writeback: replace custom worker pool implementation with unbound workqueue
[linux-2.6-block.git] / mm / backing-dev.c
CommitLineData
3fcfab16
AM
1
2#include <linux/wait.h>
3#include <linux/backing-dev.h>
03ba3782
JA
4#include <linux/kthread.h>
5#include <linux/freezer.h>
3fcfab16 6#include <linux/fs.h>
26160158 7#include <linux/pagemap.h>
03ba3782 8#include <linux/mm.h>
3fcfab16
AM
9#include <linux/sched.h>
10#include <linux/module.h>
cf0ca9fe
PZ
11#include <linux/writeback.h>
12#include <linux/device.h>
455b2864 13#include <trace/events/writeback.h>
cf0ca9fe 14
c3c53206
JA
15static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
16
26160158 17struct backing_dev_info default_backing_dev_info = {
d993831f 18 .name = "default",
26160158
JA
19 .ra_pages = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
20 .state = 0,
21 .capabilities = BDI_CAP_MAP_COPY,
26160158
JA
22};
23EXPORT_SYMBOL_GPL(default_backing_dev_info);
cf0ca9fe 24
5129a469
JE
25struct backing_dev_info noop_backing_dev_info = {
26 .name = "noop",
976e48f8 27 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
5129a469
JE
28};
29EXPORT_SYMBOL_GPL(noop_backing_dev_info);
30
cf0ca9fe 31static struct class *bdi_class;
cfc4ba53
JA
32
33/*
181387da 34 * bdi_lock protects updates to bdi_list. bdi_list has RCU reader side
cfc4ba53
JA
35 * locking.
36 */
03ba3782 37DEFINE_SPINLOCK(bdi_lock);
66f3b8e2 38LIST_HEAD(bdi_list);
03ba3782 39
839a8e86
TH
40/* bdi_wq serves all asynchronous writeback tasks */
41struct workqueue_struct *bdi_wq;
42
f758eeab
CH
43void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
44{
45 if (wb1 < wb2) {
46 spin_lock(&wb1->list_lock);
47 spin_lock_nested(&wb2->list_lock, 1);
48 } else {
49 spin_lock(&wb2->list_lock);
50 spin_lock_nested(&wb1->list_lock, 1);
51 }
52}
53
76f1418b
MS
54#ifdef CONFIG_DEBUG_FS
55#include <linux/debugfs.h>
56#include <linux/seq_file.h>
57
58static struct dentry *bdi_debug_root;
59
60static void bdi_debug_init(void)
61{
62 bdi_debug_root = debugfs_create_dir("bdi", NULL);
63}
64
65static int bdi_debug_stats_show(struct seq_file *m, void *v)
66{
67 struct backing_dev_info *bdi = m->private;
c1955ce3 68 struct bdi_writeback *wb = &bdi->wb;
364aeb28
DR
69 unsigned long background_thresh;
70 unsigned long dirty_thresh;
71 unsigned long bdi_thresh;
345227d7 72 unsigned long nr_dirty, nr_io, nr_more_io;
f09b00d3
JA
73 struct inode *inode;
74
345227d7 75 nr_dirty = nr_io = nr_more_io = 0;
f758eeab 76 spin_lock(&wb->list_lock);
7ccf19a8 77 list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
c1955ce3 78 nr_dirty++;
7ccf19a8 79 list_for_each_entry(inode, &wb->b_io, i_wb_list)
c1955ce3 80 nr_io++;
7ccf19a8 81 list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
c1955ce3 82 nr_more_io++;
f758eeab 83 spin_unlock(&wb->list_lock);
76f1418b 84
16c4042f
WF
85 global_dirty_limits(&background_thresh, &dirty_thresh);
86 bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
76f1418b
MS
87
88#define K(x) ((x) << (PAGE_SHIFT - 10))
89 seq_printf(m,
00821b00
WF
90 "BdiWriteback: %10lu kB\n"
91 "BdiReclaimable: %10lu kB\n"
92 "BdiDirtyThresh: %10lu kB\n"
93 "DirtyThresh: %10lu kB\n"
94 "BackgroundThresh: %10lu kB\n"
c8e28ce0 95 "BdiDirtied: %10lu kB\n"
00821b00
WF
