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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
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
314 wb->congested = wb_congested_get_create(bdi, blkcg_id, gfp);
315 if (!wb->congested)
316 return -ENOMEM;
317
318 err = fprop_local_init_percpu(&wb->completions, gfp);
319 if (err)
320 goto out_put_cong;
321
322 for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
323 err = percpu_counter_init(&wb->stat[i], 0, gfp);
324 if (err)
325 goto out_destroy_stat;
326 }
327
328 return 0;
329
330out_destroy_stat:
331 while (i--)
332 percpu_counter_destroy(&wb->stat[i]);
333 fprop_local_destroy_percpu(&wb->completions);
334out_put_cong:
335 wb_congested_put(wb->congested);
336 return err;
337}
338
339/*
340 * Remove bdi from the global list and shutdown any threads we have running
341 */
342static void wb_shutdown(struct bdi_writeback *wb)
343{
344 /* Make sure nobody queues further work */
345 spin_lock_bh(&wb->work_lock);
346 if (!test_and_clear_bit(WB_registered, &wb->state)) {
347 spin_unlock_bh(&wb->work_lock);
348 return;
349 }
350 spin_unlock_bh(&wb->work_lock);
351
352 /*
353 * Drain work list and shutdown the delayed_work. !WB_registered
354 * tells wb_workfn() that @wb is dying and its work_list needs to
355 * be drained no matter what.
356 */
357 mod_delayed_work(bdi_wq, &wb->dwork, 0);
358 flush_delayed_work(&wb->dwork);
359 WARN_ON(!list_empty(&wb->work_list));
360}
361
362static void wb_exit(struct bdi_writeback *wb)
363{
364 int i;
365
366 WARN_ON(delayed_work_pending(&wb->dwork));
367
368 for (i = 0; i < NR_WB_STAT_ITEMS; i++)
369 percpu_counter_destroy(&wb->stat[i]);
370
371 fprop_local_destroy_percpu(&wb->completions);
372 wb_congested_put(wb->congested);
373}
374
375#ifdef CONFIG_CGROUP_WRITEBACK
376
377#include <linux/memcontrol.h>
378
379/*
380 * cgwb_lock protects bdi->cgwb_tree, bdi->cgwb_congested_tree,
381 * blkcg->cgwb_list, and memcg->cgwb_list. bdi->cgwb_tree is also RCU
382 * protected. cgwb_release_wait is used to wait for the completion of cgwb
383 * releases from bdi destruction path.
384 */
385static DEFINE_SPINLOCK(cgwb_lock);
386static DECLARE_WAIT_QUEUE_HEAD(cgwb_release_wait);
387
388/**
389 * wb_congested_get_create - get or create a wb_congested
390 * @bdi: associated bdi
391 * @blkcg_id: ID of the associated blkcg
392 * @gfp: allocation mask
393 *
394 * Look up the wb_congested for @blkcg_id on @bdi. If missing, create one.
395 * The returned wb_congested has its reference count incremented. Returns
396 * NULL on failure.
397 */
398struct bdi_writeback_congested *
399wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
400{
401 struct bdi_writeback_congested *new_congested = NULL, *congested;
402 struct rb_node **node, *parent;
403 unsigned long flags;
404retry:
405 spin_lock_irqsave(&cgwb_lock, flags);
406
407 node = &bdi->cgwb_congested_tree.rb_node;
408 parent = NULL;
409
410 while (*node != NULL) {
411 parent = *node;
412 congested = container_of(parent, struct bdi_writeback_congested,
413 rb_node);
414 if (congested->blkcg_id < blkcg_id)
415 node = &parent->rb_left;
416 else if (congested->blkcg_id > blkcg_id)
417 node = &parent->rb_right;
418 else
419 goto found;
420 }
421
422 if (new_congested) {
423 /* !found and storage for new one already allocated, insert */
424 congested = new_congested;
425 new_congested = NULL;
426 rb_link_node(&congested->rb_node, parent, node);
427 rb_insert_color(&congested->rb_node, &bdi->cgwb_congested_tree);
428 goto found;
429 }
430
431 spin_unlock_irqrestore(&cgwb_lock, flags);
432
433 /* allocate storage for new one and retry */
434 new_congested = kzalloc(sizeof(*new_congested), gfp);
435 if (!new_congested)
436 return NULL;
437
438 atomic_set(&new_congested->refcnt, 0);
439 new_congested->bdi = bdi;
440 new_congested->blkcg_id = blkcg_id;
441 goto retry;
442
443found:
444 atomic_inc(&congested->refcnt);
445 spin_unlock_irqrestore(&cgwb_lock, flags);
446 kfree(new_congested);
447 return congested;
448}
449
450/**
451 * wb_congested_put - put a wb_congested
452 * @congested: wb_congested to put
453 *
454 * Put @congested and destroy it if the refcnt reaches zero.
