projects/linux·blob v3.0 · refs

832 lines · 20.8 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
48#ifdef CONFIG_DEBUG_FS
49#include <linux/debugfs.h>
50#include <linux/seq_file.h>
51
52static struct dentry *bdi_debug_root;
53
54static void bdi_debug_init(void)
55{
56 bdi_debug_root = debugfs_create_dir("bdi", NULL);
57}
58
59static int bdi_debug_stats_show(struct seq_file *m, void *v)
60{
61 struct backing_dev_info *bdi = m->private;
62 struct bdi_writeback *wb = &bdi->wb;
63 unsigned long background_thresh;
64 unsigned long dirty_thresh;
65 unsigned long bdi_thresh;
66 unsigned long nr_dirty, nr_io, nr_more_io;
67 struct inode *inode;
68
69 nr_dirty = nr_io = nr_more_io = 0;
70 spin_lock(&inode_wb_list_lock);
71 list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
72 nr_dirty++;
73 list_for_each_entry(inode, &wb->b_io, i_wb_list)
74 nr_io++;
75 list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
76 nr_more_io++;
77 spin_unlock(&inode_wb_list_lock);
78
79 global_dirty_limits(&background_thresh, &dirty_thresh);
80 bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
81
82#define K(x) ((x) << (PAGE_SHIFT - 10))
83 seq_printf(m,
84 "BdiWriteback: %8lu kB\n"
85 "BdiReclaimable: %8lu kB\n"
86 "BdiDirtyThresh: %8lu kB\n"
87 "DirtyThresh: %8lu kB\n"
88 "BackgroundThresh: %8lu kB\n"
89 "b_dirty: %8lu\n"
90 "b_io: %8lu\n"
91 "b_more_io: %8lu\n"
92 "bdi_list: %8u\n"
93 "state: %8lx\n",
94 (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
95 (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
96 K(bdi_thresh), K(dirty_thresh),
97 K(background_thresh), nr_dirty, nr_io, nr_more_io,
98 !list_empty(&bdi->bdi_list), bdi->state);
99#undef K
100
101 return 0;
102}
103
104static int bdi_debug_stats_open(struct inode *inode, struct file *file)
105{
106 return single_open(file, bdi_debug_stats_show, inode->i_private);
107}
108
109static const struct file_operations bdi_debug_stats_fops = {
110 .open = bdi_debug_stats_open,
111 .read = seq_read,
112 .llseek = seq_lseek,
113 .release = single_release,
114};
115
116static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
117{
118 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
119 bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
120 bdi, &bdi_debug_stats_fops);
121}
122
123static void bdi_debug_unregister(struct backing_dev_info *bdi)
124{
125 debugfs_remove(bdi->debug_stats);
126 debugfs_remove(bdi->debug_dir);
127}
128#else
129static inline void bdi_debug_init(void)
130{
131}
132static inline void bdi_debug_register(struct backing_dev_info *bdi,
133 const char *name)
134{
135}
136static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
137{
138}
139#endif
140
141static ssize_t read_ahead_kb_store(struct device *dev,
142 struct device_attribute *attr,
143 const char *buf, size_t count)
144{
145 struct backing_dev_info *bdi = dev_get_drvdata(dev);
146 char *end;
147 unsigned long read_ahead_kb;
148 ssize_t ret = -EINVAL;
149
150 read_ahead_kb = simple_strtoul(buf, &end, 10);
151 if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
152 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
153 ret = count;
154 }
155 return ret;
156}
157
158#define K(pages) ((pages) << (PAGE_SHIFT - 10))
159
160#define BDI_SHOW(name, expr) \
161static ssize_t name##_show(struct device *dev, \
162 struct device_attribute *attr, char *page) \
163{ \
164 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
165 \
166 return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
167}
168
169BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
170
171static ssize_t min_ratio_store(struct device *dev,
