Merge tag 'timers-core-2022-08-01' of git://git.kernel.org/pub/scm/linux/kernel/git...
[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
20 struct backing_dev_info noop_backing_dev_info;
21 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
22
23 static struct class *bdi_class;
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 #define K(x) ((x) << (PAGE_SHIFT - 10))
39
40 #ifdef CONFIG_DEBUG_FS
41 #include <linux/debugfs.h>
42 #include <linux/seq_file.h>
43
44 static struct dentry *bdi_debug_root;
45
46 static void bdi_debug_init(void)
47 {
48         bdi_debug_root = debugfs_create_dir("bdi", NULL);
49 }
50
51 static int bdi_debug_stats_show(struct seq_file *m, void *v)
52 {
53         struct backing_dev_info *bdi = m->private;
54         struct bdi_writeback *wb = &bdi->wb;
55         unsigned long background_thresh;
56         unsigned long dirty_thresh;
57         unsigned long wb_thresh;
58         unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
59         struct inode *inode;
60
61         nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
62         spin_lock(&wb->list_lock);
63         list_for_each_entry(inode, &wb->b_dirty, i_io_list)
64                 nr_dirty++;
65         list_for_each_entry(inode, &wb->b_io, i_io_list)
66                 nr_io++;
67         list_for_each_entry(inode, &wb->b_more_io, i_io_list)
68                 nr_more_io++;
69         list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
70                 if (inode->i_state & I_DIRTY_TIME)
71                         nr_dirty_time++;
72         spin_unlock(&wb->list_lock);
73
74         global_dirty_limits(&background_thresh, &dirty_thresh);
75         wb_thresh = wb_calc_thresh(wb, dirty_thresh);
76
77         seq_printf(m,
78                    "BdiWriteback:       %10lu kB\n"
79                    "BdiReclaimable:     %10lu kB\n"
80                    "BdiDirtyThresh:     %10lu kB\n"
81                    "DirtyThresh:        %10lu kB\n"
82                    "BackgroundThresh:   %10lu kB\n"
83                    "BdiDirtied:         %10lu kB\n"
84                    "BdiWritten:         %10lu kB\n"
85                    "BdiWriteBandwidth:  %10lu kBps\n"
86                    "b_dirty:            %10lu\n"
87                    "b_io:               %10lu\n"
88                    "b_more_io:          %10lu\n"
89                    "b_dirty_time:       %10lu\n"
90                    "bdi_list:           %10u\n"
91                    "state:              %10lx\n",
92                    (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
93                    (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
94                    K(wb_thresh),
95                    K(dirty_thresh),
96                    K(background_thresh),
97                    (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
98                    (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
99                    (unsigned long) K(wb->write_bandwidth),
100                    nr_dirty,
101                    nr_io,
102                    nr_more_io,
103                    nr_dirty_time,
104                    !list_empty(&bdi->bdi_list), bdi->wb.state);
105
106         return 0;
107 }
108 DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
109
110 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
111 {
112         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
113
114         debugfs_create_file("stats", 0444, bdi->debug_dir, bdi,
115                             &bdi_debug_stats_fops);
116 }
117
118 static void bdi_debug_unregister(struct backing_dev_info *bdi)
119 {
120         debugfs_remove_recursive(bdi->debug_dir);
121 }
122 #else
123 static inline void bdi_debug_init(void)
124 {
125 }
126 static inline void bdi_debug_register(struct backing_dev_info *bdi,
127                                       const char *name)
128 {
129 }
130 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
131 {
132 }
133 #endif
134
135 static ssize_t read_ahead_kb_store(struct device *dev,
136                                   struct device_attribute *attr,
137                                   const char *buf, size_t count)
138 {
139         struct backing_dev_info *bdi = dev_get_drvdata(dev);
140         unsigned long read_ahead_kb;
141         ssize_t ret;
142
143         ret = kstrtoul(buf, 10, &read_ahead_kb);
144         if (ret < 0)
145                 return ret;
146
147         bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
148
149         return count;
150 }
151
152 #define BDI_SHOW(name, expr)                                            \
153 static ssize_t name##_show(struct device *dev,                          \
154                            struct device_attribute *attr, char *buf)    \
155 {                                                                       \
156         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
157                                                                         \
158         return sysfs_emit(buf, "%lld\n", (long long)expr);              \
159 }                                                                       \
