c6f2a37028c205db8143ebe58677c790c66a0faf
[sfrench/cifs-2.6.git] / mm / backing-dev.c
1
2 #include <linux/wait.h>
3 #include <linux/backing-dev.h>
4 #include <linux/kthread.h>
5 #include <linux/freezer.h>
6 #include <linux/fs.h>
7 #include <linux/pagemap.h>
8 #include <linux/mm.h>
9 #include <linux/sched.h>
10 #include <linux/module.h>
11 #include <linux/writeback.h>
12 #include <linux/device.h>
13 #include <trace/events/writeback.h>
14
15 static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
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 updates to bdi_list. bdi_list has RCU reader side
27  * locking.
28  */
29 DEFINE_SPINLOCK(bdi_lock);
30 LIST_HEAD(bdi_list);
31
32 /* bdi_wq serves all asynchronous writeback tasks */
33 struct workqueue_struct *bdi_wq;
34
35 #ifdef CONFIG_DEBUG_FS
36 #include <linux/debugfs.h>
37 #include <linux/seq_file.h>
38
39 static struct dentry *bdi_debug_root;
40
41 static void bdi_debug_init(void)
42 {
43         bdi_debug_root = debugfs_create_dir("bdi", NULL);
44 }
45
46 static int bdi_debug_stats_show(struct seq_file *m, void *v)
47 {
48         struct backing_dev_info *bdi = m->private;
49         struct bdi_writeback *wb = &bdi->wb;
50         unsigned long background_thresh;
51         unsigned long dirty_thresh;
52         unsigned long wb_thresh;
53         unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
54         struct inode *inode;
55
56         nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
57         spin_lock(&wb->list_lock);
58         list_for_each_entry(inode, &wb->b_dirty, i_io_list)
59                 nr_dirty++;
60         list_for_each_entry(inode, &wb->b_io, i_io_list)
61                 nr_io++;
62         list_for_each_entry(inode, &wb->b_more_io, i_io_list)
63                 nr_more_io++;
64         list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
65                 if (inode->i_state & I_DIRTY_TIME)
66                         nr_dirty_time++;
67         spin_unlock(&wb->list_lock);
68
69         global_dirty_limits(&background_thresh, &dirty_thresh);
70         wb_thresh = wb_calc_thresh(wb, dirty_thresh);
71
72 #define K(x) ((x) << (PAGE_SHIFT - 10))
73         seq_printf(m,
74                    "BdiWriteback:       %10lu kB\n"
75                    "BdiReclaimable:     %10lu kB\n"
76                    "BdiDirtyThresh:     %10lu kB\n"
77                    "DirtyThresh:        %10lu kB\n"
78                    "BackgroundThresh:   %10lu kB\n"
79                    "BdiDirtied:         %10lu kB\n"
80                    "BdiWritten:         %10lu kB\n"
81                    "BdiWriteBandwidth:  %10lu kBps\n"
82                    "b_dirty:            %10lu\n"
83                    "b_io:               %10lu\n"
84                    "b_more_io:          %10lu\n"
85                    "b_dirty_time:       %10lu\n"
86                    "bdi_list:           %10u\n"
87                    "state:              %10lx\n",
88                    (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
89                    (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
90                    K(wb_thresh),
91                    K(dirty_thresh),
92                    K(background_thresh),
93                    (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
94                    (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
95                    (unsigned long) K(wb->write_bandwidth),
96                    nr_dirty,
97                    nr_io,
98                    nr_more_io,
99                    nr_dirty_time,
100                    !list_empty(&bdi->bdi_list), bdi->wb.state);
101 #undef K
102
103         return 0;
104 }
105
106 static int bdi_debug_stats_open(struct inode *inode, struct file *file)
107 {
108         return single_open(file, bdi_debug_stats_show, inode->i_private);
109 }
110
111 static const struct file_operations bdi_debug_stats_fops = {
112         .open           = bdi_debug_stats_open,
113         .read           = seq_read,
114         .llseek         = seq_lseek,
115         .release        = single_release,
116 };
117
118 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
119 {
120         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
121         bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
122                                                bdi, &bdi_debug_stats_fops);
123 }
124
125 static void bdi_debug_unregister(struct backing_dev_info *bdi)
126 {
127         debugfs_remove(bdi->debug_stats);
128         debugfs_remove(bdi->debug_dir);
129 }
130 #else
131 static inline void bdi_debug_init(void)
132 {
133 }
134 static inline void bdi_debug_register(struct backing_dev_info *bdi,
135                                       const char *name)
