Merge branch 'for-5.6' of https://git.kernel.org/pub/scm/linux/kernel/git/broonie...
[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 const char *bdi_unknown_name = "(unknown)";
25
26 /*
27  * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
28  * reader side locking.
29  */
30 DEFINE_SPINLOCK(bdi_lock);
31 static u64 bdi_id_cursor;
32 static struct rb_root bdi_tree = RB_ROOT;
33 LIST_HEAD(bdi_list);
34
35 /* bdi_wq serves all asynchronous writeback tasks */
36 struct workqueue_struct *bdi_wq;
37
38 #ifdef CONFIG_DEBUG_FS
39 #include <linux/debugfs.h>
40 #include <linux/seq_file.h>
41
42 static struct dentry *bdi_debug_root;
43
44 static void bdi_debug_init(void)
45 {
46         bdi_debug_root = debugfs_create_dir("bdi", NULL);
47 }
48
49 static int bdi_debug_stats_show(struct seq_file *m, void *v)
50 {
51         struct backing_dev_info *bdi = m->private;
52         struct bdi_writeback *wb = &bdi->wb;
53         unsigned long background_thresh;
54         unsigned long dirty_thresh;
55         unsigned long wb_thresh;
56         unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
57         struct inode *inode;
58
59         nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
60         spin_lock(&wb->list_lock);
61         list_for_each_entry(inode, &wb->b_dirty, i_io_list)
62                 nr_dirty++;
63         list_for_each_entry(inode, &wb->b_io, i_io_list)
64                 nr_io++;
65         list_for_each_entry(inode, &wb->b_more_io, i_io_list)
66                 nr_more_io++;
67         list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
68                 if (inode->i_state & I_DIRTY_TIME)
69                         nr_dirty_time++;
70         spin_unlock(&wb->list_lock);
71
72         global_dirty_limits(&background_thresh, &dirty_thresh);
73         wb_thresh = wb_calc_thresh(wb, dirty_thresh);
74
75 #define K(x) ((x) << (PAGE_SHIFT - 10))
76         seq_printf(m,
77                    "BdiWriteback:       %10lu kB\n"
78                    "BdiReclaimable:     %10lu kB\n"
79                    "BdiDirtyThresh:     %10lu kB\n"
80                    "DirtyThresh:        %10lu kB\n"
81                    "BackgroundThresh:   %10lu kB\n"
82                    "BdiDirtied:         %10lu kB\n"
83                    "BdiWritten:         %10lu kB\n"
84                    "BdiWriteBandwidth:  %10lu kBps\n"
85                    "b_dirty:            %10lu\n"
86                    "b_io:               %10lu\n"
87                    "b_more_io:          %10lu\n"
88                    "b_dirty_time:       %10lu\n"
89                    "bdi_list:           %10u\n"
90                    "state:              %10lx\n",
91                    (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
92                    (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
93                    K(wb_thresh),
94                    K(dirty_thresh),
95                    K(background_thresh),
96                    (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
97                    (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
98                    (unsigned long) K(wb->write_bandwidth),
99                    nr_dirty,
100                    nr_io,
101                    nr_more_io,
102                    nr_dirty_time,
103                    !list_empty(&bdi->bdi_list), bdi->wb.state);
104 #undef K
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 K(pages) ((pages) << (PAGE_SHIFT - 10))
153
154 #define BDI_SHOW(name, expr)                                            \
155 static ssize_t name##_show(struct device *dev,                          \
156                            struct device_attribute *attr, char *page)   \
157 {                                                                       \
158         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
159                                                                         \
160         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
161 }                                                                       \
162 static DEVICE_ATTR_RW(name);
163
164 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
165
166 static ssize_t min_ratio_store(struct device *dev,
167                 struct device_attribute *attr, const char *buf, size_t count)
168 {
169         struct backing_dev_info *bdi = dev_get_drvdata(dev);
170         unsigned int ratio;
171         ssize_t ret;
172
173         ret = kstrtouint(buf, 10, &ratio);
174         if (ret < 0)
175                 return ret;
176
177         ret = bdi_set_min_ratio(bdi, ratio);
178         if (!ret)
179                 ret = count;
180
181         return ret;
182 }
183 BDI_SHOW(min_ratio, bdi->min_ratio)
184
185 static ssize_t max_ratio_store(struct device *dev,
186                 struct device_attribute *attr, const char *buf, size_t count)
187 {
188         struct backing_dev_info *bdi = dev_get_drvdata(dev);
189         unsigned int ratio;
190         ssize_t ret;
191
192         ret = kstrtouint(buf, 10, &ratio);
193         if (ret < 0)
194                 return ret;
195
196         ret = bdi_set_max_ratio(bdi, ratio);
197         if (!ret)
198                 ret = count;
199
200         return ret;
201 }
202 BDI_SHOW(max_ratio, bdi->max_ratio)
203
204 static ssize_t stable_pages_required_show(struct device *dev,
