projects/linux·blob v3.1 · refs

867 lines · 21.8 KiB

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
15static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
16
17struct 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};
23EXPORT_SYMBOL_GPL(default_backing_dev_info);
24
25struct backing_dev_info noop_backing_dev_info = {
26 .name = "noop",
27 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
28};
29EXPORT_SYMBOL_GPL(noop_backing_dev_info);
30
31static 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 */
38DEFINE_SPINLOCK(bdi_lock);
39LIST_HEAD(bdi_list);
40LIST_HEAD(bdi_pending_list);
41
42static struct task_struct *sync_supers_tsk;
43static struct timer_list sync_supers_timer;
44
45static int bdi_sync_supers(void *);
46static void sync_supers_timer_fn(unsigned long);
47
48void 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
63static struct dentry *bdi_debug_root;
64
65static void bdi_debug_init(void)
66{
67 bdi_debug_root = debugfs_create_dir("bdi", NULL);
68}
69
70static 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 "BdiWritten: %10lu kB\n"
101 "BdiWriteBandwidth: %10lu kBps\n"
102 "b_dirty: %10lu\n"
103 "b_io: %10lu\n"
104 "b_more_io: %10lu\n"
105 "bdi_list: %10u\n"
106 "state: %10lx\n",
107 (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
108 (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
109 K(bdi_thresh),
110 K(dirty_thresh),
111 K(background_thresh),
112 (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
113 (unsigned long) K(bdi->write_bandwidth),
114 nr_dirty,
115 nr_io,
116 nr_more_io,
117 !list_empty(&bdi->bdi_list), bdi->state);
118#undef K
119
120 return 0;
121}
122
123static int bdi_debug_stats_open(struct inode *inode, struct file *file)
124{
125 return single_open(file, bdi_debug_stats_show, inode->i_private);
126}
127
128static const struct file_operations bdi_debug_stats_fops = {
129 .open = bdi_debug_stats_open,
130 .read = seq_read,
131 .llseek = seq_lseek,
132 .release = single_release,
133};
134
135static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
136{
137 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
138 bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
139 bdi, &bdi_debug_stats_fops);
140}
141
142static void bdi_debug_unregister(struct backing_dev_info *bdi)
143{
144 debugfs_remove(bdi->debug_stats);
145 debugfs_remove(bdi->debug_dir);
146}
147#else
148static inline void bdi_debug_init(void)
149{
150}
151static inline void bdi_debug_register(struct backing_dev_info *bdi,
152 const char *name)
153{
154}
155static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
156{
157}
158#endif
159
160static ssize_t read_ahead_kb_store(struct device *dev,
161 struct device_attribute *attr,
162 const char *buf, size_t count)
163{
164 struct backing_dev_info *bdi = dev_get_drvdata(dev);
165 char *end;
166 unsigned long read_ahead_kb;
167 ssize_t ret = -EINVAL;
168
169 read_ahead_kb = simple_strtoul(buf, &end, 10);
170 if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
171 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
172 ret = count;
173 }
174 return ret;
175}
176
177#define K(pages) ((pages) << (PAGE_SHIFT - 10))
178
179#define BDI_SHOW(name, expr) \
180static ssize_t name##_show(struct device *dev, \
181 struct device_attribute *attr, char *page) \
182{ \
183 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
184 \
185 return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
186}
187
188BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
189
190static ssize_t min_ratio_store(struct device *dev,
191 struct device_attribute *attr, const char *buf, size_t count)
192{
193 struct backing_dev_info *bdi = dev_get_drvdata(dev);
194 char *end;
195 unsigned int ratio;
196 ssize_t ret = -EINVAL;
197
198 ratio = simple_strtoul(buf, &end, 10);
199 if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