172 struct device_attribute *attr, const char *buf, size_t count)
173{
174 struct backing_dev_info *bdi = dev_get_drvdata(dev);
175 char *end;
176 unsigned int ratio;
177 ssize_t ret = -EINVAL;
178
179 ratio = simple_strtoul(buf, &end, 10);
180 if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
181 ret = bdi_set_min_ratio(bdi, ratio);
182 if (!ret)
183 ret = count;
184 }
185 return ret;
186}
187BDI_SHOW(min_ratio, bdi->min_ratio)
188
189static ssize_t max_ratio_store(struct device *dev,
190 struct device_attribute *attr, const char *buf, size_t count)
191{
192 struct backing_dev_info *bdi = dev_get_drvdata(dev);
193 char *end;
194 unsigned int ratio;
195 ssize_t ret = -EINVAL;
196
197 ratio = simple_strtoul(buf, &end, 10);
198 if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
199 ret = bdi_set_max_ratio(bdi, ratio);
200 if (!ret)
201 ret = count;
202 }
203 return ret;
204}
205BDI_SHOW(max_ratio, bdi->max_ratio)
206
207#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
208
209static struct device_attribute bdi_dev_attrs[] = {
210 __ATTR_RW(read_ahead_kb),
211 __ATTR_RW(min_ratio),
212 __ATTR_RW(max_ratio),
213 __ATTR_NULL,
214};
215
216static __init int bdi_class_init(void)
217{
218 bdi_class = class_create(THIS_MODULE, "bdi");
219 if (IS_ERR(bdi_class))
220 return PTR_ERR(bdi_class);
221
222 bdi_class->dev_attrs = bdi_dev_attrs;
223 bdi_debug_init();
224 return 0;
225}
226postcore_initcall(bdi_class_init);
227
228static int __init default_bdi_init(void)
229{
230 int err;
231
232 sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
233 BUG_ON(IS_ERR(sync_supers_tsk));
234
235 setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
236 bdi_arm_supers_timer();
237
238 err = bdi_init(&default_backing_dev_info);
239 if (!err)
240 bdi_register(&default_backing_dev_info, NULL, "default");
241 err = bdi_init(&noop_backing_dev_info);
242
243 return err;
244}
245subsys_initcall(default_bdi_init);
246
247int bdi_has_dirty_io(struct backing_dev_info *bdi)
248{
249 return wb_has_dirty_io(&bdi->wb);
250}
251
252static void bdi_flush_io(struct backing_dev_info *bdi)
253{
254 struct writeback_control wbc = {
255 .sync_mode = WB_SYNC_NONE,
256 .older_than_this = NULL,
257 .range_cyclic = 1,
258 .nr_to_write = 1024,
259 };
260
261 writeback_inodes_wb(&bdi->wb, &wbc);
262}
263
264/*
265 * kupdated() used to do this. We cannot do it from the bdi_forker_thread()
266 * or we risk deadlocking on ->s_umount. The longer term solution would be
267 * to implement sync_supers_bdi() or similar and simply do it from the
268 * bdi writeback thread individually.
269 */
270static int bdi_sync_supers(void *unused)
271{
272 set_user_nice(current, 0);
273
274 while (!kthread_should_stop()) {
275 set_current_state(TASK_INTERRUPTIBLE);
276 schedule();
277
278 /*
279 * Do this periodically, like kupdated() did before.
280 */
281 sync_supers();
282 }
283
284 return 0;
285}
286
287void bdi_arm_supers_timer(void)
288{
289 unsigned long next;
290
291 if (!dirty_writeback_interval)
292 return;
293
294 next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
295 mod_timer(&sync_supers_timer, round_jiffies_up(next));
296}
297
298static void sync_supers_timer_fn(unsigned long unused)
299{
300 wake_up_process(sync_supers_tsk);
301 bdi_arm_supers_timer();
302}
303
304static void wakeup_timer_fn(unsigned long data)
305{
306 struct backing_dev_info *bdi = (struct backing_dev_info *)data;
307
308 spin_lock_bh(&bdi->wb_lock);
309 if (bdi->wb.task) {
310 trace_writeback_wake_thread(bdi);
311 wake_up_process(bdi->wb.task);
312 } else {
313 /*
314 * When bdi tasks are inactive for long time, they are killed.
