Merge tag 'v5.15.64' into rpi-5.15.y
[platform/kernel/linux-rpi.git] / mm / backing-dev.c
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
18 struct backing_dev_info noop_backing_dev_info;
19 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
20
21 static struct class *bdi_class;
22 static 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  */
28 DEFINE_SPINLOCK(bdi_lock);
29 static u64 bdi_id_cursor;
30 static struct rb_root bdi_tree = RB_ROOT;
31 LIST_HEAD(bdi_list);
32
33 /* bdi_wq serves all asynchronous writeback tasks */
34 struct 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
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)
180
181 static 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 }
198 BDI_SHOW(max_ratio, bdi->max_ratio)
199
200 static 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 }
208 static DEVICE_ATTR_RO(stable_pages_required);
209
210 static 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 };
217 ATTRIBUTE_GROUPS(bdi_dev);
218
219 static __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 }
230 postcore_initcall(bdi_class_init);
231
232 static int __init default_bdi_init(void)
233 {
234         bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
235                                  WQ_SYSFS, 0);
236         if (!bdi_wq)
237                 return -ENOMEM;
238         return 0;
239 }
240 subsys_initcall(default_bdi_init);
241
242 /*
243  * This function is used when the first inode for this wb is marked dirty. It
244  * wakes-up the corresponding bdi thread which should then take care of the
245  * periodic background write-out of dirty inodes. Since the write-out would
246  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
247  * set up a timer which wakes the bdi thread up later.
248  *
249  * Note, we wouldn't bother setting up the timer, but this function is on the
250  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
251  * by delaying the wake-up.
252  *
253  * We have to be careful not to postpone flush work if it is scheduled for
254  * earlier. Thus we use queue_delayed_work().
255  */
256 void wb_wakeup_delayed(struct bdi_writeback *wb)
257 {
258         unsigned long timeout;
259
260         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
261         spin_lock_irq(&wb->work_lock);
262         if (test_bit(WB_registered, &wb->state))
263                 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
264         spin_unlock_irq(&wb->work_lock);
265 }
266
267 static void wb_update_bandwidth_workfn(struct work_struct *work)
268 {
269         struct bdi_writeback *wb = container_of(to_delayed_work(work),
270                                                 struct bdi_writeback, bw_dwork);
271
272         wb_update_bandwidth(wb);
273 }
274
275 /*
276  * Initial write bandwidth: 100 MB/s
277  */
278 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
279
280 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
281                    gfp_t gfp)
282 {
283         int i, err;
284
285         memset(wb, 0, sizeof(*wb));
286
287         if (wb != &bdi->wb)
288                 bdi_get(bdi);
289         wb->bdi = bdi;
290         wb->last_old_flush = jiffies;
291         INIT_LIST_HEAD(&wb->b_dirty);
292         INIT_LIST_HEAD(&wb->b_io);
293         INIT_LIST_HEAD(&wb->b_more_io);
294         INIT_LIST_HEAD(&wb->b_dirty_time);
295         spin_lock_init(&wb->list_lock);
296
297         atomic_set(&wb->writeback_inodes, 0);
298         wb->bw_time_stamp = jiffies;
299         wb->balanced_dirty_ratelimit = INIT_BW;
300         wb->dirty_ratelimit = INIT_BW;
301         wb->write_bandwidth = INIT_BW;
302         wb->avg_write_bandwidth = INIT_BW;
303
304         spin_lock_init(&wb->work_lock);
305         INIT_LIST_HEAD(&wb->work_list);
306         INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
307         INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn);
308         wb->dirty_sleep = jiffies;
309
310         err = fprop_local_init_percpu(&wb->completions, gfp);
311         if (err)
312                 goto out_put_bdi;
313
314         for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
315                 err = percpu_counter_init(&wb->stat[i], 0, gfp);
316                 if (err)
317                         goto out_destroy_stat;
318         }
319
320         return 0;
321
322 out_destroy_stat:
323         while (i--)
324                 percpu_counter_destroy(&wb->stat[i]);
325         fprop_local_destroy_percpu(&wb->completions);
326 out_put_bdi:
327         if (wb != &bdi->wb)
328                 bdi_put(bdi);
329         return err;
330 }
331
332 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
333
334 /*
335  * Remove bdi from the global list and shutdown any threads we have running
336  */
337 static void wb_shutdown(struct bdi_writeback *wb)
338 {
339         /* Make sure nobody queues further work */
340         spin_lock_irq(&wb->work_lock);
341         if (!test_and_clear_bit(WB_registered, &wb->state)) {
342                 spin_unlock_irq(&wb->work_lock);
343                 return;
344         }
345         spin_unlock_irq(&wb->work_lock);
346
347         cgwb_remove_from_bdi_list(wb);
348         /*
349          * Drain work list and shutdown the delayed_work.  !WB_registered
350          * tells wb_workfn() that @wb is dying and its work_list needs to
351          * be drained no matter what.
