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
 15static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
 16
 17struct 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};
 23EXPORT_SYMBOL_GPL(default_backing_dev_info);
 24
 25struct backing_dev_info noop_backing_dev_info = {
 26	.name		= "noop",
 27	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
 28};
 29EXPORT_SYMBOL_GPL(noop_backing_dev_info);
 30
 31static 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 */
 38DEFINE_SPINLOCK(bdi_lock);
 39LIST_HEAD(bdi_list);
 40LIST_HEAD(bdi_pending_list);
 41
 42static struct task_struct *sync_supers_tsk;
 43static struct timer_list sync_supers_timer;
 44
 45static int bdi_sync_supers(void *);
 46static void sync_supers_timer_fn(unsigned long);
 47
 48void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
 49{
 50	if (wb1 < wb2) {
 51		spin_lock(&wb1->list_lock);
 52		spin_lock_nested(&wb2->list_lock, 1);
 53	} else {
 54		spin_lock(&wb2->list_lock);
 55		spin_lock_nested(&wb1->list_lock, 1);
 56	}
 57}
 58
 59#ifdef CONFIG_DEBUG_FS
 60#include <linux/debugfs.h>
 61#include <linux/seq_file.h>
 62
 63static struct dentry *bdi_debug_root;
 64
 65static void bdi_debug_init(void)
 66{
 67	bdi_debug_root = debugfs_create_dir("bdi", NULL);
 68}
 69
 70static int bdi_debug_stats_show(struct seq_file *m, void *v)
 71{
 72	struct backing_dev_info *bdi = m->private;
 73	struct bdi_writeback *wb = &bdi->wb;
 74	unsigned long background_thresh;
 75	unsigned long dirty_thresh;
 76	unsigned long bdi_thresh;
 77	unsigned long nr_dirty, nr_io, nr_more_io;
 78	struct inode *inode;
 79
 80	nr_dirty = nr_io = nr_more_io = 0;
 81	spin_lock(&wb->list_lock);
 82	list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
 83		nr_dirty++;
 84	list_for_each_entry(inode, &wb->b_io, i_wb_list)
 85		nr_io++;
 86	list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
 87		nr_more_io++;
 88	spin_unlock(&wb->list_lock);
 89
 90	global_dirty_limits(&background_thresh, &dirty_thresh);
 91	bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
 92
 93#define K(x) ((x) << (PAGE_SHIFT - 10))
 94	seq_printf(m,
 95		   "BdiWriteback:       %10lu kB\n"
 96		   "BdiReclaimable:     %10lu kB\n"
 97		   "BdiDirtyThresh:     %10lu kB\n"
 98		   "DirtyThresh:        %10lu kB\n"
 99		   "BackgroundThresh:   %10lu kB\n"
 
100		   "BdiWritten:         %10lu kB\n"
101		   "BdiWriteBandwidth:  %10lu kBps\n"
102		   "b_dirty:            %10lu\n"
103		   "b_io:               %10lu\n"
104		   "b_more_io:          %10lu\n"
105		   "bdi_list:           %10u\n"
106		   "state:              %10lx\n",
107		   (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
108		   (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
109		   K(bdi_thresh),
110		   K(dirty_thresh),
111		   K(background_thresh),
 
112		   (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
113		   (unsigned long) K(bdi->write_bandwidth),
114		   nr_dirty,
115		   nr_io,
116		   nr_more_io,
117		   !list_empty(&bdi->bdi_list), bdi->state);
118#undef K
119
120	return 0;
121}
122
123static int bdi_debug_stats_open(struct inode *inode, struct file *file)
124{
125	return single_open(file, bdi_debug_stats_show, inode->i_private);
126}
127
128static const struct file_operations bdi_debug_stats_fops = {
129	.open		= bdi_debug_stats_open,
130	.read		= seq_read,
131	.llseek		= seq_lseek,
132	.release	= single_release,
133};
134
135static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
136{
137	bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
138	bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
139					       bdi, &bdi_debug_stats_fops);
140}
141
142static void bdi_debug_unregister(struct backing_dev_info *bdi)
143{
144	debugfs_remove(bdi->debug_stats);
145	debugfs_remove(bdi->debug_dir);
146}
147#else
148static inline void bdi_debug_init(void)
149{
150}
151static inline void bdi_debug_register(struct backing_dev_info *bdi,
152				      const char *name)
153{
154}
155static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
156{
157}
158#endif
159
160static ssize_t read_ahead_kb_store(struct device *dev,
161				  struct device_attribute *attr,
162				  const char *buf, size_t count)
163{
164	struct backing_dev_info *bdi = dev_get_drvdata(dev);
165	char *end;
166	unsigned long read_ahead_kb;
167	ssize_t ret = -EINVAL;
168
169	read_ahead_kb = simple_strtoul(buf, &end, 10);
170	if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
171		bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
172		ret = count;
173	}
174	return ret;
 