205                                           struct device_attribute *attr,
206                                           char *page)
207 {
208         struct backing_dev_info *bdi = dev_get_drvdata(dev);
209
210         return snprintf(page, PAGE_SIZE-1, "%d\n",
211                         bdi_cap_stable_pages_required(bdi) ? 1 : 0);
212 }
213 static DEVICE_ATTR_RO(stable_pages_required);
214
215 static struct attribute *bdi_dev_attrs[] = {
216         &dev_attr_read_ahead_kb.attr,
217         &dev_attr_min_ratio.attr,
218         &dev_attr_max_ratio.attr,
219         &dev_attr_stable_pages_required.attr,
220         NULL,
221 };
222 ATTRIBUTE_GROUPS(bdi_dev);
223
224 static __init int bdi_class_init(void)
225 {
226         bdi_class = class_create(THIS_MODULE, "bdi");
227         if (IS_ERR(bdi_class))
228                 return PTR_ERR(bdi_class);
229
230         bdi_class->dev_groups = bdi_dev_groups;
231         bdi_debug_init();
232
233         return 0;
234 }
235 postcore_initcall(bdi_class_init);
236
237 static int bdi_init(struct backing_dev_info *bdi);
238
239 static int __init default_bdi_init(void)
240 {
241         int err;
242
243         bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
244                                  WQ_SYSFS, 0);
245         if (!bdi_wq)
246                 return -ENOMEM;
247
248         err = bdi_init(&noop_backing_dev_info);
249
250         return err;
251 }
252 subsys_initcall(default_bdi_init);
253
254 /*
255  * This function is used when the first inode for this wb is marked dirty. It
256  * wakes-up the corresponding bdi thread which should then take care of the
257  * periodic background write-out of dirty inodes. Since the write-out would
258  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
259  * set up a timer which wakes the bdi thread up later.
260  *
261  * Note, we wouldn't bother setting up the timer, but this function is on the
262  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
263  * by delaying the wake-up.
264  *
265  * We have to be careful not to postpone flush work if it is scheduled for
266  * earlier. Thus we use queue_delayed_work().
267  */
268 void wb_wakeup_delayed(struct bdi_writeback *wb)
269 {
270         unsigned long timeout;
271
272         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
273         spin_lock_bh(&wb->work_lock);
274         if (test_bit(WB_registered, &wb->state))
275                 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
276         spin_unlock_bh(&wb->work_lock);
277 }
278
279 /*
280  * Initial write bandwidth: 100 MB/s
281  */
282 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
283
284 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
285                    int blkcg_id, gfp_t gfp)
286 {
287         int i, err;
288
289         memset(wb, 0, sizeof(*wb));
290
291         if (wb != &bdi->wb)
292                 bdi_get(bdi);
293         wb->bdi = bdi;
294         wb->last_old_flush = jiffies;
295         INIT_LIST_HEAD(&wb->b_dirty);
296         INIT_LIST_HEAD(&wb->b_io);
297         INIT_LIST_HEAD(&wb->b_more_io);
298         INIT_LIST_HEAD(&wb->b_dirty_time);
299         spin_lock_init(&wb->list_lock);
300
301         wb->bw_time_stamp = jiffies;
302         wb->balanced_dirty_ratelimit = INIT_BW;
303         wb->dirty_ratelimit = INIT_BW;
304         wb->write_bandwidth = INIT_BW;
305         wb->avg_write_bandwidth = INIT_BW;
306
307         spin_lock_init(&wb->work_lock);
308         INIT_LIST_HEAD(&wb->work_list);
309         INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
310         wb->dirty_sleep = jiffies;
311
312         wb->congested = wb_congested_get_create(bdi, blkcg_id, gfp);
313         if (!wb->congested) {
314                 err = -ENOMEM;
315                 goto out_put_bdi;
316         }
317
318         err = fprop_local_init_percpu(&wb->completions, gfp);
319         if (err)
320                 goto out_put_cong;
321
322         for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
323                 err = percpu_counter_init(&wb->stat[i], 0, gfp);
324                 if (err)
325                         goto out_destroy_stat;
326         }
327
328         return 0;
329
330 out_destroy_stat:
331         while (i--)
332                 percpu_counter_destroy(&wb->stat[i]);
333         fprop_local_destroy_percpu(&wb->completions);
334 out_put_cong:
335         wb_congested_put(wb->congested);
336 out_put_bdi:
337         if (wb != &bdi->wb)
338                 bdi_put(bdi);
339         return err;
340 }
341
342 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
343
344 /*
345  * Remove bdi from the global list and shutdown any threads we have running
346  */
347 static void wb_shutdown(struct bdi_writeback *wb)
348 {
349         /* Make sure nobody queues further work */
350         spin_lock_bh(&wb->work_lock);
351         if (!test_and_clear_bit(WB_registered, &wb->state)) {
352                 spin_unlock_bh(&wb->work_lock);
353                 return;
354         }
355         spin_unlock_bh(&wb->work_lock);
356
357         cgwb_remove_from_bdi_list(wb);
358         /*
359          * Drain work list and shutdown the delayed_work.  !WB_registered
360          * tells wb_workfn() that @wb is dying and its work_list needs to
361          * be drained no matter what.
