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 struct backing_dev_info noop_backing_dev_info = {
19 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
22 static struct class *bdi_class;
25 * bdi_lock protects updates to bdi_list. bdi_list has RCU reader side
28 DEFINE_SPINLOCK(bdi_lock);
31 /* bdi_wq serves all asynchronous writeback tasks */
32 struct workqueue_struct *bdi_wq;
34 #ifdef CONFIG_DEBUG_FS
35 #include <linux/debugfs.h>
36 #include <linux/seq_file.h>
38 static struct dentry *bdi_debug_root;
40 static void bdi_debug_init(void)
42 bdi_debug_root = debugfs_create_dir("bdi", NULL);
45 static int bdi_debug_stats_show(struct seq_file *m, void *v)
47 struct backing_dev_info *bdi = m->private;
48 struct bdi_writeback *wb = &bdi->wb;
49 unsigned long background_thresh;
50 unsigned long dirty_thresh;
51 unsigned long bdi_thresh;
52 unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
55 nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
56 spin_lock(&wb->list_lock);
57 list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
59 list_for_each_entry(inode, &wb->b_io, i_wb_list)
61 list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
63 list_for_each_entry(inode, &wb->b_dirty_time, i_wb_list)
64 if (inode->i_state & I_DIRTY_TIME)
66 spin_unlock(&wb->list_lock);
68 global_dirty_limits(&background_thresh, &dirty_thresh);
69 bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
71 #define K(x) ((x) << (PAGE_SHIFT - 10))
73 "BdiWriteback: %10lu kB\n"
74 "BdiReclaimable: %10lu kB\n"
75 "BdiDirtyThresh: %10lu kB\n"
76 "DirtyThresh: %10lu kB\n"
77 "BackgroundThresh: %10lu kB\n"
78 "BdiDirtied: %10lu kB\n"
79 "BdiWritten: %10lu kB\n"
80 "BdiWriteBandwidth: %10lu kBps\n"
84 "b_dirty_time: %10lu\n"
87 (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
88 (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
92 (unsigned long) K(bdi_stat(bdi, BDI_DIRTIED)),
93 (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
94 (unsigned long) K(bdi->write_bandwidth),
99 !list_empty(&bdi->bdi_list), bdi->state);
105 static int bdi_debug_stats_open(struct inode *inode, struct file *file)
107 return single_open(file, bdi_debug_stats_show, inode->i_private);
110 static const struct file_operations bdi_debug_stats_fops = {
111 .open = bdi_debug_stats_open,
114 .release = single_release,
117 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
119 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
120 bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
121 bdi, &bdi_debug_stats_fops);
124 static void bdi_debug_unregister(struct backing_dev_info *bdi)
126 debugfs_remove(bdi->debug_stats);
127 debugfs_remove(bdi->debug_dir);
130 static inline void bdi_debug_init(void)
133 static inline void bdi_debug_register(struct backing_dev_info *bdi,
137 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
142 static ssize_t read_ahead_kb_store(struct device *dev,
143 struct device_attribute *attr,
144 const char *buf, size_t count)
146 struct backing_dev_info *bdi = dev_get_drvdata(dev);
147 unsigned long read_ahead_kb;
150 ret = kstrtoul(buf, 10, &read_ahead_kb);
154 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
159 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
161 #define BDI_SHOW(name, expr) \
162 static ssize_t name##_show(struct device *dev, \
163 struct device_attribute *attr, char *page) \
165 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
167 return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
169 static DEVICE_ATTR_RW(name);
171 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
173 static ssize_t min_ratio_store(struct device *dev,
174 struct device_attribute *attr, const char *buf, size_t count)
176 struct backing_dev_info *bdi = dev_get_drvdata(dev);
180 ret = kstrtouint(buf, 10, &ratio);
184 ret = bdi_set_min_ratio(bdi, ratio);
190 BDI_SHOW(min_ratio, bdi->min_ratio)
192 static ssize_t max_ratio_store(struct device *dev,
193 struct device_attribute *attr, const char *buf, size_t count)
195 struct backing_dev_info *bdi = dev_get_drvdata(dev);
199 ret = kstrtouint(buf, 10, &ratio);
203 ret = bdi_set_max_ratio(bdi, ratio);
209 BDI_SHOW(max_ratio, bdi->max_ratio)
211 static ssize_t stable_pages_required_show(struct device *dev,
212 struct device_attribute *attr,
215 struct backing_dev_info *bdi = dev_get_drvdata(dev);
217 return snprintf(page, PAGE_SIZE-1, "%d\n",
218 bdi_cap_stable_pages_required(bdi) ? 1 : 0);
220 static DEVICE_ATTR_RO(stable_pages_required);
222 static struct attribute *bdi_dev_attrs[] = {
223 &dev_attr_read_ahead_kb.attr,
224 &dev_attr_min_ratio.attr,
225 &dev_attr_max_ratio.attr,
226 &dev_attr_stable_pages_required.attr,
229 ATTRIBUTE_GROUPS(bdi_dev);
231 static __init int bdi_class_init(void)
233 bdi_class = class_create(THIS_MODULE, "bdi");
234 if (IS_ERR(bdi_class))
235 return PTR_ERR(bdi_class);
237 bdi_class->dev_groups = bdi_dev_groups;
241 postcore_initcall(bdi_class_init);
243 static int __init default_bdi_init(void)
247 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE |
248 WQ_UNBOUND | WQ_SYSFS, 0);
252 err = bdi_init(&noop_backing_dev_info);
256 subsys_initcall(default_bdi_init);
258 int bdi_has_dirty_io(struct backing_dev_info *bdi)
260 return wb_has_dirty_io(&bdi->wb);
264 * This function is used when the first inode for this bdi is marked dirty. It
265 * wakes-up the corresponding bdi thread which should then take care of the
266 * periodic background write-out of dirty inodes. Since the write-out would
267 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
268 * set up a timer which wakes the bdi thread up later.
