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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. bdi_list has RCU reader side
35 * locking.
36 */
37DEFINE_SPINLOCK(bdi_lock);
38LIST_HEAD(bdi_list);
39
40/* bdi_wq serves all asynchronous writeback tasks */
41struct workqueue_struct *bdi_wq;
42
43void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
44{
45 if (wb1 < wb2) {
46 spin_lock(&wb1->list_lock);
47 spin_lock_nested(&wb2->list_lock, 1);
48 } else {
49 spin_lock(&wb2->list_lock);
50 spin_lock_nested(&wb1->list_lock, 1);
51 }
52}
53
54#ifdef CONFIG_DEBUG_FS
55#include <linux/debugfs.h>
56#include <linux/seq_file.h>
57
58static struct dentry *bdi_debug_root;
59
60static void bdi_debug_init(void)
61{
62 bdi_debug_root = debugfs_create_dir("bdi", NULL);
63}
64
65static int bdi_debug_stats_show(struct seq_file *m, void *v)
66{
67 struct backing_dev_info *bdi = m->private;
68 struct bdi_writeback *wb = &bdi->wb;
69 unsigned long background_thresh;
70 unsigned long dirty_thresh;
71 unsigned long bdi_thresh;
72 unsigned long nr_dirty, nr_io, nr_more_io;
73 struct inode *inode;
74
75 nr_dirty = nr_io = nr_more_io = 0;
76 spin_lock(&wb->list_lock);
77 list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
78 nr_dirty++;
79 list_for_each_entry(inode, &wb->b_io, i_wb_list)
80 nr_io++;
81 list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
82 nr_more_io++;
83 spin_unlock(&wb->list_lock);
84
85 global_dirty_limits(&background_thresh, &dirty_thresh);
86 bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
87
88#define K(x) ((x) << (PAGE_SHIFT - 10))
89 seq_printf(m,
90 "BdiWriteback: %10lu kB\n"
91 "BdiReclaimable: %10lu kB\n"
92 "BdiDirtyThresh: %10lu kB\n"
93 "DirtyThresh: %10lu kB\n"
94 "BackgroundThresh: %10lu kB\n"
95 "BdiDirtied: %10lu kB\n"
96 "BdiWritten: %10lu kB\n"
97 "BdiWriteBandwidth: %10lu kBps\n"
98 "b_dirty: %10lu\n"
99 "b_io: %10lu\n"
100 "b_more_io: %10lu\n"
101 "bdi_list: %10u\n"
102 "state: %10lx\n",
103 (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
104 (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
105 K(bdi_thresh),
106 K(dirty_thresh),
107 K(background_thresh),
108 (unsigned long) K(bdi_stat(bdi, BDI_DIRTIED)),
109 (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
110 (unsigned long) K(bdi->write_bandwidth),
111 nr_dirty,
112 nr_io,
113 nr_more_io,
114 !list_empty(&bdi->bdi_list), bdi->state);
115#undef K
116
117 return 0;
118}
119
120static int bdi_debug_stats_open(struct inode *inode, struct file *file)
121{
122 return single_open(file, bdi_debug_stats_show, inode->i_private);
123}
124
125static const struct file_operations bdi_debug_stats_fops = {
126 .open = bdi_debug_stats_open,
127 .read = seq_read,
128 .llseek = seq_lseek,
129 .release = single_release,
130};
131
132static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
133{
134 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
135 bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
136 bdi, &bdi_debug_stats_fops);
137}
138
139static void bdi_debug_unregister(struct backing_dev_info *bdi)
140{
141 debugfs_remove(bdi->debug_stats);
142 debugfs_remove(bdi->debug_dir);
143}
144#else
145static inline void bdi_debug_init(void)
146{
147}
148static inline void bdi_debug_register(struct backing_dev_info *bdi,
149 const char *name)
150{
151}
152static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
153{
154}
155#endif
156
157static ssize_t read_ahead_kb_store(struct device *dev,
158 struct device_attribute *attr,
159 const char *buf, size_t count)
160{
161 struct backing_dev_info *bdi = dev_get_drvdata(dev);
162 unsigned long read_ahead_kb;
163 ssize_t ret;
164
165 ret = kstrtoul(buf, 10, &read_ahead_kb);
166 if (ret < 0)
167 return ret;
168
169 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
170
171 return count;
172}
173
174#define K(pages) ((pages) << (PAGE_SHIFT - 10))
175
176#define BDI_SHOW(name, expr) \
177static ssize_t name##_show(struct device *dev, \
178 struct device_attribute *attr, char *page) \
179{ \
180 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
181 \
182 return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
183} \
184static DEVICE_ATTR_RW(name);
185
186BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
187
188static ssize_t min_ratio_store(struct device *dev,
189 struct device_attribute *attr, const char *buf, size_t count)
190{
191 struct backing_dev_info *bdi = dev_get_drvdata(dev);
192 unsigned int ratio;
193 ssize_t ret;
194
195 ret = kstrtouint(buf, 10, &ratio);
196 if (ret < 0)
197 return ret;
198
199 ret = bdi_set_min_ratio(bdi, ratio);
200 if (!ret)
201 ret = count;
202
203 return ret;
204}
205BDI_SHOW(min_ratio, bdi->min_ratio)
206
207static ssize_t max_ratio_store(struct device *dev,
208 struct device_attribute *attr, const char *buf, size_t count)
209{
210 struct backing_dev_info *bdi = dev_get_drvdata(dev);
211 unsigned int ratio;
212 ssize_t ret;
213
214 ret = kstrtouint(buf, 10, &ratio);
215 if (ret < 0)
216 return ret;
217
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
226static ssize_t stable_pages_required_show(struct device *dev,
227 struct device_attribute *attr,
228 char *page)
229{
230 struct backing_dev_info *bdi = dev_get_drvdata(dev);
231
232 return snprintf(page, PAGE_SIZE-1, "%d\n",
233 bdi_cap_stable_pages_required(bdi) ? 1 : 0);
234}
235static DEVICE_ATTR_RO(stable_pages_required);
236
237static struct attribute *bdi_dev_attrs[] = {
238 &dev_attr_read_ahead_kb.attr,
239 &dev_attr_min_ratio.attr,
240 &dev_attr_max_ratio.attr,
241 &dev_attr_stable_pages_required.attr,
242 NULL,
243};
244ATTRIBUTE_GROUPS(bdi_dev);
245
246static __init int bdi_class_init(void)
247{
248 bdi_class = class_create(THIS_MODULE, "bdi");
249 if (IS_ERR(bdi_class))
250 return PTR_ERR(bdi_class);
251
252 bdi_class->dev_groups = bdi_dev_groups;
253 bdi_debug_init();
254 return 0;
255}
256postcore_initcall(bdi_class_init);
257
258static int __init default_bdi_init(void)
259{
260 int err;
261
262 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE |
263 WQ_UNBOUND | WQ_SYSFS, 0);
264 if (!bdi_wq)
265 return -ENOMEM;
266
267 err = bdi_init(&default_backing_dev_info);
268 if (!err)
269 bdi_register(&default_backing_dev_info, NULL, "default");
270 err = bdi_init(&noop_backing_dev_info);
271
272 return err;
273}
274subsys_initcall(default_bdi_init);
275
276int bdi_has_dirty_io(struct backing_dev_info *bdi)
277{
278 return wb_has_dirty_io(&bdi->wb);
279}
280
281/*
282 * This function is used when the first inode for this bdi is marked dirty. It
283 * wakes-up the corresponding bdi thread which should then take care of the
284 * periodic background write-out of dirty inodes. Since the write-out would
285 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
286 * set up a timer which wakes the bdi thread up later.
