1 // SPDX-License-Identifier: GPL-2.0-only
2
3 #include <linux/blkdev.h>
4 #include <linux/wait.h>
5 #include <linux/rbtree.h>
6 #include <linux/kthread.h>
7 #include <linux/backing-dev.h>
8 #include <linux/blk-cgroup.h>
9 #include <linux/freezer.h>
10 #include <linux/fs.h>
11 #include <linux/pagemap.h>
12 #include <linux/mm.h>
13 #include <linux/sched/mm.h>
14 #include <linux/sched.h>
15 #include <linux/module.h>
16 #include <linux/writeback.h>
17 #include <linux/device.h>
18 #include <trace/events/writeback.h>
19 #include "internal.h"
20
21 struct backing_dev_info noop_backing_dev_info;
22 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
23
24 static const char *bdi_unknown_name = "(unknown)";
25
26 /*
27 * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
28 * reader side locking.
29 */
30 DEFINE_SPINLOCK(bdi_lock);
31 static u64 bdi_id_cursor;
32 static struct rb_root bdi_tree = RB_ROOT;
33 LIST_HEAD(bdi_list);
34
35 /* bdi_wq serves all asynchronous writeback tasks */
36 struct workqueue_struct *bdi_wq;
37
38 #ifdef CONFIG_DEBUG_FS
39 #include <linux/debugfs.h>
40 #include <linux/seq_file.h>
41
42 struct wb_stats {
43 unsigned long nr_dirty;
44 unsigned long nr_io;
45 unsigned long nr_more_io;
46 unsigned long nr_dirty_time;
47 unsigned long nr_writeback;
48 unsigned long nr_reclaimable;
49 unsigned long nr_dirtied;
50 unsigned long nr_written;
51 unsigned long dirty_thresh;
52 unsigned long wb_thresh;
53 };
54
55 static struct dentry *bdi_debug_root;
56
57 static void bdi_debug_init(void)
58 {
59 bdi_debug_root = debugfs_create_dir("bdi", NULL);
60 }
61
62 static void collect_wb_stats(struct wb_stats *stats,
63 struct bdi_writeback *wb)
64 {
65 struct inode *inode;
66
67 spin_lock(&wb->list_lock);
68 list_for_each_entry(inode, &wb->b_dirty, i_io_list)
69 stats->nr_dirty++;
70 list_for_each_entry(inode, &wb->b_io, i_io_list)
71 stats->nr_io++;
72 list_for_each_entry(inode, &wb->b_more_io, i_io_list)
73 stats->nr_more_io++;
74 list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
75 if (inode->i_state & I_DIRTY_TIME)
76 stats->nr_dirty_time++;
77 spin_unlock(&wb->list_lock);
78
79 stats->nr_writeback += wb_stat(wb, WB_WRITEBACK);
80 stats->nr_reclaimable += wb_stat(wb, WB_RECLAIMABLE);
81 stats->nr_dirtied += wb_stat(wb, WB_DIRTIED);
82 stats->nr_written += wb_stat(wb, WB_WRITTEN);
83 stats->wb_thresh += wb_calc_thresh(wb, stats->dirty_thresh);
84 }
85
86 #ifdef CONFIG_CGROUP_WRITEBACK
87 static void bdi_collect_stats(struct backing_dev_info *bdi,
88 struct wb_stats *stats)
89 {
90 struct bdi_writeback *wb;
91
92 rcu_read_lock();
93 list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node) {
94 if (!wb_tryget(wb))
95 continue;
96
97 collect_wb_stats(stats, wb);
98 wb_put(wb);
99 }
100 rcu_read_unlock();
101 }
102 #else
103 static void bdi_collect_stats(struct backing_dev_info *bdi,
104 struct wb_stats *stats)
105 {
106 collect_wb_stats(stats, &bdi->wb);
107 }
108 #endif
109
110 static int bdi_debug_stats_show(struct seq_file *m, void *v)
111 {
112 struct backing_dev_info *bdi = m->private;
113 unsigned long background_thresh;
114 unsigned long dirty_thresh;
115 struct wb_stats stats;
116 unsigned long tot_bw;
117
118 global_dirty_limits(&background_thresh, &dirty_thresh);
119
120 memset(&stats, 0, sizeof(stats));
121 stats.dirty_thresh = dirty_thresh;
122 bdi_collect_stats(bdi, &stats);
123 tot_bw = atomic_long_read(&bdi->tot_write_bandwidth);
124
125 seq_printf(m,
126 "BdiWriteback: %10lu kB\n"
127 "BdiReclaimable: %10lu kB\n"
128 "BdiDirtyThresh: %10lu kB\n"
129 "DirtyThresh: %10lu kB\n"
130 "BackgroundThresh: %10lu kB\n"
131 "BdiDirtied: %10lu kB\n"
132 "BdiWritten: %10lu kB\n"
133 "BdiWriteBandwidth: %10lu kBps\n"
134 "b_dirty: %10lu\n"
135 "b_io: %10lu\n"
136 "b_more_io: %10lu\n"
137 "b_dirty_time: %10lu\n"
138 "bdi_list: %10u\n"
139 "state: %10lx\n",
140 K(stats.nr_writeback),
141 K(stats.nr_reclaimable),
