mm: memcg: make stats flushing threshold per-memcg
[linux-2.6-microblaze.git] / mm / backing-dev.c
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 static struct dentry *bdi_debug_root;
43
44 static void bdi_debug_init(void)
45 {
46         bdi_debug_root = debugfs_create_dir("bdi", NULL);
47 }
48
49 static 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 }
106 DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
107
108 static 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
116 static void bdi_debug_unregister(struct backing_dev_info *bdi)
117 {
118         debugfs_remove_recursive(bdi->debug_dir);
119 }
120 #else
121 static inline void bdi_debug_init(void)
122 {
123 }
124 static inline void bdi_debug_register(struct backing_dev_info *bdi,
125                                       const char *name)
126 {
127 }
128 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
129 {
130 }
131 #endif
132
133 static 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)                                            \
151 static 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 }                                                                       \
158 static DEVICE_ATTR_RW(name);
159
160 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
161
162 static 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 }
179 BDI_SHOW(min_ratio, bdi->min_ratio / BDI_RATIO_SCALE)
180
181 static ssize_t min_ratio_fine_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_min_ratio_no_scale(bdi, ratio);
193         if (!ret)
194                 ret = count;
195
196         return ret;
197 }
198 BDI_SHOW(min_ratio_fine, bdi->min_ratio)
199
200 static ssize_t max_ratio_store(struct device *dev,
201                 struct device_attribute *attr, const char *buf, size_t count)
202 {
203         struct backing_dev_info *bdi = dev_get_drvdata(dev);
204         unsigned int ratio;
205         ssize_t ret;
206
207         ret = kstrtouint(buf, 10, &ratio);
208         if (ret < 0)
209                 return ret;
210
211         ret = bdi_set_max_ratio(bdi, ratio);
212         if (!ret)
213                 ret = count;
214
215         return ret;
216 }
217 BDI_SHOW(max_ratio, bdi->max_ratio / BDI_RATIO_SCALE)
218
219 static ssize_t max_ratio_fine_store(struct device *dev,
220                 struct device_attribute *attr, const char *buf, size_t count)
221 {
222         struct backing_dev_info *bdi = dev_get_drvdata(dev);
223         unsigned int ratio;
224         ssize_t ret;
225
226         ret = kstrtouint(buf, 10, &ratio);
227         if (ret < 0)
228                 return ret;
229
230         ret = bdi_set_max_ratio_no_scale(bdi, ratio);
231         if (!ret)
232                 ret = count;
233
234         return ret;
235 }
236 BDI_SHOW(max_ratio_fine, bdi->max_ratio)
237
238 static ssize_t min_bytes_show(struct device *dev,
239                               struct device_attribute *attr,
240                               char *buf)
241 {
242         struct backing_dev_info *bdi = dev_get_drvdata(dev);
243
244         return sysfs_emit(buf, "%llu\n", bdi_get_min_bytes(bdi));
245 }
246
247 static ssize_t min_bytes_store(struct device *dev,
248                 struct device_attribute *attr, const char *buf, size_t count)
249 {
250         struct backing_dev_info *bdi = dev_get_drvdata(dev);
251         u64 bytes;
252         ssize_t ret;
253
254         ret = kstrtoull(buf, 10, &bytes);
255         if (ret < 0)
256                 return ret;
257
258         ret = bdi_set_min_bytes(bdi, bytes);
259         if (!ret)
260                 ret = count;
261
262         return ret;
263 }
264 static DEVICE_ATTR_RW(min_bytes);
265
266 static ssize_t max_bytes_show(struct device *dev,
267                               struct device_attribute *attr,
268                               char *buf)
269 {