362          */
363         mod_delayed_work(bdi_wq, &wb->dwork, 0);
364         flush_delayed_work(&wb->dwork);
365         WARN_ON(!list_empty(&wb->work_list));
366 }
367
368 static void wb_exit(struct bdi_writeback *wb)
369 {
370         int i;
371
372         WARN_ON(delayed_work_pending(&wb->dwork));
373
374         for (i = 0; i < NR_WB_STAT_ITEMS; i++)
375                 percpu_counter_destroy(&wb->stat[i]);
376
377         fprop_local_destroy_percpu(&wb->completions);
378         wb_congested_put(wb->congested);
379         if (wb != &wb->bdi->wb)
380                 bdi_put(wb->bdi);
381 }
382
383 #ifdef CONFIG_CGROUP_WRITEBACK
384
385 #include <linux/memcontrol.h>
386
387 /*
388  * cgwb_lock protects bdi->cgwb_tree, bdi->cgwb_congested_tree,
389  * blkcg->cgwb_list, and memcg->cgwb_list.  bdi->cgwb_tree is also RCU
390  * protected.
391  */
392 static DEFINE_SPINLOCK(cgwb_lock);
393 static struct workqueue_struct *cgwb_release_wq;
394
395 /**
396  * wb_congested_get_create - get or create a wb_congested
397  * @bdi: associated bdi
398  * @blkcg_id: ID of the associated blkcg
399  * @gfp: allocation mask
400  *
401  * Look up the wb_congested for @blkcg_id on @bdi.  If missing, create one.
402  * The returned wb_congested has its reference count incremented.  Returns
403  * NULL on failure.
404  */
405 struct bdi_writeback_congested *
406 wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
407 {
408         struct bdi_writeback_congested *new_congested = NULL, *congested;
409         struct rb_node **node, *parent;
410         unsigned long flags;
411 retry:
412         spin_lock_irqsave(&cgwb_lock, flags);
413
414         node = &bdi->cgwb_congested_tree.rb_node;
415         parent = NULL;
416
417         while (*node != NULL) {
418                 parent = *node;
419                 congested = rb_entry(parent, struct bdi_writeback_congested,
420                                      rb_node);
421                 if (congested->blkcg_id < blkcg_id)
422                         node = &parent->rb_left;
423                 else if (congested->blkcg_id > blkcg_id)
424                         node = &parent->rb_right;
425                 else
426                         goto found;
427         }
428
429         if (new_congested) {
430                 /* !found and storage for new one already allocated, insert */
431                 congested = new_congested;
432                 rb_link_node(&congested->rb_node, parent, node);
433                 rb_insert_color(&congested->rb_node, &bdi->cgwb_congested_tree);
434                 spin_unlock_irqrestore(&cgwb_lock, flags);
435                 return congested;
436         }
437
438         spin_unlock_irqrestore(&cgwb_lock, flags);
439
440         /* allocate storage for new one and retry */
441         new_congested = kzalloc(sizeof(*new_congested), gfp);
442         if (!new_congested)
443                 return NULL;
444
445         refcount_set(&new_congested->refcnt, 1);
446         new_congested->__bdi = bdi;
447         new_congested->blkcg_id = blkcg_id;
448         goto retry;
449
450 found:
451         refcount_inc(&congested->refcnt);
452         spin_unlock_irqrestore(&cgwb_lock, flags);
453         kfree(new_congested);
454         return congested;
455 }
456
457 /**
458  * wb_congested_put - put a wb_congested
459  * @congested: wb_congested to put
460  *
461  * Put @congested and destroy it if the refcnt reaches zero.
