2 #include <linux/wait.h>
3 #include <linux/backing-dev.h>
4 #include <linux/kthread.h>
5 #include <linux/freezer.h>
7 #include <linux/pagemap.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>
15 static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
17 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
20 EXPORT_SYMBOL(default_unplug_io_fn);
22 struct backing_dev_info default_backing_dev_info = {
24 .ra_pages = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
26 .capabilities = BDI_CAP_MAP_COPY,
27 .unplug_io_fn = default_unplug_io_fn,
29 EXPORT_SYMBOL_GPL(default_backing_dev_info);
31 struct backing_dev_info noop_backing_dev_info = {
34 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
36 static struct class *bdi_class;
39 * bdi_lock protects updates to bdi_list and bdi_pending_list, as well as
40 * reader side protection for bdi_pending_list. bdi_list has RCU reader side
43 DEFINE_SPINLOCK(bdi_lock);
45 LIST_HEAD(bdi_pending_list);
47 static struct task_struct *sync_supers_tsk;
48 static struct timer_list sync_supers_timer;
50 static int bdi_sync_supers(void *);
51 static void sync_supers_timer_fn(unsigned long);
53 static void bdi_add_default_flusher_thread(struct backing_dev_info *bdi);
55 #ifdef CONFIG_DEBUG_FS
56 #include <linux/debugfs.h>
57 #include <linux/seq_file.h>
59 static struct dentry *bdi_debug_root;
61 static void bdi_debug_init(void)
63 bdi_debug_root = debugfs_create_dir("bdi", NULL);
66 static int bdi_debug_stats_show(struct seq_file *m, void *v)
68 struct backing_dev_info *bdi = m->private;
69 struct bdi_writeback *wb = &bdi->wb;
70 unsigned long background_thresh;
71 unsigned long dirty_thresh;
72 unsigned long bdi_thresh;
73 unsigned long nr_dirty, nr_io, nr_more_io, nr_wb;
76 nr_wb = nr_dirty = nr_io = nr_more_io = 0;
77 spin_lock(&inode_lock);
78 list_for_each_entry(inode, &wb->b_dirty, i_list)
80 list_for_each_entry(inode, &wb->b_io, i_list)
82 list_for_each_entry(inode, &wb->b_more_io, i_list)
84 spin_unlock(&inode_lock);
86 get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi);
88 #define K(x) ((x) << (PAGE_SHIFT - 10))
90 "BdiWriteback: %8lu kB\n"
91 "BdiReclaimable: %8lu kB\n"
92 "BdiDirtyThresh: %8lu kB\n"
93 "DirtyThresh: %8lu kB\n"
94 "BackgroundThresh: %8lu kB\n"
100 (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
101 (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
102 K(bdi_thresh), K(dirty_thresh),
103 K(background_thresh), nr_dirty, nr_io, nr_more_io,
104 !list_empty(&bdi->bdi_list), bdi->state);
110 static int bdi_debug_stats_open(struct inode *inode, struct file *file)
112 return single_open(file, bdi_debug_stats_show, inode->i_private);
115 static const struct file_operations bdi_debug_stats_fops = {
116 .open = bdi_debug_stats_open,
119 .release = single_release,
122 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
124 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
125 bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
126 bdi, &bdi_debug_stats_fops);
129 static void bdi_debug_unregister(struct backing_dev_info *bdi)
131 debugfs_remove(bdi->debug_stats);
132 debugfs_remove(bdi->debug_dir);
135 static inline void bdi_debug_init(void)
138 static inline void bdi_debug_register(struct backing_dev_info *bdi,
142 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
147 static ssize_t read_ahead_kb_store(struct device *dev,
148 struct device_attribute *attr,
149 const char *buf, size_t count)
151 struct backing_dev_info *bdi = dev_get_drvdata(dev);
153 unsigned long read_ahead_kb;
154 ssize_t ret = -EINVAL;
156 read_ahead_kb = simple_strtoul(buf, &end, 10);
157 if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
158 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
164 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
166 #define BDI_SHOW(name, expr) \