315 * In this case we have to wake-up the forker thread which
316 * should create and run the bdi thread.
317 */
318 trace_writeback_wake_forker_thread(bdi);
319 wake_up_process(default_backing_dev_info.wb.task);
320 }
321 spin_unlock_bh(&bdi->wb_lock);
322}
323
324/*
325 * This function is used when the first inode for this bdi is marked dirty. It
326 * wakes-up the corresponding bdi thread which should then take care of the
327 * periodic background write-out of dirty inodes. Since the write-out would
328 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
329 * set up a timer which wakes the bdi thread up later.
330 *
331 * Note, we wouldn't bother setting up the timer, but this function is on the
332 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
333 * by delaying the wake-up.
334 */
335void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
336{
337 unsigned long timeout;
338
339 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
340 mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout);
341}
342
343/*
344 * Calculate the longest interval (jiffies) bdi threads are allowed to be
345 * inactive.
346 */
347static unsigned long bdi_longest_inactive(void)
348{
349 unsigned long interval;
350
351 interval = msecs_to_jiffies(dirty_writeback_interval * 10);
352 return max(5UL * 60 * HZ, interval);
353}
354
355static int bdi_forker_thread(void *ptr)
356{
357 struct bdi_writeback *me = ptr;
358
359 current->flags |= PF_SWAPWRITE;
360 set_freezable();
361
362 /*
363 * Our parent may run at a different priority, just set us to normal
364 */
365 set_user_nice(current, 0);
366
367 for (;;) {
368 struct task_struct *task = NULL;
369 struct backing_dev_info *bdi;
370 enum {
371 NO_ACTION, /* Nothing to do */
372 FORK_THREAD, /* Fork bdi thread */
373 KILL_THREAD, /* Kill inactive bdi thread */
374 } action = NO_ACTION;
375
376 /*
377 * Temporary measure, we want to make sure we don't see
378 * dirty data on the default backing_dev_info
379 */
380 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
381 del_timer(&me->wakeup_timer);
382 wb_do_writeback(me, 0);
383 }
384
385 spin_lock_bh(&bdi_lock);
386 set_current_state(TASK_INTERRUPTIBLE);
387
388 list_for_each_entry(bdi, &bdi_list, bdi_list) {
389 bool have_dirty_io;
390
391 if (!bdi_cap_writeback_dirty(bdi) ||
392 bdi_cap_flush_forker(bdi))
393 continue;
394
395 WARN(!test_bit(BDI_registered, &bdi->state),
396 "bdi %p/%s is not registered!\n", bdi, bdi->name);
397
398 have_dirty_io = !list_empty(&bdi->work_list) ||
399 wb_has_dirty_io(&bdi->wb);
400
401 /*
402 * If the bdi has work to do, but the thread does not
403 * exist - create it.
404 */
405 if (!bdi->wb.task && have_dirty_io) {
406 /*
407 * Set the pending bit - if someone will try to
408 * unregister this bdi - it'll wait on this bit.
409 */
410 set_bit(BDI_pending, &bdi->state);
411 action = FORK_THREAD;
412 break;
413 }
414
415 spin_lock(&bdi->wb_lock);
416
417 /*
418 * If there is no work to do and the bdi thread was
419 * inactive long enough - kill it. The wb_lock is taken
420 * to make sure no-one adds more work to this bdi and
421 * wakes the bdi thread up.
