bdi: wake up concurrent wb_shutdown() callers.
[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 struct backing_dev_info noop_backing_dev_info = {
16         .name           = "noop",
17         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
18 };
19 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
20
21 static struct class *bdi_class;
22
23 /*
24  * bdi_lock protects updates to bdi_list. bdi_list has RCU reader side
25  * locking.
26  */
27 DEFINE_SPINLOCK(bdi_lock);
28 LIST_HEAD(bdi_list);
29
30 /* bdi_wq serves all asynchronous writeback tasks */
31 struct workqueue_struct *bdi_wq;
32
33 #ifdef CONFIG_DEBUG_FS
34 #include <linux/debugfs.h>
35 #include <linux/seq_file.h>
36
37 static struct dentry *bdi_debug_root;
38
39 static void bdi_debug_init(void)
40 {
41         bdi_debug_root = debugfs_create_dir("bdi", NULL);
42 }
43
44 static int bdi_debug_stats_show(struct seq_file *m, void *v)
45 {
46         struct backing_dev_info *bdi = m->private;
47         struct bdi_writeback *wb = &bdi->wb;
48         unsigned long background_thresh;
49         unsigned long dirty_thresh;
50         unsigned long wb_thresh;
51         unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
52         struct inode *inode;
53
54         nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
55         spin_lock(&wb->list_lock);
56         list_for_each_entry(inode, &wb->b_dirty, i_io_list)
57                 nr_dirty++;
58         list_for_each_entry(inode, &wb->b_io, i_io_list)
59                 nr_io++;
60         list_for_each_entry(inode, &wb->b_more_io, i_io_list)
61                 nr_more_io++;
62         list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
63                 if (inode->i_state & I_DIRTY_TIME)
64                         nr_dirty_time++;
65         spin_unlock(&wb->list_lock);
66
67         global_dirty_limits(&background_thresh, &dirty_thresh);
68         wb_thresh = wb_calc_thresh(wb, dirty_thresh);
69
70 #define K(x) ((x) << (PAGE_SHIFT - 10))
71         seq_printf(m,
72                    "BdiWriteback:       %10lu kB\n"
73                    "BdiReclaimable:     %10lu kB\n"
74                    "BdiDirtyThresh:     %10lu kB\n"
75                    "DirtyThresh:        %10lu kB\n"
76                    "BackgroundThresh:   %10lu kB\n"
77                    "BdiDirtied:         %10lu kB\n"
78                    "BdiWritten:         %10lu kB\n"
79                    "BdiWriteBandwidth:  %10lu kBps\n"
80                    "b_dirty:            %10lu\n"
81                    "b_io:               %10lu\n"
82                    "b_more_io:          %10lu\n"
83                    "b_dirty_time:       %10lu\n"
84                    "bdi_list:           %10u\n"
85                    "state:              %10lx\n",
86                    (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
87                    (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
88                    K(wb_thresh),
89                    K(dirty_thresh),
90                    K(background_thresh),
91                    (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
92                    (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
93                    (unsigned long) K(wb->write_bandwidth),
94                    nr_dirty,
95                    nr_io,
96                    nr_more_io,
97                    nr_dirty_time,
98                    !list_empty(&bdi->bdi_list), bdi->wb.state);
99 #undef K
100
101         return 0;
102 }
103 DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
104
105 static int bdi_debug_register(struct backing_dev_info *bdi, const char *name)
106 {
107         if (!bdi_debug_root)
108                 return -ENOMEM;
109
110         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
111         if (!bdi->debug_dir)
112                 return -ENOMEM;
113
114         bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
115                                                bdi, &bdi_debug_stats_fops);
116         if (!bdi->debug_stats) {
117                 debugfs_remove(bdi->debug_dir);
118                 return -ENOMEM;
119         }
120
121         return 0;
122 }
123
124 static void bdi_debug_unregister(struct backing_dev_info *bdi)
125 {
126         debugfs_remove(bdi->debug_stats);
127         debugfs_remove(bdi->debug_dir);
128 }
129 #else
130 static inline void bdi_debug_init(void)
131 {
132 }
133 static inline int bdi_debug_register(struct backing_dev_info *bdi,
134                                       const char *name)
135 {
136         return 0;
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 bdi_init(struct backing_dev_info *bdi);
246
247 static int __init default_bdi_init(void)
248 {
249         int err;
250
251         bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE |
252                                               WQ_UNBOUND | WQ_SYSFS, 0);
253         if (!bdi_wq)
254                 return -ENOMEM;
255
256         err = bdi_init(&noop_backing_dev_info);
257
258         return err;
259 }
260 subsys_initcall(default_bdi_init);
261
262 /*
263  * This function is used when the first inode for this wb is marked dirty. It
264  * wakes-up the corresponding bdi thread which should then take care of the
265  * periodic background write-out of dirty inodes. Since the write-out would
266  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
267  * set up a timer which wakes the bdi thread up later.