352          */
353         mod_delayed_work(bdi_wq, &wb->dwork, 0);
354         flush_delayed_work(&wb->dwork);
355         WARN_ON(!list_empty(&wb->work_list));
356         flush_delayed_work(&wb->bw_dwork);
357 }
358
359 static void wb_exit(struct bdi_writeback *wb)
360 {
361         int i;
362
363         WARN_ON(delayed_work_pending(&wb->dwork));
364
365         for (i = 0; i < NR_WB_STAT_ITEMS; i++)
366                 percpu_counter_destroy(&wb->stat[i]);
367
368         fprop_local_destroy_percpu(&wb->completions);
369         if (wb != &wb->bdi->wb)
370                 bdi_put(wb->bdi);
371 }
372
373 #ifdef CONFIG_CGROUP_WRITEBACK
374
375 #include <linux/memcontrol.h>
376
377 /*
378  * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
379  * memcg->cgwb_list.  bdi->cgwb_tree is also RCU protected.
380  */
381 static DEFINE_SPINLOCK(cgwb_lock);
382 static struct workqueue_struct *cgwb_release_wq;
383
384 static LIST_HEAD(offline_cgwbs);
385 static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
386 static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
387
388 static void cgwb_release_workfn(struct work_struct *work)
389 {
390         struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
391                                                 release_work);
392         struct blkcg *blkcg = css_to_blkcg(wb->blkcg_css);
393
394         mutex_lock(&wb->bdi->cgwb_release_mutex);
395         wb_shutdown(wb);
396
397         css_put(wb->memcg_css);
398         css_put(wb->blkcg_css);
399         mutex_unlock(&wb->bdi->cgwb_release_mutex);
400
401         /* triggers blkg destruction if no online users left */
402         blkcg_unpin_online(blkcg);
403
404         fprop_local_destroy_percpu(&wb->memcg_completions);
405
406         spin_lock_irq(&cgwb_lock);
407         list_del(&wb->offline_node);
408         spin_unlock_irq(&cgwb_lock);
409
410         percpu_ref_exit(&wb->refcnt);
411         wb_exit(wb);
412         WARN_ON_ONCE(!list_empty(&wb->b_attached));
413         kfree_rcu(wb, rcu);
414 }
415
416 static void cgwb_release(struct percpu_ref *refcnt)
417 {
418         struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
419                                                 refcnt);
420         queue_work(cgwb_release_wq, &wb->release_work);
421 }
422
423 static void cgwb_kill(struct bdi_writeback *wb)
424 {
425         lockdep_assert_held(&cgwb_lock);
426
427         WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
428         list_del(&wb->memcg_node);
429         list_del(&wb->blkcg_node);
430         list_add(&wb->offline_node, &offline_cgwbs);
431         percpu_ref_kill(&wb->refcnt);
432 }
433
434 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
435 {
436         spin_lock_irq(&cgwb_lock);
437         list_del_rcu(&wb->bdi_node);
438         spin_unlock_irq(&cgwb_lock);
439 }
440
441 static int cgwb_create(struct backing_dev_info *bdi,
442                        struct cgroup_subsys_state *memcg_css, gfp_t gfp)
443 {
444         struct mem_cgroup *memcg;
445         struct cgroup_subsys_state *blkcg_css;
446         struct blkcg *blkcg;
447         struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
448         struct bdi_writeback *wb;
449         unsigned long flags;
450         int ret = 0;
451
452         memcg = mem_cgroup_from_css(memcg_css);
453         blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
454         blkcg = css_to_blkcg(blkcg_css);
455         memcg_cgwb_list = &memcg->cgwb_list;
456         blkcg_cgwb_list = &blkcg->cgwb_list;
457
458         /* look up again under lock and discard on blkcg mismatch */
459         spin_lock_irqsave(&cgwb_lock, flags);
460         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
461         if (wb && wb->blkcg_css != blkcg_css) {