422 */
423 if (bdi->wb.task && !have_dirty_io &&
424 time_after(jiffies, bdi->wb.last_active +
425 bdi_longest_inactive())) {
426 task = bdi->wb.task;
427 bdi->wb.task = NULL;
428 spin_unlock(&bdi->wb_lock);
429 set_bit(BDI_pending, &bdi->state);
430 action = KILL_THREAD;
431 break;
432 }
433 spin_unlock(&bdi->wb_lock);
434 }
435 spin_unlock_bh(&bdi_lock);
436
437 /* Keep working if default bdi still has things to do */
438 if (!list_empty(&me->bdi->work_list))
439 __set_current_state(TASK_RUNNING);
440
441 switch (action) {
442 case FORK_THREAD:
443 __set_current_state(TASK_RUNNING);
444 task = kthread_create(bdi_writeback_thread, &bdi->wb,
445 "flush-%s", dev_name(bdi->dev));
446 if (IS_ERR(task)) {
447 /*
448 * If thread creation fails, force writeout of
449 * the bdi from the thread.
450 */
451 bdi_flush_io(bdi);
452 } else {
453 /*
454 * The spinlock makes sure we do not lose
455 * wake-ups when racing with 'bdi_queue_work()'.
456 * And as soon as the bdi thread is visible, we
457 * can start it.
458 */
459 spin_lock_bh(&bdi->wb_lock);
460 bdi->wb.task = task;
461 spin_unlock_bh(&bdi->wb_lock);
462 wake_up_process(task);
463 }
464 break;
465
466 case KILL_THREAD:
467 __set_current_state(TASK_RUNNING);
468 kthread_stop(task);
469 break;
470
471 case NO_ACTION:
472 if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
473 /*
474 * There are no dirty data. The only thing we
475 * should now care about is checking for
476 * inactive bdi threads and killing them. Thus,
477 * let's sleep for longer time, save energy and
478 * be friendly for battery-driven devices.
479 */
480 schedule_timeout(bdi_longest_inactive());
481 else
482 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
483 try_to_freeze();
484 /* Back to the main loop */
485 continue;
486 }
487
488 /*
489 * Clear pending bit and wakeup anybody waiting to tear us down.
490 */
491 clear_bit(BDI_pending, &bdi->state);
492 smp_mb__after_clear_bit();
493 wake_up_bit(&bdi->state, BDI_pending);
494 }
495
496 return 0;
497}
498
499/*
500 * Remove bdi from bdi_list, and ensure that it is no longer visible
501 */
502static void bdi_remove_from_list(struct backing_dev_info *bdi)
503{
504 spin_lock_bh(&bdi_lock);
505 list_del_rcu(&bdi->bdi_list);
506 spin_unlock_bh(&bdi_lock);
507
508 synchronize_rcu();
509}
510
511int bdi_register(struct backing_dev_info *bdi, struct device *parent,
512 const char *fmt, ...)
513{
514 va_list args;
515 struct device *dev;
516
517 if (bdi->dev) /* The driver needs to use separate queues per device */
518 return 0;
519
520 va_start(args, fmt);
521 dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
522 va_end(args);
523 if (IS_ERR(dev))
524 return PTR_ERR(dev);
525
526 bdi->dev = dev;
527
528 /*
529 * Just start the forker thread for our default backing_dev_info,
530 * and add other bdi's to the list. They will get a thread created
531 * on-demand when they need it.
532 */
533 if (bdi_cap_flush_forker(bdi)) {
534 struct bdi_writeback *wb = &bdi->wb;
535
536 wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
537 dev_name(dev));
538 if (IS_ERR(wb->task))
539 return PTR_ERR(wb->task);
540 }
541
542 bdi_debug_register(bdi, dev_name(dev));
543 set_bit(BDI_registered, &bdi->state);
544
545 spin_lock_bh(&bdi_lock);
546 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
547 spin_unlock_bh(&bdi_lock);
548
549 trace_writeback_bdi_register(bdi);
550 return 0;
551}
552EXPORT_SYMBOL(bdi_register);
553
554int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
555{
556 return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
557}
558EXPORT_SYMBOL(bdi_register_dev);
559
560/*
561 * Remove bdi from the global list and shutdown any threads we have running
562 */
563static void bdi_wb_shutdown(struct backing_dev_info *bdi)
564{
565 if (!bdi_cap_writeback_dirty(bdi))
566 return;
567
568 /*
569 * Make sure nobody finds us on the bdi_list anymore
570 */
571 bdi_remove_from_list(bdi);
572
573 /*
574 * If setup is pending, wait for that to complete first
575 */
576 wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
577 TASK_UNINTERRUPTIBLE);
578
579 /*
580 * Finally, kill the kernel thread. We don't need to be RCU
581 * safe anymore, since the bdi is gone from visibility. Force
582 * unfreeze of the thread before calling kthread_stop(), otherwise
583 * it would never exet if it is currently stuck in the refrigerator.