96 "BdiWritten: %10lu kB\n"
97 "BdiWriteBandwidth: %10lu kBps\n"
98 "b_dirty: %10lu\n"
99 "b_io: %10lu\n"
100 "b_more_io: %10lu\n"
101 "bdi_list: %10u\n"
102 "state: %10lx\n",
76f1418b
MS
103 (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
104 (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
f7d2b1ec
JK
105 K(bdi_thresh),
106 K(dirty_thresh),
107 K(background_thresh),
c8e28ce0 108 (unsigned long) K(bdi_stat(bdi, BDI_DIRTIED)),
f7d2b1ec 109 (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
00821b00 110 (unsigned long) K(bdi->write_bandwidth),
f7d2b1ec
JK
111 nr_dirty,
112 nr_io,
113 nr_more_io,
c1955ce3 114 !list_empty(&bdi->bdi_list), bdi->state);
76f1418b
MS
115#undef K
116
117 return 0;
118}
119
120static int bdi_debug_stats_open(struct inode *inode, struct file *file)
121{
122 return single_open(file, bdi_debug_stats_show, inode->i_private);
123}
124
125static const struct file_operations bdi_debug_stats_fops = {
126 .open = bdi_debug_stats_open,
127 .read = seq_read,
128 .llseek = seq_lseek,
129 .release = single_release,
130};
131
132static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
133{
134 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
135 bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
136 bdi, &bdi_debug_stats_fops);
137}
138
139static void bdi_debug_unregister(struct backing_dev_info *bdi)
140{
141 debugfs_remove(bdi->debug_stats);
142 debugfs_remove(bdi->debug_dir);
143}
144#else
145static inline void bdi_debug_init(void)
146{
147}
148static inline void bdi_debug_register(struct backing_dev_info *bdi,
149 const char *name)
150{
151}
152static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
153{
154}
155#endif
156
cf0ca9fe
PZ
157static ssize_t read_ahead_kb_store(struct device *dev,
158 struct device_attribute *attr,
159 const char *buf, size_t count)
160{
161 struct backing_dev_info *bdi = dev_get_drvdata(dev);
cf0ca9fe 162 unsigned long read_ahead_kb;
7034ed13 163 ssize_t ret;
cf0ca9fe 164
7034ed13
NJ
165 ret = kstrtoul(buf, 10, &read_ahead_kb);
166 if (ret < 0)
167 return ret;
168
169 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
170
171 return count;
cf0ca9fe
PZ
172}
173
174#define K(pages) ((pages) << (PAGE_SHIFT - 10))
175
176#define BDI_SHOW(name, expr) \
177static ssize_t name##_show(struct device *dev, \
178 struct device_attribute *attr, char *page) \
179{ \
180 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
181 \
182 return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
183}
184
185BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
186
189d3c4a
PZ
187static ssize_t min_ratio_store(struct device *dev,
188 struct device_attribute *attr, const char *buf, size_t count)
189{
190 struct backing_dev_info *bdi = dev_get_drvdata(dev);
189d3c4a 191 unsigned int ratio;
7034ed13
NJ
192 ssize_t ret;
193
194 ret = kstrtouint(buf, 10, &ratio);
195 if (ret < 0)
196 return ret;
197
198 ret = bdi_set_min_ratio(bdi, ratio);
199 if (!ret)
200 ret = count;
189d3c4a 201
189d3c4a
PZ
202 return ret;
203}
204BDI_SHOW(min_ratio, bdi->min_ratio)
205
a42dde04
PZ
206static ssize_t max_ratio_store(struct device *dev,
207 struct device_attribute *attr, const char *buf, size_t count)
208{
209 struct backing_dev_info *bdi = dev_get_drvdata(dev);
