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