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1// SPDX-License-Identifier: GPL-2.0-only
2
3#include <linux/wait.h>
4#include <linux/rbtree.h>
5#include <linux/backing-dev.h>
6#include <linux/kthread.h>
7#include <linux/freezer.h>
8#include <linux/fs.h>
9#include <linux/pagemap.h>
10#include <linux/mm.h>
11#include <linux/sched/mm.h>
12#include <linux/sched.h>
13#include <linux/module.h>
14#include <linux/writeback.h>
15#include <linux/device.h>
16#include <trace/events/writeback.h>
17
18struct backing_dev_info noop_backing_dev_info;
19EXPORT_SYMBOL_GPL(noop_backing_dev_info);
20
21static struct class *bdi_class;
22static const char *bdi_unknown_name = "(unknown)";
23
24/*
25 * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
26 * reader side locking.
27 */
28DEFINE_SPINLOCK(bdi_lock);
29static u64 bdi_id_cursor;
30static struct rb_root bdi_tree = RB_ROOT;
31LIST_HEAD(bdi_list);
32
33/* bdi_wq serves all asynchronous writeback tasks */
34struct workqueue_struct *bdi_wq;
35
36#define K(x) ((x) << (PAGE_SHIFT - 10))
37
38#ifdef CONFIG_DEBUG_FS
39#include <linux/debugfs.h>
40#include <linux/seq_file.h>
41
42static struct dentry *bdi_debug_root;
43
44static void bdi_debug_init(void)
45{
46 bdi_debug_root = debugfs_create_dir("bdi", NULL);
47}
48
49static int bdi_debug_stats_show(struct seq_file *m, void *v)
50{
51 struct backing_dev_info *bdi = m->private;
52 struct bdi_writeback *wb = &bdi->wb;
53 unsigned long background_thresh;
54 unsigned long dirty_thresh;
55 unsigned long wb_thresh;
56 unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
57 struct inode *inode;
58
59 nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
60 spin_lock(&wb->list_lock);
61 list_for_each_entry(inode, &wb->b_dirty, i_io_list)
62 nr_dirty++;
63 list_for_each_entry(inode, &wb->b_io, i_io_list)
64 nr_io++;
65 list_for_each_entry(inode, &wb->b_more_io, i_io_list)
66 nr_more_io++;
67 list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
68 if (inode->i_state & I_DIRTY_TIME)
69 nr_dirty_time++;
70 spin_unlock(&wb->list_lock);
71
72 global_dirty_limits(&background_thresh, &dirty_thresh);
73 wb_thresh = wb_calc_thresh(wb, dirty_thresh);
74
75 seq_printf(m,
76 "BdiWriteback: %10lu kB\n"
77 "BdiReclaimable: %10lu kB\n"
78 "BdiDirtyThresh: %10lu kB\n"
79 "DirtyThresh: %10lu kB\n"
80 "BackgroundThresh: %10lu kB\n"
81 "BdiDirtied: %10lu kB\n"
82 "BdiWritten: %10lu kB\n"
83 "BdiWriteBandwidth: %10lu kBps\n"
84 "b_dirty: %10lu\n"
85 "b_io: %10lu\n"
86 "b_more_io: %10lu\n"
87 "b_dirty_time: %10lu\n"
88 "bdi_list: %10u\n"
89 "state: %10lx\n",
90 (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
91 (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
92 K(wb_thresh),
93 K(dirty_thresh),
94 K(background_thresh),
95 (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
96 (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
97 (unsigned long) K(wb->write_bandwidth),
98 nr_dirty,
99 nr_io,
100 nr_more_io,
101 nr_dirty_time,
102 !list_empty(&bdi->bdi_list), bdi->wb.state);
103
104 return 0;
105}
106DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
107
108static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
109{
110 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
111
112 debugfs_create_file("stats", 0444, bdi->debug_dir, bdi,
113 &bdi_debug_stats_fops);
114}
115
116static void bdi_debug_unregister(struct backing_dev_info *bdi)
117{
118 debugfs_remove_recursive(bdi->debug_dir);
119}
120#else
121static inline void bdi_debug_init(void)
122{
123}
124static inline void bdi_debug_register(struct backing_dev_info *bdi,
125 const char *name)
126{
127}
128static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
129{
130}
131#endif
132
133static ssize_t read_ahead_kb_store(struct device *dev,
134 struct device_attribute *attr,
135 const char *buf, size_t count)
136{
137 struct backing_dev_info *bdi = dev_get_drvdata(dev);
138 unsigned long read_ahead_kb;
139 ssize_t ret;
140
141 ret = kstrtoul(buf, 10, &read_ahead_kb);
142 if (ret < 0)
143 return ret;
144
145 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
146
147 return count;
148}
149
150#define BDI_SHOW(name, expr) \
151static ssize_t name##_show(struct device *dev, \
152 struct device_attribute *attr, char *buf) \
153{ \
154 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
155 \
156 return sysfs_emit(buf, "%lld\n", (long long)expr); \
157} \
158static DEVICE_ATTR_RW(name);
159
160BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
161
162static ssize_t min_ratio_store(struct device *dev,
163 struct device_attribute *attr, const char *buf, size_t count)
164{
165 struct backing_dev_info *bdi = dev_get_drvdata(dev);
166 unsigned int ratio;
167 ssize_t ret;
168
169 ret = kstrtouint(buf, 10, &ratio);
170 if (ret < 0)
171 return ret;
172
173 ret = bdi_set_min_ratio(bdi, ratio);
174 if (!ret)
175 ret = count;
176
177 return ret;
178}
179BDI_SHOW(min_ratio, bdi->min_ratio)
180
181static ssize_t max_ratio_store(struct device *dev,
182 struct device_attribute *attr, const char *buf, size_t count)
183{
184 struct backing_dev_info *bdi = dev_get_drvdata(dev);
185 unsigned int ratio;
186 ssize_t ret;
187
188 ret = kstrtouint(buf, 10, &ratio);
189 if (ret < 0)
190 return ret;
191
192 ret = bdi_set_max_ratio(bdi, ratio);
193 if (!ret)
194 ret = count;
195
196 return ret;
197}
198BDI_SHOW(max_ratio, bdi->max_ratio)
199
200static ssize_t stable_pages_required_show(struct device *dev,
201 struct device_attribute *attr,
202 char *buf)
203{
204 dev_warn_once(dev,
205 "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n");
206 return sysfs_emit(buf, "%d\n", 0);
207}
208static DEVICE_ATTR_RO(stable_pages_required);
209
210static struct attribute *bdi_dev_attrs[] = {
211 &dev_attr_read_ahead_kb.attr,
212 &dev_attr_min_ratio.attr,
213 &dev_attr_max_ratio.attr,
214 &dev_attr_stable_pages_required.attr,
215 NULL,
216};
217ATTRIBUTE_GROUPS(bdi_dev);
218
219static __init int bdi_class_init(void)
220{
221 bdi_class = class_create(THIS_MODULE, "bdi");
222 if (IS_ERR(bdi_class))
223 return PTR_ERR(bdi_class);
224
225 bdi_class->dev_groups = bdi_dev_groups;
226 bdi_debug_init();
227
228 return 0;
229}
230postcore_initcall(bdi_class_init);
231
232static int bdi_init(struct backing_dev_info *bdi);
233
234static int __init default_bdi_init(void)
235{
236 int err;
237
238 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
239 WQ_SYSFS, 0);
240 if (!bdi_wq)
241 return -ENOMEM;
242
243 err = bdi_init(&noop_backing_dev_info);
244
245 return err;
246}
247subsys_initcall(default_bdi_init);
248
249/*
250 * This function is used when the first inode for this wb is marked dirty. It
251 * wakes-up the corresponding bdi thread which should then take care of the
252 * periodic background write-out of dirty inodes. Since the write-out would
253 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
254 * set up a timer which wakes the bdi thread up later.
255 *
256 * Note, we wouldn't bother setting up the timer, but this function is on the
257 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
258 * by delaying the wake-up.
259 *
260 * We have to be careful not to postpone flush work if it is scheduled for
261 * earlier. Thus we use queue_delayed_work().