462                 cgwb_kill(wb);
463                 wb = NULL;
464         }
465         spin_unlock_irqrestore(&cgwb_lock, flags);
466         if (wb)
467                 goto out_put;
468
469         /* need to create a new one */
470         wb = kmalloc(sizeof(*wb), gfp);
471         if (!wb) {
472                 ret = -ENOMEM;
473                 goto out_put;
474         }
475
476         ret = wb_init(wb, bdi, gfp);
477         if (ret)
478                 goto err_free;
479
480         ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
481         if (ret)
482                 goto err_wb_exit;
483
484         ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
485         if (ret)
486                 goto err_ref_exit;
487
488         wb->memcg_css = memcg_css;
489         wb->blkcg_css = blkcg_css;
490         INIT_LIST_HEAD(&wb->b_attached);
491         INIT_WORK(&wb->release_work, cgwb_release_workfn);
492         set_bit(WB_registered, &wb->state);
493
494         /*
495          * The root wb determines the registered state of the whole bdi and
496          * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
497          * whether they're still online.  Don't link @wb if any is dead.
498          * See wb_memcg_offline() and wb_blkcg_offline().
499          */
500         ret = -ENODEV;
501         spin_lock_irqsave(&cgwb_lock, flags);
502         if (test_bit(WB_registered, &bdi->wb.state) &&
503             blkcg_cgwb_list->next && memcg_cgwb_list->next) {
504                 /* we might have raced another instance of this function */
505                 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
506                 if (!ret) {
507                         list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
508                         list_add(&wb->memcg_node, memcg_cgwb_list);
509                         list_add(&wb->blkcg_node, blkcg_cgwb_list);
510                         blkcg_pin_online(blkcg);
511                         css_get(memcg_css);
512                         css_get(blkcg_css);
513                 }
514         }
515         spin_unlock_irqrestore(&cgwb_lock, flags);
516         if (ret) {
517                 if (ret == -EEXIST)
518                         ret = 0;
519                 goto err_fprop_exit;
520         }
521         goto out_put;
522
523 err_fprop_exit:
524         fprop_local_destroy_percpu(&wb->memcg_completions);
525 err_ref_exit:
526         percpu_ref_exit(&wb->refcnt);
527 err_wb_exit:
528         wb_exit(wb);
529 err_free:
530         kfree(wb);
531 out_put:
532         css_put(blkcg_css);
533         return ret;
534 }
535
536 /**
537  * wb_get_lookup - get wb for a given memcg
538  * @bdi: target bdi
539  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
540  *
541  * Try to get the wb for @memcg_css on @bdi.  The returned wb has its
542  * refcount incremented.
543  *
544  * This function uses css_get() on @memcg_css and thus expects its refcnt
545  * to be positive on invocation.  IOW, rcu_read_lock() protection on
546  * @memcg_css isn't enough.  try_get it before calling this function.
547  *
548  * A wb is keyed by its associated memcg.  As blkcg implicitly enables
549  * memcg on the default hierarchy, memcg association is guaranteed to be
550  * more specific (equal or descendant to the associated blkcg) and thus can
551  * identify both the memcg and blkcg associations.
552  *
553  * Because the blkcg associated with a memcg may change as blkcg is enabled
554  * and disabled closer to root in the hierarchy, each wb keeps track of
555  * both the memcg and blkcg associated with it and verifies the blkcg on
556  * each lookup.  On mismatch, the existing wb is discarded and a new one is
557  * created.
