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