262 */
263void wb_wakeup_delayed(struct bdi_writeback *wb)
264{
265 unsigned long timeout;
266
267 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
268 spin_lock_bh(&wb->work_lock);
269 if (test_bit(WB_registered, &wb->state))
270 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
271 spin_unlock_bh(&wb->work_lock);
272}
273
274/*
275 * Initial write bandwidth: 100 MB/s
276 */
277#define INIT_BW (100 << (20 - PAGE_SHIFT))
278
279static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
280 gfp_t gfp)
281{
282 int i, err;
283
284 memset(wb, 0, sizeof(*wb));
285
286 if (wb != &bdi->wb)
287 bdi_get(bdi);
288 wb->bdi = bdi;
289 wb->last_old_flush = jiffies;
290 INIT_LIST_HEAD(&wb->b_dirty);
291 INIT_LIST_HEAD(&wb->b_io);
292 INIT_LIST_HEAD(&wb->b_more_io);
293 INIT_LIST_HEAD(&wb->b_dirty_time);
294 spin_lock_init(&wb->list_lock);
295
296 wb->bw_time_stamp = jiffies;
297 wb->balanced_dirty_ratelimit = INIT_BW;
298 wb->dirty_ratelimit = INIT_BW;
299 wb->write_bandwidth = INIT_BW;
300 wb->avg_write_bandwidth = INIT_BW;
301
302 spin_lock_init(&wb->work_lock);
303 INIT_LIST_HEAD(&wb->work_list);
304 INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
305 wb->dirty_sleep = jiffies;
306
307 err = fprop_local_init_percpu(&wb->completions, gfp);
308 if (err)
309 goto out_put_bdi;
310
311 for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
312 err = percpu_counter_init(&wb->stat[i], 0, gfp);
313 if (err)
314 goto out_destroy_stat;
315 }
316
317 return 0;
318
319out_destroy_stat:
320 while (i--)
321 percpu_counter_destroy(&wb->stat[i]);
322 fprop_local_destroy_percpu(&wb->completions);
323out_put_bdi:
324 if (wb != &bdi->wb)
325 bdi_put(bdi);
326 return err;
327}
328
329static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
330
331/*
332 * Remove bdi from the global list and shutdown any threads we have running
333 */
334static void wb_shutdown(struct bdi_writeback *wb)
335{
336 /* Make sure nobody queues further work */
337 spin_lock_bh(&wb->work_lock);
338 if (!test_and_clear_bit(WB_registered, &wb->state)) {
339 spin_unlock_bh(&wb->work_lock);
340 return;
341 }
342 spin_unlock_bh(&wb->work_lock);
343
344 cgwb_remove_from_bdi_list(wb);
345 /*
346 * Drain work list and shutdown the delayed_work. !WB_registered
347 * tells wb_workfn() that @wb is dying and its work_list needs to
348 * be drained no matter what.
349 */
350 mod_delayed_work(bdi_wq, &wb->dwork, 0);
351 flush_delayed_work(&wb->dwork);
352 WARN_ON(!list_empty(&wb->work_list));
353}
354
355static void wb_exit(struct bdi_writeback *wb)
356{
357 int i;
358
359 WARN_ON(delayed_work_pending(&wb->dwork));
360
361 for (i = 0; i < NR_WB_STAT_ITEMS; i++)
362 percpu_counter_destroy(&wb->stat[i]);
363
364 fprop_local_destroy_percpu(&wb->completions);
365 if (wb != &wb->bdi->wb)
366 bdi_put(wb->bdi);
367}
368
369#ifdef CONFIG_CGROUP_WRITEBACK
370
371#include <linux/memcontrol.h>
372
373/*
374 * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
375 * memcg->cgwb_list. bdi->cgwb_tree is also RCU protected.
376 */
377static DEFINE_SPINLOCK(cgwb_lock);
378static struct workqueue_struct *cgwb_release_wq;
379
380static LIST_HEAD(offline_cgwbs);
381static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
382static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
383
384static void cgwb_release_workfn(struct work_struct *work)
385{
386 struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
387 release_work);
388 struct blkcg *blkcg = css_to_blkcg(wb->blkcg_css);
389
390 mutex_lock(&wb->bdi->cgwb_release_mutex);
391 wb_shutdown(wb);
392
393 css_put(wb->memcg_css);
394 css_put(wb->blkcg_css);
395 mutex_unlock(&wb->bdi->cgwb_release_mutex);
396
397 /* triggers blkg destruction if no online users left */
398 blkcg_unpin_online(blkcg);
399
400 fprop_local_destroy_percpu(&wb->memcg_completions);
401
402 spin_lock_irq(&cgwb_lock);
403 list_del(&wb->offline_node);
404 spin_unlock_irq(&cgwb_lock);
405
406 percpu_ref_exit(&wb->refcnt);
407 wb_exit(wb);
408 WARN_ON_ONCE(!list_empty(&wb->b_attached));
409 kfree_rcu(wb, rcu);
410}
411
412static void cgwb_release(struct percpu_ref *refcnt)
413{
414 struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
415 refcnt);
416 queue_work(cgwb_release_wq, &wb->release_work);
417}
418
419static void cgwb_kill(struct bdi_writeback *wb)
420{
421 lockdep_assert_held(&cgwb_lock);
422
423 WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
424 list_del(&wb->memcg_node);
425 list_del(&wb->blkcg_node);
426 list_add(&wb->offline_node, &offline_cgwbs);
427 percpu_ref_kill(&wb->refcnt);
428}
429
430static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
431{
432 spin_lock_irq(&cgwb_lock);
433 list_del_rcu(&wb->bdi_node);
434 spin_unlock_irq(&cgwb_lock);
435}
436
437static int cgwb_create(struct backing_dev_info *bdi,
438 struct cgroup_subsys_state *memcg_css, gfp_t gfp)
439{
440 struct mem_cgroup *memcg;
441 struct cgroup_subsys_state *blkcg_css;
442 struct blkcg *blkcg;
443 struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
444 struct bdi_writeback *wb;
445 unsigned long flags;
446 int ret = 0;
447
448 memcg = mem_cgroup_from_css(memcg_css);
449 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
450 blkcg = css_to_blkcg(blkcg_css);
451 memcg_cgwb_list = &memcg->cgwb_list;
452 blkcg_cgwb_list = &blkcg->cgwb_list;
453
454 /* look up again under lock and discard on blkcg mismatch */
455 spin_lock_irqsave(&cgwb_lock, flags);
456 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
457 if (wb && wb->blkcg_css != blkcg_css) {
458 cgwb_kill(wb);
459 wb = NULL;
460 }
461 spin_unlock_irqrestore(&cgwb_lock, flags);
462 if (wb)
463 goto out_put;
464
465 /* need to create a new one */
466 wb = kmalloc(sizeof(*wb), gfp);
467 if (!wb) {
468 ret = -ENOMEM;
469 goto out_put;
470 }
471
472 ret = wb_init(wb, bdi, gfp);
473 if (ret)
474 goto err_free;
475
476 ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
477 if (ret)
478 goto err_wb_exit;
479
480 ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
481 if (ret)
482 goto err_ref_exit;
483
484 wb->memcg_css = memcg_css;
485 wb->blkcg_css = blkcg_css;
486 INIT_LIST_HEAD(&wb->b_attached);
487 INIT_WORK(&wb->release_work, cgwb_release_workfn);
488 set_bit(WB_registered, &wb->state);
489
490 /*
491 * The root wb determines the registered state of the whole bdi and
492 * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
493 * whether they're still online. Don't link @wb if any is dead.
494 * See wb_memcg_offline() and wb_blkcg_offline().
495 */
496 ret = -ENODEV;
497 spin_lock_irqsave(&cgwb_lock, flags);
498 if (test_bit(WB_registered, &bdi->wb.state) &&
499 blkcg_cgwb_list->next && memcg_cgwb_list->next) {
500 /* we might have raced another instance of this function */
501 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
502 if (!ret) {
503 list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
504 list_add(&wb->memcg_node, memcg_cgwb_list);
505 list_add(&wb->blkcg_node, blkcg_cgwb_list);
506 blkcg_pin_online(blkcg);
507 css_get(memcg_css);
508 css_get(blkcg_css);
509 }
510 }
511 spin_unlock_irqrestore(&cgwb_lock, flags);
512 if (ret) {
513 if (ret == -EEXIST)
514 ret = 0;
515 goto err_fprop_exit;
516 }
517 goto out_put;
518
519err_fprop_exit:
520 fprop_local_destroy_percpu(&wb->memcg_completions);
521err_ref_exit:
522 percpu_ref_exit(&wb->refcnt);
523err_wb_exit:
524 wb_exit(wb);
525err_free:
526 kfree(wb);
527out_put:
528 css_put(blkcg_css);
529 return ret;
530}
531
532/**
533 * wb_get_lookup - get wb for a given memcg
534 * @bdi: target bdi
535 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
536 *
537 * Try to get the wb for @memcg_css on @bdi. The returned wb has its
538 * refcount incremented.