270 * Note, we wouldn't bother setting up the timer, but this function is on the
271 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
272 * by delaying the wake-up.
274 * We have to be careful not to postpone flush work if it is scheduled for
275 * earlier. Thus we use queue_delayed_work().
277 void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
279 unsigned long timeout;
281 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
282 spin_lock_bh(&bdi->wb_lock);
283 if (test_bit(BDI_registered, &bdi->state))
284 queue_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);
285 spin_unlock_bh(&bdi->wb_lock);
289 * Remove bdi from bdi_list, and ensure that it is no longer visible
291 static void bdi_remove_from_list(struct backing_dev_info *bdi)
293 spin_lock_bh(&bdi_lock);
294 list_del_rcu(&bdi->bdi_list);
295 spin_unlock_bh(&bdi_lock);
297 synchronize_rcu_expedited();
300 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
301 const char *fmt, ...)
306 if (bdi->dev) /* The driver needs to use separate queues per device */
310 dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
317 bdi_debug_register(bdi, dev_name(dev));
318 set_bit(BDI_registered, &bdi->state);
320 spin_lock_bh(&bdi_lock);
321 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
322 spin_unlock_bh(&bdi_lock);
324 trace_writeback_bdi_register(bdi);
327 EXPORT_SYMBOL(bdi_register);
329 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
331 return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
333 EXPORT_SYMBOL(bdi_register_dev);
336 * Remove bdi from the global list and shutdown any threads we have running
338 static void bdi_wb_shutdown(struct backing_dev_info *bdi)
340 /* Make sure nobody queues further work */
341 spin_lock_bh(&bdi->wb_lock);
342 if (!test_and_clear_bit(BDI_registered, &bdi->state)) {
343 spin_unlock_bh(&bdi->wb_lock);
346 spin_unlock_bh(&bdi->wb_lock);
349 * Make sure nobody finds us on the bdi_list anymore
351 bdi_remove_from_list(bdi);
354 * Drain work list and shutdown the delayed_work. At this point,
355 * @bdi->bdi_list is empty telling bdi_Writeback_workfn() that @bdi
356 * is dying and its work_list needs to be drained no matter what.
