bdi: make inode_to_bdi() inline
[linux-2.6-block.git] / mm / backing-dev.c
CommitLineData
3fcfab16
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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>
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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
5129a469
JE
17struct backing_dev_info noop_backing_dev_info = {
18 .name = "noop",
976e48f8 19 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
5129a469 20};
a212b105 21EXPORT_SYMBOL_GPL(noop_backing_dev_info);
5129a469 22
cf0ca9fe 23static struct class *bdi_class;
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24
25/*
181387da 26 * bdi_lock protects updates to bdi_list. bdi_list has RCU reader side
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27 * locking.
28 */
03ba3782 29DEFINE_SPINLOCK(bdi_lock);
66f3b8e2 30LIST_HEAD(bdi_list);
03ba3782 31
839a8e86
TH
32/* bdi_wq serves all asynchronous writeback tasks */
33struct workqueue_struct *bdi_wq;
34
76f1418b
MS
35#ifdef CONFIG_DEBUG_FS
36#include <linux/debugfs.h>
37#include <linux/seq_file.h>
38
39static struct dentry *bdi_debug_root;
40
41static void bdi_debug_init(void)
42{
43 bdi_debug_root = debugfs_create_dir("bdi", NULL);
44}
45
46static int bdi_debug_stats_show(struct seq_file *m, void *v)
47{
48 struct backing_dev_info *bdi = m->private;
c1955ce3 49 struct bdi_writeback *wb = &bdi->wb;
364aeb28
DR
50 unsigned long background_thresh;
51 unsigned long dirty_thresh;
52 unsigned long bdi_thresh;
0ae45f63 53 unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
f09b00d3
JA
54 struct inode *inode;
55
0ae45f63 56 nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
f758eeab 57 spin_lock(&wb->list_lock);
7ccf19a8 58 list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
c1955ce3 59 nr_dirty++;
7ccf19a8 60 list_for_each_entry(inode, &wb->b_io, i_wb_list)
c1955ce3 61 nr_io++;
7ccf19a8 62 list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
c1955ce3 63 nr_more_io++;
0ae45f63
TT
64 list_for_each_entry(inode, &wb->b_dirty_time, i_wb_list)
65 if (inode->i_state & I_DIRTY_TIME)
66 nr_dirty_time++;
f758eeab 67 spin_unlock(&wb->list_lock);
76f1418b 68
16c4042f 69 global_dirty_limits(&background_thresh, &dirty_thresh);
a88a341a 70 bdi_thresh = wb_dirty_limit(wb, dirty_thresh);
76f1418b
MS
71
72#define K(x) ((x) << (PAGE_SHIFT - 10))
73 seq_printf(m,
00821b00
WF
74 "BdiWriteback: %10lu kB\n"
75 "BdiReclaimable: %10lu kB\n"
76 "BdiDirtyThresh: %10lu kB\n"
77 "DirtyThresh: %10lu kB\n"
78 "BackgroundThresh: %10lu kB\n"
c8e28ce0 79 "BdiDirtied: %10lu kB\n"
00821b00
WF
80 "BdiWritten: %10lu kB\n"
81 "BdiWriteBandwidth: %10lu kBps\n"
82 "b_dirty: %10lu\n"
83 "b_io: %10lu\n"
84 "b_more_io: %10lu\n"
0ae45f63 85 "b_dirty_time: %10lu\n"
00821b00
WF
86 "bdi_list: %10u\n"
87 "state: %10lx\n",
93f78d88
TH
88 (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
89 (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
f7d2b1ec
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90 K(bdi_thresh),
91 K(dirty_thresh),
92 K(background_thresh),
93f78d88
TH
93 (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
94 (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
a88a341a 95 (unsigned long) K(wb->write_bandwidth),
f7d2b1ec
JK
96 nr_dirty,
97 nr_io,
98 nr_more_io,
0ae45f63 99 nr_dirty_time,
4452226e 100 !list_empty(&bdi->bdi_list), bdi->wb.state);
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MS
101#undef K
102
103 return 0;
104}
105
106static int bdi_debug_stats_open(struct inode *inode, struct file *file)
107{
108 return single_open(file, bdi_debug_stats_show, inode->i_private);
109}
110
111static const struct file_operations bdi_debug_stats_fops = {
112 .open = bdi_debug_stats_open,
113 .read = seq_read,
114 .llseek = seq_lseek,
115 .release = single_release,
116};
117
118static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
119{
120 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
121 bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
122 bdi, &bdi_debug_stats_fops);
123}
124
125static void bdi_debug_unregister(struct backing_dev_info *bdi)
126{
127 debugfs_remove(bdi->debug_stats);
128 debugfs_remove(bdi->debug_dir);
129}
130#else
131static inline void bdi_debug_init(void)
132{
133}
134static inline void bdi_debug_register(struct backing_dev_info *bdi,
135 const char *name)
136{
137}