a42dde04 210 unsigned int ratio;
7034ed13
NJ
211 ssize_t ret;
212
213 ret = kstrtouint(buf, 10, &ratio);
214 if (ret < 0)
215 return ret;
216
217 ret = bdi_set_max_ratio(bdi, ratio);
218 if (!ret)
219 ret = count;
a42dde04 220
a42dde04
PZ
221 return ret;
222}
223BDI_SHOW(max_ratio, bdi->max_ratio)
224
7d311cda
DW
225static ssize_t stable_pages_required_show(struct device *dev,
226 struct device_attribute *attr,
227 char *page)
228{
229 struct backing_dev_info *bdi = dev_get_drvdata(dev);
230
231 return snprintf(page, PAGE_SIZE-1, "%d\n",
232 bdi_cap_stable_pages_required(bdi) ? 1 : 0);
233}
234
cf0ca9fe
PZ
235#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
236
237static struct device_attribute bdi_dev_attrs[] = {
238 __ATTR_RW(read_ahead_kb),
189d3c4a 239 __ATTR_RW(min_ratio),
a42dde04 240 __ATTR_RW(max_ratio),
7d311cda 241 __ATTR_RO(stable_pages_required),
cf0ca9fe
PZ
242 __ATTR_NULL,
243};
244
245static __init int bdi_class_init(void)
246{
247 bdi_class = class_create(THIS_MODULE, "bdi");
14421453
AB
248 if (IS_ERR(bdi_class))
249 return PTR_ERR(bdi_class);
250
cf0ca9fe 251 bdi_class->dev_attrs = bdi_dev_attrs;
76f1418b 252 bdi_debug_init();
cf0ca9fe
PZ
253 return 0;
254}
76f1418b 255postcore_initcall(bdi_class_init);
cf0ca9fe 256
26160158
JA
257static int __init default_bdi_init(void)
258{
259 int err;
260
839a8e86
TH
261 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE |
262 WQ_UNBOUND, 0);
263 if (!bdi_wq)
264 return -ENOMEM;
265
26160158
JA
266 err = bdi_init(&default_backing_dev_info);
267 if (!err)
268 bdi_register(&default_backing_dev_info, NULL, "default");
976e48f8 269 err = bdi_init(&noop_backing_dev_info);
26160158
JA
270
271 return err;
272}
273subsys_initcall(default_bdi_init);
274
03ba3782
JA
275int bdi_has_dirty_io(struct backing_dev_info *bdi)
276{
277 return wb_has_dirty_io(&bdi->wb);
278}
279
6467716a
AB
280/*
281 * This function is used when the first inode for this bdi is marked dirty. It
282 * wakes-up the corresponding bdi thread which should then take care of the
283 * periodic background write-out of dirty inodes. Since the write-out would
284 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
285 * set up a timer which wakes the bdi thread up later.
286 *
287 * Note, we wouldn't bother setting up the timer, but this function is on the
288 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
289 * by delaying the wake-up.
290 */
291void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
292{
293 unsigned long timeout;
294
295 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
839a8e86 296 mod_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);
03ba3782
JA
297}
298
cfc4ba53
JA
299/*
300 * Remove bdi from bdi_list, and ensure that it is no longer visible
301 */
302static void bdi_remove_from_list(struct backing_dev_info *bdi)
303{
304 spin_lock_bh(&bdi_lock);
305 list_del_rcu(&bdi->bdi_list);
306 spin_unlock_bh(&bdi_lock);
307
ef323088 308 synchronize_rcu_expedited();
839a8e86
TH
309
310 /* bdi_list is now unused, clear it to mark @bdi dying */
311 INIT_LIST_HEAD(&bdi->bdi_list);
cfc4ba53
JA
312}
313
cf0ca9fe
PZ
314int bdi_register(struct backing_dev_info *bdi, struct device *parent,
315 const char *fmt, ...)