175}
176
177#define K(pages) ((pages) << (PAGE_SHIFT - 10))
178
179#define BDI_SHOW(name, expr)						\
180static ssize_t name##_show(struct device *dev,				\
181			   struct device_attribute *attr, char *page)	\
182{									\
183	struct backing_dev_info *bdi = dev_get_drvdata(dev);		\
184									\
185	return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);	\
186}
 
187
188BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
189
190static ssize_t min_ratio_store(struct device *dev,
191		struct device_attribute *attr, const char *buf, size_t count)
192{
193	struct backing_dev_info *bdi = dev_get_drvdata(dev);
194	char *end;
195	unsigned int ratio;
196	ssize_t ret = -EINVAL;
 
 
 
 
 
 
 
 
197
198	ratio = simple_strtoul(buf, &end, 10);
199	if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
200		ret = bdi_set_min_ratio(bdi, ratio);
201		if (!ret)
202			ret = count;
203	}
204	return ret;
205}
206BDI_SHOW(min_ratio, bdi->min_ratio)
207
208static ssize_t max_ratio_store(struct device *dev,
209		struct device_attribute *attr, const char *buf, size_t count)
210{
211	struct backing_dev_info *bdi = dev_get_drvdata(dev);
212	char *end;
213	unsigned int ratio;
214	ssize_t ret = -EINVAL;
 
 
 
 
 
 
 
 
215
216	ratio = simple_strtoul(buf, &end, 10);
217	if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
218		ret = bdi_set_max_ratio(bdi, ratio);
219		if (!ret)
220			ret = count;
221	}
222	return ret;
223}
224BDI_SHOW(max_ratio, bdi->max_ratio)
225
226#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
 
 
 
 
 
 
 
 
 
227
228static struct device_attribute bdi_dev_attrs[] = {
229	__ATTR_RW(read_ahead_kb),
230	__ATTR_RW(min_ratio),
231	__ATTR_RW(max_ratio),
232	__ATTR_NULL,
 
233};
 
234
235static __init int bdi_class_init(void)
236{
237	bdi_class = class_create(THIS_MODULE, "bdi");
238	if (IS_ERR(bdi_class))
239		return PTR_ERR(bdi_class);
240
241	bdi_class->dev_attrs = bdi_dev_attrs;
242	bdi_debug_init();
243	return 0;
244}
245postcore_initcall(bdi_class_init);
246
247static int __init default_bdi_init(void)
248{
249	int err;
250
251	sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
252	BUG_ON(IS_ERR(sync_supers_tsk));
253
254	setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
255	bdi_arm_supers_timer();
256
257	err = bdi_init(&default_backing_dev_info);
258	if (!err)
259		bdi_register(&default_backing_dev_info, NULL, "default");
260	err = bdi_init(&noop_backing_dev_info);
261
262	return err;
263}
264subsys_initcall(default_bdi_init);
265
266int bdi_has_dirty_io(struct backing_dev_info *bdi)
267{
268	return wb_has_dirty_io(&bdi->wb);
269}
270
271/*
272 * kupdated() used to do this. We cannot do it from the bdi_forker_thread()
273 * or we risk deadlocking on ->s_umount. The longer term solution would be
274 * to implement sync_supers_bdi() or similar and simply do it from the
275 * bdi writeback thread individually.
276 */
277static int bdi_sync_supers(void *unused)
278{
279	set_user_nice(current, 0);
280
281	while (!kthread_should_stop()) {
282		set_current_state(TASK_INTERRUPTIBLE);
283		schedule();
284
285		/*
286		 * Do this periodically, like kupdated() did before.
287		 */
288		sync_supers();
289	}
290
291	return 0;
292}
293
294void bdi_arm_supers_timer(void)
295{
296	unsigned long next;
297
298	if (!dirty_writeback_interval)
299		return;
300
301	next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
302	mod_timer(&sync_supers_timer, round_jiffies_up(next));
303}
304
305static void sync_supers_timer_fn(unsigned long unused)
306{
307	wake_up_process(sync_supers_tsk);
308	bdi_arm_supers_timer();
309}
310
311static void wakeup_timer_fn(unsigned long data)
312{
313	struct backing_dev_info *bdi = (struct backing_dev_info *)data;
314
315	spin_lock_bh(&bdi->wb_lock);
316	if (bdi->wb.task) {
317		trace_writeback_wake_thread(bdi);
318		wake_up_process(bdi->wb.task);
319	} else {
320		/*
321		 * When bdi tasks are inactive for long time, they are killed.
322		 * In this case we have to wake-up the forker thread which
323		 * should create and run the bdi thread.
324		 */
325		trace_writeback_wake_forker_thread(bdi);
326		wake_up_process(default_backing_dev_info.wb.task);
327	}
328	spin_unlock_bh(&bdi->wb_lock);
329}
330
331/*
332 * This function is used when the first inode for this bdi is marked dirty. It
333 * wakes-up the corresponding bdi thread which should then take care of the
334 * periodic background write-out of dirty inodes. Since the write-out would
335 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
336 * set up a timer which wakes the bdi thread up later.
337 *
338 * Note, we wouldn't bother setting up the timer, but this function is on the
339 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
340 * by delaying the wake-up.
 