136 {
137 }
138 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
139 {
140 }
141 #endif
142
143 static ssize_t read_ahead_kb_store(struct device *dev,
144                                   struct device_attribute *attr,
145                                   const char *buf, size_t count)
146 {
147         struct backing_dev_info *bdi = dev_get_drvdata(dev);
148         unsigned long read_ahead_kb;
149         ssize_t ret;
150
151         ret = kstrtoul(buf, 10, &read_ahead_kb);
152         if (ret < 0)
153                 return ret;
154
155         bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
156
157         return count;
158 }
159
160 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
161
162 #define BDI_SHOW(name, expr)                                            \
163 static ssize_t name##_show(struct device *dev,                          \
164                            struct device_attribute *attr, char *page)   \
165 {                                                                       \
166         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
167                                                                         \
168         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
169 }                                                                       \
170 static DEVICE_ATTR_RW(name);
171
172 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
173
174 static ssize_t min_ratio_store(struct device *dev,
175                 struct device_attribute *attr, const char *buf, size_t count)
176 {
177         struct backing_dev_info *bdi = dev_get_drvdata(dev);
178         unsigned int ratio;
179         ssize_t ret;
180
181         ret = kstrtouint(buf, 10, &ratio);
182         if (ret < 0)
183                 return ret;
184
185         ret = bdi_set_min_ratio(bdi, ratio);
186         if (!ret)
187                 ret = count;
188
189         return ret;
190 }
191 BDI_SHOW(min_ratio, bdi->min_ratio)
192
193 static ssize_t max_ratio_store(struct device *dev,
194                 struct device_attribute *attr, const char *buf, size_t count)
195 {
196         struct backing_dev_info *bdi = dev_get_drvdata(dev);
197         unsigned int ratio;
198         ssize_t ret;
199
200         ret = kstrtouint(buf, 10, &ratio);
201         if (ret < 0)
202                 return ret;
203
204         ret = bdi_set_max_ratio(bdi, ratio);
205         if (!ret)
206                 ret = count;
207
208         return ret;
209 }
210 BDI_SHOW(max_ratio, bdi->max_ratio)
211
212 static ssize_t stable_pages_required_show(struct device *dev,
213                                           struct device_attribute *attr,
214                                           char *page)
215 {
216         struct backing_dev_info *bdi = dev_get_drvdata(dev);
217
218         return snprintf(page, PAGE_SIZE-1, "%d\n",
219                         bdi_cap_stable_pages_required(bdi) ? 1 : 0);
220 }
221 static DEVICE_ATTR_RO(stable_pages_required);
222
223 static struct attribute *bdi_dev_attrs[] = {
224         &dev_attr_read_ahead_kb.attr,
225         &dev_attr_min_ratio.attr,
226         &dev_attr_max_ratio.attr,
227         &dev_attr_stable_pages_required.attr,
228         NULL,
229 };
230 ATTRIBUTE_GROUPS(bdi_dev);
231
232 static __init int bdi_class_init(void)
233 {
234         bdi_class = class_create(THIS_MODULE, "bdi");
235         if (IS_ERR(bdi_class))
236                 return PTR_ERR(bdi_class);
237
238         bdi_class->dev_groups = bdi_dev_groups;
239         bdi_debug_init();
240
241         return 0;
242 }
243 postcore_initcall(bdi_class_init);
244
245 static int __init default_bdi_init(void)
246 {
247         int err;
248
249         bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE |
250                                               WQ_UNBOUND | WQ_SYSFS, 0);
251         if (!bdi_wq)
252                 return -ENOMEM;
253
254         err = bdi_init(&noop_backing_dev_info);
255
256         return err;
257 }
258 subsys_initcall(default_bdi_init);
259
260 /*
261  * This function is used when the first inode for this wb is marked dirty. It
262  * wakes-up the corresponding bdi thread which should then take care of the
263  * periodic background write-out of dirty inodes. Since the write-out would
264  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
265  * set up a timer which wakes the bdi thread up later.
266  *
267  * Note, we wouldn't bother setting up the timer, but this function is on the
268  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
269  * by delaying the wake-up.
270  *
271  * We have to be careful not to postpone flush work if it is scheduled for
272  * earlier. Thus we use queue_delayed_work().