316{
cf0ca9fe 317 va_list args;
cf0ca9fe
PZ
318 struct device *dev;
319
69fc208b 320 if (bdi->dev) /* The driver needs to use separate queues per device */
c284de61 321 return 0;
f1d0b063 322
cf0ca9fe 323 va_start(args, fmt);
19051c50 324 dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
cf0ca9fe 325 va_end(args);
c284de61
AB
326 if (IS_ERR(dev))
327 return PTR_ERR(dev);
66f3b8e2 328
cf0ca9fe 329 bdi->dev = dev;
cf0ca9fe 330
03ba3782 331 bdi_debug_register(bdi, dev_name(dev));
500b067c 332 set_bit(BDI_registered, &bdi->state);
c284de61
AB
333
334 spin_lock_bh(&bdi_lock);
335 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
336 spin_unlock_bh(&bdi_lock);
337
455b2864 338 trace_writeback_bdi_register(bdi);
c284de61 339 return 0;
cf0ca9fe
PZ
340}
341EXPORT_SYMBOL(bdi_register);
342
343int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
344{
345 return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
346}
347EXPORT_SYMBOL(bdi_register_dev);
348
03ba3782
JA
349/*
350 * Remove bdi from the global list and shutdown any threads we have running
351 */
352static void bdi_wb_shutdown(struct backing_dev_info *bdi)
66f3b8e2 353{
03ba3782
JA
354 if (!bdi_cap_writeback_dirty(bdi))
355 return;
356
357 /*
fff5b85a 358 * Make sure nobody finds us on the bdi_list anymore
03ba3782 359 */
fff5b85a 360 bdi_remove_from_list(bdi);
03ba3782
JA
361
362 /*
839a8e86
TH
363 * Drain work list and shutdown the delayed_work. At this point,
364 * @bdi->bdi_list is empty telling bdi_Writeback_workfn() that @bdi
365 * is dying and its work_list needs to be drained no matter what.
03ba3782 366 */
839a8e86
TH
367 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
368 flush_delayed_work(&bdi->wb.dwork);
369 WARN_ON(!list_empty(&bdi->work_list));
03ba3782
JA
370
371 /*
839a8e86
TH
372 * This shouldn't be necessary unless @bdi for some reason has
373 * unflushed dirty IO after work_list is drained. Do it anyway
374 * just in case.
03ba3782 375 */
839a8e86 376 cancel_delayed_work_sync(&bdi->wb.dwork);
66f3b8e2
JA
377}
378
592b09a4
JA
379/*
380 * This bdi is going away now, make sure that no super_blocks point to it
381 */
382static void bdi_prune_sb(struct backing_dev_info *bdi)
383{
384 struct super_block *sb;
385
386 spin_lock(&sb_lock);
387 list_for_each_entry(sb, &super_blocks, s_list) {
388 if (sb->s_bdi == bdi)
95f28604 389 sb->s_bdi = &default_backing_dev_info;
592b09a4
JA
390 }
391 spin_unlock(&sb_lock);
392}
393
cf0ca9fe
PZ
394void bdi_unregister(struct backing_dev_info *bdi)
395{
2673b4cf
RV
396 struct device *dev = bdi->dev;
397
398 if (dev) {
ccb6108f 399 bdi_set_min_ratio(bdi, 0);
455b2864 400 trace_writeback_bdi_unregister(bdi);
8c4db335
JA
401 bdi_prune_sb(bdi);
402
839a8e86 403 bdi_wb_shutdown(bdi);
76f1418b 404 bdi_debug_unregister(bdi);
2673b4cf
RV
405
406 spin_lock_bh(&bdi->wb_lock);
cf0ca9fe 407 bdi->dev = NULL;
2673b4cf
RV
408 spin_unlock_bh(&bdi->wb_lock);
409
410 device_unregister(dev);
cf0ca9fe
PZ
411 }
412}
413EXPORT_SYMBOL(bdi_unregister);
3fcfab16 414
6467716a
AB
415static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
416{
417 memset(wb, 0, sizeof(*wb));
418
419 wb->bdi = bdi;
420 wb->last_old_flush = jiffies;
421 INIT_LIST_HEAD(&wb->b_dirty);
422 INIT_LIST_HEAD(&wb->b_io);
423 INIT_LIST_HEAD(&wb->b_more_io);
f758eeab 424 spin_lock_init(&wb->list_lock);
839a8e86 425 INIT_DELAYED_WORK(&wb->dwork, bdi_writeback_workfn);
6467716a
AB
426}
427
e98be2d5
WF
428/*
429 * Initial write bandwidth: 100 MB/s
430 */
431#define INIT_BW (100 << (20 - PAGE_SHIFT))
432
b2e8fb6e
PZ
433int bdi_init(struct backing_dev_info *bdi)
434{
03ba3782 435 int i, err;
b2e8fb6e 436
cf0ca9fe
PZ
437 bdi->dev = NULL;
438
189d3c4a 439 bdi->min_ratio = 0;