142 K(stats.wb_thresh),
143 K(dirty_thresh),
144 K(background_thresh),
145 K(stats.nr_dirtied),
146 K(stats.nr_written),
147 K(tot_bw),
148 stats.nr_dirty,
149 stats.nr_io,
150 stats.nr_more_io,
151 stats.nr_dirty_time,
152 !list_empty(&bdi->bdi_list), bdi->wb.state);
153
154 return 0;
155 }
156 DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
157
158 static void wb_stats_show(struct seq_file *m, struct bdi_writeback *wb,
159 struct wb_stats *stats)
160 {
161
162 seq_printf(m,
163 "WbCgIno: %10lu\n"
164 "WbWriteback: %10lu kB\n"
165 "WbReclaimable: %10lu kB\n"
166 "WbDirtyThresh: %10lu kB\n"
167 "WbDirtied: %10lu kB\n"
168 "WbWritten: %10lu kB\n"
169 "WbWriteBandwidth: %10lu kBps\n"
170 "b_dirty: %10lu\n"
171 "b_io: %10lu\n"
172 "b_more_io: %10lu\n"
173 "b_dirty_time: %10lu\n"
174 "state: %10lx\n\n",
175 #ifdef CONFIG_CGROUP_WRITEBACK
176 cgroup_ino(wb->memcg_css->cgroup),
177 #else
178 1ul,
179 #endif
180 K(stats->nr_writeback),
181 K(stats->nr_reclaimable),
182 K(stats->wb_thresh),
183 K(stats->nr_dirtied),
184 K(stats->nr_written),
185 K(wb->avg_write_bandwidth),
186 stats->nr_dirty,
187 stats->nr_io,
188 stats->nr_more_io,
189 stats->nr_dirty_time,
190 wb->state);
191 }
192
193 static int cgwb_debug_stats_show(struct seq_file *m, void *v)
194 {
195 struct backing_dev_info *bdi = m->private;
196 unsigned long background_thresh;
197 unsigned long dirty_thresh;
198 struct bdi_writeback *wb;
199
200 global_dirty_limits(&background_thresh, &dirty_thresh);
201
202 rcu_read_lock();
203 list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node) {
204 struct wb_stats stats = { .dirty_thresh = dirty_thresh };
205
206 if (!wb_tryget(wb))
207 continue;
208
209 collect_wb_stats(&stats, wb);
210
211 /*
212 * Calculate thresh of wb in writeback cgroup which is min of
213 * thresh in global domain and thresh in cgroup domain. Drop
214 * rcu lock because cgwb_calc_thresh may sleep in
215 * cgroup_rstat_flush. We can do so here because we have a ref.
216 */
217 if (mem_cgroup_wb_domain(wb)) {
218 rcu_read_unlock();
219 stats.wb_thresh = min(stats.wb_thresh, cgwb_calc_thresh(wb));
220 rcu_read_lock();
221 }
222
223 wb_stats_show(m, wb, &stats);
224
225 wb_put(wb);
226 }
227 rcu_read_unlock();
228
229 return 0;
230 }
231 DEFINE_SHOW_ATTRIBUTE(cgwb_debug_stats);
232
233 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
234 {
235 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
236
237 debugfs_create_file("stats", 0444, bdi->debug_dir, bdi,
238 &bdi_debug_stats_fops);
239 debugfs_create_file("wb_stats", 0444, bdi->debug_dir, bdi,
240 &cgwb_debug_stats_fops);
241 }
242
243 static void bdi_debug_unregister(struct backing_dev_info *bdi)
244 {
245 debugfs_remove_recursive(bdi->debug_dir);
246 }
247 #else /* CONFIG_DEBUG_FS */
248 static inline void bdi_debug_init(void)
249 {
250 }
251 static inline void bdi_debug_register(struct backing_dev_info *bdi,
252 const char *name)
253 {
254 }
255 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
256 {
257 }
258 #endif /* CONFIG_DEBUG_FS */
259
260 static ssize_t read_ahead_kb_store(struct device *dev,
261 struct device_attribute *attr,
262 const char *buf, size_t count)
263 {
264 struct backing_dev_info *bdi = dev_get_drvdata(dev);
265 unsigned long read_ahead_kb;
266 ssize_t ret;
267
268 ret = kstrtoul(buf, 10, &read_ahead_kb);
269 if (ret < 0)
270 return ret;
271
272 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
273
274 return count;
275 }
276
277 #define BDI_SHOW(name, expr) \
278 static ssize_t name##_show(struct device *dev, \
279 struct device_attribute *attr, char *buf) \
280 { \
281 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
282 \
283 return sysfs_emit(buf, "%lld\n", (long long)expr); \
284 } \
285 static DEVICE_ATTR_RW(name);
286
287 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
288
289 static ssize_t min_ratio_store(struct device *dev,
