Merge drm-intel-next-queued into gvt-next
[linux-2.6-microblaze.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.h>
12 #include <linux/module.h>
13 #include <linux/writeback.h>
14 #include <linux/device.h>
15 #include <trace/events/writeback.h>
16
17 struct backing_dev_info noop_backing_dev_info = {
18         .name           = "noop",
19         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
20 };
21 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
22
23 static struct class *bdi_class;
24
25 /*
26  * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
27  * reader side locking.
28  */
29 DEFINE_SPINLOCK(bdi_lock);
30 static u64 bdi_id_cursor;
31 static struct rb_root bdi_tree = RB_ROOT;
32 LIST_HEAD(bdi_list);
33
34 /* bdi_wq serves all asynchronous writeback tasks */
35 struct workqueue_struct *bdi_wq;
36
37 #ifdef CONFIG_DEBUG_FS
38 #include <linux/debugfs.h>
39 #include <linux/seq_file.h>
40
41 static struct dentry *bdi_debug_root;
42
43 static void bdi_debug_init(void)
44 {
45         bdi_debug_root = debugfs_create_dir("bdi", NULL);
46 }
47
48 static int bdi_debug_stats_show(struct seq_file *m, void *v)
49 {
50         struct backing_dev_info *bdi = m->private;
51         struct bdi_writeback *wb = &bdi->wb;
52         unsigned long background_thresh;
53         unsigned long dirty_thresh;
54         unsigned long wb_thresh;
55         unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
56         struct inode *inode;
57
58         nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
59         spin_lock(&wb->list_lock);
60         list_for_each_entry(inode, &wb->b_dirty, i_io_list)
61                 nr_dirty++;
62         list_for_each_entry(inode, &wb->b_io, i_io_list)
63                 nr_io++;
64         list_for_each_entry(inode, &wb->b_more_io, i_io_list)
65                 nr_more_io++;
66         list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
67                 if (inode->i_state & I_DIRTY_TIME)
68                         nr_dirty_time++;
69         spin_unlock(&wb->list_lock);
70
71         global_dirty_limits(&background_thresh, &dirty_thresh);
72         wb_thresh = wb_calc_thresh(wb, dirty_thresh);
73
74 #define K(x) ((x) << (PAGE_SHIFT - 10))
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 #undef K
104
105         return 0;
106 }
107 DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
108
109 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
110 {
111         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
112
113         debugfs_create_file("stats", 0444, bdi->debug_dir, bdi,
114                             &bdi_debug_stats_fops);
115 }
116
117 static void bdi_debug_unregister(struct backing_dev_info *bdi)
118 {
119         debugfs_remove_recursive(bdi->debug_dir);
120 }
121 #else
122 static inline void bdi_debug_init(void)
123 {
124 }
125 static inline void bdi_debug_register(struct backing_dev_info *bdi,
126                                       const char *name)
127 {
128 }
129 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
130 {
131 }
132 #endif
133
134 static ssize_t read_ahead_kb_store(struct device *dev,
135                                   struct device_attribute *attr,
136                                   const char *buf, size_t count)
137 {
138         struct backing_dev_info *bdi = dev_get_drvdata(dev);
139         unsigned long read_ahead_kb;
140         ssize_t ret;
141
142         ret = kstrtoul(buf, 10, &read_ahead_kb);
143         if (ret < 0)
144                 return ret;
145
146         bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
147
148         return count;
149 }
150
151 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
152
153 #define BDI_SHOW(name, expr)                                            \
154 static ssize_t name##_show(struct device *dev,                          \
155                            struct device_attribute *attr, char *page)   \
156 {                                                                       \
157         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
158                                                                         \
159         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
160 }                                                                       \
161 static DEVICE_ATTR_RW(name);
162
163 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
164
165 static ssize_t min_ratio_store(struct device *dev,
166                 struct device_attribute *attr, const char *buf, size_t count)
167 {
168         struct backing_dev_info *bdi = dev_get_drvdata(dev);
169         unsigned int ratio;
170         ssize_t ret;
171
172         ret = kstrtouint(buf, 10, &ratio);
173         if (ret < 0)
174                 return ret;
175
176         ret = bdi_set_min_ratio(bdi, ratio);
177         if (!ret)
178                 ret = count;
179
180         return ret;
181 }
182 BDI_SHOW(min_ratio, bdi->min_ratio)
183
184 static ssize_t max_ratio_store(struct device *dev,
185                 struct device_attribute *attr, const char *buf, size_t count)
186 {
187         struct backing_dev_info *bdi = dev_get_drvdata(dev);
188         unsigned int ratio;
189         ssize_t ret;
190
191         ret = kstrtouint(buf, 10, &ratio);
