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 = wb_dirty_limit(wb, 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(wb_stat(wb, WB_WRITEBACK)),
88 (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
92 (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
93 (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
94 (unsigned long) K(wb->write_bandwidth),
99 !list_empty(&bdi->bdi_list), bdi->wb.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 wb 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 wb_wakeup_delayed(struct bdi_writeback *wb)
279 unsigned long timeout;
281 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
282 spin_lock_bh(&wb->work_lock);
283 if (test_bit(WB_registered, &wb->state))
284 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
285 spin_unlock_bh(&wb->work_lock);
289 * Initial write bandwidth: 100 MB/s
291 #define INIT_BW (100 << (20 - PAGE_SHIFT))
293 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
297 memset(wb, 0, sizeof(*wb));
300 wb->last_old_flush = jiffies;
301 INIT_LIST_HEAD(&wb->b_dirty);
302 INIT_LIST_HEAD(&wb->b_io);
303 INIT_LIST_HEAD(&wb->b_more_io);
304 INIT_LIST_HEAD(&wb->b_dirty_time);
305 spin_lock_init(&wb->list_lock);
307 wb->bw_time_stamp = jiffies;
308 wb->balanced_dirty_ratelimit = INIT_BW;
309 wb->dirty_ratelimit = INIT_BW;
310 wb->write_bandwidth = INIT_BW;
311 wb->avg_write_bandwidth = INIT_BW;
313 spin_lock_init(&wb->work_lock);
314 INIT_LIST_HEAD(&wb->work_list);
315 INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
317 err = fprop_local_init_percpu(&wb->completions, GFP_KERNEL);
321 for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
322 err = percpu_counter_init(&wb->stat[i], 0, GFP_KERNEL);
325 percpu_counter_destroy(&wb->stat[i]);
326 fprop_local_destroy_percpu(&wb->completions);
335 * Remove bdi from the global list and shutdown any threads we have running
337 static void wb_shutdown(struct bdi_writeback *wb)
339 /* Make sure nobody queues further work */
340 spin_lock_bh(&wb->work_lock);
341 if (!test_and_clear_bit(WB_registered, &wb->state)) {
342 spin_unlock_bh(&wb->work_lock);
345 spin_unlock_bh(&wb->work_lock);
348 * Drain work list and shutdown the delayed_work. !WB_registered
349 * tells wb_workfn() that @wb is dying and its work_list needs to
350 * be drained no matter what.
352 mod_delayed_work(bdi_wq, &wb->dwork, 0);
353 flush_delayed_work(&wb->dwork);
354 WARN_ON(!list_empty(&wb->work_list));
357 static void wb_exit(struct bdi_writeback *wb)
361 WARN_ON(delayed_work_pending(&wb->dwork));
363 for (i = 0; i < NR_WB_STAT_ITEMS; i++)
364 percpu_counter_destroy(&wb->stat[i]);
366 fprop_local_destroy_percpu(&wb->completions);
369 int bdi_init(struct backing_dev_info *bdi)
376 bdi->max_ratio = 100;
377 bdi->max_prop_frac = FPROP_FRAC_BASE;
378 INIT_LIST_HEAD(&bdi->bdi_list);
380 err = wb_init(&bdi->wb, bdi);
386 EXPORT_SYMBOL(bdi_init);
388 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
389 const char *fmt, ...)
394 if (bdi->dev) /* The driver needs to use separate queues per device */
398 dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
405 bdi_debug_register(bdi, dev_name(dev));
406 set_bit(WB_registered, &bdi->wb.state);
408 spin_lock_bh(&bdi_lock);
409 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
410 spin_unlock_bh(&bdi_lock);
412 trace_writeback_bdi_register(bdi);
415 EXPORT_SYMBOL(bdi_register);
417 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
419 return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
421 EXPORT_SYMBOL(bdi_register_dev);
424 * Remove bdi from bdi_list, and ensure that it is no longer visible
426 static void bdi_remove_from_list(struct backing_dev_info *bdi)
428 spin_lock_bh(&bdi_lock);
429 list_del_rcu(&bdi->bdi_list);
430 spin_unlock_bh(&bdi_lock);
432 synchronize_rcu_expedited();
436 * Called when the device behind @bdi has been removed or ejected.
438 * We can't really do much here except for reducing the dirty ratio at
439 * the moment. In the future we should be able to set a flag so that
440 * the filesystem can handle errors at mark_inode_dirty time instead
441 * of only at writeback time.
