1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
|
#include <linux/wait.h>
#include <linux/backing-dev.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/writeback.h>
#include <linux/device.h>
#include <trace/events/writeback.h>
static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
{
}
EXPORT_SYMBOL(default_unplug_io_fn);
struct backing_dev_info default_backing_dev_info = {
.name = "default",
.ra_pages = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
.state = 0,
.capabilities = BDI_CAP_MAP_COPY,
.unplug_io_fn = default_unplug_io_fn,
};
EXPORT_SYMBOL_GPL(default_backing_dev_info);
struct backing_dev_info noop_backing_dev_info = {
.name = "noop",
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
};
EXPORT_SYMBOL_GPL(noop_backing_dev_info);
static struct class *bdi_class;
/*
* bdi_lock protects updates to bdi_list and bdi_pending_list, as well as
* reader side protection for bdi_pending_list. bdi_list has RCU reader side
* locking.
*/
DEFINE_SPINLOCK(bdi_lock);
LIST_HEAD(bdi_list);
LIST_HEAD(bdi_pending_list);
static struct task_struct *sync_supers_tsk;
static struct timer_list sync_supers_timer;
static int bdi_sync_supers(void *);
static void sync_supers_timer_fn(unsigned long);
#ifdef CONFIG_DEBUG_FS
#include <linux/debugfs.h>
#include <linux/seq_file.h>
static struct dentry *bdi_debug_root;
static void bdi_debug_init(void)
{
bdi_debug_root = debugfs_create_dir("bdi", NULL);
}
static int bdi_debug_stats_show(struct seq_file *m, void *v)
{
struct backing_dev_info *bdi = m->private;
struct bdi_writeback *wb = &bdi->wb;
unsigned long background_thresh;
unsigned long dirty_thresh;
unsigned long bdi_thresh;
unsigned long nr_dirty, nr_io, nr_more_io, nr_wb;
struct inode *inode;
nr_wb = nr_dirty = nr_io = nr_more_io = 0;
spin_lock(&inode_lock);
list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
nr_dirty++;
list_for_each_entry(inode, &wb->b_io, i_wb_list)
nr_io++;
list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
nr_more_io++;
spin_unlock(&inode_lock);
global_dirty_limits(&background_thresh, &dirty_thresh);
bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
#define K(x) ((x) << (PAGE_SHIFT - 10))
seq_printf(m,
"BdiWriteback: %8lu kB\n"
"BdiReclaimable: %8lu kB\n"
"BdiDirtyThresh: %8lu kB\n"
"DirtyThresh: %8lu kB\n"
"BackgroundThresh: %8lu kB\n"
"b_dirty: %8lu\n"
"b_io: %8lu\n"
"b_more_io: %8lu\n"
"bdi_list: %8u\n"
"state: %8lx\n",
(unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
(unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
K(bdi_thresh), K(dirty_thresh),
K(background_thresh), nr_dirty, nr_io, nr_more_io,
!list_empty(&bdi->bdi_list), bdi->state);
#undef K
return 0;
}
static int bdi_debug_stats_open(struct inode *inode, struct file *file)
{
return single_open(file, bdi_debug_stats_show, inode->i_private);
}
static const struct file_operations bdi_debug_stats_fops = {
.open = bdi_debug_stats_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
{
bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
bdi, &bdi_debug_stats_fops);
}
static void bdi_debug_unregister(struct backing_dev_info *bdi)
{
debugfs_remove(bdi->debug_stats);
debugfs_remove(bdi->debug_dir);
}
#else
static inline void bdi_debug_init(void)
{
}
static inline void bdi_debug_register(struct backing_dev_info *bdi,
const char *name)
{
}
static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
{
}
#endif
static ssize_t read_ahead_kb_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct backing_dev_info *bdi = dev_get_drvdata(dev);
char *end;
unsigned long read_ahead_kb;
ssize_t ret = -EINVAL;
read_ahead_kb = simple_strtoul(buf, &end, 10);
if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
ret = count;
}
return ret;
}
#define K(pages) ((pages) << (PAGE_SHIFT - 10))
#define BDI_SHOW(name, expr) \
static ssize_t name##_show(struct device *dev, \
struct device_attribute *attr, char *page) \
{ \
struct backing_dev_info *bdi = dev_get_drvdata(dev); \
\
