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