writeback: separate out include/linux/backing-dev-defs.h
[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
5129a469
JE
17struct backing_dev_info noop_backing_dev_info = {
18 .name = "noop",
976e48f8 19 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
5129a469 20};
5129a469 21
cf0ca9fe 22static struct class *bdi_class;
cfc4ba53
JA
23
24/*
181387da 25 * bdi_lock protects updates to bdi_list. bdi_list has RCU reader side
cfc4ba53
JA
26 * locking.
27 */
03ba3782 28DEFINE_SPINLOCK(bdi_lock);
66f3b8e2 29LIST_HEAD(bdi_list);
03ba3782 30
839a8e86
TH
31/* bdi_wq serves all asynchronous writeback tasks */
32struct workqueue_struct *bdi_wq;
33
76f1418b
MS
34#ifdef CONFIG_DEBUG_FS
35#include <linux/debugfs.h>
36#include <linux/seq_file.h>
37
38static struct dentry *bdi_debug_root;
39
40static void bdi_debug_init(void)
41{
42 bdi_debug_root = debugfs_create_dir("bdi", NULL);
43}
44
45static int bdi_debug_stats_show(struct seq_file *m, void *v)
46{
47 struct backing_dev_info *bdi = m->private;
c1955ce3 48 struct bdi_writeback *wb = &bdi->wb;
364aeb28
DR
49 unsigned long background_thresh;
50 unsigned long dirty_thresh;
51 unsigned long bdi_thresh;
0ae45f63 52 unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
f09b00d3
JA
53 struct inode *inode;
54
0ae45f63 55 nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
f758eeab 56 spin_lock(&wb->list_lock);
7ccf19a8 57 list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
c1955ce3 58 nr_dirty++;
7ccf19a8 59 list_for_each_entry(inode, &wb->b_io, i_wb_list)
c1955ce3 60 nr_io++;
7ccf19a8 61 list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
c1955ce3 62 nr_more_io++;
0ae45f63
TT
63 list_for_each_entry(inode, &wb->b_dirty_time, i_wb_list)
64 if (inode->i_state & I_DIRTY_TIME)
65 nr_dirty_time++;
f758eeab 66 spin_unlock(&wb->list_lock);
76f1418b 67
16c4042f 68 global_dirty_limits(&background_thresh, &dirty_thresh);
a88a341a 69 bdi_thresh = wb_dirty_limit(wb, dirty_thresh);
76f1418b
MS
70
71#define K(x) ((x) << (PAGE_SHIFT - 10))
72 seq_printf(m,
00821b00
WF
73 "BdiWriteback: %10lu kB\n"
74 "BdiReclaimable: %10lu kB\n"
75 "BdiDirtyThresh: %10lu kB\n"
76 "DirtyThresh: %10lu kB\n"
77 "BackgroundThresh: %10lu kB\n"
c8e28ce0 78 "BdiDirtied: %10lu kB\n"
00821b00
WF
79 "BdiWritten: %10lu kB\n"
80 "BdiWriteBandwidth: %10lu kBps\n"
81 "b_dirty: %10lu\n"
82 "b_io: %10lu\n"
83 "b_more_io: %10lu\n"
0ae45f63 84 "b_dirty_time: %10lu\n"
00821b00
WF
85 "bdi_list: %10u\n"
86 "state: %10lx\n",
93f78d88
TH
87 (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
88 (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
f7d2b1ec
JK
89 K(bdi_thresh),
90 K(dirty_thresh),
91 K(background_thresh),
93f78d88
TH
92 (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
93 (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
a88a341a 94 (unsigned long) K(wb->write_bandwidth),
f7d2b1ec
JK
95 nr_dirty,
96 nr_io,
97 nr_more_io,
0ae45f63 98 nr_dirty_time,
4452226e 99 !list_empty(&bdi->bdi_list), bdi->wb.state);
76f1418b
MS
100#undef K
101
102 return 0;
103}
104
105static int bdi_debug_stats_open(struct inode *inode, struct file *file)
106{
107 return single_open(file, bdi_debug_stats_show, inode->i_private);
108}
109
110static const struct file_operations bdi_debug_stats_fops = {
111 .open = bdi_debug_stats_open,
112 .read = seq_read,
113 .llseek = seq_lseek,
114 .release = single_release,
115};
116
117static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
118{
119 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
120 bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
121 bdi, &bdi_debug_stats_fops);
122}
123
124static void bdi_debug_unregister(struct backing_dev_info *bdi)
125{
126 debugfs_remove(bdi->debug_stats);
127 debugfs_remove(bdi->debug_dir);
128}
129#else
130static inline void bdi_debug_init(void)
131{
132}
133static inline void bdi_debug_register(struct backing_dev_info *bdi,