 
 
341 */
342void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
343{
344	unsigned long timeout;
345
346	timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
347	mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout);
348}
349
350/*
351 * Calculate the longest interval (jiffies) bdi threads are allowed to be
352 * inactive.
353 */
354static unsigned long bdi_longest_inactive(void)
355{
356	unsigned long interval;
357
358	interval = msecs_to_jiffies(dirty_writeback_interval * 10);
359	return max(5UL * 60 * HZ, interval);
360}
361
362/*
363 * Clear pending bit and wakeup anybody waiting for flusher thread creation or
364 * shutdown
365 */
366static void bdi_clear_pending(struct backing_dev_info *bdi)
367{
368	clear_bit(BDI_pending, &bdi->state);
369	smp_mb__after_clear_bit();
370	wake_up_bit(&bdi->state, BDI_pending);
371}
372
373static int bdi_forker_thread(void *ptr)
374{
375	struct bdi_writeback *me = ptr;
376
377	current->flags |= PF_SWAPWRITE;
378	set_freezable();
379
380	/*
381	 * Our parent may run at a different priority, just set us to normal
382	 */
383	set_user_nice(current, 0);
384
385	for (;;) {
386		struct task_struct *task = NULL;
387		struct backing_dev_info *bdi;
388		enum {
389			NO_ACTION,   /* Nothing to do */
390			FORK_THREAD, /* Fork bdi thread */
391			KILL_THREAD, /* Kill inactive bdi thread */
392		} action = NO_ACTION;
393
394		/*
395		 * Temporary measure, we want to make sure we don't see
396		 * dirty data on the default backing_dev_info
397		 */
398		if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
399			del_timer(&me->wakeup_timer);
400			wb_do_writeback(me, 0);
401		}
402
403		spin_lock_bh(&bdi_lock);
404		/*
405		 * In the following loop we are going to check whether we have
406		 * some work to do without any synchronization with tasks
407		 * waking us up to do work for them. So we have to set task
408		 * state already here so that we don't miss wakeups coming
409		 * after we verify some condition.
410		 */
411		set_current_state(TASK_INTERRUPTIBLE);
412
413		list_for_each_entry(bdi, &bdi_list, bdi_list) {
414			bool have_dirty_io;
415
416			if (!bdi_cap_writeback_dirty(bdi) ||
417			     bdi_cap_flush_forker(bdi))
418				continue;
419
420			WARN(!test_bit(BDI_registered, &bdi->state),
421			     "bdi %p/%s is not registered!\n", bdi, bdi->name);
422
423			have_dirty_io = !list_empty(&bdi->work_list) ||
424					wb_has_dirty_io(&bdi->wb);
425
426			/*
427			 * If the bdi has work to do, but the thread does not
428			 * exist - create it.
429			 */
430			if (!bdi->wb.task && have_dirty_io) {
431				/*
432				 * Set the pending bit - if someone will try to
433				 * unregister this bdi - it'll wait on this bit.
434				 */
435				set_bit(BDI_pending, &bdi->state);
436				action = FORK_THREAD;
437				break;
438			}
439
440			spin_lock(&bdi->wb_lock);
441
442			/*
443			 * If there is no work to do and the bdi thread was
444			 * inactive long enough - kill it. The wb_lock is taken
445			 * to make sure no-one adds more work to this bdi and
446			 * wakes the bdi thread up.
447			 */
448			if (bdi->wb.task && !have_dirty_io &&
449			    time_after(jiffies, bdi->wb.last_active +
450						bdi_longest_inactive())) {
451				task = bdi->wb.task;
452				bdi->wb.task = NULL;
453				spin_unlock(&bdi->wb_lock);
454				set_bit(BDI_pending, &bdi->state);
455				action = KILL_THREAD;
456				break;
457			}
458			spin_unlock(&bdi->wb_lock);
459		}
460		spin_unlock_bh(&bdi_lock);
461
462		/* Keep working if default bdi still has things to do */