167 static ssize_t name##_show(struct device *dev, \
168 struct device_attribute *attr, char *page) \
170 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
172 return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
175 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
177 static ssize_t min_ratio_store(struct device *dev,
178 struct device_attribute *attr, const char *buf, size_t count)
180 struct backing_dev_info *bdi = dev_get_drvdata(dev);
183 ssize_t ret = -EINVAL;
185 ratio = simple_strtoul(buf, &end, 10);
186 if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
187 ret = bdi_set_min_ratio(bdi, ratio);
193 BDI_SHOW(min_ratio, bdi->min_ratio)
195 static ssize_t max_ratio_store(struct device *dev,
196 struct device_attribute *attr, const char *buf, size_t count)
198 struct backing_dev_info *bdi = dev_get_drvdata(dev);
201 ssize_t ret = -EINVAL;
203 ratio = simple_strtoul(buf, &end, 10);
204 if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
205 ret = bdi_set_max_ratio(bdi, ratio);
211 BDI_SHOW(max_ratio, bdi->max_ratio)
213 #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
215 static struct device_attribute bdi_dev_attrs[] = {
216 __ATTR_RW(read_ahead_kb),
217 __ATTR_RW(min_ratio),
218 __ATTR_RW(max_ratio),
222 static __init int bdi_class_init(void)
224 bdi_class = class_create(THIS_MODULE, "bdi");
225 if (IS_ERR(bdi_class))
226 return PTR_ERR(bdi_class);
228 bdi_class->dev_attrs = bdi_dev_attrs;
232 postcore_initcall(bdi_class_init);
234 static int __init default_bdi_init(void)
238 sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
239 BUG_ON(IS_ERR(sync_supers_tsk));
241 init_timer(&sync_supers_timer);
242 setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
243 bdi_arm_supers_timer();
245 err = bdi_init(&default_backing_dev_info);
247 bdi_register(&default_backing_dev_info, NULL, "default");
251 subsys_initcall(default_bdi_init);
253 static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
255 memset(wb, 0, sizeof(*wb));
258 wb->last_old_flush = jiffies;
259 INIT_LIST_HEAD(&wb->b_dirty);
260 INIT_LIST_HEAD(&wb->b_io);
261 INIT_LIST_HEAD(&wb->b_more_io);
264 int bdi_has_dirty_io(struct backing_dev_info *bdi)
266 return wb_has_dirty_io(&bdi->wb);
269 static void bdi_flush_io(struct backing_dev_info *bdi)
271 struct writeback_control wbc = {
272 .sync_mode = WB_SYNC_NONE,
273 .older_than_this = NULL,
278 writeback_inodes_wb(&bdi->wb, &wbc);
282 * kupdated() used to do this. We cannot do it from the bdi_forker_thread()
283 * or we risk deadlocking on ->s_umount. The longer term solution would be
284 * to implement sync_supers_bdi() or similar and simply do it from the
285 * bdi writeback thread individually.
287 static int bdi_sync_supers(void *unused)
289 set_user_nice(current, 0);
291 while (!kthread_should_stop()) {
292 set_current_state(TASK_INTERRUPTIBLE);
296 * Do this periodically, like kupdated() did before.
304 void bdi_arm_supers_timer(void)
308 if (!dirty_writeback_interval)
311 next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
312 mod_timer(&sync_supers_timer, round_jiffies_up(next));
315 static void sync_supers_timer_fn(unsigned long unused)
317 wake_up_process(sync_supers_tsk);
318 bdi_arm_supers_timer();
321 static int bdi_forker_thread(void *ptr)
323 struct bdi_writeback *me = ptr;
325 current->flags |= PF_FLUSHER | PF_SWAPWRITE;
329 * Our parent may run at a different priority, just set us to normal
331 set_user_nice(current, 0);
334 struct task_struct *task;
335 struct backing_dev_info *bdi, *tmp;
338 * Temporary measure, we want to make sure we don't see
339 * dirty data on the default backing_dev_info
341 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list))
342 wb_do_writeback(me, 0);
344 spin_lock_bh(&bdi_lock);
347 * Check if any existing bdi's have dirty data without
348 * a thread registered. If so, set that up.