287 *
288 * Note, we wouldn't bother setting up the timer, but this function is on the
289 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
290 * by delaying the wake-up.
291 *
292 * We have to be careful not to postpone flush work if it is scheduled for
293 * earlier. Thus we use queue_delayed_work().
294 */
295void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
296{
297 unsigned long timeout;
298
299 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
300 spin_lock_bh(&bdi->wb_lock);
301 if (test_bit(BDI_registered, &bdi->state))
302 queue_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);
303 spin_unlock_bh(&bdi->wb_lock);
304}
305
306/*
307 * Remove bdi from bdi_list, and ensure that it is no longer visible
308 */
309static void bdi_remove_from_list(struct backing_dev_info *bdi)
310{
311 spin_lock_bh(&bdi_lock);
312 list_del_rcu(&bdi->bdi_list);
313 spin_unlock_bh(&bdi_lock);
314
315 synchronize_rcu_expedited();
316}
317
318int bdi_register(struct backing_dev_info *bdi, struct device *parent,
319 const char *fmt, ...)
320{
321 va_list args;
322 struct device *dev;
323
324 if (bdi->dev) /* The driver needs to use separate queues per device */
325 return 0;
326
327 va_start(args, fmt);
328 dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
329 va_end(args);
330 if (IS_ERR(dev))
331 return PTR_ERR(dev);
332
333 bdi->dev = dev;
334
335 bdi_debug_register(bdi, dev_name(dev));
336 set_bit(BDI_registered, &bdi->state);
337
338 spin_lock_bh(&bdi_lock);
339 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
340 spin_unlock_bh(&bdi_lock);
341
342 trace_writeback_bdi_register(bdi);
343 return 0;
344}
345EXPORT_SYMBOL(bdi_register);
346
347int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
348{
349 return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
350}
351EXPORT_SYMBOL(bdi_register_dev);
352
353/*
354 * Remove bdi from the global list and shutdown any threads we have running
355 */
356static void bdi_wb_shutdown(struct backing_dev_info *bdi)
357{
358 if (!bdi_cap_writeback_dirty(bdi))
359 return;
360
361 /*
362 * Make sure nobody finds us on the bdi_list anymore
363 */
364 bdi_remove_from_list(bdi);
365
366 /* Make sure nobody queues further work */
367 spin_lock_bh(&bdi->wb_lock);
368 clear_bit(BDI_registered, &bdi->state);
369 spin_unlock_bh(&bdi->wb_lock);
370
371 /*
372 * Drain work list and shutdown the delayed_work. At this point,
373 * @bdi->bdi_list is empty telling bdi_Writeback_workfn() that @bdi
374 * is dying and its work_list needs to be drained no matter what.
375 */
376 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
377 flush_delayed_work(&bdi->wb.dwork);
378 WARN_ON(!list_empty(&bdi->work_list));
379
380 /*
381 * This shouldn't be necessary unless @bdi for some reason has
382 * unflushed dirty IO after work_list is drained. Do it anyway
383 * just in case.
384 */
385 cancel_delayed_work_sync(&bdi->wb.dwork);
386}
387
388/*
389 * This bdi is going away now, make sure that no super_blocks point to it
390 */
391static void bdi_prune_sb(struct backing_dev_info *bdi)
392{
393 struct super_block *sb;
394
395 spin_lock(&sb_lock);
396 list_for_each_entry(sb, &super_blocks, s_list) {
397 if (sb->s_bdi == bdi)
398 sb->s_bdi = &default_backing_dev_info;
399 }
400 spin_unlock(&sb_lock);
401}
402
403void bdi_unregister(struct backing_dev_info *bdi)
404{
405 struct device *dev = bdi->dev;
406
407 if (dev) {
408 bdi_set_min_ratio(bdi, 0);
409 trace_writeback_bdi_unregister(bdi);
410 bdi_prune_sb(bdi);
411
412 bdi_wb_shutdown(bdi);
413 bdi_debug_unregister(bdi);
414
415 spin_lock_bh(&bdi->wb_lock);
416 bdi->dev = NULL;
417 spin_unlock_bh(&bdi->wb_lock);
418
419 device_unregister(dev);
420 }
421}
422EXPORT_SYMBOL(bdi_unregister);
423
424static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
425{
426 memset(wb, 0, sizeof(*wb));
427
428 wb->bdi = bdi;
429 wb->last_old_flush = jiffies;
430 INIT_LIST_HEAD(&wb->b_dirty);
431 INIT_LIST_HEAD(&wb->b_io);
432 INIT_LIST_HEAD(&wb->b_more_io);
433 spin_lock_init(&wb->list_lock);
434 INIT_DELAYED_WORK(&wb->dwork, bdi_writeback_workfn);
435}
436
437/*
438 * Initial write bandwidth: 100 MB/s
439 */
440#define INIT_BW (100 << (20 - PAGE_SHIFT))
441
442int bdi_init(struct backing_dev_info *bdi)
443{
444 int i, err;
445
446 bdi->dev = NULL;
447
448 bdi->min_ratio = 0;
449 bdi->max_ratio = 100;
450 bdi->max_prop_frac = FPROP_FRAC_BASE;
451 spin_lock_init(&bdi->wb_lock);
452 INIT_LIST_HEAD(&bdi->bdi_list);
453 INIT_LIST_HEAD(&bdi->work_list);
454
455 bdi_wb_init(&bdi->wb, bdi);
456
457 for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
458 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
459 if (err)
460 goto err;
461 }
462
463 bdi->dirty_exceeded = 0;
464
465 bdi->bw_time_stamp = jiffies;
466 bdi->written_stamp = 0;
467
468 bdi->balanced_dirty_ratelimit = INIT_BW;
469 bdi->dirty_ratelimit = INIT_BW;
470 bdi->write_bandwidth = INIT_BW;
471 bdi->avg_write_bandwidth = INIT_BW;
472
473 err = fprop_local_init_percpu(&bdi->completions);
474
475 if (err) {
476err:
477 while (i--)
478 percpu_counter_destroy(&bdi->bdi_stat[i]);
479 }
480
481 return err;
482}
483EXPORT_SYMBOL(bdi_init);
484
485void bdi_destroy(struct backing_dev_info *bdi)
486{
487 int i;
488
489 /*
490 * Splice our entries to the default_backing_dev_info, if this
491 * bdi disappears
492 */
493 if (bdi_has_dirty_io(bdi)) {
494 struct bdi_writeback *dst = &default_backing_dev_info.wb;
495
496 bdi_lock_two(&bdi->wb, dst);
497 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
498 list_splice(&bdi->wb.b_io, &dst->b_io);
499 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
500 spin_unlock(&bdi->wb.list_lock);
501 spin_unlock(&dst->list_lock);
502 }
503
504 bdi_unregister(bdi);
505
506 /*
507 * If bdi_unregister() had already been called earlier, the dwork
508 * could still be pending because bdi_prune_sb() can race with the
509 * bdi_wakeup_thread_delayed() calls from __mark_inode_dirty().