192         if (ret < 0)
193                 return ret;
194
195         ret = bdi_set_max_ratio(bdi, ratio);
196         if (!ret)
197                 ret = count;
198
199         return ret;
200 }
201 BDI_SHOW(max_ratio, bdi->max_ratio)
202
203 static ssize_t stable_pages_required_show(struct device *dev,
204                                           struct device_attribute *attr,
205                                           char *page)
206 {
207         struct backing_dev_info *bdi = dev_get_drvdata(dev);
208
209         return snprintf(page, PAGE_SIZE-1, "%d\n",
210                         bdi_cap_stable_pages_required(bdi) ? 1 : 0);
211 }
212 static DEVICE_ATTR_RO(stable_pages_required);
213
214 static struct attribute *bdi_dev_attrs[] = {
215         &dev_attr_read_ahead_kb.attr,
216         &dev_attr_min_ratio.attr,
217         &dev_attr_max_ratio.attr,
218         &dev_attr_stable_pages_required.attr,
219         NULL,
220 };
221 ATTRIBUTE_GROUPS(bdi_dev);
222
223 static __init int bdi_class_init(void)
224 {
225         bdi_class = class_create(THIS_MODULE, "bdi");
226         if (IS_ERR(bdi_class))
227                 return PTR_ERR(bdi_class);
228
229         bdi_class->dev_groups = bdi_dev_groups;
230         bdi_debug_init();
231
232         return 0;
233 }
234 postcore_initcall(bdi_class_init);
235
236 static int bdi_init(struct backing_dev_info *bdi);
237
238 static int __init default_bdi_init(void)
239 {
240         int err;
241
242         bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
243                                  WQ_SYSFS, 0);
244         if (!bdi_wq)
245                 return -ENOMEM;
246
247         err = bdi_init(&noop_backing_dev_info);
248
249         return err;
250 }
251 subsys_initcall(default_bdi_init);
252
253 /*
254  * This function is used when the first inode for this wb is marked dirty. It
255  * wakes-up the corresponding bdi thread which should then take care of the
256  * periodic background write-out of dirty inodes. Since the write-out would
257  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
258  * set up a timer which wakes the bdi thread up later.
259  *
260  * Note, we wouldn't bother setting up the timer, but this function is on the
261  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
262  * by delaying the wake-up.
263  *
264  * We have to be careful not to postpone flush work if it is scheduled for
265  * earlier. Thus we use queue_delayed_work().
266  */
267 void wb_wakeup_delayed(struct bdi_writeback *wb)
268 {
269         unsigned long timeout;
270
271         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
272         spin_lock_bh(&wb->work_lock);
273         if (test_bit(WB_registered, &wb->state))
274                 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
275         spin_unlock_bh(&wb->work_lock);
276 }
277
278 /*
279  * Initial write bandwidth: 100 MB/s
280  */
281 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
282
283 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
284                    int blkcg_id, gfp_t gfp)
285 {
286         int i, err;
287
288         memset(wb, 0, sizeof(*wb));
289
290         if (wb != &bdi->wb)
291                 bdi_get(bdi);
292         wb->bdi = bdi;
293         wb->last_old_flush = jiffies;
294         INIT_LIST_HEAD(&wb->b_dirty);
295         INIT_LIST_HEAD(&wb->b_io);
296         INIT_LIST_HEAD(&wb->b_more_io);
297         INIT_LIST_HEAD(&wb->b_dirty_time);
298         spin_lock_init(&wb->list_lock);
299
300         wb->bw_time_stamp = jiffies;
301         wb->balanced_dirty_ratelimit = INIT_BW;
302         wb->dirty_ratelimit = INIT_BW;
303         wb->write_bandwidth = INIT_BW;
304         wb->avg_write_bandwidth = INIT_BW;
305
306         spin_lock_init(&wb->work_lock);
307         INIT_LIST_HEAD(&wb->work_list);
308         INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
309         wb->dirty_sleep = jiffies;
310
311         wb->congested = wb_congested_get_create(bdi, blkcg_id, gfp);
312         if (!wb->congested) {
313                 err = -ENOMEM;
314                 goto out_put_bdi;
315         }
316
317         err = fprop_local_init_percpu(&wb->completions, gfp);
318         if (err)
319                 goto out_put_cong;
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_cong:
334         wb_congested_put(wb->congested);
335 out_put_bdi:
336         if (wb != &bdi->wb)
337                 bdi_put(bdi);
338         return err;
339 }
340
341 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
342
343 /*
344  * Remove bdi from the global list and shutdown any threads we have running
345  */
346 static void wb_shutdown(struct bdi_writeback *wb)
347 {
348         /* Make sure nobody queues further work */
349         spin_lock_bh(&wb->work_lock);
350         if (!test_and_clear_bit(WB_registered, &wb->state)) {
351                 spin_unlock_bh(&wb->work_lock);
352                 return;
353         }
354         spin_unlock_bh(&wb->work_lock);
355
356         cgwb_remove_from_bdi_list(wb);
357         /*
358          * Drain work list and shutdown the delayed_work.  !WB_registered
359          * tells wb_workfn() that @wb is dying and its work_list needs to
360          * be drained no matter what.