270         struct backing_dev_info *bdi = dev_get_drvdata(dev);
271
272         return sysfs_emit(buf, "%llu\n", bdi_get_max_bytes(bdi));
273 }
274
275 static ssize_t max_bytes_store(struct device *dev,
276                 struct device_attribute *attr, const char *buf, size_t count)
277 {
278         struct backing_dev_info *bdi = dev_get_drvdata(dev);
279         u64 bytes;
280         ssize_t ret;
281
282         ret = kstrtoull(buf, 10, &bytes);
283         if (ret < 0)
284                 return ret;
285
286         ret = bdi_set_max_bytes(bdi, bytes);
287         if (!ret)
288                 ret = count;
289
290         return ret;
291 }
292 static DEVICE_ATTR_RW(max_bytes);
293
294 static ssize_t stable_pages_required_show(struct device *dev,
295                                           struct device_attribute *attr,
296                                           char *buf)
297 {
298         dev_warn_once(dev,
299                 "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n");
300         return sysfs_emit(buf, "%d\n", 0);
301 }
302 static DEVICE_ATTR_RO(stable_pages_required);
303
304 static ssize_t strict_limit_store(struct device *dev,
305                 struct device_attribute *attr, const char *buf, size_t count)
306 {
307         struct backing_dev_info *bdi = dev_get_drvdata(dev);
308         unsigned int strict_limit;
309         ssize_t ret;
310
311         ret = kstrtouint(buf, 10, &strict_limit);
312         if (ret < 0)
313                 return ret;
314
315         ret = bdi_set_strict_limit(bdi, strict_limit);
316         if (!ret)
317                 ret = count;
318
319         return ret;
320 }
321
322 static ssize_t strict_limit_show(struct device *dev,
323                 struct device_attribute *attr, char *buf)
324 {
325         struct backing_dev_info *bdi = dev_get_drvdata(dev);
326
327         return sysfs_emit(buf, "%d\n",
328                         !!(bdi->capabilities & BDI_CAP_STRICTLIMIT));
329 }
330 static DEVICE_ATTR_RW(strict_limit);
331
332 static struct attribute *bdi_dev_attrs[] = {
333         &dev_attr_read_ahead_kb.attr,
334         &dev_attr_min_ratio.attr,
335         &dev_attr_min_ratio_fine.attr,
336         &dev_attr_max_ratio.attr,
337         &dev_attr_max_ratio_fine.attr,
338         &dev_attr_min_bytes.attr,
339         &dev_attr_max_bytes.attr,
340         &dev_attr_stable_pages_required.attr,
341         &dev_attr_strict_limit.attr,
342         NULL,
343 };
344 ATTRIBUTE_GROUPS(bdi_dev);
345
346 static const struct class bdi_class = {
347         .name           = "bdi",
348         .dev_groups     = bdi_dev_groups,
349 };
350
351 static __init int bdi_class_init(void)
352 {
353         int ret;
354
355         ret = class_register(&bdi_class);
356         if (ret)
357                 return ret;
358
359         bdi_debug_init();
360
361         return 0;
362 }
363 postcore_initcall(bdi_class_init);
364
365 static int __init default_bdi_init(void)
366 {
367         bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
368                                  WQ_SYSFS, 0);
369         if (!bdi_wq)
370                 return -ENOMEM;
371         return 0;
372 }
373 subsys_initcall(default_bdi_init);
374
375 /*
376  * This function is used when the first inode for this wb is marked dirty. It
377  * wakes-up the corresponding bdi thread which should then take care of the
378  * periodic background write-out of dirty inodes. Since the write-out would
379  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
380  * set up a timer which wakes the bdi thread up later.
381  *
382  * Note, we wouldn't bother setting up the timer, but this function is on the
383  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
384  * by delaying the wake-up.
385  *
386  * We have to be careful not to postpone flush work if it is scheduled for
387  * earlier. Thus we use queue_delayed_work().
