mm/page-writeback.c: use min3/max3 macros to avoid shadow warnings
[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); \
d9e1241e
GKH
183} \
184static DEVICE_ATTR_RW(name);
cf0ca9fe
PZ
185
186BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
187
189d3c4a
PZ
188static ssize_t min_ratio_store(struct device *dev,
189 struct device_attribute *attr, const char *buf, size_t count)
190{
191 struct backing_dev_info *bdi = dev_get_drvdata(dev);
189d3c4a 192 unsigned int ratio;
7034ed13
NJ
193 ssize_t ret;
194
195 ret = kstrtouint(buf, 10, &ratio);
196 if (ret < 0)
197 return ret;
198
199 ret = bdi_set_min_ratio(bdi, ratio);
200 if (!ret)
201 ret = count;
189d3c4a 202
189d3c4a
PZ
203 return ret;
204}
205BDI_SHOW(min_ratio, bdi->min_ratio)
206
a42dde04
PZ
207static ssize_t max_ratio_store(struct device *dev,
208 struct device_attribute *attr, const char *buf, size_t count)
209{
210 struct backing_dev_info *bdi = dev_get_drvdata(dev);
a42dde04 211 unsigned int ratio;
7034ed13
NJ
212 ssize_t ret;
213
214 ret = kstrtouint(buf, 10, &ratio);
215 if (ret < 0)
216 return ret;
217
218 ret = bdi_set_max_ratio(bdi, ratio);
219 if (!ret)
220 ret = count;
a42dde04 221
a42dde04
PZ
222 return ret;
223}
224BDI_SHOW(max_ratio, bdi->max_ratio)
225
7d311cda
DW
226static ssize_t stable_pages_required_show(struct device *dev,
227 struct device_attribute *attr,
228 char *page)
229{
230 struct backing_dev_info *bdi = dev_get_drvdata(dev);
231
232 return snprintf(page, PAGE_SIZE-1, "%d\n",
233 bdi_cap_stable_pages_required(bdi) ? 1 : 0);
234}
d9e1241e
GKH
235static DEVICE_ATTR_RO(stable_pages_required);
236
237static struct attribute *bdi_dev_attrs[] = {
238 &dev_attr_read_ahead_kb.attr,
239 &dev_attr_min_ratio.attr,
240 &dev_attr_max_ratio.attr,
241 &dev_attr_stable_pages_required.attr,
242 NULL,
cf0ca9fe 243};
d9e1241e 244ATTRIBUTE_GROUPS(bdi_dev);
cf0ca9fe
PZ
245
246static __init int bdi_class_init(void)
247{
248 bdi_class = class_create(THIS_MODULE, "bdi");
14421453
AB
249 if (IS_ERR(bdi_class))
250 return PTR_ERR(bdi_class);
251
d9e1241e 252 bdi_class->dev_groups = bdi_dev_groups;
76f1418b 253 bdi_debug_init();
cf0ca9fe
PZ
254 return 0;
255}
76f1418b 256postcore_initcall(bdi_class_init);
cf0ca9fe 257
26160158
JA
258static int __init default_bdi_init(void)
259{
260 int err;
261
839a8e86 262 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE |
b5c872dd 263 WQ_UNBOUND | WQ_SYSFS, 0);
839a8e86
TH
264 if (!bdi_wq)
265 return -ENOMEM;
266
26160158
JA
267 err = bdi_init(&default_backing_dev_info);
268 if (!err)
269 bdi_register(&default_backing_dev_info, NULL, "default");
976e48f8 270 err = bdi_init(&noop_backing_dev_info);
26160158
JA
271
272 return err;
273}
274subsys_initcall(default_bdi_init);
275
03ba3782
JA
276int bdi_has_dirty_io(struct backing_dev_info *bdi)
277{
278 return wb_has_dirty_io(&bdi->wb);
279}
280
6467716a
AB
281/*
282 * This function is used when the first inode for this bdi is marked dirty. It
283 * wakes-up the corresponding bdi thread which should then take care of the
284 * periodic background write-out of dirty inodes. Since the write-out would
285 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
286 * set up a timer which wakes the bdi thread up later.
287 *
288 * Note, we wouldn't bother setting up the timer, but this function is on the
289 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
290 * by delaying the wake-up.
6ca738d6
DB
291 *
292 * We have to be careful not to postpone flush work if it is scheduled for
293 * earlier. Thus we use queue_delayed_work().