361          */
362         mod_delayed_work(bdi_wq, &wb->dwork, 0);
363         flush_delayed_work(&wb->dwork);
364         WARN_ON(!list_empty(&wb->work_list));
365 }
366
367 static void wb_exit(struct bdi_writeback *wb)
368 {
369         int i;
370
371         WARN_ON(delayed_work_pending(&wb->dwork));
372
373         for (i = 0; i < NR_WB_STAT_ITEMS; i++)
374                 percpu_counter_destroy(&wb->stat[i]);
375
376         fprop_local_destroy_percpu(&wb->completions);
377         wb_congested_put(wb->congested);
378         if (wb != &wb->bdi->wb)
379                 bdi_put(wb->bdi);
380 }
381
382 #ifdef CONFIG_CGROUP_WRITEBACK
383
384 #include <linux/memcontrol.h>
385
386 /*
387  * cgwb_lock protects bdi->cgwb_tree, bdi->cgwb_congested_tree,
388  * blkcg->cgwb_list, and memcg->cgwb_list.  bdi->cgwb_tree is also RCU
389  * protected.
390  */
391 static DEFINE_SPINLOCK(cgwb_lock);
392 static struct workqueue_struct *cgwb_release_wq;
393
394 /**
395  * wb_congested_get_create - get or create a wb_congested
396  * @bdi: associated bdi
397  * @blkcg_id: ID of the associated blkcg
398  * @gfp: allocation mask
399  *
400  * Look up the wb_congested for @blkcg_id on @bdi.  If missing, create one.
401  * The returned wb_congested has its reference count incremented.  Returns
402  * NULL on failure.
403  */
404 struct bdi_writeback_congested *
405 wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
406 {
407         struct bdi_writeback_congested *new_congested = NULL, *congested;
408         struct rb_node **node, *parent;
409         unsigned long flags;
410 retry:
411         spin_lock_irqsave(&cgwb_lock, flags);
412
413         node = &bdi->cgwb_congested_tree.rb_node;
414         parent = NULL;
415
416         while (*node != NULL) {
417                 parent = *node;
418                 congested = rb_entry(parent, struct bdi_writeback_congested,
419                                      rb_node);
420                 if (congested->blkcg_id < blkcg_id)
421                         node = &parent->rb_left;
422                 else if (congested->blkcg_id > blkcg_id)
423                         node = &parent->rb_right;
424                 else
425                         goto found;
426         }
427
428         if (new_congested) {
429                 /* !found and storage for new one already allocated, insert */
430                 congested = new_congested;
431                 rb_link_node(&congested->rb_node, parent, node);
432                 rb_insert_color(&congested->rb_node, &bdi->cgwb_congested_tree);
433                 spin_unlock_irqrestore(&cgwb_lock, flags);
434                 return congested;
435         }
436
437         spin_unlock_irqrestore(&cgwb_lock, flags);
438
439         /* allocate storage for new one and retry */
440         new_congested = kzalloc(sizeof(*new_congested), gfp);
441         if (!new_congested)
442                 return NULL;
443
444         refcount_set(&new_congested->refcnt, 1);
445         new_congested->__bdi = bdi;
446         new_congested->blkcg_id = blkcg_id;
447         goto retry;
448
449 found:
450         refcount_inc(&congested->refcnt);
451         spin_unlock_irqrestore(&cgwb_lock, flags);
452         kfree(new_congested);
453         return congested;
454 }
455
456 /**
457  * wb_congested_put - put a wb_congested
458  * @congested: wb_congested to put
459  *
460  * Put @congested and destroy it if the refcnt reaches zero.