268  *
269  * Note, we wouldn't bother setting up the timer, but this function is on the
270  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
271  * by delaying the wake-up.
272  *
273  * We have to be careful not to postpone flush work if it is scheduled for
274  * earlier. Thus we use queue_delayed_work().
275  */
276 void wb_wakeup_delayed(struct bdi_writeback *wb)
277 {
278         unsigned long timeout;
279
280         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
281         spin_lock_bh(&wb->work_lock);
282         if (test_bit(WB_registered, &wb->state))
283                 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
284         spin_unlock_bh(&wb->work_lock);
285 }
286
287 /*
288  * Initial write bandwidth: 100 MB/s
289  */
290 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
291
292 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
293                    int blkcg_id, gfp_t gfp)
294 {
295         int i, err;
296
297         memset(wb, 0, sizeof(*wb));
298
299         if (wb != &bdi->wb)
300                 bdi_get(bdi);
301         wb->bdi = bdi;
302         wb->last_old_flush = jiffies;
303         INIT_LIST_HEAD(&wb->b_dirty);
304         INIT_LIST_HEAD(&wb->b_io);
305         INIT_LIST_HEAD(&wb->b_more_io);
306         INIT_LIST_HEAD(&wb->b_dirty_time);
307         spin_lock_init(&wb->list_lock);
308
309         wb->bw_time_stamp = jiffies;
310         wb->balanced_dirty_ratelimit = INIT_BW;
311         wb->dirty_ratelimit = INIT_BW;
312         wb->write_bandwidth = INIT_BW;
313         wb->avg_write_bandwidth = INIT_BW;
314
315         spin_lock_init(&wb->work_lock);
316         INIT_LIST_HEAD(&wb->work_list);
317         INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
318         wb->dirty_sleep = jiffies;
319
320         wb->congested = wb_congested_get_create(bdi, blkcg_id, gfp);
321         if (!wb->congested) {
322                 err = -ENOMEM;
323                 goto out_put_bdi;
324         }
325
326         err = fprop_local_init_percpu(&wb->completions, gfp);
327         if (err)
328                 goto out_put_cong;
329
330         for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
331                 err = percpu_counter_init(&wb->stat[i], 0, gfp);
332                 if (err)
333                         goto out_destroy_stat;
334         }
335
336         return 0;
337
338 out_destroy_stat:
339         while (i--)
340                 percpu_counter_destroy(&wb->stat[i]);
341         fprop_local_destroy_percpu(&wb->completions);
342 out_put_cong:
343         wb_congested_put(wb->congested);
344 out_put_bdi:
345         if (wb != &bdi->wb)
346                 bdi_put(bdi);
347         return err;
348 }
349
350 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
351
352 /*
353  * Remove bdi from the global list and shutdown any threads we have running
354  */
355 static void wb_shutdown(struct bdi_writeback *wb)
356 {
357         /* Make sure nobody queues further work */
358         spin_lock_bh(&wb->work_lock);
359         if (!test_and_clear_bit(WB_registered, &wb->state)) {
360                 spin_unlock_bh(&wb->work_lock);
361                 /*
362                  * Wait for wb shutdown to finish if someone else is just
363                  * running wb_shutdown(). Otherwise we could proceed to wb /
364                  * bdi destruction before wb_shutdown() is finished.