558  */
559 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
560                                     struct cgroup_subsys_state *memcg_css)
561 {
562         struct bdi_writeback *wb;
563
564         if (!memcg_css->parent)
565                 return &bdi->wb;
566
567         rcu_read_lock();
568         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
569         if (wb) {
570                 struct cgroup_subsys_state *blkcg_css;
571
572                 /* see whether the blkcg association has changed */
573                 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
574                 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
575                         wb = NULL;
576                 css_put(blkcg_css);
577         }
578         rcu_read_unlock();
579
580         return wb;
581 }
582
583 /**
584  * wb_get_create - get wb for a given memcg, create if necessary
585  * @bdi: target bdi
586  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
587  * @gfp: allocation mask to use
588  *
589  * Try to get the wb for @memcg_css on @bdi.  If it doesn't exist, try to
590  * create one.  See wb_get_lookup() for more details.
591  */
592 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
593                                     struct cgroup_subsys_state *memcg_css,
594                                     gfp_t gfp)
595 {
596         struct bdi_writeback *wb;
597
598         might_alloc(gfp);
599
600         if (!memcg_css->parent)
601                 return &bdi->wb;
602
603         do {
604                 wb = wb_get_lookup(bdi, memcg_css);
605         } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
606
607         return wb;
608 }
609
610 static int cgwb_bdi_init(struct backing_dev_info *bdi)
611 {
612         int ret;
613
614         INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
615         mutex_init(&bdi->cgwb_release_mutex);
616         init_rwsem(&bdi->wb_switch_rwsem);
617
618         ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
619         if (!ret) {
620                 bdi->wb.memcg_css = &root_mem_cgroup->css;
621                 bdi->wb.blkcg_css = blkcg_root_css;
622         }
623         return ret;
624 }
625
626 static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
627 {
628         struct radix_tree_iter iter;
629         void **slot;
630         struct bdi_writeback *wb;
631
632         WARN_ON(test_bit(WB_registered, &bdi->wb.state));
633
634         spin_lock_irq(&cgwb_lock);
635         radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
636                 cgwb_kill(*slot);
637         spin_unlock_irq(&cgwb_lock);
638
639         mutex_lock(&bdi->cgwb_release_mutex);
640         spin_lock_irq(&cgwb_lock);
641         while (!list_empty(&bdi->wb_list)) {
642                 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
643                                       bdi_node);
644                 spin_unlock_irq(&cgwb_lock);
645                 wb_shutdown(wb);
646                 spin_lock_irq(&cgwb_lock);
647         }
648         spin_unlock_irq(&cgwb_lock);
649         mutex_unlock(&bdi->cgwb_release_mutex);
650 }
651
652 /*
653  * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
654  *
655  * Try to release dying cgwbs by switching attached inodes to the nearest
656  * living ancestor's writeback. Processed wbs are placed at the end
657  * of the list to guarantee the forward progress.
658  */
659 static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
660 {
661         struct bdi_writeback *wb;
662         LIST_HEAD(processed);
663
664         spin_lock_irq(&cgwb_lock);
665
666         while (!list_empty(&offline_cgwbs)) {
667                 wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
668                                       offline_node);
669                 list_move(&wb->offline_node, &processed);
670
671                 /*
672                  * If wb is dirty, cleaning up the writeback by switching
673                  * attached inodes will result in an effective removal of any
674                  * bandwidth restrictions, which isn't the goal.  Instead,
675                  * it can be postponed until the next time, when all io
676                  * will be likely completed.  If in the meantime some inodes
677                  * will get re-dirtied, they should be eventually switched to
678                  * a new cgwb.
679                  */
680                 if (wb_has_dirty_io(wb))
681                         continue;
682
683                 if (!wb_tryget(wb))
684                         continue;
685
686                 spin_unlock_irq(&cgwb_lock);
687                 while (cleanup_offline_cgwb(wb))
688                         cond_resched();
689                 spin_lock_irq(&cgwb_lock);
690
691                 wb_put(wb);
692         }
693
694         if (!list_empty(&processed))
695                 list_splice_tail(&processed, &offline_cgwbs);
696
697         spin_unlock_irq(&cgwb_lock);
698 }
699
700 /**
701  * wb_memcg_offline - kill all wb's associated with a memcg being offlined
702  * @memcg: memcg being offlined
703  *
704  * Also prevents creation of any new wb's associated with @memcg.