461  */
462 void wb_congested_put(struct bdi_writeback_congested *congested)
463 {
464         unsigned long flags;
465
466         if (!refcount_dec_and_lock_irqsave(&congested->refcnt, &cgwb_lock, &flags))
467                 return;
468
469         /* bdi might already have been destroyed leaving @congested unlinked */
470         if (congested->__bdi) {
471                 rb_erase(&congested->rb_node,
472                          &congested->__bdi->cgwb_congested_tree);
473                 congested->__bdi = NULL;
474         }
475
476         spin_unlock_irqrestore(&cgwb_lock, flags);
477         kfree(congested);
478 }
479
480 static void cgwb_release_workfn(struct work_struct *work)
481 {
482         struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
483                                                 release_work);
484         struct blkcg *blkcg = css_to_blkcg(wb->blkcg_css);
485
486         mutex_lock(&wb->bdi->cgwb_release_mutex);
487         wb_shutdown(wb);
488
489         css_put(wb->memcg_css);
490         css_put(wb->blkcg_css);
491         mutex_unlock(&wb->bdi->cgwb_release_mutex);
492
493         /* triggers blkg destruction if cgwb_refcnt becomes zero */
494         blkcg_cgwb_put(blkcg);
495
496         fprop_local_destroy_percpu(&wb->memcg_completions);
497         percpu_ref_exit(&wb->refcnt);
498         wb_exit(wb);
499         kfree_rcu(wb, rcu);
500 }
501
502 static void cgwb_release(struct percpu_ref *refcnt)
503 {
504         struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
505                                                 refcnt);
506         queue_work(cgwb_release_wq, &wb->release_work);
507 }
508
509 static void cgwb_kill(struct bdi_writeback *wb)
510 {
511         lockdep_assert_held(&cgwb_lock);
512
513         WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
514         list_del(&wb->memcg_node);
515         list_del(&wb->blkcg_node);
516         percpu_ref_kill(&wb->refcnt);
517 }
518
519 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
520 {
521         spin_lock_irq(&cgwb_lock);
522         list_del_rcu(&wb->bdi_node);
523         spin_unlock_irq(&cgwb_lock);
524 }
525
526 static int cgwb_create(struct backing_dev_info *bdi,
527                        struct cgroup_subsys_state *memcg_css, gfp_t gfp)
528 {
529         struct mem_cgroup *memcg;
530         struct cgroup_subsys_state *blkcg_css;
531         struct blkcg *blkcg;
532         struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
533         struct bdi_writeback *wb;
534         unsigned long flags;
535         int ret = 0;
536
537         memcg = mem_cgroup_from_css(memcg_css);
538         blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
539         blkcg = css_to_blkcg(blkcg_css);
540         memcg_cgwb_list = &memcg->cgwb_list;
541         blkcg_cgwb_list = &blkcg->cgwb_list;
542
543         /* look up again under lock and discard on blkcg mismatch */
544         spin_lock_irqsave(&cgwb_lock, flags);
545         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
546         if (wb && wb->blkcg_css != blkcg_css) {
547                 cgwb_kill(wb);
548                 wb = NULL;
549         }
550         spin_unlock_irqrestore(&cgwb_lock, flags);
551         if (wb)
552                 goto out_put;
553
554         /* need to create a new one */
555         wb = kmalloc(sizeof(*wb), gfp);
556         if (!wb) {
557                 ret = -ENOMEM;
558                 goto out_put;
559         }
560
561         ret = wb_init(wb, bdi, blkcg_css->id, gfp);
562         if (ret)
563                 goto err_free;
564
565         ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
566         if (ret)
567                 goto err_wb_exit;
568
569         ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
570         if (ret)
571                 goto err_ref_exit;
572
573         wb->memcg_css = memcg_css;
574         wb->blkcg_css = blkcg_css;
575         INIT_WORK(&wb->release_work, cgwb_release_workfn);
576         set_bit(WB_registered, &wb->state);
577
578         /*
579          * The root wb determines the registered state of the whole bdi and
580          * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
581          * whether they're still online.  Don't link @wb if any is dead.
582          * See wb_memcg_offline() and wb_blkcg_offline().