290 struct device_attribute *attr, const char *buf, size_t count)
291 {
292 struct backing_dev_info *bdi = dev_get_drvdata(dev);
293 unsigned int ratio;
294 ssize_t ret;
295
296 ret = kstrtouint(buf, 10, &ratio);
297 if (ret < 0)
298 return ret;
299
300 ret = bdi_set_min_ratio(bdi, ratio);
301 if (!ret)
302 ret = count;
303
304 return ret;
305 }
306 BDI_SHOW(min_ratio, bdi->min_ratio / BDI_RATIO_SCALE)
307
308 static ssize_t min_ratio_fine_store(struct device *dev,
309 struct device_attribute *attr, const char *buf, size_t count)
310 {
311 struct backing_dev_info *bdi = dev_get_drvdata(dev);
312 unsigned int ratio;
313 ssize_t ret;
314
315 ret = kstrtouint(buf, 10, &ratio);
316 if (ret < 0)
317 return ret;
318
319 ret = bdi_set_min_ratio_no_scale(bdi, ratio);
320 if (!ret)
321 ret = count;
322
323 return ret;
324 }
325 BDI_SHOW(min_ratio_fine, bdi->min_ratio)
326
327 static ssize_t max_ratio_store(struct device *dev,
328 struct device_attribute *attr, const char *buf, size_t count)
329 {
330 struct backing_dev_info *bdi = dev_get_drvdata(dev);
331 unsigned int ratio;
332 ssize_t ret;
333
334 ret = kstrtouint(buf, 10, &ratio);
335 if (ret < 0)
336 return ret;
337
338 ret = bdi_set_max_ratio(bdi, ratio);
339 if (!ret)
340 ret = count;
341
342 return ret;
343 }
344 BDI_SHOW(max_ratio, bdi->max_ratio / BDI_RATIO_SCALE)
345
346 static ssize_t max_ratio_fine_store(struct device *dev,
347 struct device_attribute *attr, const char *buf, size_t count)
348 {
349 struct backing_dev_info *bdi = dev_get_drvdata(dev);
350 unsigned int ratio;
351 ssize_t ret;
352
353 ret = kstrtouint(buf, 10, &ratio);
354 if (ret < 0)
355 return ret;
356
357 ret = bdi_set_max_ratio_no_scale(bdi, ratio);
358 if (!ret)
359 ret = count;
360
361 return ret;
362 }
363 BDI_SHOW(max_ratio_fine, bdi->max_ratio)
364
365 static ssize_t min_bytes_show(struct device *dev,
366 struct device_attribute *attr,
367 char *buf)
368 {
369 struct backing_dev_info *bdi = dev_get_drvdata(dev);
370
371 return sysfs_emit(buf, "%llu\n", bdi_get_min_bytes(bdi));
372 }
373
374 static ssize_t min_bytes_store(struct device *dev,
375 struct device_attribute *attr, const char *buf, size_t count)
376 {
377 struct backing_dev_info *bdi = dev_get_drvdata(dev);
378 u64 bytes;
379 ssize_t ret;
380
381 ret = kstrtoull(buf, 10, &bytes);
382 if (ret < 0)
383 return ret;
384
385 ret = bdi_set_min_bytes(bdi, bytes);
386 if (!ret)
387 ret = count;
388
389 return ret;
390 }
391 static DEVICE_ATTR_RW(min_bytes);
392
393 static ssize_t max_bytes_show(struct device *dev,
394 struct device_attribute *attr,
395 char *buf)
396 {
397 struct backing_dev_info *bdi = dev_get_drvdata(dev);
398
399 return sysfs_emit(buf, "%llu\n", bdi_get_max_bytes(bdi));
400 }
401
402 static ssize_t max_bytes_store(struct device *dev,
403 struct device_attribute *attr, const char *buf, size_t count)
404 {
405 struct backing_dev_info *bdi = dev_get_drvdata(dev);
406 u64 bytes;
407 ssize_t ret;
408
409 ret = kstrtoull(buf, 10, &bytes);
410 if (ret < 0)
411 return ret;
412
413 ret = bdi_set_max_bytes(bdi, bytes);
414 if (!ret)
415 ret = count;
416
417 return ret;
418 }
419 static DEVICE_ATTR_RW(max_bytes);
420
421 static ssize_t stable_pages_required_show(struct device *dev,
422 struct device_attribute *attr,
423 char *buf)
424 {
425 dev_warn_once(dev,
426 "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n");
427 return sysfs_emit(buf, "%d\n", 0);
428 }
429 static DEVICE_ATTR_RO(stable_pages_required);
430
431 static ssize_t strict_limit_store(struct device *dev,
432 struct device_attribute *attr, const char *buf, size_t count)
433 {
434 struct backing_dev_info *bdi = dev_get_drvdata(dev);
435 unsigned int strict_limit;
436 ssize_t ret;
437
438 ret = kstrtouint(buf, 10, &strict_limit);
439 if (ret < 0)
440 return ret;
441
442 ret = bdi_set_strict_limit(bdi, strict_limit);
443 if (!ret)
444 ret = count;
445
446 return ret;
447 }
448