705  */
706 void wb_memcg_offline(struct mem_cgroup *memcg)
707 {
708         struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
709         struct bdi_writeback *wb, *next;
710
711         spin_lock_irq(&cgwb_lock);
712         list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
713                 cgwb_kill(wb);
714         memcg_cgwb_list->next = NULL;   /* prevent new wb's */
715         spin_unlock_irq(&cgwb_lock);
716
717         queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
718 }
719
720 /**
721  * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
722  * @blkcg: blkcg being offlined
723  *
724  * Also prevents creation of any new wb's associated with @blkcg.
725  */
726 void wb_blkcg_offline(struct blkcg *blkcg)
727 {
728         struct bdi_writeback *wb, *next;
729
730         spin_lock_irq(&cgwb_lock);
731         list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node)
732                 cgwb_kill(wb);
733         blkcg->cgwb_list.next = NULL;   /* prevent new wb's */
734         spin_unlock_irq(&cgwb_lock);
735 }
736
737 static void cgwb_bdi_register(struct backing_dev_info *bdi)
738 {
739         spin_lock_irq(&cgwb_lock);
740         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
741         spin_unlock_irq(&cgwb_lock);
742 }
743
744 static int __init cgwb_init(void)
745 {
746         /*
747          * There can be many concurrent release work items overwhelming
748          * system_wq.  Put them in a separate wq and limit concurrency.
749          * There's no point in executing many of these in parallel.
750          */
751         cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
752         if (!cgwb_release_wq)
753                 return -ENOMEM;
754
755         return 0;
756 }
757 subsys_initcall(cgwb_init);
758
759 #else   /* CONFIG_CGROUP_WRITEBACK */
760
761 static int cgwb_bdi_init(struct backing_dev_info *bdi)
762 {
763         return wb_init(&bdi->wb, bdi, GFP_KERNEL);
764 }
765
766 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
767
768 static void cgwb_bdi_register(struct backing_dev_info *bdi)
769 {
770         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
771 }
772
773 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
774 {
775         list_del_rcu(&wb->bdi_node);
776 }
777
778 #endif  /* CONFIG_CGROUP_WRITEBACK */
779
780 int bdi_init(struct backing_dev_info *bdi)
781 {
782         int ret;
783
784         bdi->dev = NULL;
785
786         kref_init(&bdi->refcnt);
787         bdi->min_ratio = 0;
788         bdi->max_ratio = 100;
789         bdi->max_prop_frac = FPROP_FRAC_BASE;
790         INIT_LIST_HEAD(&bdi->bdi_list);
791         INIT_LIST_HEAD(&bdi->wb_list);
792         init_waitqueue_head(&bdi->wb_waitq);
793
794         ret = cgwb_bdi_init(bdi);
795
796         return ret;
797 }
798
799 struct backing_dev_info *bdi_alloc(int node_id)
800 {
801         struct backing_dev_info *bdi;
802
803         bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
804         if (!bdi)
805                 return NULL;
806
807         if (bdi_init(bdi)) {
808                 kfree(bdi);
809                 return NULL;
810         }
811         bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
812         bdi->ra_pages = VM_READAHEAD_PAGES;
813         bdi->io_pages = VM_READAHEAD_PAGES;
814         timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
815         return bdi;
816 }
817 EXPORT_SYMBOL(bdi_alloc);
818
819 static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
820 {
821         struct rb_node **p = &bdi_tree.rb_node;
822         struct rb_node *parent = NULL;
823         struct backing_dev_info *bdi;
824
825         lockdep_assert_held(&bdi_lock);
826
827         while (*p) {
828                 parent = *p;
829                 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
830
831                 if (bdi->id > id)
832                         p = &(*p)->rb_left;
833                 else if (bdi->id < id)
834                         p = &(*p)->rb_right;
835                 else
836                         break;
837         }
838
839         if (parentp)
840                 *parentp = parent;
841         return p;
842 }
843
844 /**
845  * bdi_get_by_id - lookup and get bdi from its id
846  * @id: bdi id to lookup
847  *
848  * Find bdi matching @id and get it.  Returns NULL if the matching bdi
849  * doesn't exist or is already unregistered.