583          */
584         ret = -ENODEV;
585         spin_lock_irqsave(&cgwb_lock, flags);
586         if (test_bit(WB_registered, &bdi->wb.state) &&
587             blkcg_cgwb_list->next && memcg_cgwb_list->next) {
588                 /* we might have raced another instance of this function */
589                 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
590                 if (!ret) {
591                         list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
592                         list_add(&wb->memcg_node, memcg_cgwb_list);
593                         list_add(&wb->blkcg_node, blkcg_cgwb_list);
594                         blkcg_cgwb_get(blkcg);
595                         css_get(memcg_css);
596                         css_get(blkcg_css);
597                 }
598         }
599         spin_unlock_irqrestore(&cgwb_lock, flags);
600         if (ret) {
601                 if (ret == -EEXIST)
602                         ret = 0;
603                 goto err_fprop_exit;
604         }
605         goto out_put;
606
607 err_fprop_exit:
608         fprop_local_destroy_percpu(&wb->memcg_completions);
609 err_ref_exit:
610         percpu_ref_exit(&wb->refcnt);
611 err_wb_exit:
612         wb_exit(wb);
613 err_free:
614         kfree(wb);
615 out_put:
616         css_put(blkcg_css);
617         return ret;
618 }
619
620 /**
621  * wb_get_lookup - get wb for a given memcg
622  * @bdi: target bdi
623  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
624  *
625  * Try to get the wb for @memcg_css on @bdi.  The returned wb has its
626  * refcount incremented.
627  *
628  * This function uses css_get() on @memcg_css and thus expects its refcnt
629  * to be positive on invocation.  IOW, rcu_read_lock() protection on
630  * @memcg_css isn't enough.  try_get it before calling this function.
631  *
632  * A wb is keyed by its associated memcg.  As blkcg implicitly enables
633  * memcg on the default hierarchy, memcg association is guaranteed to be
634  * more specific (equal or descendant to the associated blkcg) and thus can
635  * identify both the memcg and blkcg associations.
636  *
637  * Because the blkcg associated with a memcg may change as blkcg is enabled
638  * and disabled closer to root in the hierarchy, each wb keeps track of
639  * both the memcg and blkcg associated with it and verifies the blkcg on
640  * each lookup.  On mismatch, the existing wb is discarded and a new one is
641  * created.
642  */
643 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
644                                     struct cgroup_subsys_state *memcg_css)
645 {
646         struct bdi_writeback *wb;
647
648         if (!memcg_css->parent)
649                 return &bdi->wb;
650
651         rcu_read_lock();
652         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
653         if (wb) {
654                 struct cgroup_subsys_state *blkcg_css;
655
656                 /* see whether the blkcg association has changed */
657                 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
658                 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
659                         wb = NULL;
660                 css_put(blkcg_css);
661         }
662         rcu_read_unlock();
663
664         return wb;
665 }
666
667 /**
668  * wb_get_create - get wb for a given memcg, create if necessary
669  * @bdi: target bdi
670  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
671  * @gfp: allocation mask to use
672  *
673  * Try to get the wb for @memcg_css on @bdi.  If it doesn't exist, try to
674  * create one.  See wb_get_lookup() for more details.
675  */
676 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
677                                     struct cgroup_subsys_state *memcg_css,
678                                     gfp_t gfp)
679 {
680         struct bdi_writeback *wb;
681
682         might_sleep_if(gfpflags_allow_blocking(gfp));
683
684         if (!memcg_css->parent)
685                 return &bdi->wb;
686
687         do {
688                 wb = wb_get_lookup(bdi, memcg_css);
689         } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
690
691         return wb;
692 }
693
694 static int cgwb_bdi_init(struct backing_dev_info *bdi)
695 {
696         int ret;
697
698         INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
699         bdi->cgwb_congested_tree = RB_ROOT;
700         mutex_init(&bdi->cgwb_release_mutex);
701         init_rwsem(&bdi->wb_switch_rwsem);
702
703         ret = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
704         if (!ret) {
705                 bdi->wb.memcg_css = &root_mem_cgroup->css;
706                 bdi->wb.blkcg_css = blkcg_root_css;
707         }
708         return ret;
709 }
710
711 static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
712 {
713         struct radix_tree_iter iter;
714         void **slot;
715         struct bdi_writeback *wb;
716
717         WARN_ON(test_bit(WB_registered, &bdi->wb.state));
718
719         spin_lock_irq(&cgwb_lock);
720         radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
721                 cgwb_kill(*slot);
722         spin_unlock_irq(&cgwb_lock);
723
724         mutex_lock(&bdi->cgwb_release_mutex);
725         spin_lock_irq(&cgwb_lock);
726         while (!list_empty(&bdi->wb_list)) {
727                 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
728                                       bdi_node);
729                 spin_unlock_irq(&cgwb_lock);
730                 wb_shutdown(wb);
731                 spin_lock_irq(&cgwb_lock);
732         }
733         spin_unlock_irq(&cgwb_lock);
734         mutex_unlock(&bdi->cgwb_release_mutex);
735 }
736
737 /**
738  * wb_memcg_offline - kill all wb's associated with a memcg being offlined
739  * @memcg: memcg being offlined
740  *
741  * Also prevents creation of any new wb's associated with @memcg.