200 ret = bdi_set_min_ratio(bdi, ratio);
201 if (!ret)
202 ret = count;
203 }
204 return ret;
205}
206BDI_SHOW(min_ratio, bdi->min_ratio)
207
208static ssize_t max_ratio_store(struct device *dev,
209 struct device_attribute *attr, const char *buf, size_t count)
210{
211 struct backing_dev_info *bdi = dev_get_drvdata(dev);
212 char *end;
213 unsigned int ratio;
214 ssize_t ret = -EINVAL;
215
216 ratio = simple_strtoul(buf, &end, 10);
217 if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
218 ret = bdi_set_max_ratio(bdi, ratio);
219 if (!ret)
220 ret = count;
221 }
222 return ret;
223}
224BDI_SHOW(max_ratio, bdi->max_ratio)
225
226#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
227
228static struct device_attribute bdi_dev_attrs[] = {
229 __ATTR_RW(read_ahead_kb),
230 __ATTR_RW(min_ratio),
231 __ATTR_RW(max_ratio),
232 __ATTR_NULL,
233};
234
235static __init int bdi_class_init(void)
236{
237 bdi_class = class_create(THIS_MODULE, "bdi");
238 if (IS_ERR(bdi_class))
239 return PTR_ERR(bdi_class);
240
241 bdi_class->dev_attrs = bdi_dev_attrs;
242 bdi_debug_init();
243 return 0;
244}
245postcore_initcall(bdi_class_init);
246
247static int __init default_bdi_init(void)
248{
249 int err;
250
251 sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
252 BUG_ON(IS_ERR(sync_supers_tsk));
253
254 setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
255 bdi_arm_supers_timer();
256
257 err = bdi_init(&default_backing_dev_info);
258 if (!err)
259 bdi_register(&default_backing_dev_info, NULL, "default");
260 err = bdi_init(&noop_backing_dev_info);
261
262 return err;
263}
264subsys_initcall(default_bdi_init);
265
266int bdi_has_dirty_io(struct backing_dev_info *bdi)
267{
268 return wb_has_dirty_io(&bdi->wb);
269}
270
271/*
272 * kupdated() used to do this. We cannot do it from the bdi_forker_thread()
273 * or we risk deadlocking on ->s_umount. The longer term solution would be
274 * to implement sync_supers_bdi() or similar and simply do it from the
275 * bdi writeback thread individually.
276 */
277static int bdi_sync_supers(void *unused)
278{
279 set_user_nice(current, 0);
280
281 while (!kthread_should_stop()) {
282 set_current_state(TASK_INTERRUPTIBLE);
283 schedule();
284
285 /*
286 * Do this periodically, like kupdated() did before.
287 */
288 sync_supers();
289 }
290
291 return 0;
292}
293
294void bdi_arm_supers_timer(void)
295{
296 unsigned long next;
297
298 if (!dirty_writeback_interval)
299 return;
300
301 next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
302 mod_timer(&sync_supers_timer, round_jiffies_up(next));
303}
304
305static void sync_supers_timer_fn(unsigned long unused)
306{
307 wake_up_process(sync_supers_tsk);
308 bdi_arm_supers_timer();
309}
310
311static void wakeup_timer_fn(unsigned long data)
312{
313 struct backing_dev_info *bdi = (struct backing_dev_info *)data;
314
315 spin_lock_bh(&bdi->wb_lock);
316 if (bdi->wb.task) {
317 trace_writeback_wake_thread(bdi);
318 wake_up_process(bdi->wb.task);
319 } else {
320 /*
321 * When bdi tasks are inactive for long time, they are killed.
322 * In this case we have to wake-up the forker thread which
323 * should create and run the bdi thread.
324 */
325 trace_writeback_wake_forker_thread(bdi);
326 wake_up_process(default_backing_dev_info.wb.task);
327 }
328 spin_unlock_bh(&bdi->wb_lock);
329}
330
331/*
332 * This function is used when the first inode for this bdi is marked dirty. It
333 * wakes-up the corresponding bdi thread which should then take care of the
334 * periodic background write-out of dirty inodes. Since the write-out would
335 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
336 * set up a timer which wakes the bdi thread up later.
337 *
338 * Note, we wouldn't bother setting up the timer, but this function is on the
339 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
340 * by delaying the wake-up.