850  */
851 struct backing_dev_info *bdi_get_by_id(u64 id)
852 {
853         struct backing_dev_info *bdi = NULL;
854         struct rb_node **p;
855
856         spin_lock_bh(&bdi_lock);
857         p = bdi_lookup_rb_node(id, NULL);
858         if (*p) {
859                 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
860                 bdi_get(bdi);
861         }
862         spin_unlock_bh(&bdi_lock);
863
864         return bdi;
865 }
866
867 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
868 {
869         struct device *dev;
870         struct rb_node *parent, **p;
871
872         if (bdi->dev)   /* The driver needs to use separate queues per device */
873                 return 0;
874
875         vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
876         dev = device_create(bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
877         if (IS_ERR(dev))
878                 return PTR_ERR(dev);
879
880         cgwb_bdi_register(bdi);
881         bdi->dev = dev;
882
883         bdi_debug_register(bdi, dev_name(dev));
884         set_bit(WB_registered, &bdi->wb.state);
885
886         spin_lock_bh(&bdi_lock);
887
888         bdi->id = ++bdi_id_cursor;
889
890         p = bdi_lookup_rb_node(bdi->id, &parent);
891         rb_link_node(&bdi->rb_node, parent, p);
892         rb_insert_color(&bdi->rb_node, &bdi_tree);
893
894         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
895
896         spin_unlock_bh(&bdi_lock);
897
898         trace_writeback_bdi_register(bdi);
899         return 0;
900 }
901
902 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
903 {
904         va_list args;
905         int ret;
906
907         va_start(args, fmt);
908         ret = bdi_register_va(bdi, fmt, args);
909         va_end(args);
910         return ret;
911 }
912 EXPORT_SYMBOL(bdi_register);
913
914 void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
915 {
916         WARN_ON_ONCE(bdi->owner);
917         bdi->owner = owner;
918         get_device(owner);
919 }
920
921 /*
922  * Remove bdi from bdi_list, and ensure that it is no longer visible
923  */
924 static void bdi_remove_from_list(struct backing_dev_info *bdi)
925 {
926         spin_lock_bh(&bdi_lock);
927         rb_erase(&bdi->rb_node, &bdi_tree);
928         list_del_rcu(&bdi->bdi_list);
929         spin_unlock_bh(&bdi_lock);
930
931         synchronize_rcu_expedited();
932 }
933
934 void bdi_unregister(struct backing_dev_info *bdi)
935 {
936         del_timer_sync(&bdi->laptop_mode_wb_timer);
937
938         /* make sure nobody finds us on the bdi_list anymore */
939         bdi_remove_from_list(bdi);
940         wb_shutdown(&bdi->wb);
941         cgwb_bdi_unregister(bdi);
942
943         /*
944          * If this BDI's min ratio has been set, use bdi_set_min_ratio() to
945          * update the global bdi_min_ratio.
