1 // SPDX-License-Identifier: GPL-2.0-only
2
3 #include <linux/blkdev.h>
4 #include <linux/wait.h>
5 #include <linux/rbtree.h>
6 #include <linux/kthread.h>
7 #include <linux/backing-dev.h>
8 #include <linux/blk-cgroup.h>
9 #include <linux/freezer.h>
10 #include <linux/fs.h>
11 #include <linux/pagemap.h>
12 #include <linux/mm.h>
13 #include <linux/sched/mm.h>
14 #include <linux/sched.h>
15 #include <linux/module.h>
16 #include <linux/writeback.h>
17 #include <linux/device.h>
18 #include <trace/events/writeback.h>
19
20 struct backing_dev_info noop_backing_dev_info;
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 #define K(x) ((x) << (PAGE_SHIFT - 10))
39
40 #ifdef CONFIG_DEBUG_FS
41 #include <linux/debugfs.h>
42 #include <linux/seq_file.h>
43
44 static struct dentry *bdi_debug_root;
45
bdi_debug_init(void)46 static void bdi_debug_init(void)
47 {
48 bdi_debug_root = debugfs_create_dir("bdi", NULL);
49 }
50
bdi_debug_stats_show(struct seq_file * m,void * v)51 static int bdi_debug_stats_show(struct seq_file *m, void *v)
52 {
53 struct backing_dev_info *bdi = m->private;
54 struct bdi_writeback *wb = &bdi->wb;
55 unsigned long background_thresh;
56 unsigned long dirty_thresh;
57 unsigned long wb_thresh;
58 unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
59 struct inode *inode;
60
61 nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
62 spin_lock(&wb->list_lock);
63 list_for_each_entry(inode, &wb->b_dirty, i_io_list)
64 nr_dirty++;
65 list_for_each_entry(inode, &wb->b_io, i_io_list)
66 nr_io++;
67 list_for_each_entry(inode, &wb->b_more_io, i_io_list)
68 nr_more_io++;
69 list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
70 if (inode->i_state & I_DIRTY_TIME)
71 nr_dirty_time++;
72 spin_unlock(&wb->list_lock);
73
74 global_dirty_limits(&background_thresh, &dirty_thresh);
75 wb_thresh = wb_calc_thresh(wb, dirty_thresh);
76
77 seq_printf(m,
78 "BdiWriteback: %10lu kB\n"
79 "BdiReclaimable: %10lu kB\n"
80 "BdiDirtyThresh: %10lu kB\n"
81 "DirtyThresh: %10lu kB\n"
82 "BackgroundThresh: %10lu kB\n"
83 "BdiDirtied: %10lu kB\n"
84 "BdiWritten: %10lu kB\n"
85 "BdiWriteBandwidth: %10lu kBps\n"
86 "b_dirty: %10lu\n"
87 "b_io: %10lu\n"
88 "b_more_io: %10lu\n"
89 "b_dirty_time: %10lu\n"
90 "bdi_list: %10u\n"
91 "state: %10lx\n",
92 (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
93 (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
94 K(wb_thresh),
95 K(dirty_thresh),
96 K(background_thresh),
97 (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
98 (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
99 (unsigned long) K(wb->write_bandwidth),
100 nr_dirty,
101 nr_io,
102 nr_more_io,
103 nr_dirty_time,
104 !list_empty(&bdi->bdi_list), bdi->wb.state);
105
106 return 0;
107 }
108 DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
109
bdi_debug_register(struct backing_dev_info * bdi,const char * name)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
bdi_debug_unregister(struct backing_dev_info * bdi)118 static void bdi_debug_unregister(struct backing_dev_info *bdi)
119 {
120 debugfs_remove_recursive(bdi->debug_dir);
121 }
122 #else
bdi_debug_init(void)123 static inline void bdi_debug_init(void)
124 {
125 }
bdi_debug_register(struct backing_dev_info * bdi,const char * name)126 static inline void bdi_debug_register(struct backing_dev_info *bdi,
127 const char *name)
128 {
129 }
bdi_debug_unregister(struct backing_dev_info * bdi)130 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
131 {
132 }
133 #endif
134