388  */
389 void wb_wakeup_delayed(struct bdi_writeback *wb)
390 {
391         unsigned long timeout;
392
393         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
394         spin_lock_irq(&wb->work_lock);
395         if (test_bit(WB_registered, &wb->state))
396                 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
397         spin_unlock_irq(&wb->work_lock);
398 }
399
400 static void wb_update_bandwidth_workfn(struct work_struct *work)
401 {
402         struct bdi_writeback *wb = container_of(to_delayed_work(work),
403                                                 struct bdi_writeback, bw_dwork);
404
405         wb_update_bandwidth(wb);
406 }
407
408 /*
409  * Initial write bandwidth: 100 MB/s
410  */
411 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
412
413 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
414                    gfp_t gfp)
415 {
416         int i, err;
417
418         memset(wb, 0, sizeof(*wb));
419
420         wb->bdi = bdi;
421         wb->last_old_flush = jiffies;
422         INIT_LIST_HEAD(&wb->b_dirty);
423         INIT_LIST_HEAD(&wb->b_io);
424         INIT_LIST_HEAD(&wb->b_more_io);
425         INIT_LIST_HEAD(&wb->b_dirty_time);
426         spin_lock_init(&wb->list_lock);
427
428         atomic_set(&wb->writeback_inodes, 0);
429         wb->bw_time_stamp = jiffies;
430         wb->balanced_dirty_ratelimit = INIT_BW;
431         wb->dirty_ratelimit = INIT_BW;
432         wb->write_bandwidth = INIT_BW;
433         wb->avg_write_bandwidth = INIT_BW;
434
435         spin_lock_init(&wb->work_lock);
436         INIT_LIST_HEAD(&wb->work_list);
437         INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
438         INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn);
439         wb->dirty_sleep = jiffies;
440
441         err = fprop_local_init_percpu(&wb->completions, gfp);
442         if (err)
443                 return err;
444
445         for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
446                 err = percpu_counter_init(&wb->stat[i], 0, gfp);
447                 if (err)
448                         goto out_destroy_stat;
449         }
450
451         return 0;
452
453 out_destroy_stat:
454         while (i--)
455                 percpu_counter_destroy(&wb->stat[i]);
456         fprop_local_destroy_percpu(&wb->completions);
457         return err;
458 }
459
460 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
461
462 /*
463  * Remove bdi from the global list and shutdown any threads we have running
464  */
465 static void wb_shutdown(struct bdi_writeback *wb)
466 {
467         /* Make sure nobody queues further work */
468         spin_lock_irq(&wb->work_lock);
469         if (!test_and_clear_bit(WB_registered, &wb->state)) {
470                 spin_unlock_irq(&wb->work_lock);
471                 return;
472         }
473         spin_unlock_irq(&wb->work_lock);
474
475         cgwb_remove_from_bdi_list(wb);
476         /*
477          * Drain work list and shutdown the delayed_work.  !WB_registered
478          * tells wb_workfn() that @wb is dying and its work_list needs to
479          * be drained no matter what.
480          */
481         mod_delayed_work(bdi_wq, &wb->dwork, 0);
482         flush_delayed_work(&wb->dwork);
483         WARN_ON(!list_empty(&wb->work_list));
484         flush_delayed_work(&wb->bw_dwork);
485 }
486
487 static void wb_exit(struct bdi_writeback *wb)
488 {
489         int i;
490
491         WARN_ON(delayed_work_pending(&wb->dwork));
492
493         for (i = 0; i < NR_WB_STAT_ITEMS; i++)
494                 percpu_counter_destroy(&wb->stat[i]);
495
496         fprop_local_destroy_percpu(&wb->completions);
497 }
498
499 #ifdef CONFIG_CGROUP_WRITEBACK
500
501 #include <linux/memcontrol.h>
502
503 /*
504  * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
505  * memcg->cgwb_list.  bdi->cgwb_tree is also RCU protected.
