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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.h>
12#include <linux/module.h>
13#include <linux/writeback.h>
14#include <linux/device.h>
15#include <trace/events/writeback.h>
16
17struct backing_dev_info noop_backing_dev_info = {
18 .name = "noop",
19 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
20};
21EXPORT_SYMBOL_GPL(noop_backing_dev_info);
22
23static struct class *bdi_class;
24
25/*
26 * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
27 * reader side locking.
28 */
29DEFINE_SPINLOCK(bdi_lock);
30static u64 bdi_id_cursor;
31static struct rb_root bdi_tree = RB_ROOT;
32LIST_HEAD(bdi_list);
33
34/* bdi_wq serves all asynchronous writeback tasks */
35struct workqueue_struct *bdi_wq;
36
37#ifdef CONFIG_DEBUG_FS
38#include <linux/debugfs.h>
39#include <linux/seq_file.h>
40
41static struct dentry *bdi_debug_root;
42
43static void bdi_debug_init(void)
44{
45 bdi_debug_root = debugfs_create_dir("bdi", NULL);
46}
47
48static int bdi_debug_stats_show(struct seq_file *m, void *v)
49{
50 struct backing_dev_info *bdi = m->private;
51 struct bdi_writeback *wb = &bdi->wb;
52 unsigned long background_thresh;
53 unsigned long dirty_thresh;
54 unsigned long wb_thresh;
55 unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
56 struct inode *inode;
57
58 nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
59 spin_lock(&wb->list_lock);
60 list_for_each_entry(inode, &wb->b_dirty, i_io_list)
61 nr_dirty++;
62 list_for_each_entry(inode, &wb->b_io, i_io_list)
63 nr_io++;
64 list_for_each_entry(inode, &wb->b_more_io, i_io_list)
65 nr_more_io++;
66 list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
67 if (inode->i_state & I_DIRTY_TIME)
68 nr_dirty_time++;
69 spin_unlock(&wb->list_lock);
70
71 global_dirty_limits(&background_thresh, &dirty_thresh);
72 wb_thresh = wb_calc_thresh(wb, dirty_thresh);
73
74#define K(x) ((x) << (PAGE_SHIFT - 10))
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#undef K
104
105 return 0;
106}
107DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
108
109static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
110{
111 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
112
113 debugfs_create_file("stats", 0444, bdi->debug_dir, bdi,
114 &bdi_debug_stats_fops);
115}
116
117static void bdi_debug_unregister(struct backing_dev_info *bdi)
118{
119 debugfs_remove_recursive(bdi->debug_dir);
120}
121#else
122static inline void bdi_debug_init(void)
123{
124}
125static inline void bdi_debug_register(struct backing_dev_info *bdi,
126 const char *name)
127{
128}
129static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
130{
131}
132#endif
133
134static ssize_t read_ahead_kb_store(struct device *dev,
135 struct device_attribute *attr,
136 const char *buf, size_t count)
137{
138 struct backing_dev_info *bdi = dev_get_drvdata(dev);
139 unsigned long read_ahead_kb;
140 ssize_t ret;
141
142 ret = kstrtoul(buf, 10, &read_ahead_kb);
143 if (ret < 0)
144 return ret;
145
146 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
147
148 return count;
149}
150
151#define K(pages) ((pages) << (PAGE_SHIFT - 10))
152
153#define BDI_SHOW(name, expr) \
154static ssize_t name##_show(struct device *dev, \
155 struct device_attribute *attr, char *page) \
156{ \
157 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
158 \
159 return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
160} \
161static DEVICE_ATTR_RW(name);
162
163BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
164
165static ssize_t min_ratio_store(struct device *dev,
166 struct device_attribute *attr, const char *buf, size_t count)
167{
168 struct backing_dev_info *bdi = dev_get_drvdata(dev);
169 unsigned int ratio;
170 ssize_t ret;
171
172 ret = kstrtouint(buf, 10, &ratio);
173 if (ret < 0)
174 return ret;
175
176 ret = bdi_set_min_ratio(bdi, ratio);
177 if (!ret)
178 ret = count;
179
180 return ret;
181}
182BDI_SHOW(min_ratio, bdi->min_ratio)
183
184static ssize_t max_ratio_store(struct device *dev,
185 struct device_attribute *attr, const char *buf, size_t count)
186{
187 struct backing_dev_info *bdi = dev_get_drvdata(dev);
188 unsigned int ratio;
189 ssize_t ret;
190
191 ret = kstrtouint(buf, 10, &ratio);
192 if (ret < 0)
193 return ret;
194
195 ret = bdi_set_max_ratio(bdi, ratio);
196 if (!ret)
197 ret = count;
198
199 return ret;
200}
201BDI_SHOW(max_ratio, bdi->max_ratio)
202