return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
}
BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
static ssize_t min_ratio_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t count)
{
struct backing_dev_info *bdi = dev_get_drvdata(dev);
char *end;
unsigned int ratio;
ssize_t ret = -EINVAL;
ratio = simple_strtoul(buf, &end, 10);
if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
ret = bdi_set_min_ratio(bdi, ratio);
if (!ret)
ret = count;
}
return ret;
}
BDI_SHOW(min_ratio, bdi->min_ratio)
static ssize_t max_ratio_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t count)
{
struct backing_dev_info *bdi = dev_get_drvdata(dev);
char *end;
unsigned int ratio;
ssize_t ret = -EINVAL;
ratio = simple_strtoul(buf, &end, 10);
if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
ret = bdi_set_max_ratio(bdi, ratio);
if (!ret)
ret = count;
}
return ret;
}
BDI_SHOW(max_ratio, bdi->max_ratio)
#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
static struct device_attribute bdi_dev_attrs[] = {
__ATTR_RW(read_ahead_kb),
__ATTR_RW(min_ratio),
__ATTR_RW(max_ratio),
__ATTR_NULL,
};
static __init int bdi_class_init(void)
{
bdi_class = class_create(THIS_MODULE, "bdi");
if (IS_ERR(bdi_class))
return PTR_ERR(bdi_class);
bdi_class->dev_attrs = bdi_dev_attrs;
bdi_debug_init();
return 0;
}
postcore_initcall(bdi_class_init);
static int __init default_bdi_init(void)
{
int err;
sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
BUG_ON(IS_ERR(sync_supers_tsk));
setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
bdi_arm_supers_timer();
err = bdi_init(&default_backing_dev_info);
if (!err)
bdi_register(&default_backing_dev_info, NULL, "default");
err = bdi_init(&noop_backing_dev_info);
return err;
}
subsys_initcall(default_bdi_init);
int bdi_has_dirty_io(struct backing_dev_info *bdi)
{
return wb_has_dirty_io(&bdi->wb);
}
static void bdi_flush_io(struct backing_dev_info *bdi)
{
struct writeback_control wbc = {
.sync_mode = WB_SYNC_NONE,
.older_than_this = NULL,
.range_cyclic = 1,
.nr_to_write = 1024,
};
writeback_inodes_wb(&bdi->wb, &wbc);
}
/*
* kupdated() used to do this. We cannot do it from the bdi_forker_thread()
* or we risk deadlocking on ->s_umount. The longer term solution would be
* to implement sync_supers_bdi() or similar and simply do it from the
* bdi writeback thread individually.
*/
static int bdi_sync_supers(void *unused)
{
set_user_nice(current, 0);
while (!kthread_should_stop()) {
set_current_state(TASK_INTERRUPTIBLE);
schedule();
/*
* Do this periodically, like kupdated() did before.
*/
sync_supers();
}
return 0;
}
void bdi_arm_supers_timer(void)
{
unsigned long next;
if (!dirty_writeback_interval)
return;
next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
mod_timer(&sync_supers_timer, round_jiffies_up(next));
}
static void sync_supers_timer_fn(unsigned long unused)
{
wake_up_process(sync_supers_tsk);
bdi_arm_supers_timer();
}
static void wakeup_timer_fn(unsigned long data)
{
struct backing_dev_info *bdi = (struct backing_dev_info *)data;
spin_lock_bh(&bdi->wb_lock);
if (bdi->wb.task) {
trace_writeback_wake_thread(bdi);
wake_up_process(bdi->wb.task);
} else {
/*
* When bdi tasks are inactive for long time, they are killed.
* In this case we have to wake-up the forker thread which
* should create and run the bdi thread.
*/
trace_writeback_wake_forker_thread(bdi);
wake_up_process(default_backing_dev_info.wb.task);
}
spin_unlock_bh(&bdi->wb_lock);
}
/*
* This function is used when the first inode for this bdi is marked dirty. It
* wakes-up the corresponding bdi thread which should then take care of the
* periodic background write-out of dirty inodes. Since the write-out would
* starts only 'dirty_writeback_interval' centisecs from now anyway, we just
* set up a timer which wakes the bdi thread up later.
*
* Note, we wouldn't bother setting up the timer, but this function is on the
* fast-path (used by '__mark_inode_dirty()'), so we save few context switches
* by delaying the wake-up.
