tmpfs: convert shmem_truncate_range to radix-swap
[linux-2.6.git] / mm / backing-dev.c
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 void 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
63 static struct dentry *bdi_debug_root;
64
65 static void bdi_debug_init(void)
66 {
67         bdi_debug_root = debugfs_create_dir("bdi", NULL);
68 }
69
70 static 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
123 static 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
128 static 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
135 static 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
142 static 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
148 static inline void bdi_debug_init(void)
149 {
150 }
151 static inline void bdi_debug_register(struct backing_dev_info *bdi,
152                                       const char *name)
153 {
154 }
155 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
156 {
157 }
158 #endif
159
160 static 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)                                            \
180 static 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
188 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
189
190 static 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 }
206 BDI_SHOW(min_ratio, bdi->min_ratio)
207
208 static 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 }
224 BDI_SHOW(max_ratio, bdi->max_ratio)
225
226 #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
227
228 static 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
235 static __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 }
245 postcore_initcall(bdi_class_init);
246
247 static 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 }
264 subsys_initcall(default_bdi_init);
265
266 int 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  */
277 static 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
294 void 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
305 static void sync_supers_timer_fn(unsigned long unused)
306 {
307         wake_up_process(sync_supers_tsk);
308         bdi_arm_supers_timer();
309 }
310
311 static 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  */
342 void 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  */
354 static 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 static int bdi_forker_thread(void *ptr)
363 {
364         struct bdi_writeback *me = ptr;
365
366         current->flags |= PF_SWAPWRITE;
367         set_freezable();
368
369         /*
370          * Our parent may run at a different priority, just set us to normal
371          */
372         set_user_nice(current, 0);
373
374         for (;;) {
375                 struct task_struct *task = NULL;
376                 struct backing_dev_info *bdi;
377                 enum {
378                         NO_ACTION,   /* Nothing to do */
379                         FORK_THREAD, /* Fork bdi thread */
380                         KILL_THREAD, /* Kill inactive bdi thread */
381                 } action = NO_ACTION;
382
383                 /*
384                  * Temporary measure, we want to make sure we don't see
385                  * dirty data on the default backing_dev_info
386                  */
387                 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
388                         del_timer(&me->wakeup_timer);
389                         wb_do_writeback(me, 0);
390                 }
391
392                 spin_lock_bh(&bdi_lock);
393                 set_current_state(TASK_INTERRUPTIBLE);
394
395                 list_for_each_entry(bdi, &bdi_list, bdi_list) {
396                         bool have_dirty_io;
397
398                         if (!bdi_cap_writeback_dirty(bdi) ||
399                              bdi_cap_flush_forker(bdi))
400                                 continue;
401
402                         WARN(!test_bit(BDI_registered, &bdi->state),
403                              "bdi %p/%s is not registered!\n", bdi, bdi->name);
404
405                         have_dirty_io = !list_empty(&bdi->work_list) ||
406                                         wb_has_dirty_io(&bdi->wb);
407
408                         /*
409                          * If the bdi has work to do, but the thread does not
410                          * exist - create it.
411                          */
412                         if (!bdi->wb.task && have_dirty_io) {
413                                 /*
414                                  * Set the pending bit - if someone will try to
415                                  * unregister this bdi - it'll wait on this bit.
416                                  */
417                                 set_bit(BDI_pending, &bdi->state);
418                                 action = FORK_THREAD;
419                                 break;
420                         }
421
422                         spin_lock(&bdi->wb_lock);
423
424                         /*
425                          * If there is no work to do and the bdi thread was
426                          * inactive long enough - kill it. The wb_lock is taken
427                          * to make sure no-one adds more work to this bdi and
428                          * wakes the bdi thread up.
429                          */
430                         if (bdi->wb.task && !have_dirty_io &&
431                             time_after(jiffies, bdi->wb.last_active +
432                                                 bdi_longest_inactive())) {
433                                 task = bdi->wb.task;
434                                 bdi->wb.task = NULL;
435                                 spin_unlock(&bdi->wb_lock);
436                                 set_bit(BDI_pending, &bdi->state);
437                                 action = KILL_THREAD;
438                                 break;
439                         }
440                         spin_unlock(&bdi->wb_lock);
441                 }
442                 spin_unlock_bh(&bdi_lock);
443
444                 /* Keep working if default bdi still has things to do */
445                 if (!list_empty(&me->bdi->work_list))
446                         __set_current_state(TASK_RUNNING);
447
448                 switch (action) {
449                 case FORK_THREAD:
450                         __set_current_state(TASK_RUNNING);
451                         task = kthread_create(bdi_writeback_thread, &bdi->wb,
452                                               "flush-%s", dev_name(bdi->dev));
453                         if (IS_ERR(task)) {
454                                 /*
455                                  * If thread creation fails, force writeout of
456                                  * the bdi from the thread. Hopefully 1024 is
457                                  * large enough for efficient IO.