203static ssize_t stable_pages_required_show(struct device *dev,
204 struct device_attribute *attr,
205 char *page)
206{
207 struct backing_dev_info *bdi = dev_get_drvdata(dev);
208
209 return snprintf(page, PAGE_SIZE-1, "%d\n",
210 bdi_cap_stable_pages_required(bdi) ? 1 : 0);
211}
212static DEVICE_ATTR_RO(stable_pages_required);
213
214static struct attribute *bdi_dev_attrs[] = {
215 &dev_attr_read_ahead_kb.attr,
216 &dev_attr_min_ratio.attr,
217 &dev_attr_max_ratio.attr,
218 &dev_attr_stable_pages_required.attr,
219 NULL,
220};
221ATTRIBUTE_GROUPS(bdi_dev);
222
223static __init int bdi_class_init(void)
224{
225 bdi_class = class_create(THIS_MODULE, "bdi");
226 if (IS_ERR(bdi_class))
227 return PTR_ERR(bdi_class);
228
229 bdi_class->dev_groups = bdi_dev_groups;
230 bdi_debug_init();
231
232 return 0;
233}
234postcore_initcall(bdi_class_init);
235
236static int bdi_init(struct backing_dev_info *bdi);
237
238static int __init default_bdi_init(void)
239{
240 int err;
241
242 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
243 WQ_SYSFS, 0);
244 if (!bdi_wq)
245 return -ENOMEM;
246
247 err = bdi_init(&noop_backing_dev_info);
248
249 return err;
250}
251subsys_initcall(default_bdi_init);
252
253/*
254 * This function is used when the first inode for this wb is marked dirty. It
255 * wakes-up the corresponding bdi thread which should then take care of the
256 * periodic background write-out of dirty inodes. Since the write-out would
257 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
258 * set up a timer which wakes the bdi thread up later.
259 *
260 * Note, we wouldn't bother setting up the timer, but this function is on the
261 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
262 * by delaying the wake-up.
263 *
264 * We have to be careful not to postpone flush work if it is scheduled for
265 * earlier. Thus we use queue_delayed_work().
266 */
267void wb_wakeup_delayed(struct bdi_writeback *wb)
268{
269 unsigned long timeout;
270
271 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
272 spin_lock_bh(&wb->work_lock);
273 if (test_bit(WB_registered, &wb->state))
274 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
275 spin_unlock_bh(&wb->work_lock);
276}
277
278/*
279 * Initial write bandwidth: 100 MB/s
280 */
281#define INIT_BW (100 << (20 - PAGE_SHIFT))
282
283static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
284 int blkcg_id, gfp_t gfp)
285{
286 int i, err;
287
288 memset(wb, 0, sizeof(*wb));
289
290 if (wb != &bdi->wb)
291 bdi_get(bdi);
292 wb->bdi = bdi;
293 wb->last_old_flush = jiffies;
294 INIT_LIST_HEAD(&wb->b_dirty);
295 INIT_LIST_HEAD(&wb->b_io);
296 INIT_LIST_HEAD(&wb->b_more_io);
297 INIT_LIST_HEAD(&wb->b_dirty_time);
298 spin_lock_init(&wb->list_lock);
299
300 wb->bw_time_stamp = jiffies;
301 wb->balanced_dirty_ratelimit = INIT_BW;
302 wb->dirty_ratelimit = INIT_BW;
303 wb->write_bandwidth = INIT_BW;
304 wb->avg_write_bandwidth = INIT_BW;
305
306 spin_lock_init(&wb->work_lock);
307 INIT_LIST_HEAD(&wb->work_list);
308 INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
309 wb->dirty_sleep = jiffies;
310
311 wb->congested = wb_congested_get_create(bdi, blkcg_id, gfp);
312 if (!wb->congested) {
313 err = -ENOMEM;
314 goto out_put_bdi;
315 }
316
317 err = fprop_local_init_percpu(&wb->completions, gfp);
318 if (err)
319 goto out_put_cong;
320
321 for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
322 err = percpu_counter_init(&wb->stat[i], 0, gfp);
323 if (err)
324 goto out_destroy_stat;
325 }
326
327 return 0;
328
329out_destroy_stat:
330 while (i--)
331 percpu_counter_destroy(&wb->stat[i]);
332 fprop_local_destroy_percpu(&wb->completions);
333out_put_cong:
334 wb_congested_put(wb->congested);
335out_put_bdi:
336 if (wb != &bdi->wb)
337 bdi_put(bdi);
338 return err;
339}
340
341static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
342
343/*
344 * Remove bdi from the global list and shutdown any threads we have running
345 */
346static void wb_shutdown(struct bdi_writeback *wb)
347{
348 /* Make sure nobody queues further work */
349 spin_lock_bh(&wb->work_lock);
350 if (!test_and_clear_bit(WB_registered, &wb->state)) {
351 spin_unlock_bh(&wb->work_lock);
352 return;
353 }
354 spin_unlock_bh(&wb->work_lock);
355
356 cgwb_remove_from_bdi_list(wb);
357 /*
358 * Drain work list and shutdown the delayed_work. !WB_registered
359 * tells wb_workfn() that @wb is dying and its work_list needs to
360 * be drained no matter what.