462  */
463 void wb_congested_put(struct bdi_writeback_congested *congested)
464 {
465         unsigned long flags;
466
467         if (!refcount_dec_and_lock_irqsave(&congested->refcnt, &cgwb_lock, &flags))
468                 return;
469
470         /* bdi might already have been destroyed leaving @congested unlinked */
471         if (congested->__bdi) {
472                 rb_erase(&congested->rb_node,
473                          &congested->__bdi->cgwb_congested_tree);
474                 congested->__bdi = NULL;
475         }
476
477         spin_unlock_irqrestore(&cgwb_lock, flags);
478         kfree(congested);
479 }
480
481 static void cgwb_release_workfn(struct work_struct *work)
482 {
483         struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
484                                                 release_work);
485         struct blkcg *blkcg = css_to_blkcg(wb->blkcg_css);
486
487         mutex_lock(&wb->bdi->cgwb_release_mutex);
488         wb_shutdown(wb);
489
490         css_put(wb->memcg_css);
491         css_put(wb->blkcg_css);
492         mutex_unlock(&wb->bdi->cgwb_release_mutex);
493
494         /* triggers blkg destruction if cgwb_refcnt becomes zero */
495         blkcg_cgwb_put(blkcg);
496
497         fprop_local_destroy_percpu(&wb->memcg_completions);
498         percpu_ref_exit(&wb->refcnt);
499         wb_exit(wb);
500         kfree_rcu(wb, rcu);
501 }
502
503 static void cgwb_release(struct percpu_ref *refcnt)
504 {
505         struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
506                                                 refcnt);
507         queue_work(cgwb_release_wq, &wb->release_work);
508 }
509
510 static void cgwb_kill(struct bdi_writeback *wb)
511 {
512         lockdep_assert_held(&cgwb_lock);
513
514         WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
515         list_del(&wb->memcg_node);
516         list_del(&wb->blkcg_node);
517         percpu_ref_kill(&wb->refcnt);
518 }
519
520 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
521 {
522         spin_lock_irq(&cgwb_lock);
523         list_del_rcu(&wb->bdi_node);
524         spin_unlock_irq(&cgwb_lock);
525 }
526
527 static int cgwb_create(struct backing_dev_info *bdi,
528                        struct cgroup_subsys_state *memcg_css, gfp_t gfp)
529 {
530         struct mem_cgroup *memcg;
531         struct cgroup_subsys_state *blkcg_css;
532         struct blkcg *blkcg;
533         struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
534         struct bdi_writeback *wb;
535         unsigned long flags;
536         int ret = 0;
537
538         memcg = mem_cgroup_from_css(memcg_css);
539         blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
540         blkcg = css_to_blkcg(blkcg_css);
541         memcg_cgwb_list = &memcg->cgwb_list;
542         blkcg_cgwb_list = &blkcg->cgwb_list;
543
544         /* look up again under lock and discard on blkcg mismatch */
545         spin_lock_irqsave(&cgwb_lock, flags);
546         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
547         if (wb && wb->blkcg_css != blkcg_css) {
548                 cgwb_kill(wb);
549                 wb = NULL;
550         }
551         spin_unlock_irqrestore(&cgwb_lock, flags);
552         if (wb)
553                 goto out_put;
554
555         /* need to create a new one */
556         wb = kmalloc(sizeof(*wb), gfp);
557         if (!wb) {
558                 ret = -ENOMEM;
559                 goto out_put;
560         }
561
562         ret = wb_init(wb, bdi, blkcg_css->id, gfp);
563         if (ret)
564                 goto err_free;
565
566         ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
567         if (ret)
568                 goto err_wb_exit;
569
570         ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
571         if (ret)
572                 goto err_ref_exit;
573
574         wb->memcg_css = memcg_css;
575         wb->blkcg_css = blkcg_css;
576         INIT_WORK(&wb->release_work, cgwb_release_workfn);
577         set_bit(WB_registered, &wb->state);
578
579         /*
580          * The root wb determines the registered state of the whole bdi and
581          * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
582          * whether they're still online.  Don't link @wb if any is dead.
583          * See wb_memcg_offline() and wb_blkcg_offline().