449 static ssize_t strict_limit_show(struct device *dev,
450 struct device_attribute *attr, char *buf)
451 {
452 struct backing_dev_info *bdi = dev_get_drvdata(dev);
453
454 return sysfs_emit(buf, "%d\n",
455 !!(bdi->capabilities & BDI_CAP_STRICTLIMIT));
456 }
457 static DEVICE_ATTR_RW(strict_limit);
458
459 static struct attribute *bdi_dev_attrs[] = {
460 &dev_attr_read_ahead_kb.attr,
461 &dev_attr_min_ratio.attr,
462 &dev_attr_min_ratio_fine.attr,
463 &dev_attr_max_ratio.attr,
464 &dev_attr_max_ratio_fine.attr,
465 &dev_attr_min_bytes.attr,
466 &dev_attr_max_bytes.attr,
467 &dev_attr_stable_pages_required.attr,
468 &dev_attr_strict_limit.attr,
469 NULL,
470 };
471 ATTRIBUTE_GROUPS(bdi_dev);
472
473 static const struct class bdi_class = {
474 .name = "bdi",
475 .dev_groups = bdi_dev_groups,
476 };
477
478 static __init int bdi_class_init(void)
479 {
480 int ret;
481
482 ret = class_register(&bdi_class);
483 if (ret)
484 return ret;
485
486 bdi_debug_init();
487
488 return 0;
489 }
490 postcore_initcall(bdi_class_init);
491
492 static int __init default_bdi_init(void)
493 {
494 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
495 WQ_SYSFS, 0);
496 if (!bdi_wq)
497 return -ENOMEM;
498 return 0;
499 }
500 subsys_initcall(default_bdi_init);
501
502 static void wb_update_bandwidth_workfn(struct work_struct *work)
503 {
504 struct bdi_writeback *wb = container_of(to_delayed_work(work),
505 struct bdi_writeback, bw_dwork);
506
507 wb_update_bandwidth(wb);
508 }
509
510 /*
511 * Initial write bandwidth: 100 MB/s
512 */
513 #define INIT_BW (100 << (20 - PAGE_SHIFT))
514
515 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
516 gfp_t gfp)
517 {
518 int err;
519
520 memset(wb, 0, sizeof(*wb));
521
522 wb->bdi = bdi;
523 wb->last_old_flush = jiffies;
524 INIT_LIST_HEAD(&wb->b_dirty);
525 INIT_LIST_HEAD(&wb->b_io);
526 INIT_LIST_HEAD(&wb->b_more_io);
527 INIT_LIST_HEAD(&wb->b_dirty_time);
528 spin_lock_init(&wb->list_lock);
529
530 atomic_set(&wb->writeback_inodes, 0);
531 wb->bw_time_stamp = jiffies;
532 wb->balanced_dirty_ratelimit = INIT_BW;
533 wb->dirty_ratelimit = INIT_BW;
534 wb->write_bandwidth = INIT_BW;
535 wb->avg_write_bandwidth = INIT_BW;
536
537 spin_lock_init(&wb->work_lock);
538 INIT_LIST_HEAD(&wb->work_list);
539 INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
540 INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn);
541
542 err = fprop_local_init_percpu(&wb->completions, gfp);
543 if (err)
544 return err;
545
546 err = percpu_counter_init_many(wb->stat, 0, gfp, NR_WB_STAT_ITEMS);
547 if (err)
548 fprop_local_destroy_percpu(&wb->completions);
549
550 return err;
551 }
552
553 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
554
555 /*
556 * Remove bdi from the global list and shutdown any threads we have running
557 */
558 static void wb_shutdown(struct bdi_writeback *wb)
559 {
560 /* Make sure nobody queues further work */
561 spin_lock_irq(&wb->work_lock);
562 if (!test_and_clear_bit(WB_registered, &wb->state)) {
563 spin_unlock_irq(&wb->work_lock);
564 return;
565 }
566 spin_unlock_irq(&wb->work_lock);
567
568 cgwb_remove_from_bdi_list(wb);
569 /*
570 * Drain work list and shutdown the delayed_work. !WB_registered
571 * tells wb_workfn() that @wb is dying and its work_list needs to
572 * be drained no matter what.
573 */
574 mod_delayed_work(bdi_wq, &wb->dwork, 0);
575 flush_delayed_work(&wb->dwork);
576 WARN_ON(!list_empty(&wb->work_list));
577 flush_delayed_work(&wb->bw_dwork);
578 }
579
580 static void wb_exit(struct bdi_writeback *wb)
581 {
582 WARN_ON(delayed_work_pending(&wb->dwork));
583 percpu_counter_destroy_many(wb->stat, NR_WB_STAT_ITEMS);
584 fprop_local_destroy_percpu(&wb->completions);
585 }
586
587 #ifdef CONFIG_CGROUP_WRITEBACK
588
589 #include <linux/memcontrol.h>
590
591 /*
592 * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
593 * memcg->cgwb_list. bdi->cgwb_tree is also RCU protected.