506  */
507 static DEFINE_SPINLOCK(cgwb_lock);
508 static struct workqueue_struct *cgwb_release_wq;
509
510 static LIST_HEAD(offline_cgwbs);
511 static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
512 static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
513
514 static void cgwb_free_rcu(struct rcu_head *rcu_head)
515 {
516         struct bdi_writeback *wb = container_of(rcu_head,
517                         struct bdi_writeback, rcu);
518
519         percpu_ref_exit(&wb->refcnt);
520         kfree(wb);
521 }
522
523 static void cgwb_release_workfn(struct work_struct *work)
524 {
525         struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
526                                                 release_work);
527         struct backing_dev_info *bdi = wb->bdi;
528
529         mutex_lock(&wb->bdi->cgwb_release_mutex);
530         wb_shutdown(wb);
531
532         css_put(wb->memcg_css);
533         css_put(wb->blkcg_css);
534         mutex_unlock(&wb->bdi->cgwb_release_mutex);
535
536         /* triggers blkg destruction if no online users left */
537         blkcg_unpin_online(wb->blkcg_css);
538
539         fprop_local_destroy_percpu(&wb->memcg_completions);
540
541         spin_lock_irq(&cgwb_lock);
542         list_del(&wb->offline_node);
543         spin_unlock_irq(&cgwb_lock);
544
545         wb_exit(wb);
546         bdi_put(bdi);
547         WARN_ON_ONCE(!list_empty(&wb->b_attached));
548         call_rcu(&wb->rcu, cgwb_free_rcu);
549 }
550
551 static void cgwb_release(struct percpu_ref *refcnt)
552 {
553         struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
554                                                 refcnt);
555         queue_work(cgwb_release_wq, &wb->release_work);
556 }
557
558 static void cgwb_kill(struct bdi_writeback *wb)
559 {
560         lockdep_assert_held(&cgwb_lock);
561
562         WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
563         list_del(&wb->memcg_node);
564         list_del(&wb->blkcg_node);
565         list_add(&wb->offline_node, &offline_cgwbs);
566         percpu_ref_kill(&wb->refcnt);
567 }
568
569 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
570 {
571         spin_lock_irq(&cgwb_lock);
572         list_del_rcu(&wb->bdi_node);
573         spin_unlock_irq(&cgwb_lock);
574 }
575
576 static int cgwb_create(struct backing_dev_info *bdi,
577                        struct cgroup_subsys_state *memcg_css, gfp_t gfp)
578 {
579         struct mem_cgroup *memcg;
580         struct cgroup_subsys_state *blkcg_css;
581         struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
582         struct bdi_writeback *wb;
583         unsigned long flags;
584         int ret = 0;
585
586         memcg = mem_cgroup_from_css(memcg_css);
587         blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
588         memcg_cgwb_list = &memcg->cgwb_list;
589         blkcg_cgwb_list = blkcg_get_cgwb_list(blkcg_css);
590
591         /* look up again under lock and discard on blkcg mismatch */
592         spin_lock_irqsave(&cgwb_lock, flags);
593         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
594         if (wb && wb->blkcg_css != blkcg_css) {
595                 cgwb_kill(wb);
596                 wb = NULL;
597         }
598         spin_unlock_irqrestore(&cgwb_lock, flags);
599         if (wb)
600                 goto out_put;
601
602         /* need to create a new one */
603         wb = kmalloc(sizeof(*wb), gfp);
604         if (!wb) {
605                 ret = -ENOMEM;
606                 goto out_put;
607         }
608
609         ret = wb_init(wb, bdi, gfp);
610         if (ret)
611                 goto err_free;
612
613         ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
614         if (ret)
615                 goto err_wb_exit;
616
617         ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
618         if (ret)
619                 goto err_ref_exit;
620
621         wb->memcg_css = memcg_css;
622         wb->blkcg_css = blkcg_css;
623         INIT_LIST_HEAD(&wb->b_attached);
624         INIT_WORK(&wb->release_work, cgwb_release_workfn);
625         set_bit(WB_registered, &wb->state);
626         bdi_get(bdi);
627
628         /*
629          * The root wb determines the registered state of the whole bdi and
630          * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
631          * whether they're still online.  Don't link @wb if any is dead.
632          * See wb_memcg_offline() and wb_blkcg_offline().