*/
void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
{
unsigned long timeout;
timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout);
}
/*
* Calculate the longest interval (jiffies) bdi threads are allowed to be
* inactive.
*/
static unsigned long bdi_longest_inactive(void)
{
unsigned long interval;
interval = msecs_to_jiffies(dirty_writeback_interval * 10);
return max(5UL * 60 * HZ, interval);
}
static int bdi_forker_thread(void *ptr)
{
struct bdi_writeback *me = ptr;
current->flags |= PF_SWAPWRITE;
set_freezable();
/*
* Our parent may run at a different priority, just set us to normal
*/
set_user_nice(current, 0);
for (;;) {
struct task_struct *task = NULL;
struct backing_dev_info *bdi;
enum {
NO_ACTION, /* Nothing to do */
FORK_THREAD, /* Fork bdi thread */
KILL_THREAD, /* Kill inactive bdi thread */
} action = NO_ACTION;
/*
* Temporary measure, we want to make sure we don't see
* dirty data on the default backing_dev_info
*/
if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
del_timer(&me->wakeup_timer);
wb_do_writeback(me, 0);
}
spin_lock_bh(&bdi_lock);
set_current_state(TASK_INTERRUPTIBLE);
list_for_each_entry(bdi, &bdi_list, bdi_list) {
bool have_dirty_io;
if (!bdi_cap_writeback_dirty(bdi) ||
bdi_cap_flush_forker(bdi))
continue;
WARN(!test_bit(BDI_registered, &bdi->state),
"bdi %p/%s is not registered!\n", bdi, bdi->name);
have_dirty_io = !list_empty(&bdi->work_list) ||
wb_has_dirty_io(&bdi->wb);
/*
* If the bdi has work to do, but the thread does not
* exist - create it.
*/
if (!bdi->wb.task && have_dirty_io) {
/*
* Set the pending bit - if someone will try to
* unregister this bdi - it'll wait on this bit.
*/
set_bit(BDI_pending, &bdi->state);
action = FORK_THREAD;
break;
}
spin_lock(&bdi->wb_lock);
/*
* If there is no work to do and the bdi thread was
* inactive long enough - kill it. The wb_lock is taken
* to make sure no-one adds more work to this bdi and
* wakes the bdi thread up.
*/
if (bdi->wb.task && !have_dirty_io &&
time_after(jiffies, bdi->wb.last_active +
bdi_longest_inactive())) {
task = bdi->wb.task;
bdi->wb.task = NULL;
spin_unlock(&bdi->wb_lock);
set_bit(BDI_pending, &bdi->state);
action = KILL_THREAD;
break;
}
spin_unlock(&bdi->wb_lock);
}
spin_unlock_bh(&bdi_lock);
/* Keep working if default bdi still has things to do */
if (!list_empty(&me->bdi->work_list))
__set_current_state(TASK_RUNNING);
switch (action) {
case FORK_THREAD:
__set_current_state(TASK_RUNNING);
task = kthread_create(bdi_writeback_thread, &bdi->wb,
"flush-%s", dev_name(bdi->dev));
if (IS_ERR(task)) {
/*
* If thread creation fails, force writeout of
* the bdi from the thread.
*/
bdi_flush_io(bdi);
} else {
/*
* The spinlock makes sure we do not lose
* wake-ups when racing with 'bdi_queue_work()'.
* And as soon as the bdi thread is visible, we
* can start it.
*/
spin_lock_bh(&bdi->wb_lock);
bdi->wb.task = task;
spin_unlock_bh(&bdi->wb_lock);
wake_up_process(task);
}
break;
case KILL_THREAD:
__set_current_state(TASK_RUNNING);
kthread_stop(task);
break;
case NO_ACTION:
if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
/*
* There are no dirty data. The only thing we
* should now care about is checking for
* inactive bdi threads and killing them. Thus,
* let's sleep for longer time, save energy and
* be friendly for battery-driven devices.
*/
schedule_timeout(bdi_longest_inactive());
else
schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
try_to_freeze();
/* Back to the main loop */
continue;
}
/*
* Clear pending bit and wakeup anybody waiting to tear us down.