a42dde04 440 bdi->max_ratio = 100;
eb608e3a 441 bdi->max_prop_frac = FPROP_FRAC_BASE;
03ba3782 442 spin_lock_init(&bdi->wb_lock);
66f3b8e2 443 INIT_LIST_HEAD(&bdi->bdi_list);
03ba3782
JA
444 INIT_LIST_HEAD(&bdi->work_list);
445
446 bdi_wb_init(&bdi->wb, bdi);
447
b2e8fb6e 448 for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
ea319518 449 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
04fbfdc1
PZ
450 if (err)
451 goto err;
452 }
453
454 bdi->dirty_exceeded = 0;
e98be2d5
WF
455
456 bdi->bw_time_stamp = jiffies;
457 bdi->written_stamp = 0;
458
7381131c 459 bdi->balanced_dirty_ratelimit = INIT_BW;
be3ffa27 460 bdi->dirty_ratelimit = INIT_BW;
e98be2d5
WF
461 bdi->write_bandwidth = INIT_BW;
462 bdi->avg_write_bandwidth = INIT_BW;
463
eb608e3a 464 err = fprop_local_init_percpu(&bdi->completions);
04fbfdc1
PZ
465
466 if (err) {
467err:
4b01a0b1 468 while (i--)
04fbfdc1 469 percpu_counter_destroy(&bdi->bdi_stat[i]);
b2e8fb6e
PZ
470 }
471
472 return err;
473}
474EXPORT_SYMBOL(bdi_init);
475
476void bdi_destroy(struct backing_dev_info *bdi)
477{
478 int i;
479
ce5f8e77
JA
480 /*
481 * Splice our entries to the default_backing_dev_info, if this
482 * bdi disappears
483 */
484 if (bdi_has_dirty_io(bdi)) {
485 struct bdi_writeback *dst = &default_backing_dev_info.wb;
486
f758eeab 487 bdi_lock_two(&bdi->wb, dst);
ce5f8e77
JA
488 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
489 list_splice(&bdi->wb.b_io, &dst->b_io);
490 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
f758eeab
CH
491 spin_unlock(&bdi->wb.list_lock);
492 spin_unlock(&dst->list_lock);
ce5f8e77 493 }
66f3b8e2 494
cf0ca9fe
PZ
495 bdi_unregister(bdi);
496
7a401a97 497 /*
839a8e86
TH
498 * If bdi_unregister() had already been called earlier, the dwork
499 * could still be pending because bdi_prune_sb() can race with the
500 * bdi_wakeup_thread_delayed() calls from __mark_inode_dirty().
7a401a97 501 */
839a8e86 502 cancel_delayed_work_sync(&bdi->wb.dwork);
7a401a97 503
b2e8fb6e
PZ
504 for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
505 percpu_counter_destroy(&bdi->bdi_stat[i]);
04fbfdc1 506
eb608e3a 507 fprop_local_destroy_percpu(&bdi->completions);
b2e8fb6e
PZ
508}
509EXPORT_SYMBOL(bdi_destroy);
510
c3c53206
JA
511/*
512 * For use from filesystems to quickly init and register a bdi associated
513 * with dirty writeback
514 */
515int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
516 unsigned int cap)
517{
518 char tmp[32];
519 int err;
520
521 bdi->name = name;
522 bdi->capabilities = cap;
523 err = bdi_init(bdi);
524 if (err)
525 return err;
526
527 sprintf(tmp, "%.28s%s", name, "-%d");
528 err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
529 if (err) {
530 bdi_destroy(bdi);
531 return err;
532 }
533
534 return 0;
535}
536EXPORT_SYMBOL(bdi_setup_and_register);
537
3fcfab16
AM
538static wait_queue_head_t congestion_wqh[2] = {
539 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
540 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
541 };
0e093d99 542static atomic_t nr_bdi_congested[2];
3fcfab16 543
1faa16d2 544void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
3fcfab16
AM
545{
546 enum bdi_state bit;
1faa16d2 547 wait_queue_head_t *wqh = &congestion_wqh[sync];
3fcfab16 548
1faa16d2 549 bit = sync ? BDI_sync_congested : BDI_async_congested;
0e093d99
MG
550 if (test_and_clear_bit(bit, &bdi->state))
551 atomic_dec(&nr_bdi_congested[sync]);
3fcfab16
AM
552 smp_mb__after_clear_bit();
553 if (waitqueue_active(wqh))
554 wake_up(wqh);
555}
556EXPORT_SYMBOL(clear_bdi_congested);
557
1faa16d2 558void set_bdi_congested(struct backing_dev_info *bdi, int sync)
3fcfab16
AM
559{
560 enum bdi_state bit;
561
1faa16d2 562 bit = sync ? BDI_sync_congested : BDI_async_congested;