365                  */
366                 wait_on_bit(&wb->state, WB_shutting_down, TASK_UNINTERRUPTIBLE);
367                 return;
368         }
369         set_bit(WB_shutting_down, &wb->state);
370         spin_unlock_bh(&wb->work_lock);
371
372         cgwb_remove_from_bdi_list(wb);
373         /*
374          * Drain work list and shutdown the delayed_work.  !WB_registered
375          * tells wb_workfn() that @wb is dying and its work_list needs to
376          * be drained no matter what.
377          */
378         mod_delayed_work(bdi_wq, &wb->dwork, 0);
379         flush_delayed_work(&wb->dwork);
380         WARN_ON(!list_empty(&wb->work_list));
381         /*
382          * Make sure bit gets cleared after shutdown is finished. Matches with
383          * the barrier provided by test_and_clear_bit() above.
384          */
385         smp_wmb();
386         clear_and_wake_up_bit(WB_shutting_down, &wb->state);
387 }
388
389 static void wb_exit(struct bdi_writeback *wb)
390 {
391         int i;
392
393         WARN_ON(delayed_work_pending(&wb->dwork));
394
395         for (i = 0; i < NR_WB_STAT_ITEMS; i++)
396                 percpu_counter_destroy(&wb->stat[i]);
397
398         fprop_local_destroy_percpu(&wb->completions);
399         wb_congested_put(wb->congested);
400         if (wb != &wb->bdi->wb)
401                 bdi_put(wb->bdi);
402 }
403
404 #ifdef CONFIG_CGROUP_WRITEBACK
405
406 #include <linux/memcontrol.h>
407
408 /*
409  * cgwb_lock protects bdi->cgwb_tree, bdi->cgwb_congested_tree,
410  * blkcg->cgwb_list, and memcg->cgwb_list.  bdi->cgwb_tree is also RCU
411  * protected.
412  */
413 static DEFINE_SPINLOCK(cgwb_lock);
414
415 /**
416  * wb_congested_get_create - get or create a wb_congested
417  * @bdi: associated bdi
418  * @blkcg_id: ID of the associated blkcg
419  * @gfp: allocation mask
420  *
421  * Look up the wb_congested for @blkcg_id on @bdi.  If missing, create one.
422  * The returned wb_congested has its reference count incremented.  Returns
423  * NULL on failure.
424  */
425 struct bdi_writeback_congested *
426 wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
427 {
428         struct bdi_writeback_congested *new_congested = NULL, *congested;
429         struct rb_node **node, *parent;
430         unsigned long flags;
431 retry:
432         spin_lock_irqsave(&cgwb_lock, flags);
433
434         node = &bdi->cgwb_congested_tree.rb_node;
435         parent = NULL;
436
437         while (*node != NULL) {
438                 parent = *node;
439                 congested = rb_entry(parent, struct bdi_writeback_congested,
440                                      rb_node);
441                 if (congested->blkcg_id < blkcg_id)
442                         node = &parent->rb_left;
443                 else if (congested->blkcg_id > blkcg_id)
444                         node = &parent->rb_right;
445                 else
446                         goto found;
447         }
448
449         if (new_congested) {
450                 /* !found and storage for new one already allocated, insert */
451                 congested = new_congested;
452                 new_congested = NULL;
453                 rb_link_node(&congested->rb_node, parent, node);
454                 rb_insert_color(&congested->rb_node, &bdi->cgwb_congested_tree);
455                 goto found;
456         }
457
458         spin_unlock_irqrestore(&cgwb_lock, flags);
459
460         /* allocate storage for new one and retry */
461         new_congested = kzalloc(sizeof(*new_congested), gfp);
462         if (!new_congested)
463                 return NULL;
464
465         atomic_set(&new_congested->refcnt, 0);
466         new_congested->__bdi = bdi;
467         new_congested->blkcg_id = blkcg_id;
468         goto retry;
469
470 found:
471         atomic_inc(&congested->refcnt);
472         spin_unlock_irqrestore(&cgwb_lock, flags);
473         kfree(new_congested);
474         return congested;
475 }
476
477 /**
478  * wb_congested_put - put a wb_congested
479  * @congested: wb_congested to put
480  *
481  * Put @congested and destroy it if the refcnt reaches zero.