read_ahead_kb_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)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 BDI_SHOW(name, expr) \
153 static ssize_t name##_show(struct device *dev, \
154 struct device_attribute *attr, char *buf) \
155 { \
156 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
157 \
158 return sysfs_emit(buf, "%lld\n", (long long)expr); \
159 } \
160 static DEVICE_ATTR_RW(name);
161
162 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
163
min_ratio_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)164 static ssize_t min_ratio_store(struct device *dev,
165 struct device_attribute *attr, const char *buf, size_t count)
166 {
167 struct backing_dev_info *bdi = dev_get_drvdata(dev);
168 unsigned int ratio;
169 ssize_t ret;
170
171 ret = kstrtouint(buf, 10, &ratio);
172 if (ret < 0)
173 return ret;
174
175 ret = bdi_set_min_ratio(bdi, ratio);
176 if (!ret)
177 ret = count;
178
179 return ret;
180 }
181 BDI_SHOW(min_ratio, bdi->min_ratio / BDI_RATIO_SCALE)
182
min_ratio_fine_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)183 static ssize_t min_ratio_fine_store(struct device *dev,
184 struct device_attribute *attr, const char *buf, size_t count)
185 {
186 struct backing_dev_info *bdi = dev_get_drvdata(dev);
187 unsigned int ratio;
188 ssize_t ret;
189
190 ret = kstrtouint(buf, 10, &ratio);
191 if (ret < 0)
192 return ret;
193
194 ret = bdi_set_min_ratio_no_scale(bdi, ratio);
195 if (!ret)
196 ret = count;
197
198 return ret;
199 }
200 BDI_SHOW(min_ratio_fine, bdi->min_ratio)
201
max_ratio_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)202 static ssize_t max_ratio_store(struct device *dev,
203 struct device_attribute *attr, const char *buf, size_t count)
204 {
205 struct backing_dev_info *bdi = dev_get_drvdata(dev);
206 unsigned int ratio;
207 ssize_t ret;
208
209 ret = kstrtouint(buf, 10, &ratio);
210 if (ret < 0)
211 return ret;
212
213 ret = bdi_set_max_ratio(bdi, ratio);
214 if (!ret)
215 ret = count;
216
217 return ret;
218 }
219 BDI_SHOW(max_ratio, bdi->max_ratio / BDI_RATIO_SCALE)
220
max_ratio_fine_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)221 static ssize_t max_ratio_fine_store(struct device *dev,
222 struct device_attribute *attr, const char *buf, size_t count)
223 {
224 struct backing_dev_info *bdi = dev_get_drvdata(dev);
225 unsigned int ratio;
226 ssize_t ret;
227
228 ret = kstrtouint(buf, 10, &ratio);
229 if (ret < 0)
230 return ret;
231
232 ret = bdi_set_max_ratio_no_scale(bdi, ratio);
233 if (!ret)
234 ret = count;
235
236 return ret;
237 }
238 BDI_SHOW(max_ratio_fine, bdi->max_ratio)
239
min_bytes_show(struct device * dev,struct device_attribute * attr,char * buf)240 static ssize_t min_bytes_show(struct device *dev,
241 struct device_attribute *attr,
242 char *buf)
243 {
244 struct backing_dev_info *bdi = dev_get_drvdata(dev);
245
246 return sysfs_emit(buf, "%llu\n", bdi_get_min_bytes(bdi));
247 }
248
min_bytes_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)249 static ssize_t min_bytes_store(struct device *dev,
250 struct device_attribute *attr, const char *buf, size_t count)
251 {
252 struct backing_dev_info *bdi = dev_get_drvdata(dev);
253 u64 bytes;
254 ssize_t ret;
255
256 ret = kstrtoull(buf, 10, &bytes);
257 if (ret < 0)
258 return ret;
259
260 ret = bdi_set_min_bytes(bdi, bytes);
261 if (!ret)
262 ret = count;
263
264 return ret;
265 }
266 DEVICE_ATTR_RW(min_bytes);
267
max_bytes_show(struct device * dev,struct device_attribute * attr,char * buf)268 static ssize_t max_bytes_show(struct device *dev,
269 struct device_attribute *attr,
270 char *buf)