273  */
274 void wb_wakeup_delayed(struct bdi_writeback *wb)
275 {
276         unsigned long timeout;
277
278         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
279         spin_lock_bh(&wb->work_lock);
280         if (test_bit(WB_registered, &wb->state))
281                 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
282         spin_unlock_bh(&wb->work_lock);
283 }
284
285 /*
286  * Initial write bandwidth: 100 MB/s
287  */
288 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
289
290 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
291                    int blkcg_id, gfp_t gfp)
292 {
293         int i, err;
294
295         memset(wb, 0, sizeof(*wb));
296
297         wb->bdi = bdi;
298         wb->last_old_flush = jiffies;
299         INIT_LIST_HEAD(&wb->b_dirty);
300         INIT_LIST_HEAD(&wb->b_io);
301         INIT_LIST_HEAD(&wb->b_more_io);
302         INIT_LIST_HEAD(&wb->b_dirty_time);
303         spin_lock_init(&wb->list_lock);
304
305         wb->bw_time_stamp = jiffies;
306         wb->balanced_dirty_ratelimit = INIT_BW;
307         wb->dirty_ratelimit = INIT_BW;
308         wb->write_bandwidth = INIT_BW;
309         wb->avg_write_bandwidth = INIT_BW;
310
311         spin_lock_init(&wb->work_lock);
312         INIT_LIST_HEAD(&wb->work_list);
313         INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
314         wb->dirty_sleep = jiffies;
315
316         wb->congested = wb_congested_get_create(bdi, blkcg_id, gfp);
317         if (!wb->congested)
318                 return -ENOMEM;
319
320         err = fprop_local_init_percpu(&wb->completions, gfp);
321         if (err)
322                 goto out_put_cong;
323
324         for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
325                 err = percpu_counter_init(&wb->stat[i], 0, gfp);
326                 if (err)
327                         goto out_destroy_stat;
328         }
329
330         return 0;
331
332 out_destroy_stat:
333         while (i--)
334                 percpu_counter_destroy(&wb->stat[i]);
335         fprop_local_destroy_percpu(&wb->completions);
336 out_put_cong:
337         wb_congested_put(wb->congested);
338         return err;
339 }
340
341 /*
342  * Remove bdi from the global list and shutdown any threads we have running
343  */
344 static void wb_shutdown(struct bdi_writeback *wb)
345 {
346         /* Make sure nobody queues further work */
347         spin_lock_bh(&wb->work_lock);
348         if (!test_and_clear_bit(WB_registered, &wb->state)) {
349                 spin_unlock_bh(&wb->work_lock);
350                 return;
351         }
352         spin_unlock_bh(&wb->work_lock);
353
354         /*
355          * Drain work list and shutdown the delayed_work.  !WB_registered
356          * tells wb_workfn() that @wb is dying and its work_list needs to
357          * be drained no matter what.
358          */
359         mod_delayed_work(bdi_wq, &wb->dwork, 0);
360         flush_delayed_work(&wb->dwork);
361         WARN_ON(!list_empty(&wb->work_list));
362 }
363
364 static void wb_exit(struct bdi_writeback *wb)
365 {
366         int i;
367
368         WARN_ON(delayed_work_pending(&wb->dwork));
369
370         for (i = 0; i < NR_WB_STAT_ITEMS; i++)
371                 percpu_counter_destroy(&wb->stat[i]);
372
373         fprop_local_destroy_percpu(&wb->completions);
374         wb_congested_put(wb->congested);
375 }
376
377 #ifdef CONFIG_CGROUP_WRITEBACK
378
379 #include <linux/memcontrol.h>
380
381 /*
382  * cgwb_lock protects bdi->cgwb_tree, bdi->cgwb_congested_tree,
383  * blkcg->cgwb_list, and memcg->cgwb_list.  bdi->cgwb_tree is also RCU
384  * protected.  cgwb_release_wait is used to wait for the completion of cgwb
385  * releases from bdi destruction path.
386  */
387 static DEFINE_SPINLOCK(cgwb_lock);
388 static DECLARE_WAIT_QUEUE_HEAD(cgwb_release_wait);
389
390 /**
391  * wb_congested_get_create - get or create a wb_congested
392  * @bdi: associated bdi
393  * @blkcg_id: ID of the associated blkcg
394  * @gfp: allocation mask
395  *
396  * Look up the wb_congested for @blkcg_id on @bdi.  If missing, create one.
397  * The returned wb_congested has its reference count incremented.  Returns
398  * NULL on failure.