510 */
511 cancel_delayed_work_sync(&bdi->wb.dwork);
512
513 for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
514 percpu_counter_destroy(&bdi->bdi_stat[i]);
515
516 fprop_local_destroy_percpu(&bdi->completions);
517}
518EXPORT_SYMBOL(bdi_destroy);
519
520/*
521 * For use from filesystems to quickly init and register a bdi associated
522 * with dirty writeback
523 */
524int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
525 unsigned int cap)
526{
527 int err;
528
529 bdi->name = name;
530 bdi->capabilities = cap;
531 err = bdi_init(bdi);
532 if (err)
533 return err;
534
535 err = bdi_register(bdi, NULL, "%.28s-%ld", name,
536 atomic_long_inc_return(&bdi_seq));
537 if (err) {
538 bdi_destroy(bdi);
539 return err;
540 }
541
542 return 0;
543}
544EXPORT_SYMBOL(bdi_setup_and_register);
545
546static wait_queue_head_t congestion_wqh[2] = {
547 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
548 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
549 };
550static atomic_t nr_bdi_congested[2];
551
552void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
553{
554 enum bdi_state bit;
555 wait_queue_head_t *wqh = &congestion_wqh[sync];
556
557 bit = sync ? BDI_sync_congested : BDI_async_congested;
558 if (test_and_clear_bit(bit, &bdi->state))
559 atomic_dec(&nr_bdi_congested[sync]);
560 smp_mb__after_clear_bit();
561 if (waitqueue_active(wqh))
562 wake_up(wqh);
563}
564EXPORT_SYMBOL(clear_bdi_congested);
565
566void set_bdi_congested(struct backing_dev_info *bdi, int sync)
567{
568 enum bdi_state bit;
569
570 bit = sync ? BDI_sync_congested : BDI_async_congested;
571 if (!test_and_set_bit(bit, &bdi->state))
572 atomic_inc(&nr_bdi_congested[sync]);
573}
574EXPORT_SYMBOL(set_bdi_congested);
575
576/**
577 * congestion_wait - wait for a backing_dev to become uncongested
578 * @sync: SYNC or ASYNC IO
579 * @timeout: timeout in jiffies
580 *
581 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
582 * write congestion. If no backing_devs are congested then just wait for the
583 * next write to be completed.
584 */
585long congestion_wait(int sync, long timeout)
586{
587 long ret;
588 unsigned long start = jiffies;
589 DEFINE_WAIT(wait);
590 wait_queue_head_t *wqh = &congestion_wqh[sync];
591
592 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
593 ret = io_schedule_timeout(timeout);
594 finish_wait(wqh, &wait);
595
596 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
597 jiffies_to_usecs(jiffies - start));
598
599 return ret;
600}
601EXPORT_SYMBOL(congestion_wait);
602
603/**
604 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
605 * @zone: A zone to check if it is heavily congested
606 * @sync: SYNC or ASYNC IO
607 * @timeout: timeout in jiffies
608 *
609 * In the event of a congested backing_dev (any backing_dev) and the given
610 * @zone has experienced recent congestion, this waits for up to @timeout
611 * jiffies for either a BDI to exit congestion of the given @sync queue
612 * or a write to complete.
613 *
614 * In the absence of zone congestion, cond_resched() is called to yield
615 * the processor if necessary but otherwise does not sleep.
616 *
617 * The return value is 0 if the sleep is for the full timeout. Otherwise,
618 * it is the number of jiffies that were still remaining when the function
619 * returned. return_value == timeout implies the function did not sleep.
620 */
621long wait_iff_congested(struct zone *zone, int sync, long timeout)
622{
623 long ret;
624 unsigned long start = jiffies;
625 DEFINE_WAIT(wait);
626 wait_queue_head_t *wqh = &congestion_wqh[sync];
627
628 /*
629 * If there is no congestion, or heavy congestion is not being
630 * encountered in the current zone, yield if necessary instead
631 * of sleeping on the congestion queue
632 */
633 if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
634 !zone_is_reclaim_congested(zone)) {
635 cond_resched();
636
637 /* In case we scheduled, work out time remaining */
638 ret = timeout - (jiffies - start);
639 if (ret < 0)
640 ret = 0;
641
642 goto out;
643 }
644
645 /* Sleep until uncongested or a write happens */
646 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
647 ret = io_schedule_timeout(timeout);
648 finish_wait(wqh, &wait);
649
650out:
651 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
652 jiffies_to_usecs(jiffies - start));
653
654 return ret;
655}
656EXPORT_SYMBOL(wait_iff_congested);
657
658int pdflush_proc_obsolete(struct ctl_table *table, int write,
659 void __user *buffer, size_t *lenp, loff_t *ppos)
660{
661 char kbuf[] = "0\n";
662
663 if (*ppos || *lenp < sizeof(kbuf)) {
664 *lenp = 0;
665 return 0;
666 }
667
668 if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
669 return -EFAULT;
670 printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
671 table->procname);
672
673 *lenp = 2;
674 *ppos += *lenp;
675 return 2;
676}
1// SPDX-License-Identifier: GPL-2.0-only
2
3#include <linux/blkdev.h>
4#include <linux/wait.h>
5#include <linux/rbtree.h>
6#include <linux/kthread.h>
7#include <linux/backing-dev.h>
8#include <linux/blk-cgroup.h>
9#include <linux/freezer.h>
10#include <linux/fs.h>
11#include <linux/pagemap.h>
12#include <linux/mm.h>
13#include <linux/sched/mm.h>
14#include <linux/sched.h>
15#include <linux/module.h>
16#include <linux/writeback.h>
17#include <linux/device.h>
18#include <trace/events/writeback.h>
19
20struct backing_dev_info noop_backing_dev_info;
21EXPORT_SYMBOL_GPL(noop_backing_dev_info);
22
23static struct class *bdi_class;
24static const char *bdi_unknown_name = "(unknown)";
25
26/*
27 * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
28 * reader side locking.