271 {
272 struct backing_dev_info *bdi = dev_get_drvdata(dev);
273
274 return sysfs_emit(buf, "%llu\n", bdi_get_max_bytes(bdi));
275 }
276
max_bytes_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)277 static ssize_t max_bytes_store(struct device *dev,
278 struct device_attribute *attr, const char *buf, size_t count)
279 {
280 struct backing_dev_info *bdi = dev_get_drvdata(dev);
281 u64 bytes;
282 ssize_t ret;
283
284 ret = kstrtoull(buf, 10, &bytes);
285 if (ret < 0)
286 return ret;
287
288 ret = bdi_set_max_bytes(bdi, bytes);
289 if (!ret)
290 ret = count;
291
292 return ret;
293 }
294 DEVICE_ATTR_RW(max_bytes);
295
stable_pages_required_show(struct device * dev,struct device_attribute * attr,char * buf)296 static ssize_t stable_pages_required_show(struct device *dev,
297 struct device_attribute *attr,
298 char *buf)
299 {
300 dev_warn_once(dev,
301 "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n");
302 return sysfs_emit(buf, "%d\n", 0);
303 }
304 static DEVICE_ATTR_RO(stable_pages_required);
305
strict_limit_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)306 static ssize_t strict_limit_store(struct device *dev,
307 struct device_attribute *attr, const char *buf, size_t count)
308 {
309 struct backing_dev_info *bdi = dev_get_drvdata(dev);
310 unsigned int strict_limit;
311 ssize_t ret;
312
313 ret = kstrtouint(buf, 10, &strict_limit);
314 if (ret < 0)
315 return ret;
316
317 ret = bdi_set_strict_limit(bdi, strict_limit);
318 if (!ret)
319 ret = count;
320
321 return ret;
322 }
323
strict_limit_show(struct device * dev,struct device_attribute * attr,char * buf)324 static ssize_t strict_limit_show(struct device *dev,
325 struct device_attribute *attr, char *buf)
326 {
327 struct backing_dev_info *bdi = dev_get_drvdata(dev);
328
329 return sysfs_emit(buf, "%d\n",
330 !!(bdi->capabilities & BDI_CAP_STRICTLIMIT));
331 }
332 static DEVICE_ATTR_RW(strict_limit);
333
334 static struct attribute *bdi_dev_attrs[] = {
335 &dev_attr_read_ahead_kb.attr,
336 &dev_attr_min_ratio.attr,
337 &dev_attr_min_ratio_fine.attr,
338 &dev_attr_max_ratio.attr,
339 &dev_attr_max_ratio_fine.attr,
340 &dev_attr_min_bytes.attr,
341 &dev_attr_max_bytes.attr,
342 &dev_attr_stable_pages_required.attr,
343 &dev_attr_strict_limit.attr,
344 NULL,
345 };
346 ATTRIBUTE_GROUPS(bdi_dev);
347
bdi_class_init(void)348 static __init int bdi_class_init(void)
349 {
350 bdi_class = class_create(THIS_MODULE, "bdi");
351 if (IS_ERR(bdi_class))
352 return PTR_ERR(bdi_class);
353
354 bdi_class->dev_groups = bdi_dev_groups;
355 bdi_debug_init();
356
357 return 0;
358 }
359 postcore_initcall(bdi_class_init);
360
default_bdi_init(void)361 static int __init default_bdi_init(void)
362 {
363 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
364 WQ_SYSFS, 0);
365 if (!bdi_wq)
366 return -ENOMEM;
367 return 0;
368 }
369 subsys_initcall(default_bdi_init);
370
371 /*
372 * This function is used when the first inode for this wb is marked dirty. It
373 * wakes-up the corresponding bdi thread which should then take care of the
374 * periodic background write-out of dirty inodes. Since the write-out would
375 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
376 * set up a timer which wakes the bdi thread up later.
377 *
378 * Note, we wouldn't bother setting up the timer, but this function is on the
379 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
380 * by delaying the wake-up.
381 *
382 * We have to be careful not to postpone flush work if it is scheduled for
383 * earlier. Thus we use queue_delayed_work().