399  */
400 struct bdi_writeback_congested *
401 wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
402 {
403         struct bdi_writeback_congested *new_congested = NULL, *congested;
404         struct rb_node **node, *parent;
405         unsigned long flags;
406 retry:
407         spin_lock_irqsave(&cgwb_lock, flags);
408
409         node = &bdi->cgwb_congested_tree.rb_node;
410         parent = NULL;
411
412         while (*node != NULL) {
413                 parent = *node;
414                 congested = rb_entry(parent, struct bdi_writeback_congested,
415                                      rb_node);
416                 if (congested->blkcg_id < blkcg_id)
417                         node = &parent->rb_left;
418                 else if (congested->blkcg_id > blkcg_id)
419                         node = &parent->rb_right;
420                 else
421                         goto found;
422         }
423
424         if (new_congested) {
425                 /* !found and storage for new one already allocated, insert */
426                 congested = new_congested;
427                 new_congested = NULL;
428                 rb_link_node(&congested->rb_node, parent, node);
429                 rb_insert_color(&congested->rb_node, &bdi->cgwb_congested_tree);
430                 goto found;
431         }
432
433         spin_unlock_irqrestore(&cgwb_lock, flags);
434
435         /* allocate storage for new one and retry */
436         new_congested = kzalloc(sizeof(*new_congested), gfp);
437         if (!new_congested)
438                 return NULL;
439
440         atomic_set(&new_congested->refcnt, 0);
441         new_congested->bdi = bdi;
442         new_congested->blkcg_id = blkcg_id;
443         goto retry;
444
445 found:
446         atomic_inc(&congested->refcnt);
447         spin_unlock_irqrestore(&cgwb_lock, flags);
448         kfree(new_congested);
449         return congested;
450 }
451
452 /**
453  * wb_congested_put - put a wb_congested
454  * @congested: wb_congested to put
455  *
456  * Put @congested and destroy it if the refcnt reaches zero.
457  */
458 void wb_congested_put(struct bdi_writeback_congested *congested)
459 {
460         unsigned long flags;
461
462         local_irq_save(flags);
463         if (!atomic_dec_and_lock(&congested->refcnt, &cgwb_lock)) {
464                 local_irq_restore(flags);
465                 return;
466         }
467
468         /* bdi might already have been destroyed leaving @congested unlinked */
469         if (congested->bdi) {
470                 rb_erase(&congested->rb_node,
471                          &congested->bdi->cgwb_congested_tree);
472                 congested->bdi = NULL;
473         }
474
475         spin_unlock_irqrestore(&cgwb_lock, flags);
476         kfree(congested);
477 }
478
479 static void cgwb_release_workfn(struct work_struct *work)
480 {
481         struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
482                                                 release_work);
483         struct backing_dev_info *bdi = wb->bdi;
484
485         spin_lock_irq(&cgwb_lock);
486         list_del_rcu(&wb->bdi_node);
487         spin_unlock_irq(&cgwb_lock);
488
489         wb_shutdown(wb);
490
491         css_put(wb->memcg_css);
492         css_put(wb->blkcg_css);
493
494         fprop_local_destroy_percpu(&wb->memcg_completions);
495         percpu_ref_exit(&wb->refcnt);
496         wb_exit(wb);
497         kfree_rcu(wb, rcu);
498
499         if (atomic_dec_and_test(&bdi->usage_cnt))
500                 wake_up_all(&cgwb_release_wait);
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         schedule_work(&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 int cgwb_create(struct backing_dev_info *bdi,
521                        struct cgroup_subsys_state *memcg_css, gfp_t gfp)
522 {
523         struct mem_cgroup *memcg;
524         struct cgroup_subsys_state *blkcg_css;
525         struct blkcg *blkcg;
526         struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
527         struct bdi_writeback *wb;
528         unsigned long flags;
529         int ret = 0;
530
531         memcg = mem_cgroup_from_css(memcg_css);
532         blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
533         blkcg = css_to_blkcg(blkcg_css);
534         memcg_cgwb_list = mem_cgroup_cgwb_list(memcg);
535         blkcg_cgwb_list = &blkcg->cgwb_list;
536
537         /* look up again under lock and discard on blkcg mismatch */
538         spin_lock_irqsave(&cgwb_lock, flags);
539         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
540         if (wb && wb->blkcg_css != blkcg_css) {
541                 cgwb_kill(wb);
542                 wb = NULL;
543         }
544         spin_unlock_irqrestore(&cgwb_lock, flags);
545         if (wb)
546                 goto out_put;
547
548         /* need to create a new one */
549         wb = kmalloc(sizeof(*wb), gfp);
550         if (!wb)
551                 return -ENOMEM;
552
553         ret = wb_init(wb, bdi, blkcg_css->id, gfp);
554         if (ret)
555                 goto err_free;
556
557         ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
558         if (ret)
559                 goto err_wb_exit;
560
561         ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
562         if (ret)
563                 goto err_ref_exit;
564
565         wb->memcg_css = memcg_css;
566         wb->blkcg_css = blkcg_css;
567         INIT_WORK(&wb->release_work, cgwb_release_workfn);
568         set_bit(WB_registered, &wb->state);
569
570         /*
571          * The root wb determines the registered state of the whole bdi and
572          * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
573          * whether they're still online.  Don't link @wb if any is dead.