946          */
947         if (bdi->min_ratio)
948                 bdi_set_min_ratio(bdi, 0);
949
950         if (bdi->dev) {
951                 bdi_debug_unregister(bdi);
952                 device_unregister(bdi->dev);
953                 bdi->dev = NULL;
954         }
955
956         if (bdi->owner) {
957                 put_device(bdi->owner);
958                 bdi->owner = NULL;
959         }
960 }
961
962 static void release_bdi(struct kref *ref)
963 {
964         struct backing_dev_info *bdi =
965                         container_of(ref, struct backing_dev_info, refcnt);
966
967         if (test_bit(WB_registered, &bdi->wb.state))
968                 bdi_unregister(bdi);
969         WARN_ON_ONCE(bdi->dev);
970         wb_exit(&bdi->wb);
971         kfree(bdi);
972 }
973
974 void bdi_put(struct backing_dev_info *bdi)
975 {
976         kref_put(&bdi->refcnt, release_bdi);
977 }
978 EXPORT_SYMBOL(bdi_put);
979
980 const char *bdi_dev_name(struct backing_dev_info *bdi)
981 {
982         if (!bdi || !bdi->dev)
983                 return bdi_unknown_name;
984         return bdi->dev_name;
985 }
986 EXPORT_SYMBOL_GPL(bdi_dev_name);
987
988 static wait_queue_head_t congestion_wqh[2] = {
989                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
990                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
991         };
992 static atomic_t nr_wb_congested[2];
993
994 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
995 {
996         wait_queue_head_t *wqh = &congestion_wqh[sync];
997         enum wb_congested_state bit;
998
999         bit = sync ? WB_sync_congested : WB_async_congested;
1000         if (test_and_clear_bit(bit, &bdi->wb.congested))
1001                 atomic_dec(&nr_wb_congested[sync]);
1002         smp_mb__after_atomic();
1003         if (waitqueue_active(wqh))
1004                 wake_up(wqh);
1005 }
1006 EXPORT_SYMBOL(clear_bdi_congested);
1007
1008 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
1009 {
1010         enum wb_congested_state bit;
1011
1012         bit = sync ? WB_sync_congested : WB_async_congested;
1013         if (!test_and_set_bit(bit, &bdi->wb.congested))
1014                 atomic_inc(&nr_wb_congested[sync]);
1015 }
1016 EXPORT_SYMBOL(set_bdi_congested);
1017
1018 /**
1019  * congestion_wait - wait for a backing_dev to become uncongested
1020  * @sync: SYNC or ASYNC IO
1021  * @timeout: timeout in jiffies
1022  *
1023  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
1024  * write congestion.  If no backing_devs are congested then just wait for the
1025  * next write to be completed.
1026  */
1027 long congestion_wait(int sync, long timeout)
1028 {
1029         long ret;
1030         unsigned long start = jiffies;
1031         DEFINE_WAIT(wait);
1032         wait_queue_head_t *wqh = &congestion_wqh[sync];
1033
1034         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1035         ret = io_schedule_timeout(timeout);
1036         finish_wait(wqh, &wait);
1037
1038         trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
1039                                         jiffies_to_usecs(jiffies - start));
1040
1041         return ret;
1042 }
1043 EXPORT_SYMBOL(congestion_wait);
1044
1045 /**
1046  * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a pgdat to complete writes
1047  * @sync: SYNC or ASYNC IO
1048  * @timeout: timeout in jiffies
1049  *
1050  * In the event of a congested backing_dev (any backing_dev) this waits
1051  * for up to @timeout jiffies for either a BDI to exit congestion of the
1052  * given @sync queue or a write to complete.
1053  *
1054  * The return value is 0 if the sleep is for the full timeout. Otherwise,
1055  * it is the number of jiffies that were still remaining when the function
1056  * returned. return_value == timeout implies the function did not sleep.
1057  */
1058 long wait_iff_congested(int sync, long timeout)
1059 {
1060         long ret;
1061         unsigned long start = jiffies;
1062         DEFINE_WAIT(wait);
1063         wait_queue_head_t *wqh = &congestion_wqh[sync];
1064
1065         /*
1066          * If there is no congestion, yield if necessary instead
1067          * of sleeping on the congestion queue
1068          */
1069         if (atomic_read(&nr_wb_congested[sync]) == 0) {
1070                 cond_resched();
1071
1072                 /* In case we scheduled, work out time remaining */
1073                 ret = timeout - (jiffies - start);
1074                 if (ret < 0)
1075                         ret = 0;
1076
1077                 goto out;
1078         }
1079
1080         /* Sleep until uncongested or a write happens */
1081         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1082         ret = io_schedule_timeout(timeout);
1083         finish_wait(wqh, &wait);
1084
1085 out:
1086         trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
1087                                         jiffies_to_usecs(jiffies - start));
1088
1089         return ret;
1090 }
1091 EXPORT_SYMBOL(wait_iff_congested);