455 */
456void wb_congested_put(struct bdi_writeback_congested *congested)
457{
458 unsigned long flags;
459
460 local_irq_save(flags);
461 if (!atomic_dec_and_lock(&congested->refcnt, &cgwb_lock)) {
462 local_irq_restore(flags);
463 return;
464 }
465
466 /* bdi might already have been destroyed leaving @congested unlinked */
467 if (congested->bdi) {
468 rb_erase(&congested->rb_node,
469 &congested->bdi->cgwb_congested_tree);
470 congested->bdi = NULL;
471 }
472
473 spin_unlock_irqrestore(&cgwb_lock, flags);
474 kfree(congested);
475}
476
477static void cgwb_release_workfn(struct work_struct *work)
478{
479 struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
480 release_work);
481 struct backing_dev_info *bdi = wb->bdi;
482
483 spin_lock_irq(&cgwb_lock);
484 list_del_rcu(&wb->bdi_node);
485 spin_unlock_irq(&cgwb_lock);
486
487 wb_shutdown(wb);
488
489 css_put(wb->memcg_css);
490 css_put(wb->blkcg_css);
491
492 fprop_local_destroy_percpu(&wb->memcg_completions);
493 percpu_ref_exit(&wb->refcnt);
494 wb_exit(wb);
495 kfree_rcu(wb, rcu);
496
497 if (atomic_dec_and_test(&bdi->usage_cnt))
498 wake_up_all(&cgwb_release_wait);
499}
500
501static void cgwb_release(struct percpu_ref *refcnt)
502{
503 struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
504 refcnt);
505 schedule_work(&wb->release_work);
506}
507
508static void cgwb_kill(struct bdi_writeback *wb)
509{
510 lockdep_assert_held(&cgwb_lock);
511
512 WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
513 list_del(&wb->memcg_node);
514 list_del(&wb->blkcg_node);
515 percpu_ref_kill(&wb->refcnt);
516}
517
518static int cgwb_create(struct backing_dev_info *bdi,
519 struct cgroup_subsys_state *memcg_css, gfp_t gfp)
520{
521 struct mem_cgroup *memcg;
522 struct cgroup_subsys_state *blkcg_css;
523 struct blkcg *blkcg;
524 struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
525 struct bdi_writeback *wb;
526 unsigned long flags;
527 int ret = 0;
528
529 memcg = mem_cgroup_from_css(memcg_css);
530 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
531 blkcg = css_to_blkcg(blkcg_css);
532 memcg_cgwb_list = mem_cgroup_cgwb_list(memcg);
533 blkcg_cgwb_list = &blkcg->cgwb_list;
534
535 /* look up again under lock and discard on blkcg mismatch */
536 spin_lock_irqsave(&cgwb_lock, flags);
537 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
538 if (wb && wb->blkcg_css != blkcg_css) {
539 cgwb_kill(wb);
540 wb = NULL;
541 }
542 spin_unlock_irqrestore(&cgwb_lock, flags);
543 if (wb)
544 goto out_put;
545
546 /* need to create a new one */
547 wb = kmalloc(sizeof(*wb), gfp);
548 if (!wb)
549 return -ENOMEM;
550
551 ret = wb_init(wb, bdi, blkcg_css->id, gfp);
552 if (ret)
553 goto err_free;
554
555 ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
556 if (ret)
557 goto err_wb_exit;
558
559 ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
560 if (ret)
561 goto err_ref_exit;
562
563 wb->memcg_css = memcg_css;
564 wb->blkcg_css = blkcg_css;
565 INIT_WORK(&wb->release_work, cgwb_release_workfn);
566 set_bit(WB_registered, &wb->state);
567
568 /*
569 * The root wb determines the registered state of the whole bdi and
570 * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
571 * whether they're still online. Don't link @wb if any is dead.