458                                  */
459                                 writeback_inodes_wb(&bdi->wb, 1024);
460                         } else {
461                                 /*
462                                  * The spinlock makes sure we do not lose
463                                  * wake-ups when racing with 'bdi_queue_work()'.
464                                  * And as soon as the bdi thread is visible, we
465                                  * can start it.
466                                  */
467                                 spin_lock_bh(&bdi->wb_lock);
468                                 bdi->wb.task = task;
469                                 spin_unlock_bh(&bdi->wb_lock);
470                                 wake_up_process(task);
471                         }
472                         break;
473
474                 case KILL_THREAD:
475                         __set_current_state(TASK_RUNNING);
476                         kthread_stop(task);
477                         break;
478
479                 case NO_ACTION:
480                         if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
481                                 /*
482                                  * There are no dirty data. The only thing we
483                                  * should now care about is checking for
484                                  * inactive bdi threads and killing them. Thus,
485                                  * let's sleep for longer time, save energy and
486                                  * be friendly for battery-driven devices.
487                                  */
488                                 schedule_timeout(bdi_longest_inactive());
489                         else
490                                 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
491                         try_to_freeze();
492                         /* Back to the main loop */
493                         continue;
494                 }
495
496                 /*
497                  * Clear pending bit and wakeup anybody waiting to tear us down.
498                  */
499                 clear_bit(BDI_pending, &bdi->state);
500                 smp_mb__after_clear_bit();
501                 wake_up_bit(&bdi->state, BDI_pending);
502         }
503
504         return 0;
505 }
506
507 /*
508  * Remove bdi from bdi_list, and ensure that it is no longer visible
509  */
510 static void bdi_remove_from_list(struct backing_dev_info *bdi)
511 {
512         spin_lock_bh(&bdi_lock);
513         list_del_rcu(&bdi->bdi_list);
514         spin_unlock_bh(&bdi_lock);
515
516         synchronize_rcu_expedited();
517 }
518
519 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
520                 const char *fmt, ...)
521 {
522         va_list args;
523         struct device *dev;
524
525         if (bdi->dev)   /* The driver needs to use separate queues per device */
526                 return 0;
527
528         va_start(args, fmt);
529         dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
530         va_end(args);
531         if (IS_ERR(dev))
532                 return PTR_ERR(dev);
533
534         bdi->dev = dev;
535
536         /*
537          * Just start the forker thread for our default backing_dev_info,
538          * and add other bdi's to the list. They will get a thread created
539          * on-demand when they need it.
540          */
541         if (bdi_cap_flush_forker(bdi)) {
542                 struct bdi_writeback *wb = &bdi->wb;
543
544                 wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
545                                                 dev_name(dev));
546                 if (IS_ERR(wb->task))
547                         return PTR_ERR(wb->task);
548         }
549
550         bdi_debug_register(bdi, dev_name(dev));
551         set_bit(BDI_registered, &bdi->state);
552
553         spin_lock_bh(&bdi_lock);
554         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
555         spin_unlock_bh(&bdi_lock);
556
557         trace_writeback_bdi_register(bdi);
558         return 0;
559 }
560 EXPORT_SYMBOL(bdi_register);
561
562 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
563 {
564         return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
565 }
566 EXPORT_SYMBOL(bdi_register_dev);
567
568 /*
569  * Remove bdi from the global list and shutdown any threads we have running
570  */
571 static void bdi_wb_shutdown(struct backing_dev_info *bdi)
572 {
573         if (!bdi_cap_writeback_dirty(bdi))
574                 return;
575
576         /*
577          * Make sure nobody finds us on the bdi_list anymore
578          */
579         bdi_remove_from_list(bdi);
580
581         /*
582          * If setup is pending, wait for that to complete first
583          */
584         wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
585                         TASK_UNINTERRUPTIBLE);
586
587         /*
588          * Finally, kill the kernel thread. We don't need to be RCU
589          * safe anymore, since the bdi is gone from visibility. Force
590          * unfreeze of the thread before calling kthread_stop(), otherwise
591          * it would never exet if it is currently stuck in the refrigerator.