384 */
wb_wakeup_delayed(struct bdi_writeback * wb)385 void wb_wakeup_delayed(struct bdi_writeback *wb)
386 {
387 unsigned long timeout;
388
389 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
390 spin_lock_irq(&wb->work_lock);
391 if (test_bit(WB_registered, &wb->state))
392 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
393 spin_unlock_irq(&wb->work_lock);
394 }
395
wb_update_bandwidth_workfn(struct work_struct * work)396 static void wb_update_bandwidth_workfn(struct work_struct *work)
397 {
398 struct bdi_writeback *wb = container_of(to_delayed_work(work),
399 struct bdi_writeback, bw_dwork);
400
401 wb_update_bandwidth(wb);
402 }
403
404 /*
405 * Initial write bandwidth: 100 MB/s
406 */
407 #define INIT_BW (100 << (20 - PAGE_SHIFT))
408
wb_init(struct bdi_writeback * wb,struct backing_dev_info * bdi,gfp_t gfp)409 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
410 gfp_t gfp)
411 {
412 int i, err;
413
414 memset(wb, 0, sizeof(*wb));
415
416 wb->bdi = bdi;
417 wb->last_old_flush = jiffies;
418 INIT_LIST_HEAD(&wb->b_dirty);
419 INIT_LIST_HEAD(&wb->b_io);
420 INIT_LIST_HEAD(&wb->b_more_io);
421 INIT_LIST_HEAD(&wb->b_dirty_time);
422 spin_lock_init(&wb->list_lock);
423
424 atomic_set(&wb->writeback_inodes, 0);
425 wb->bw_time_stamp = jiffies;
426 wb->balanced_dirty_ratelimit = INIT_BW;
427 wb->dirty_ratelimit = INIT_BW;
428 wb->write_bandwidth = INIT_BW;
429 wb->avg_write_bandwidth = INIT_BW;
430
431 spin_lock_init(&wb->work_lock);
432 INIT_LIST_HEAD(&wb->work_list);
433 INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
434 INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn);
435 wb->dirty_sleep = jiffies;
436
437 err = fprop_local_init_percpu(&wb->completions, gfp);
438 if (err)
439 return err;
440
441 for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
442 err = percpu_counter_init(&wb->stat[i], 0, gfp);
443 if (err)
444 goto out_destroy_stat;
445 }
446
447 return 0;
448
449 out_destroy_stat:
450 while (i--)
451 percpu_counter_destroy(&wb->stat[i]);
452 fprop_local_destroy_percpu(&wb->completions);
453 return err;
454 }
455
456 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
457
458 /*
459 * Remove bdi from the global list and shutdown any threads we have running
460 */
wb_shutdown(struct bdi_writeback * wb)461 static void wb_shutdown(struct bdi_writeback *wb)
462 {
463 /* Make sure nobody queues further work */
464 spin_lock_irq(&wb->work_lock);
465 if (!test_and_clear_bit(WB_registered, &wb->state)) {
466 spin_unlock_irq(&wb->work_lock);
467 return;
468 }
469 spin_unlock_irq(&wb->work_lock);
470
471 cgwb_remove_from_bdi_list(wb);
472 /*
473 * Drain work list and shutdown the delayed_work. !WB_registered
474 * tells wb_workfn() that @wb is dying and its work_list needs to
475 * be drained no matter what.
476 */
477 mod_delayed_work(bdi_wq, &wb->dwork, 0);
478 flush_delayed_work(&wb->dwork);
479 WARN_ON(!list_empty(&wb->work_list));
480 flush_delayed_work(&wb->bw_dwork);
481 }
482
wb_exit(struct bdi_writeback * wb)483 static void wb_exit(struct bdi_writeback *wb)
484 {
485 int i;
486
487 WARN_ON(delayed_work_pending(&wb->dwork));
488
489 for (i = 0; i < NR_WB_STAT_ITEMS; i++)
490 percpu_counter_destroy(&wb->stat[i]);
491
492 fprop_local_destroy_percpu(&wb->completions);
493 }
494
495 #ifdef CONFIG_CGROUP_WRITEBACK
496
497 #include <linux/memcontrol.h>
498
499 /*
500 * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
501 * memcg->cgwb_list. bdi->cgwb_tree is also RCU protected.