6467716a
AB
294 */
295void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
296{
297 unsigned long timeout;
298
299 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
5acda9d1
JK
300 spin_lock_bh(&bdi->wb_lock);
301 if (test_bit(BDI_registered, &bdi->state))
302 queue_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);
303 spin_unlock_bh(&bdi->wb_lock);
03ba3782
JA
304}
305
cfc4ba53
JA
306/*
307 * Remove bdi from bdi_list, and ensure that it is no longer visible
308 */
309static void bdi_remove_from_list(struct backing_dev_info *bdi)
310{
311 spin_lock_bh(&bdi_lock);
312 list_del_rcu(&bdi->bdi_list);
313 spin_unlock_bh(&bdi_lock);
314
ef323088 315 synchronize_rcu_expedited();
cfc4ba53
JA
316}
317
cf0ca9fe
PZ
318int bdi_register(struct backing_dev_info *bdi, struct device *parent,
319 const char *fmt, ...)
320{
cf0ca9fe 321 va_list args;
cf0ca9fe
PZ
322 struct device *dev;
323
69fc208b 324 if (bdi->dev) /* The driver needs to use separate queues per device */
c284de61 325 return 0;
f1d0b063 326
cf0ca9fe 327 va_start(args, fmt);
19051c50 328 dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
cf0ca9fe 329 va_end(args);
c284de61
AB
330 if (IS_ERR(dev))
331 return PTR_ERR(dev);
66f3b8e2 332
cf0ca9fe 333 bdi->dev = dev;
cf0ca9fe 334
03ba3782 335 bdi_debug_register(bdi, dev_name(dev));
500b067c 336 set_bit(BDI_registered, &bdi->state);
c284de61
AB
337
338 spin_lock_bh(&bdi_lock);
339 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
340 spin_unlock_bh(&bdi_lock);
341
455b2864 342 trace_writeback_bdi_register(bdi);
c284de61 343 return 0;
cf0ca9fe
PZ
344}
345EXPORT_SYMBOL(bdi_register);
346
347int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
348{
349 return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
350}
351EXPORT_SYMBOL(bdi_register_dev);
352
03ba3782
JA
353/*
354 * Remove bdi from the global list and shutdown any threads we have running
355 */
356static void bdi_wb_shutdown(struct backing_dev_info *bdi)
66f3b8e2 357{
03ba3782
JA
358 if (!bdi_cap_writeback_dirty(bdi))
359 return;
360
361 /*
fff5b85a 362 * Make sure nobody finds us on the bdi_list anymore
03ba3782 363 */
fff5b85a 364 bdi_remove_from_list(bdi);
03ba3782 365
5acda9d1
JK
366 /* Make sure nobody queues further work */
367 spin_lock_bh(&bdi->wb_lock);
368 clear_bit(BDI_registered, &bdi->state);
369 spin_unlock_bh(&bdi->wb_lock);
370
03ba3782 371 /*
839a8e86
TH
372 * Drain work list and shutdown the delayed_work. At this point,
373 * @bdi->bdi_list is empty telling bdi_Writeback_workfn() that @bdi
374 * is dying and its work_list needs to be drained no matter what.
03ba3782 375 */
839a8e86
TH
376 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
377 flush_delayed_work(&bdi->wb.dwork);
378 WARN_ON(!list_empty(&bdi->work_list));
03ba3782
JA
379
380 /*
839a8e86
TH
381 * This shouldn't be necessary unless @bdi for some reason has
382 * unflushed dirty IO after work_list is drained. Do it anyway
383 * just in case.
03ba3782 384 */
839a8e86 385 cancel_delayed_work_sync(&bdi->wb.dwork);
66f3b8e2
JA
386}
387
592b09a4
JA
388/*
389 * This bdi is going away now, make sure that no super_blocks point to it
390 */
391static void bdi_prune_sb(struct backing_dev_info *bdi)
392{
393 struct super_block *sb;
394
395 spin_lock(&sb_lock);
396 list_for_each_entry(sb, &super_blocks, s_list) {