160 static DEVICE_ATTR_RW(name);
161
162 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
163
164 static ssize_t min_ratio_store(struct device *dev,
165                 struct device_attribute *attr, const char *buf, size_t count)
166 {
167         struct backing_dev_info *bdi = dev_get_drvdata(dev);
168         unsigned int ratio;
169         ssize_t ret;
170
171         ret = kstrtouint(buf, 10, &ratio);
172         if (ret < 0)
173                 return ret;
174
175         ret = bdi_set_min_ratio(bdi, ratio);
176         if (!ret)
177                 ret = count;
178
179         return ret;
180 }
181 BDI_SHOW(min_ratio, bdi->min_ratio)
182
183 static ssize_t max_ratio_store(struct device *dev,
184                 struct device_attribute *attr, const char *buf, size_t count)
185 {
186         struct backing_dev_info *bdi = dev_get_drvdata(dev);
187         unsigned int ratio;
188         ssize_t ret;
189
190         ret = kstrtouint(buf, 10, &ratio);
191         if (ret < 0)
192                 return ret;
193
194         ret = bdi_set_max_ratio(bdi, ratio);
195         if (!ret)
196                 ret = count;
197
198         return ret;
199 }
200 BDI_SHOW(max_ratio, bdi->max_ratio)
201
202 static ssize_t stable_pages_required_show(struct device *dev,
203                                           struct device_attribute *attr,
204                                           char *buf)
205 {
206         dev_warn_once(dev,
207                 "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n");
208         return sysfs_emit(buf, "%d\n", 0);
209 }
210 static DEVICE_ATTR_RO(stable_pages_required);
211
212 static struct attribute *bdi_dev_attrs[] = {
213         &dev_attr_read_ahead_kb.attr,
214         &dev_attr_min_ratio.attr,
215         &dev_attr_max_ratio.attr,
216         &dev_attr_stable_pages_required.attr,
217         NULL,
218 };
219 ATTRIBUTE_GROUPS(bdi_dev);
220
221 static __init int bdi_class_init(void)
222 {
223         bdi_class = class_create(THIS_MODULE, "bdi");
224         if (IS_ERR(bdi_class))
225                 return PTR_ERR(bdi_class);
226
227         bdi_class->dev_groups = bdi_dev_groups;
228         bdi_debug_init();
229
230         return 0;
231 }
232 postcore_initcall(bdi_class_init);
233
234 static int __init default_bdi_init(void)
235 {
236         bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
237                                  WQ_SYSFS, 0);
238         if (!bdi_wq)
239                 return -ENOMEM;
240         return 0;
241 }
242 subsys_initcall(default_bdi_init);
243
244 /*
245  * This function is used when the first inode for this wb is marked dirty. It
246  * wakes-up the corresponding bdi thread which should then take care of the
247  * periodic background write-out of dirty inodes. Since the write-out would
248  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
249  * set up a timer which wakes the bdi thread up later.
250  *
251  * Note, we wouldn't bother setting up the timer, but this function is on the
252  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
253  * by delaying the wake-up.
254  *
255  * We have to be careful not to postpone flush work if it is scheduled for
256  * earlier. Thus we use queue_delayed_work().
257  */
258 void wb_wakeup_delayed(struct bdi_writeback *wb)
259 {
260         unsigned long timeout;
261
262         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
263         spin_lock_bh(&wb->work_lock);
264         if (test_bit(WB_registered, &wb->state))
265                 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
266         spin_unlock_bh(&wb->work_lock);
267 }
268
269 static void wb_update_bandwidth_workfn(struct work_struct *work)
270 {
271         struct bdi_writeback *wb = container_of(to_delayed_work(work),
272                                                 struct bdi_writeback, bw_dwork);
273
274         wb_update_bandwidth(wb);
275 }
276
277 /*
278  * Initial write bandwidth: 100 MB/s
279  */
280 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
281
282 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
283                    gfp_t gfp)
284 {
285         int i, err;
286
287         memset(wb, 0, sizeof(*wb));
288
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                 return err;
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         return err;
327 }
328
329 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
330
331 /*
332  * Remove bdi from the global list and shutdown any threads we have running
333  */
334 static void wb_shutdown(struct bdi_writeback *wb)
335 {
336         /* Make sure nobody queues further work */
337         spin_lock_bh(&wb->work_lock);
338         if (!test_and_clear_bit(WB_registered, &wb->state)) {
339                 spin_unlock_bh(&wb->work_lock);
340                 return;
341         }
342         spin_unlock_bh(&wb->work_lock);
343
344         cgwb_remove_from_bdi_list(wb);
345         /*
346          * Drain work list and shutdown the delayed_work.  !WB_registered
347          * tells wb_workfn() that @wb is dying and its work_list needs to
348          * be drained no matter what.