584          */
585         ret = -ENODEV;
586         spin_lock_irqsave(&cgwb_lock, flags);
587         if (test_bit(WB_registered, &bdi->wb.state) &&
588             blkcg_cgwb_list->next && memcg_cgwb_list->next) {
589                 /* we might have raced another instance of this function */
590                 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
591                 if (!ret) {
592                         list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
593                         list_add(&wb->memcg_node, memcg_cgwb_list);
594                         list_add(&wb->blkcg_node, blkcg_cgwb_list);
595                         blkcg_cgwb_get(blkcg);
596                         css_get(memcg_css);
597                         css_get(blkcg_css);
598                 }
599         }
600         spin_unlock_irqrestore(&cgwb_lock, flags);
601         if (ret) {
602                 if (ret == -EEXIST)
603                         ret = 0;
604                 goto err_fprop_exit;
605         }
606         goto out_put;
607
608 err_fprop_exit:
609         fprop_local_destroy_percpu(&wb->memcg_completions);
610 err_ref_exit:
611         percpu_ref_exit(&wb->refcnt);
612 err_wb_exit:
613         wb_exit(wb);
614 err_free:
615         kfree(wb);
616 out_put:
617         css_put(blkcg_css);
618         return ret;
619 }
620
621 /**
622  * wb_get_lookup - get wb for a given memcg
623  * @bdi: target bdi
624  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
625  *
626  * Try to get the wb for @memcg_css on @bdi.  The returned wb has its
627  * refcount incremented.
628  *
629  * This function uses css_get() on @memcg_css and thus expects its refcnt
630  * to be positive on invocation.  IOW, rcu_read_lock() protection on
631  * @memcg_css isn't enough.  try_get it before calling this function.
632  *
633  * A wb is keyed by its associated memcg.  As blkcg implicitly enables
634  * memcg on the default hierarchy, memcg association is guaranteed to be
635  * more specific (equal or descendant to the associated blkcg) and thus can
636  * identify both the memcg and blkcg associations.
637  *
638  * Because the blkcg associated with a memcg may change as blkcg is enabled
639  * and disabled closer to root in the hierarchy, each wb keeps track of
640  * both the memcg and blkcg associated with it and verifies the blkcg on
641  * each lookup.  On mismatch, the existing wb is discarded and a new one is
642  * created.
643  */
644 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
645                                     struct cgroup_subsys_state *memcg_css)
646 {
647         struct bdi_writeback *wb;
648
649         if (!memcg_css->parent)
650                 return &bdi->wb;
651
652         rcu_read_lock();
653         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
654         if (wb) {
655                 struct cgroup_subsys_state *blkcg_css;
656
657                 /* see whether the blkcg association has changed */
658                 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
659                 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
660                         wb = NULL;
661                 css_put(blkcg_css);
662         }
663         rcu_read_unlock();
664
665         return wb;
666 }
667
668 /**
669  * wb_get_create - get wb for a given memcg, create if necessary
670  * @bdi: target bdi
671  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
672  * @gfp: allocation mask to use
673  *
674  * Try to get the wb for @memcg_css on @bdi.  If it doesn't exist, try to
675  * create one.  See wb_get_lookup() for more details.
676  */
677 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
678                                     struct cgroup_subsys_state *memcg_css,
679                                     gfp_t gfp)
680 {
681         struct bdi_writeback *wb;
682
683         might_sleep_if(gfpflags_allow_blocking(gfp));
684
685         if (!memcg_css->parent)
686                 return &bdi->wb;
687
688         do {
689                 wb = wb_get_lookup(bdi, memcg_css);
690         } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
691
692         return wb;
693 }
694
695 static int cgwb_bdi_init(struct backing_dev_info *bdi)
696 {
697         int ret;
698
699         INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
700         bdi->cgwb_congested_tree = RB_ROOT;
701         mutex_init(&bdi->cgwb_release_mutex);
702         init_rwsem(&bdi->wb_switch_rwsem);
703
704         ret = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
705         if (!ret) {
706                 bdi->wb.memcg_css = &root_mem_cgroup->css;
707                 bdi->wb.blkcg_css = blkcg_root_css;
708         }
709         return ret;
710 }
711
712 static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
713 {
714         struct radix_tree_iter iter;
715         void **slot;
716         struct bdi_writeback *wb;
717
718         WARN_ON(test_bit(WB_registered, &bdi->wb.state));
719
720         spin_lock_irq(&cgwb_lock);
721         radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
722                 cgwb_kill(*slot);
723         spin_unlock_irq(&cgwb_lock);
724
725         mutex_lock(&bdi->cgwb_release_mutex);
726         spin_lock_irq(&cgwb_lock);
727         while (!list_empty(&bdi->wb_list)) {
728                 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
729                                       bdi_node);
730                 spin_unlock_irq(&cgwb_lock);
731                 wb_shutdown(wb);
732                 spin_lock_irq(&cgwb_lock);
733         }
734         spin_unlock_irq(&cgwb_lock);
735         mutex_unlock(&bdi->cgwb_release_mutex);
736 }
737
738 /**
739  * wb_memcg_offline - kill all wb's associated with a memcg being offlined
740  * @memcg: memcg being offlined
741  *
742  * Also prevents creation of any new wb's associated with @memcg.