361 */
362 mod_delayed_work(bdi_wq, &wb->dwork, 0);
363 flush_delayed_work(&wb->dwork);
364 WARN_ON(!list_empty(&wb->work_list));
365}
366
367static void wb_exit(struct bdi_writeback *wb)
368{
369 int i;
370
371 WARN_ON(delayed_work_pending(&wb->dwork));
372
373 for (i = 0; i < NR_WB_STAT_ITEMS; i++)
374 percpu_counter_destroy(&wb->stat[i]);
375
376 fprop_local_destroy_percpu(&wb->completions);
377 wb_congested_put(wb->congested);
378 if (wb != &wb->bdi->wb)
379 bdi_put(wb->bdi);
380}
381
382#ifdef CONFIG_CGROUP_WRITEBACK
383
384#include <linux/memcontrol.h>
385
386/*
387 * cgwb_lock protects bdi->cgwb_tree, bdi->cgwb_congested_tree,
388 * blkcg->cgwb_list, and memcg->cgwb_list. bdi->cgwb_tree is also RCU
389 * protected.
390 */
391static DEFINE_SPINLOCK(cgwb_lock);
392static struct workqueue_struct *cgwb_release_wq;
393
394/**
395 * wb_congested_get_create - get or create a wb_congested
396 * @bdi: associated bdi
397 * @blkcg_id: ID of the associated blkcg
398 * @gfp: allocation mask
399 *
400 * Look up the wb_congested for @blkcg_id on @bdi. If missing, create one.
401 * The returned wb_congested has its reference count incremented. Returns
402 * NULL on failure.
403 */
404struct bdi_writeback_congested *
405wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
406{
407 struct bdi_writeback_congested *new_congested = NULL, *congested;
408 struct rb_node **node, *parent;
409 unsigned long flags;
410retry:
411 spin_lock_irqsave(&cgwb_lock, flags);
412
413 node = &bdi->cgwb_congested_tree.rb_node;
414 parent = NULL;
415
416 while (*node != NULL) {
417 parent = *node;
418 congested = rb_entry(parent, struct bdi_writeback_congested,
419 rb_node);
420 if (congested->blkcg_id < blkcg_id)
421 node = &parent->rb_left;
422 else if (congested->blkcg_id > blkcg_id)
423 node = &parent->rb_right;
424 else
425 goto found;
426 }
427
428 if (new_congested) {
429 /* !found and storage for new one already allocated, insert */
430 congested = new_congested;
431 rb_link_node(&congested->rb_node, parent, node);
432 rb_insert_color(&congested->rb_node, &bdi->cgwb_congested_tree);
433 spin_unlock_irqrestore(&cgwb_lock, flags);
434 return congested;
435 }
436
437 spin_unlock_irqrestore(&cgwb_lock, flags);
438
439 /* allocate storage for new one and retry */
440 new_congested = kzalloc(sizeof(*new_congested), gfp);
441 if (!new_congested)
442 return NULL;
443
444 refcount_set(&new_congested->refcnt, 1);
445 new_congested->__bdi = bdi;
446 new_congested->blkcg_id = blkcg_id;
447 goto retry;
448
449found:
450 refcount_inc(&congested->refcnt);
451 spin_unlock_irqrestore(&cgwb_lock, flags);
452 kfree(new_congested);
453 return congested;
454}
455
456/**
457 * wb_congested_put - put a wb_congested
458 * @congested: wb_congested to put
459 *
460 * Put @congested and destroy it if the refcnt reaches zero.