29 */
30DEFINE_SPINLOCK(bdi_lock);
31static u64 bdi_id_cursor;
32static struct rb_root bdi_tree = RB_ROOT;
33LIST_HEAD(bdi_list);
34
35/* bdi_wq serves all asynchronous writeback tasks */
36struct workqueue_struct *bdi_wq;
37
38#define K(x) ((x) << (PAGE_SHIFT - 10))
39
40#ifdef CONFIG_DEBUG_FS
41#include <linux/debugfs.h>
42#include <linux/seq_file.h>
43
44static struct dentry *bdi_debug_root;
45
46static void bdi_debug_init(void)
47{
48 bdi_debug_root = debugfs_create_dir("bdi", NULL);
49}
50
51static int bdi_debug_stats_show(struct seq_file *m, void *v)
52{
53 struct backing_dev_info *bdi = m->private;
54 struct bdi_writeback *wb = &bdi->wb;
55 unsigned long background_thresh;
56 unsigned long dirty_thresh;
57 unsigned long wb_thresh;
58 unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
59 struct inode *inode;
60
61 nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
62 spin_lock(&wb->list_lock);
63 list_for_each_entry(inode, &wb->b_dirty, i_io_list)
64 nr_dirty++;
65 list_for_each_entry(inode, &wb->b_io, i_io_list)
66 nr_io++;
67 list_for_each_entry(inode, &wb->b_more_io, i_io_list)
68 nr_more_io++;
69 list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
70 if (inode->i_state & I_DIRTY_TIME)
71 nr_dirty_time++;
72 spin_unlock(&wb->list_lock);
73
74 global_dirty_limits(&background_thresh, &dirty_thresh);
75 wb_thresh = wb_calc_thresh(wb, dirty_thresh);
76
77 seq_printf(m,
78 "BdiWriteback: %10lu kB\n"
79 "BdiReclaimable: %10lu kB\n"
80 "BdiDirtyThresh: %10lu kB\n"
81 "DirtyThresh: %10lu kB\n"
82 "BackgroundThresh: %10lu kB\n"
83 "BdiDirtied: %10lu kB\n"
84 "BdiWritten: %10lu kB\n"
85 "BdiWriteBandwidth: %10lu kBps\n"
86 "b_dirty: %10lu\n"
87 "b_io: %10lu\n"
88 "b_more_io: %10lu\n"
89 "b_dirty_time: %10lu\n"
90 "bdi_list: %10u\n"
91 "state: %10lx\n",
92 (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
93 (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
94 K(wb_thresh),
95 K(dirty_thresh),
96 K(background_thresh),
97 (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
98 (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
99 (unsigned long) K(wb->write_bandwidth),
100 nr_dirty,
101 nr_io,
102 nr_more_io,
103 nr_dirty_time,
104 !list_empty(&bdi->bdi_list), bdi->wb.state);
105
106 return 0;
107}
108DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
109
110static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
111{
112 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
113
114 debugfs_create_file("stats", 0444, bdi->debug_dir, bdi,
115 &bdi_debug_stats_fops);
116}
117
118static void bdi_debug_unregister(struct backing_dev_info *bdi)
119{
120 debugfs_remove_recursive(bdi->debug_dir);
121}
122#else
123static inline void bdi_debug_init(void)
124{
125}
126static inline void bdi_debug_register(struct backing_dev_info *bdi,
127 const char *name)
128{
129}
130static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
131{
132}
133#endif
134
135static ssize_t read_ahead_kb_store(struct device *dev,
136 struct device_attribute *attr,
137 const char *buf, size_t count)
138{
139 struct backing_dev_info *bdi = dev_get_drvdata(dev);
140 unsigned long read_ahead_kb;
141 ssize_t ret;
142
143 ret = kstrtoul(buf, 10, &read_ahead_kb);
144 if (ret < 0)
145 return ret;
146
147 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
148
149 return count;
150}
151
152#define BDI_SHOW(name, expr) \
153static ssize_t name##_show(struct device *dev, \
154 struct device_attribute *attr, char *buf) \
155{ \
156 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
157 \
158 return sysfs_emit(buf, "%lld\n", (long long)expr); \
159} \
160static DEVICE_ATTR_RW(name);
161
162BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
163
164static ssize_t min_ratio_store(struct device *dev,
165 struct device_attribute *attr, const char *buf, size_t count)
166{
167 struct backing_dev_info *bdi = dev_get_drvdata(dev);
168 unsigned int ratio;
169 ssize_t ret;
170
171 ret = kstrtouint(buf, 10, &ratio);
172 if (ret < 0)
173 return ret;
174
175 ret = bdi_set_min_ratio(bdi, ratio);
176 if (!ret)
177 ret = count;
178
179 return ret;
180}
181BDI_SHOW(min_ratio, bdi->min_ratio / BDI_RATIO_SCALE)
182
183static ssize_t min_ratio_fine_store(struct device *dev,
184 struct device_attribute *attr, const char *buf, size_t count)
185{
186 struct backing_dev_info *bdi = dev_get_drvdata(dev);
187 unsigned int ratio;
188 ssize_t ret;
189
190 ret = kstrtouint(buf, 10, &ratio);
191 if (ret < 0)
192 return ret;
193
194 ret = bdi_set_min_ratio_no_scale(bdi, ratio);
195 if (!ret)
196 ret = count;
197
198 return ret;
199}
200BDI_SHOW(min_ratio_fine, bdi->min_ratio)
201
202static ssize_t max_ratio_store(struct device *dev,
203 struct device_attribute *attr, const char *buf, size_t count)
204{
205 struct backing_dev_info *bdi = dev_get_drvdata(dev);
206 unsigned int ratio;
207 ssize_t ret;
208
209 ret = kstrtouint(buf, 10, &ratio);
210 if (ret < 0)
211 return ret;
212
213 ret = bdi_set_max_ratio(bdi, ratio);
214 if (!ret)
215 ret = count;
216
217 return ret;
218}
219BDI_SHOW(max_ratio, bdi->max_ratio / BDI_RATIO_SCALE)
220
221static ssize_t max_ratio_fine_store(struct device *dev,
222 struct device_attribute *attr, const char *buf, size_t count)
223{
224 struct backing_dev_info *bdi = dev_get_drvdata(dev);
225 unsigned int ratio;
226 ssize_t ret;
227
228 ret = kstrtouint(buf, 10, &ratio);
229 if (ret < 0)
230 return ret;
231
232 ret = bdi_set_max_ratio_no_scale(bdi, ratio);
233 if (!ret)
234 ret = count;
235
236 return ret;
237}
238BDI_SHOW(max_ratio_fine, bdi->max_ratio)
239
240static ssize_t min_bytes_show(struct device *dev,
241 struct device_attribute *attr,
242 char *buf)
243{
244 struct backing_dev_info *bdi = dev_get_drvdata(dev);
245
246 return sysfs_emit(buf, "%llu\n", bdi_get_min_bytes(bdi));
247}
248
249static ssize_t min_bytes_store(struct device *dev,
250 struct device_attribute *attr, const char *buf, size_t count)
251{
252 struct backing_dev_info *bdi = dev_get_drvdata(dev);
253 u64 bytes;
254 ssize_t ret;
255
256 ret = kstrtoull(buf, 10, &bytes);