743  */
744 void wb_memcg_offline(struct mem_cgroup *memcg)
745 {
746         struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
747         struct bdi_writeback *wb, *next;
748
749         spin_lock_irq(&cgwb_lock);
750         list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
751                 cgwb_kill(wb);
752         memcg_cgwb_list->next = NULL;   /* prevent new wb's */
753         spin_unlock_irq(&cgwb_lock);
754 }
755
756 /**
757  * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
758  * @blkcg: blkcg being offlined
759  *
760  * Also prevents creation of any new wb's associated with @blkcg.
761  */
762 void wb_blkcg_offline(struct blkcg *blkcg)
763 {
764         struct bdi_writeback *wb, *next;
765
766         spin_lock_irq(&cgwb_lock);
767         list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node)
768                 cgwb_kill(wb);
769         blkcg->cgwb_list.next = NULL;   /* prevent new wb's */
770         spin_unlock_irq(&cgwb_lock);
771 }
772
773 static void cgwb_bdi_exit(struct backing_dev_info *bdi)
774 {
775         struct rb_node *rbn;
776
777         spin_lock_irq(&cgwb_lock);
778         while ((rbn = rb_first(&bdi->cgwb_congested_tree))) {
779                 struct bdi_writeback_congested *congested =
780                         rb_entry(rbn, struct bdi_writeback_congested, rb_node);
781
782                 rb_erase(rbn, &bdi->cgwb_congested_tree);
783                 congested->__bdi = NULL;        /* mark @congested unlinked */
784         }
785         spin_unlock_irq(&cgwb_lock);
786 }
787
788 static void cgwb_bdi_register(struct backing_dev_info *bdi)
789 {
790         spin_lock_irq(&cgwb_lock);
791         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
792         spin_unlock_irq(&cgwb_lock);
793 }
794
795 static int __init cgwb_init(void)
796 {
797         /*
798          * There can be many concurrent release work items overwhelming
799          * system_wq.  Put them in a separate wq and limit concurrency.
800          * There's no point in executing many of these in parallel.
801          */
802         cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
803         if (!cgwb_release_wq)
804                 return -ENOMEM;
805
806         return 0;
807 }
808 subsys_initcall(cgwb_init);
809
810 #else   /* CONFIG_CGROUP_WRITEBACK */
811
812 static int cgwb_bdi_init(struct backing_dev_info *bdi)
813 {
814         int err;
815
816         bdi->wb_congested = kzalloc(sizeof(*bdi->wb_congested), GFP_KERNEL);
817         if (!bdi->wb_congested)
818                 return -ENOMEM;
819
820         refcount_set(&bdi->wb_congested->refcnt, 1);
821
822         err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
823         if (err) {
824                 wb_congested_put(bdi->wb_congested);
825                 return err;
826         }
827         return 0;
828 }
829
830 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
831
832 static void cgwb_bdi_exit(struct backing_dev_info *bdi)
833 {
834         wb_congested_put(bdi->wb_congested);
835 }
836
837 static void cgwb_bdi_register(struct backing_dev_info *bdi)
838 {
839         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
840 }
841
842 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
843 {
844         list_del_rcu(&wb->bdi_node);
845 }
846
847 #endif  /* CONFIG_CGROUP_WRITEBACK */
848
849 static int bdi_init(struct backing_dev_info *bdi)
850 {
851         int ret;
852
853         bdi->dev = NULL;
854
855         kref_init(&bdi->refcnt);
856         bdi->min_ratio = 0;
857         bdi->max_ratio = 100;
858         bdi->max_prop_frac = FPROP_FRAC_BASE;
859         INIT_LIST_HEAD(&bdi->bdi_list);
860         INIT_LIST_HEAD(&bdi->wb_list);
861         init_waitqueue_head(&bdi->wb_waitq);
862
863         ret = cgwb_bdi_init(bdi);
864
865         return ret;
866 }
867
868 struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id)
869 {
870         struct backing_dev_info *bdi;
871
872         bdi = kmalloc_node(sizeof(struct backing_dev_info),
873                            gfp_mask | __GFP_ZERO, node_id);
874         if (!bdi)
875                 return NULL;
876
877         if (bdi_init(bdi)) {
878                 kfree(bdi);
879                 return NULL;
880         }
881         return bdi;
882 }
883 EXPORT_SYMBOL(bdi_alloc_node);
884
885 static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
886 {
887         struct rb_node **p = &bdi_tree.rb_node;
888         struct rb_node *parent = NULL;
889         struct backing_dev_info *bdi;
890
891         lockdep_assert_held(&bdi_lock);
892
893         while (*p) {
894                 parent = *p;
895                 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
896
897                 if (bdi->id > id)
898                         p = &(*p)->rb_left;
899                 else if (bdi->id < id)
900                         p = &(*p)->rb_right;
901                 else
902                         break;
903         }
904
905         if (parentp)
906                 *parentp = parent;
907         return p;
908 }
909
910 /**
911  * bdi_get_by_id - lookup and get bdi from its id
912  * @id: bdi id to lookup
913  *
914  * Find bdi matching @id and get it.  Returns NULL if the matching bdi
915  * doesn't exist or is already unregistered.