134 const char *name)
135{
136}
137static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
138{
139}
140#endif
141
cf0ca9fe
PZ
142static ssize_t read_ahead_kb_store(struct device *dev,
143 struct device_attribute *attr,
144 const char *buf, size_t count)
145{
146 struct backing_dev_info *bdi = dev_get_drvdata(dev);
cf0ca9fe 147 unsigned long read_ahead_kb;
7034ed13 148 ssize_t ret;
cf0ca9fe 149
7034ed13
NJ
150 ret = kstrtoul(buf, 10, &read_ahead_kb);
151 if (ret < 0)
152 return ret;
153
154 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
155
156 return count;
cf0ca9fe
PZ
157}
158
159#define K(pages) ((pages) << (PAGE_SHIFT - 10))
160
161#define BDI_SHOW(name, expr) \
162static ssize_t name##_show(struct device *dev, \
163 struct device_attribute *attr, char *page) \
164{ \
165 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
166 \
167 return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
d9e1241e
GKH
168} \
169static DEVICE_ATTR_RW(name);
cf0ca9fe
PZ
170
171BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
172
189d3c4a
PZ
173static ssize_t min_ratio_store(struct device *dev,
174 struct device_attribute *attr, const char *buf, size_t count)
175{
176 struct backing_dev_info *bdi = dev_get_drvdata(dev);
189d3c4a 177 unsigned int ratio;
7034ed13
NJ
178 ssize_t ret;
179
180 ret = kstrtouint(buf, 10, &ratio);
181 if (ret < 0)
182 return ret;
183
184 ret = bdi_set_min_ratio(bdi, ratio);
185 if (!ret)
186 ret = count;
189d3c4a 187
189d3c4a
PZ
188 return ret;
189}
190BDI_SHOW(min_ratio, bdi->min_ratio)
191
a42dde04
PZ
192static ssize_t max_ratio_store(struct device *dev,
193 struct device_attribute *attr, const char *buf, size_t count)
194{
195 struct backing_dev_info *bdi = dev_get_drvdata(dev);
a42dde04 196 unsigned int ratio;
7034ed13
NJ
197 ssize_t ret;
198
199 ret = kstrtouint(buf, 10, &ratio);
200 if (ret < 0)
201 return ret;
202
203 ret = bdi_set_max_ratio(bdi, ratio);
204 if (!ret)
205 ret = count;
a42dde04 206
a42dde04
PZ
207 return ret;
208}
209BDI_SHOW(max_ratio, bdi->max_ratio)
210
7d311cda
DW
211static ssize_t stable_pages_required_show(struct device *dev,
212 struct device_attribute *attr,
213 char *page)
214{
215 struct backing_dev_info *bdi = dev_get_drvdata(dev);
216
217 return snprintf(page, PAGE_SIZE-1, "%d\n",
218 bdi_cap_stable_pages_required(bdi) ? 1 : 0);
219}
d9e1241e
GKH
220static DEVICE_ATTR_RO(stable_pages_required);
221
222static struct attribute *bdi_dev_attrs[] = {
223 &dev_attr_read_ahead_kb.attr,
224 &dev_attr_min_ratio.attr,
225 &dev_attr_max_ratio.attr,
226 &dev_attr_stable_pages_required.attr,
227 NULL,
cf0ca9fe 228};
d9e1241e 229ATTRIBUTE_GROUPS(bdi_dev);
cf0ca9fe
PZ
230
231static __init int bdi_class_init(void)
232{
233 bdi_class = class_create(THIS_MODULE, "bdi");
14421453
AB
234 if (IS_ERR(bdi_class))
235 return PTR_ERR(bdi_class);
236
d9e1241e 237 bdi_class->dev_groups = bdi_dev_groups;
76f1418b 238 bdi_debug_init();
cf0ca9fe
PZ
239 return 0;
240}
76f1418b 241postcore_initcall(bdi_class_init);
cf0ca9fe 242
26160158
JA
243static int __init default_bdi_init(void)
244{
245 int err;
246
839a8e86 247 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE |
b5c872dd 248 WQ_UNBOUND | WQ_SYSFS, 0);
839a8e86
TH
249 if (!bdi_wq)
250 return -ENOMEM;
251
976e48f8 252 err = bdi_init(&noop_backing_dev_info);
26160158
JA
253
254 return err;
255}
256subsys_initcall(default_bdi_init);
257
03ba3782
JA
258int bdi_has_dirty_io(struct backing_dev_info *bdi)
259{
260 return wb_has_dirty_io(&bdi->wb);
261}
262
6467716a 263/*
f0054bb1 264 * This function is used when the first inode for this wb is marked dirty. It
6467716a
AB
265 * wakes-up the corresponding bdi thread which should then take care of the
266 * periodic background write-out of dirty inodes. Since the write-out would
267 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
268 * set up a timer which wakes the bdi thread up later.