*/
clear_bit(BDI_pending, &bdi->state);
smp_mb__after_clear_bit();
wake_up_bit(&bdi->state, BDI_pending);
}
return 0;
}
/*
* Remove bdi from bdi_list, and ensure that it is no longer visible
*/
static void bdi_remove_from_list(struct backing_dev_info *bdi)
{
spin_lock_bh(&bdi_lock);
list_del_rcu(&bdi->bdi_list);
spin_unlock_bh(&bdi_lock);
synchronize_rcu();
}
int bdi_register(struct backing_dev_info *bdi, struct device *parent,
const char *fmt, ...)
{
va_list args;
struct device *dev;
if (bdi->dev) /* The driver needs to use separate queues per device */
return 0;
va_start(args, fmt);
dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
va_end(args);
if (IS_ERR(dev))
return PTR_ERR(dev);
bdi->dev = dev;
/*
* Just start the forker thread for our default backing_dev_info,
* and add other bdi's to the list. They will get a thread created
* on-demand when they need it.
*/
if (bdi_cap_flush_forker(bdi)) {
struct bdi_writeback *wb = &bdi->wb;
wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
dev_name(dev));
if (IS_ERR(wb->task))
return PTR_ERR(wb->task);
}
bdi_debug_register(bdi, dev_name(dev));
set_bit(BDI_registered, &bdi->state);
spin_lock_bh(&bdi_lock);
list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
spin_unlock_bh(&bdi_lock);
trace_writeback_bdi_register(bdi);
return 0;
}
EXPORT_SYMBOL(bdi_register);
int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
{
return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
}
EXPORT_SYMBOL(bdi_register_dev);
/*
* Remove bdi from the global list and shutdown any threads we have running
*/
static void bdi_wb_shutdown(struct backing_dev_info *bdi)
{
if (!bdi_cap_writeback_dirty(bdi))
return;
/*
* Make sure nobody finds us on the bdi_list anymore
*/
bdi_remove_from_list(bdi);
/*
* If setup is pending, wait for that to complete first
*/
wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
TASK_UNINTERRUPTIBLE);
/*
* Finally, kill the kernel thread. We don't need to be RCU
* safe anymore, since the bdi is gone from visibility. Force
* unfreeze of the thread before calling kthread_stop(), otherwise
* it would never exet if it is currently stuck in the refrigerator.
*/
if (bdi->wb.task) {
thaw_process(bdi->wb.task);
kthread_stop(bdi->wb.task);
}
}
/*
* This bdi is going away now, make sure that no super_blocks point to it
*/
static void bdi_prune_sb(struct backing_dev_info *bdi)
{
struct super_block *sb;
spin_lock(&sb_lock);
list_for_each_entry(sb, &super_blocks, s_list) {
if (sb->s_bdi == bdi)
sb->s_bdi = NULL;
}
spin_unlock(&sb_lock);
}
void bdi_unregister(struct backing_dev_info *bdi)
{
if (bdi->dev) {
trace_writeback_bdi_unregister(bdi);
bdi_prune_sb(bdi);
del_timer_sync(&bdi->wb.wakeup_timer);
if (!bdi_cap_flush_forker(bdi))
bdi_wb_shutdown(bdi);
bdi_debug_unregister(bdi);
device_unregister(bdi->dev);
bdi->dev = NULL;
}
}
EXPORT_SYMBOL(bdi_unregister);
static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
{
memset(wb, 0, sizeof(*wb));
wb->bdi = bdi;
wb->last_old_flush = jiffies;
INIT_LIST_HEAD(&wb->b_dirty);
INIT_LIST_HEAD(&wb->b_io);
INIT_LIST_HEAD(&wb->b_more_io);
setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
}
int bdi_init(struct backing_dev_info *bdi)
{
int i, err;
bdi->dev = NULL;
bdi->min_ratio = 0;
bdi->max_ratio = 100;
bdi->max_prop_frac = PROP_FRAC_BASE;
spin_lock_init(&bdi->wb_lock);
INIT_LIST_HEAD(&bdi->bdi_list);
INIT_LIST_HEAD(&bdi->work_list);
bdi_wb_init(&bdi->wb, bdi);
for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
err = percpu_counter_init(&bdi->bdi_stat[i], 0);
if (err)
goto err;
}
bdi->dirty_exceeded = 0;
err = prop_local_init_percpu(&bdi->completions);
if (err) {
err:
while (i--)
percpu_counter_destroy(&bdi->bdi_stat[i]);
}
return err;
}
EXPORT_SYMBOL(bdi_init);
void bdi_destroy(struct backing_dev_info *bdi)
{
int i;
/*
* Splice our entries to the default_backing_dev_info, if this
* bdi disappears
*/
if (bdi_has_dirty_io(bdi)) {
struct bdi_writeback *dst = &default_backing_dev_info.wb;
spin_lock(&inode_lock);