633          */
634         ret = -ENODEV;
635         spin_lock_irqsave(&cgwb_lock, flags);
636         if (test_bit(WB_registered, &bdi->wb.state) &&
637             blkcg_cgwb_list->next && memcg_cgwb_list->next) {
638                 /* we might have raced another instance of this function */
639                 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
640                 if (!ret) {
641                         list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
642                         list_add(&wb->memcg_node, memcg_cgwb_list);
643                         list_add(&wb->blkcg_node, blkcg_cgwb_list);
644                         blkcg_pin_online(blkcg_css);
645                         css_get(memcg_css);
646                         css_get(blkcg_css);
647                 }
648         }
649         spin_unlock_irqrestore(&cgwb_lock, flags);
650         if (ret) {
651                 if (ret == -EEXIST)
652                         ret = 0;
653                 goto err_fprop_exit;
654         }
655         goto out_put;
656
657 err_fprop_exit:
658         bdi_put(bdi);
659         fprop_local_destroy_percpu(&wb->memcg_completions);
660 err_ref_exit:
661         percpu_ref_exit(&wb->refcnt);
662 err_wb_exit:
663         wb_exit(wb);
664 err_free:
665         kfree(wb);
666 out_put:
667         css_put(blkcg_css);
668         return ret;
669 }
670
671 /**
672  * wb_get_lookup - get wb for a given memcg
673  * @bdi: target bdi
674  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
675  *
676  * Try to get the wb for @memcg_css on @bdi.  The returned wb has its
677  * refcount incremented.
678  *
679  * This function uses css_get() on @memcg_css and thus expects its refcnt
680  * to be positive on invocation.  IOW, rcu_read_lock() protection on
681  * @memcg_css isn't enough.  try_get it before calling this function.
682  *
683  * A wb is keyed by its associated memcg.  As blkcg implicitly enables
684  * memcg on the default hierarchy, memcg association is guaranteed to be
685  * more specific (equal or descendant to the associated blkcg) and thus can
686  * identify both the memcg and blkcg associations.
687  *
688  * Because the blkcg associated with a memcg may change as blkcg is enabled
689  * and disabled closer to root in the hierarchy, each wb keeps track of
690  * both the memcg and blkcg associated with it and verifies the blkcg on
691  * each lookup.  On mismatch, the existing wb is discarded and a new one is
692  * created.
693  */
694 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
695                                     struct cgroup_subsys_state *memcg_css)
696 {
697         struct bdi_writeback *wb;
698
699         if (!memcg_css->parent)
700                 return &bdi->wb;
701
702         rcu_read_lock();
703         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
704         if (wb) {
705                 struct cgroup_subsys_state *blkcg_css;
706
707                 /* see whether the blkcg association has changed */
708                 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
709                 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
710                         wb = NULL;
711                 css_put(blkcg_css);
712         }
713         rcu_read_unlock();
714
715         return wb;
716 }
717
718 /**
719  * wb_get_create - get wb for a given memcg, create if necessary
720  * @bdi: target bdi
721  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
722  * @gfp: allocation mask to use
723  *
724  * Try to get the wb for @memcg_css on @bdi.  If it doesn't exist, try to
725  * create one.  See wb_get_lookup() for more details.