574          * See wb_memcg_offline() and wb_blkcg_offline().
575          */
576         ret = -ENODEV;
577         spin_lock_irqsave(&cgwb_lock, flags);
578         if (test_bit(WB_registered, &bdi->wb.state) &&
579             blkcg_cgwb_list->next && memcg_cgwb_list->next) {
580                 /* we might have raced another instance of this function */
581                 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
582                 if (!ret) {
583                         atomic_inc(&bdi->usage_cnt);
584                         list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
585                         list_add(&wb->memcg_node, memcg_cgwb_list);
586                         list_add(&wb->blkcg_node, blkcg_cgwb_list);
587                         css_get(memcg_css);
588                         css_get(blkcg_css);
589                 }
590         }
591         spin_unlock_irqrestore(&cgwb_lock, flags);
592         if (ret) {
593                 if (ret == -EEXIST)
594                         ret = 0;
595                 goto err_fprop_exit;
596         }
597         goto out_put;
598
599 err_fprop_exit:
600         fprop_local_destroy_percpu(&wb->memcg_completions);
601 err_ref_exit:
602         percpu_ref_exit(&wb->refcnt);
603 err_wb_exit:
604         wb_exit(wb);
605 err_free:
606         kfree(wb);
607 out_put:
608         css_put(blkcg_css);
609         return ret;
610 }
611
612 /**
613  * wb_get_create - get wb for a given memcg, create if necessary
614  * @bdi: target bdi
615  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
616  * @gfp: allocation mask to use
617  *
618  * Try to get the wb for @memcg_css on @bdi.  If it doesn't exist, try to
619  * create one.  The returned wb has its refcount incremented.
620  *
621  * This function uses css_get() on @memcg_css and thus expects its refcnt
622  * to be positive on invocation.  IOW, rcu_read_lock() protection on
623  * @memcg_css isn't enough.  try_get it before calling this function.
624  *
625  * A wb is keyed by its associated memcg.  As blkcg implicitly enables
626  * memcg on the default hierarchy, memcg association is guaranteed to be
627  * more specific (equal or descendant to the associated blkcg) and thus can
628  * identify both the memcg and blkcg associations.
629  *
630  * Because the blkcg associated with a memcg may change as blkcg is enabled
631  * and disabled closer to root in the hierarchy, each wb keeps track of
632  * both the memcg and blkcg associated with it and verifies the blkcg on
633  * each lookup.  On mismatch, the existing wb is discarded and a new one is
634  * created.
635  */
636 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
637                                     struct cgroup_subsys_state *memcg_css,
638                                     gfp_t gfp)
639 {
640         struct bdi_writeback *wb;
641
642         might_sleep_if(gfpflags_allow_blocking(gfp));
643
644         if (!memcg_css->parent)
645                 return &bdi->wb;
646
647         do {
648                 rcu_read_lock();
649                 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
650                 if (wb) {
651                         struct cgroup_subsys_state *blkcg_css;
652
653                         /* see whether the blkcg association has changed */
654                         blkcg_css = cgroup_get_e_css(memcg_css->cgroup,
655                                                      &io_cgrp_subsys);
656                         if (unlikely(wb->blkcg_css != blkcg_css ||
657                                      !wb_tryget(wb)))
658                                 wb = NULL;
659                         css_put(blkcg_css);
660                 }
661                 rcu_read_unlock();
662         } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
663
664         return wb;
665 }
666
667 static int cgwb_bdi_init(struct backing_dev_info *bdi)
668 {
669         int ret;
670
671         INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
672         bdi->cgwb_congested_tree = RB_ROOT;
673         atomic_set(&bdi->usage_cnt, 1);
674
675         ret = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
676         if (!ret) {
677                 bdi->wb.memcg_css = &root_mem_cgroup->css;
678                 bdi->wb.blkcg_css = blkcg_root_css;
679         }
680         return ret;
681 }
682
683 static void cgwb_bdi_destroy(struct backing_dev_info *bdi)
684 {
685         struct radix_tree_iter iter;
686         void **slot;
687
688         WARN_ON(test_bit(WB_registered, &bdi->wb.state));
689
690         spin_lock_irq(&cgwb_lock);
691         radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
692                 cgwb_kill(*slot);
693         spin_unlock_irq(&cgwb_lock);
694
695         /*
696          * All cgwb's must be shutdown and released before returning.  Drain
697          * the usage counter to wait for all cgwb's ever created on @bdi.