463		if (!list_empty(&me->bdi->work_list))
464			__set_current_state(TASK_RUNNING);
465
466		switch (action) {
467		case FORK_THREAD:
468			__set_current_state(TASK_RUNNING);
469			task = kthread_create(bdi_writeback_thread, &bdi->wb,
470					      "flush-%s", dev_name(bdi->dev));
471			if (IS_ERR(task)) {
472				/*
473				 * If thread creation fails, force writeout of
474				 * the bdi from the thread. Hopefully 1024 is
475				 * large enough for efficient IO.
476				 */
477				writeback_inodes_wb(&bdi->wb, 1024);
478			} else {
479				/*
480				 * The spinlock makes sure we do not lose
481				 * wake-ups when racing with 'bdi_queue_work()'.
482				 * And as soon as the bdi thread is visible, we
483				 * can start it.
484				 */
485				spin_lock_bh(&bdi->wb_lock);
486				bdi->wb.task = task;
487				spin_unlock_bh(&bdi->wb_lock);
488				wake_up_process(task);
489			}
490			bdi_clear_pending(bdi);
491			break;
492
493		case KILL_THREAD:
494			__set_current_state(TASK_RUNNING);
495			kthread_stop(task);
496			bdi_clear_pending(bdi);
497			break;
498
499		case NO_ACTION:
500			if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
501				/*
502				 * There are no dirty data. The only thing we
503				 * should now care about is checking for
504				 * inactive bdi threads and killing them. Thus,
505				 * let's sleep for longer time, save energy and
506				 * be friendly for battery-driven devices.
507				 */
508				schedule_timeout(bdi_longest_inactive());
509			else
510				schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
511			try_to_freeze();
512			break;
513		}
514	}
515
516	return 0;
517}
518
519/*
520 * Remove bdi from bdi_list, and ensure that it is no longer visible
521 */
522static void bdi_remove_from_list(struct backing_dev_info *bdi)
523{
524	spin_lock_bh(&bdi_lock);
525	list_del_rcu(&bdi->bdi_list);
526	spin_unlock_bh(&bdi_lock);
527
528	synchronize_rcu_expedited();
529}
530
531int bdi_register(struct backing_dev_info *bdi, struct device *parent,
532		const char *fmt, ...)
533{
534	va_list args;
535	struct device *dev;
536
537	if (bdi->dev)	/* The driver needs to use separate queues per device */
538		return 0;
539
540	va_start(args, fmt);
541	dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
542	va_end(args);
543	if (IS_ERR(dev))
544		return PTR_ERR(dev);
545
546	bdi->dev = dev;
547
548	/*
549	 * Just start the forker thread for our default backing_dev_info,
550	 * and add other bdi's to the list. They will get a thread created
551	 * on-demand when they need it.
552	 */
553	if (bdi_cap_flush_forker(bdi)) {
554		struct bdi_writeback *wb = &bdi->wb;
555
556		wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
557						dev_name(dev));
558		if (IS_ERR(wb->task))
559			return PTR_ERR(wb->task);
560	}
561
562	bdi_debug_register(bdi, dev_name(dev));
563	set_bit(BDI_registered, &bdi->state);
564
565	spin_lock_bh(&bdi_lock);
566	list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
567	spin_unlock_bh(&bdi_lock);
568
569	trace_writeback_bdi_register(bdi);
570	return 0;
571}
572EXPORT_SYMBOL(bdi_register);
573
574int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
575{
576	return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
577}
578EXPORT_SYMBOL(bdi_register_dev);
579
580/*
581 * Remove bdi from the global list and shutdown any threads we have running
582 */
583static void bdi_wb_shutdown(struct backing_dev_info *bdi)
584{
585	if (!bdi_cap_writeback_dirty(bdi))
586		return;
587
588	/*
589	 * Make sure nobody finds us on the bdi_list anymore
590	 */
591	bdi_remove_from_list(bdi);
592
 