482  */
483 void wb_congested_put(struct bdi_writeback_congested *congested)
484 {
485         unsigned long flags;
486
487         local_irq_save(flags);
488         if (!atomic_dec_and_lock(&congested->refcnt, &cgwb_lock)) {
489                 local_irq_restore(flags);
490                 return;
491         }
492
493         /* bdi might already have been destroyed leaving @congested unlinked */
494         if (congested->__bdi) {
495                 rb_erase(&congested->rb_node,
496                          &congested->__bdi->cgwb_congested_tree);
497                 congested->__bdi = NULL;
498         }
499
500         spin_unlock_irqrestore(&cgwb_lock, flags);
501         kfree(congested);
502 }
503
504 static void cgwb_release_workfn(struct work_struct *work)
505 {
506         struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
507                                                 release_work);
508
509         wb_shutdown(wb);
510
511         css_put(wb->memcg_css);
512         css_put(wb->blkcg_css);
513
514         fprop_local_destroy_percpu(&wb->memcg_completions);
515         percpu_ref_exit(&wb->refcnt);
516         wb_exit(wb);
517         kfree_rcu(wb, rcu);
518 }
519
520 static void cgwb_release(struct percpu_ref *refcnt)
521 {
522         struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
523                                                 refcnt);
524         schedule_work(&wb->release_work);
525 }
526
527 static void cgwb_kill(struct bdi_writeback *wb)
528 {
529         lockdep_assert_held(&cgwb_lock);
530
531         WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
532         list_del(&wb->memcg_node);
533         list_del(&wb->blkcg_node);
534         percpu_ref_kill(&wb->refcnt);
535 }
536
537 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
538 {
539         spin_lock_irq(&cgwb_lock);
540         list_del_rcu(&wb->bdi_node);
541         spin_unlock_irq(&cgwb_lock);
542 }
543
544 static int cgwb_create(struct backing_dev_info *bdi,
545                        struct cgroup_subsys_state *memcg_css, gfp_t gfp)
546 {
547         struct mem_cgroup *memcg;
548         struct cgroup_subsys_state *blkcg_css;
549         struct blkcg *blkcg;
550         struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
551         struct bdi_writeback *wb;
552         unsigned long flags;
553         int ret = 0;
554
555         memcg = mem_cgroup_from_css(memcg_css);
556         blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
557         blkcg = css_to_blkcg(blkcg_css);
558         memcg_cgwb_list = mem_cgroup_cgwb_list(memcg);
559         blkcg_cgwb_list = &blkcg->cgwb_list;
560
561         /* look up again under lock and discard on blkcg mismatch */
562         spin_lock_irqsave(&cgwb_lock, flags);
563         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
564         if (wb && wb->blkcg_css != blkcg_css) {
565                 cgwb_kill(wb);
566                 wb = NULL;
567         }
568         spin_unlock_irqrestore(&cgwb_lock, flags);
569         if (wb)
570                 goto out_put;
571
572         /* need to create a new one */
573         wb = kmalloc(sizeof(*wb), gfp);
574         if (!wb) {
575                 ret = -ENOMEM;
576                 goto out_put;
577         }
578
579         ret = wb_init(wb, bdi, blkcg_css->id, gfp);
580         if (ret)
581                 goto err_free;
582
583         ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
584         if (ret)
585                 goto err_wb_exit;
586
587         ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
588         if (ret)
589                 goto err_ref_exit;
590
591         wb->memcg_css = memcg_css;
592         wb->blkcg_css = blkcg_css;
593         INIT_WORK(&wb->release_work, cgwb_release_workfn);
594         set_bit(WB_registered, &wb->state);
595
596         /*
597          * The root wb determines the registered state of the whole bdi and
598          * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
599          * whether they're still online.  Don't link @wb if any is dead.