138static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
139{
140}
141#endif
142
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143static ssize_t read_ahead_kb_store(struct device *dev,
144 struct device_attribute *attr,
145 const char *buf, size_t count)
146{
147 struct backing_dev_info *bdi = dev_get_drvdata(dev);
cf0ca9fe 148 unsigned long read_ahead_kb;
7034ed13 149 ssize_t ret;
cf0ca9fe 150
7034ed13
NJ
151 ret = kstrtoul(buf, 10, &read_ahead_kb);
152 if (ret < 0)
153 return ret;
154
155 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
156
157 return count;
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PZ
158}
159
160#define K(pages) ((pages) << (PAGE_SHIFT - 10))
161
162#define BDI_SHOW(name, expr) \
163static ssize_t name##_show(struct device *dev, \
164 struct device_attribute *attr, char *page) \
165{ \
166 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
167 \
168 return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
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169} \
170static DEVICE_ATTR_RW(name);
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171
172BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
173
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174static ssize_t min_ratio_store(struct device *dev,
175 struct device_attribute *attr, const char *buf, size_t count)
176{
177 struct backing_dev_info *bdi = dev_get_drvdata(dev);
189d3c4a 178 unsigned int ratio;
7034ed13
NJ
179 ssize_t ret;
180
181 ret = kstrtouint(buf, 10, &ratio);
182 if (ret < 0)
183 return ret;
184
185 ret = bdi_set_min_ratio(bdi, ratio);
186 if (!ret)
187 ret = count;
189d3c4a 188
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189 return ret;
190}
191BDI_SHOW(min_ratio, bdi->min_ratio)
192
a42dde04
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193static ssize_t max_ratio_store(struct device *dev,
194 struct device_attribute *attr, const char *buf, size_t count)
195{
196 struct backing_dev_info *bdi = dev_get_drvdata(dev);
a42dde04 197 unsigned int ratio;
7034ed13
NJ
198 ssize_t ret;
199
200 ret = kstrtouint(buf, 10, &ratio);
201 if (ret < 0)
202 return ret;
203
204 ret = bdi_set_max_ratio(bdi, ratio);
205 if (!ret)
206 ret = count;
a42dde04 207
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208 return ret;
209}
210BDI_SHOW(max_ratio, bdi->max_ratio)
211
7d311cda
DW
212static ssize_t stable_pages_required_show(struct device *dev,
213 struct device_attribute *attr,
214 char *page)
215{
216 struct backing_dev_info *bdi = dev_get_drvdata(dev);
217
218 return snprintf(page, PAGE_SIZE-1, "%d\n",
219 bdi_cap_stable_pages_required(bdi) ? 1 : 0);
220}
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GKH
221static DEVICE_ATTR_RO(stable_pages_required);
222
223static struct attribute *bdi_dev_attrs[] = {
224 &dev_attr_read_ahead_kb.attr,
225 &dev_attr_min_ratio.attr,
226 &dev_attr_max_ratio.attr,
227 &dev_attr_stable_pages_required.attr,
228 NULL,
cf0ca9fe 229};
d9e1241e 230ATTRIBUTE_GROUPS(bdi_dev);
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231
232static __init int bdi_class_init(void)
233{
234 bdi_class = class_create(THIS_MODULE, "bdi");
14421453
AB
235 if (IS_ERR(bdi_class))
236 return PTR_ERR(bdi_class);
237
d9e1241e 238 bdi_class->dev_groups = bdi_dev_groups;
76f1418b 239 bdi_debug_init();
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240 return 0;
241}
76f1418b 242postcore_initcall(bdi_class_init);
cf0ca9fe 243
26160158
JA
244static int __init default_bdi_init(void)
245{
246 int err;
247
839a8e86 248 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE |
b5c872dd 249 WQ_UNBOUND | WQ_SYSFS, 0);
839a8e86
TH
250 if (!bdi_wq)
251 return -ENOMEM;
252
976e48f8 253 err = bdi_init(&noop_backing_dev_info);
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254
255 return err;
256}
257subsys_initcall(default_bdi_init);
258
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259int bdi_has_dirty_io(struct backing_dev_info *bdi)
260{
261 return wb_has_dirty_io(&bdi->wb);
262}
263
6467716a 264/*
f0054bb1 265 * This function is used when the first inode for this wb is marked dirty. It
6467716a
AB
266 * wakes-up the corresponding bdi thread which should then take care of the
267 * periodic background write-out of dirty inodes. Since the write-out would
268 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
269 * set up a timer which wakes the bdi thread up later.