539 *
540 * This function uses css_get() on @memcg_css and thus expects its refcnt
541 * to be positive on invocation. IOW, rcu_read_lock() protection on
542 * @memcg_css isn't enough. try_get it before calling this function.
543 *
544 * A wb is keyed by its associated memcg. As blkcg implicitly enables
545 * memcg on the default hierarchy, memcg association is guaranteed to be
546 * more specific (equal or descendant to the associated blkcg) and thus can
547 * identify both the memcg and blkcg associations.
548 *
549 * Because the blkcg associated with a memcg may change as blkcg is enabled
550 * and disabled closer to root in the hierarchy, each wb keeps track of
551 * both the memcg and blkcg associated with it and verifies the blkcg on
552 * each lookup. On mismatch, the existing wb is discarded and a new one is
553 * created.
554 */
555struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
556 struct cgroup_subsys_state *memcg_css)
557{
558 struct bdi_writeback *wb;
559
560 if (!memcg_css->parent)
561 return &bdi->wb;
562
563 rcu_read_lock();
564 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
565 if (wb) {
566 struct cgroup_subsys_state *blkcg_css;
567
568 /* see whether the blkcg association has changed */
569 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
570 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
571 wb = NULL;
572 css_put(blkcg_css);
573 }
574 rcu_read_unlock();
575
576 return wb;
577}
578
579/**
580 * wb_get_create - get wb for a given memcg, create if necessary
581 * @bdi: target bdi
582 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
583 * @gfp: allocation mask to use
584 *
585 * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
586 * create one. See wb_get_lookup() for more details.
587 */
588struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
589 struct cgroup_subsys_state *memcg_css,
590 gfp_t gfp)
591{
592 struct bdi_writeback *wb;
593
594 might_alloc(gfp);
595
596 if (!memcg_css->parent)
597 return &bdi->wb;
598
599 do {
600 wb = wb_get_lookup(bdi, memcg_css);
601 } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
602
603 return wb;
604}
605
606static int cgwb_bdi_init(struct backing_dev_info *bdi)
607{
608 int ret;
609
610 INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
611 mutex_init(&bdi->cgwb_release_mutex);
612 init_rwsem(&bdi->wb_switch_rwsem);
613
614 ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
615 if (!ret) {
616 bdi->wb.memcg_css = &root_mem_cgroup->css;
617 bdi->wb.blkcg_css = blkcg_root_css;
618 }
619 return ret;
620}
621
622static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
623{
624 struct radix_tree_iter iter;
625 void **slot;
626 struct bdi_writeback *wb;
627
628 WARN_ON(test_bit(WB_registered, &bdi->wb.state));
629
630 spin_lock_irq(&cgwb_lock);
631 radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
632 cgwb_kill(*slot);
633 spin_unlock_irq(&cgwb_lock);
634
635 mutex_lock(&bdi->cgwb_release_mutex);
636 spin_lock_irq(&cgwb_lock);
637 while (!list_empty(&bdi->wb_list)) {
638 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
639 bdi_node);
640 spin_unlock_irq(&cgwb_lock);
641 wb_shutdown(wb);
642 spin_lock_irq(&cgwb_lock);
643 }
644 spin_unlock_irq(&cgwb_lock);
645 mutex_unlock(&bdi->cgwb_release_mutex);
646}
647
648/*
649 * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
650 *
651 * Try to release dying cgwbs by switching attached inodes to the nearest
652 * living ancestor's writeback. Processed wbs are placed at the end
653 * of the list to guarantee the forward progress.
654 */
655static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
656{
657 struct bdi_writeback *wb;
658 LIST_HEAD(processed);
659
660 spin_lock_irq(&cgwb_lock);
661
662 while (!list_empty(&offline_cgwbs)) {
663 wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
664 offline_node);
665 list_move(&wb->offline_node, &processed);
666
667 /*
668 * If wb is dirty, cleaning up the writeback by switching
669 * attached inodes will result in an effective removal of any
670 * bandwidth restrictions, which isn't the goal. Instead,
671 * it can be postponed until the next time, when all io
672 * will be likely completed. If in the meantime some inodes
673 * will get re-dirtied, they should be eventually switched to
674 * a new cgwb.
675 */
676 if (wb_has_dirty_io(wb))
677 continue;
678
679 if (!wb_tryget(wb))
680 continue;
681
682 spin_unlock_irq(&cgwb_lock);
683 while (cleanup_offline_cgwb(wb))
684 cond_resched();
685 spin_lock_irq(&cgwb_lock);
686
687 wb_put(wb);
688 }
689
690 if (!list_empty(&processed))
691 list_splice_tail(&processed, &offline_cgwbs);
692
693 spin_unlock_irq(&cgwb_lock);
694}
695
696/**
697 * wb_memcg_offline - kill all wb's associated with a memcg being offlined
698 * @memcg: memcg being offlined
699 *
700 * Also prevents creation of any new wb's associated with @memcg.
701 */
702void wb_memcg_offline(struct mem_cgroup *memcg)
703{
704 struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
705 struct bdi_writeback *wb, *next;
706
707 spin_lock_irq(&cgwb_lock);
708 list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
709 cgwb_kill(wb);
710 memcg_cgwb_list->next = NULL; /* prevent new wb's */
711 spin_unlock_irq(&cgwb_lock);
712
713 queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
714}
715
716/**
717 * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
718 * @blkcg: blkcg being offlined
719 *
720 * Also prevents creation of any new wb's associated with @blkcg.
721 */
722void wb_blkcg_offline(struct blkcg *blkcg)
723{
724 struct bdi_writeback *wb, *next;
725
726 spin_lock_irq(&cgwb_lock);
727 list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node)
728 cgwb_kill(wb);
729 blkcg->cgwb_list.next = NULL; /* prevent new wb's */
730 spin_unlock_irq(&cgwb_lock);
731}
732
733static void cgwb_bdi_register(struct backing_dev_info *bdi)
734{
735 spin_lock_irq(&cgwb_lock);
736 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
737 spin_unlock_irq(&cgwb_lock);
738}
739
740static int __init cgwb_init(void)
741{
742 /*
743 * There can be many concurrent release work items overwhelming
744 * system_wq. Put them in a separate wq and limit concurrency.
745 * There's no point in executing many of these in parallel.
746 */
747 cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
748 if (!cgwb_release_wq)
749 return -ENOMEM;
750
751 return 0;
752}
753subsys_initcall(cgwb_init);
754
755#else /* CONFIG_CGROUP_WRITEBACK */
756
757static int cgwb_bdi_init(struct backing_dev_info *bdi)
758{
759 return wb_init(&bdi->wb, bdi, GFP_KERNEL);
760}
761
762static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
763
764static void cgwb_bdi_register(struct backing_dev_info *bdi)
765{
766 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
767}
768
769static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
770{
771 list_del_rcu(&wb->bdi_node);
772}
773
774#endif /* CONFIG_CGROUP_WRITEBACK */
775
776static int bdi_init(struct backing_dev_info *bdi)
777{
778 int ret;
779
780 bdi->dev = NULL;
781
782 kref_init(&bdi->refcnt);
783 bdi->min_ratio = 0;
784 bdi->max_ratio = 100;
785 bdi->max_prop_frac = FPROP_FRAC_BASE;
786 INIT_LIST_HEAD(&bdi->bdi_list);
787 INIT_LIST_HEAD(&bdi->wb_list);
788 init_waitqueue_head(&bdi->wb_waitq);
789
790 ret = cgwb_bdi_init(bdi);
791
792 return ret;
793}
794
795struct backing_dev_info *bdi_alloc(int node_id)
796{
797 struct backing_dev_info *bdi;
798
799 bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
800 if (!bdi)
801 return NULL;
802
803 if (bdi_init(bdi)) {
804 kfree(bdi);
805 return NULL;
806 }
807 bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
808 bdi->ra_pages = VM_READAHEAD_PAGES;
809 bdi->io_pages = VM_READAHEAD_PAGES;
810 return bdi;
811}
812EXPORT_SYMBOL(bdi_alloc);
813
814static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
815{
816 struct rb_node **p = &bdi_tree.rb_node;
817 struct rb_node *parent = NULL;
818 struct backing_dev_info *bdi;
819
820 lockdep_assert_held(&bdi_lock);
821
822 while (*p) {
823 parent = *p;
824 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
825
826 if (bdi->id > id)
827 p = &(*p)->rb_left;
828 else if (bdi->id < id)
829 p = &(*p)->rb_right;
830 else
831 break;
832 }
833
834 if (parentp)
835 *parentp = parent;
836 return p;
837}
838
839/**
840 * bdi_get_by_id - lookup and get bdi from its id
841 * @id: bdi id to lookup
842 *
843 * Find bdi matching @id and get it. Returns NULL if the matching bdi
844 * doesn't exist or is already unregistered.