349          */
350         mod_delayed_work(bdi_wq, &wb->dwork, 0);
351         flush_delayed_work(&wb->dwork);
352         WARN_ON(!list_empty(&wb->work_list));
353         flush_delayed_work(&wb->bw_dwork);
354 }
355
356 static void wb_exit(struct bdi_writeback *wb)
357 {
358         int i;
359
360         WARN_ON(delayed_work_pending(&wb->dwork));
361
362         for (i = 0; i < NR_WB_STAT_ITEMS; i++)
363                 percpu_counter_destroy(&wb->stat[i]);
364
365         fprop_local_destroy_percpu(&wb->completions);
366 }
367
368 #ifdef CONFIG_CGROUP_WRITEBACK
369
370 #include <linux/memcontrol.h>
371
372 /*
373  * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
374  * memcg->cgwb_list.  bdi->cgwb_tree is also RCU protected.
375  */
376 static DEFINE_SPINLOCK(cgwb_lock);
377 static struct workqueue_struct *cgwb_release_wq;
378
379 static LIST_HEAD(offline_cgwbs);
380 static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
381 static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
382
383 static void cgwb_release_workfn(struct work_struct *work)
384 {
385         struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
386                                                 release_work);
387         struct backing_dev_info *bdi = wb->bdi;
388
389         mutex_lock(&wb->bdi->cgwb_release_mutex);
390         wb_shutdown(wb);
391
392         css_put(wb->memcg_css);
393         css_put(wb->blkcg_css);
394         mutex_unlock(&wb->bdi->cgwb_release_mutex);
395
396         /* triggers blkg destruction if no online users left */
397         blkcg_unpin_online(wb->blkcg_css);
398
399         fprop_local_destroy_percpu(&wb->memcg_completions);
400
401         spin_lock_irq(&cgwb_lock);
402         list_del(&wb->offline_node);
403         spin_unlock_irq(&cgwb_lock);
404
405         percpu_ref_exit(&wb->refcnt);
406         wb_exit(wb);
407         bdi_put(bdi);
408         WARN_ON_ONCE(!list_empty(&wb->b_attached));
409         kfree_rcu(wb, rcu);
410 }
411
412 static void cgwb_release(struct percpu_ref *refcnt)
413 {
414         struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
415                                                 refcnt);
416         queue_work(cgwb_release_wq, &wb->release_work);
417 }
418
419 static void cgwb_kill(struct bdi_writeback *wb)
420 {
421         lockdep_assert_held(&cgwb_lock);
422
423         WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
424         list_del(&wb->memcg_node);
425         list_del(&wb->blkcg_node);
426         list_add(&wb->offline_node, &offline_cgwbs);
427         percpu_ref_kill(&wb->refcnt);
428 }
429
430 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
431 {
432         spin_lock_irq(&cgwb_lock);
433         list_del_rcu(&wb->bdi_node);
434         spin_unlock_irq(&cgwb_lock);
435 }
436
437 static int cgwb_create(struct backing_dev_info *bdi,
438                        struct cgroup_subsys_state *memcg_css, gfp_t gfp)
439 {
440         struct mem_cgroup *memcg;
441         struct cgroup_subsys_state *blkcg_css;
442         struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
443         struct bdi_writeback *wb;
444         unsigned long flags;
445         int ret = 0;
446
447         memcg = mem_cgroup_from_css(memcg_css);
448         blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
449         memcg_cgwb_list = &memcg->cgwb_list;
450         blkcg_cgwb_list = blkcg_get_cgwb_list(blkcg_css);
451
452         /* look up again under lock and discard on blkcg mismatch */
453         spin_lock_irqsave(&cgwb_lock, flags);
454         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
455         if (wb && wb->blkcg_css != blkcg_css) {
456                 cgwb_kill(wb);
457                 wb = NULL;
458         }
459         spin_unlock_irqrestore(&cgwb_lock, flags);
460         if (wb)
461                 goto out_put;
462
463         /* need to create a new one */
464         wb = kmalloc(sizeof(*wb), gfp);
465         if (!wb) {
466                 ret = -ENOMEM;
467                 goto out_put;
468         }
469
470         ret = wb_init(wb, bdi, gfp);
471         if (ret)
472                 goto err_free;
473
474         ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
475         if (ret)
476                 goto err_wb_exit;
477
478         ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
479         if (ret)
480                 goto err_ref_exit;
481
482         wb->memcg_css = memcg_css;
483         wb->blkcg_css = blkcg_css;
484         INIT_LIST_HEAD(&wb->b_attached);
485         INIT_WORK(&wb->release_work, cgwb_release_workfn);
486         set_bit(WB_registered, &wb->state);
487         bdi_get(bdi);
488
489         /*
490          * The root wb determines the registered state of the whole bdi and
491          * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
492          * whether they're still online.  Don't link @wb if any is dead.
