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