397 if (sb->s_bdi == bdi)
95f28604 398 sb->s_bdi = &default_backing_dev_info;
592b09a4
JA
399 }
400 spin_unlock(&sb_lock);
401}
402
cf0ca9fe
PZ
403void bdi_unregister(struct backing_dev_info *bdi)
404{
2673b4cf
RV
405 struct device *dev = bdi->dev;
406
407 if (dev) {
ccb6108f 408 bdi_set_min_ratio(bdi, 0);
455b2864 409 trace_writeback_bdi_unregister(bdi);
8c4db335
JA
410 bdi_prune_sb(bdi);
411
839a8e86 412 bdi_wb_shutdown(bdi);
76f1418b 413 bdi_debug_unregister(bdi);
2673b4cf
RV
414
415 spin_lock_bh(&bdi->wb_lock);
cf0ca9fe 416 bdi->dev = NULL;
2673b4cf
RV
417 spin_unlock_bh(&bdi->wb_lock);
418
419 device_unregister(dev);
cf0ca9fe
PZ
420 }
421}
422EXPORT_SYMBOL(bdi_unregister);
3fcfab16 423
6467716a
AB
424static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
425{
426 memset(wb, 0, sizeof(*wb));
427
428 wb->bdi = bdi;
429 wb->last_old_flush = jiffies;
430 INIT_LIST_HEAD(&wb->b_dirty);
431 INIT_LIST_HEAD(&wb->b_io);
432 INIT_LIST_HEAD(&wb->b_more_io);
f758eeab 433 spin_lock_init(&wb->list_lock);
839a8e86 434 INIT_DELAYED_WORK(&wb->dwork, bdi_writeback_workfn);
6467716a
AB
435}
436
e98be2d5
WF
437/*
438 * Initial write bandwidth: 100 MB/s
439 */
440#define INIT_BW (100 << (20 - PAGE_SHIFT))
441
b2e8fb6e
PZ
442int bdi_init(struct backing_dev_info *bdi)
443{
03ba3782 444 int i, err;
b2e8fb6e 445
cf0ca9fe
PZ
446 bdi->dev = NULL;
447
189d3c4a 448 bdi->min_ratio = 0;
a42dde04 449 bdi->max_ratio = 100;
eb608e3a 450 bdi->max_prop_frac = FPROP_FRAC_BASE;
03ba3782 451 spin_lock_init(&bdi->wb_lock);
66f3b8e2 452 INIT_LIST_HEAD(&bdi->bdi_list);
03ba3782
JA
453 INIT_LIST_HEAD(&bdi->work_list);
454
455 bdi_wb_init(&bdi->wb, bdi);
456
b2e8fb6e 457 for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
ea319518 458 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
04fbfdc1
PZ
459 if (err)
460 goto err;
461 }
462
463 bdi->dirty_exceeded = 0;
e98be2d5
WF
464
465 bdi->bw_time_stamp = jiffies;
466 bdi->written_stamp = 0;
467
7381131c 468 bdi->balanced_dirty_ratelimit = INIT_BW;
be3ffa27 469 bdi->dirty_ratelimit = INIT_BW;
e98be2d5
WF
470 bdi->write_bandwidth = INIT_BW;
471 bdi->avg_write_bandwidth = INIT_BW;
472
eb608e3a 473 err = fprop_local_init_percpu(&bdi->completions);
04fbfdc1
PZ
474
475 if (err) {
476err:
4b01a0b1 477 while (i--)
04fbfdc1 478 percpu_counter_destroy(&bdi->bdi_stat[i]);
b2e8fb6e
PZ
479 }
480
481 return err;
482}
483EXPORT_SYMBOL(bdi_init);
484
485void bdi_destroy(struct backing_dev_info *bdi)
486{
487 int i;
488
ce5f8e77
JA
489 /*
490 * Splice our entries to the default_backing_dev_info, if this
491 * bdi disappears
492 */
493 if (bdi_has_dirty_io(bdi)) {
494 struct bdi_writeback *dst = &default_backing_dev_info.wb;
495
f758eeab 496 bdi_lock_two(&bdi->wb, dst);
ce5f8e77
JA
497 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
498 list_splice(&bdi->wb.b_io, &dst->b_io);
499 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
f758eeab
CH
500 spin_unlock(&bdi->wb.list_lock);
501 spin_unlock(&dst->list_lock);
ce5f8e77 502 }
66f3b8e2 503
cf0ca9fe
PZ
504 bdi_unregister(bdi);
505
7a401a97 506 /*
839a8e86
TH
507 * If bdi_unregister() had already been called earlier, the dwork
508 * could still be pending because bdi_prune_sb() can race with the
509 * bdi_wakeup_thread_delayed() calls from __mark_inode_dirty().