341 */
342void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
343{
344 unsigned long timeout;
345
346 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
347 mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout);
348}
349
350/*
351 * Calculate the longest interval (jiffies) bdi threads are allowed to be
352 * inactive.
353 */
354static unsigned long bdi_longest_inactive(void)
355{
356 unsigned long interval;
357
358 interval = msecs_to_jiffies(dirty_writeback_interval * 10);
359 return max(5UL * 60 * HZ, interval);
360}
361
362/*
363 * Clear pending bit and wakeup anybody waiting for flusher thread creation or
364 * shutdown
365 */
366static void bdi_clear_pending(struct backing_dev_info *bdi)
367{
368 clear_bit(BDI_pending, &bdi->state);
369 smp_mb__after_clear_bit();
370 wake_up_bit(&bdi->state, BDI_pending);
371}
372
373static int bdi_forker_thread(void *ptr)
374{
375 struct bdi_writeback *me = ptr;
376
377 current->flags |= PF_SWAPWRITE;
378 set_freezable();
379
380 /*
381 * Our parent may run at a different priority, just set us to normal
382 */
383 set_user_nice(current, 0);
384
385 for (;;) {
386 struct task_struct *task = NULL;
387 struct backing_dev_info *bdi;
388 enum {
389 NO_ACTION, /* Nothing to do */
390 FORK_THREAD, /* Fork bdi thread */
391 KILL_THREAD, /* Kill inactive bdi thread */
392 } action = NO_ACTION;
393
394 /*
395 * Temporary measure, we want to make sure we don't see
396 * dirty data on the default backing_dev_info
397 */
398 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
399 del_timer(&me->wakeup_timer);
400 wb_do_writeback(me, 0);
401 }
402
403 spin_lock_bh(&bdi_lock);
404 /*
405 * In the following loop we are going to check whether we have
406 * some work to do without any synchronization with tasks
407 * waking us up to do work for them. So we have to set task
408 * state already here so that we don't miss wakeups coming
409 * after we verify some condition.
410 */
411 set_current_state(TASK_INTERRUPTIBLE);
412
413 list_for_each_entry(bdi, &bdi_list, bdi_list) {
414 bool have_dirty_io;
415
416 if (!bdi_cap_writeback_dirty(bdi) ||
417 bdi_cap_flush_forker(bdi))
418 continue;
419
420 WARN(!test_bit(BDI_registered, &bdi->state),
421 "bdi %p/%s is not registered!\n", bdi, bdi->name);
422
423 have_dirty_io = !list_empty(&bdi->work_list) ||
424 wb_has_dirty_io(&bdi->wb);
425
426 /*
427 * If the bdi has work to do, but the thread does not
428 * exist - create it.
429 */
430 if (!bdi->wb.task && have_dirty_io) {
431 /*
432 * Set the pending bit - if someone will try to
433 * unregister this bdi - it'll wait on this bit.
434 */
435 set_bit(BDI_pending, &bdi->state);
436 action = FORK_THREAD;
437 break;
438 }
439
440 spin_lock(&bdi->wb_lock);
441
442 /*
443 * If there is no work to do and the bdi thread was
444 * inactive long enough - kill it. The wb_lock is taken
445 * to make sure no-one adds more work to this bdi and
446 * wakes the bdi thread up.
447 */
448 if (bdi->wb.task && !have_dirty_io &&
449 time_after(jiffies, bdi->wb.last_active +
450 bdi_longest_inactive())) {
451 task = bdi->wb.task;
452 bdi->wb.task = NULL;
453 spin_unlock(&bdi->wb_lock);
454 set_bit(BDI_pending, &bdi->state);
455 action = KILL_THREAD;
456 break;
457 }
458 spin_unlock(&bdi->wb_lock);
459 }
460 spin_unlock_bh(&bdi_lock);
461
462 /* Keep working if default bdi still has things to do */
463 if (!list_empty(&me->bdi->work_list))
464 __set_current_state(TASK_RUNNING);
465
466 switch (action) {
467 case FORK_THREAD:
468 __set_current_state(TASK_RUNNING);
469 task = kthread_create(bdi_writeback_thread, &bdi->wb,
470 "flush-%s", dev_name(bdi->dev));
471 if (IS_ERR(task)) {
472 /*
473 * If thread creation fails, force writeout of
474 * the bdi from the thread. Hopefully 1024 is
475 * large enough for efficient IO.