269 *
270 * Note, we wouldn't bother setting up the timer, but this function is on the
271 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
272 * by delaying the wake-up.
6ca738d6
DB
273 *
274 * We have to be careful not to postpone flush work if it is scheduled for
275 * earlier. Thus we use queue_delayed_work().
6467716a 276 */
f0054bb1 277void wb_wakeup_delayed(struct bdi_writeback *wb)
6467716a
AB
278{
279 unsigned long timeout;
280
281 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
f0054bb1
TH
282 spin_lock_bh(&wb->work_lock);
283 if (test_bit(WB_registered, &wb->state))
284 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
285 spin_unlock_bh(&wb->work_lock);
03ba3782
JA
286}
287
a88a341a
TH
288/*
289 * Initial write bandwidth: 100 MB/s
290 */
291#define INIT_BW (100 << (20 - PAGE_SHIFT))
292
f0054bb1 293static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
6467716a 294{
93f78d88
TH
295 int i, err;
296
6467716a
AB
297 memset(wb, 0, sizeof(*wb));
298
299 wb->bdi = bdi;
300 wb->last_old_flush = jiffies;
301 INIT_LIST_HEAD(&wb->b_dirty);
302 INIT_LIST_HEAD(&wb->b_io);
303 INIT_LIST_HEAD(&wb->b_more_io);
0ae45f63 304 INIT_LIST_HEAD(&wb->b_dirty_time);
f758eeab 305 spin_lock_init(&wb->list_lock);
93f78d88 306
a88a341a
TH
307 wb->bw_time_stamp = jiffies;
308 wb->balanced_dirty_ratelimit = INIT_BW;
309 wb->dirty_ratelimit = INIT_BW;
310 wb->write_bandwidth = INIT_BW;
311 wb->avg_write_bandwidth = INIT_BW;
312
f0054bb1
TH
313 spin_lock_init(&wb->work_lock);
314 INIT_LIST_HEAD(&wb->work_list);
315 INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
316
a88a341a
TH
317 err = fprop_local_init_percpu(&wb->completions, GFP_KERNEL);
318 if (err)
319 return err;
320
93f78d88
TH
321 for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
322 err = percpu_counter_init(&wb->stat[i], 0, GFP_KERNEL);
323 if (err) {
324 while (--i)
325 percpu_counter_destroy(&wb->stat[i]);
a88a341a 326 fprop_local_destroy_percpu(&wb->completions);
93f78d88
TH
327 return err;
328 }
329 }
330
331 return 0;
332}
333
46100071
TH
334/*
335 * Remove bdi from the global list and shutdown any threads we have running
336 */
337static void wb_shutdown(struct bdi_writeback *wb)
338{
339 /* Make sure nobody queues further work */
340 spin_lock_bh(&wb->work_lock);
341 if (!test_and_clear_bit(WB_registered, &wb->state)) {
342 spin_unlock_bh(&wb->work_lock);
343 return;
344 }
345 spin_unlock_bh(&wb->work_lock);
346
347 /*
348 * Drain work list and shutdown the delayed_work. !WB_registered
349 * tells wb_workfn() that @wb is dying and its work_list needs to
350 * be drained no matter what.