270 *
271 * Note, we wouldn't bother setting up the timer, but this function is on the
272 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
273 * by delaying the wake-up.
6ca738d6
DB
274 *
275 * We have to be careful not to postpone flush work if it is scheduled for
276 * earlier. Thus we use queue_delayed_work().
6467716a 277 */
f0054bb1 278void wb_wakeup_delayed(struct bdi_writeback *wb)
6467716a
AB
279{
280 unsigned long timeout;
281
282 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
f0054bb1
TH
283 spin_lock_bh(&wb->work_lock);
284 if (test_bit(WB_registered, &wb->state))
285 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
286 spin_unlock_bh(&wb->work_lock);
03ba3782
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287}
288
a88a341a
TH
289/*
290 * Initial write bandwidth: 100 MB/s
291 */
292#define INIT_BW (100 << (20 - PAGE_SHIFT))
293
f0054bb1 294static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
6467716a 295{
93f78d88
TH
296 int i, err;
297
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AB
298 memset(wb, 0, sizeof(*wb));
299
300 wb->bdi = bdi;
301 wb->last_old_flush = jiffies;
302 INIT_LIST_HEAD(&wb->b_dirty);
303 INIT_LIST_HEAD(&wb->b_io);
304 INIT_LIST_HEAD(&wb->b_more_io);
0ae45f63 305 INIT_LIST_HEAD(&wb->b_dirty_time);
f758eeab 306 spin_lock_init(&wb->list_lock);
93f78d88 307
a88a341a
TH
308 wb->bw_time_stamp = jiffies;
309 wb->balanced_dirty_ratelimit = INIT_BW;
310 wb->dirty_ratelimit = INIT_BW;
311 wb->write_bandwidth = INIT_BW;
312 wb->avg_write_bandwidth = INIT_BW;
313
f0054bb1
TH
314 spin_lock_init(&wb->work_lock);
315 INIT_LIST_HEAD(&wb->work_list);
316 INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
317
a88a341a
TH
318 err = fprop_local_init_percpu(&wb->completions, GFP_KERNEL);
319 if (err)
320 return err;
321
93f78d88
TH
322 for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
323 err = percpu_counter_init(&wb->stat[i], 0, GFP_KERNEL);
324 if (err) {
325 while (--i)
326 percpu_counter_destroy(&wb->stat[i]);
a88a341a 327 fprop_local_destroy_percpu(&wb->completions);
93f78d88
TH
328 return err;
329 }
330 }
331
332 return 0;
333}
334
46100071
TH
335/*
336 * Remove bdi from the global list and shutdown any threads we have running
337 */
338static void wb_shutdown(struct bdi_writeback *wb)
339{
340 /* Make sure nobody queues further work */
341 spin_lock_bh(&wb->work_lock);
342 if (!test_and_clear_bit(WB_registered, &wb->state)) {
343 spin_unlock_bh(&wb->work_lock);
344 return;
345 }
346 spin_unlock_bh(&wb->work_lock);
347
348 /*
349 * Drain work list and shutdown the delayed_work. !WB_registered
350 * tells wb_workfn() that @wb is dying and its work_list needs to
351 * be drained no matter what.
352 */
353 mod_delayed_work(bdi_wq, &wb->dwork, 0);
354 flush_delayed_work(&wb->dwork);
355 WARN_ON(!list_empty(&wb->work_list));
356}
357
f0054bb1 358static void wb_exit(struct bdi_writeback *wb)
93f78d88
TH
359{
360 int i;
361
362 WARN_ON(delayed_work_pending(&wb->dwork));
363
364 for (i = 0; i < NR_WB_STAT_ITEMS; i++)
365 percpu_counter_destroy(&wb->stat[i]);
6467716a 366
a88a341a
TH
367 fprop_local_destroy_percpu(&wb->completions);
368}
e98be2d5 369
b2e8fb6e
PZ
370int bdi_init(struct backing_dev_info *bdi)
371{
93f78d88 372 int err;
b2e8fb6e 373
cf0ca9fe
PZ
374 bdi->dev = NULL;
375
189d3c4a 376 bdi->min_ratio = 0;
a42dde04 377 bdi->max_ratio = 100;
eb608e3a 378 bdi->max_prop_frac = FPROP_FRAC_BASE;
66f3b8e2 379 INIT_LIST_HEAD(&bdi->bdi_list);
03ba3782 380
f0054bb1 381 err = wb_init(&bdi->wb, bdi);
93f78d88
TH
382 if (err)
383 return err;
04fbfdc1 384
93f78d88 385 return 0;
b2e8fb6e
PZ
386}
387EXPORT_SYMBOL(bdi_init);
388
46100071
TH
389int bdi_register(struct backing_dev_info *bdi, struct device *parent,
390 const char *fmt, ...)