845 */
846struct backing_dev_info *bdi_get_by_id(u64 id)
847{
848 struct backing_dev_info *bdi = NULL;
849 struct rb_node **p;
850
851 spin_lock_bh(&bdi_lock);
852 p = bdi_lookup_rb_node(id, NULL);
853 if (*p) {
854 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
855 bdi_get(bdi);
856 }
857 spin_unlock_bh(&bdi_lock);
858
859 return bdi;
860}
861
862int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
863{
864 struct device *dev;
865 struct rb_node *parent, **p;
866
867 if (bdi->dev) /* The driver needs to use separate queues per device */
868 return 0;
869
870 vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
871 dev = device_create(bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
872 if (IS_ERR(dev))
873 return PTR_ERR(dev);
874
875 cgwb_bdi_register(bdi);
876 bdi->dev = dev;
877
878 bdi_debug_register(bdi, dev_name(dev));
879 set_bit(WB_registered, &bdi->wb.state);
880
881 spin_lock_bh(&bdi_lock);
882
883 bdi->id = ++bdi_id_cursor;
884
885 p = bdi_lookup_rb_node(bdi->id, &parent);
886 rb_link_node(&bdi->rb_node, parent, p);
887 rb_insert_color(&bdi->rb_node, &bdi_tree);
888
889 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
890
891 spin_unlock_bh(&bdi_lock);
892
893 trace_writeback_bdi_register(bdi);
894 return 0;
895}
896
897int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
898{
899 va_list args;
900 int ret;
901
902 va_start(args, fmt);
903 ret = bdi_register_va(bdi, fmt, args);
904 va_end(args);
905 return ret;
906}
907EXPORT_SYMBOL(bdi_register);
908
909void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
910{
911 WARN_ON_ONCE(bdi->owner);
912 bdi->owner = owner;
913 get_device(owner);
914}
915
916/*
917 * Remove bdi from bdi_list, and ensure that it is no longer visible
918 */
919static void bdi_remove_from_list(struct backing_dev_info *bdi)
920{
921 spin_lock_bh(&bdi_lock);
922 rb_erase(&bdi->rb_node, &bdi_tree);
923 list_del_rcu(&bdi->bdi_list);
924 spin_unlock_bh(&bdi_lock);
925
926 synchronize_rcu_expedited();
927}
928
929void bdi_unregister(struct backing_dev_info *bdi)
930{
931 /* make sure nobody finds us on the bdi_list anymore */
932 bdi_remove_from_list(bdi);
933 wb_shutdown(&bdi->wb);
934 cgwb_bdi_unregister(bdi);
935
936 if (bdi->dev) {
937 bdi_debug_unregister(bdi);
938 device_unregister(bdi->dev);
939 bdi->dev = NULL;
940 }
941
942 if (bdi->owner) {
943 put_device(bdi->owner);
944 bdi->owner = NULL;
945 }
946}
947
948static void release_bdi(struct kref *ref)
949{
950 struct backing_dev_info *bdi =
951 container_of(ref, struct backing_dev_info, refcnt);
952
953 if (test_bit(WB_registered, &bdi->wb.state))
954 bdi_unregister(bdi);
955 WARN_ON_ONCE(bdi->dev);
956 wb_exit(&bdi->wb);
957 kfree(bdi);
958}
959
960void bdi_put(struct backing_dev_info *bdi)
961{
962 kref_put(&bdi->refcnt, release_bdi);
963}
964EXPORT_SYMBOL(bdi_put);
965
966const char *bdi_dev_name(struct backing_dev_info *bdi)
967{
968 if (!bdi || !bdi->dev)
969 return bdi_unknown_name;
970 return bdi->dev_name;
971}
972EXPORT_SYMBOL_GPL(bdi_dev_name);
973
974static wait_queue_head_t congestion_wqh[2] = {
975 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
976 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
977 };
978static atomic_t nr_wb_congested[2];
979
980void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
981{
982 wait_queue_head_t *wqh = &congestion_wqh[sync];
983 enum wb_congested_state bit;
984
985 bit = sync ? WB_sync_congested : WB_async_congested;
986 if (test_and_clear_bit(bit, &bdi->wb.congested))
987 atomic_dec(&nr_wb_congested[sync]);
988 smp_mb__after_atomic();
989 if (waitqueue_active(wqh))
990 wake_up(wqh);
991}
992EXPORT_SYMBOL(clear_bdi_congested);
993
994void set_bdi_congested(struct backing_dev_info *bdi, int sync)
995{
996 enum wb_congested_state bit;
997
998 bit = sync ? WB_sync_congested : WB_async_congested;
999 if (!test_and_set_bit(bit, &bdi->wb.congested))
1000 atomic_inc(&nr_wb_congested[sync]);
1001}
1002EXPORT_SYMBOL(set_bdi_congested);
1003
1004/**
1005 * congestion_wait - wait for a backing_dev to become uncongested
1006 * @sync: SYNC or ASYNC IO
1007 * @timeout: timeout in jiffies
1008 *
1009 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
1010 * write congestion. If no backing_devs are congested then just wait for the
1011 * next write to be completed.
1012 */
1013long congestion_wait(int sync, long timeout)
1014{
1015 long ret;
1016 unsigned long start = jiffies;
1017 DEFINE_WAIT(wait);
1018 wait_queue_head_t *wqh = &congestion_wqh[sync];
1019
1020 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1021 ret = io_schedule_timeout(timeout);
1022 finish_wait(wqh, &wait);
1023
1024 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
1025 jiffies_to_usecs(jiffies - start));
1026
1027 return ret;
1028}
1029EXPORT_SYMBOL(congestion_wait);
1030
1031/**
1032 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a pgdat to complete writes
1033 * @sync: SYNC or ASYNC IO
1034 * @timeout: timeout in jiffies
1035 *
1036 * In the event of a congested backing_dev (any backing_dev) this waits
1037 * for up to @timeout jiffies for either a BDI to exit congestion of the
1038 * given @sync queue or a write to complete.
1039 *
1040 * The return value is 0 if the sleep is for the full timeout. Otherwise,
1041 * it is the number of jiffies that were still remaining when the function
1042 * returned. return_value == timeout implies the function did not sleep.