257 if (ret < 0)
258 return ret;
259
260 ret = bdi_set_min_bytes(bdi, bytes);
261 if (!ret)
262 ret = count;
263
264 return ret;
265}
266DEVICE_ATTR_RW(min_bytes);
267
268static ssize_t max_bytes_show(struct device *dev,
269 struct device_attribute *attr,
270 char *buf)
271{
272 struct backing_dev_info *bdi = dev_get_drvdata(dev);
273
274 return sysfs_emit(buf, "%llu\n", bdi_get_max_bytes(bdi));
275}
276
277static ssize_t max_bytes_store(struct device *dev,
278 struct device_attribute *attr, const char *buf, size_t count)
279{
280 struct backing_dev_info *bdi = dev_get_drvdata(dev);
281 u64 bytes;
282 ssize_t ret;
283
284 ret = kstrtoull(buf, 10, &bytes);
285 if (ret < 0)
286 return ret;
287
288 ret = bdi_set_max_bytes(bdi, bytes);
289 if (!ret)
290 ret = count;
291
292 return ret;
293}
294DEVICE_ATTR_RW(max_bytes);
295
296static ssize_t stable_pages_required_show(struct device *dev,
297 struct device_attribute *attr,
298 char *buf)
299{
300 dev_warn_once(dev,
301 "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n");
302 return sysfs_emit(buf, "%d\n", 0);
303}
304static DEVICE_ATTR_RO(stable_pages_required);
305
306static ssize_t strict_limit_store(struct device *dev,
307 struct device_attribute *attr, const char *buf, size_t count)
308{
309 struct backing_dev_info *bdi = dev_get_drvdata(dev);
310 unsigned int strict_limit;
311 ssize_t ret;
312
313 ret = kstrtouint(buf, 10, &strict_limit);
314 if (ret < 0)
315 return ret;
316
317 ret = bdi_set_strict_limit(bdi, strict_limit);
318 if (!ret)
319 ret = count;
320
321 return ret;
322}
323
324static ssize_t strict_limit_show(struct device *dev,
325 struct device_attribute *attr, char *buf)
326{
327 struct backing_dev_info *bdi = dev_get_drvdata(dev);
328
329 return sysfs_emit(buf, "%d\n",
330 !!(bdi->capabilities & BDI_CAP_STRICTLIMIT));
331}
332static DEVICE_ATTR_RW(strict_limit);
333
334static struct attribute *bdi_dev_attrs[] = {
335 &dev_attr_read_ahead_kb.attr,
336 &dev_attr_min_ratio.attr,
337 &dev_attr_min_ratio_fine.attr,
338 &dev_attr_max_ratio.attr,
339 &dev_attr_max_ratio_fine.attr,
340 &dev_attr_min_bytes.attr,
341 &dev_attr_max_bytes.attr,
342 &dev_attr_stable_pages_required.attr,
343 &dev_attr_strict_limit.attr,
344 NULL,
345};
346ATTRIBUTE_GROUPS(bdi_dev);
347
348static __init int bdi_class_init(void)
349{
350 bdi_class = class_create(THIS_MODULE, "bdi");
351 if (IS_ERR(bdi_class))
352 return PTR_ERR(bdi_class);
353
354 bdi_class->dev_groups = bdi_dev_groups;
355 bdi_debug_init();
356
357 return 0;
358}
359postcore_initcall(bdi_class_init);
360
361static int __init default_bdi_init(void)
362{
363 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
364 WQ_SYSFS, 0);
365 if (!bdi_wq)
366 return -ENOMEM;
367 return 0;
368}
369subsys_initcall(default_bdi_init);
370
371/*
372 * This function is used when the first inode for this wb is marked dirty. It
373 * wakes-up the corresponding bdi thread which should then take care of the
374 * periodic background write-out of dirty inodes. Since the write-out would
375 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
376 * set up a timer which wakes the bdi thread up later.
377 *
378 * Note, we wouldn't bother setting up the timer, but this function is on the
379 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
380 * by delaying the wake-up.
381 *
382 * We have to be careful not to postpone flush work if it is scheduled for
383 * earlier. Thus we use queue_delayed_work().
384 */
385void wb_wakeup_delayed(struct bdi_writeback *wb)
386{
387 unsigned long timeout;
388
389 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
390 spin_lock_irq(&wb->work_lock);
391 if (test_bit(WB_registered, &wb->state))
392 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
393 spin_unlock_irq(&wb->work_lock);
394}
395
396static void wb_update_bandwidth_workfn(struct work_struct *work)
397{
398 struct bdi_writeback *wb = container_of(to_delayed_work(work),
399 struct bdi_writeback, bw_dwork);
400
401 wb_update_bandwidth(wb);
402}
403
404/*
405 * Initial write bandwidth: 100 MB/s
406 */
407#define INIT_BW (100 << (20 - PAGE_SHIFT))
408
409static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
410 gfp_t gfp)
411{
412 int i, err;
413
414 memset(wb, 0, sizeof(*wb));
415
416 wb->bdi = bdi;
417 wb->last_old_flush = jiffies;
418 INIT_LIST_HEAD(&wb->b_dirty);
419 INIT_LIST_HEAD(&wb->b_io);
420 INIT_LIST_HEAD(&wb->b_more_io);
421 INIT_LIST_HEAD(&wb->b_dirty_time);
422 spin_lock_init(&wb->list_lock);
423
424 atomic_set(&wb->writeback_inodes, 0);
425 wb->bw_time_stamp = jiffies;
426 wb->balanced_dirty_ratelimit = INIT_BW;
427 wb->dirty_ratelimit = INIT_BW;
428 wb->write_bandwidth = INIT_BW;
429 wb->avg_write_bandwidth = INIT_BW;
430
431 spin_lock_init(&wb->work_lock);
432 INIT_LIST_HEAD(&wb->work_list);
433 INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
434 INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn);
435 wb->dirty_sleep = jiffies;
436
437 err = fprop_local_init_percpu(&wb->completions, gfp);
438 if (err)
439 return err;
440
441 for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
442 err = percpu_counter_init(&wb->stat[i], 0, gfp);
443 if (err)
444 goto out_destroy_stat;
445 }
446
447 return 0;
448
449out_destroy_stat:
450 while (i--)
451 percpu_counter_destroy(&wb->stat[i]);
452 fprop_local_destroy_percpu(&wb->completions);
453 return err;
454}
455
456static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
457
458/*
459 * Remove bdi from the global list and shutdown any threads we have running
460 */
461static void wb_shutdown(struct bdi_writeback *wb)
462{
463 /* Make sure nobody queues further work */
464 spin_lock_irq(&wb->work_lock);
465 if (!test_and_clear_bit(WB_registered, &wb->state)) {
466 spin_unlock_irq(&wb->work_lock);
467 return;
468 }
469 spin_unlock_irq(&wb->work_lock);
470
471 cgwb_remove_from_bdi_list(wb);
472 /*
473 * Drain work list and shutdown the delayed_work. !WB_registered
474 * tells wb_workfn() that @wb is dying and its work_list needs to
475 * be drained no matter what.