 
 
 
 
593	/*
594	 * If setup is pending, wait for that to complete first
 
 
595	 */
596	wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
597			TASK_UNINTERRUPTIBLE);
 
598
599	/*
600	 * Finally, kill the kernel thread. We don't need to be RCU
601	 * safe anymore, since the bdi is gone from visibility. Force
602	 * unfreeze of the thread before calling kthread_stop(), otherwise
603	 * it would never exet if it is currently stuck in the refrigerator.
604	 */
605	if (bdi->wb.task) {
606		thaw_process(bdi->wb.task);
607		kthread_stop(bdi->wb.task);
608	}
609}
610
611/*
612 * This bdi is going away now, make sure that no super_blocks point to it
613 */
614static void bdi_prune_sb(struct backing_dev_info *bdi)
615{
616	struct super_block *sb;
617
618	spin_lock(&sb_lock);
619	list_for_each_entry(sb, &super_blocks, s_list) {
620		if (sb->s_bdi == bdi)
621			sb->s_bdi = &default_backing_dev_info;
622	}
623	spin_unlock(&sb_lock);
624}
625
626void bdi_unregister(struct backing_dev_info *bdi)
627{
628	if (bdi->dev) {
 
 
629		bdi_set_min_ratio(bdi, 0);
630		trace_writeback_bdi_unregister(bdi);
631		bdi_prune_sb(bdi);
632		del_timer_sync(&bdi->wb.wakeup_timer);
633
634		if (!bdi_cap_flush_forker(bdi))
635			bdi_wb_shutdown(bdi);
636		bdi_debug_unregister(bdi);
637		device_unregister(bdi->dev);
 
638		bdi->dev = NULL;
 
 
 
639	}
640}
641EXPORT_SYMBOL(bdi_unregister);
642
643static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
644{
645	memset(wb, 0, sizeof(*wb));
646
647	wb->bdi = bdi;
648	wb->last_old_flush = jiffies;
649	INIT_LIST_HEAD(&wb->b_dirty);
650	INIT_LIST_HEAD(&wb->b_io);
651	INIT_LIST_HEAD(&wb->b_more_io);
652	spin_lock_init(&wb->list_lock);
653	setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
654}
655
656/*
657 * Initial write bandwidth: 100 MB/s
658 */
659#define INIT_BW		(100 << (20 - PAGE_SHIFT))
660
661int bdi_init(struct backing_dev_info *bdi)
662{
663	int i, err;
664
665	bdi->dev = NULL;
666
667	bdi->min_ratio = 0;
668	bdi->max_ratio = 100;
669	bdi->max_prop_frac = PROP_FRAC_BASE;
670	spin_lock_init(&bdi->wb_lock);
671	INIT_LIST_HEAD(&bdi->bdi_list);
672	INIT_LIST_HEAD(&bdi->work_list);
673
674	bdi_wb_init(&bdi->wb, bdi);
675
676	for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
677		err = percpu_counter_init(&bdi->bdi_stat[i], 0);
678		if (err)
679			goto err;
680	}
681
682	bdi->dirty_exceeded = 0;
683
684	bdi->bw_time_stamp = jiffies;
685	bdi->written_stamp = 0;
686
 
 
687	bdi->write_bandwidth = INIT_BW;
688	bdi->avg_write_bandwidth = INIT_BW;
689
690	err = prop_local_init_percpu(&bdi->completions);
691
692	if (err) {
693err:
694		while (i--)
695			percpu_counter_destroy(&bdi->bdi_stat[i]);
696	}
697
698	return err;
699}
700EXPORT_SYMBOL(bdi_init);
701
702void bdi_destroy(struct backing_dev_info *bdi)
703{
704	int i;
705
706	/*
707	 * Splice our entries to the default_backing_dev_info, if this
708	 * bdi disappears
709	 */
710	if (bdi_has_dirty_io(bdi)) {
711		struct bdi_writeback *dst = &default_backing_dev_info.wb;
712
713		bdi_lock_two(&bdi->wb, dst);
714		list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
715		list_splice(&bdi->wb.b_io, &dst->b_io);
716		list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
717		spin_unlock(&bdi->wb.list_lock);
718		spin_unlock(&dst->list_lock);
719	}
720
721	bdi_unregister(bdi);
722
 
 
 
 
 
 
 