1043 */
1044long wait_iff_congested(int sync, long timeout)
1045{
1046 long ret;
1047 unsigned long start = jiffies;
1048 DEFINE_WAIT(wait);
1049 wait_queue_head_t *wqh = &congestion_wqh[sync];
1050
1051 /*
1052 * If there is no congestion, yield if necessary instead
1053 * of sleeping on the congestion queue
1054 */
1055 if (atomic_read(&nr_wb_congested[sync]) == 0) {
1056 cond_resched();
1057
1058 /* In case we scheduled, work out time remaining */
1059 ret = timeout - (jiffies - start);
1060 if (ret < 0)
1061 ret = 0;
1062
1063 goto out;
1064 }
1065
1066 /* Sleep until uncongested or a write happens */
1067 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1068 ret = io_schedule_timeout(timeout);
1069 finish_wait(wqh, &wait);
1070
1071out:
1072 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
1073 jiffies_to_usecs(jiffies - start));
1074
1075 return ret;
1076}
1077EXPORT_SYMBOL(wait_iff_congested);
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#include "internal.h"
20
21struct backing_dev_info noop_backing_dev_info;
22EXPORT_SYMBOL_GPL(noop_backing_dev_info);
23
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#ifdef CONFIG_DEBUG_FS
39#include <linux/debugfs.h>
40#include <linux/seq_file.h>
41
42static struct dentry *bdi_debug_root;
43
44static void bdi_debug_init(void)
45{
46 bdi_debug_root = debugfs_create_dir("bdi", NULL);
47}
48
49static int bdi_debug_stats_show(struct seq_file *m, void *v)
50{
51 struct backing_dev_info *bdi = m->private;
52 struct bdi_writeback *wb = &bdi->wb;
53 unsigned long background_thresh;
54 unsigned long dirty_thresh;
55 unsigned long wb_thresh;
56 unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
57 struct inode *inode;
58
59 nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
60 spin_lock(&wb->list_lock);
61 list_for_each_entry(inode, &wb->b_dirty, i_io_list)
62 nr_dirty++;
63 list_for_each_entry(inode, &wb->b_io, i_io_list)
64 nr_io++;
65 list_for_each_entry(inode, &wb->b_more_io, i_io_list)
66 nr_more_io++;
67 list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
68 if (inode->i_state & I_DIRTY_TIME)
69 nr_dirty_time++;
70 spin_unlock(&wb->list_lock);
71
72 global_dirty_limits(&background_thresh, &dirty_thresh);
73 wb_thresh = wb_calc_thresh(wb, dirty_thresh);
74
75 seq_printf(m,
76 "BdiWriteback: %10lu kB\n"
77 "BdiReclaimable: %10lu kB\n"
78 "BdiDirtyThresh: %10lu kB\n"
79 "DirtyThresh: %10lu kB\n"
80 "BackgroundThresh: %10lu kB\n"
81 "BdiDirtied: %10lu kB\n"
82 "BdiWritten: %10lu kB\n"
83 "BdiWriteBandwidth: %10lu kBps\n"
84 "b_dirty: %10lu\n"
85 "b_io: %10lu\n"
86 "b_more_io: %10lu\n"
87 "b_dirty_time: %10lu\n"
88 "bdi_list: %10u\n"
89 "state: %10lx\n",
90 (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
91 (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
92 K(wb_thresh),
93 K(dirty_thresh),
94 K(background_thresh),
95 (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
96 (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
97 (unsigned long) K(wb->write_bandwidth),
98 nr_dirty,
99 nr_io,
100 nr_more_io,
101 nr_dirty_time,
102 !list_empty(&bdi->bdi_list), bdi->wb.state);
103
104 return 0;
105}
106DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
107
108static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
109{
110 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
111
112 debugfs_create_file("stats", 0444, bdi->debug_dir, bdi,
113 &bdi_debug_stats_fops);
114}
115
116static void bdi_debug_unregister(struct backing_dev_info *bdi)
117{
118 debugfs_remove_recursive(bdi->debug_dir);
119}
120#else
121static inline void bdi_debug_init(void)
122{
123}
124static inline void bdi_debug_register(struct backing_dev_info *bdi,
125 const char *name)
126{
127}
128static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
129{
130}
131#endif
132
133static ssize_t read_ahead_kb_store(struct device *dev,
134 struct device_attribute *attr,
135 const char *buf, size_t count)
136{
137 struct backing_dev_info *bdi = dev_get_drvdata(dev);
138 unsigned long read_ahead_kb;
139 ssize_t ret;
140
141 ret = kstrtoul(buf, 10, &read_ahead_kb);
142 if (ret < 0)
143 return ret;
144
145 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
146
147 return count;
148}
149
150#define BDI_SHOW(name, expr) \
151static ssize_t name##_show(struct device *dev, \
152 struct device_attribute *attr, char *buf) \
153{ \
154 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
155 \
156 return sysfs_emit(buf, "%lld\n", (long long)expr); \
157} \
158static DEVICE_ATTR_RW(name);
159
160BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
161
162static ssize_t min_ratio_store(struct device *dev,
163 struct device_attribute *attr, const char *buf, size_t count)
164{
165 struct backing_dev_info *bdi = dev_get_drvdata(dev);
166 unsigned int ratio;
167 ssize_t ret;
168
169 ret = kstrtouint(buf, 10, &ratio);
170 if (ret < 0)
171 return ret;
172
173 ret = bdi_set_min_ratio(bdi, ratio);
174 if (!ret)
175 ret = count;
176
177 return ret;
178}
179BDI_SHOW(min_ratio, bdi->min_ratio / BDI_RATIO_SCALE)
180
181static ssize_t min_ratio_fine_store(struct device *dev,
182 struct device_attribute *attr, const char *buf, size_t count)
183{
184 struct backing_dev_info *bdi = dev_get_drvdata(dev);
185 unsigned int ratio;
186 ssize_t ret;
187
188 ret = kstrtouint(buf, 10, &ratio);
189 if (ret < 0)
190 return ret;
191
192 ret = bdi_set_min_ratio_no_scale(bdi, ratio);
193 if (!ret)
194 ret = count;
195
196 return ret;
197}
198BDI_SHOW(min_ratio_fine, bdi->min_ratio)
199
200static ssize_t max_ratio_store(struct device *dev,
201 struct device_attribute *attr, const char *buf, size_t count)
202{
203 struct backing_dev_info *bdi = dev_get_drvdata(dev);
204 unsigned int ratio;
205 ssize_t ret;
206
207 ret = kstrtouint(buf, 10, &ratio);
208 if (ret < 0)
209 return ret;
210
211 ret = bdi_set_max_ratio(bdi, ratio);
212 if (!ret)
213 ret = count;
214
215 return ret;
216}
217BDI_SHOW(max_ratio, bdi->max_ratio / BDI_RATIO_SCALE)
218
219static ssize_t max_ratio_fine_store(struct device *dev,
220 struct device_attribute *attr, const char *buf, size_t count)
221{
222 struct backing_dev_info *bdi = dev_get_drvdata(dev);
223 unsigned int ratio;
224 ssize_t ret;
225
226 ret = kstrtouint(buf, 10, &ratio);
227 if (ret < 0)
228 return ret;
229
230 ret = bdi_set_max_ratio_no_scale(bdi, ratio);
231 if (!ret)
232 ret = count;
233
234 return ret;
235}
236BDI_SHOW(max_ratio_fine, bdi->max_ratio)
237
238static ssize_t min_bytes_show(struct device *dev,
239 struct device_attribute *attr,
240 char *buf)
241{
242 struct backing_dev_info *bdi = dev_get_drvdata(dev);
243
244 return sysfs_emit(buf, "%llu\n", bdi_get_min_bytes(bdi));
245}
246
247static ssize_t min_bytes_store(struct device *dev,
248 struct device_attribute *attr, const char *buf, size_t count)
249{
250 struct backing_dev_info *bdi = dev_get_drvdata(dev);
251 u64 bytes;
252 ssize_t ret;
253
254 ret = kstrtoull(buf, 10, &bytes);
255 if (ret < 0)
256 return ret;
257
258 ret = bdi_set_min_bytes(bdi, bytes);
259 if (!ret)
260 ret = count;
261
262 return ret;
263}
264static DEVICE_ATTR_RW(min_bytes);
265
266static ssize_t max_bytes_show(struct device *dev,
267 struct device_attribute *attr,
268 char *buf)
269{
270 struct backing_dev_info *bdi = dev_get_drvdata(dev);
271
272 return sysfs_emit(buf, "%llu\n", bdi_get_max_bytes(bdi));
273}
274
275static ssize_t max_bytes_store(struct device *dev,
276 struct device_attribute *attr, const char *buf, size_t count)
277{
278 struct backing_dev_info *bdi = dev_get_drvdata(dev);
279 u64 bytes;
280 ssize_t ret;
281
282 ret = kstrtoull(buf, 10, &bytes);
283 if (ret < 0)
284 return ret;
285
286 ret = bdi_set_max_bytes(bdi, bytes);
287 if (!ret)
288 ret = count;
289
290 return ret;
291}
292static DEVICE_ATTR_RW(max_bytes);
293
294static ssize_t stable_pages_required_show(struct device *dev,
295 struct device_attribute *attr,
296 char *buf)
297{
298 dev_warn_once(dev,
299 "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n");
300 return sysfs_emit(buf, "%d\n", 0);
301}
302static DEVICE_ATTR_RO(stable_pages_required);
303
304static ssize_t strict_limit_store(struct device *dev,
305 struct device_attribute *attr, const char *buf, size_t count)
306{
307 struct backing_dev_info *bdi = dev_get_drvdata(dev);
308 unsigned int strict_limit;
309 ssize_t ret;
310
311 ret = kstrtouint(buf, 10, &strict_limit);
312 if (ret < 0)
313 return ret;
314
315 ret = bdi_set_strict_limit(bdi, strict_limit);
316 if (!ret)
317 ret = count;
318
319 return ret;
320}
321
322static ssize_t strict_limit_show(struct device *dev,
323 struct device_attribute *attr, char *buf)
324{
325 struct backing_dev_info *bdi = dev_get_drvdata(dev);
326
327 return sysfs_emit(buf, "%d\n",
328 !!(bdi->capabilities & BDI_CAP_STRICTLIMIT));
329}
330static DEVICE_ATTR_RW(strict_limit);
331
332static struct attribute *bdi_dev_attrs[] = {
333 &dev_attr_read_ahead_kb.attr,
334 &dev_attr_min_ratio.attr,
335 &dev_attr_min_ratio_fine.attr,
336 &dev_attr_max_ratio.attr,
337 &dev_attr_max_ratio_fine.attr,
338 &dev_attr_min_bytes.attr,
339 &dev_attr_max_bytes.attr,
340 &dev_attr_stable_pages_required.attr,
341 &dev_attr_strict_limit.attr,
342 NULL,
343};
344ATTRIBUTE_GROUPS(bdi_dev);
345
346static const struct class bdi_class = {
347 .name = "bdi",
348 .dev_groups = bdi_dev_groups,
349};
350
351static __init int bdi_class_init(void)
352{
353 int ret;
354
355 ret = class_register(&bdi_class);
356 if (ret)
357 return ret;
358
359 bdi_debug_init();
360
361 return 0;
362}
363postcore_initcall(bdi_class_init);
364
365static int __init default_bdi_init(void)
366{
367 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
368 WQ_SYSFS, 0);
369 if (!bdi_wq)
370 return -ENOMEM;
371 return 0;
372}
373subsys_initcall(default_bdi_init);
374
375/*
376 * This function is used when the first inode for this wb is marked dirty. It
377 * wakes-up the corresponding bdi thread which should then take care of the
378 * periodic background write-out of dirty inodes. Since the write-out would
379 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
380 * set up a timer which wakes the bdi thread up later.