584 */
585 if (bdi->wb.task) {
586 thaw_process(bdi->wb.task);
587 kthread_stop(bdi->wb.task);
588 }
589}
590
591/*
592 * This bdi is going away now, make sure that no super_blocks point to it
593 */
594static void bdi_prune_sb(struct backing_dev_info *bdi)
595{
596 struct super_block *sb;
597
598 spin_lock(&sb_lock);
599 list_for_each_entry(sb, &super_blocks, s_list) {
600 if (sb->s_bdi == bdi)
601 sb->s_bdi = &default_backing_dev_info;
602 }
603 spin_unlock(&sb_lock);
604}
605
606void bdi_unregister(struct backing_dev_info *bdi)
607{
608 if (bdi->dev) {
609 trace_writeback_bdi_unregister(bdi);
610 bdi_prune_sb(bdi);
611 del_timer_sync(&bdi->wb.wakeup_timer);
612
613 if (!bdi_cap_flush_forker(bdi))
614 bdi_wb_shutdown(bdi);
615 bdi_debug_unregister(bdi);
616 device_unregister(bdi->dev);
617 bdi->dev = NULL;
618 }
619}
620EXPORT_SYMBOL(bdi_unregister);
621
622static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
623{
624 memset(wb, 0, sizeof(*wb));
625
626 wb->bdi = bdi;
627 wb->last_old_flush = jiffies;
628 INIT_LIST_HEAD(&wb->b_dirty);
629 INIT_LIST_HEAD(&wb->b_io);
630 INIT_LIST_HEAD(&wb->b_more_io);
631 setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
632}
633
634int bdi_init(struct backing_dev_info *bdi)
635{
636 int i, err;
637
638 bdi->dev = NULL;
639
640 bdi->min_ratio = 0;
641 bdi->max_ratio = 100;
642 bdi->max_prop_frac = PROP_FRAC_BASE;
643 spin_lock_init(&bdi->wb_lock);
644 INIT_LIST_HEAD(&bdi->bdi_list);
645 INIT_LIST_HEAD(&bdi->work_list);
646
647 bdi_wb_init(&bdi->wb, bdi);
648
649 for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
650 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
651 if (err)
652 goto err;
653 }
654
655 bdi->dirty_exceeded = 0;
656 err = prop_local_init_percpu(&bdi->completions);
657
658 if (err) {
659err:
660 while (i--)
661 percpu_counter_destroy(&bdi->bdi_stat[i]);
662 }
663
664 return err;
665}
666EXPORT_SYMBOL(bdi_init);
667
668void bdi_destroy(struct backing_dev_info *bdi)
669{
670 int i;
671
672 /*
673 * Splice our entries to the default_backing_dev_info, if this
674 * bdi disappears
675 */
676 if (bdi_has_dirty_io(bdi)) {
677 struct bdi_writeback *dst = &default_backing_dev_info.wb;
678
679 spin_lock(&inode_wb_list_lock);
680 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
681 list_splice(&bdi->wb.b_io, &dst->b_io);
682 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
683 spin_unlock(&inode_wb_list_lock);
684 }
685
686 bdi_unregister(bdi);
687
688 for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
689 percpu_counter_destroy(&bdi->bdi_stat[i]);
690
691 prop_local_destroy_percpu(&bdi->completions);
692}
693EXPORT_SYMBOL(bdi_destroy);
694
695/*
696 * For use from filesystems to quickly init and register a bdi associated
697 * with dirty writeback
698 */
699int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
700 unsigned int cap)
701{
702 char tmp[32];
703 int err;
704
705 bdi->name = name;
706 bdi->capabilities = cap;
707 err = bdi_init(bdi);
708 if (err)
709 return err;
710
711 sprintf(tmp, "%.28s%s", name, "-%d");
712 err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
713 if (err) {
714 bdi_destroy(bdi);
715 return err;
716 }
717
718 return 0;
719}
720EXPORT_SYMBOL(bdi_setup_and_register);
721
722static wait_queue_head_t congestion_wqh[2] = {
723 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
724 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
725 };