493          * See wb_memcg_offline() and wb_blkcg_offline().
494          */
495         ret = -ENODEV;
496         spin_lock_irqsave(&cgwb_lock, flags);
497         if (test_bit(WB_registered, &bdi->wb.state) &&
498             blkcg_cgwb_list->next && memcg_cgwb_list->next) {
499                 /* we might have raced another instance of this function */
500                 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
501                 if (!ret) {
502                         list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
503                         list_add(&wb->memcg_node, memcg_cgwb_list);
504                         list_add(&wb->blkcg_node, blkcg_cgwb_list);
505                         blkcg_pin_online(blkcg_css);
506                         css_get(memcg_css);
507                         css_get(blkcg_css);
508                 }
509         }
510         spin_unlock_irqrestore(&cgwb_lock, flags);
511         if (ret) {
512                 if (ret == -EEXIST)
513                         ret = 0;
514                 goto err_fprop_exit;
515         }
516         goto out_put;
517
518 err_fprop_exit:
519         bdi_put(bdi);
520         fprop_local_destroy_percpu(&wb->memcg_completions);
521 err_ref_exit:
522         percpu_ref_exit(&wb->refcnt);
523 err_wb_exit:
524         wb_exit(wb);
525 err_free:
526         kfree(wb);
527 out_put:
528         css_put(blkcg_css);
529         return ret;
530 }
531
532 /**
533  * wb_get_lookup - get wb for a given memcg
534  * @bdi: target bdi
535  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
536  *
537  * Try to get the wb for @memcg_css on @bdi.  The returned wb has its
538  * refcount incremented.
539  *
540  * This function uses css_get() on @memcg_css and thus expects its refcnt
541  * to be positive on invocation.  IOW, rcu_read_lock() protection on
542  * @memcg_css isn't enough.  try_get it before calling this function.
543  *
544  * A wb is keyed by its associated memcg.  As blkcg implicitly enables
545  * memcg on the default hierarchy, memcg association is guaranteed to be
546  * more specific (equal or descendant to the associated blkcg) and thus can
547  * identify both the memcg and blkcg associations.
548  *
549  * Because the blkcg associated with a memcg may change as blkcg is enabled
550  * and disabled closer to root in the hierarchy, each wb keeps track of
551  * both the memcg and blkcg associated with it and verifies the blkcg on
552  * each lookup.  On mismatch, the existing wb is discarded and a new one is
553  * created.
554  */
555 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
556                                     struct cgroup_subsys_state *memcg_css)
557 {
558         struct bdi_writeback *wb;
559
560         if (!memcg_css->parent)
561                 return &bdi->wb;
562
563         rcu_read_lock();
564         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
565         if (wb) {
566                 struct cgroup_subsys_state *blkcg_css;
567
568                 /* see whether the blkcg association has changed */
569                 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
570                 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
571                         wb = NULL;
572                 css_put(blkcg_css);
573         }
574         rcu_read_unlock();
575
576         return wb;
577 }
578
579 /**
580  * wb_get_create - get wb for a given memcg, create if necessary
581  * @bdi: target bdi
582  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
583  * @gfp: allocation mask to use
584  *
585  * Try to get the wb for @memcg_css on @bdi.  If it doesn't exist, try to
586  * create one.  See wb_get_lookup() for more details.