916  */
917 struct backing_dev_info *bdi_get_by_id(u64 id)
918 {
919         struct backing_dev_info *bdi = NULL;
920         struct rb_node **p;
921
922         spin_lock_bh(&bdi_lock);
923         p = bdi_lookup_rb_node(id, NULL);
924         if (*p) {
925                 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
926                 bdi_get(bdi);
927         }
928         spin_unlock_bh(&bdi_lock);
929
930         return bdi;
931 }
932
933 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
934 {
935         struct device *dev;
936         struct rb_node *parent, **p;
937
938         if (bdi->dev)   /* The driver needs to use separate queues per device */
939                 return 0;
940
941         dev = device_create_vargs(bdi_class, NULL, MKDEV(0, 0), bdi, fmt, args);
942         if (IS_ERR(dev))
943                 return PTR_ERR(dev);
944
945         cgwb_bdi_register(bdi);
946         bdi->dev = dev;
947
948         bdi_debug_register(bdi, dev_name(dev));
949         set_bit(WB_registered, &bdi->wb.state);
950
951         spin_lock_bh(&bdi_lock);
952
953         bdi->id = ++bdi_id_cursor;
954
955         p = bdi_lookup_rb_node(bdi->id, &parent);
956         rb_link_node(&bdi->rb_node, parent, p);
957         rb_insert_color(&bdi->rb_node, &bdi_tree);
958
959         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
960
961         spin_unlock_bh(&bdi_lock);
962
963         trace_writeback_bdi_register(bdi);
964         return 0;
965 }
966 EXPORT_SYMBOL(bdi_register_va);
967
968 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
969 {
970         va_list args;
971         int ret;
972
973         va_start(args, fmt);
974         ret = bdi_register_va(bdi, fmt, args);
975         va_end(args);
976         return ret;
977 }
978 EXPORT_SYMBOL(bdi_register);
979
980 int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner)
981 {
982         int rc;
983
984         rc = bdi_register(bdi, "%u:%u", MAJOR(owner->devt), MINOR(owner->devt));
985         if (rc)
986                 return rc;
987         /* Leaking owner reference... */
988         WARN_ON(bdi->owner);
989         bdi->owner = owner;
990         get_device(owner);
991         return 0;
992 }
993 EXPORT_SYMBOL(bdi_register_owner);
994
995 /*
996  * Remove bdi from bdi_list, and ensure that it is no longer visible
997  */
998 static void bdi_remove_from_list(struct backing_dev_info *bdi)
999 {
1000         spin_lock_bh(&bdi_lock);
1001         rb_erase(&bdi->rb_node, &bdi_tree);
1002         list_del_rcu(&bdi->bdi_list);
1003         spin_unlock_bh(&bdi_lock);
1004
1005         synchronize_rcu_expedited();
1006 }
1007
1008 void bdi_unregister(struct backing_dev_info *bdi)
1009 {
1010         /* make sure nobody finds us on the bdi_list anymore */
1011         bdi_remove_from_list(bdi);
1012         wb_shutdown(&bdi->wb);
1013         cgwb_bdi_unregister(bdi);
1014
1015         if (bdi->dev) {
1016                 bdi_debug_unregister(bdi);
1017                 device_unregister(bdi->dev);
1018                 bdi->dev = NULL;
1019         }
1020
1021         if (bdi->owner) {
1022                 put_device(bdi->owner);
1023                 bdi->owner = NULL;
1024         }
1025 }
1026
1027 static void release_bdi(struct kref *ref)
1028 {
1029         struct backing_dev_info *bdi =
1030                         container_of(ref, struct backing_dev_info, refcnt);
1031
1032         if (test_bit(WB_registered, &bdi->wb.state))
1033                 bdi_unregister(bdi);
1034         WARN_ON_ONCE(bdi->dev);
1035         wb_exit(&bdi->wb);
1036         cgwb_bdi_exit(bdi);
1037         kfree(bdi);
1038 }
1039
1040 void bdi_put(struct backing_dev_info *bdi)
1041 {
1042         kref_put(&bdi->refcnt, release_bdi);
1043 }
1044 EXPORT_SYMBOL(bdi_put);
1045
1046 static wait_queue_head_t congestion_wqh[2] = {