742  */
743 void wb_memcg_offline(struct mem_cgroup *memcg)
744 {
745         struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
746         struct bdi_writeback *wb, *next;
747
748         spin_lock_irq(&cgwb_lock);
749         list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
750                 cgwb_kill(wb);
751         memcg_cgwb_list->next = NULL;   /* prevent new wb's */
752         spin_unlock_irq(&cgwb_lock);
753 }
754
755 /**
756  * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
757  * @blkcg: blkcg being offlined
758  *
759  * Also prevents creation of any new wb's associated with @blkcg.
760  */
761 void wb_blkcg_offline(struct blkcg *blkcg)
762 {
763         struct bdi_writeback *wb, *next;
764
765         spin_lock_irq(&cgwb_lock);
766         list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node)
767                 cgwb_kill(wb);
768         blkcg->cgwb_list.next = NULL;   /* prevent new wb's */
769         spin_unlock_irq(&cgwb_lock);
770 }
771
772 static void cgwb_bdi_exit(struct backing_dev_info *bdi)
773 {
774         struct rb_node *rbn;
775
776         spin_lock_irq(&cgwb_lock);
777         while ((rbn = rb_first(&bdi->cgwb_congested_tree))) {
778                 struct bdi_writeback_congested *congested =
779                         rb_entry(rbn, struct bdi_writeback_congested, rb_node);
780
781                 rb_erase(rbn, &bdi->cgwb_congested_tree);
782                 congested->__bdi = NULL;        /* mark @congested unlinked */
783         }
784         spin_unlock_irq(&cgwb_lock);
785 }
786
787 static void cgwb_bdi_register(struct backing_dev_info *bdi)
788 {
789         spin_lock_irq(&cgwb_lock);
790         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
791         spin_unlock_irq(&cgwb_lock);
792 }
793
794 static int __init cgwb_init(void)
795 {
796         /*
797          * There can be many concurrent release work items overwhelming
798          * system_wq.  Put them in a separate wq and limit concurrency.
799          * There's no point in executing many of these in parallel.
800          */
801         cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
802         if (!cgwb_release_wq)
803                 return -ENOMEM;
804
805         return 0;
806 }
807 subsys_initcall(cgwb_init);
808
809 #else   /* CONFIG_CGROUP_WRITEBACK */
810
811 static int cgwb_bdi_init(struct backing_dev_info *bdi)
812 {
813         int err;
814
815         bdi->wb_congested = kzalloc(sizeof(*bdi->wb_congested), GFP_KERNEL);
816         if (!bdi->wb_congested)
817                 return -ENOMEM;
818
819         refcount_set(&bdi->wb_congested->refcnt, 1);
820
821         err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
822         if (err) {
823                 wb_congested_put(bdi->wb_congested);
824                 return err;
825         }
826         return 0;
827 }
828
829 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
830
831 static void cgwb_bdi_exit(struct backing_dev_info *bdi)
832 {
833         wb_congested_put(bdi->wb_congested);
834 }
835
836 static void cgwb_bdi_register(struct backing_dev_info *bdi)
837 {
838         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
839 }
840
841 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
842 {
843         list_del_rcu(&wb->bdi_node);
844 }
845
846 #endif  /* CONFIG_CGROUP_WRITEBACK */
847
848 static int bdi_init(struct backing_dev_info *bdi)
849 {
850         int ret;
851
852         bdi->dev = NULL;
853
854         kref_init(&bdi->refcnt);
855         bdi->min_ratio = 0;
856         bdi->max_ratio = 100;
857         bdi->max_prop_frac = FPROP_FRAC_BASE;
858         INIT_LIST_HEAD(&bdi->bdi_list);
859         INIT_LIST_HEAD(&bdi->wb_list);
860         init_waitqueue_head(&bdi->wb_waitq);
861
862         ret = cgwb_bdi_init(bdi);
863
864         return ret;
865 }
866
867 struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id)
868 {
869         struct backing_dev_info *bdi;
870
871         bdi = kmalloc_node(sizeof(struct backing_dev_info),
872                            gfp_mask | __GFP_ZERO, node_id);
873         if (!bdi)
874                 return NULL;
875
876         if (bdi_init(bdi)) {
877                 kfree(bdi);
878                 return NULL;
879         }
880         return bdi;
881 }
882 EXPORT_SYMBOL(bdi_alloc_node);
883
884 static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
885 {
886         struct rb_node **p = &bdi_tree.rb_node;
887         struct rb_node *parent = NULL;
888         struct backing_dev_info *bdi;
889
890         lockdep_assert_held(&bdi_lock);
891
892         while (*p) {
893                 parent = *p;
894                 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
895
896                 if (bdi->id > id)
897                         p = &(*p)->rb_left;
898                 else if (bdi->id < id)
899                         p = &(*p)->rb_right;
900                 else
901                         break;
902         }
903
904         if (parentp)
905                 *parentp = parent;
906         return p;
907 }
908
909 /**
910  * bdi_get_by_id - lookup and get bdi from its id
911  * @id: bdi id to lookup
912  *
913  * Find bdi matching @id and get it.  Returns NULL if the matching bdi
914  * doesn't exist or is already unregistered.