572 * See wb_memcg_offline() and wb_blkcg_offline().
573 */
574 ret = -ENODEV;
575 spin_lock_irqsave(&cgwb_lock, flags);
576 if (test_bit(WB_registered, &bdi->wb.state) &&
577 blkcg_cgwb_list->next && memcg_cgwb_list->next) {
578 /* we might have raced another instance of this function */
579 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
580 if (!ret) {
581 atomic_inc(&bdi->usage_cnt);
582 list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
583 list_add(&wb->memcg_node, memcg_cgwb_list);
584 list_add(&wb->blkcg_node, blkcg_cgwb_list);
585 css_get(memcg_css);
586 css_get(blkcg_css);
587 }
588 }
589 spin_unlock_irqrestore(&cgwb_lock, flags);
590 if (ret) {
591 if (ret == -EEXIST)
592 ret = 0;
593 goto err_fprop_exit;
594 }
595 goto out_put;
596
597err_fprop_exit:
598 fprop_local_destroy_percpu(&wb->memcg_completions);
599err_ref_exit:
600 percpu_ref_exit(&wb->refcnt);
601err_wb_exit:
602 wb_exit(wb);
603err_free:
604 kfree(wb);
605out_put:
606 css_put(blkcg_css);
607 return ret;
608}
609
610/**
611 * wb_get_create - get wb for a given memcg, create if necessary
612 * @bdi: target bdi
613 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
614 * @gfp: allocation mask to use
615 *
616 * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
617 * create one. The returned wb has its refcount incremented.
618 *
619 * This function uses css_get() on @memcg_css and thus expects its refcnt
620 * to be positive on invocation. IOW, rcu_read_lock() protection on
621 * @memcg_css isn't enough. try_get it before calling this function.
622 *
623 * A wb is keyed by its associated memcg. As blkcg implicitly enables
624 * memcg on the default hierarchy, memcg association is guaranteed to be
625 * more specific (equal or descendant to the associated blkcg) and thus can
626 * identify both the memcg and blkcg associations.
627 *
628 * Because the blkcg associated with a memcg may change as blkcg is enabled
629 * and disabled closer to root in the hierarchy, each wb keeps track of
630 * both the memcg and blkcg associated with it and verifies the blkcg on
631 * each lookup. On mismatch, the existing wb is discarded and a new one is
632 * created.