723	for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
724		percpu_counter_destroy(&bdi->bdi_stat[i]);
725
726	prop_local_destroy_percpu(&bdi->completions);
727}
728EXPORT_SYMBOL(bdi_destroy);
729
730/*
731 * For use from filesystems to quickly init and register a bdi associated
732 * with dirty writeback
733 */
734int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
735			   unsigned int cap)
736{
737	char tmp[32];
738	int err;
739
740	bdi->name = name;
741	bdi->capabilities = cap;
742	err = bdi_init(bdi);
743	if (err)
744		return err;
745
746	sprintf(tmp, "%.28s%s", name, "-%d");
747	err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
748	if (err) {
749		bdi_destroy(bdi);
750		return err;
751	}
752
753	return 0;
754}
755EXPORT_SYMBOL(bdi_setup_and_register);
756
757static wait_queue_head_t congestion_wqh[2] = {
758		__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
759		__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
760	};
761static atomic_t nr_bdi_congested[2];
762
763void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
764{
765	enum bdi_state bit;
766	wait_queue_head_t *wqh = &congestion_wqh[sync];
767
768	bit = sync ? BDI_sync_congested : BDI_async_congested;
769	if (test_and_clear_bit(bit, &bdi->state))
770		atomic_dec(&nr_bdi_congested[sync]);
771	smp_mb__after_clear_bit();
772	if (waitqueue_active(wqh))
773		wake_up(wqh);
774}
775EXPORT_SYMBOL(clear_bdi_congested);
776
777void set_bdi_congested(struct backing_dev_info *bdi, int sync)
778{
779	enum bdi_state bit;
780
781	bit = sync ? BDI_sync_congested : BDI_async_congested;
782	if (!test_and_set_bit(bit, &bdi->state))
783		atomic_inc(&nr_bdi_congested[sync]);
784}
785EXPORT_SYMBOL(set_bdi_congested);
786
787/**
788 * congestion_wait - wait for a backing_dev to become uncongested
789 * @sync: SYNC or ASYNC IO
790 * @timeout: timeout in jiffies
791 *
792 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
793 * write congestion.  If no backing_devs are congested then just wait for the
794 * next write to be completed.
795 */
796long congestion_wait(int sync, long timeout)
797{
798	long ret;
799	unsigned long start = jiffies;
800	DEFINE_WAIT(wait);
801	wait_queue_head_t *wqh = &congestion_wqh[sync];
802
803	prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
804	ret = io_schedule_timeout(timeout);
805	finish_wait(wqh, &wait);
806
807	trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
808					jiffies_to_usecs(jiffies - start));
809
810	return ret;
811}
812EXPORT_SYMBOL(congestion_wait);
813
814/**
815 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
816 * @zone: A zone to check if it is heavily congested
817 * @sync: SYNC or ASYNC IO
818 * @timeout: timeout in jiffies
819 *
820 * In the event of a congested backing_dev (any backing_dev) and the given
821 * @zone has experienced recent congestion, this waits for up to @timeout
822 * jiffies for either a BDI to exit congestion of the given @sync queue
823 * or a write to complete.
824 *
825 * In the absence of zone congestion, cond_resched() is called to yield
826 * the processor if necessary but otherwise does not sleep.
827 *
828 * The return value is 0 if the sleep is for the full timeout. Otherwise,
829 * it is the number of jiffies that were still remaining when the function
830 * returned. return_value == timeout implies the function did not sleep.
831 */
832long wait_iff_congested(struct zone *zone, int sync, long timeout)
833{
834	long ret;
835	unsigned long start = jiffies;
836	DEFINE_WAIT(wait);
837	wait_queue_head_t *wqh = &congestion_wqh[sync];
838
839	/*
840	 * If there is no congestion, or heavy congestion is not being
841	 * encountered in the current zone, yield if necessary instead
842	 * of sleeping on the congestion queue
843	 */
844	if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
845			!zone_is_reclaim_congested(zone)) {
846		cond_resched();
847
848		/* In case we scheduled, work out time remaining */
849		ret = timeout - (jiffies - start);
850		if (ret < 0)
851			ret = 0;
852
853		goto out;
854	}
855
856	/* Sleep until uncongested or a write happens */
857	prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
858	ret = io_schedule_timeout(timeout);
859	finish_wait(wqh, &wait);
860
861out:
862	trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
863					jiffies_to_usecs(jiffies - start));
864
865	return ret;
866}
867EXPORT_SYMBOL(wait_iff_congested);