592          */
593         if (bdi->wb.task) {
594                 thaw_process(bdi->wb.task);
595                 kthread_stop(bdi->wb.task);
596         }
597 }
598
599 /*
600  * This bdi is going away now, make sure that no super_blocks point to it
601  */
602 static void bdi_prune_sb(struct backing_dev_info *bdi)
603 {
604         struct super_block *sb;
605
606         spin_lock(&sb_lock);
607         list_for_each_entry(sb, &super_blocks, s_list) {
608                 if (sb->s_bdi == bdi)
609                         sb->s_bdi = &default_backing_dev_info;
610         }
611         spin_unlock(&sb_lock);
612 }
613
614 void bdi_unregister(struct backing_dev_info *bdi)
615 {
616         if (bdi->dev) {
617                 bdi_set_min_ratio(bdi, 0);
618                 trace_writeback_bdi_unregister(bdi);
619                 bdi_prune_sb(bdi);
620                 del_timer_sync(&bdi->wb.wakeup_timer);
621
622                 if (!bdi_cap_flush_forker(bdi))
623                         bdi_wb_shutdown(bdi);
624                 bdi_debug_unregister(bdi);
625                 device_unregister(bdi->dev);
626                 bdi->dev = NULL;
627         }
628 }
629 EXPORT_SYMBOL(bdi_unregister);
630
631 static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
632 {
633         memset(wb, 0, sizeof(*wb));
634
635         wb->bdi = bdi;
636         wb->last_old_flush = jiffies;
637         INIT_LIST_HEAD(&wb->b_dirty);
638         INIT_LIST_HEAD(&wb->b_io);
639         INIT_LIST_HEAD(&wb->b_more_io);
640         spin_lock_init(&wb->list_lock);
641         setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
642 }
643
644 /*
645  * Initial write bandwidth: 100 MB/s
646  */
647 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
648
649 int bdi_init(struct backing_dev_info *bdi)
650 {
651         int i, err;
652
653         bdi->dev = NULL;
654
655         bdi->min_ratio = 0;
656         bdi->max_ratio = 100;
657         bdi->max_prop_frac = PROP_FRAC_BASE;
658         spin_lock_init(&bdi->wb_lock);
659         INIT_LIST_HEAD(&bdi->bdi_list);
660         INIT_LIST_HEAD(&bdi->work_list);
661
662         bdi_wb_init(&bdi->wb, bdi);
663
664         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
665                 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
666                 if (err)
667                         goto err;
668         }
669
670         bdi->dirty_exceeded = 0;
671
672         bdi->bw_time_stamp = jiffies;
673         bdi->written_stamp = 0;
674
675         bdi->write_bandwidth = INIT_BW;
676         bdi->avg_write_bandwidth = INIT_BW;
677
678         err = prop_local_init_percpu(&bdi->completions);
679
680         if (err) {
681 err:
682                 while (i--)
683                         percpu_counter_destroy(&bdi->bdi_stat[i]);
684         }
685
686         return err;
687 }
688 EXPORT_SYMBOL(bdi_init);
689
690 void bdi_destroy(struct backing_dev_info *bdi)
691 {
692         int i;
693
694         /*
695          * Splice our entries to the default_backing_dev_info, if this
696          * bdi disappears
697          */
698         if (bdi_has_dirty_io(bdi)) {
699                 struct bdi_writeback *dst = &default_backing_dev_info.wb;
700
701                 bdi_lock_two(&bdi->wb, dst);
702                 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
703                 list_splice(&bdi->wb.b_io, &dst->b_io);
704                 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
705                 spin_unlock(&bdi->wb.list_lock);
706                 spin_unlock(&dst->list_lock);
707         }
708
709         bdi_unregister(bdi);
710
711         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
712                 percpu_counter_destroy(&bdi->bdi_stat[i]);
713
714         prop_local_destroy_percpu(&bdi->completions);
715 }
716 EXPORT_SYMBOL(bdi_destroy);
717
718 /*
719  * For use from filesystems to quickly init and register a bdi associated
720  * with dirty writeback
721  */
722 int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
723                            unsigned int cap)
724 {
725         char tmp[32];
726         int err;
727
728         bdi->name = name;
729         bdi->capabilities = cap;
730         err = bdi_init(bdi);
731         if (err)
732                 return err;
733
734         sprintf(tmp, "%.28s%s", name, "-%d");
735         err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