list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
list_splice(&bdi->wb.b_io, &dst->b_io);
list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
spin_unlock(&inode_lock);
}
bdi_unregister(bdi);
for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
percpu_counter_destroy(&bdi->bdi_stat[i]);
prop_local_destroy_percpu(&bdi->completions);
}
EXPORT_SYMBOL(bdi_destroy);
/*
* For use from filesystems to quickly init and register a bdi associated
* with dirty writeback
*/
int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
unsigned int cap)
{
char tmp[32];
int err;
bdi->name = name;
bdi->capabilities = cap;
err = bdi_init(bdi);
if (err)
return err;
sprintf(tmp, "%.28s%s", name, "-%d");
err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
if (err) {
bdi_destroy(bdi);
return err;
}
return 0;
}
EXPORT_SYMBOL(bdi_setup_and_register);
static wait_queue_head_t congestion_wqh[2] = {
__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
};
static atomic_t nr_bdi_congested[2];
void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
{
enum bdi_state bit;
wait_queue_head_t *wqh = &congestion_wqh[sync];
bit = sync ? BDI_sync_congested : BDI_async_congested;
if (test_and_clear_bit(bit, &bdi->state))
atomic_dec(&nr_bdi_congested[sync]);
smp_mb__after_clear_bit();
if (waitqueue_active(wqh))
wake_up(wqh);
}
EXPORT_SYMBOL(clear_bdi_congested);
void set_bdi_congested(struct backing_dev_info *bdi, int sync)
{
enum bdi_state bit;
bit = sync ? BDI_sync_congested : BDI_async_congested;
if (!test_and_set_bit(bit, &bdi->state))
atomic_inc(&nr_bdi_congested[sync]);
}
EXPORT_SYMBOL(set_bdi_congested);
/**
* congestion_wait - wait for a backing_dev to become uncongested
* @sync: SYNC or ASYNC IO
* @timeout: timeout in jiffies
*
* Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
* write congestion. If no backing_devs are congested then just wait for the
* next write to be completed.
*/
long congestion_wait(int sync, long timeout)
{
long ret;
unsigned long start = jiffies;
DEFINE_WAIT(wait);
wait_queue_head_t *wqh = &congestion_wqh[sync];
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
ret = io_schedule_timeout(timeout);
finish_wait(wqh, &wait);
trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
jiffies_to_usecs(jiffies - start));
return ret;
}
EXPORT_SYMBOL(congestion_wait);
/**
* wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
* @zone: A zone to check if it is heavily congested
* @sync: SYNC or ASYNC IO
* @timeout: timeout in jiffies
*
* In the event of a congested backing_dev (any backing_dev) and the given
* @zone has experienced recent congestion, this waits for up to @timeout
* jiffies for either a BDI to exit congestion of the given @sync queue
* or a write to complete.
*
* In the absense of zone congestion, cond_resched() is called to yield
* the processor if necessary but otherwise does not sleep.
*
* The return value is 0 if the sleep is for the full timeout. Otherwise,
* it is the number of jiffies that were still remaining when the function
* returned. return_value == timeout implies the function did not sleep.
*/
long wait_iff_congested(struct zone *zone, int sync, long timeout)
{
long ret;
unsigned long start = jiffies;
DEFINE_WAIT(wait);
wait_queue_head_t *wqh = &congestion_wqh[sync];
/*
* If there is no congestion, or heavy congestion is not being
* encountered in the current zone, yield if necessary instead
* of sleeping on the congestion queue
*/
if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
!zone_is_reclaim_congested(zone)) {
cond_resched();
/* In case we scheduled, work out time remaining */
ret = timeout - (jiffies - start);
if (ret < 0)
ret = 0;
goto out;
}
/* Sleep until uncongested or a write happens */
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
ret = io_schedule_timeout(timeout);
finish_wait(wqh, &wait);
out:
trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
jiffies_to_usecs(jiffies - start));
return ret;
}
EXPORT_SYMBOL(wait_iff_congested);
|