600          * See wb_memcg_offline() and wb_blkcg_offline().
601          */
602         ret = -ENODEV;
603         spin_lock_irqsave(&cgwb_lock, flags);
604         if (test_bit(WB_registered, &bdi->wb.state) &&
605             blkcg_cgwb_list->next && memcg_cgwb_list->next) {
606                 /* we might have raced another instance of this function */
607                 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
608                 if (!ret) {
609                         list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
610                         list_add(&wb->memcg_node, memcg_cgwb_list);
611                         list_add(&wb->blkcg_node, blkcg_cgwb_list);
612                         css_get(memcg_css);
613                         css_get(blkcg_css);
614                 }
615         }
616         spin_unlock_irqrestore(&cgwb_lock, flags);
617         if (ret) {
618                 if (ret == -EEXIST)
619                         ret = 0;
620                 goto err_fprop_exit;
621         }
622         goto out_put;
623
624 err_fprop_exit:
625         fprop_local_destroy_percpu(&wb->memcg_completions);
626 err_ref_exit:
627         percpu_ref_exit(&wb->refcnt);
628 err_wb_exit:
629         wb_exit(wb);
630 err_free:
631         kfree(wb);
632 out_put:
633         css_put(blkcg_css);
634         return ret;
635 }
636
637 /**
638  * wb_get_create - get wb for a given memcg, create if necessary
639  * @bdi: target bdi
640  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
641  * @gfp: allocation mask to use
642  *
643  * Try to get the wb for @memcg_css on @bdi.  If it doesn't exist, try to
644  * create one.  The returned wb has its refcount incremented.
645  *
646  * This function uses css_get() on @memcg_css and thus expects its refcnt
647  * to be positive on invocation.  IOW, rcu_read_lock() protection on
648  * @memcg_css isn't enough.  try_get it before calling this function.
649  *
650  * A wb is keyed by its associated memcg.  As blkcg implicitly enables
651  * memcg on the default hierarchy, memcg association is guaranteed to be
652  * more specific (equal or descendant to the associated blkcg) and thus can
653  * identify both the memcg and blkcg associations.
654  *
655  * Because the blkcg associated with a memcg may change as blkcg is enabled
656  * and disabled closer to root in the hierarchy, each wb keeps track of
657  * both the memcg and blkcg associated with it and verifies the blkcg on
658  * each lookup.  On mismatch, the existing wb is discarded and a new one is
659  * created.
660  */
661 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
662                                     struct cgroup_subsys_state *memcg_css,
663                                     gfp_t gfp)
664 {
665         struct bdi_writeback *wb;
666
667         might_sleep_if(gfpflags_allow_blocking(gfp));
668
669         if (!memcg_css->parent)
670                 return &bdi->wb;
671
672         do {
673                 rcu_read_lock();
674                 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
675                 if (wb) {
676                         struct cgroup_subsys_state *blkcg_css;
677
678                         /* see whether the blkcg association has changed */
679                         blkcg_css = cgroup_get_e_css(memcg_css->cgroup,
680                                                      &io_cgrp_subsys);
681                         if (unlikely(wb->blkcg_css != blkcg_css ||
682                                      !wb_tryget(wb)))
683                                 wb = NULL;
684                         css_put(blkcg_css);
685                 }
686                 rcu_read_unlock();
687         } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
688
689         return wb;
690 }
691
692 static int cgwb_bdi_init(struct backing_dev_info *bdi)
693 {
694         int ret;
695
696         INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
697         bdi->cgwb_congested_tree = RB_ROOT;
698
699         ret = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
700         if (!ret) {
701                 bdi->wb.memcg_css = &root_mem_cgroup->css;
702                 bdi->wb.blkcg_css = blkcg_root_css;
703         }
704         return ret;
705 }
706
707 static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
708 {
709         struct radix_tree_iter iter;
710         void **slot;
711         struct bdi_writeback *wb;
712
713         WARN_ON(test_bit(WB_registered, &bdi->wb.state));
714
715         spin_lock_irq(&cgwb_lock);
716         radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
717                 cgwb_kill(*slot);
718
719         while (!list_empty(&bdi->wb_list)) {
720                 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
721                                       bdi_node);
722                 spin_unlock_irq(&cgwb_lock);
723                 wb_shutdown(wb);
724                 spin_lock_irq(&cgwb_lock);
725         }
726         spin_unlock_irq(&cgwb_lock);
727 }
728
729 /**
730  * wb_memcg_offline - kill all wb's associated with a memcg being offlined
731  * @memcg: memcg being offlined
732  *
733  * Also prevents creation of any new wb's associated with @memcg.
