spin_lock_init(&bdi->wb_lock);
682         INIT_LIST_HEAD(&bdi->bdi_list);
683         INIT_LIST_HEAD(&bdi->work_list);
684
685         bdi_wb_init(&bdi->wb, bdi);
686
687         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
688                 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
689                 if (err)
690                         goto err;
691         }
692
693         bdi->dirty_exceeded = 0;
694
695         bdi->bw_time_stamp = jiffies;
696         bdi->written_stamp = 0;
697
698         bdi->balanced_dirty_ratelimit = INIT_BW;
699         bdi->dirty_ratelimit = INIT_BW;
700         bdi->write_bandwidth = INIT_BW;
701         bdi->avg_write_bandwidth = INIT_BW;
702
703         err = prop_local_init_percpu(&bdi->completions);
704
705         if (err) {
706 err:
707                 while (i--)
708                         percpu_counter_destroy(&bdi->bdi_stat[i]);
709         }
710
711         return err;
712 }
713 EXPORT_SYMBOL(bdi_init);
714
715 void bdi_destroy(struct backing_dev_info *bdi)
716 {
717         int i;
718
719         /*
720          * Splice our entries to the default_backing_dev_info, if this
721          * bdi disappears
722          */
723         if (bdi_has_dirty_io(bdi)) {
724                 struct bdi_writeback *dst = &default_backing_dev_info.wb;
725
726                 bdi_lock_two(&bdi->wb, dst);
727                 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
728                 list_splice(&bdi->wb.b_io, &dst->b_io);
729                 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
730                 spin_unlock(&bdi->wb.list_lock);
731                 spin_unlock(&dst->list_lock);
732         }
733
734         bdi_unregister(bdi);
735
736         /*
737          * If bdi_unregister() had already been called earlier, the
738          * wakeup_timer could still be armed because bdi_prune_sb()
739          * can race with the bdi_wakeup_thread_delayed() calls from
740          * __mark_inode_dirty().
741          */
742         del_timer_sync(&bdi->wb.wakeup_timer);
743
744         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
745                 percpu_counter_destroy(&bdi->bdi_stat[i]);
746
747         prop_local_destroy_percpu(&bdi->completions);
748 }
749 EXPORT_SYMBOL(bdi_destroy);
750
751 /*
752  * For use from filesystems to quickly init and register a bdi associated
753  * with dirty writeback
754  */
755 int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
756                            unsigned int cap)
757 {
758         char tmp[32];
759         int err;
760
761         bdi->name = name;
762         bdi->capabilities = cap;
763         err = bdi_init(bdi);
764         if (err)
765                 return err;
766
767         sprintf(tmp, "%.28s%s", name, "-%d");
768         err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
769         if (err) {
770                 bdi_destroy(bdi);
771                 return err;
772         }
773
774         return 0;
775 }
776 EXPORT_SYMBOL(bdi_setup_and_register);
777
778 static wait_queue_head_t congestion_wqh[2] = {
779                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
780                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
781         };
782 static atomic_t nr_bdi_congested[2];
783
784 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
785 {
786         enum bdi_state bit;
787         wait_queue_head_t *wqh = &congestion_wqh[sync];
788
789         bit = sync ? BDI_sync_congested : BDI_async_congested;
790         if (test_and_clear_bit(bit, &bdi->state))
791                 atomic_dec(&nr_bdi_congested[sync]);
792         smp_mb__after_clear_bit();
793         if (waitqueue_active(wqh))
794                 wake_up(wqh);
795 }
796 EXPORT_SYMBOL(clear_bdi_congested);
797
798 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
799 {
800         enum bdi_state bit;
801
802         bit = sync ? BDI_sync_congested : BDI_async_congested;
803         if (!test_and_set_bit(bit, &bdi->state))
804                 atomic_inc(&nr_bdi_congested[sync]);
805 }
806 EXPORT_SYMBOL(set_bdi_congested);
807
808 /**
809  * congestion_wait - wait for a backing_dev to become uncongested
810  * @sync: SYNC or ASYNC IO
811  * @timeout: timeout in jiffies
812  *
813  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
814  * write congestion.  If no backing_devs are congested then just wait for the
815  * next write to be completed.
816  */
817 long congestion_wait(int sync, long timeout)
818 {
819         long ret;
820         unsigned long start = jiffies;
821         DEFINE_WAIT(wait);
822         wait_queue_head_t *wqh = &congestion_wqh[sync];
823
824         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
825         ret = io_schedule_timeout(timeout);
826         finish_wait(wqh, &wait);
827
828         trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
829                                         jiffies_to_usecs(jiffies - start));
830
831         return ret;
832 }
833 EXPORT_SYMBOL(congestion_wait);
834
835 /**
836  * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
837  * @zone: A zone to check if it is heavily congested
838  * @sync: SYNC or ASYNC IO
839  * @timeout: timeout in jiffies
840  *
841  * In the event of a congested backing_dev (any backing_dev) and the given
842  * @zone has experienced recent congestion, this waits for up to @timeout
843  * jiffies for either a BDI to exit congestion of the given @sync queue
844  * or a write to complete.
845  *
846  * In the absence of zone congestion, cond_resched() is called to yield
847  * the processor if necessary but otherwise does not sleep.
848  *
849  * The return value is 0 if the sleep is for the full timeout. Otherwise,
850  * it is the number of jiffies that were still remaining when the function
851  * returned. return_value == timeout implies the function did not sleep.
852  */
853 long wait_iff_congested(struct zone *zone, int sync, long timeout)
854 {
855         long ret;
856         unsigned long start = jiffies;
857         DEFINE_WAIT(wait);
858         wait_queue_head_t *wqh = &congestion_wqh[sync];
859
860         /*
861          * If there is no congestion, or heavy congestion is not being
862          * encountered in the current zone, yield if necessary instead
863          * of sleeping on the congestion queue
864          */
865         if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
866                         !zone_is_reclaim_congested(zone)) {
867                 cond_resched();
868
869                 /* In case we scheduled, work out time remaining */
870                 ret = timeout - (jiffies - start);
871                 if (ret < 0)
872                         ret = 0;
873
874                 goto out;
875         }
876
877         /* Sleep until uncongested or a write happens */
878         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
879         ret = io_schedule_timeout(timeout);
880         finish_wait(wqh, &wait);
881
882 out:
883         trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
884                                         jiffies_to_usecs(jiffies - start));
885
886         return ret;
887 }
888 EXPORT_SYMBOL(wait_iff_congested);