461 */
462void wb_congested_put(struct bdi_writeback_congested *congested)
463{
464 unsigned long flags;
465
466 if (!refcount_dec_and_lock_irqsave(&congested->refcnt, &cgwb_lock, &flags))
467 return;
468
469 /* bdi might already have been destroyed leaving @congested unlinked */
470 if (congested->__bdi) {
471 rb_erase(&congested->rb_node,
472 &congested->__bdi->cgwb_congested_tree);
473 congested->__bdi = NULL;
474 }
475
476 spin_unlock_irqrestore(&cgwb_lock, flags);
477 kfree(congested);
478}
479
480static void cgwb_release_workfn(struct work_struct *work)
481{
482 struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
483 release_work);
484 struct blkcg *blkcg = css_to_blkcg(wb->blkcg_css);
485
486 mutex_lock(&wb->bdi->cgwb_release_mutex);
487 wb_shutdown(wb);
488
489 css_put(wb->memcg_css);
490 css_put(wb->blkcg_css);
491 mutex_unlock(&wb->bdi->cgwb_release_mutex);
492
493 /* triggers blkg destruction if cgwb_refcnt becomes zero */
494 blkcg_cgwb_put(blkcg);
495
496 fprop_local_destroy_percpu(&wb->memcg_completions);
497 percpu_ref_exit(&wb->refcnt);
498 wb_exit(wb);
499 kfree_rcu(wb, rcu);
500}
501
502static void cgwb_release(struct percpu_ref *refcnt)
503{
504 struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
505 refcnt);
506 queue_work(cgwb_release_wq, &wb->release_work);
507}
508
509static void cgwb_kill(struct bdi_writeback *wb)
510{
511 lockdep_assert_held(&cgwb_lock);
512
513 WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
514 list_del(&wb->memcg_node);
515 list_del(&wb->blkcg_node);
516 percpu_ref_kill(&wb->refcnt);
517}
518
519static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
520{
521 spin_lock_irq(&cgwb_lock);
522 list_del_rcu(&wb->bdi_node);
523 spin_unlock_irq(&cgwb_lock);
524}
525
526static int cgwb_create(struct backing_dev_info *bdi,
527 struct cgroup_subsys_state *memcg_css, gfp_t gfp)
528{
529 struct mem_cgroup *memcg;
530 struct cgroup_subsys_state *blkcg_css;
531 struct blkcg *blkcg;
532 struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
533 struct bdi_writeback *wb;
534 unsigned long flags;
535 int ret = 0;
536
537 memcg = mem_cgroup_from_css(memcg_css);
538 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
539 blkcg = css_to_blkcg(blkcg_css);
540 memcg_cgwb_list = &memcg->cgwb_list;
541 blkcg_cgwb_list = &blkcg->cgwb_list;
542
543 /* look up again under lock and discard on blkcg mismatch */
544 spin_lock_irqsave(&cgwb_lock, flags);
545 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
546 if (wb && wb->blkcg_css != blkcg_css) {
547 cgwb_kill(wb);
548 wb = NULL;
549 }
550 spin_unlock_irqrestore(&cgwb_lock, flags);
551 if (wb)
552 goto out_put;
553
554 /* need to create a new one */
555 wb = kmalloc(sizeof(*wb), gfp);
556 if (!wb) {
557 ret = -ENOMEM;
558 goto out_put;
559 }
560
561 ret = wb_init(wb, bdi, blkcg_css->id, gfp);
562 if (ret)
563 goto err_free;
564
565 ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
566 if (ret)
567 goto err_wb_exit;
568
569 ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
570 if (ret)
571 goto err_ref_exit;
572
573 wb->memcg_css = memcg_css;
574 wb->blkcg_css = blkcg_css;
575 INIT_WORK(&wb->release_work, cgwb_release_workfn);
576 set_bit(WB_registered, &wb->state);
577
578 /*
579 * The root wb determines the registered state of the whole bdi and
580 * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
581 * whether they're still online. Don't link @wb if any is dead.
582 * See wb_memcg_offline() and wb_blkcg_offline().