915  */
916 struct backing_dev_info *bdi_get_by_id(u64 id)
917 {
918         struct backing_dev_info *bdi = NULL;
919         struct rb_node **p;
920
921         spin_lock_bh(&bdi_lock);
922         p = bdi_lookup_rb_node(id, NULL);
923         if (*p) {
924                 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
925                 bdi_get(bdi);
926         }
927         spin_unlock_bh(&bdi_lock);
928
929         return bdi;
930 }
931
932 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
933 {
934         struct device *dev;
935         struct rb_node *parent, **p;
936
937         if (bdi->dev)   /* The driver needs to use separate queues per device */
938                 return 0;
939
940         dev = device_create_vargs(bdi_class, NULL, MKDEV(0, 0), bdi, fmt, args);
941         if (IS_ERR(dev))
942                 return PTR_ERR(dev);
943
944         cgwb_bdi_register(bdi);
945         bdi->dev = dev;
946
947         bdi_debug_register(bdi, dev_name(dev));
948         set_bit(WB_registered, &bdi->wb.state);
949
950         spin_lock_bh(&bdi_lock);
951
952         bdi->id = ++bdi_id_cursor;
953
954         p = bdi_lookup_rb_node(bdi->id, &parent);
955         rb_link_node(&bdi->rb_node, parent, p);
956         rb_insert_color(&bdi->rb_node, &bdi_tree);
957
958         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
959
960         spin_unlock_bh(&bdi_lock);
961
962         trace_writeback_bdi_register(bdi);
963         return 0;
964 }
965 EXPORT_SYMBOL(bdi_register_va);
966
967 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
968 {
969         va_list args;
970         int ret;
971
972         va_start(args, fmt);
973         ret = bdi_register_va(bdi, fmt, args);
974         va_end(args);
975         return ret;
976 }
977 EXPORT_SYMBOL(bdi_register);
978
979 int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner)
980 {
981         int rc;
982
983         rc = bdi_register(bdi, "%u:%u", MAJOR(owner->devt), MINOR(owner->devt));
984         if (rc)
985                 return rc;
986         /* Leaking owner reference... */
987         WARN_ON(bdi->owner);
988         bdi->owner = owner;
989         get_device(owner);
990         return 0;
991 }
992 EXPORT_SYMBOL(bdi_register_owner);
993
994 /*
995  * Remove bdi from bdi_list, and ensure that it is no longer visible
996  */
997 static void bdi_remove_from_list(struct backing_dev_info *bdi)
998 {
999         spin_lock_bh(&bdi_lock);
1000         rb_erase(&bdi->rb_node, &bdi_tree);
1001         list_del_rcu(&bdi->bdi_list);
1002         spin_unlock_bh(&bdi_lock);
1003
1004         synchronize_rcu_expedited();
1005 }
1006
1007 void bdi_unregister(struct backing_dev_info *bdi)
1008 {
1009         /* make sure nobody finds us on the bdi_list anymore */
1010         bdi_remove_from_list(bdi);
1011         wb_shutdown(&bdi->wb);
1012         cgwb_bdi_unregister(bdi);
1013
1014         if (bdi->dev) {
1015                 bdi_debug_unregister(bdi);
1016                 device_unregister(bdi->dev);
1017                 bdi->dev = NULL;
1018         }
1019
1020         if (bdi->owner) {
1021                 put_device(bdi->owner);
1022                 bdi->owner = NULL;
1023         }
1024 }
1025
1026 static void release_bdi(struct kref *ref)
1027 {
1028         struct backing_dev_info *bdi =
1029                         container_of(ref, struct backing_dev_info, refcnt);
1030
1031         if (test_bit(WB_registered, &bdi->wb.state))
1032                 bdi_unregister(bdi);
1033         WARN_ON_ONCE(bdi->dev);
1034         wb_exit(&bdi->wb);
1035         cgwb_bdi_exit(bdi);
1036         kfree(bdi);
1037 }
1038
1039 void bdi_put(struct backing_dev_info *bdi)
1040 {
1041         kref_put(&bdi->refcnt, release_bdi);
1042 }
1043 EXPORT_SYMBOL(bdi_put);
1044
1045 static wait_queue_head_t congestion_wqh[2] = {