587  */
588 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
589                                     struct cgroup_subsys_state *memcg_css,
590                                     gfp_t gfp)
591 {
592         struct bdi_writeback *wb;
593
594         might_alloc(gfp);
595
596         if (!memcg_css->parent)
597                 return &bdi->wb;
598
599         do {
600                 wb = wb_get_lookup(bdi, memcg_css);
601         } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
602
603         return wb;
604 }
605
606 static int cgwb_bdi_init(struct backing_dev_info *bdi)
607 {
608         int ret;
609
610         INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
611         mutex_init(&bdi->cgwb_release_mutex);
612         init_rwsem(&bdi->wb_switch_rwsem);
613
614         ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
615         if (!ret) {
616                 bdi->wb.memcg_css = &root_mem_cgroup->css;
617                 bdi->wb.blkcg_css = blkcg_root_css;
618         }
619         return ret;
620 }
621
622 static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
623 {
624         struct radix_tree_iter iter;
625         void **slot;
626         struct bdi_writeback *wb;
627
628         WARN_ON(test_bit(WB_registered, &bdi->wb.state));
629
630         spin_lock_irq(&cgwb_lock);
631         radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
632                 cgwb_kill(*slot);
633         spin_unlock_irq(&cgwb_lock);
634
635         mutex_lock(&bdi->cgwb_release_mutex);
636         spin_lock_irq(&cgwb_lock);
637         while (!list_empty(&bdi->wb_list)) {
638                 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
639                                       bdi_node);
640                 spin_unlock_irq(&cgwb_lock);
641                 wb_shutdown(wb);
642                 spin_lock_irq(&cgwb_lock);
643         }
644         spin_unlock_irq(&cgwb_lock);
645         mutex_unlock(&bdi->cgwb_release_mutex);
646 }
647
648 /*
649  * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
650  *
651  * Try to release dying cgwbs by switching attached inodes to the nearest
652  * living ancestor's writeback. Processed wbs are placed at the end
653  * of the list to guarantee the forward progress.
654  */
655 static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
656 {
657         struct bdi_writeback *wb;
658         LIST_HEAD(processed);
659
660         spin_lock_irq(&cgwb_lock);
661
662         while (!list_empty(&offline_cgwbs)) {
663                 wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
664                                       offline_node);
665                 list_move(&wb->offline_node, &processed);
666
667                 /*
668                  * If wb is dirty, cleaning up the writeback by switching
669                  * attached inodes will result in an effective removal of any
670                  * bandwidth restrictions, which isn't the goal.  Instead,
671                  * it can be postponed until the next time, when all io
672                  * will be likely completed.  If in the meantime some inodes
673                  * will get re-dirtied, they should be eventually switched to
674                  * a new cgwb.
675                  */
676                 if (wb_has_dirty_io(wb))
677                         continue;
678
679                 if (!wb_tryget(wb))
680                         continue;
681
682                 spin_unlock_irq(&cgwb_lock);
683                 while (cleanup_offline_cgwb(wb))
684                         cond_resched();
685                 spin_lock_irq(&cgwb_lock);
686
687                 wb_put(wb);
688         }
689
690         if (!list_empty(&processed))
691                 list_splice_tail(&processed, &offline_cgwbs);
692
693         spin_unlock_irq(&cgwb_lock);
694 }
695
696 /**
697  * wb_memcg_offline - kill all wb's associated with a memcg being offlined
698  * @memcg: memcg being offlined
699  *
700  * Also prevents creation of any new wb's associated with @memcg.
701  */
702 void wb_memcg_offline(struct mem_cgroup *memcg)
703 {
704         struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
705         struct bdi_writeback *wb, *next;
706
707         spin_lock_irq(&cgwb_lock);
708         list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
709                 cgwb_kill(wb);
710         memcg_cgwb_list->next = NULL;   /* prevent new wb's */
711         spin_unlock_irq(&cgwb_lock);
712
713         queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
714 }
715
716 /**
717  * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
718  * @css: blkcg being offlined
719  *
720  * Also prevents creation of any new wb's associated with @blkcg.