583 */
584 ret = -ENODEV;
585 spin_lock_irqsave(&cgwb_lock, flags);
586 if (test_bit(WB_registered, &bdi->wb.state) &&
587 blkcg_cgwb_list->next && memcg_cgwb_list->next) {
588 /* we might have raced another instance of this function */
589 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
590 if (!ret) {
591 list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
592 list_add(&wb->memcg_node, memcg_cgwb_list);
593 list_add(&wb->blkcg_node, blkcg_cgwb_list);
594 blkcg_cgwb_get(blkcg);
595 css_get(memcg_css);
596 css_get(blkcg_css);
597 }
598 }
599 spin_unlock_irqrestore(&cgwb_lock, flags);
600 if (ret) {
601 if (ret == -EEXIST)
602 ret = 0;
603 goto err_fprop_exit;
604 }
605 goto out_put;
606
607err_fprop_exit:
608 fprop_local_destroy_percpu(&wb->memcg_completions);
609err_ref_exit:
610 percpu_ref_exit(&wb->refcnt);
611err_wb_exit:
612 wb_exit(wb);
613err_free:
614 kfree(wb);
615out_put:
616 css_put(blkcg_css);
617 return ret;
618}
619
620/**
621 * wb_get_lookup - get wb for a given memcg
622 * @bdi: target bdi
623 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
624 *
625 * Try to get the wb for @memcg_css on @bdi. The returned wb has its
626 * refcount incremented.
627 *
628 * This function uses css_get() on @memcg_css and thus expects its refcnt
629 * to be positive on invocation. IOW, rcu_read_lock() protection on
630 * @memcg_css isn't enough. try_get it before calling this function.
631 *
632 * A wb is keyed by its associated memcg. As blkcg implicitly enables
633 * memcg on the default hierarchy, memcg association is guaranteed to be
634 * more specific (equal or descendant to the associated blkcg) and thus can
635 * identify both the memcg and blkcg associations.
636 *
637 * Because the blkcg associated with a memcg may change as blkcg is enabled
638 * and disabled closer to root in the hierarchy, each wb keeps track of
639 * both the memcg and blkcg associated with it and verifies the blkcg on
640 * each lookup. On mismatch, the existing wb is discarded and a new one is
641 * created.
642 */
643struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
644 struct cgroup_subsys_state *memcg_css)
645{
646 struct bdi_writeback *wb;
647
648 if (!memcg_css->parent)
649 return &bdi->wb;
650
651 rcu_read_lock();
652 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
653 if (wb) {
654 struct cgroup_subsys_state *blkcg_css;
655
656 /* see whether the blkcg association has changed */
657 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
658 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
659 wb = NULL;
660 css_put(blkcg_css);
661 }
662 rcu_read_unlock();
663
664 return wb;
665}
666
667/**
668 * wb_get_create - get wb for a given memcg, create if necessary
669 * @bdi: target bdi
670 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
671 * @gfp: allocation mask to use
672 *
673 * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
674 * create one. See wb_get_lookup() for more details.
675 */
676struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
677 struct cgroup_subsys_state *memcg_css,
678 gfp_t gfp)
679{
680 struct bdi_writeback *wb;
681
682 might_sleep_if(gfpflags_allow_blocking(gfp));
683
684 if (!memcg_css->parent)
685 return &bdi->wb;
686
687 do {
688 wb = wb_get_lookup(bdi, memcg_css);
689 } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
690
691 return wb;
692}
693
694static int cgwb_bdi_init(struct backing_dev_info *bdi)
695{
696 int ret;
697
698 INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
699 bdi->cgwb_congested_tree = RB_ROOT;
700 mutex_init(&bdi->cgwb_release_mutex);
701 init_rwsem(&bdi->wb_switch_rwsem);
702
703 ret = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
704 if (!ret) {
705 bdi->wb.memcg_css = &root_mem_cgroup->css;
706 bdi->wb.blkcg_css = blkcg_root_css;
707 }
708 return ret;
709}
710
711static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
712{
713 struct radix_tree_iter iter;
714 void **slot;
715 struct bdi_writeback *wb;
716
717 WARN_ON(test_bit(WB_registered, &bdi->wb.state));
718
719 spin_lock_irq(&cgwb_lock);
720 radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
721 cgwb_kill(*slot);
722 spin_unlock_irq(&cgwb_lock);
723
724 mutex_lock(&bdi->cgwb_release_mutex);
725 spin_lock_irq(&cgwb_lock);
726 while (!list_empty(&bdi->wb_list)) {
727 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
728 bdi_node);
729 spin_unlock_irq(&cgwb_lock);
730 wb_shutdown(wb);
731 spin_lock_irq(&cgwb_lock);
732 }
733 spin_unlock_irq(&cgwb_lock);
734 mutex_unlock(&bdi->cgwb_release_mutex);
735}
736
737/**
738 * wb_memcg_offline - kill all wb's associated with a memcg being offlined
739 * @memcg: memcg being offlined
740 *
741 * Also prevents creation of any new wb's associated with @memcg.