726  */
727 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
728                                     struct cgroup_subsys_state *memcg_css,
729                                     gfp_t gfp)
730 {
731         struct bdi_writeback *wb;
732
733         might_alloc(gfp);
734
735         do {
736                 wb = wb_get_lookup(bdi, memcg_css);
737         } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
738
739         return wb;
740 }
741
742 static int cgwb_bdi_init(struct backing_dev_info *bdi)
743 {
744         int ret;
745
746         INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
747         mutex_init(&bdi->cgwb_release_mutex);
748         init_rwsem(&bdi->wb_switch_rwsem);
749
750         ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
751         if (!ret) {
752                 bdi->wb.memcg_css = &root_mem_cgroup->css;
753                 bdi->wb.blkcg_css = blkcg_root_css;
754         }
755         return ret;
756 }
757
758 static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
759 {
760         struct radix_tree_iter iter;
761         void **slot;
762         struct bdi_writeback *wb;
763
764         WARN_ON(test_bit(WB_registered, &bdi->wb.state));
765
766         spin_lock_irq(&cgwb_lock);
767         radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
768                 cgwb_kill(*slot);
769         spin_unlock_irq(&cgwb_lock);
770
771         mutex_lock(&bdi->cgwb_release_mutex);
772         spin_lock_irq(&cgwb_lock);
773         while (!list_empty(&bdi->wb_list)) {
774                 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
775                                       bdi_node);
776                 spin_unlock_irq(&cgwb_lock);
777                 wb_shutdown(wb);
778                 spin_lock_irq(&cgwb_lock);
779         }
780         spin_unlock_irq(&cgwb_lock);
781         mutex_unlock(&bdi->cgwb_release_mutex);
782 }
783
784 /*
785  * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
786  *
787  * Try to release dying cgwbs by switching attached inodes to the nearest
788  * living ancestor's writeback. Processed wbs are placed at the end
789  * of the list to guarantee the forward progress.
790  */
791 static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
792 {
793         struct bdi_writeback *wb;
794         LIST_HEAD(processed);
795
796         spin_lock_irq(&cgwb_lock);
797
798         while (!list_empty(&offline_cgwbs)) {
799                 wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
800                                       offline_node);
801                 list_move(&wb->offline_node, &processed);
802
803                 /*
804                  * If wb is dirty, cleaning up the writeback by switching
805                  * attached inodes will result in an effective removal of any
806                  * bandwidth restrictions, which isn't the goal.  Instead,
807                  * it can be postponed until the next time, when all io
808                  * will be likely completed.  If in the meantime some inodes
809                  * will get re-dirtied, they should be eventually switched to
810                  * a new cgwb.
811                  */
812                 if (wb_has_dirty_io(wb))
813                         continue;
814
815                 if (!wb_tryget(wb))
816                         continue;
817
818                 spin_unlock_irq(&cgwb_lock);
819                 while (cleanup_offline_cgwb(wb))
820                         cond_resched();
821                 spin_lock_irq(&cgwb_lock);
822
823                 wb_put(wb);
824         }
825
826         if (!list_empty(&processed))
827                 list_splice_tail(&processed, &offline_cgwbs);
828
829         spin_unlock_irq(&cgwb_lock);
830 }
831
832 /**
833  * wb_memcg_offline - kill all wb's associated with a memcg being offlined
834  * @memcg: memcg being offlined
835  *
836  * Also prevents creation of any new wb's associated with @memcg.
837  */
838 void wb_memcg_offline(struct mem_cgroup *memcg)
839 {
840         struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
841         struct bdi_writeback *wb, *next;
842
843         spin_lock_irq(&cgwb_lock);
844         list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
845                 cgwb_kill(wb);
846         memcg_cgwb_list->next = NULL;   /* prevent new wb's */
847         spin_unlock_irq(&cgwb_lock);
848
849         queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
850 }
851
852 /**
853  * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
854  * @css: blkcg being offlined
855  *
856  * Also prevents creation of any new wb's associated with @blkcg.
857  */
858 void wb_blkcg_offline(struct cgroup_subsys_state *css)
859 {
860         struct bdi_writeback *wb, *next;
861         struct list_head *list = blkcg_get_cgwb_list(css);
862
863         spin_lock_irq(&cgwb_lock);
864         list_for_each_entry_safe(wb, next, list, blkcg_node)
865                 cgwb_kill(wb);
866         list->next = NULL;      /* prevent new wb's */
867         spin_unlock_irq(&cgwb_lock);
868 }
869
870 static void cgwb_bdi_register(struct backing_dev_info *bdi)
871 {
872         spin_lock_irq(&cgwb_lock);
873         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
874         spin_unlock_irq(&cgwb_lock);
875 }
876
877 static int __init cgwb_init(void)
878 {
879         /*
880          * There can be many concurrent release work items overwhelming
881          * system_wq.  Put them in a separate wq and limit concurrency.