633 */
634struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
635 struct cgroup_subsys_state *memcg_css,
636 gfp_t gfp)
637{
638 struct bdi_writeback *wb;
639
640 might_sleep_if(gfpflags_allow_blocking(gfp));
641
642 if (!memcg_css->parent)
643 return &bdi->wb;
644
645 do {
646 rcu_read_lock();
647 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
648 if (wb) {
649 struct cgroup_subsys_state *blkcg_css;
650
651 /* see whether the blkcg association has changed */
652 blkcg_css = cgroup_get_e_css(memcg_css->cgroup,
653 &io_cgrp_subsys);
654 if (unlikely(wb->blkcg_css != blkcg_css ||
655 !wb_tryget(wb)))
656 wb = NULL;
657 css_put(blkcg_css);
658 }
659 rcu_read_unlock();
660 } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
661
662 return wb;
663}
664
665static int cgwb_bdi_init(struct backing_dev_info *bdi)
666{
667 int ret;
668
669 INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
670 bdi->cgwb_congested_tree = RB_ROOT;
671 atomic_set(&bdi->usage_cnt, 1);
672
673 ret = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
674 if (!ret) {
675 bdi->wb.memcg_css = &root_mem_cgroup->css;
676 bdi->wb.blkcg_css = blkcg_root_css;
677 }
678 return ret;
679}
680
681static void cgwb_bdi_destroy(struct backing_dev_info *bdi)
682{
683 struct radix_tree_iter iter;
684 struct rb_node *rbn;
685 void **slot;
686
687 WARN_ON(test_bit(WB_registered, &bdi->wb.state));
688
689 spin_lock_irq(&cgwb_lock);
690
691 radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
692 cgwb_kill(*slot);
693
694 while ((rbn = rb_first(&bdi->cgwb_congested_tree))) {
695 struct bdi_writeback_congested *congested =
696 rb_entry(rbn, struct bdi_writeback_congested, rb_node);
697
698 rb_erase(rbn, &bdi->cgwb_congested_tree);
699 congested->bdi = NULL; /* mark @congested unlinked */
700 }
701
702 spin_unlock_irq(&cgwb_lock);
703
704 /*
705 * All cgwb's and their congested states must be shutdown and
706 * released before returning. Drain the usage counter to wait for
707 * all cgwb's and cgwb_congested's ever created on @bdi.
708 */
709 atomic_dec(&bdi->usage_cnt);
710 wait_event(cgwb_release_wait, !atomic_read(&bdi->usage_cnt));
711}
712
713/**
714 * wb_memcg_offline - kill all wb's associated with a memcg being offlined
715 * @memcg: memcg being offlined
716 *
717 * Also prevents creation of any new wb's associated with @memcg.
718 */
719void wb_memcg_offline(struct mem_cgroup *memcg)
720{
721 LIST_HEAD(to_destroy);
722 struct list_head *memcg_cgwb_list = mem_cgroup_cgwb_list(memcg);
723 struct bdi_writeback *wb, *next;
724
725 spin_lock_irq(&cgwb_lock);
726 list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
727 cgwb_kill(wb);
728 memcg_cgwb_list->next = NULL; /* prevent new wb's */
729 spin_unlock_irq(&cgwb_lock);
730}
731
732/**
733 * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
734 * @blkcg: blkcg being offlined
735 *
736 * Also prevents creation of any new wb's associated with @blkcg.
737 */
738void wb_blkcg_offline(struct blkcg *blkcg)
739{
740 LIST_HEAD(to_destroy);
741 struct bdi_writeback *wb, *next;
742
743 spin_lock_irq(&cgwb_lock);
744 list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node)
745 cgwb_kill(wb);
746 blkcg->cgwb_list.next = NULL; /* prevent new wb's */
747 spin_unlock_irq(&cgwb_lock);
748}
749
750#else /* CONFIG_CGROUP_WRITEBACK */
751
752static int cgwb_bdi_init(struct backing_dev_info *bdi)
753{
754 int err;
755
756 bdi->wb_congested = kzalloc(sizeof(*bdi->wb_congested), GFP_KERNEL);
757 if (!bdi->wb_congested)
758 return -ENOMEM;
759
760 err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
761 if (err) {
762 kfree(bdi->wb_congested);
763 return err;
764 }
765 return 0;
766}
767
768static void cgwb_bdi_destroy(struct backing_dev_info *bdi) { }
769
770#endif /* CONFIG_CGROUP_WRITEBACK */
771
772int bdi_init(struct backing_dev_info *bdi)
773{
774 int ret;
775
776 bdi->dev = NULL;
777
778 bdi->min_ratio = 0;
779 bdi->max_ratio = 100;
780 bdi->max_prop_frac = FPROP_FRAC_BASE;
781 INIT_LIST_HEAD(&bdi->bdi_list);
782 INIT_LIST_HEAD(&bdi->wb_list);
783 init_waitqueue_head(&bdi->wb_waitq);
784
785 ret = cgwb_bdi_init(bdi);
786
787 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
788
789 return ret;
790}
791EXPORT_SYMBOL(bdi_init);
792
793int bdi_register(struct backing_dev_info *bdi, struct device *parent,
794 const char *fmt, ...)