742 */
743void wb_memcg_offline(struct mem_cgroup *memcg)
744{
745 struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
746 struct bdi_writeback *wb, *next;
747
748 spin_lock_irq(&cgwb_lock);
749 list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
750 cgwb_kill(wb);
751 memcg_cgwb_list->next = NULL; /* prevent new wb's */
752 spin_unlock_irq(&cgwb_lock);
753}
754
755/**
756 * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
757 * @blkcg: blkcg being offlined
758 *
759 * Also prevents creation of any new wb's associated with @blkcg.
760 */
761void wb_blkcg_offline(struct blkcg *blkcg)
762{
763 struct bdi_writeback *wb, *next;
764
765 spin_lock_irq(&cgwb_lock);
766 list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node)
767 cgwb_kill(wb);
768 blkcg->cgwb_list.next = NULL; /* prevent new wb's */
769 spin_unlock_irq(&cgwb_lock);
770}
771
772static void cgwb_bdi_exit(struct backing_dev_info *bdi)
773{
774 struct rb_node *rbn;
775
776 spin_lock_irq(&cgwb_lock);
777 while ((rbn = rb_first(&bdi->cgwb_congested_tree))) {
778 struct bdi_writeback_congested *congested =
779 rb_entry(rbn, struct bdi_writeback_congested, rb_node);
780
781 rb_erase(rbn, &bdi->cgwb_congested_tree);
782 congested->__bdi = NULL; /* mark @congested unlinked */
783 }
784 spin_unlock_irq(&cgwb_lock);
785}
786
787static void cgwb_bdi_register(struct backing_dev_info *bdi)
788{
789 spin_lock_irq(&cgwb_lock);
790 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
791 spin_unlock_irq(&cgwb_lock);
792}
793
794static int __init cgwb_init(void)
795{
796 /*
797 * There can be many concurrent release work items overwhelming
798 * system_wq. Put them in a separate wq and limit concurrency.
799 * There's no point in executing many of these in parallel.
800 */
801 cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
802 if (!cgwb_release_wq)
803 return -ENOMEM;
804
805 return 0;
806}
807subsys_initcall(cgwb_init);
808
809#else /* CONFIG_CGROUP_WRITEBACK */
810
811static int cgwb_bdi_init(struct backing_dev_info *bdi)
812{
813 int err;
814
815 bdi->wb_congested = kzalloc(sizeof(*bdi->wb_congested), GFP_KERNEL);
816 if (!bdi->wb_congested)
817 return -ENOMEM;
818
819 refcount_set(&bdi->wb_congested->refcnt, 1);
820
821 err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
822 if (err) {
823 wb_congested_put(bdi->wb_congested);
824 return err;
825 }
826 return 0;
827}
828
829static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
830
831static void cgwb_bdi_exit(struct backing_dev_info *bdi)
832{
833 wb_congested_put(bdi->wb_congested);
834}
835
836static void cgwb_bdi_register(struct backing_dev_info *bdi)
837{
838 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
839}
840
841static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
842{
843 list_del_rcu(&wb->bdi_node);
844}
845
846#endif /* CONFIG_CGROUP_WRITEBACK */
847
848static int bdi_init(struct backing_dev_info *bdi)
849{
850 int ret;
851
852 bdi->dev = NULL;
853
854 kref_init(&bdi->refcnt);
855 bdi->min_ratio = 0;
856 bdi->max_ratio = 100;
857 bdi->max_prop_frac = FPROP_FRAC_BASE;
858 INIT_LIST_HEAD(&bdi->bdi_list);
859 INIT_LIST_HEAD(&bdi->wb_list);
860 init_waitqueue_head(&bdi->wb_waitq);
861
862 ret = cgwb_bdi_init(bdi);
863
864 return ret;
865}
866
867struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id)
868{
869 struct backing_dev_info *bdi;
870
871 bdi = kmalloc_node(sizeof(struct backing_dev_info),
872 gfp_mask | __GFP_ZERO, node_id);
873 if (!bdi)
874 return NULL;
875
876 if (bdi_init(bdi)) {
877 kfree(bdi);
878 return NULL;
879 }
880 return bdi;
881}
882EXPORT_SYMBOL(bdi_alloc_node);
883
884static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
885{
886 struct rb_node **p = &bdi_tree.rb_node;
887 struct rb_node *parent = NULL;
888 struct backing_dev_info *bdi;
889
890 lockdep_assert_held(&bdi_lock);
891
892 while (*p) {
893 parent = *p;
894 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
895
896 if (bdi->id > id)
897 p = &(*p)->rb_left;
898 else if (bdi->id < id)
899 p = &(*p)->rb_right;
900 else
901 break;
902 }
903
904 if (parentp)
905 *parentp = parent;
906 return p;
907}
908
909/**
910 * bdi_get_by_id - lookup and get bdi from its id
911 * @id: bdi id to lookup
912 *
913 * Find bdi matching @id and get it. Returns NULL if the matching bdi
914 * doesn't exist or is already unregistered.