594 */
595 static DEFINE_SPINLOCK(cgwb_lock);
596 static struct workqueue_struct *cgwb_release_wq;
597
598 static LIST_HEAD(offline_cgwbs);
599 static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
600 static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
601
602 static void cgwb_free_rcu(struct rcu_head *rcu_head)
603 {
604 struct bdi_writeback *wb = container_of(rcu_head,
605 struct bdi_writeback, rcu);
606
607 percpu_ref_exit(&wb->refcnt);
608 kfree(wb);
609 }
610
611 static void cgwb_release_workfn(struct work_struct *work)
612 {
613 struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
614 release_work);
615 struct backing_dev_info *bdi = wb->bdi;
616
617 mutex_lock(&wb->bdi->cgwb_release_mutex);
618 wb_shutdown(wb);
619
620 css_put(wb->memcg_css);
621 css_put(wb->blkcg_css);
622 mutex_unlock(&wb->bdi->cgwb_release_mutex);
623
624 /* triggers blkg destruction if no online users left */
625 blkcg_unpin_online(wb->blkcg_css);
626
627 fprop_local_destroy_percpu(&wb->memcg_completions);
628
629 spin_lock_irq(&cgwb_lock);
630 list_del(&wb->offline_node);
631 spin_unlock_irq(&cgwb_lock);
632
633 wb_exit(wb);
634 bdi_put(bdi);
635 WARN_ON_ONCE(!list_empty(&wb->b_attached));
636 call_rcu(&wb->rcu, cgwb_free_rcu);
637 }
638
639 static void cgwb_release(struct percpu_ref *refcnt)
640 {
641 struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
642 refcnt);
643 queue_work(cgwb_release_wq, &wb->release_work);
644 }
645
646 static void cgwb_kill(struct bdi_writeback *wb)
647 {
648 lockdep_assert_held(&cgwb_lock);
649
650 WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
651 list_del(&wb->memcg_node);
652 list_del(&wb->blkcg_node);
653 list_add(&wb->offline_node, &offline_cgwbs);
654 percpu_ref_kill(&wb->refcnt);
655 }
656
657 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
658 {
659 spin_lock_irq(&cgwb_lock);
660 list_del_rcu(&wb->bdi_node);
661 spin_unlock_irq(&cgwb_lock);
662 }
663
664 static int cgwb_create(struct backing_dev_info *bdi,
665 struct cgroup_subsys_state *memcg_css, gfp_t gfp)
666 {
667 struct mem_cgroup *memcg;
668 struct cgroup_subsys_state *blkcg_css;
669 struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
670 struct bdi_writeback *wb;
671 unsigned long flags;
672 int ret = 0;
673
674 memcg = mem_cgroup_from_css(memcg_css);
675 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
676 memcg_cgwb_list = &memcg->cgwb_list;
677 blkcg_cgwb_list = blkcg_get_cgwb_list(blkcg_css);
678
679 /* look up again under lock and discard on blkcg mismatch */
680 spin_lock_irqsave(&cgwb_lock, flags);
681 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
682 if (wb && wb->blkcg_css != blkcg_css) {
683 cgwb_kill(wb);
684 wb = NULL;
685 }
686 spin_unlock_irqrestore(&cgwb_lock, flags);
687 if (wb)
688 goto out_put;
689
690 /* need to create a new one */
691 wb = kmalloc(sizeof(*wb), gfp);
692 if (!wb) {
693 ret = -ENOMEM;
694 goto out_put;
695 }
696
697 ret = wb_init(wb, bdi, gfp);
698 if (ret)
699 goto err_free;
700
701 ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
702 if (ret)
703 goto err_wb_exit;
704
705 ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
706 if (ret)
707 goto err_ref_exit;
708
709 wb->memcg_css = memcg_css;
710 wb->blkcg_css = blkcg_css;
711 INIT_LIST_HEAD(&wb->b_attached);
712 INIT_WORK(&wb->release_work, cgwb_release_workfn);
713 set_bit(WB_registered, &wb->state);
714 bdi_get(bdi);
715
716 /*
717 * The root wb determines the registered state of the whole bdi and
718 * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
719 * whether they're still online. Don't link @wb if any is dead.
720 * See wb_memcg_offline() and wb_blkcg_offline().
721 */
722 ret = -ENODEV;
723 spin_lock_irqsave(&cgwb_lock, flags);
724 if (test_bit(WB_registered, &bdi->wb.state) &&
725 blkcg_cgwb_list->next && memcg_cgwb_list->next) {
726 /* we might have raced another instance of this function */
727 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
728 if (!ret) {
729 list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
730 list_add(&wb->memcg_node, memcg_cgwb_list);
731 list_add(&wb->blkcg_node, blkcg_cgwb_list);
732 blkcg_pin_online(blkcg_css);
733 css_get(memcg_css);
734 css_get(blkcg_css);
735 }
736 }
737 spin_unlock_irqrestore(&cgwb_lock, flags);
738 if (ret) {
739 if (ret == -EEXIST)
740 ret = 0;
741 goto err_fprop_exit;
742 }
743 goto out_put;
744
745 err_fprop_exit:
746 bdi_put(bdi);
747 fprop_local_destroy_percpu(&wb->memcg_completions);
748 err_ref_exit:
749 percpu_ref_exit(&wb->refcnt);
750 err_wb_exit:
751 wb_exit(wb);
752 err_free:
753 kfree(wb);
754 out_put:
755 css_put(blkcg_css);
756 return ret;
757 }
758
759 /**
760 * wb_get_lookup - get wb for a given memcg
761 * @bdi: target bdi
762 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
763 *
764 * Try to get the wb for @memcg_css on @bdi. The returned wb has its
765 * refcount incremented.