1047                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
1048                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
1049         };
1050 static atomic_t nr_wb_congested[2];
1051
1052 void clear_wb_congested(struct bdi_writeback_congested *congested, int sync)
1053 {
1054         wait_queue_head_t *wqh = &congestion_wqh[sync];
1055         enum wb_congested_state bit;
1056
1057         bit = sync ? WB_sync_congested : WB_async_congested;
1058         if (test_and_clear_bit(bit, &congested->state))
1059                 atomic_dec(&nr_wb_congested[sync]);
1060         smp_mb__after_atomic();
1061         if (waitqueue_active(wqh))
1062                 wake_up(wqh);
1063 }
1064 EXPORT_SYMBOL(clear_wb_congested);
1065
1066 void set_wb_congested(struct bdi_writeback_congested *congested, int sync)
1067 {
1068         enum wb_congested_state bit;
1069
1070         bit = sync ? WB_sync_congested : WB_async_congested;
1071         if (!test_and_set_bit(bit, &congested->state))
1072                 atomic_inc(&nr_wb_congested[sync]);
1073 }
1074 EXPORT_SYMBOL(set_wb_congested);
1075
1076 /**
1077  * congestion_wait - wait for a backing_dev to become uncongested
1078  * @sync: SYNC or ASYNC IO
1079  * @timeout: timeout in jiffies
1080  *
1081  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
1082  * write congestion.  If no backing_devs are congested then just wait for the
1083  * next write to be completed.
1084  */
1085 long congestion_wait(int sync, long timeout)
1086 {
1087         long ret;
1088         unsigned long start = jiffies;
1089         DEFINE_WAIT(wait);
1090         wait_queue_head_t *wqh = &congestion_wqh[sync];
1091
1092         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1093         ret = io_schedule_timeout(timeout);
1094         finish_wait(wqh, &wait);
1095
1096         trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
1097                                         jiffies_to_usecs(jiffies - start));
1098
1099         return ret;
1100 }
1101 EXPORT_SYMBOL(congestion_wait);
1102
1103 /**
1104  * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a pgdat to complete writes
1105  * @sync: SYNC or ASYNC IO
1106  * @timeout: timeout in jiffies
1107  *
1108  * In the event of a congested backing_dev (any backing_dev) this waits
1109  * for up to @timeout jiffies for either a BDI to exit congestion of the
1110  * given @sync queue or a write to complete.
1111  *
1112  * The return value is 0 if the sleep is for the full timeout. Otherwise,
1113  * it is the number of jiffies that were still remaining when the function
1114  * returned. return_value == timeout implies the function did not sleep.
1115  */
1116 long wait_iff_congested(int sync, long timeout)
1117 {
1118         long ret;
1119         unsigned long start = jiffies;
1120         DEFINE_WAIT(wait);
1121         wait_queue_head_t *wqh = &congestion_wqh[sync];
1122
1123         /*
1124          * If there is no congestion, yield if necessary instead
1125          * of sleeping on the congestion queue
1126          */
1127         if (atomic_read(&nr_wb_congested[sync]) == 0) {
1128                 cond_resched();
1129
1130                 /* In case we scheduled, work out time remaining */
1131                 ret = timeout - (jiffies - start);
1132                 if (ret < 0)
1133                         ret = 0;
1134
1135                 goto out;
1136         }
1137
1138         /* Sleep until uncongested or a write happens */
1139         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1140         ret = io_schedule_timeout(timeout);
1141         finish_wait(wqh, &wait);
1142
1143 out:
1144         trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
1145                                         jiffies_to_usecs(jiffies - start));
1146
1147         return ret;
1148 }
1149 EXPORT_SYMBOL(wait_iff_congested);