882          * There's no point in executing many of these in parallel.
883          */
884         cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
885         if (!cgwb_release_wq)
886                 return -ENOMEM;
887
888         return 0;
889 }
890 subsys_initcall(cgwb_init);
891
892 #else   /* CONFIG_CGROUP_WRITEBACK */
893
894 static int cgwb_bdi_init(struct backing_dev_info *bdi)
895 {
896         return wb_init(&bdi->wb, bdi, GFP_KERNEL);
897 }
898
899 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
900
901 static void cgwb_bdi_register(struct backing_dev_info *bdi)
902 {
903         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
904 }
905
906 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
907 {
908         list_del_rcu(&wb->bdi_node);
909 }
910
911 #endif  /* CONFIG_CGROUP_WRITEBACK */
912
913 int bdi_init(struct backing_dev_info *bdi)
914 {
915         bdi->dev = NULL;
916
917         kref_init(&bdi->refcnt);
918         bdi->min_ratio = 0;
919         bdi->max_ratio = 100 * BDI_RATIO_SCALE;
920         bdi->max_prop_frac = FPROP_FRAC_BASE;
921         INIT_LIST_HEAD(&bdi->bdi_list);
922         INIT_LIST_HEAD(&bdi->wb_list);
923         init_waitqueue_head(&bdi->wb_waitq);
924
925         return cgwb_bdi_init(bdi);
926 }
927
928 struct backing_dev_info *bdi_alloc(int node_id)
929 {
930         struct backing_dev_info *bdi;
931
932         bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
933         if (!bdi)
934                 return NULL;
935
936         if (bdi_init(bdi)) {
937                 kfree(bdi);
938                 return NULL;
939         }
940         bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
941         bdi->ra_pages = VM_READAHEAD_PAGES;
942         bdi->io_pages = VM_READAHEAD_PAGES;
943         timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
944         return bdi;
945 }
946 EXPORT_SYMBOL(bdi_alloc);
947
948 static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
949 {
950         struct rb_node **p = &bdi_tree.rb_node;
951         struct rb_node *parent = NULL;
952         struct backing_dev_info *bdi;
953
954         lockdep_assert_held(&bdi_lock);
955
956         while (*p) {
957                 parent = *p;
958                 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
959
960                 if (bdi->id > id)
961                         p = &(*p)->rb_left;
962                 else if (bdi->id < id)
963                         p = &(*p)->rb_right;
964                 else
965                         break;
966         }
967
968         if (parentp)
969                 *parentp = parent;
970         return p;
971 }
972
973 /**
974  * bdi_get_by_id - lookup and get bdi from its id
975  * @id: bdi id to lookup
976  *
977  * Find bdi matching @id and get it.  Returns NULL if the matching bdi
978  * doesn't exist or is already unregistered.