351 */
352 mod_delayed_work(bdi_wq, &wb->dwork, 0);
353 flush_delayed_work(&wb->dwork);
354 WARN_ON(!list_empty(&wb->work_list));
355}
356
f0054bb1 357static void wb_exit(struct bdi_writeback *wb)
93f78d88
TH
358{
359 int i;
360
361 WARN_ON(delayed_work_pending(&wb->dwork));
362
363 for (i = 0; i < NR_WB_STAT_ITEMS; i++)
364 percpu_counter_destroy(&wb->stat[i]);
6467716a 365
a88a341a
TH
366 fprop_local_destroy_percpu(&wb->completions);
367}
e98be2d5 368
b2e8fb6e
PZ
369int bdi_init(struct backing_dev_info *bdi)
370{
93f78d88 371 int err;
b2e8fb6e 372
cf0ca9fe
PZ
373 bdi->dev = NULL;
374
189d3c4a 375 bdi->min_ratio = 0;
a42dde04 376 bdi->max_ratio = 100;
eb608e3a 377 bdi->max_prop_frac = FPROP_FRAC_BASE;
66f3b8e2 378 INIT_LIST_HEAD(&bdi->bdi_list);
03ba3782 379
f0054bb1 380 err = wb_init(&bdi->wb, bdi);
93f78d88
TH
381 if (err)
382 return err;
04fbfdc1 383
93f78d88 384 return 0;
b2e8fb6e
PZ
385}
386EXPORT_SYMBOL(bdi_init);
387
46100071
TH
388int bdi_register(struct backing_dev_info *bdi, struct device *parent,
389 const char *fmt, ...)
390{
391 va_list args;
392 struct device *dev;
393
394 if (bdi->dev) /* The driver needs to use separate queues per device */
395 return 0;
396
397 va_start(args, fmt);
398 dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
399 va_end(args);
400 if (IS_ERR(dev))
401 return PTR_ERR(dev);
402
403 bdi->dev = dev;
404
405 bdi_debug_register(bdi, dev_name(dev));
406 set_bit(WB_registered, &bdi->wb.state);
407
408 spin_lock_bh(&bdi_lock);
409 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
410 spin_unlock_bh(&bdi_lock);
411
412 trace_writeback_bdi_register(bdi);
413 return 0;
414}
415EXPORT_SYMBOL(bdi_register);
416
417int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
418{
419 return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
420}
421EXPORT_SYMBOL(bdi_register_dev);
422
423/*
424 * Remove bdi from bdi_list, and ensure that it is no longer visible
425 */
426static void bdi_remove_from_list(struct backing_dev_info *bdi)
427{
428 spin_lock_bh(&bdi_lock);
429 list_del_rcu(&bdi->bdi_list);
430 spin_unlock_bh(&bdi_lock);
431
432 synchronize_rcu_expedited();
433}
434
435/*
436 * Called when the device behind @bdi has been removed or ejected.
437 *
438 * We can't really do much here except for reducing the dirty ratio at
439 * the moment. In the future we should be able to set a flag so that
440 * the filesystem can handle errors at mark_inode_dirty time instead
441 * of only at writeback time.
442 */
443void bdi_unregister(struct backing_dev_info *bdi)
444{
445 if (WARN_ON_ONCE(!bdi->dev))
446 return;
447
448 bdi_set_min_ratio(bdi, 0);
449}
450EXPORT_SYMBOL(bdi_unregister);
451
b2e8fb6e
PZ
452void bdi_destroy(struct backing_dev_info *bdi)
453{
f0054bb1
TH
454 /* make sure nobody finds us on the bdi_list anymore */
455 bdi_remove_from_list(bdi);
456 wb_shutdown(&bdi->wb);
7a401a97 457
c4db59d3
CH
458 if (bdi->dev) {
459 bdi_debug_unregister(bdi);
460 device_unregister(bdi->dev);
461 bdi->dev = NULL;
462 }
463
f0054bb1 464 wb_exit(&bdi->wb);
b2e8fb6e
PZ
465}
466EXPORT_SYMBOL(bdi_destroy);
467
c3c53206
JA
468/*
469 * For use from filesystems to quickly init and register a bdi associated
470 * with dirty writeback
471 */
b4caecd4 472int bdi_setup_and_register(struct backing_dev_info *bdi, char *name)
c3c53206 473{
c3c53206
JA
474 int err;
475
476 bdi->name = name;
b4caecd4 477 bdi->capabilities = 0;
c3c53206
JA
478 err = bdi_init(bdi);
479 if (err)
480 return err;
481
02aa2a37
KC
482 err = bdi_register(bdi, NULL, "%.28s-%ld", name,
483 atomic_long_inc_return(&bdi_seq));
c3c53206
JA
484 if (err) {
485 bdi_destroy(bdi);
486 return err;
487 }
488
489 return 0;
490}
491EXPORT_SYMBOL(bdi_setup_and_register);
492
3fcfab16
AM
493static wait_queue_head_t congestion_wqh[2] = {
494 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
495 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
496 };
0e093d99 497static atomic_t nr_bdi_congested[2];
3fcfab16 498
1faa16d2 499void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
3fcfab16 500{
4452226e 501 enum wb_state bit;
1faa16d2 502 wait_queue_head_t *wqh = &congestion_wqh[sync];