502 */
503 static DEFINE_SPINLOCK(cgwb_lock);
504 static struct workqueue_struct *cgwb_release_wq;
505
506 static LIST_HEAD(offline_cgwbs);
507 static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
508 static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
509
cgwb_release_workfn(struct work_struct * work)510 static void cgwb_release_workfn(struct work_struct *work)
511 {
512 struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
513 release_work);
514 struct backing_dev_info *bdi = wb->bdi;
515
516 mutex_lock(&wb->bdi->cgwb_release_mutex);
517 wb_shutdown(wb);
518
519 css_put(wb->memcg_css);
520 css_put(wb->blkcg_css);
521 mutex_unlock(&wb->bdi->cgwb_release_mutex);
522
523 /* triggers blkg destruction if no online users left */
524 blkcg_unpin_online(wb->blkcg_css);
525
526 fprop_local_destroy_percpu(&wb->memcg_completions);
527
528 spin_lock_irq(&cgwb_lock);
529 list_del(&wb->offline_node);
530 spin_unlock_irq(&cgwb_lock);
531
532 percpu_ref_exit(&wb->refcnt);
533 wb_exit(wb);
534 bdi_put(bdi);
535 WARN_ON_ONCE(!list_empty(&wb->b_attached));
536 kfree_rcu(wb, rcu);
537 }
538
cgwb_release(struct percpu_ref * refcnt)539 static void cgwb_release(struct percpu_ref *refcnt)
540 {
541 struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
542 refcnt);
543 queue_work(cgwb_release_wq, &wb->release_work);
544 }
545
cgwb_kill(struct bdi_writeback * wb)546 static void cgwb_kill(struct bdi_writeback *wb)
547 {
548 lockdep_assert_held(&cgwb_lock);
549
550 WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
551 list_del(&wb->memcg_node);
552 list_del(&wb->blkcg_node);
553 list_add(&wb->offline_node, &offline_cgwbs);
554 percpu_ref_kill(&wb->refcnt);
555 }
556
cgwb_remove_from_bdi_list(struct bdi_writeback * wb)557 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
558 {
559 spin_lock_irq(&cgwb_lock);
560 list_del_rcu(&wb->bdi_node);
561 spin_unlock_irq(&cgwb_lock);
562 }
563
cgwb_create(struct backing_dev_info * bdi,struct cgroup_subsys_state * memcg_css,gfp_t gfp)564 static int cgwb_create(struct backing_dev_info *bdi,
565 struct cgroup_subsys_state *memcg_css, gfp_t gfp)
566 {
567 struct mem_cgroup *memcg;
568 struct cgroup_subsys_state *blkcg_css;
569 struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
570 struct bdi_writeback *wb;
571 unsigned long flags;
572 int ret = 0;
573
574 memcg = mem_cgroup_from_css(memcg_css);
575 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
576 memcg_cgwb_list = &memcg->cgwb_list;
577 blkcg_cgwb_list = blkcg_get_cgwb_list(blkcg_css);
578
579 /* look up again under lock and discard on blkcg mismatch */
580 spin_lock_irqsave(&cgwb_lock, flags);
581 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
582 if (wb && wb->blkcg_css != blkcg_css) {
583 cgwb_kill(wb);
584 wb = NULL;
585 }
586 spin_unlock_irqrestore(&cgwb_lock, flags);
587 if (wb)
588 goto out_put;
589
590 /* need to create a new one */
591 wb = kmalloc(sizeof(*wb), gfp);
592 if (!wb) {
593 ret = -ENOMEM;
594 goto out_put;
595 }
596
597 ret = wb_init(wb, bdi, gfp);
598 if (ret)
599 goto err_free;
600
601 ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
602 if (ret)
603 goto err_wb_exit;
604
605 ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
606 if (ret)
607 goto err_ref_exit;
608
609 wb->memcg_css = memcg_css;
610 wb->blkcg_css = blkcg_css;
611 INIT_LIST_HEAD(&wb->b_attached);
612 INIT_WORK(&wb->release_work, cgwb_release_workfn);
613 set_bit(WB_registered, &wb->state);
614 bdi_get(bdi);
615
616 /*
617 * The root wb determines the registered state of the whole bdi and
618 * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
619 * whether they're still online. Don't link @wb if any is dead.