476 */
477 writeback_inodes_wb(&bdi->wb, 1024);
478 } else {
479 /*
480 * The spinlock makes sure we do not lose
481 * wake-ups when racing with 'bdi_queue_work()'.
482 * And as soon as the bdi thread is visible, we
483 * can start it.
484 */
485 spin_lock_bh(&bdi->wb_lock);
486 bdi->wb.task = task;
487 spin_unlock_bh(&bdi->wb_lock);
488 wake_up_process(task);
489 }
490 bdi_clear_pending(bdi);
491 break;
492
493 case KILL_THREAD:
494 __set_current_state(TASK_RUNNING);
495 kthread_stop(task);
496 bdi_clear_pending(bdi);
497 break;
498
499 case NO_ACTION:
500 if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
501 /*
502 * There are no dirty data. The only thing we
503 * should now care about is checking for
504 * inactive bdi threads and killing them. Thus,
505 * let's sleep for longer time, save energy and
506 * be friendly for battery-driven devices.
507 */
508 schedule_timeout(bdi_longest_inactive());
509 else
510 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
511 try_to_freeze();
512 break;
513 }
514 }
515
516 return 0;
517}
518
519/*
520 * Remove bdi from bdi_list, and ensure that it is no longer visible
521 */
522static void bdi_remove_from_list(struct backing_dev_info *bdi)
523{
524 spin_lock_bh(&bdi_lock);
525 list_del_rcu(&bdi->bdi_list);
526 spin_unlock_bh(&bdi_lock);
527
528 synchronize_rcu_expedited();
529}
530
531int bdi_register(struct backing_dev_info *bdi, struct device *parent,
532 const char *fmt, ...)
533{
534 va_list args;
535 struct device *dev;
536
537 if (bdi->dev) /* The driver needs to use separate queues per device */
538 return 0;
539
540 va_start(args, fmt);
541 dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
542 va_end(args);
543 if (IS_ERR(dev))
544 return PTR_ERR(dev);
545
546 bdi->dev = dev;
547
548 /*
549 * Just start the forker thread for our default backing_dev_info,
550 * and add other bdi's to the list. They will get a thread created
551 * on-demand when they need it.
552 */
553 if (bdi_cap_flush_forker(bdi)) {
554 struct bdi_writeback *wb = &bdi->wb;
555
556 wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
557 dev_name(dev));
558 if (IS_ERR(wb->task))
559 return PTR_ERR(wb->task);
560 }
561
562 bdi_debug_register(bdi, dev_name(dev));
563 set_bit(BDI_registered, &bdi->state);
564
565 spin_lock_bh(&bdi_lock);
566 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
567 spin_unlock_bh(&bdi_lock);
568
569 trace_writeback_bdi_register(bdi);
570 return 0;
571}
572EXPORT_SYMBOL(bdi_register);
573
574int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
575{
576 return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
577}
578EXPORT_SYMBOL(bdi_register_dev);
579
580/*
581 * Remove bdi from the global list and shutdown any threads we have running
582 */
583static void bdi_wb_shutdown(struct backing_dev_info *bdi)
584{
585 if (!bdi_cap_writeback_dirty(bdi))
586 return;
587
588 /*
589 * Make sure nobody finds us on the bdi_list anymore
590 */
591 bdi_remove_from_list(bdi);
592
593 /*
594 * If setup is pending, wait for that to complete first
595 */
596 wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
597 TASK_UNINTERRUPTIBLE);
598
599 /*
600 * Finally, kill the kernel thread. We don't need to be RCU
601 * safe anymore, since the bdi is gone from visibility. Force
602 * unfreeze of the thread before calling kthread_stop(), otherwise
603 * it would never exet if it is currently stuck in the refrigerator.