698          */
699         atomic_dec(&bdi->usage_cnt);
700         wait_event(cgwb_release_wait, !atomic_read(&bdi->usage_cnt));
701         /*
702          * Grab back our reference so that we hold it when @bdi gets
703          * re-registered.
704          */
705         atomic_inc(&bdi->usage_cnt);
706 }
707
708 /**
709  * wb_memcg_offline - kill all wb's associated with a memcg being offlined
710  * @memcg: memcg being offlined
711  *
712  * Also prevents creation of any new wb's associated with @memcg.
713  */
714 void wb_memcg_offline(struct mem_cgroup *memcg)
715 {
716         LIST_HEAD(to_destroy);
717         struct list_head *memcg_cgwb_list = mem_cgroup_cgwb_list(memcg);
718         struct bdi_writeback *wb, *next;
719
720         spin_lock_irq(&cgwb_lock);
721         list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
722                 cgwb_kill(wb);
723         memcg_cgwb_list->next = NULL;   /* prevent new wb's */
724         spin_unlock_irq(&cgwb_lock);
725 }
726
727 /**
728  * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
729  * @blkcg: blkcg being offlined
730  *
731  * Also prevents creation of any new wb's associated with @blkcg.
732  */
733 void wb_blkcg_offline(struct blkcg *blkcg)
734 {
735         LIST_HEAD(to_destroy);
736         struct bdi_writeback *wb, *next;
737
738         spin_lock_irq(&cgwb_lock);
739         list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node)
740                 cgwb_kill(wb);
741         blkcg->cgwb_list.next = NULL;   /* prevent new wb's */
742         spin_unlock_irq(&cgwb_lock);
743 }
744
745 static void cgwb_bdi_exit(struct backing_dev_info *bdi)
746 {
747         struct rb_node *rbn;
748
749         spin_lock_irq(&cgwb_lock);
750         while ((rbn = rb_first(&bdi->cgwb_congested_tree))) {
751                 struct bdi_writeback_congested *congested =
752                         rb_entry(rbn, struct bdi_writeback_congested, rb_node);
753
754                 rb_erase(rbn, &bdi->cgwb_congested_tree);
755                 congested->bdi = NULL;  /* mark @congested unlinked */
756         }
757         spin_unlock_irq(&cgwb_lock);
758 }
759
760 #else   /* CONFIG_CGROUP_WRITEBACK */
761
762 static int cgwb_bdi_init(struct backing_dev_info *bdi)
763 {
764         int err;
765
766         bdi->wb_congested = kzalloc(sizeof(*bdi->wb_congested), GFP_KERNEL);
767         if (!bdi->wb_congested)
768                 return -ENOMEM;
769
770         atomic_set(&bdi->wb_congested->refcnt, 1);
771
772         err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
773         if (err) {
774                 wb_congested_put(bdi->wb_congested);
775                 return err;
776         }
777         return 0;
778 }
779
780 static void cgwb_bdi_destroy(struct backing_dev_info *bdi) { }
781
782 static void cgwb_bdi_exit(struct backing_dev_info *bdi)
783 {
784         wb_congested_put(bdi->wb_congested);
785 }
786
787 #endif  /* CONFIG_CGROUP_WRITEBACK */
788
789 int bdi_init(struct backing_dev_info *bdi)
790 {
791         int ret;
792
793         bdi->dev = NULL;
794
795         kref_init(&bdi->refcnt);
796         bdi->min_ratio = 0;
797         bdi->max_ratio = 100;
798         bdi->max_prop_frac = FPROP_FRAC_BASE;
799         INIT_LIST_HEAD(&bdi->bdi_list);
800         INIT_LIST_HEAD(&bdi->wb_list);
801         init_waitqueue_head(&bdi->wb_waitq);
802
803         ret = cgwb_bdi_init(bdi);
804
805         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
806
807         return ret;
808 }
809 EXPORT_SYMBOL(bdi_init);
810
811 struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id)
812 {
813         struct backing_dev_info *bdi;
814
815         bdi = kmalloc_node(sizeof(struct backing_dev_info),
816                            gfp_mask | __GFP_ZERO, node_id);
817         if (!bdi)
818                 return NULL;
819
820         if (bdi_init(bdi)) {
821                 kfree(bdi);
822                 return NULL;
823         }
824         return bdi;
825 }
826
827 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
828                 const char *fmt, ...)
