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Merge tag 'io_uring-5.7-2020-05-22' of git://git.kernel.dk/linux-block
[thirdparty/linux.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 static const char *bdi_unknown_name = "(unknown)";
25
26 /*
27 * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
28 * reader side locking.
29 */
30 DEFINE_SPINLOCK(bdi_lock);
31 static u64 bdi_id_cursor;
32 static struct rb_root bdi_tree = RB_ROOT;
33 LIST_HEAD(bdi_list);
34
35 /* bdi_wq serves all asynchronous writeback tasks */
36 struct workqueue_struct *bdi_wq;
37
38 #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 no online users left */
495 blkcg_unpin_online(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_pin_online(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 vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
942 dev = device_create(bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
943 if (IS_ERR(dev))
944 return PTR_ERR(dev);
945
946 cgwb_bdi_register(bdi);
947 bdi->dev = dev;
948
949 bdi_debug_register(bdi, dev_name(dev));
950 set_bit(WB_registered, &bdi->wb.state);
951
952 spin_lock_bh(&bdi_lock);
953
954 bdi->id = ++bdi_id_cursor;
955
956 p = bdi_lookup_rb_node(bdi->id, &parent);
957 rb_link_node(&bdi->rb_node, parent, p);
958 rb_insert_color(&bdi->rb_node, &bdi_tree);
959
960 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
961
962 spin_unlock_bh(&bdi_lock);
963
964 trace_writeback_bdi_register(bdi);
965 return 0;
966 }
967 EXPORT_SYMBOL(bdi_register_va);
968
969 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
970 {
971 va_list args;
972 int ret;
973
974 va_start(args, fmt);
975 ret = bdi_register_va(bdi, fmt, args);
976 va_end(args);
977 return ret;
978 }
979 EXPORT_SYMBOL(bdi_register);
980
981 int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner)
982 {
983 int rc;
984
985 rc = bdi_register(bdi, "%u:%u", MAJOR(owner->devt), MINOR(owner->devt));
986 if (rc)
987 return rc;
988 /* Leaking owner reference... */
989 WARN_ON(bdi->owner);
990 bdi->owner = owner;
991 get_device(owner);
992 return 0;
993 }
994 EXPORT_SYMBOL(bdi_register_owner);
995
996 /*
997 * Remove bdi from bdi_list, and ensure that it is no longer visible
998 */
999 static void bdi_remove_from_list(struct backing_dev_info *bdi)
1000 {
1001 spin_lock_bh(&bdi_lock);
1002 rb_erase(&bdi->rb_node, &bdi_tree);
1003 list_del_rcu(&bdi->bdi_list);
1004 spin_unlock_bh(&bdi_lock);
1005
1006 synchronize_rcu_expedited();
1007 }
1008
1009 void bdi_unregister(struct backing_dev_info *bdi)
1010 {
1011 /* make sure nobody finds us on the bdi_list anymore */
1012 bdi_remove_from_list(bdi);
1013 wb_shutdown(&bdi->wb);
1014 cgwb_bdi_unregister(bdi);
1015
1016 if (bdi->dev) {
1017 bdi_debug_unregister(bdi);
1018 device_unregister(bdi->dev);
1019 bdi->dev = NULL;
1020 }
1021
1022 if (bdi->owner) {
1023 put_device(bdi->owner);
1024 bdi->owner = NULL;
1025 }
1026 }
1027
1028 static void release_bdi(struct kref *ref)
1029 {
1030 struct backing_dev_info *bdi =
1031 container_of(ref, struct backing_dev_info, refcnt);
1032
1033 if (test_bit(WB_registered, &bdi->wb.state))
1034 bdi_unregister(bdi);
1035 WARN_ON_ONCE(bdi->dev);
1036 wb_exit(&bdi->wb);
1037 cgwb_bdi_exit(bdi);
1038 kfree(bdi);
1039 }
1040
1041 void bdi_put(struct backing_dev_info *bdi)
1042 {
1043 kref_put(&bdi->refcnt, release_bdi);
1044 }
1045 EXPORT_SYMBOL(bdi_put);
1046
1047 const char *bdi_dev_name(struct backing_dev_info *bdi)
1048 {
1049 if (!bdi || !bdi->dev)