604 */
605 if (bdi->wb.task) {
606 thaw_process(bdi->wb.task);
607 kthread_stop(bdi->wb.task);
608 }
609}
610
611/*
612 * This bdi is going away now, make sure that no super_blocks point to it
613 */
614static void bdi_prune_sb(struct backing_dev_info *bdi)
615{
616 struct super_block *sb;
617
618 spin_lock(&sb_lock);
619 list_for_each_entry(sb, &super_blocks, s_list) {
620 if (sb->s_bdi == bdi)
621 sb->s_bdi = &default_backing_dev_info;
622 }
623 spin_unlock(&sb_lock);
624}
625
626void bdi_unregister(struct backing_dev_info *bdi)
627{
628 if (bdi->dev) {
629 bdi_set_min_ratio(bdi, 0);
630 trace_writeback_bdi_unregister(bdi);
631 bdi_prune_sb(bdi);
632 del_timer_sync(&bdi->wb.wakeup_timer);
633
634 if (!bdi_cap_flush_forker(bdi))
635 bdi_wb_shutdown(bdi);
636 bdi_debug_unregister(bdi);
637 device_unregister(bdi->dev);
638 bdi->dev = NULL;
639 }
640}
641EXPORT_SYMBOL(bdi_unregister);
642
643static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
644{
645 memset(wb, 0, sizeof(*wb));
646
647 wb->bdi = bdi;
648 wb->last_old_flush = jiffies;
649 INIT_LIST_HEAD(&wb->b_dirty);
650 INIT_LIST_HEAD(&wb->b_io);
651 INIT_LIST_HEAD(&wb->b_more_io);
652 spin_lock_init(&wb->list_lock);
653 setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
654}
655
656/*
657 * Initial write bandwidth: 100 MB/s
658 */
659#define INIT_BW (100 << (20 - PAGE_SHIFT))
660
661int bdi_init(struct backing_dev_info *bdi)
662{
663 int i, err;
664
665 bdi->dev = NULL;
666
667 bdi->min_ratio = 0;
668 bdi->max_ratio = 100;
669 bdi->max_prop_frac = PROP_FRAC_BASE;
670 spin_lock_init(&bdi->wb_lock);
671 INIT_LIST_HEAD(&bdi->bdi_list);
672 INIT_LIST_HEAD(&bdi->work_list);
673
674 bdi_wb_init(&bdi->wb, bdi);
675
676 for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
677 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
678 if (err)
679 goto err;
680 }
681
682 bdi->dirty_exceeded = 0;
683
684 bdi->bw_time_stamp = jiffies;
685 bdi->written_stamp = 0;
686
687 bdi->write_bandwidth = INIT_BW;
688 bdi->avg_write_bandwidth = INIT_BW;
689
690 err = prop_local_init_percpu(&bdi->completions);
691
692 if (err) {
693err:
694 while (i--)
695 percpu_counter_destroy(&bdi->bdi_stat[i]);
696 }
697
698 return err;
699}
700EXPORT_SYMBOL(bdi_init);
701
702void bdi_destroy(struct backing_dev_info *bdi)
703{
704 int i;
705
706 /*
707 * Splice our entries to the default_backing_dev_info, if this
708 * bdi disappears
709 */
710 if (bdi_has_dirty_io(bdi)) {
711 struct bdi_writeback *dst = &default_backing_dev_info.wb;
712
713 bdi_lock_two(&bdi->wb, dst);
714 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
715 list_splice(&bdi->wb.b_io, &dst->b_io);
716 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
717 spin_unlock(&bdi->wb.list_lock);
718 spin_unlock(&dst->list_lock);
719 }
720
721 bdi_unregister(bdi);
722
723 for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
724 percpu_counter_destroy(&bdi->bdi_stat[i]);
725
726 prop_local_destroy_percpu(&bdi->completions);
727}
728EXPORT_SYMBOL(bdi_destroy);
729
730/*
731 * For use from filesystems to quickly init and register a bdi associated
732 * with dirty writeback
733 */
734int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
735 unsigned int cap)
736{
737 char tmp[32];
738 int err;
739
740 bdi->name = name;
741 bdi->capabilities = cap;
742 err = bdi_init(bdi);
743 if (err)
744 return err;
745
746 sprintf(tmp, "%.28s%s", name, "-%d");
747 err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
748 if (err) {
749 bdi_destroy(bdi);
750 return err;
751 }
752
753 return 0;
754}
755EXPORT_SYMBOL(bdi_setup_and_register);