350 list_for_each_entry_safe(bdi, tmp, &bdi_list, bdi_list) {
353 if (list_empty(&bdi->work_list) &&
354 !bdi_has_dirty_io(bdi))
357 bdi_add_default_flusher_thread(bdi);
360 set_current_state(TASK_INTERRUPTIBLE);
362 if (list_empty(&bdi_pending_list)) {
365 spin_unlock_bh(&bdi_lock);
366 wait = msecs_to_jiffies(dirty_writeback_interval * 10);
368 schedule_timeout(wait);
375 __set_current_state(TASK_RUNNING);
378 * This is our real job - check for pending entries in
379 * bdi_pending_list, and create the threads that got added
381 bdi = list_entry(bdi_pending_list.next, struct backing_dev_info,
383 list_del_init(&bdi->bdi_list);
384 spin_unlock_bh(&bdi_lock);
386 task = kthread_run(bdi_writeback_thread, &bdi->wb, "flush-%s",
390 * If thread creation fails, then readd the bdi back to
391 * the list and force writeout of the bdi from this
392 * forker thread. That will free some memory and we can
393 * try again. Add it to the tail so we get a chance to
394 * flush other bdi's to free memory.
396 spin_lock_bh(&bdi_lock);
397 list_add_tail(&bdi->bdi_list, &bdi_pending_list);
398 spin_unlock_bh(&bdi_lock);
408 static void bdi_add_to_pending(struct rcu_head *head)
410 struct backing_dev_info *bdi;
412 bdi = container_of(head, struct backing_dev_info, rcu_head);
413 INIT_LIST_HEAD(&bdi->bdi_list);
415 spin_lock(&bdi_lock);
416 list_add_tail(&bdi->bdi_list, &bdi_pending_list);
417 spin_unlock(&bdi_lock);
420 * We are now on the pending list, wake up bdi_forker_task()
421 * to finish the job and add us back to the active bdi_list
423 wake_up_process(default_backing_dev_info.wb.task);
427 * Add the default flusher thread that gets created for any bdi
428 * that has dirty data pending writeout
430 static void bdi_add_default_flusher_thread(struct backing_dev_info *bdi)
432 if (!bdi_cap_writeback_dirty(bdi))
435 if (WARN_ON(!test_bit(BDI_registered, &bdi->state))) {
436 printk(KERN_ERR "bdi %p/%s is not registered!\n",
442 * Check with the helper whether to proceed adding a thread. Will only
443 * abort if we two or more simultanous calls to
444 * bdi_add_default_flusher_thread() occured, further additions will
445 * block waiting for previous additions to finish.
447 if (!test_and_set_bit(BDI_pending, &bdi->state)) {
448 list_del_rcu(&bdi->bdi_list);
451 * We must wait for the current RCU period to end before
452 * moving to the pending list. So schedule that operation
453 * from an RCU callback.
455 call_rcu(&bdi->rcu_head, bdi_add_to_pending);
460 * Remove bdi from bdi_list, and ensure that it is no longer visible
462 static void bdi_remove_from_list(struct backing_dev_info *bdi)
464 spin_lock_bh(&bdi_lock);
465 list_del_rcu(&bdi->bdi_list);
466 spin_unlock_bh(&bdi_lock);
471 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
472 const char *fmt, ...)
478 if (bdi->dev) /* The driver needs to use separate queues per device */
482 dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
489 spin_lock_bh(&bdi_lock);
490 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
491 spin_unlock_bh(&bdi_lock);
496 * Just start the forker thread for our default backing_dev_info,
497 * and add other bdi's to the list. They will get a thread created
498 * on-demand when they need it.
500 if (bdi_cap_flush_forker(bdi)) {
501 struct bdi_writeback *wb = &bdi->wb;
503 wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
505 if (IS_ERR(wb->task)) {
509 bdi_remove_from_list(bdi);
514 bdi_debug_register(bdi, dev_name(dev));
515 set_bit(BDI_registered, &bdi->state);
516 trace_writeback_bdi_register(bdi);
520 EXPORT_SYMBOL(bdi_register);
522 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
524 return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
526 EXPORT_SYMBOL(bdi_register_dev);
529 * Remove bdi from the global list and shutdown any threads we have running
531 static void bdi_wb_shutdown(struct backing_dev_info *bdi)
533 if (!bdi_cap_writeback_dirty(bdi))
537 * If setup is pending, wait for that to complete first
539 wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
540 TASK_UNINTERRUPTIBLE);
543 * Make sure nobody finds us on the bdi_list anymore
545 bdi_remove_from_list(bdi);
548 * Finally, kill the kernel thread. We don't need to be RCU
549 * safe anymore, since the bdi is gone from visibility. Force
550 * unfreeze of the thread before calling kthread_stop(), otherwise
551 * it would never exet if it is currently stuck in the refrigerator.