766 *
767 * This function uses css_get() on @memcg_css and thus expects its refcnt
768 * to be positive on invocation. IOW, rcu_read_lock() protection on
769 * @memcg_css isn't enough. try_get it before calling this function.
770 *
771 * A wb is keyed by its associated memcg. As blkcg implicitly enables
772 * memcg on the default hierarchy, memcg association is guaranteed to be
773 * more specific (equal or descendant to the associated blkcg) and thus can
774 * identify both the memcg and blkcg associations.
775 *
776 * Because the blkcg associated with a memcg may change as blkcg is enabled
777 * and disabled closer to root in the hierarchy, each wb keeps track of
778 * both the memcg and blkcg associated with it and verifies the blkcg on
779 * each lookup. On mismatch, the existing wb is discarded and a new one is
780 * created.
781 */
782 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
783 struct cgroup_subsys_state *memcg_css)
784 {
785 struct bdi_writeback *wb;
786
787 if (!memcg_css->parent)
788 return &bdi->wb;
789
790 rcu_read_lock();
791 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
792 if (wb) {
793 struct cgroup_subsys_state *blkcg_css;
794
795 /* see whether the blkcg association has changed */
796 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
797 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
798 wb = NULL;
799 css_put(blkcg_css);
800 }
801 rcu_read_unlock();
802
803 return wb;
804 }
805
806 /**
807 * wb_get_create - get wb for a given memcg, create if necessary
808 * @bdi: target bdi
809 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
810 * @gfp: allocation mask to use
811 *
812 * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
813 * create one. See wb_get_lookup() for more details.
814 */
815 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
816 struct cgroup_subsys_state *memcg_css,
817 gfp_t gfp)
818 {
819 struct bdi_writeback *wb;
820
821 might_alloc(gfp);
822
823 do {
824 wb = wb_get_lookup(bdi, memcg_css);
825 } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
826
827 return wb;
828 }
829
830 static int cgwb_bdi_init(struct backing_dev_info *bdi)
831 {
832 int ret;
833
834 INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
835 mutex_init(&bdi->cgwb_release_mutex);
836 init_rwsem(&bdi->wb_switch_rwsem);
837
838 ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
839 if (!ret) {
840 bdi->wb.memcg_css = &root_mem_cgroup->css;
841 bdi->wb.blkcg_css = blkcg_root_css;
842 }
843 return ret;
844 }
845
846 static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
847 {
848 struct radix_tree_iter iter;
849 void **slot;
850 struct bdi_writeback *wb;
851
852 WARN_ON(test_bit(WB_registered, &bdi->wb.state));
853
854 spin_lock_irq(&cgwb_lock);
855 radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
856 cgwb_kill(*slot);
857 spin_unlock_irq(&cgwb_lock);
858
859 mutex_lock(&bdi->cgwb_release_mutex);
860 spin_lock_irq(&cgwb_lock);
861 while (!list_empty(&bdi->wb_list)) {
862 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
863 bdi_node);
864 spin_unlock_irq(&cgwb_lock);
865 wb_shutdown(wb);
866 spin_lock_irq(&cgwb_lock);
867 }
868 spin_unlock_irq(&cgwb_lock);
869 mutex_unlock(&bdi->cgwb_release_mutex);
870 }
871
872 /*
873 * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
874 *
875 * Try to release dying cgwbs by switching attached inodes to the nearest
876 * living ancestor's writeback. Processed wbs are placed at the end
877 * of the list to guarantee the forward progress.
878 */
879 static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
880 {
881 struct bdi_writeback *wb;
882 LIST_HEAD(processed);
883
884 spin_lock_irq(&cgwb_lock);
885
886 while (!list_empty(&offline_cgwbs)) {
887 wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
888 offline_node);
889 list_move(&wb->offline_node, &processed);
890
891 /*
892 * If wb is dirty, cleaning up the writeback by switching
893 * attached inodes will result in an effective removal of any
894 * bandwidth restrictions, which isn't the goal. Instead,
895 * it can be postponed until the next time, when all io
896 * will be likely completed. If in the meantime some inodes
897 * will get re-dirtied, they should be eventually switched to
898 * a new cgwb.