381 *
382 * Note, we wouldn't bother setting up the timer, but this function is on the
383 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
384 * by delaying the wake-up.
385 *
386 * We have to be careful not to postpone flush work if it is scheduled for
387 * earlier. Thus we use queue_delayed_work().
388 */
389void wb_wakeup_delayed(struct bdi_writeback *wb)
390{
391 unsigned long timeout;
392
393 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
394 spin_lock_irq(&wb->work_lock);
395 if (test_bit(WB_registered, &wb->state))
396 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
397 spin_unlock_irq(&wb->work_lock);
398}
399
400static void wb_update_bandwidth_workfn(struct work_struct *work)
401{
402 struct bdi_writeback *wb = container_of(to_delayed_work(work),
403 struct bdi_writeback, bw_dwork);
404
405 wb_update_bandwidth(wb);
406}
407
408/*
409 * Initial write bandwidth: 100 MB/s
410 */
411#define INIT_BW (100 << (20 - PAGE_SHIFT))
412
413static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
414 gfp_t gfp)
415{
416 int i, err;
417
418 memset(wb, 0, sizeof(*wb));
419
420 wb->bdi = bdi;
421 wb->last_old_flush = jiffies;
422 INIT_LIST_HEAD(&wb->b_dirty);
423 INIT_LIST_HEAD(&wb->b_io);
424 INIT_LIST_HEAD(&wb->b_more_io);
425 INIT_LIST_HEAD(&wb->b_dirty_time);
426 spin_lock_init(&wb->list_lock);
427
428 atomic_set(&wb->writeback_inodes, 0);
429 wb->bw_time_stamp = jiffies;
430 wb->balanced_dirty_ratelimit = INIT_BW;
431 wb->dirty_ratelimit = INIT_BW;
432 wb->write_bandwidth = INIT_BW;
433 wb->avg_write_bandwidth = INIT_BW;
434
435 spin_lock_init(&wb->work_lock);
436 INIT_LIST_HEAD(&wb->work_list);
437 INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
438 INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn);
439
440 err = fprop_local_init_percpu(&wb->completions, gfp);
441 if (err)
442 return err;
443
444 for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
445 err = percpu_counter_init(&wb->stat[i], 0, gfp);
446 if (err)
447 goto out_destroy_stat;
448 }
449
450 return 0;
451
452out_destroy_stat:
453 while (i--)
454 percpu_counter_destroy(&wb->stat[i]);
455 fprop_local_destroy_percpu(&wb->completions);
456 return err;
457}
458
459static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
460
461/*
462 * Remove bdi from the global list and shutdown any threads we have running
463 */
464static void wb_shutdown(struct bdi_writeback *wb)
465{
466 /* Make sure nobody queues further work */
467 spin_lock_irq(&wb->work_lock);
468 if (!test_and_clear_bit(WB_registered, &wb->state)) {
469 spin_unlock_irq(&wb->work_lock);
470 return;
471 }
472 spin_unlock_irq(&wb->work_lock);
473
474 cgwb_remove_from_bdi_list(wb);
475 /*
476 * Drain work list and shutdown the delayed_work. !WB_registered
477 * tells wb_workfn() that @wb is dying and its work_list needs to
478 * be drained no matter what.
479 */
480 mod_delayed_work(bdi_wq, &wb->dwork, 0);
481 flush_delayed_work(&wb->dwork);
482 WARN_ON(!list_empty(&wb->work_list));
483 flush_delayed_work(&wb->bw_dwork);
484}
485
486static void wb_exit(struct bdi_writeback *wb)
487{
488 int i;
489
490 WARN_ON(delayed_work_pending(&wb->dwork));
491
492 for (i = 0; i < NR_WB_STAT_ITEMS; i++)
493 percpu_counter_destroy(&wb->stat[i]);
494
495 fprop_local_destroy_percpu(&wb->completions);
496}
497
498#ifdef CONFIG_CGROUP_WRITEBACK
499
500#include <linux/memcontrol.h>
501
502/*
503 * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
504 * memcg->cgwb_list. bdi->cgwb_tree is also RCU protected.
505 */
506static DEFINE_SPINLOCK(cgwb_lock);
507static struct workqueue_struct *cgwb_release_wq;
508
509static LIST_HEAD(offline_cgwbs);
510static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
511static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
512
513static void cgwb_free_rcu(struct rcu_head *rcu_head)
514{
515 struct bdi_writeback *wb = container_of(rcu_head,
516 struct bdi_writeback, rcu);
517
518 percpu_ref_exit(&wb->refcnt);
519 kfree(wb);
520}
521
522static void cgwb_release_workfn(struct work_struct *work)
523{
524 struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
525 release_work);
526 struct backing_dev_info *bdi = wb->bdi;
527
528 mutex_lock(&wb->bdi->cgwb_release_mutex);
529 wb_shutdown(wb);
530
531 css_put(wb->memcg_css);
532 css_put(wb->blkcg_css);
533 mutex_unlock(&wb->bdi->cgwb_release_mutex);
534
535 /* triggers blkg destruction if no online users left */
536 blkcg_unpin_online(wb->blkcg_css);
537
538 fprop_local_destroy_percpu(&wb->memcg_completions);
539
540 spin_lock_irq(&cgwb_lock);
541 list_del(&wb->offline_node);
542 spin_unlock_irq(&cgwb_lock);
543
544 wb_exit(wb);
545 bdi_put(bdi);
546 WARN_ON_ONCE(!list_empty(&wb->b_attached));
547 call_rcu(&wb->rcu, cgwb_free_rcu);
548}
549
550static void cgwb_release(struct percpu_ref *refcnt)
551{
552 struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
553 refcnt);
554 queue_work(cgwb_release_wq, &wb->release_work);
555}
556
557static void cgwb_kill(struct bdi_writeback *wb)
558{
559 lockdep_assert_held(&cgwb_lock);
560
561 WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
562 list_del(&wb->memcg_node);
563 list_del(&wb->blkcg_node);
564 list_add(&wb->offline_node, &offline_cgwbs);
565 percpu_ref_kill(&wb->refcnt);
566}
567
568static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
569{
570 spin_lock_irq(&cgwb_lock);
571 list_del_rcu(&wb->bdi_node);
572 spin_unlock_irq(&cgwb_lock);
573}
574
575static int cgwb_create(struct backing_dev_info *bdi,
576 struct cgroup_subsys_state *memcg_css, gfp_t gfp)
577{
578 struct mem_cgroup *memcg;
579 struct cgroup_subsys_state *blkcg_css;
580 struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
581 struct bdi_writeback *wb;
582 unsigned long flags;
583 int ret = 0;
584
585 memcg = mem_cgroup_from_css(memcg_css);
586 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
587 memcg_cgwb_list = &memcg->cgwb_list;
588 blkcg_cgwb_list = blkcg_get_cgwb_list(blkcg_css);
589
590 /* look up again under lock and discard on blkcg mismatch */
591 spin_lock_irqsave(&cgwb_lock, flags);
592 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
593 if (wb && wb->blkcg_css != blkcg_css) {
594 cgwb_kill(wb);
595 wb = NULL;
596 }
597 spin_unlock_irqrestore(&cgwb_lock, flags);
598 if (wb)
599 goto out_put;
600
601 /* need to create a new one */
602 wb = kmalloc(sizeof(*wb), gfp);
603 if (!wb) {
604 ret = -ENOMEM;
605 goto out_put;
606 }
607
608 ret = wb_init(wb, bdi, gfp);
609 if (ret)
610 goto err_free;
611
612 ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
613 if (ret)
614 goto err_wb_exit;
615
616 ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
617 if (ret)
618 goto err_ref_exit;
619
620 wb->memcg_css = memcg_css;
621 wb->blkcg_css = blkcg_css;
622 INIT_LIST_HEAD(&wb->b_attached);
623 INIT_WORK(&wb->release_work, cgwb_release_workfn);
624 set_bit(WB_registered, &wb->state);
625 bdi_get(bdi);
626
627 /*
628 * The root wb determines the registered state of the whole bdi and
629 * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
630 * whether they're still online. Don't link @wb if any is dead.