829 {
830         va_list args;
831         struct device *dev;
832
833         if (bdi->dev)   /* The driver needs to use separate queues per device */
834                 return 0;
835
836         va_start(args, fmt);
837         dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
838         va_end(args);
839         if (IS_ERR(dev))
840                 return PTR_ERR(dev);
841
842         bdi->dev = dev;
843
844         bdi_debug_register(bdi, dev_name(dev));
845         set_bit(WB_registered, &bdi->wb.state);
846
847         spin_lock_bh(&bdi_lock);
848         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
849         spin_unlock_bh(&bdi_lock);
850
851         trace_writeback_bdi_register(bdi);
852         return 0;
853 }
854 EXPORT_SYMBOL(bdi_register);
855
856 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
857 {
858         return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
859 }
860 EXPORT_SYMBOL(bdi_register_dev);
861
862 int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner)
863 {
864         int rc;
865
866         rc = bdi_register(bdi, NULL, "%u:%u", MAJOR(owner->devt),
867                         MINOR(owner->devt));
868         if (rc)
869                 return rc;
870         /* Leaking owner reference... */
871         WARN_ON(bdi->owner);
872         bdi->owner = owner;
873         get_device(owner);
874         return 0;
875 }
876 EXPORT_SYMBOL(bdi_register_owner);
877
878 /*
879  * Remove bdi from bdi_list, and ensure that it is no longer visible
880  */
881 static void bdi_remove_from_list(struct backing_dev_info *bdi)
882 {
883         spin_lock_bh(&bdi_lock);
884         list_del_rcu(&bdi->bdi_list);
885         spin_unlock_bh(&bdi_lock);
886
887         synchronize_rcu_expedited();
888 }
889
890 void bdi_unregister(struct backing_dev_info *bdi)
891 {
892         /* make sure nobody finds us on the bdi_list anymore */
893         bdi_remove_from_list(bdi);
894         wb_shutdown(&bdi->wb);
895         cgwb_bdi_destroy(bdi);
896
897         if (bdi->dev) {
898                 bdi_debug_unregister(bdi);
899                 device_unregister(bdi->dev);
900                 bdi->dev = NULL;
901         }
902
903         if (bdi->owner) {
904                 put_device(bdi->owner);
905                 bdi->owner = NULL;
906         }
907 }
908
909 static void bdi_exit(struct backing_dev_info *bdi)
910 {
911         WARN_ON_ONCE(bdi->dev);
912         wb_exit(&bdi->wb);
913         cgwb_bdi_exit(bdi);
914 }
915
916 static void release_bdi(struct kref *ref)
917 {
918         struct backing_dev_info *bdi =
919                         container_of(ref, struct backing_dev_info, refcnt);
920
921         bdi_exit(bdi);
922         kfree(bdi);
923 }
924
925 void bdi_put(struct backing_dev_info *bdi)
926 {
927         kref_put(&bdi->refcnt, release_bdi);
928 }
929
930 void bdi_destroy(struct backing_dev_info *bdi)
931 {
932         bdi_unregister(bdi);
933         bdi_exit(bdi);
934 }
935 EXPORT_SYMBOL(bdi_destroy);
936
937 /*
938  * For use from filesystems to quickly init and register a bdi associated
939  * with dirty writeback
940  */
941 int bdi_setup_and_register(struct backing_dev_info *bdi, char *name)
942 {
943         int err;
944
945         bdi->name = name;
946         bdi->capabilities = 0;
947         err = bdi_init(bdi);
948         if (err)
949                 return err;
950
951         err = bdi_register(bdi, NULL, "%.28s-%ld", name,
952                            atomic_long_inc_return(&bdi_seq));
953         if (err) {
954                 bdi_destroy(bdi);
955                 return err;
956         }
957
958         return 0;
959 }
960 EXPORT_SYMBOL(bdi_setup_and_register);
961
962 static wait_queue_head_t congestion_wqh[2] = {
963                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
964                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
965         };
966 static atomic_t nr_wb_congested[2];
967
968 void clear_wb_congested(struct bdi_writeback_congested *congested, int sync)
969 {
970         wait_queue_head_t *wqh = &congestion_wqh[sync];
971         enum wb_congested_state bit;
972
973         bit = sync ? WB_sync_congested : WB_async_congested;
974         if (test_and_clear_bit(bit, &congested->state))
975                 atomic_dec(&nr_wb_congested[sync]);
976         smp_mb__after_atomic();
977         if (waitqueue_active(wqh))
978                 wake_up(wqh);
979 }
980 EXPORT_SYMBOL(clear_wb_congested);
981
982 void set_wb_congested(struct bdi_writeback_congested *congested, int sync)
983 {
984         enum wb_congested_state bit;
985
986         bit = sync ? WB_sync_congested : WB_async_congested;
987         if (!test_and_set_bit(bit, &congested->state))
988                 atomic_inc(&nr_wb_congested[sync]);
989 }
990 EXPORT_SYMBOL(set_wb_congested);
991
992 /**
993  * congestion_wait - wait for a backing_dev to become uncongested
994  * @sync: SYNC or ASYNC IO
995  * @timeout: timeout in jiffies
996  *
997  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
998  * write congestion.  If no backing_devs are congested then just wait for the
999  * next write to be completed.