721  */
722 void wb_blkcg_offline(struct cgroup_subsys_state *css)
723 {
724         struct bdi_writeback *wb, *next;
725         struct list_head *list = blkcg_get_cgwb_list(css);
726
727         spin_lock_irq(&cgwb_lock);
728         list_for_each_entry_safe(wb, next, list, blkcg_node)
729                 cgwb_kill(wb);
730         list->next = NULL;      /* prevent new wb's */
731         spin_unlock_irq(&cgwb_lock);
732 }
733
734 static void cgwb_bdi_register(struct backing_dev_info *bdi)
735 {
736         spin_lock_irq(&cgwb_lock);
737         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
738         spin_unlock_irq(&cgwb_lock);
739 }
740
741 static int __init cgwb_init(void)
742 {
743         /*
744          * There can be many concurrent release work items overwhelming
745          * system_wq.  Put them in a separate wq and limit concurrency.
746          * There's no point in executing many of these in parallel.
747          */
748         cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
749         if (!cgwb_release_wq)
750                 return -ENOMEM;
751
752         return 0;
753 }
754 subsys_initcall(cgwb_init);
755
756 #else   /* CONFIG_CGROUP_WRITEBACK */
757
758 static int cgwb_bdi_init(struct backing_dev_info *bdi)
759 {
760         return wb_init(&bdi->wb, bdi, GFP_KERNEL);
761 }
762
763 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
764
765 static void cgwb_bdi_register(struct backing_dev_info *bdi)
766 {
767         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
768 }
769
770 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
771 {
772         list_del_rcu(&wb->bdi_node);
773 }
774
775 #endif  /* CONFIG_CGROUP_WRITEBACK */
776
777 int bdi_init(struct backing_dev_info *bdi)
778 {
779         int ret;
780
781         bdi->dev = NULL;
782
783         kref_init(&bdi->refcnt);
784         bdi->min_ratio = 0;
785         bdi->max_ratio = 100;
786         bdi->max_prop_frac = FPROP_FRAC_BASE;
787         INIT_LIST_HEAD(&bdi->bdi_list);
788         INIT_LIST_HEAD(&bdi->wb_list);
789         init_waitqueue_head(&bdi->wb_waitq);
790
791         ret = cgwb_bdi_init(bdi);
792
793         return ret;
794 }
795
796 struct backing_dev_info *bdi_alloc(int node_id)
797 {
798         struct backing_dev_info *bdi;
799
800         bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
801         if (!bdi)
802                 return NULL;
803
804         if (bdi_init(bdi)) {
805                 kfree(bdi);
806                 return NULL;
807         }
808         bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
809         bdi->ra_pages = VM_READAHEAD_PAGES;
810         bdi->io_pages = VM_READAHEAD_PAGES;
811         timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
812         return bdi;
813 }
814 EXPORT_SYMBOL(bdi_alloc);
815
816 static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
817 {
818         struct rb_node **p = &bdi_tree.rb_node;
819         struct rb_node *parent = NULL;
820         struct backing_dev_info *bdi;
821
822         lockdep_assert_held(&bdi_lock);
823
824         while (*p) {
825                 parent = *p;
826                 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
827
828                 if (bdi->id > id)
829                         p = &(*p)->rb_left;
830                 else if (bdi->id < id)
831                         p = &(*p)->rb_right;
832                 else
833                         break;
834         }
835
836         if (parentp)
837                 *parentp = parent;
838         return p;
839 }
840
841 /**
842  * bdi_get_by_id - lookup and get bdi from its id
843  * @id: bdi id to lookup
844  *
845  * Find bdi matching @id and get it.  Returns NULL if the matching bdi
846  * doesn't exist or is already unregistered.