620 * See wb_memcg_offline() and wb_blkcg_offline().
621 */
622 ret = -ENODEV;
623 spin_lock_irqsave(&cgwb_lock, flags);
624 if (test_bit(WB_registered, &bdi->wb.state) &&
625 blkcg_cgwb_list->next && memcg_cgwb_list->next) {
626 /* we might have raced another instance of this function */
627 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
628 if (!ret) {
629 list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
630 list_add(&wb->memcg_node, memcg_cgwb_list);
631 list_add(&wb->blkcg_node, blkcg_cgwb_list);
632 blkcg_pin_online(blkcg_css);
633 css_get(memcg_css);
634 css_get(blkcg_css);
635 }
636 }
637 spin_unlock_irqrestore(&cgwb_lock, flags);
638 if (ret) {
639 if (ret == -EEXIST)
640 ret = 0;
641 goto err_fprop_exit;
642 }
643 goto out_put;
644
645 err_fprop_exit:
646 bdi_put(bdi);
647 fprop_local_destroy_percpu(&wb->memcg_completions);
648 err_ref_exit:
649 percpu_ref_exit(&wb->refcnt);
650 err_wb_exit:
651 wb_exit(wb);
652 err_free:
653 kfree(wb);
654 out_put:
655 css_put(blkcg_css);
656 return ret;
657 }
658
659 /**
660 * wb_get_lookup - get wb for a given memcg
661 * @bdi: target bdi
662 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
663 *
664 * Try to get the wb for @memcg_css on @bdi. The returned wb has its
665 * refcount incremented.
666 *
667 * This function uses css_get() on @memcg_css and thus expects its refcnt
668 * to be positive on invocation. IOW, rcu_read_lock() protection on
669 * @memcg_css isn't enough. try_get it before calling this function.
670 *
671 * A wb is keyed by its associated memcg. As blkcg implicitly enables
672 * memcg on the default hierarchy, memcg association is guaranteed to be
673 * more specific (equal or descendant to the associated blkcg) and thus can
674 * identify both the memcg and blkcg associations.
675 *
676 * Because the blkcg associated with a memcg may change as blkcg is enabled
677 * and disabled closer to root in the hierarchy, each wb keeps track of
678 * both the memcg and blkcg associated with it and verifies the blkcg on
679 * each lookup. On mismatch, the existing wb is discarded and a new one is
680 * created.
681 */
wb_get_lookup(struct backing_dev_info * bdi,struct cgroup_subsys_state * memcg_css)682 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
683 struct cgroup_subsys_state *memcg_css)
684 {
685 struct bdi_writeback *wb;
686
687 if (!memcg_css->parent)
688 return &bdi->wb;
689
690 rcu_read_lock();
691 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
692 if (wb) {
693 struct cgroup_subsys_state *blkcg_css;
694
695 /* see whether the blkcg association has changed */
696 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
697 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
698 wb = NULL;
699 css_put(blkcg_css);
700 }
701 rcu_read_unlock();
702
703 return wb;
704 }
705
706 /**
707 * wb_get_create - get wb for a given memcg, create if necessary
708 * @bdi: target bdi
709 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
710 * @gfp: allocation mask to use
711 *
712 * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
713 * create one. See wb_get_lookup() for more details.