443 void bdi_unregister(struct backing_dev_info *bdi)
445 if (WARN_ON_ONCE(!bdi->dev))
448 bdi_set_min_ratio(bdi, 0);
450 EXPORT_SYMBOL(bdi_unregister);
452 void bdi_destroy(struct backing_dev_info *bdi)
454 /* make sure nobody finds us on the bdi_list anymore */
455 bdi_remove_from_list(bdi);
456 wb_shutdown(&bdi->wb);
459 bdi_debug_unregister(bdi);
460 device_unregister(bdi->dev);
466 EXPORT_SYMBOL(bdi_destroy);
469 * For use from filesystems to quickly init and register a bdi associated
470 * with dirty writeback
472 int bdi_setup_and_register(struct backing_dev_info *bdi, char *name)
477 bdi->capabilities = 0;
482 err = bdi_register(bdi, NULL, "%.28s-%ld", name,
483 atomic_long_inc_return(&bdi_seq));
491 EXPORT_SYMBOL(bdi_setup_and_register);
493 static wait_queue_head_t congestion_wqh[2] = {
494 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
495 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
497 static atomic_t nr_bdi_congested[2];
499 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
502 wait_queue_head_t *wqh = &congestion_wqh[sync];
504 bit = sync ? WB_sync_congested : WB_async_congested;
505 if (test_and_clear_bit(bit, &bdi->wb.state))
506 atomic_dec(&nr_bdi_congested[sync]);
507 smp_mb__after_atomic();
508 if (waitqueue_active(wqh))
511 EXPORT_SYMBOL(clear_bdi_congested);
513 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
517 bit = sync ? WB_sync_congested : WB_async_congested;
518 if (!test_and_set_bit(bit, &bdi->wb.state))
519 atomic_inc(&nr_bdi_congested[sync]);
521 EXPORT_SYMBOL(set_bdi_congested);
524 * congestion_wait - wait for a backing_dev to become uncongested
525 * @sync: SYNC or ASYNC IO
526 * @timeout: timeout in jiffies
528 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
529 * write congestion. If no backing_devs are congested then just wait for the
530 * next write to be completed.
532 long congestion_wait(int sync, long timeout)
535 unsigned long start = jiffies;
537 wait_queue_head_t *wqh = &congestion_wqh[sync];
539 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
540 ret = io_schedule_timeout(timeout);
541 finish_wait(wqh, &wait);
543 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
544 jiffies_to_usecs(jiffies - start));
548 EXPORT_SYMBOL(congestion_wait);
551 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
552 * @zone: A zone to check if it is heavily congested
553 * @sync: SYNC or ASYNC IO
554 * @timeout: timeout in jiffies
556 * In the event of a congested backing_dev (any backing_dev) and the given
557 * @zone has experienced recent congestion, this waits for up to @timeout
558 * jiffies for either a BDI to exit congestion of the given @sync queue
559 * or a write to complete.
561 * In the absence of zone congestion, cond_resched() is called to yield
562 * the processor if necessary but otherwise does not sleep.
564 * The return value is 0 if the sleep is for the full timeout. Otherwise,
565 * it is the number of jiffies that were still remaining when the function
566 * returned. return_value == timeout implies the function did not sleep.
568 long wait_iff_congested(struct zone *zone, int sync, long timeout)
571 unsigned long start = jiffies;
573 wait_queue_head_t *wqh = &congestion_wqh[sync];
576 * If there is no congestion, or heavy congestion is not being
577 * encountered in the current zone, yield if necessary instead
578 * of sleeping on the congestion queue
580 if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
581 !test_bit(ZONE_CONGESTED, &zone->flags)) {
584 /* In case we scheduled, work out time remaining */
585 ret = timeout - (jiffies - start);
592 /* Sleep until uncongested or a write happens */
593 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
594 ret = io_schedule_timeout(timeout);
595 finish_wait(wqh, &wait);
598 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
599 jiffies_to_usecs(jiffies - start));
603 EXPORT_SYMBOL(wait_iff_congested);
605 int pdflush_proc_obsolete(struct ctl_table *table, int write,
606 void __user *buffer, size_t *lenp, loff_t *ppos)
610 if (*ppos || *lenp < sizeof(kbuf)) {
615 if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
617 printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",