847  */
848 struct backing_dev_info *bdi_get_by_id(u64 id)
849 {
850         struct backing_dev_info *bdi = NULL;
851         struct rb_node **p;
852
853         spin_lock_bh(&bdi_lock);
854         p = bdi_lookup_rb_node(id, NULL);
855         if (*p) {
856                 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
857                 bdi_get(bdi);
858         }
859         spin_unlock_bh(&bdi_lock);
860
861         return bdi;
862 }
863
864 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
865 {
866         struct device *dev;
867         struct rb_node *parent, **p;
868
869         if (bdi->dev)   /* The driver needs to use separate queues per device */
870                 return 0;
871
872         vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
873         dev = device_create(bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
874         if (IS_ERR(dev))
875                 return PTR_ERR(dev);
876
877         cgwb_bdi_register(bdi);
878         bdi->dev = dev;
879
880         bdi_debug_register(bdi, dev_name(dev));
881         set_bit(WB_registered, &bdi->wb.state);
882
883         spin_lock_bh(&bdi_lock);
884
885         bdi->id = ++bdi_id_cursor;
886
887         p = bdi_lookup_rb_node(bdi->id, &parent);
888         rb_link_node(&bdi->rb_node, parent, p);
889         rb_insert_color(&bdi->rb_node, &bdi_tree);
890
891         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
892
893         spin_unlock_bh(&bdi_lock);
894
895         trace_writeback_bdi_register(bdi);
896         return 0;
897 }
898
899 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
900 {
901         va_list args;
902         int ret;
903
904         va_start(args, fmt);
905         ret = bdi_register_va(bdi, fmt, args);
906         va_end(args);
907         return ret;
908 }
909 EXPORT_SYMBOL(bdi_register);
910
911 void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
912 {
913         WARN_ON_ONCE(bdi->owner);
914         bdi->owner = owner;
915         get_device(owner);
916 }
917
918 /*
919  * Remove bdi from bdi_list, and ensure that it is no longer visible
920  */
921 static void bdi_remove_from_list(struct backing_dev_info *bdi)
922 {
923         spin_lock_bh(&bdi_lock);
924         rb_erase(&bdi->rb_node, &bdi_tree);
925         list_del_rcu(&bdi->bdi_list);
926         spin_unlock_bh(&bdi_lock);
927
928         synchronize_rcu_expedited();
929 }
930
931 void bdi_unregister(struct backing_dev_info *bdi)
932 {
933         del_timer_sync(&bdi->laptop_mode_wb_timer);
934
935         /* make sure nobody finds us on the bdi_list anymore */
936         bdi_remove_from_list(bdi);
937         wb_shutdown(&bdi->wb);
938         cgwb_bdi_unregister(bdi);
939
940         /*
941          * If this BDI's min ratio has been set, use bdi_set_min_ratio() to
942          * update the global bdi_min_ratio.
943          */
944         if (bdi->min_ratio)
945                 bdi_set_min_ratio(bdi, 0);
946
947         if (bdi->dev) {
948                 bdi_debug_unregister(bdi);
949                 device_unregister(bdi->dev);
950                 bdi->dev = NULL;
951         }
952
953         if (bdi->owner) {
954                 put_device(bdi->owner);
955                 bdi->owner = NULL;
956         }
957 }
958 EXPORT_SYMBOL(bdi_unregister);
959
960 static void release_bdi(struct kref *ref)
961 {
962         struct backing_dev_info *bdi =
963                         container_of(ref, struct backing_dev_info, refcnt);
964
965         WARN_ON_ONCE(test_bit(WB_registered, &bdi->wb.state));
966         WARN_ON_ONCE(bdi->dev);
967         wb_exit(&bdi->wb);
968         kfree(bdi);
969 }
970
971 void bdi_put(struct backing_dev_info *bdi)
972 {
973         kref_put(&bdi->refcnt, release_bdi);
974 }
975 EXPORT_SYMBOL(bdi_put);
976
977 struct backing_dev_info *inode_to_bdi(struct inode *inode)
978 {
979         struct super_block *sb;
980
981         if (!inode)
982                 return &noop_backing_dev_info;
983
984         sb = inode->i_sb;
985 #ifdef CONFIG_BLOCK
986         if (sb_is_blkdev_sb(sb))
987                 return I_BDEV(inode)->bd_disk->bdi;
988 #endif
989         return sb->s_bdi;
990 }
991 EXPORT_SYMBOL(inode_to_bdi);
992
993 const char *bdi_dev_name(struct backing_dev_info *bdi)
994 {
995         if (!bdi || !bdi->dev)
996                 return bdi_unknown_name;
997         return bdi->dev_name;
998 }
999 EXPORT_SYMBOL_GPL(bdi_dev_name);