1046                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
1047                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
1048         };
1049 static atomic_t nr_wb_congested[2];
1050
1051 void clear_wb_congested(struct bdi_writeback_congested *congested, int sync)
1052 {
1053         wait_queue_head_t *wqh = &congestion_wqh[sync];
1054         enum wb_congested_state bit;
1055
1056         bit = sync ? WB_sync_congested : WB_async_congested;
1057         if (test_and_clear_bit(bit, &congested->state))
1058                 atomic_dec(&nr_wb_congested[sync]);
1059         smp_mb__after_atomic();
1060         if (waitqueue_active(wqh))
1061                 wake_up(wqh);
1062 }
1063 EXPORT_SYMBOL(clear_wb_congested);
1064
1065 void set_wb_congested(struct bdi_writeback_congested *congested, int sync)
1066 {
1067         enum wb_congested_state bit;
1068
1069         bit = sync ? WB_sync_congested : WB_async_congested;
1070         if (!test_and_set_bit(bit, &congested->state))
1071                 atomic_inc(&nr_wb_congested[sync]);
1072 }
1073 EXPORT_SYMBOL(set_wb_congested);
1074
1075 /**
1076  * congestion_wait - wait for a backing_dev to become uncongested
1077  * @sync: SYNC or ASYNC IO
1078  * @timeout: timeout in jiffies
1079  *
1080  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
1081  * write congestion.  If no backing_devs are congested then just wait for the
1082  * next write to be completed.
1083  */
1084 long congestion_wait(int sync, long timeout)
1085 {
1086         long ret;
1087         unsigned long start = jiffies;
1088         DEFINE_WAIT(wait);
1089         wait_queue_head_t *wqh = &congestion_wqh[sync];
1090
1091         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1092         ret = io_schedule_timeout(timeout);
1093         finish_wait(wqh, &wait);
1094
1095         trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
1096                                         jiffies_to_usecs(jiffies - start));
1097
1098         return ret;
1099 }
1100 EXPORT_SYMBOL(congestion_wait);
1101
1102 /**
1103  * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a pgdat to complete writes
1104  * @sync: SYNC or ASYNC IO
1105  * @timeout: timeout in jiffies
1106  *
1107  * In the event of a congested backing_dev (any backing_dev) this waits
1108  * for up to @timeout jiffies for either a BDI to exit congestion of the
1109  * given @sync queue or a write to complete.
1110  *
1111  * The return value is 0 if the sleep is for the full timeout. Otherwise,
1112  * it is the number of jiffies that were still remaining when the function
1113  * returned. return_value == timeout implies the function did not sleep.
1114  */
1115 long wait_iff_congested(int sync, long timeout)
1116 {
1117         long ret;
1118         unsigned long start = jiffies;
1119         DEFINE_WAIT(wait);
1120         wait_queue_head_t *wqh = &congestion_wqh[sync];
1121
1122         /*
1123          * If there is no congestion, yield if necessary instead
1124          * of sleeping on the congestion queue
1125          */
1126         if (atomic_read(&nr_wb_congested[sync]) == 0) {
1127                 cond_resched();
1128
1129                 /* In case we scheduled, work out time remaining */
1130                 ret = timeout - (jiffies - start);
1131                 if (ret < 0)
1132                         ret = 0;
1133
1134                 goto out;
1135         }
1136
1137         /* Sleep until uncongested or a write happens */
1138         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1139         ret = io_schedule_timeout(timeout);
1140         finish_wait(wqh, &wait);
1141
1142 out:
1143         trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
1144                                         jiffies_to_usecs(jiffies - start));
1145
1146         return ret;
1147 }
1148 EXPORT_SYMBOL(wait_iff_congested);