391{
392 va_list args;
393 struct device *dev;
394
395 if (bdi->dev) /* The driver needs to use separate queues per device */
396 return 0;
397
398 va_start(args, fmt);
399 dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
400 va_end(args);
401 if (IS_ERR(dev))
402 return PTR_ERR(dev);
403
404 bdi->dev = dev;
405
406 bdi_debug_register(bdi, dev_name(dev));
407 set_bit(WB_registered, &bdi->wb.state);
408
409 spin_lock_bh(&bdi_lock);
410 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
411 spin_unlock_bh(&bdi_lock);
412
413 trace_writeback_bdi_register(bdi);
414 return 0;
415}
416EXPORT_SYMBOL(bdi_register);
417
418int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
419{
420 return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
421}
422EXPORT_SYMBOL(bdi_register_dev);
423
424/*
425 * Remove bdi from bdi_list, and ensure that it is no longer visible
426 */
427static void bdi_remove_from_list(struct backing_dev_info *bdi)
428{
429 spin_lock_bh(&bdi_lock);
430 list_del_rcu(&bdi->bdi_list);
431 spin_unlock_bh(&bdi_lock);
432
433 synchronize_rcu_expedited();
434}
435
436/*
437 * Called when the device behind @bdi has been removed or ejected.
438 *
439 * We can't really do much here except for reducing the dirty ratio at
440 * the moment. In the future we should be able to set a flag so that
441 * the filesystem can handle errors at mark_inode_dirty time instead
442 * of only at writeback time.
443 */
444void bdi_unregister(struct backing_dev_info *bdi)
445{
446 if (WARN_ON_ONCE(!bdi->dev))
447 return;
448
449 bdi_set_min_ratio(bdi, 0);
450}
451EXPORT_SYMBOL(bdi_unregister);
452
b2e8fb6e
PZ
453void bdi_destroy(struct backing_dev_info *bdi)
454{
f0054bb1
TH
455 /* make sure nobody finds us on the bdi_list anymore */
456 bdi_remove_from_list(bdi);
457 wb_shutdown(&bdi->wb);
7a401a97 458
c4db59d3
CH
459 if (bdi->dev) {
460 bdi_debug_unregister(bdi);
461 device_unregister(bdi->dev);
462 bdi->dev = NULL;
463 }
464
f0054bb1 465 wb_exit(&bdi->wb);
b2e8fb6e
PZ
466}
467EXPORT_SYMBOL(bdi_destroy);
468
c3c53206
JA
469/*
470 * For use from filesystems to quickly init and register a bdi associated
471 * with dirty writeback
472 */
b4caecd4 473int bdi_setup_and_register(struct backing_dev_info *bdi, char *name)
c3c53206 474{
c3c53206
JA
475 int err;
476
477 bdi->name = name;
b4caecd4 478 bdi->capabilities = 0;
c3c53206
JA
479 err = bdi_init(bdi);
480 if (err)
481 return err;
482
02aa2a37
KC
483 err = bdi_register(bdi, NULL, "%.28s-%ld", name,
484 atomic_long_inc_return(&bdi_seq));
c3c53206
JA
485 if (err) {
486 bdi_destroy(bdi);
487 return err;
488 }
489
490 return 0;
491}
492EXPORT_SYMBOL(bdi_setup_and_register);
493
3fcfab16
AM
494static wait_queue_head_t congestion_wqh[2] = {
495 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
496 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
497 };
0e093d99 498static atomic_t nr_bdi_congested[2];
3fcfab16 499
1faa16d2 500void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
3fcfab16 501{
4452226e 502 enum wb_state bit;
1faa16d2 503 wait_queue_head_t *wqh = &congestion_wqh[sync];
3fcfab16 504
4452226e
TH
505 bit = sync ? WB_sync_congested : WB_async_congested;
506 if (test_and_clear_bit(bit, &bdi->wb.state))
0e093d99 507 atomic_dec(&nr_bdi_congested[sync]);
4e857c58 508 smp_mb__after_atomic();
3fcfab16
AM
509 if (waitqueue_active(wqh))
510 wake_up(wqh);
511}
512EXPORT_SYMBOL(clear_bdi_congested);
513
1faa16d2 514void set_bdi_congested(struct backing_dev_info *bdi, int sync)
3fcfab16 515{
4452226e 516 enum wb_state bit;
3fcfab16 517
4452226e
TH
518 bit = sync ? WB_sync_congested : WB_async_congested;