756
757static wait_queue_head_t congestion_wqh[2] = {
758 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
759 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
760 };
761static atomic_t nr_bdi_congested[2];
762
763void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
764{
765 enum bdi_state bit;
766 wait_queue_head_t *wqh = &congestion_wqh[sync];
767
768 bit = sync ? BDI_sync_congested : BDI_async_congested;
769 if (test_and_clear_bit(bit, &bdi->state))
770 atomic_dec(&nr_bdi_congested[sync]);
771 smp_mb__after_clear_bit();
772 if (waitqueue_active(wqh))
773 wake_up(wqh);
774}
775EXPORT_SYMBOL(clear_bdi_congested);
776
777void set_bdi_congested(struct backing_dev_info *bdi, int sync)
778{
779 enum bdi_state bit;
780
781 bit = sync ? BDI_sync_congested : BDI_async_congested;
782 if (!test_and_set_bit(bit, &bdi->state))
783 atomic_inc(&nr_bdi_congested[sync]);
784}
785EXPORT_SYMBOL(set_bdi_congested);
786
787/**
788 * congestion_wait - wait for a backing_dev to become uncongested
789 * @sync: SYNC or ASYNC IO
790 * @timeout: timeout in jiffies
791 *
792 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
793 * write congestion. If no backing_devs are congested then just wait for the
794 * next write to be completed.
795 */
796long congestion_wait(int sync, long timeout)
797{
798 long ret;
799 unsigned long start = jiffies;
800 DEFINE_WAIT(wait);
801 wait_queue_head_t *wqh = &congestion_wqh[sync];
802
803 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
804 ret = io_schedule_timeout(timeout);
805 finish_wait(wqh, &wait);
806
807 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
808 jiffies_to_usecs(jiffies - start));
809
810 return ret;
811}
812EXPORT_SYMBOL(congestion_wait);
813
814/**
815 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
816 * @zone: A zone to check if it is heavily congested
817 * @sync: SYNC or ASYNC IO
818 * @timeout: timeout in jiffies
819 *
820 * In the event of a congested backing_dev (any backing_dev) and the given
821 * @zone has experienced recent congestion, this waits for up to @timeout
822 * jiffies for either a BDI to exit congestion of the given @sync queue
823 * or a write to complete.
824 *
825 * In the absence of zone congestion, cond_resched() is called to yield
826 * the processor if necessary but otherwise does not sleep.
827 *
828 * The return value is 0 if the sleep is for the full timeout. Otherwise,
829 * it is the number of jiffies that were still remaining when the function
830 * returned. return_value == timeout implies the function did not sleep.
831 */
832long wait_iff_congested(struct zone *zone, int sync, long timeout)
833{
834 long ret;
835 unsigned long start = jiffies;
836 DEFINE_WAIT(wait);
837 wait_queue_head_t *wqh = &congestion_wqh[sync];
838
839 /*
840 * If there is no congestion, or heavy congestion is not being
841 * encountered in the current zone, yield if necessary instead
842 * of sleeping on the congestion queue
843 */
844 if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
845 !zone_is_reclaim_congested(zone)) {
846 cond_resched();
847
848 /* In case we scheduled, work out time remaining */
849 ret = timeout - (jiffies - start);
850 if (ret < 0)
851 ret = 0;
852
853 goto out;
854 }
855
856 /* Sleep until uncongested or a write happens */
857 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
858 ret = io_schedule_timeout(timeout);
859 finish_wait(wqh, &wait);
860
861out:
862 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
863 jiffies_to_usecs(jiffies - start));
864
865 return ret;
866}
867EXPORT_SYMBOL(wait_iff_congested);