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