734  */
735 void wb_memcg_offline(struct mem_cgroup *memcg)
736 {
737         struct list_head *memcg_cgwb_list = mem_cgroup_cgwb_list(memcg);
738         struct bdi_writeback *wb, *next;
739
740         spin_lock_irq(&cgwb_lock);
741         list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
742                 cgwb_kill(wb);
743         memcg_cgwb_list->next = NULL;   /* prevent new wb's */
744         spin_unlock_irq(&cgwb_lock);
745 }
746
747 /**
748  * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
749  * @blkcg: blkcg being offlined
750  *
751  * Also prevents creation of any new wb's associated with @blkcg.
752  */
753 void wb_blkcg_offline(struct blkcg *blkcg)
754 {
755         struct bdi_writeback *wb, *next;
756
757         spin_lock_irq(&cgwb_lock);
758         list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node)
759                 cgwb_kill(wb);
760         blkcg->cgwb_list.next = NULL;   /* prevent new wb's */
761         spin_unlock_irq(&cgwb_lock);
762 }
763
764 static void cgwb_bdi_exit(struct backing_dev_info *bdi)
765 {
766         struct rb_node *rbn;
767
768         spin_lock_irq(&cgwb_lock);
769         while ((rbn = rb_first(&bdi->cgwb_congested_tree))) {
770                 struct bdi_writeback_congested *congested =
771                         rb_entry(rbn, struct bdi_writeback_congested, rb_node);
772
773                 rb_erase(rbn, &bdi->cgwb_congested_tree);
774                 congested->__bdi = NULL;        /* mark @congested unlinked */
775         }
776         spin_unlock_irq(&cgwb_lock);
777 }
778
779 static void cgwb_bdi_register(struct backing_dev_info *bdi)
780 {
781         spin_lock_irq(&cgwb_lock);
782         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
783         spin_unlock_irq(&cgwb_lock);
784 }
785
786 #else   /* CONFIG_CGROUP_WRITEBACK */
787
788 static int cgwb_bdi_init(struct backing_dev_info *bdi)
789 {
790         int err;
791
792         bdi->wb_congested = kzalloc(sizeof(*bdi->wb_congested), GFP_KERNEL);
793         if (!bdi->wb_congested)
794                 return -ENOMEM;
795
796         atomic_set(&bdi->wb_congested->refcnt, 1);
797
798         err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
799         if (err) {
800                 wb_congested_put(bdi->wb_congested);
801                 return err;
802         }
803         return 0;
804 }
805
806 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
807
808 static void cgwb_bdi_exit(struct backing_dev_info *bdi)
809 {
810         wb_congested_put(bdi->wb_congested);
811 }
812
813 static void cgwb_bdi_register(struct backing_dev_info *bdi)
814 {
815         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
816 }
817
818 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
819 {
820         list_del_rcu(&wb->bdi_node);
821 }
822
823 #endif  /* CONFIG_CGROUP_WRITEBACK */
824
825 static int bdi_init(struct backing_dev_info *bdi)
826 {
827         int ret;
828
829         bdi->dev = NULL;
830
831         kref_init(&bdi->refcnt);
832         bdi->min_ratio = 0;
833         bdi->max_ratio = 100;
834         bdi->max_prop_frac = FPROP_FRAC_BASE;
835         INIT_LIST_HEAD(&bdi->bdi_list);
836         INIT_LIST_HEAD(&bdi->wb_list);
837         init_waitqueue_head(&bdi->wb_waitq);
838
839         ret = cgwb_bdi_init(bdi);
840
841         return ret;
842 }
843
844 struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id)
845 {
846         struct backing_dev_info *bdi;
847
848         bdi = kmalloc_node(sizeof(struct backing_dev_info),
849                            gfp_mask | __GFP_ZERO, node_id);