519 if (!test_and_set_bit(bit, &bdi->wb.state))
0e093d99 520 atomic_inc(&nr_bdi_congested[sync]);
3fcfab16
AM
521}
522EXPORT_SYMBOL(set_bdi_congested);
523
524/**
525 * congestion_wait - wait for a backing_dev to become uncongested
8aa7e847 526 * @sync: SYNC or ASYNC IO
3fcfab16
AM
527 * @timeout: timeout in jiffies
528 *
529 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
530 * write congestion. If no backing_devs are congested then just wait for the
531 * next write to be completed.
532 */
8aa7e847 533long congestion_wait(int sync, long timeout)
3fcfab16
AM
534{
535 long ret;
52bb9198 536 unsigned long start = jiffies;
3fcfab16 537 DEFINE_WAIT(wait);
8aa7e847 538 wait_queue_head_t *wqh = &congestion_wqh[sync];
3fcfab16
AM
539
540 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
541 ret = io_schedule_timeout(timeout);
542 finish_wait(wqh, &wait);
52bb9198
MG
543
544 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
545 jiffies_to_usecs(jiffies - start));
546
3fcfab16
AM
547 return ret;
548}
549EXPORT_SYMBOL(congestion_wait);
04fbfdc1 550
0e093d99
MG
551/**
552 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
553 * @zone: A zone to check if it is heavily congested
554 * @sync: SYNC or ASYNC IO
555 * @timeout: timeout in jiffies
556 *
557 * In the event of a congested backing_dev (any backing_dev) and the given
558 * @zone has experienced recent congestion, this waits for up to @timeout
559 * jiffies for either a BDI to exit congestion of the given @sync queue
560 * or a write to complete.
561 *
25985edc 562 * In the absence of zone congestion, cond_resched() is called to yield
0e093d99
MG
563 * the processor if necessary but otherwise does not sleep.
564 *
565 * The return value is 0 if the sleep is for the full timeout. Otherwise,
566 * it is the number of jiffies that were still remaining when the function
567 * returned. return_value == timeout implies the function did not sleep.
568 */
569long wait_iff_congested(struct zone *zone, int sync, long timeout)
570{
571 long ret;
572 unsigned long start = jiffies;
573 DEFINE_WAIT(wait);
574 wait_queue_head_t *wqh = &congestion_wqh[sync];
575
576 /*
577 * If there is no congestion, or heavy congestion is not being
578 * encountered in the current zone, yield if necessary instead
579 * of sleeping on the congestion queue
580 */
581 if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
57054651 582 !test_bit(ZONE_CONGESTED, &zone->flags)) {
0e093d99
MG
583 cond_resched();
584
585 /* In case we scheduled, work out time remaining */
586 ret = timeout - (jiffies - start);
587 if (ret < 0)
588 ret = 0;
589
590 goto out;
591 }
592
593 /* Sleep until uncongested or a write happens */
594 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
595 ret = io_schedule_timeout(timeout);
596 finish_wait(wqh, &wait);
597
598out:
599 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
600 jiffies_to_usecs(jiffies - start));
601
602 return ret;
603}
604EXPORT_SYMBOL(wait_iff_congested);
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605
606int pdflush_proc_obsolete(struct ctl_table *table, int write,
607 void __user *buffer, size_t *lenp, loff_t *ppos)
608{
609 char kbuf[] = "0\n";
610
4c3bffc2 611 if (*ppos || *lenp < sizeof(kbuf)) {
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612 *lenp = 0;
613 return 0;
614 }
615
616 if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
617 return -EFAULT;
618 printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
619 table->procname);
620
621 *lenp = 2;
622 *ppos += *lenp;
623 return 2;
624}