476 */
477 mod_delayed_work(bdi_wq, &wb->dwork, 0);
478 flush_delayed_work(&wb->dwork);
479 WARN_ON(!list_empty(&wb->work_list));
480 flush_delayed_work(&wb->bw_dwork);
481}
482
483static void wb_exit(struct bdi_writeback *wb)
484{
485 int i;
486
487 WARN_ON(delayed_work_pending(&wb->dwork));
488
489 for (i = 0; i < NR_WB_STAT_ITEMS; i++)
490 percpu_counter_destroy(&wb->stat[i]);
491
492 fprop_local_destroy_percpu(&wb->completions);
493}
494
495#ifdef CONFIG_CGROUP_WRITEBACK
496
497#include <linux/memcontrol.h>
498
499/*
500 * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
501 * memcg->cgwb_list. bdi->cgwb_tree is also RCU protected.
502 */
503static DEFINE_SPINLOCK(cgwb_lock);
504static struct workqueue_struct *cgwb_release_wq;
505
506static LIST_HEAD(offline_cgwbs);
507static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
508static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
509
510static void cgwb_release_workfn(struct work_struct *work)
511{
512 struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
513 release_work);
514 struct backing_dev_info *bdi = wb->bdi;
515
516 mutex_lock(&wb->bdi->cgwb_release_mutex);
517 wb_shutdown(wb);
518
519 css_put(wb->memcg_css);
520 css_put(wb->blkcg_css);
521 mutex_unlock(&wb->bdi->cgwb_release_mutex);
522
523 /* triggers blkg destruction if no online users left */
524 blkcg_unpin_online(wb->blkcg_css);
525
526 fprop_local_destroy_percpu(&wb->memcg_completions);
527
528 spin_lock_irq(&cgwb_lock);
529 list_del(&wb->offline_node);
530 spin_unlock_irq(&cgwb_lock);
531
532 percpu_ref_exit(&wb->refcnt);
533 wb_exit(wb);
534 bdi_put(bdi);
535 WARN_ON_ONCE(!list_empty(&wb->b_attached));
536 kfree_rcu(wb, rcu);
537}
538
539static void cgwb_release(struct percpu_ref *refcnt)
540{
541 struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
542 refcnt);
543 queue_work(cgwb_release_wq, &wb->release_work);
544}
545
546static void cgwb_kill(struct bdi_writeback *wb)
547{
548 lockdep_assert_held(&cgwb_lock);
549
550 WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
551 list_del(&wb->memcg_node);
552 list_del(&wb->blkcg_node);
553 list_add(&wb->offline_node, &offline_cgwbs);
554 percpu_ref_kill(&wb->refcnt);
555}
556
557static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
558{
559 spin_lock_irq(&cgwb_lock);
560 list_del_rcu(&wb->bdi_node);
561 spin_unlock_irq(&cgwb_lock);
562}
563
564static int cgwb_create(struct backing_dev_info *bdi,
565 struct cgroup_subsys_state *memcg_css, gfp_t gfp)
566{
567 struct mem_cgroup *memcg;
568 struct cgroup_subsys_state *blkcg_css;
569 struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
570 struct bdi_writeback *wb;
571 unsigned long flags;
572 int ret = 0;
573
574 memcg = mem_cgroup_from_css(memcg_css);
575 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
576 memcg_cgwb_list = &memcg->cgwb_list;
577 blkcg_cgwb_list = blkcg_get_cgwb_list(blkcg_css);
578
579 /* look up again under lock and discard on blkcg mismatch */
580 spin_lock_irqsave(&cgwb_lock, flags);
581 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
582 if (wb && wb->blkcg_css != blkcg_css) {
583 cgwb_kill(wb);
584 wb = NULL;
585 }
586 spin_unlock_irqrestore(&cgwb_lock, flags);
587 if (wb)
588 goto out_put;
589
590 /* need to create a new one */
591 wb = kmalloc(sizeof(*wb), gfp);
592 if (!wb) {
593 ret = -ENOMEM;
594 goto out_put;
595 }
596
597 ret = wb_init(wb, bdi, gfp);
598 if (ret)
599 goto err_free;
600
601 ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
602 if (ret)
603 goto err_wb_exit;
604
605 ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
606 if (ret)
607 goto err_ref_exit;
608
609 wb->memcg_css = memcg_css;
610 wb->blkcg_css = blkcg_css;
611 INIT_LIST_HEAD(&wb->b_attached);
612 INIT_WORK(&wb->release_work, cgwb_release_workfn);
613 set_bit(WB_registered, &wb->state);
614 bdi_get(bdi);
615
616 /*
617 * The root wb determines the registered state of the whole bdi and
618 * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
619 * whether they're still online. Don't link @wb if any is dead.
620 * See wb_memcg_offline() and wb_blkcg_offline().
621 */
622 ret = -ENODEV;
623 spin_lock_irqsave(&cgwb_lock, flags);
624 if (test_bit(WB_registered, &bdi->wb.state) &&
625 blkcg_cgwb_list->next && memcg_cgwb_list->next) {
626 /* we might have raced another instance of this function */
627 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
628 if (!ret) {
629 list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
630 list_add(&wb->memcg_node, memcg_cgwb_list);
631 list_add(&wb->blkcg_node, blkcg_cgwb_list);
632 blkcg_pin_online(blkcg_css);
633 css_get(memcg_css);
634 css_get(blkcg_css);
635 }
636 }
637 spin_unlock_irqrestore(&cgwb_lock, flags);
638 if (ret) {
639 if (ret == -EEXIST)
640 ret = 0;
641 goto err_fprop_exit;
642 }
643 goto out_put;
644
645err_fprop_exit:
646 bdi_put(bdi);
647 fprop_local_destroy_percpu(&wb->memcg_completions);
648err_ref_exit:
649 percpu_ref_exit(&wb->refcnt);
650err_wb_exit:
651 wb_exit(wb);
652err_free:
653 kfree(wb);
654out_put:
655 css_put(blkcg_css);
656 return ret;
657}
658
659/**
660 * wb_get_lookup - get wb for a given memcg
661 * @bdi: target bdi
662 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
663 *
664 * Try to get the wb for @memcg_css on @bdi. The returned wb has its
665 * refcount incremented.