795{
796 va_list args;
797 struct device *dev;
798
799 if (bdi->dev) /* The driver needs to use separate queues per device */
800 return 0;
801
802 va_start(args, fmt);
803 dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
804 va_end(args);
805 if (IS_ERR(dev))
806 return PTR_ERR(dev);
807
808 bdi->dev = dev;
809
810 bdi_debug_register(bdi, dev_name(dev));
811 set_bit(WB_registered, &bdi->wb.state);
812
813 spin_lock_bh(&bdi_lock);
814 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
815 spin_unlock_bh(&bdi_lock);
816
817 trace_writeback_bdi_register(bdi);
818 return 0;
819}
820EXPORT_SYMBOL(bdi_register);
821
822int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
823{
824 return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
825}
826EXPORT_SYMBOL(bdi_register_dev);
827
828/*
829 * Remove bdi from bdi_list, and ensure that it is no longer visible
830 */
831static void bdi_remove_from_list(struct backing_dev_info *bdi)
832{
833 spin_lock_bh(&bdi_lock);
834 list_del_rcu(&bdi->bdi_list);
835 spin_unlock_bh(&bdi_lock);
836
837 synchronize_rcu_expedited();
838}
839
840void bdi_unregister(struct backing_dev_info *bdi)
841{
842 /* make sure nobody finds us on the bdi_list anymore */
843 bdi_remove_from_list(bdi);
844 wb_shutdown(&bdi->wb);
845 cgwb_bdi_destroy(bdi);
846
847 if (bdi->dev) {
848 bdi_debug_unregister(bdi);
849 device_unregister(bdi->dev);
850 bdi->dev = NULL;
851 }
852}
853
854void bdi_exit(struct backing_dev_info *bdi)
855{
856 WARN_ON_ONCE(bdi->dev);
857 wb_exit(&bdi->wb);
858}
859
860void bdi_destroy(struct backing_dev_info *bdi)
861{
862 bdi_unregister(bdi);
863 bdi_exit(bdi);
864}
865EXPORT_SYMBOL(bdi_destroy);
866
867/*
868 * For use from filesystems to quickly init and register a bdi associated
869 * with dirty writeback
870 */
871int bdi_setup_and_register(struct backing_dev_info *bdi, char *name)
872{
873 int err;
874
875 bdi->name = name;
876 bdi->capabilities = 0;
877 err = bdi_init(bdi);
878 if (err)
879 return err;
880
881 err = bdi_register(bdi, NULL, "%.28s-%ld", name,
882 atomic_long_inc_return(&bdi_seq));
883 if (err) {
884 bdi_destroy(bdi);
885 return err;
886 }
887
888 return 0;
889}
890EXPORT_SYMBOL(bdi_setup_and_register);
891
892static wait_queue_head_t congestion_wqh[2] = {
893 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
894 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
895 };
896static atomic_t nr_wb_congested[2];
897
898void clear_wb_congested(struct bdi_writeback_congested *congested, int sync)
899{
900 wait_queue_head_t *wqh = &congestion_wqh[sync];
901 enum wb_congested_state bit;
902
903 bit = sync ? WB_sync_congested : WB_async_congested;
904 if (test_and_clear_bit(bit, &congested->state))
905 atomic_dec(&nr_wb_congested[sync]);
906 smp_mb__after_atomic();
907 if (waitqueue_active(wqh))
908 wake_up(wqh);
909}
910EXPORT_SYMBOL(clear_wb_congested);
911
912void set_wb_congested(struct bdi_writeback_congested *congested, int sync)
913{
914 enum wb_congested_state bit;
915
916 bit = sync ? WB_sync_congested : WB_async_congested;
917 if (!test_and_set_bit(bit, &congested->state))
918 atomic_inc(&nr_wb_congested[sync]);
919}
920EXPORT_SYMBOL(set_wb_congested);
921
922/**
923 * congestion_wait - wait for a backing_dev to become uncongested
924 * @sync: SYNC or ASYNC IO
925 * @timeout: timeout in jiffies
926 *
927 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
928 * write congestion. If no backing_devs are congested then just wait for the
929 * next write to be completed.