358 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
359 flush_delayed_work(&bdi->wb.dwork);
362 static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
364 memset(wb, 0, sizeof(*wb));
367 wb->last_old_flush = jiffies;
368 INIT_LIST_HEAD(&wb->b_dirty);
369 INIT_LIST_HEAD(&wb->b_io);
370 INIT_LIST_HEAD(&wb->b_more_io);
371 INIT_LIST_HEAD(&wb->b_dirty_time);
372 spin_lock_init(&wb->list_lock);
373 INIT_DELAYED_WORK(&wb->dwork, bdi_writeback_workfn);
377 * Initial write bandwidth: 100 MB/s
379 #define INIT_BW (100 << (20 - PAGE_SHIFT))
381 int bdi_init(struct backing_dev_info *bdi)
388 bdi->max_ratio = 100;
389 bdi->max_prop_frac = FPROP_FRAC_BASE;
390 spin_lock_init(&bdi->wb_lock);
391 INIT_LIST_HEAD(&bdi->bdi_list);
392 INIT_LIST_HEAD(&bdi->work_list);
394 bdi_wb_init(&bdi->wb, bdi);
396 for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
397 err = percpu_counter_init(&bdi->bdi_stat[i], 0, GFP_KERNEL);
402 bdi->dirty_exceeded = 0;
404 bdi->bw_time_stamp = jiffies;
405 bdi->written_stamp = 0;
407 bdi->balanced_dirty_ratelimit = INIT_BW;
408 bdi->dirty_ratelimit = INIT_BW;
409 bdi->write_bandwidth = INIT_BW;
410 bdi->avg_write_bandwidth = INIT_BW;
412 err = fprop_local_init_percpu(&bdi->completions, GFP_KERNEL);
417 percpu_counter_destroy(&bdi->bdi_stat[i]);
422 EXPORT_SYMBOL(bdi_init);
424 void bdi_destroy(struct backing_dev_info *bdi)
428 bdi_wb_shutdown(bdi);
429 bdi_set_min_ratio(bdi, 0);
431 WARN_ON(!list_empty(&bdi->work_list));
432 WARN_ON(delayed_work_pending(&bdi->wb.dwork));
435 bdi_debug_unregister(bdi);
436 device_unregister(bdi->dev);
440 for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
441 percpu_counter_destroy(&bdi->bdi_stat[i]);
442 fprop_local_destroy_percpu(&bdi->completions);
444 EXPORT_SYMBOL(bdi_destroy);
447 * For use from filesystems to quickly init and register a bdi associated
448 * with dirty writeback
450 int bdi_setup_and_register(struct backing_dev_info *bdi, char *name)
455 bdi->capabilities = 0;
460 err = bdi_register(bdi, NULL, "%.28s-%ld", name,
461 atomic_long_inc_return(&bdi_seq));
469 EXPORT_SYMBOL(bdi_setup_and_register);
471 static wait_queue_head_t congestion_wqh[2] = {
472 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
473 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
475 static atomic_t nr_bdi_congested[2];
477 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
480 wait_queue_head_t *wqh = &congestion_wqh[sync];
482 bit = sync ? BDI_sync_congested : BDI_async_congested;
483 if (test_and_clear_bit(bit, &bdi->state))
484 atomic_dec(&nr_bdi_congested[sync]);
485 smp_mb__after_atomic();
486 if (waitqueue_active(wqh))
489 EXPORT_SYMBOL(clear_bdi_congested);
491 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
495 bit = sync ? BDI_sync_congested : BDI_async_congested;
496 if (!test_and_set_bit(bit, &bdi->state))
497 atomic_inc(&nr_bdi_congested[sync]);
499 EXPORT_SYMBOL(set_bdi_congested);
502 * congestion_wait - wait for a backing_dev to become uncongested
503 * @sync: SYNC or ASYNC IO
504 * @timeout: timeout in jiffies
506 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
507 * write congestion. If no backing_devs are congested then just wait for the
508 * next write to be completed.
510 long congestion_wait(int sync, long timeout)
513 unsigned long start = jiffies;
515 wait_queue_head_t *wqh = &congestion_wqh[sync];
517 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
518 ret = io_schedule_timeout(timeout);
519 finish_wait(wqh, &wait);
521 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
522 jiffies_to_usecs(jiffies - start));
526 EXPORT_SYMBOL(congestion_wait);
529 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
530 * @zone: A zone to check if it is heavily congested
531 * @sync: SYNC or ASYNC IO
532 * @timeout: timeout in jiffies
534 * In the event of a congested backing_dev (any backing_dev) and the given
535 * @zone has experienced recent congestion, this waits for up to @timeout
536 * jiffies for either a BDI to exit congestion of the given @sync queue
537 * or a write to complete.
539 * In the absence of zone congestion, cond_resched() is called to yield
540 * the processor if necessary but otherwise does not sleep.
542 * The return value is 0 if the sleep is for the full timeout. Otherwise,
543 * it is the number of jiffies that were still remaining when the function
544 * returned. return_value == timeout implies the function did not sleep.
546 long wait_iff_congested(struct zone *zone, int sync, long timeout)
549 unsigned long start = jiffies;
551 wait_queue_head_t *wqh = &congestion_wqh[sync];
554 * If there is no congestion, or heavy congestion is not being
555 * encountered in the current zone, yield if necessary instead
556 * of sleeping on the congestion queue
558 if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
559 !test_bit(ZONE_CONGESTED, &zone->flags)) {
562 /* In case we scheduled, work out time remaining */
563 ret = timeout - (jiffies - start);
570 /* Sleep until uncongested or a write happens */
571 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
572 ret = io_schedule_timeout(timeout);
573 finish_wait(wqh, &wait);
576 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
577 jiffies_to_usecs(jiffies - start));
581 EXPORT_SYMBOL(wait_iff_congested);
583 int pdflush_proc_obsolete(struct ctl_table *table, int write,
584 void __user *buffer, size_t *lenp, loff_t *ppos)
588 if (*ppos || *lenp < sizeof(kbuf)) {
593 if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
595 printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",