899 */
900 if (wb_has_dirty_io(wb))
901 continue;
902
903 if (!wb_tryget(wb))
904 continue;
905
906 spin_unlock_irq(&cgwb_lock);
907 while (cleanup_offline_cgwb(wb))
908 cond_resched();
909 spin_lock_irq(&cgwb_lock);
910
911 wb_put(wb);
912 }
913
914 if (!list_empty(&processed))
915 list_splice_tail(&processed, &offline_cgwbs);
916
917 spin_unlock_irq(&cgwb_lock);
918 }
919
920 /**
921 * wb_memcg_offline - kill all wb's associated with a memcg being offlined
922 * @memcg: memcg being offlined
923 *
924 * Also prevents creation of any new wb's associated with @memcg.
925 */
926 void wb_memcg_offline(struct mem_cgroup *memcg)
927 {
928 struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
929 struct bdi_writeback *wb, *next;
930
931 spin_lock_irq(&cgwb_lock);
932 list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
933 cgwb_kill(wb);
934 memcg_cgwb_list->next = NULL; /* prevent new wb's */
935 spin_unlock_irq(&cgwb_lock);
936
937 queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
938 }
939
940 /**
941 * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
942 * @css: blkcg being offlined
943 *
944 * Also prevents creation of any new wb's associated with @blkcg.
945 */
946 void wb_blkcg_offline(struct cgroup_subsys_state *css)
947 {
948 struct bdi_writeback *wb, *next;
949 struct list_head *list = blkcg_get_cgwb_list(css);
950
951 spin_lock_irq(&cgwb_lock);
952 list_for_each_entry_safe(wb, next, list, blkcg_node)
953 cgwb_kill(wb);
954 list->next = NULL; /* prevent new wb's */
955 spin_unlock_irq(&cgwb_lock);
956 }
957
958 static void cgwb_bdi_register(struct backing_dev_info *bdi)
959 {
960 spin_lock_irq(&cgwb_lock);
961 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
962 spin_unlock_irq(&cgwb_lock);
963 }
964
965 static int __init cgwb_init(void)
966 {
967 /*
968 * There can be many concurrent release work items overwhelming
969 * system_wq. Put them in a separate wq and limit concurrency.
970 * There's no point in executing many of these in parallel.
971 */
972 cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
973 if (!cgwb_release_wq)
974 return -ENOMEM;
975
976 return 0;
977 }
978 subsys_initcall(cgwb_init);
979
980 #else /* CONFIG_CGROUP_WRITEBACK */
981
982 static int cgwb_bdi_init(struct backing_dev_info *bdi)
983 {
984 return wb_init(&bdi->wb, bdi, GFP_KERNEL);
985 }
986
987 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
988
989 static void cgwb_bdi_register(struct backing_dev_info *bdi)
990 {
991 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
992 }
993
994 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
995 {
996 list_del_rcu(&wb->bdi_node);
997 }
998
999 #endif /* CONFIG_CGROUP_WRITEBACK */
1000
1001 int bdi_init(struct backing_dev_info *bdi)
1002 {
1003 bdi->dev = NULL;
1004
1005 kref_init(&bdi->refcnt);
1006 bdi->min_ratio = 0;
1007 bdi->max_ratio = 100 * BDI_RATIO_SCALE;
1008 bdi->max_prop_frac = FPROP_FRAC_BASE;
1009 INIT_LIST_HEAD(&bdi->bdi_list);
1010 INIT_LIST_HEAD(&bdi->wb_list);
1011 init_waitqueue_head(&bdi->wb_waitq);
1012 bdi->last_bdp_sleep = jiffies;
1013
1014 return cgwb_bdi_init(bdi);
1015 }
1016
1017 struct backing_dev_info *bdi_alloc(int node_id)
1018 {
1019 struct backing_dev_info *bdi;
1020
1021 bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
1022 if (!bdi)
1023 return NULL;
1024
1025 if (bdi_init(bdi)) {
1026 kfree(bdi);
1027 return NULL;
1028 }
1029 bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
1030 bdi->ra_pages = VM_READAHEAD_PAGES;
1031 bdi->io_pages = VM_READAHEAD_PAGES;
1032 timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
1033 return bdi;
1034 }
1035 EXPORT_SYMBOL(bdi_alloc);
1036
1037 static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
1038 {
1039 struct rb_node **p = &bdi_tree.rb_node;
1040 struct rb_node *parent = NULL;
1041 struct backing_dev_info *bdi;
1042
1043 lockdep_assert_held(&bdi_lock);
1044
1045 while (*p) {
1046 parent = *p;
1047 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
1048
1049 if (bdi->id > id)
1050 p = &(*p)->rb_left;
1051 else if (bdi->id < id)
1052 p = &(*p)->rb_right;
1053 else
1054 break;
1055 }
1056
1057 if (parentp)
1058 *parentp = parent;
1059 return p;
1060 }
1061
1062 /**
1063 * bdi_get_by_id - lookup and get bdi from its id
1064 * @id: bdi id to lookup
1065 *
1066 * Find bdi matching @id and get it. Returns NULL if the matching bdi
1067 * doesn't exist or is already unregistered.