930 */
931long congestion_wait(int sync, long timeout)
932{
933 long ret;
934 unsigned long start = jiffies;
935 DEFINE_WAIT(wait);
936 wait_queue_head_t *wqh = &congestion_wqh[sync];
937
938 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
939 ret = io_schedule_timeout(timeout);
940 finish_wait(wqh, &wait);
941
942 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
943 jiffies_to_usecs(jiffies - start));
944
945 return ret;
946}
947EXPORT_SYMBOL(congestion_wait);
948
949/**
950 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
951 * @zone: A zone to check if it is heavily congested
952 * @sync: SYNC or ASYNC IO
953 * @timeout: timeout in jiffies
954 *
955 * In the event of a congested backing_dev (any backing_dev) and the given
956 * @zone has experienced recent congestion, this waits for up to @timeout
957 * jiffies for either a BDI to exit congestion of the given @sync queue
958 * or a write to complete.
959 *
960 * In the absence of zone congestion, a short sleep or a cond_resched is
961 * performed to yield the processor and to allow other subsystems to make
962 * a forward progress.
963 *
964 * The return value is 0 if the sleep is for the full timeout. Otherwise,
965 * it is the number of jiffies that were still remaining when the function
966 * returned. return_value == timeout implies the function did not sleep.
967 */
968long wait_iff_congested(struct zone *zone, int sync, long timeout)
969{
970 long ret;
971 unsigned long start = jiffies;
972 DEFINE_WAIT(wait);
973 wait_queue_head_t *wqh = &congestion_wqh[sync];
974
975 /*
976 * If there is no congestion, or heavy congestion is not being
977 * encountered in the current zone, yield if necessary instead
978 * of sleeping on the congestion queue
979 */
980 if (atomic_read(&nr_wb_congested[sync]) == 0 ||
981 !test_bit(ZONE_CONGESTED, &zone->flags)) {
982
983 /*
984 * Memory allocation/reclaim might be called from a WQ
985 * context and the current implementation of the WQ
986 * concurrency control doesn't recognize that a particular
987 * WQ is congested if the worker thread is looping without
988 * ever sleeping. Therefore we have to do a short sleep
989 * here rather than calling cond_resched().
990 */
991 if (current->flags & PF_WQ_WORKER)
992 schedule_timeout_uninterruptible(1);
993 else
994 cond_resched();
995
996 /* In case we scheduled, work out time remaining */
997 ret = timeout - (jiffies - start);
998 if (ret < 0)
999 ret = 0;
1000
1001 goto out;
1002 }
1003
1004 /* Sleep until uncongested or a write happens */
1005 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1006 ret = io_schedule_timeout(timeout);
1007 finish_wait(wqh, &wait);
1008
1009out:
1010 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
1011 jiffies_to_usecs(jiffies - start));
1012
1013 return ret;
1014}
1015EXPORT_SYMBOL(wait_iff_congested);
1016
1017int pdflush_proc_obsolete(struct ctl_table *table, int write,
1018 void __user *buffer, size_t *lenp, loff_t *ppos)
1019{
1020 char kbuf[] = "0\n";
1021
1022 if (*ppos || *lenp < sizeof(kbuf)) {
1023 *lenp = 0;
1024 return 0;
1025 }
1026
1027 if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
1028 return -EFAULT;
1029 pr_warn_once("%s exported in /proc is scheduled for removal\n",
1030 table->procname);
1031
1032 *lenp = 2;
1033 *ppos += *lenp;
1034 return 2;
1035}