915 */
916struct backing_dev_info *bdi_get_by_id(u64 id)
917{
918 struct backing_dev_info *bdi = NULL;
919 struct rb_node **p;
920
921 spin_lock_bh(&bdi_lock);
922 p = bdi_lookup_rb_node(id, NULL);
923 if (*p) {
924 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
925 bdi_get(bdi);
926 }
927 spin_unlock_bh(&bdi_lock);
928
929 return bdi;
930}
931
932int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
933{
934 struct device *dev;
935 struct rb_node *parent, **p;
936
937 if (bdi->dev) /* The driver needs to use separate queues per device */
938 return 0;
939
940 dev = device_create_vargs(bdi_class, NULL, MKDEV(0, 0), bdi, fmt, args);
941 if (IS_ERR(dev))
942 return PTR_ERR(dev);
943
944 cgwb_bdi_register(bdi);
945 bdi->dev = dev;
946
947 bdi_debug_register(bdi, dev_name(dev));
948 set_bit(WB_registered, &bdi->wb.state);
949
950 spin_lock_bh(&bdi_lock);
951
952 bdi->id = ++bdi_id_cursor;
953
954 p = bdi_lookup_rb_node(bdi->id, &parent);
955 rb_link_node(&bdi->rb_node, parent, p);
956 rb_insert_color(&bdi->rb_node, &bdi_tree);
957
958 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
959
960 spin_unlock_bh(&bdi_lock);
961
962 trace_writeback_bdi_register(bdi);
963 return 0;
964}
965EXPORT_SYMBOL(bdi_register_va);
966
967int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
968{
969 va_list args;
970 int ret;
971
972 va_start(args, fmt);
973 ret = bdi_register_va(bdi, fmt, args);
974 va_end(args);
975 return ret;
976}
977EXPORT_SYMBOL(bdi_register);
978
979int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner)
980{
981 int rc;
982
983 rc = bdi_register(bdi, "%u:%u", MAJOR(owner->devt), MINOR(owner->devt));
984 if (rc)
985 return rc;
986 /* Leaking owner reference... */
987 WARN_ON(bdi->owner);
988 bdi->owner = owner;
989 get_device(owner);
990 return 0;
991}
992EXPORT_SYMBOL(bdi_register_owner);
993
994/*
995 * Remove bdi from bdi_list, and ensure that it is no longer visible
996 */
997static void bdi_remove_from_list(struct backing_dev_info *bdi)
998{
999 spin_lock_bh(&bdi_lock);
1000 rb_erase(&bdi->rb_node, &bdi_tree);
1001 list_del_rcu(&bdi->bdi_list);
1002 spin_unlock_bh(&bdi_lock);
1003
1004 synchronize_rcu_expedited();
1005}
1006
1007void bdi_unregister(struct backing_dev_info *bdi)
1008{
1009 /* make sure nobody finds us on the bdi_list anymore */
1010 bdi_remove_from_list(bdi);
1011 wb_shutdown(&bdi->wb);
1012 cgwb_bdi_unregister(bdi);
1013
1014 if (bdi->dev) {
1015 bdi_debug_unregister(bdi);
1016 device_unregister(bdi->dev);
1017 bdi->dev = NULL;
1018 }
1019
1020 if (bdi->owner) {
1021 put_device(bdi->owner);
1022 bdi->owner = NULL;
1023 }
1024}
1025
1026static void release_bdi(struct kref *ref)
1027{
1028 struct backing_dev_info *bdi =
1029 container_of(ref, struct backing_dev_info, refcnt);
1030
1031 if (test_bit(WB_registered, &bdi->wb.state))
1032 bdi_unregister(bdi);
1033 WARN_ON_ONCE(bdi->dev);
1034 wb_exit(&bdi->wb);
1035 cgwb_bdi_exit(bdi);
1036 kfree(bdi);
1037}
1038
1039void bdi_put(struct backing_dev_info *bdi)
1040{
1041 kref_put(&bdi->refcnt, release_bdi);
1042}
1043EXPORT_SYMBOL(bdi_put);
1044
1045static wait_queue_head_t congestion_wqh[2] = {
1046 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
1047 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