850         if (!bdi)
851                 return NULL;
852
853         if (bdi_init(bdi)) {
854                 kfree(bdi);
855                 return NULL;
856         }
857         return bdi;
858 }
859 EXPORT_SYMBOL(bdi_alloc_node);
860
861 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
862 {
863         struct device *dev;
864
865         if (bdi->dev)   /* The driver needs to use separate queues per device */
866                 return 0;
867
868         dev = device_create_vargs(bdi_class, NULL, MKDEV(0, 0), bdi, fmt, args);
869         if (IS_ERR(dev))
870                 return PTR_ERR(dev);
871
872         cgwb_bdi_register(bdi);
873         bdi->dev = dev;
874
875         bdi_debug_register(bdi, dev_name(dev));
876         set_bit(WB_registered, &bdi->wb.state);
877
878         spin_lock_bh(&bdi_lock);
879         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
880         spin_unlock_bh(&bdi_lock);
881
882         trace_writeback_bdi_register(bdi);
883         return 0;
884 }
885 EXPORT_SYMBOL(bdi_register_va);
886
887 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
888 {
889         va_list args;
890         int ret;
891
892         va_start(args, fmt);
893         ret = bdi_register_va(bdi, fmt, args);
894         va_end(args);
895         return ret;
896 }
897 EXPORT_SYMBOL(bdi_register);
898
899 int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner)
900 {
901         int rc;
902
903         rc = bdi_register(bdi, "%u:%u", MAJOR(owner->devt), MINOR(owner->devt));
904         if (rc)
905                 return rc;
906         /* Leaking owner reference... */
907         WARN_ON(bdi->owner);
908         bdi->owner = owner;
909         get_device(owner);
910         return 0;
911 }
912 EXPORT_SYMBOL(bdi_register_owner);
913
914 /*
915  * Remove bdi from bdi_list, and ensure that it is no longer visible
916  */
917 static void bdi_remove_from_list(struct backing_dev_info *bdi)
918 {
919         spin_lock_bh(&bdi_lock);
920         list_del_rcu(&bdi->bdi_list);
921         spin_unlock_bh(&bdi_lock);
922
923         synchronize_rcu_expedited();
924 }
925
926 void bdi_unregister(struct backing_dev_info *bdi)
927 {
928         /* make sure nobody finds us on the bdi_list anymore */
929         bdi_remove_from_list(bdi);
930         wb_shutdown(&bdi->wb);
931         cgwb_bdi_unregister(bdi);
932
933         if (bdi->dev) {
934                 bdi_debug_unregister(bdi);
935                 device_unregister(bdi->dev);
936                 bdi->dev = NULL;
937         }
938
939         if (bdi->owner) {
940                 put_device(bdi->owner);
941                 bdi->owner = NULL;
942         }
943 }
944
945 static void release_bdi(struct kref *ref)
946 {
947         struct backing_dev_info *bdi =
948                         container_of(ref, struct backing_dev_info, refcnt);
949
950         if (test_bit(WB_registered, &bdi->wb.state))
951                 bdi_unregister(bdi);
952         WARN_ON_ONCE(bdi->dev);
953         wb_exit(&bdi->wb);
954         cgwb_bdi_exit(bdi);
955         kfree(bdi);
956 }
957
958 void bdi_put(struct backing_dev_info *bdi)
959 {
960         kref_put(&bdi->refcnt, release_bdi);
961 }
962 EXPORT_SYMBOL(bdi_put);
963
964 static wait_queue_head_t congestion_wqh[2] = {
965                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
966                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
967         };
968 static atomic_t nr_wb_congested[2];
969
970 void clear_wb_congested(struct bdi_writeback_congested *congested, int sync)