1000  */
1001 long congestion_wait(int sync, long timeout)
1002 {
1003         long ret;
1004         unsigned long start = jiffies;
1005         DEFINE_WAIT(wait);
1006         wait_queue_head_t *wqh = &congestion_wqh[sync];
1007
1008         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1009         ret = io_schedule_timeout(timeout);
1010         finish_wait(wqh, &wait);
1011
1012         trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
1013                                         jiffies_to_usecs(jiffies - start));
1014
1015         return ret;
1016 }
1017 EXPORT_SYMBOL(congestion_wait);
1018
1019 /**
1020  * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a pgdat to complete writes
1021  * @pgdat: A pgdat to check if it is heavily congested
1022  * @sync: SYNC or ASYNC IO
1023  * @timeout: timeout in jiffies
1024  *
1025  * In the event of a congested backing_dev (any backing_dev) and the given
1026  * @pgdat has experienced recent congestion, this waits for up to @timeout
1027  * jiffies for either a BDI to exit congestion of the given @sync queue
1028  * or a write to complete.
1029  *
1030  * In the absence of pgdat congestion, cond_resched() is called to yield
1031  * the processor if necessary but otherwise does not sleep.
1032  *
1033  * The return value is 0 if the sleep is for the full timeout. Otherwise,
1034  * it is the number of jiffies that were still remaining when the function
1035  * returned. return_value == timeout implies the function did not sleep.
1036  */
1037 long wait_iff_congested(struct pglist_data *pgdat, int sync, long timeout)
1038 {
1039         long ret;
1040         unsigned long start = jiffies;
1041         DEFINE_WAIT(wait);
1042         wait_queue_head_t *wqh = &congestion_wqh[sync];
1043
1044         /*
1045          * If there is no congestion, or heavy congestion is not being
1046          * encountered in the current pgdat, yield if necessary instead
1047          * of sleeping on the congestion queue
1048          */
1049         if (atomic_read(&nr_wb_congested[sync]) == 0 ||
1050             !test_bit(PGDAT_CONGESTED, &pgdat->flags)) {
1051                 cond_resched();
1052
1053                 /* In case we scheduled, work out time remaining */
1054                 ret = timeout - (jiffies - start);
1055                 if (ret < 0)
1056                         ret = 0;
1057
1058                 goto out;
1059         }
1060
1061         /* Sleep until uncongested or a write happens */
1062         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1063         ret = io_schedule_timeout(timeout);
1064         finish_wait(wqh, &wait);
1065
1066 out:
1067         trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
1068                                         jiffies_to_usecs(jiffies - start));
1069
1070         return ret;
1071 }
1072 EXPORT_SYMBOL(wait_iff_congested);
1073
1074 int pdflush_proc_obsolete(struct ctl_table *table, int write,
1075                         void __user *buffer, size_t *lenp, loff_t *ppos)
1076 {
1077         char kbuf[] = "0\n";
1078
1079         if (*ppos || *lenp < sizeof(kbuf)) {
1080                 *lenp = 0;
1081                 return 0;
1082         }
1083
1084         if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
1085                 return -EFAULT;
1086         pr_warn_once("%s exported in /proc is scheduled for removal\n",
1087                      table->procname);
1088
1089         *lenp = 2;
1090         *ppos += *lenp;
1091         return 2;
1092 }