1050 return bdi_unknown_name;
1051 return bdi->dev_name;
1052 }
1053 EXPORT_SYMBOL_GPL(bdi_dev_name);
1054
1055 static wait_queue_head_t congestion_wqh[2] = {
1056 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
1057 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
1058 };
1059 static atomic_t nr_wb_congested[2];
1060
1061 void clear_wb_congested(struct bdi_writeback_congested *congested, int sync)
1062 {
1063 wait_queue_head_t *wqh = &congestion_wqh[sync];
1064 enum wb_congested_state bit;
1065
1066 bit = sync ? WB_sync_congested : WB_async_congested;
1067 if (test_and_clear_bit(bit, &congested->state))
1068 atomic_dec(&nr_wb_congested[sync]);
1069 smp_mb__after_atomic();
1070 if (waitqueue_active(wqh))
1071 wake_up(wqh);
1072 }
1073 EXPORT_SYMBOL(clear_wb_congested);
1074
1075 void set_wb_congested(struct bdi_writeback_congested *congested, int sync)
1076 {
1077 enum wb_congested_state bit;
1078
1079 bit = sync ? WB_sync_congested : WB_async_congested;
1080 if (!test_and_set_bit(bit, &congested->state))
1081 atomic_inc(&nr_wb_congested[sync]);
1082 }
1083 EXPORT_SYMBOL(set_wb_congested);
1084
1085 /**
1086 * congestion_wait - wait for a backing_dev to become uncongested
1087 * @sync: SYNC or ASYNC IO
1088 * @timeout: timeout in jiffies
1089 *
1090 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
1091 * write congestion. If no backing_devs are congested then just wait for the
1092 * next write to be completed.
1093 */
1094 long congestion_wait(int sync, long timeout)
1095 {
1096 long ret;
1097 unsigned long start = jiffies;
1098 DEFINE_WAIT(wait);
1099 wait_queue_head_t *wqh = &congestion_wqh[sync];
1100
1101 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1102 ret = io_schedule_timeout(timeout);
1103 finish_wait(wqh, &wait);
1104
1105 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
1106 jiffies_to_usecs(jiffies - start));
1107
1108 return ret;
1109 }
1110 EXPORT_SYMBOL(congestion_wait);
1111
1112 /**
1113 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a pgdat to complete writes
1114 * @sync: SYNC or ASYNC IO
1115 * @timeout: timeout in jiffies
1116 *
1117 * In the event of a congested backing_dev (any backing_dev) this waits
1118 * for up to @timeout jiffies for either a BDI to exit congestion of the
1119 * given @sync queue or a write to complete.
1120 *
1121 * The return value is 0 if the sleep is for the full timeout. Otherwise,
1122 * it is the number of jiffies that were still remaining when the function
1123 * returned. return_value == timeout implies the function did not sleep.
1124 */
1125 long wait_iff_congested(int sync, long timeout)
1126 {
1127 long ret;
1128 unsigned long start = jiffies;
1129 DEFINE_WAIT(wait);
1130 wait_queue_head_t *wqh = &congestion_wqh[sync];
1131
1132 /*
1133 * If there is no congestion, yield if necessary instead
1134 * of sleeping on the congestion queue
1135 */
1136 if (atomic_read(&nr_wb_congested[sync]) == 0) {
1137 cond_resched();
1138
1139 /* In case we scheduled, work out time remaining */
1140 ret = timeout - (jiffies - start);
1141 if (ret < 0)
1142 ret = 0;
1143
1144 goto out;
1145 }
1146
1147 /* Sleep until uncongested or a write happens */
1148 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1149 ret = io_schedule_timeout(timeout);
1150 finish_wait(wqh, &wait);
1151
1152 out:
1153 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
1154 jiffies_to_usecs(jiffies - start));
1155
1156 return ret;
1157 }
1158 EXPORT_SYMBOL(wait_iff_congested);