1048 };
1049static atomic_t nr_wb_congested[2];
1050
1051void clear_wb_congested(struct bdi_writeback_congested *congested, int sync)
1052{
1053 wait_queue_head_t *wqh = &congestion_wqh[sync];
1054 enum wb_congested_state bit;
1055
1056 bit = sync ? WB_sync_congested : WB_async_congested;
1057 if (test_and_clear_bit(bit, &congested->state))
1058 atomic_dec(&nr_wb_congested[sync]);
1059 smp_mb__after_atomic();
1060 if (waitqueue_active(wqh))
1061 wake_up(wqh);
1062}
1063EXPORT_SYMBOL(clear_wb_congested);
1064
1065void set_wb_congested(struct bdi_writeback_congested *congested, int sync)
1066{
1067 enum wb_congested_state bit;
1068
1069 bit = sync ? WB_sync_congested : WB_async_congested;
1070 if (!test_and_set_bit(bit, &congested->state))
1071 atomic_inc(&nr_wb_congested[sync]);
1072}
1073EXPORT_SYMBOL(set_wb_congested);
1074
1075/**
1076 * congestion_wait - wait for a backing_dev to become uncongested
1077 * @sync: SYNC or ASYNC IO
1078 * @timeout: timeout in jiffies
1079 *
1080 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
1081 * write congestion. If no backing_devs are congested then just wait for the
1082 * next write to be completed.
1083 */
1084long congestion_wait(int sync, long timeout)
1085{
1086 long ret;
1087 unsigned long start = jiffies;
1088 DEFINE_WAIT(wait);
1089 wait_queue_head_t *wqh = &congestion_wqh[sync];
1090
1091 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1092 ret = io_schedule_timeout(timeout);
1093 finish_wait(wqh, &wait);
1094
1095 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
1096 jiffies_to_usecs(jiffies - start));
1097
1098 return ret;
1099}
1100EXPORT_SYMBOL(congestion_wait);
1101
1102/**
1103 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a pgdat to complete writes
1104 * @sync: SYNC or ASYNC IO
1105 * @timeout: timeout in jiffies
1106 *
1107 * In the event of a congested backing_dev (any backing_dev) this waits
1108 * for up to @timeout jiffies for either a BDI to exit congestion of the
1109 * given @sync queue or a write to complete.
1110 *
1111 * The return value is 0 if the sleep is for the full timeout. Otherwise,
1112 * it is the number of jiffies that were still remaining when the function
1113 * returned. return_value == timeout implies the function did not sleep.
1114 */
1115long wait_iff_congested(int sync, long timeout)
1116{
1117 long ret;
1118 unsigned long start = jiffies;
1119 DEFINE_WAIT(wait);
1120 wait_queue_head_t *wqh = &congestion_wqh[sync];
1121
1122 /*
1123 * If there is no congestion, yield if necessary instead
1124 * of sleeping on the congestion queue
1125 */
1126 if (atomic_read(&nr_wb_congested[sync]) == 0) {
1127 cond_resched();
1128
1129 /* In case we scheduled, work out time remaining */
1130 ret = timeout - (jiffies - start);
1131 if (ret < 0)
1132 ret = 0;
1133
1134 goto out;
1135 }
1136
1137 /* Sleep until uncongested or a write happens */
1138 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1139 ret = io_schedule_timeout(timeout);
1140 finish_wait(wqh, &wait);
1141
1142out:
1143 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
1144 jiffies_to_usecs(jiffies - start));
1145
1146 return ret;
1147}
1148EXPORT_SYMBOL(wait_iff_congested);
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);