726static atomic_t nr_bdi_congested[2];
727
728void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
729{
730 enum bdi_state bit;
731 wait_queue_head_t *wqh = &congestion_wqh[sync];
732
733 bit = sync ? BDI_sync_congested : BDI_async_congested;
734 if (test_and_clear_bit(bit, &bdi->state))
735 atomic_dec(&nr_bdi_congested[sync]);
736 smp_mb__after_clear_bit();
737 if (waitqueue_active(wqh))
738 wake_up(wqh);
739}
740EXPORT_SYMBOL(clear_bdi_congested);
741
742void set_bdi_congested(struct backing_dev_info *bdi, int sync)
743{
744 enum bdi_state bit;
745
746 bit = sync ? BDI_sync_congested : BDI_async_congested;
747 if (!test_and_set_bit(bit, &bdi->state))
748 atomic_inc(&nr_bdi_congested[sync]);
749}
750EXPORT_SYMBOL(set_bdi_congested);
751
752/**
753 * congestion_wait - wait for a backing_dev to become uncongested
754 * @sync: SYNC or ASYNC IO
755 * @timeout: timeout in jiffies
756 *
757 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
758 * write congestion. If no backing_devs are congested then just wait for the
759 * next write to be completed.
760 */
761long congestion_wait(int sync, long timeout)
762{
763 long ret;
764 unsigned long start = jiffies;
765 DEFINE_WAIT(wait);
766 wait_queue_head_t *wqh = &congestion_wqh[sync];
767
768 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
769 ret = io_schedule_timeout(timeout);
770 finish_wait(wqh, &wait);
771
772 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
773 jiffies_to_usecs(jiffies - start));
774
775 return ret;
776}
777EXPORT_SYMBOL(congestion_wait);
778
779/**
780 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
781 * @zone: A zone to check if it is heavily congested
782 * @sync: SYNC or ASYNC IO
783 * @timeout: timeout in jiffies
784 *
785 * In the event of a congested backing_dev (any backing_dev) and the given
786 * @zone has experienced recent congestion, this waits for up to @timeout
787 * jiffies for either a BDI to exit congestion of the given @sync queue
788 * or a write to complete.
789 *
790 * In the absence of zone congestion, cond_resched() is called to yield
791 * the processor if necessary but otherwise does not sleep.
792 *
793 * The return value is 0 if the sleep is for the full timeout. Otherwise,
794 * it is the number of jiffies that were still remaining when the function
795 * returned. return_value == timeout implies the function did not sleep.
796 */
797long wait_iff_congested(struct zone *zone, int sync, long timeout)
798{
799 long ret;
800 unsigned long start = jiffies;
801 DEFINE_WAIT(wait);
802 wait_queue_head_t *wqh = &congestion_wqh[sync];
803
804 /*
805 * If there is no congestion, or heavy congestion is not being
806 * encountered in the current zone, yield if necessary instead
807 * of sleeping on the congestion queue
808 */
809 if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
810 !zone_is_reclaim_congested(zone)) {
811 cond_resched();
812
813 /* In case we scheduled, work out time remaining */
814 ret = timeout - (jiffies - start);
815 if (ret < 0)
816 ret = 0;
817
818 goto out;
819 }
820
821 /* Sleep until uncongested or a write happens */
822 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
823 ret = io_schedule_timeout(timeout);
824 finish_wait(wqh, &wait);
825
826out:
827 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
828 jiffies_to_usecs(jiffies - start));
829
830 return ret;
831}
832EXPORT_SYMBOL(wait_iff_congested);