631 * See wb_memcg_offline() and wb_blkcg_offline().
632 */
633 ret = -ENODEV;
634 spin_lock_irqsave(&cgwb_lock, flags);
635 if (test_bit(WB_registered, &bdi->wb.state) &&
636 blkcg_cgwb_list->next && memcg_cgwb_list->next) {
637 /* we might have raced another instance of this function */
638 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
639 if (!ret) {
640 list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
641 list_add(&wb->memcg_node, memcg_cgwb_list);
642 list_add(&wb->blkcg_node, blkcg_cgwb_list);
643 blkcg_pin_online(blkcg_css);
644 css_get(memcg_css);
645 css_get(blkcg_css);
646 }
647 }
648 spin_unlock_irqrestore(&cgwb_lock, flags);
649 if (ret) {
650 if (ret == -EEXIST)
651 ret = 0;
652 goto err_fprop_exit;
653 }
654 goto out_put;
655
656err_fprop_exit:
657 bdi_put(bdi);
658 fprop_local_destroy_percpu(&wb->memcg_completions);
659err_ref_exit:
660 percpu_ref_exit(&wb->refcnt);
661err_wb_exit:
662 wb_exit(wb);
663err_free:
664 kfree(wb);
665out_put:
666 css_put(blkcg_css);
667 return ret;
668}
669
670/**
671 * wb_get_lookup - get wb for a given memcg
672 * @bdi: target bdi
673 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
674 *
675 * Try to get the wb for @memcg_css on @bdi. The returned wb has its
676 * refcount incremented.
677 *
678 * This function uses css_get() on @memcg_css and thus expects its refcnt
679 * to be positive on invocation. IOW, rcu_read_lock() protection on
680 * @memcg_css isn't enough. try_get it before calling this function.
681 *
682 * A wb is keyed by its associated memcg. As blkcg implicitly enables
683 * memcg on the default hierarchy, memcg association is guaranteed to be
684 * more specific (equal or descendant to the associated blkcg) and thus can
685 * identify both the memcg and blkcg associations.
686 *
687 * Because the blkcg associated with a memcg may change as blkcg is enabled
688 * and disabled closer to root in the hierarchy, each wb keeps track of
689 * both the memcg and blkcg associated with it and verifies the blkcg on
690 * each lookup. On mismatch, the existing wb is discarded and a new one is
691 * created.
692 */
693struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
694 struct cgroup_subsys_state *memcg_css)
695{
696 struct bdi_writeback *wb;
697
698 if (!memcg_css->parent)
699 return &bdi->wb;
700
701 rcu_read_lock();
702 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
703 if (wb) {
704 struct cgroup_subsys_state *blkcg_css;
705
706 /* see whether the blkcg association has changed */
707 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
708 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
709 wb = NULL;
710 css_put(blkcg_css);
711 }
712 rcu_read_unlock();
713
714 return wb;
715}
716
717/**
718 * wb_get_create - get wb for a given memcg, create if necessary
719 * @bdi: target bdi
720 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
721 * @gfp: allocation mask to use
722 *
723 * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
724 * create one. See wb_get_lookup() for more details.
725 */
726struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
727 struct cgroup_subsys_state *memcg_css,
728 gfp_t gfp)
729{
730 struct bdi_writeback *wb;
731
732 might_alloc(gfp);
733
734 do {
735 wb = wb_get_lookup(bdi, memcg_css);
736 } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
737
738 return wb;
739}
740
741static int cgwb_bdi_init(struct backing_dev_info *bdi)
742{
743 int ret;
744
745 INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
746 mutex_init(&bdi->cgwb_release_mutex);
747 init_rwsem(&bdi->wb_switch_rwsem);
748
749 ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
750 if (!ret) {
751 bdi->wb.memcg_css = &root_mem_cgroup->css;
752 bdi->wb.blkcg_css = blkcg_root_css;
753 }
754 return ret;
755}
756
757static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
758{
759 struct radix_tree_iter iter;
760 void **slot;
761 struct bdi_writeback *wb;
762
763 WARN_ON(test_bit(WB_registered, &bdi->wb.state));
764
765 spin_lock_irq(&cgwb_lock);
766 radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
767 cgwb_kill(*slot);
768 spin_unlock_irq(&cgwb_lock);
769
770 mutex_lock(&bdi->cgwb_release_mutex);
771 spin_lock_irq(&cgwb_lock);
772 while (!list_empty(&bdi->wb_list)) {
773 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
774 bdi_node);
775 spin_unlock_irq(&cgwb_lock);
776 wb_shutdown(wb);
777 spin_lock_irq(&cgwb_lock);
778 }
779 spin_unlock_irq(&cgwb_lock);
780 mutex_unlock(&bdi->cgwb_release_mutex);
781}
782
783/*
784 * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
785 *
786 * Try to release dying cgwbs by switching attached inodes to the nearest
787 * living ancestor's writeback. Processed wbs are placed at the end
788 * of the list to guarantee the forward progress.
789 */
790static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
791{
792 struct bdi_writeback *wb;
793 LIST_HEAD(processed);
794
795 spin_lock_irq(&cgwb_lock);
796
797 while (!list_empty(&offline_cgwbs)) {
798 wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
799 offline_node);
800 list_move(&wb->offline_node, &processed);
801
802 /*
803 * If wb is dirty, cleaning up the writeback by switching
804 * attached inodes will result in an effective removal of any
805 * bandwidth restrictions, which isn't the goal. Instead,
806 * it can be postponed until the next time, when all io
807 * will be likely completed. If in the meantime some inodes
808 * will get re-dirtied, they should be eventually switched to
809 * a new cgwb.
810 */
811 if (wb_has_dirty_io(wb))
812 continue;
813
814 if (!wb_tryget(wb))
815 continue;
816
817 spin_unlock_irq(&cgwb_lock);
818 while (cleanup_offline_cgwb(wb))
819 cond_resched();
820 spin_lock_irq(&cgwb_lock);
821
822 wb_put(wb);
823 }
824
825 if (!list_empty(&processed))
826 list_splice_tail(&processed, &offline_cgwbs);
827
828 spin_unlock_irq(&cgwb_lock);
829}
830
831/**
832 * wb_memcg_offline - kill all wb's associated with a memcg being offlined
833 * @memcg: memcg being offlined
834 *
835 * Also prevents creation of any new wb's associated with @memcg.
836 */
837void wb_memcg_offline(struct mem_cgroup *memcg)
838{
839 struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
840 struct bdi_writeback *wb, *next;
841
842 spin_lock_irq(&cgwb_lock);
843 list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
844 cgwb_kill(wb);
845 memcg_cgwb_list->next = NULL; /* prevent new wb's */
846 spin_unlock_irq(&cgwb_lock);
847
848 queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
849}
850
851/**
852 * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
853 * @css: blkcg being offlined
854 *
855 * Also prevents creation of any new wb's associated with @blkcg.