3fcfab16 503
4452226e
TH
504 bit = sync ? WB_sync_congested : WB_async_congested;
505 if (test_and_clear_bit(bit, &bdi->wb.state))
0e093d99 506 atomic_dec(&nr_bdi_congested[sync]);
4e857c58 507 smp_mb__after_atomic();
3fcfab16
AM
508 if (waitqueue_active(wqh))
509 wake_up(wqh);
510}
511EXPORT_SYMBOL(clear_bdi_congested);
512
1faa16d2 513void set_bdi_congested(struct backing_dev_info *bdi, int sync)
3fcfab16 514{
4452226e 515 enum wb_state bit;
3fcfab16 516
4452226e
TH
517 bit = sync ? WB_sync_congested : WB_async_congested;
518 if (!test_and_set_bit(bit, &bdi->wb.state))
0e093d99 519 atomic_inc(&nr_bdi_congested[sync]);
3fcfab16
AM
520}
521EXPORT_SYMBOL(set_bdi_congested);
522
523/**
524 * congestion_wait - wait for a backing_dev to become uncongested
8aa7e847 525 * @sync: SYNC or ASYNC IO
3fcfab16
AM
526 * @timeout: timeout in jiffies
527 *
528 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
529 * write congestion. If no backing_devs are congested then just wait for the
530 * next write to be completed.
531 */
8aa7e847 532long congestion_wait(int sync, long timeout)
3fcfab16
AM
533{
534 long ret;
52bb9198 535 unsigned long start = jiffies;
3fcfab16 536 DEFINE_WAIT(wait);
8aa7e847 537 wait_queue_head_t *wqh = &congestion_wqh[sync];
3fcfab16
AM
538
539 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
540 ret = io_schedule_timeout(timeout);
541 finish_wait(wqh, &wait);
52bb9198
MG
542
543 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
544 jiffies_to_usecs(jiffies - start));
545
3fcfab16
AM
546 return ret;
547}
548EXPORT_SYMBOL(congestion_wait);
04fbfdc1 549
0e093d99
MG
550/**
551 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
552 * @zone: A zone to check if it is heavily congested
553 * @sync: SYNC or ASYNC IO
554 * @timeout: timeout in jiffies
555 *
556 * In the event of a congested backing_dev (any backing_dev) and the given
557 * @zone has experienced recent congestion, this waits for up to @timeout
558 * jiffies for either a BDI to exit congestion of the given @sync queue
559 * or a write to complete.
560 *
25985edc 561 * In the absence of zone congestion, cond_resched() is called to yield
0e093d99
MG
562 * the processor if necessary but otherwise does not sleep.
563 *
564 * The return value is 0 if the sleep is for the full timeout. Otherwise,
565 * it is the number of jiffies that were still remaining when the function
566 * returned. return_value == timeout implies the function did not sleep.
567 */
568long wait_iff_congested(struct zone *zone, int sync, long timeout)
569{
570 long ret;
571 unsigned long start = jiffies;
572 DEFINE_WAIT(wait);
573 wait_queue_head_t *wqh = &congestion_wqh[sync];
574
575 /*
576 * If there is no congestion, or heavy congestion is not being
577 * encountered in the current zone, yield if necessary instead
578 * of sleeping on the congestion queue
579 */
580 if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
57054651 581 !test_bit(ZONE_CONGESTED, &zone->flags)) {
0e093d99
MG
582 cond_resched();
583
584 /* In case we scheduled, work out time remaining */
585 ret = timeout - (jiffies - start);
586 if (ret < 0)
587 ret = 0;
588
589 goto out;
590 }
591
592 /* Sleep until uncongested or a write happens */
593 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
594 ret = io_schedule_timeout(timeout);
595 finish_wait(wqh, &wait);
596
597out:
598 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
599 jiffies_to_usecs(jiffies - start));
600
601 return ret;
602}
603EXPORT_SYMBOL(wait_iff_congested);
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604
605int pdflush_proc_obsolete(struct ctl_table *table, int write,
606 void __user *buffer, size_t *lenp, loff_t *ppos)
607{
608 char kbuf[] = "0\n";
609
4c3bffc2 610 if (*ppos || *lenp < sizeof(kbuf)) {
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611 *lenp = 0;
612 return 0;
613 }
614
615 if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
616 return -EFAULT;
617 printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
618 table->procname);
619
620 *lenp = 2;
621 *ppos += *lenp;
622 return 2;
623}