666 *
667 * This function uses css_get() on @memcg_css and thus expects its refcnt
668 * to be positive on invocation. IOW, rcu_read_lock() protection on
669 * @memcg_css isn't enough. try_get it before calling this function.
670 *
671 * A wb is keyed by its associated memcg. As blkcg implicitly enables
672 * memcg on the default hierarchy, memcg association is guaranteed to be
673 * more specific (equal or descendant to the associated blkcg) and thus can
674 * identify both the memcg and blkcg associations.
675 *
676 * Because the blkcg associated with a memcg may change as blkcg is enabled
677 * and disabled closer to root in the hierarchy, each wb keeps track of
678 * both the memcg and blkcg associated with it and verifies the blkcg on
679 * each lookup. On mismatch, the existing wb is discarded and a new one is
680 * created.
681 */
682struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
683 struct cgroup_subsys_state *memcg_css)
684{
685 struct bdi_writeback *wb;
686
687 if (!memcg_css->parent)
688 return &bdi->wb;
689
690 rcu_read_lock();
691 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
692 if (wb) {
693 struct cgroup_subsys_state *blkcg_css;
694
695 /* see whether the blkcg association has changed */
696 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
697 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
698 wb = NULL;
699 css_put(blkcg_css);
700 }
701 rcu_read_unlock();
702
703 return wb;
704}
705
706/**
707 * wb_get_create - get wb for a given memcg, create if necessary
708 * @bdi: target bdi
709 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
710 * @gfp: allocation mask to use
711 *
712 * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
713 * create one. See wb_get_lookup() for more details.
714 */
715struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
716 struct cgroup_subsys_state *memcg_css,
717 gfp_t gfp)
718{
719 struct bdi_writeback *wb;
720
721 might_alloc(gfp);
722
723 if (!memcg_css->parent)
724 return &bdi->wb;
725
726 do {
727 wb = wb_get_lookup(bdi, memcg_css);
728 } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
729
730 return wb;
731}
732
733static int cgwb_bdi_init(struct backing_dev_info *bdi)
734{
735 int ret;
736
737 INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
738 mutex_init(&bdi->cgwb_release_mutex);
739 init_rwsem(&bdi->wb_switch_rwsem);
740
741 ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
742 if (!ret) {
743 bdi->wb.memcg_css = &root_mem_cgroup->css;
744 bdi->wb.blkcg_css = blkcg_root_css;
745 }
746 return ret;
747}
748
749static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
750{
751 struct radix_tree_iter iter;
752 void **slot;
753 struct bdi_writeback *wb;
754
755 WARN_ON(test_bit(WB_registered, &bdi->wb.state));
756
757 spin_lock_irq(&cgwb_lock);
758 radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
759 cgwb_kill(*slot);
760 spin_unlock_irq(&cgwb_lock);
761
762 mutex_lock(&bdi->cgwb_release_mutex);
763 spin_lock_irq(&cgwb_lock);
764 while (!list_empty(&bdi->wb_list)) {
765 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
766 bdi_node);
767 spin_unlock_irq(&cgwb_lock);
768 wb_shutdown(wb);
769 spin_lock_irq(&cgwb_lock);
770 }
771 spin_unlock_irq(&cgwb_lock);
772 mutex_unlock(&bdi->cgwb_release_mutex);
773}
774
775/*
776 * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
777 *
778 * Try to release dying cgwbs by switching attached inodes to the nearest
779 * living ancestor's writeback. Processed wbs are placed at the end
780 * of the list to guarantee the forward progress.
781 */
782static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
783{
784 struct bdi_writeback *wb;
785 LIST_HEAD(processed);
786
787 spin_lock_irq(&cgwb_lock);
788
789 while (!list_empty(&offline_cgwbs)) {
790 wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
791 offline_node);
792 list_move(&wb->offline_node, &processed);
793
794 /*
795 * If wb is dirty, cleaning up the writeback by switching
796 * attached inodes will result in an effective removal of any
797 * bandwidth restrictions, which isn't the goal. Instead,
798 * it can be postponed until the next time, when all io
799 * will be likely completed. If in the meantime some inodes
800 * will get re-dirtied, they should be eventually switched to
801 * a new cgwb.
802 */
803 if (wb_has_dirty_io(wb))
804 continue;
805
806 if (!wb_tryget(wb))
807 continue;
808
809 spin_unlock_irq(&cgwb_lock);
810 while (cleanup_offline_cgwb(wb))
811 cond_resched();
812 spin_lock_irq(&cgwb_lock);
813
814 wb_put(wb);
815 }
816
817 if (!list_empty(&processed))
818 list_splice_tail(&processed, &offline_cgwbs);
819
820 spin_unlock_irq(&cgwb_lock);
821}
822
823/**
824 * wb_memcg_offline - kill all wb's associated with a memcg being offlined
825 * @memcg: memcg being offlined
826 *
827 * Also prevents creation of any new wb's associated with @memcg.
828 */
829void wb_memcg_offline(struct mem_cgroup *memcg)
830{
831 struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
832 struct bdi_writeback *wb, *next;
833
834 spin_lock_irq(&cgwb_lock);
835 list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
836 cgwb_kill(wb);
837 memcg_cgwb_list->next = NULL; /* prevent new wb's */
838 spin_unlock_irq(&cgwb_lock);
839
840 queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
841}
842
843/**
844 * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
845 * @css: blkcg being offlined
846 *
847 * Also prevents creation of any new wb's associated with @blkcg.
848 */
849void wb_blkcg_offline(struct cgroup_subsys_state *css)
850{
851 struct bdi_writeback *wb, *next;
852 struct list_head *list = blkcg_get_cgwb_list(css);
853
854 spin_lock_irq(&cgwb_lock);
855 list_for_each_entry_safe(wb, next, list, blkcg_node)
856 cgwb_kill(wb);
857 list->next = NULL; /* prevent new wb's */
858 spin_unlock_irq(&cgwb_lock);
859}
860
861static void cgwb_bdi_register(struct backing_dev_info *bdi)
862{
863 spin_lock_irq(&cgwb_lock);
864 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
865 spin_unlock_irq(&cgwb_lock);
866}
867
868static int __init cgwb_init(void)
869{
870 /*
871 * There can be many concurrent release work items overwhelming
872 * system_wq. Put them in a separate wq and limit concurrency.
873 * There's no point in executing many of these in parallel.