856 */
857void wb_blkcg_offline(struct cgroup_subsys_state *css)
858{
859 struct bdi_writeback *wb, *next;
860 struct list_head *list = blkcg_get_cgwb_list(css);
861
862 spin_lock_irq(&cgwb_lock);
863 list_for_each_entry_safe(wb, next, list, blkcg_node)
864 cgwb_kill(wb);
865 list->next = NULL; /* prevent new wb's */
866 spin_unlock_irq(&cgwb_lock);
867}
868
869static void cgwb_bdi_register(struct backing_dev_info *bdi)
870{
871 spin_lock_irq(&cgwb_lock);
872 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
873 spin_unlock_irq(&cgwb_lock);
874}
875
876static int __init cgwb_init(void)
877{
878 /*
879 * There can be many concurrent release work items overwhelming
880 * system_wq. Put them in a separate wq and limit concurrency.
881 * There's no point in executing many of these in parallel.
882 */
883 cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
884 if (!cgwb_release_wq)
885 return -ENOMEM;
886
887 return 0;
888}
889subsys_initcall(cgwb_init);
890
891#else /* CONFIG_CGROUP_WRITEBACK */
892
893static int cgwb_bdi_init(struct backing_dev_info *bdi)
894{
895 return wb_init(&bdi->wb, bdi, GFP_KERNEL);
896}
897
898static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
899
900static void cgwb_bdi_register(struct backing_dev_info *bdi)
901{
902 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
903}
904
905static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
906{
907 list_del_rcu(&wb->bdi_node);
908}
909
910#endif /* CONFIG_CGROUP_WRITEBACK */
911
912int bdi_init(struct backing_dev_info *bdi)
913{
914 bdi->dev = NULL;
915
916 kref_init(&bdi->refcnt);
917 bdi->min_ratio = 0;
918 bdi->max_ratio = 100 * BDI_RATIO_SCALE;
919 bdi->max_prop_frac = FPROP_FRAC_BASE;
920 INIT_LIST_HEAD(&bdi->bdi_list);
921 INIT_LIST_HEAD(&bdi->wb_list);
922 init_waitqueue_head(&bdi->wb_waitq);
923 bdi->last_bdp_sleep = jiffies;
924
925 return cgwb_bdi_init(bdi);
926}
927
928struct backing_dev_info *bdi_alloc(int node_id)
929{
930 struct backing_dev_info *bdi;
931
932 bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
933 if (!bdi)
934 return NULL;
935
936 if (bdi_init(bdi)) {
937 kfree(bdi);
938 return NULL;
939 }
940 bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
941 bdi->ra_pages = VM_READAHEAD_PAGES;
942 bdi->io_pages = VM_READAHEAD_PAGES;
943 timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
944 return bdi;
945}
946EXPORT_SYMBOL(bdi_alloc);
947
948static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
949{
950 struct rb_node **p = &bdi_tree.rb_node;
951 struct rb_node *parent = NULL;
952 struct backing_dev_info *bdi;
953
954 lockdep_assert_held(&bdi_lock);
955
956 while (*p) {
957 parent = *p;
958 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
959
960 if (bdi->id > id)
961 p = &(*p)->rb_left;
962 else if (bdi->id < id)
963 p = &(*p)->rb_right;
964 else
965 break;
966 }
967
968 if (parentp)
969 *parentp = parent;
970 return p;
971}
972
973/**
974 * bdi_get_by_id - lookup and get bdi from its id
975 * @id: bdi id to lookup
976 *
977 * Find bdi matching @id and get it. Returns NULL if the matching bdi
978 * doesn't exist or is already unregistered.
979 */
980struct backing_dev_info *bdi_get_by_id(u64 id)
981{
982 struct backing_dev_info *bdi = NULL;
983 struct rb_node **p;
984
985 spin_lock_bh(&bdi_lock);
986 p = bdi_lookup_rb_node(id, NULL);
987 if (*p) {
988 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
989 bdi_get(bdi);
990 }
991 spin_unlock_bh(&bdi_lock);
992
993 return bdi;
994}
995
996int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
997{
998 struct device *dev;
999 struct rb_node *parent, **p;
1000
1001 if (bdi->dev) /* The driver needs to use separate queues per device */
1002 return 0;
1003
1004 vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
1005 dev = device_create(&bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
1006 if (IS_ERR(dev))
1007 return PTR_ERR(dev);
1008
1009 cgwb_bdi_register(bdi);
1010 bdi->dev = dev;
1011
1012 bdi_debug_register(bdi, dev_name(dev));
1013 set_bit(WB_registered, &bdi->wb.state);
1014
1015 spin_lock_bh(&bdi_lock);
1016
1017 bdi->id = ++bdi_id_cursor;
1018
1019 p = bdi_lookup_rb_node(bdi->id, &parent);
1020 rb_link_node(&bdi->rb_node, parent, p);
1021 rb_insert_color(&bdi->rb_node, &bdi_tree);
1022
1023 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
1024
1025 spin_unlock_bh(&bdi_lock);
1026
1027 trace_writeback_bdi_register(bdi);
1028 return 0;
1029}
1030
1031int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
1032{
1033 va_list args;
1034 int ret;
1035
1036 va_start(args, fmt);
1037 ret = bdi_register_va(bdi, fmt, args);
1038 va_end(args);
1039 return ret;
1040}
1041EXPORT_SYMBOL(bdi_register);
1042
1043void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
1044{
1045 WARN_ON_ONCE(bdi->owner);
1046 bdi->owner = owner;
1047 get_device(owner);
1048}
1049
1050/*
1051 * Remove bdi from bdi_list, and ensure that it is no longer visible
1052 */
1053static void bdi_remove_from_list(struct backing_dev_info *bdi)
1054{
1055 spin_lock_bh(&bdi_lock);
1056 rb_erase(&bdi->rb_node, &bdi_tree);
1057 list_del_rcu(&bdi->bdi_list);
1058 spin_unlock_bh(&bdi_lock);
1059
1060 synchronize_rcu_expedited();
1061}
1062
1063void bdi_unregister(struct backing_dev_info *bdi)
1064{
1065 del_timer_sync(&bdi->laptop_mode_wb_timer);
1066
1067 /* make sure nobody finds us on the bdi_list anymore */
1068 bdi_remove_from_list(bdi);
1069 wb_shutdown(&bdi->wb);
1070 cgwb_bdi_unregister(bdi);
1071
1072 /*
1073 * If this BDI's min ratio has been set, use bdi_set_min_ratio() to
1074 * update the global bdi_min_ratio.
1075 */
1076 if (bdi->min_ratio)
1077 bdi_set_min_ratio(bdi, 0);
1078
1079 if (bdi->dev) {
1080 bdi_debug_unregister(bdi);
1081 device_unregister(bdi->dev);
1082 bdi->dev = NULL;
1083 }
1084
1085 if (bdi->owner) {
1086 put_device(bdi->owner);
1087 bdi->owner = NULL;
1088 }
1089}
1090EXPORT_SYMBOL(bdi_unregister);
1091
1092static void release_bdi(struct kref *ref)
1093{
1094 struct backing_dev_info *bdi =
1095 container_of(ref, struct backing_dev_info, refcnt);
1096
1097 WARN_ON_ONCE(test_bit(WB_registered, &bdi->wb.state));
1098 WARN_ON_ONCE(bdi->dev);
1099 wb_exit(&bdi->wb);
1100 kfree(bdi);
1101}
1102
1103void bdi_put(struct backing_dev_info *bdi)
1104{
1105 kref_put(&bdi->refcnt, release_bdi);
1106}
1107EXPORT_SYMBOL(bdi_put);
1108
1109struct backing_dev_info *inode_to_bdi(struct inode *inode)
1110{
1111 struct super_block *sb;
1112
1113 if (!inode)
1114 return &noop_backing_dev_info;
1115
1116 sb = inode->i_sb;
1117#ifdef CONFIG_BLOCK
1118 if (sb_is_blkdev_sb(sb))
1119 return I_BDEV(inode)->bd_disk->bdi;
1120#endif
1121 return sb->s_bdi;
1122}
1123EXPORT_SYMBOL(inode_to_bdi);
1124
1125const char *bdi_dev_name(struct backing_dev_info *bdi)
1126{
1127 if (!bdi || !bdi->dev)
1128 return bdi_unknown_name;
1129 return bdi->dev_name;
1130}
1131EXPORT_SYMBOL_GPL(bdi_dev_name);