736         if (err) {
737                 bdi_destroy(bdi);
738                 return err;
739         }
740
741         return 0;
742 }
743 EXPORT_SYMBOL(bdi_setup_and_register);
744
745 static wait_queue_head_t congestion_wqh[2] = {
746                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
747                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
748         };
749 static atomic_t nr_bdi_congested[2];
750
751 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
752 {
753         enum bdi_state bit;
754         wait_queue_head_t *wqh = &congestion_wqh[sync];
755
756         bit = sync ? BDI_sync_congested : BDI_async_congested;
757         if (test_and_clear_bit(bit, &bdi->state))
758                 atomic_dec(&nr_bdi_congested[sync]);
759         smp_mb__after_clear_bit();
760         if (waitqueue_active(wqh))
761                 wake_up(wqh);
762 }
763 EXPORT_SYMBOL(clear_bdi_congested);
764
765 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
766 {
767         enum bdi_state bit;
768
769         bit = sync ? BDI_sync_congested : BDI_async_congested;
770         if (!test_and_set_bit(bit, &bdi->state))
771                 atomic_inc(&nr_bdi_congested[sync]);
772 }
773 EXPORT_SYMBOL(set_bdi_congested);
774
775 /**
776  * congestion_wait - wait for a backing_dev to become uncongested
777  * @sync: SYNC or ASYNC IO
778  * @timeout: timeout in jiffies
779  *
780  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
781  * write congestion.  If no backing_devs are congested then just wait for the
782  * next write to be completed.
783  */
784 long congestion_wait(int sync, long timeout)
785 {
786         long ret;
787         unsigned long start = jiffies;
788         DEFINE_WAIT(wait);
789         wait_queue_head_t *wqh = &congestion_wqh[sync];
790
791         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
792         ret = io_schedule_timeout(timeout);
793         finish_wait(wqh, &wait);
794
795         trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
796                                         jiffies_to_usecs(jiffies - start));
797
798         return ret;
799 }
800 EXPORT_SYMBOL(congestion_wait);
801
802 /**
803  * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
804  * @zone: A zone to check if it is heavily congested
805  * @sync: SYNC or ASYNC IO
806  * @timeout: timeout in jiffies
807  *
808  * In the event of a congested backing_dev (any backing_dev) and the given
809  * @zone has experienced recent congestion, this waits for up to @timeout
810  * jiffies for either a BDI to exit congestion of the given @sync queue
811  * or a write to complete.
812  *
813  * In the absence of zone congestion, cond_resched() is called to yield
814  * the processor if necessary but otherwise does not sleep.
815  *
816  * The return value is 0 if the sleep is for the full timeout. Otherwise,
817  * it is the number of jiffies that were still remaining when the function
818  * returned. return_value == timeout implies the function did not sleep.
819  */
820 long wait_iff_congested(struct zone *zone, int sync, long timeout)
821 {
822         long ret;
823         unsigned long start = jiffies;
824         DEFINE_WAIT(wait);
825         wait_queue_head_t *wqh = &congestion_wqh[sync];
826
827         /*
828          * If there is no congestion, or heavy congestion is not being
829          * encountered in the current zone, yield if necessary instead
830          * of sleeping on the congestion queue
831          */
832         if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
833                         !zone_is_reclaim_congested(zone)) {
834                 cond_resched();
835
836                 /* In case we scheduled, work out time remaining */
837                 ret = timeout - (jiffies - start);
838                 if (ret < 0)
839                         ret = 0;
840
841                 goto out;
842         }
843
844         /* Sleep until uncongested or a write happens */
845         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
846         ret = io_schedule_timeout(timeout);
847         finish_wait(wqh, &wait);
848
849 out:
850         trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
851                                         jiffies_to_usecs(jiffies - start));
852
853         return ret;
854 }
855 EXPORT_SYMBOL(wait_iff_congested);