0e093d99
MG
563 if (!test_and_set_bit(bit, &bdi->state))
564 atomic_inc(&nr_bdi_congested[sync]);
3fcfab16
AM
565}
566EXPORT_SYMBOL(set_bdi_congested);
567
568/**
569 * congestion_wait - wait for a backing_dev to become uncongested
8aa7e847 570 * @sync: SYNC or ASYNC IO
3fcfab16
AM
571 * @timeout: timeout in jiffies
572 *
573 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
574 * write congestion. If no backing_devs are congested then just wait for the
575 * next write to be completed.
576 */
8aa7e847 577long congestion_wait(int sync, long timeout)
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578{
579 long ret;
52bb9198 580 unsigned long start = jiffies;
3fcfab16 581 DEFINE_WAIT(wait);
8aa7e847 582 wait_queue_head_t *wqh = &congestion_wqh[sync];
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583
584 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
585 ret = io_schedule_timeout(timeout);
586 finish_wait(wqh, &wait);
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587
588 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
589 jiffies_to_usecs(jiffies - start));
590
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591 return ret;
592}
593EXPORT_SYMBOL(congestion_wait);
04fbfdc1 594
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595/**
596 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
597 * @zone: A zone to check if it is heavily congested
598 * @sync: SYNC or ASYNC IO
599 * @timeout: timeout in jiffies
600 *
601 * In the event of a congested backing_dev (any backing_dev) and the given
602 * @zone has experienced recent congestion, this waits for up to @timeout
603 * jiffies for either a BDI to exit congestion of the given @sync queue
604 * or a write to complete.
605 *
25985edc 606 * In the absence of zone congestion, cond_resched() is called to yield
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607 * the processor if necessary but otherwise does not sleep.
608 *
609 * The return value is 0 if the sleep is for the full timeout. Otherwise,
610 * it is the number of jiffies that were still remaining when the function
611 * returned. return_value == timeout implies the function did not sleep.
612 */
613long wait_iff_congested(struct zone *zone, int sync, long timeout)
614{
615 long ret;
616 unsigned long start = jiffies;
617 DEFINE_WAIT(wait);
618 wait_queue_head_t *wqh = &congestion_wqh[sync];
619
620 /*
621 * If there is no congestion, or heavy congestion is not being
622 * encountered in the current zone, yield if necessary instead
623 * of sleeping on the congestion queue
624 */
625 if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
626 !zone_is_reclaim_congested(zone)) {
627 cond_resched();
628
629 /* In case we scheduled, work out time remaining */
630 ret = timeout - (jiffies - start);
631 if (ret < 0)
632 ret = 0;
633
634 goto out;
635 }
636
637 /* Sleep until uncongested or a write happens */
638 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
639 ret = io_schedule_timeout(timeout);
640 finish_wait(wqh, &wait);
641
642out:
643 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
644 jiffies_to_usecs(jiffies - start));
645
646 return ret;
647}
648EXPORT_SYMBOL(wait_iff_congested);
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649
650int pdflush_proc_obsolete(struct ctl_table *table, int write,
651 void __user *buffer, size_t *lenp, loff_t *ppos)
652{
653 char kbuf[] = "0\n";
654
655 if (*ppos) {
656 *lenp = 0;
657 return 0;
658 }
659
660 if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
661 return -EFAULT;
662 printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
663 table->procname);
664
665 *lenp = 2;
666 *ppos += *lenp;
667 return 2;
668}