874 */
875 cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
876 if (!cgwb_release_wq)
877 return -ENOMEM;
878
879 return 0;
880}
881subsys_initcall(cgwb_init);
882
883#else /* CONFIG_CGROUP_WRITEBACK */
884
885static int cgwb_bdi_init(struct backing_dev_info *bdi)
886{
887 return wb_init(&bdi->wb, bdi, GFP_KERNEL);
888}
889
890static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
891
892static void cgwb_bdi_register(struct backing_dev_info *bdi)
893{
894 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
895}
896
897static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
898{
899 list_del_rcu(&wb->bdi_node);
900}
901
902#endif /* CONFIG_CGROUP_WRITEBACK */
903
904int bdi_init(struct backing_dev_info *bdi)
905{
906 bdi->dev = NULL;
907
908 kref_init(&bdi->refcnt);
909 bdi->min_ratio = 0;
910 bdi->max_ratio = 100 * BDI_RATIO_SCALE;
911 bdi->max_prop_frac = FPROP_FRAC_BASE;
912 INIT_LIST_HEAD(&bdi->bdi_list);
913 INIT_LIST_HEAD(&bdi->wb_list);
914 init_waitqueue_head(&bdi->wb_waitq);
915
916 return cgwb_bdi_init(bdi);
917}
918
919struct backing_dev_info *bdi_alloc(int node_id)
920{
921 struct backing_dev_info *bdi;
922
923 bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
924 if (!bdi)
925 return NULL;
926
927 if (bdi_init(bdi)) {
928 kfree(bdi);
929 return NULL;
930 }
931 bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
932 bdi->ra_pages = VM_READAHEAD_PAGES;
933 bdi->io_pages = VM_READAHEAD_PAGES;
934 timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
935 return bdi;
936}
937EXPORT_SYMBOL(bdi_alloc);
938
939static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
940{
941 struct rb_node **p = &bdi_tree.rb_node;
942 struct rb_node *parent = NULL;
943 struct backing_dev_info *bdi;
944
945 lockdep_assert_held(&bdi_lock);
946
947 while (*p) {
948 parent = *p;
949 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
950
951 if (bdi->id > id)
952 p = &(*p)->rb_left;
953 else if (bdi->id < id)
954 p = &(*p)->rb_right;
955 else
956 break;
957 }
958
959 if (parentp)
960 *parentp = parent;
961 return p;
962}
963
964/**
965 * bdi_get_by_id - lookup and get bdi from its id
966 * @id: bdi id to lookup
967 *
968 * Find bdi matching @id and get it. Returns NULL if the matching bdi
969 * doesn't exist or is already unregistered.
970 */
971struct backing_dev_info *bdi_get_by_id(u64 id)
972{
973 struct backing_dev_info *bdi = NULL;
974 struct rb_node **p;
975
976 spin_lock_bh(&bdi_lock);
977 p = bdi_lookup_rb_node(id, NULL);
978 if (*p) {
979 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
980 bdi_get(bdi);
981 }
982 spin_unlock_bh(&bdi_lock);
983
984 return bdi;
985}
986
987int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
988{
989 struct device *dev;
990 struct rb_node *parent, **p;
991
992 if (bdi->dev) /* The driver needs to use separate queues per device */
993 return 0;
994
995 vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
996 dev = device_create(bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
997 if (IS_ERR(dev))
998 return PTR_ERR(dev);
999
1000 cgwb_bdi_register(bdi);
1001 bdi->dev = dev;
1002
1003 bdi_debug_register(bdi, dev_name(dev));
1004 set_bit(WB_registered, &bdi->wb.state);
1005
1006 spin_lock_bh(&bdi_lock);
1007
1008 bdi->id = ++bdi_id_cursor;
1009
1010 p = bdi_lookup_rb_node(bdi->id, &parent);
1011 rb_link_node(&bdi->rb_node, parent, p);
1012 rb_insert_color(&bdi->rb_node, &bdi_tree);
1013
1014 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
1015
1016 spin_unlock_bh(&bdi_lock);
1017
1018 trace_writeback_bdi_register(bdi);
1019 return 0;
1020}
1021
1022int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
1023{
1024 va_list args;
1025 int ret;
1026
1027 va_start(args, fmt);
1028 ret = bdi_register_va(bdi, fmt, args);
1029 va_end(args);
1030 return ret;
1031}
1032EXPORT_SYMBOL(bdi_register);
1033
1034void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
1035{
1036 WARN_ON_ONCE(bdi->owner);
1037 bdi->owner = owner;
1038 get_device(owner);
1039}
1040
1041/*
1042 * Remove bdi from bdi_list, and ensure that it is no longer visible
1043 */
1044static void bdi_remove_from_list(struct backing_dev_info *bdi)
1045{
1046 spin_lock_bh(&bdi_lock);
1047 rb_erase(&bdi->rb_node, &bdi_tree);
1048 list_del_rcu(&bdi->bdi_list);
1049 spin_unlock_bh(&bdi_lock);
1050
1051 synchronize_rcu_expedited();
1052}
1053
1054void bdi_unregister(struct backing_dev_info *bdi)
1055{
1056 del_timer_sync(&bdi->laptop_mode_wb_timer);
1057
1058 /* make sure nobody finds us on the bdi_list anymore */
1059 bdi_remove_from_list(bdi);
1060 wb_shutdown(&bdi->wb);
1061 cgwb_bdi_unregister(bdi);
1062
1063 /*
1064 * If this BDI's min ratio has been set, use bdi_set_min_ratio() to
1065 * update the global bdi_min_ratio.
1066 */
1067 if (bdi->min_ratio)
1068 bdi_set_min_ratio(bdi, 0);
1069
1070 if (bdi->dev) {
1071 bdi_debug_unregister(bdi);
1072 device_unregister(bdi->dev);
1073 bdi->dev = NULL;
1074 }
1075
1076 if (bdi->owner) {
1077 put_device(bdi->owner);
1078 bdi->owner = NULL;
1079 }
1080}
1081EXPORT_SYMBOL(bdi_unregister);
1082
1083static void release_bdi(struct kref *ref)
1084{
1085 struct backing_dev_info *bdi =
1086 container_of(ref, struct backing_dev_info, refcnt);
1087
1088 WARN_ON_ONCE(test_bit(WB_registered, &bdi->wb.state));
1089 WARN_ON_ONCE(bdi->dev);
1090 wb_exit(&bdi->wb);
1091 kfree(bdi);
1092}
1093
1094void bdi_put(struct backing_dev_info *bdi)
1095{
1096 kref_put(&bdi->refcnt, release_bdi);
1097}
1098EXPORT_SYMBOL(bdi_put);
1099
1100struct backing_dev_info *inode_to_bdi(struct inode *inode)
1101{
1102 struct super_block *sb;
1103
1104 if (!inode)
1105 return &noop_backing_dev_info;
1106
1107 sb = inode->i_sb;
1108#ifdef CONFIG_BLOCK
1109 if (sb_is_blkdev_sb(sb))
1110 return I_BDEV(inode)->bd_disk->bdi;
1111#endif
1112 return sb->s_bdi;
1113}
1114EXPORT_SYMBOL(inode_to_bdi);
1115
1116const char *bdi_dev_name(struct backing_dev_info *bdi)
1117{
1118 if (!bdi || !bdi->dev)
1119 return bdi_unknown_name;
1120 return bdi->dev_name;
1121}
1122EXPORT_SYMBOL_GPL(bdi_dev_name);