971 {
972         wait_queue_head_t *wqh = &congestion_wqh[sync];
973         enum wb_congested_state bit;
974
975         bit = sync ? WB_sync_congested : WB_async_congested;
976         if (test_and_clear_bit(bit, &congested->state))
977                 atomic_dec(&nr_wb_congested[sync]);
978         smp_mb__after_atomic();
979         if (waitqueue_active(wqh))
980                 wake_up(wqh);
981 }
982 EXPORT_SYMBOL(clear_wb_congested);
983
984 void set_wb_congested(struct bdi_writeback_congested *congested, int sync)
985 {
986         enum wb_congested_state bit;
987
988         bit = sync ? WB_sync_congested : WB_async_congested;
989         if (!test_and_set_bit(bit, &congested->state))
990                 atomic_inc(&nr_wb_congested[sync]);
991 }
992 EXPORT_SYMBOL(set_wb_congested);
993
994 /**
995  * congestion_wait - wait for a backing_dev to become uncongested
996  * @sync: SYNC or ASYNC IO
997  * @timeout: timeout in jiffies
998  *
999  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
1000  * write congestion.  If no backing_devs are congested then just wait for the
1001  * next write to be completed.
1002  */
1003 long congestion_wait(int sync, long timeout)
1004 {
1005         long ret;
1006         unsigned long start = jiffies;
1007         DEFINE_WAIT(wait);
1008         wait_queue_head_t *wqh = &congestion_wqh[sync];
1009
1010         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1011         ret = io_schedule_timeout(timeout);
1012         finish_wait(wqh, &wait);
1013
1014         trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
1015                                         jiffies_to_usecs(jiffies - start));
1016
1017         return ret;
1018 }
1019 EXPORT_SYMBOL(congestion_wait);
1020
1021 /**
1022  * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a pgdat to complete writes
1023  * @sync: SYNC or ASYNC IO
1024  * @timeout: timeout in jiffies
1025  *
1026  * In the event of a congested backing_dev (any backing_dev) this waits
1027  * for up to @timeout jiffies for either a BDI to exit congestion of the
1028  * given @sync queue or a write to complete.
1029  *
1030  * The return value is 0 if the sleep is for the full timeout. Otherwise,
1031  * it is the number of jiffies that were still remaining when the function
1032  * returned. return_value == timeout implies the function did not sleep.
1033  */
1034 long wait_iff_congested(int sync, long timeout)
1035 {
1036         long ret;
1037         unsigned long start = jiffies;
1038         DEFINE_WAIT(wait);
1039         wait_queue_head_t *wqh = &congestion_wqh[sync];
1040
1041         /*
1042          * If there is no congestion, yield if necessary instead
1043          * of sleeping on the congestion queue
1044          */
1045         if (atomic_read(&nr_wb_congested[sync]) == 0) {
1046                 cond_resched();
1047
1048                 /* In case we scheduled, work out time remaining */
1049                 ret = timeout - (jiffies - start);
1050                 if (ret < 0)
1051                         ret = 0;
1052
1053                 goto out;
1054         }
1055
1056         /* Sleep until uncongested or a write happens */
1057         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1058         ret = io_schedule_timeout(timeout);
1059         finish_wait(wqh, &wait);
1060
1061 out:
1062         trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
1063                                         jiffies_to_usecs(jiffies - start));
1064
1065         return ret;
1066 }
1067 EXPORT_SYMBOL(wait_iff_congested);