554 thaw_process(bdi->wb.task);
555 kthread_stop(bdi->wb.task);
560 * This bdi is going away now, make sure that no super_blocks point to it
562 static void bdi_prune_sb(struct backing_dev_info *bdi)
564 struct super_block *sb;
567 list_for_each_entry(sb, &super_blocks, s_list) {
568 if (sb->s_bdi == bdi)
571 spin_unlock(&sb_lock);
574 void bdi_unregister(struct backing_dev_info *bdi)
577 trace_writeback_bdi_unregister(bdi);
580 if (!bdi_cap_flush_forker(bdi))
581 bdi_wb_shutdown(bdi);
582 bdi_debug_unregister(bdi);
583 device_unregister(bdi->dev);
587 EXPORT_SYMBOL(bdi_unregister);
589 int bdi_init(struct backing_dev_info *bdi)
596 bdi->max_ratio = 100;
597 bdi->max_prop_frac = PROP_FRAC_BASE;
598 spin_lock_init(&bdi->wb_lock);
599 INIT_RCU_HEAD(&bdi->rcu_head);
600 INIT_LIST_HEAD(&bdi->bdi_list);
601 INIT_LIST_HEAD(&bdi->work_list);
603 bdi_wb_init(&bdi->wb, bdi);
605 for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
606 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
611 bdi->dirty_exceeded = 0;
612 err = prop_local_init_percpu(&bdi->completions);
617 percpu_counter_destroy(&bdi->bdi_stat[i]);
622 EXPORT_SYMBOL(bdi_init);
624 void bdi_destroy(struct backing_dev_info *bdi)
629 * Splice our entries to the default_backing_dev_info, if this
632 if (bdi_has_dirty_io(bdi)) {
633 struct bdi_writeback *dst = &default_backing_dev_info.wb;
635 spin_lock(&inode_lock);
636 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
637 list_splice(&bdi->wb.b_io, &dst->b_io);
638 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
639 spin_unlock(&inode_lock);
644 for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
645 percpu_counter_destroy(&bdi->bdi_stat[i]);
647 prop_local_destroy_percpu(&bdi->completions);
649 EXPORT_SYMBOL(bdi_destroy);
652 * For use from filesystems to quickly init and register a bdi associated
653 * with dirty writeback
655 int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
662 bdi->capabilities = cap;
667 sprintf(tmp, "%.28s%s", name, "-%d");
668 err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
676 EXPORT_SYMBOL(bdi_setup_and_register);
678 static wait_queue_head_t congestion_wqh[2] = {
679 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
680 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
683 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
686 wait_queue_head_t *wqh = &congestion_wqh[sync];
688 bit = sync ? BDI_sync_congested : BDI_async_congested;
689 clear_bit(bit, &bdi->state);
690 smp_mb__after_clear_bit();
691 if (waitqueue_active(wqh))
694 EXPORT_SYMBOL(clear_bdi_congested);
696 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
700 bit = sync ? BDI_sync_congested : BDI_async_congested;
701 set_bit(bit, &bdi->state);
703 EXPORT_SYMBOL(set_bdi_congested);
706 * congestion_wait - wait for a backing_dev to become uncongested
707 * @sync: SYNC or ASYNC IO
708 * @timeout: timeout in jiffies
710 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
711 * write congestion. If no backing_devs are congested then just wait for the
712 * next write to be completed.
714 long congestion_wait(int sync, long timeout)
718 wait_queue_head_t *wqh = &congestion_wqh[sync];
720 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
721 ret = io_schedule_timeout(timeout);
722 finish_wait(wqh, &wait);
725 EXPORT_SYMBOL(congestion_wait);