979  */
980 struct backing_dev_info *bdi_get_by_id(u64 id)
981 {
982         struct backing_dev_info *bdi = NULL;
983         struct rb_node **p;
984
985         spin_lock_bh(&bdi_lock);
986         p = bdi_lookup_rb_node(id, NULL);
987         if (*p) {
988                 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
989                 bdi_get(bdi);
990         }
991         spin_unlock_bh(&bdi_lock);
992
993         return bdi;
994 }
995
996 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
997 {
998         struct device *dev;
999         struct rb_node *parent, **p;
1000
1001         if (bdi->dev)   /* The driver needs to use separate queues per device */
1002                 return 0;
1003
1004         vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
1005         dev = device_create(&bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
1006         if (IS_ERR(dev))
1007                 return PTR_ERR(dev);
1008
1009         cgwb_bdi_register(bdi);
1010         bdi->dev = dev;
1011
1012         bdi_debug_register(bdi, dev_name(dev));
1013         set_bit(WB_registered, &bdi->wb.state);
1014
1015         spin_lock_bh(&bdi_lock);
1016
1017         bdi->id = ++bdi_id_cursor;
1018
1019         p = bdi_lookup_rb_node(bdi->id, &parent);
1020         rb_link_node(&bdi->rb_node, parent, p);
1021         rb_insert_color(&bdi->rb_node, &bdi_tree);
1022
1023         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
1024
1025         spin_unlock_bh(&bdi_lock);
1026
1027         trace_writeback_bdi_register(bdi);
1028         return 0;
1029 }
1030
1031 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
1032 {
1033         va_list args;
1034         int ret;
1035
1036         va_start(args, fmt);
1037         ret = bdi_register_va(bdi, fmt, args);
1038         va_end(args);
1039         return ret;
1040 }
1041 EXPORT_SYMBOL(bdi_register);
1042
1043 void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
1044 {
1045         WARN_ON_ONCE(bdi->owner);
1046         bdi->owner = owner;
1047         get_device(owner);
1048 }
1049
1050 /*
1051  * Remove bdi from bdi_list, and ensure that it is no longer visible
1052  */
1053 static void bdi_remove_from_list(struct backing_dev_info *bdi)
1054 {
1055         spin_lock_bh(&bdi_lock);
1056         rb_erase(&bdi->rb_node, &bdi_tree);
1057         list_del_rcu(&bdi->bdi_list);
1058         spin_unlock_bh(&bdi_lock);
1059
1060         synchronize_rcu_expedited();
1061 }
1062
1063 void bdi_unregister(struct backing_dev_info *bdi)
1064 {
1065         del_timer_sync(&bdi->laptop_mode_wb_timer);
1066
1067         /* make sure nobody finds us on the bdi_list anymore */
1068         bdi_remove_from_list(bdi);
1069         wb_shutdown(&bdi->wb);
1070         cgwb_bdi_unregister(bdi);
1071
1072         /*
1073          * If this BDI's min ratio has been set, use bdi_set_min_ratio() to
1074          * update the global bdi_min_ratio.
1075          */
1076         if (bdi->min_ratio)
1077                 bdi_set_min_ratio(bdi, 0);
1078
1079         if (bdi->dev) {
1080                 bdi_debug_unregister(bdi);
1081                 device_unregister(bdi->dev);
1082                 bdi->dev = NULL;
1083         }
1084
1085         if (bdi->owner) {
1086                 put_device(bdi->owner);
1087                 bdi->owner = NULL;
1088         }
1089 }
1090 EXPORT_SYMBOL(bdi_unregister);
1091
1092 static void release_bdi(struct kref *ref)
1093 {
1094         struct backing_dev_info *bdi =
1095                         container_of(ref, struct backing_dev_info, refcnt);
1096
1097         WARN_ON_ONCE(test_bit(WB_registered, &bdi->wb.state));
1098         WARN_ON_ONCE(bdi->dev);
1099         wb_exit(&bdi->wb);
1100         kfree(bdi);
1101 }
1102
1103 void bdi_put(struct backing_dev_info *bdi)
1104 {
1105         kref_put(&bdi->refcnt, release_bdi);
1106 }
1107 EXPORT_SYMBOL(bdi_put);
1108
1109 struct backing_dev_info *inode_to_bdi(struct inode *inode)
1110 {
1111         struct super_block *sb;
1112
1113         if (!inode)
1114                 return &noop_backing_dev_info;
1115
1116         sb = inode->i_sb;
1117 #ifdef CONFIG_BLOCK
1118         if (sb_is_blkdev_sb(sb))
1119                 return I_BDEV(inode)->bd_disk->bdi;
1120 #endif
1121         return sb->s_bdi;
1122 }
1123 EXPORT_SYMBOL(inode_to_bdi);
1124
1125 const char *bdi_dev_name(struct backing_dev_info *bdi)
1126 {
1127         if (!bdi || !bdi->dev)
1128                 return bdi_unknown_name;
1129         return bdi->dev_name;
1130 }
1131 EXPORT_SYMBOL_GPL(bdi_dev_name);