7a401a97 510 */
839a8e86 511 cancel_delayed_work_sync(&bdi->wb.dwork);
7a401a97 512
b2e8fb6e
PZ
513 for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
514 percpu_counter_destroy(&bdi->bdi_stat[i]);
04fbfdc1 515
eb608e3a 516 fprop_local_destroy_percpu(&bdi->completions);
b2e8fb6e
PZ
517}
518EXPORT_SYMBOL(bdi_destroy);
519
c3c53206
JA
520/*
521 * For use from filesystems to quickly init and register a bdi associated
522 * with dirty writeback
523 */
524int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
525 unsigned int cap)
526{
c3c53206
JA
527 int err;
528
529 bdi->name = name;
530 bdi->capabilities = cap;
531 err = bdi_init(bdi);
532 if (err)
533 return err;
534
02aa2a37
KC
535 err = bdi_register(bdi, NULL, "%.28s-%ld", name,
536 atomic_long_inc_return(&bdi_seq));
c3c53206
JA
537 if (err) {
538 bdi_destroy(bdi);
539 return err;
540 }
541
542 return 0;
543}
544EXPORT_SYMBOL(bdi_setup_and_register);
545
3fcfab16
AM
546static wait_queue_head_t congestion_wqh[2] = {
547 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
548 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
549 };
0e093d99 550static atomic_t nr_bdi_congested[2];
3fcfab16 551
1faa16d2 552void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
3fcfab16
AM
553{
554 enum bdi_state bit;
1faa16d2 555 wait_queue_head_t *wqh = &congestion_wqh[sync];
3fcfab16 556
1faa16d2 557 bit = sync ? BDI_sync_congested : BDI_async_congested;
0e093d99
MG
558 if (test_and_clear_bit(bit, &bdi->state))
559 atomic_dec(&nr_bdi_congested[sync]);
4e857c58 560 smp_mb__after_atomic();
3fcfab16
AM
561 if (waitqueue_active(wqh))
562 wake_up(wqh);
563}
564EXPORT_SYMBOL(clear_bdi_congested);
565
1faa16d2 566void set_bdi_congested(struct backing_dev_info *bdi, int sync)
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567{
568 enum bdi_state bit;
569
1faa16d2 570 bit = sync ? BDI_sync_congested : BDI_async_congested;
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571 if (!test_and_set_bit(bit, &bdi->state))
572 atomic_inc(&nr_bdi_congested[sync]);
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573}
574EXPORT_SYMBOL(set_bdi_congested);
575
576/**
577 * congestion_wait - wait for a backing_dev to become uncongested
8aa7e847 578 * @sync: SYNC or ASYNC IO
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579 * @timeout: timeout in jiffies
580 *
581 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
582 * write congestion. If no backing_devs are congested then just wait for the
583 * next write to be completed.
584 */
8aa7e847 585long congestion_wait(int sync, long timeout)
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586{
587 long ret;
52bb9198 588 unsigned long start = jiffies;
3fcfab16 589 DEFINE_WAIT(wait);
8aa7e847 590 wait_queue_head_t *wqh = &congestion_wqh[sync];
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591
592 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
593 ret = io_schedule_timeout(timeout);
594 finish_wait(wqh, &wait);
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595
596 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
597 jiffies_to_usecs(jiffies - start));
598
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599 return ret;
600}
601EXPORT_SYMBOL(congestion_wait);
04fbfdc1 602
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603/**
604 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
605 * @zone: A zone to check if it is heavily congested
606 * @sync: SYNC or ASYNC IO
607 * @timeout: timeout in jiffies
608 *
609 * In the event of a congested backing_dev (any backing_dev) and the given
610 * @zone has experienced recent congestion, this waits for up to @timeout
611 * jiffies for either a BDI to exit congestion of the given @sync queue
612 * or a write to complete.
613 *
25985edc 614 * In the absence of zone congestion, cond_resched() is called to yield
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615 * the processor if necessary but otherwise does not sleep.
616 *
617 * The return value is 0 if the sleep is for the full timeout. Otherwise,
618 * it is the number of jiffies that were still remaining when the function
619 * returned. return_value == timeout implies the function did not sleep.
620 */
621long wait_iff_congested(struct zone *zone, int sync, long timeout)
622{
623 long ret;
624 unsigned long start = jiffies;
625 DEFINE_WAIT(wait);
626 wait_queue_head_t *wqh = &congestion_wqh[sync];
627
628 /*
629 * If there is no congestion, or heavy congestion is not being
630 * encountered in the current zone, yield if necessary instead
631 * of sleeping on the congestion queue
632 */
633 if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
634 !zone_is_reclaim_congested(zone)) {
635 cond_resched();
636
637 /* In case we scheduled, work out time remaining */
638 ret = timeout - (jiffies - start);
639 if (ret < 0)
640 ret = 0;
641
642 goto out;
643 }
644
645 /* Sleep until uncongested or a write happens */
646 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
647 ret = io_schedule_timeout(timeout);
648 finish_wait(wqh, &wait);
649
650out:
651 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
652 jiffies_to_usecs(jiffies - start));
653
654 return ret;
655}
656EXPORT_SYMBOL(wait_iff_congested);
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657
658int pdflush_proc_obsolete(struct ctl_table *table, int write,
659 void __user *buffer, size_t *lenp, loff_t *ppos)
660{
661 char kbuf[] = "0\n";
662
4c3bffc2 663 if (*ppos || *lenp < sizeof(kbuf)) {
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664 *lenp = 0;
665 return 0;
666 }
667
668 if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
669 return -EFAULT;
670 printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
671 table->procname);
672
673 *lenp = 2;
674 *ppos += *lenp;
675 return 2;
676}