1068 */
1069 struct backing_dev_info *bdi_get_by_id(u64 id)
1070 {
1071 struct backing_dev_info *bdi = NULL;
1072 struct rb_node **p;
1073
1074 spin_lock_bh(&bdi_lock);
1075 p = bdi_lookup_rb_node(id, NULL);
1076 if (*p) {
1077 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
1078 bdi_get(bdi);
1079 }
1080 spin_unlock_bh(&bdi_lock);
1081
1082 return bdi;
1083 }
1084
1085 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
1086 {
1087 struct device *dev;
1088 struct rb_node *parent, **p;
1089
1090 if (bdi->dev) /* The driver needs to use separate queues per device */
1091 return 0;
1092
1093 vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
1094 dev = device_create(&bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
1095 if (IS_ERR(dev))
1096 return PTR_ERR(dev);
1097
1098 cgwb_bdi_register(bdi);
1099 bdi->dev = dev;
1100
1101 bdi_debug_register(bdi, dev_name(dev));
1102 set_bit(WB_registered, &bdi->wb.state);
1103
1104 spin_lock_bh(&bdi_lock);
1105
1106 bdi->id = ++bdi_id_cursor;
1107
1108 p = bdi_lookup_rb_node(bdi->id, &parent);
1109 rb_link_node(&bdi->rb_node, parent, p);
1110 rb_insert_color(&bdi->rb_node, &bdi_tree);
1111
1112 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
1113
1114 spin_unlock_bh(&bdi_lock);
1115
1116 trace_writeback_bdi_register(bdi);
1117 return 0;
1118 }
1119
1120 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
1121 {
1122 va_list args;
1123 int ret;
1124
1125 va_start(args, fmt);
1126 ret = bdi_register_va(bdi, fmt, args);
1127 va_end(args);
1128 return ret;
1129 }
1130 EXPORT_SYMBOL(bdi_register);
1131
1132 void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
1133 {
1134 WARN_ON_ONCE(bdi->owner);
1135 bdi->owner = owner;
1136 get_device(owner);
1137 }
1138
1139 /*
1140 * Remove bdi from bdi_list, and ensure that it is no longer visible
1141 */
1142 static void bdi_remove_from_list(struct backing_dev_info *bdi)
1143 {
1144 spin_lock_bh(&bdi_lock);
1145 rb_erase(&bdi->rb_node, &bdi_tree);
1146 list_del_rcu(&bdi->bdi_list);
1147 spin_unlock_bh(&bdi_lock);
1148
1149 synchronize_rcu_expedited();
1150 }
1151
1152 void bdi_unregister(struct backing_dev_info *bdi)
1153 {
1154 del_timer_sync(&bdi->laptop_mode_wb_timer);
1155
1156 /* make sure nobody finds us on the bdi_list anymore */
1157 bdi_remove_from_list(bdi);
1158 wb_shutdown(&bdi->wb);
1159 cgwb_bdi_unregister(bdi);
1160
1161 /*
1162 * If this BDI's min ratio has been set, use bdi_set_min_ratio() to
1163 * update the global bdi_min_ratio.
1164 */
1165 if (bdi->min_ratio)
1166 bdi_set_min_ratio(bdi, 0);
1167
1168 if (bdi->dev) {
1169 bdi_debug_unregister(bdi);
1170 device_unregister(bdi->dev);
1171 bdi->dev = NULL;
1172 }
1173
1174 if (bdi->owner) {
1175 put_device(bdi->owner);
1176 bdi->owner = NULL;
1177 }
1178 }
1179 EXPORT_SYMBOL(bdi_unregister);
1180
1181 static void release_bdi(struct kref *ref)
1182 {
1183 struct backing_dev_info *bdi =
1184 container_of(ref, struct backing_dev_info, refcnt);
1185
1186 WARN_ON_ONCE(test_bit(WB_registered, &bdi->wb.state));
1187 WARN_ON_ONCE(bdi->dev);
1188 wb_exit(&bdi->wb);
1189 kfree(bdi);
1190 }
1191
1192 void bdi_put(struct backing_dev_info *bdi)
1193 {
1194 kref_put(&bdi->refcnt, release_bdi);
1195 }
1196 EXPORT_SYMBOL(bdi_put);
1197
1198 struct backing_dev_info *inode_to_bdi(struct inode *inode)
1199 {
1200 struct super_block *sb;
1201
1202 if (!inode)
1203 return &noop_backing_dev_info;
1204
1205 sb = inode->i_sb;
1206 #ifdef CONFIG_BLOCK
1207 if (sb_is_blkdev_sb(sb))
1208 return I_BDEV(inode)->bd_disk->bdi;
1209 #endif
1210 return sb->s_bdi;
1211 }
1212 EXPORT_SYMBOL(inode_to_bdi);
1213
1214 const char *bdi_dev_name(struct backing_dev_info *bdi)
1215 {
1216 if (!bdi || !bdi->dev)
1217 return bdi_unknown_name;
1218 return bdi->dev_name;
1219 }
1220 EXPORT_SYMBOL_GPL(bdi_dev_name);
1221
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