714 */
wb_get_create(struct backing_dev_info * bdi,struct cgroup_subsys_state * memcg_css,gfp_t gfp)715 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
716 struct cgroup_subsys_state *memcg_css,
717 gfp_t gfp)
718 {
719 struct bdi_writeback *wb;
720
721 might_alloc(gfp);
722
723 if (!memcg_css->parent)
724 return &bdi->wb;
725
726 do {
727 wb = wb_get_lookup(bdi, memcg_css);
728 } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
729
730 return wb;
731 }
732
cgwb_bdi_init(struct backing_dev_info * bdi)733 static int cgwb_bdi_init(struct backing_dev_info *bdi)
734 {
735 int ret;
736
737 INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
738 mutex_init(&bdi->cgwb_release_mutex);
739 init_rwsem(&bdi->wb_switch_rwsem);
740
741 ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
742 if (!ret) {
743 bdi->wb.memcg_css = &root_mem_cgroup->css;
744 bdi->wb.blkcg_css = blkcg_root_css;
745 }
746 return ret;
747 }
748
cgwb_bdi_unregister(struct backing_dev_info * bdi)749 static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
750 {
751 struct radix_tree_iter iter;
752 void **slot;
753 struct bdi_writeback *wb;
754
755 WARN_ON(test_bit(WB_registered, &bdi->wb.state));
756
757 spin_lock_irq(&cgwb_lock);
758 radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
759 cgwb_kill(*slot);
760 spin_unlock_irq(&cgwb_lock);
761
762 mutex_lock(&bdi->cgwb_release_mutex);
763 spin_lock_irq(&cgwb_lock);
764 while (!list_empty(&bdi->wb_list)) {
765 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
766 bdi_node);
767 spin_unlock_irq(&cgwb_lock);
768 wb_shutdown(wb);
769 spin_lock_irq(&cgwb_lock);
770 }
771 spin_unlock_irq(&cgwb_lock);
772 mutex_unlock(&bdi->cgwb_release_mutex);
773 }
774
775 /*
776 * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
777 *
778 * Try to release dying cgwbs by switching attached inodes to the nearest
779 * living ancestor's writeback. Processed wbs are placed at the end
780 * of the list to guarantee the forward progress.
781 */
cleanup_offline_cgwbs_workfn(struct work_struct * work)782 static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
783 {
784 struct bdi_writeback *wb;
785 LIST_HEAD(processed);
786
787 spin_lock_irq(&cgwb_lock);
788
789 while (!list_empty(&offline_cgwbs)) {
790 wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
791 offline_node);
792 list_move(&wb->offline_node, &processed);
793
794 /*
795 * If wb is dirty, cleaning up the writeback by switching
796 * attached inodes will result in an effective removal of any
797 * bandwidth restrictions, which isn't the goal. Instead,
798 * it can be postponed until the next time, when all io
799 * will be likely completed. If in the meantime some inodes
800 * will get re-dirtied, they should be eventually switched to
801 * a new cgwb.
802 */
803 if (wb_has_dirty_io(wb))
804 continue;
805
806 if (!wb_tryget(wb))
807 continue;
808
809 spin_unlock_irq(&cgwb_lock);
810 while (cleanup_offline_cgwb(wb))
811 cond_resched();
812 spin_lock_irq(&cgwb_lock);
813
814 wb_put(wb);
815 }
816
817 if (!list_empty(&processed))
818 list_splice_tail(&processed, &offline_cgwbs);
819
820 spin_unlock_irq(&cgwb_lock);
821 }
822
823 /**
824 * wb_memcg_offline - kill all wb's associated with a memcg being offlined
825 * @memcg: memcg being offlined
826 *
827 * Also prevents creation of any new wb's associated with @memcg.
828 */
wb_memcg_offline(struct mem_cgroup * memcg)829 void wb_memcg_offline(struct mem_cgroup *memcg)
830 {
831 struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
832 struct bdi_writeback *wb, *next;
833
834 spin_lock_irq(&cgwb_lock);
835 list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
836 cgwb_kill(wb);
837 memcg_cgwb_list->next = NULL; /* prevent new wb's */
838 spin_unlock_irq(&cgwb_lock);
839
840 queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
841 }
842
843 /**
844 * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
845 * @css: blkcg being offlined
846 *
847 * Also prevents creation of any new wb's associated with @blkcg.
848 */
wb_blkcg_offline(struct cgroup_subsys_state * css)849 void wb_blkcg_offline(struct cgroup_subsys_state *css)
850 {
851 struct bdi_writeback *wb, *next;
852 struct list_head *list = blkcg_get_cgwb_list(css);
853
854 spin_lock_irq(&cgwb_lock);
855 list_for_each_entry_safe(wb, next, list, blkcg_node)
856 cgwb_kill(wb);
857 list->next = NULL; /* prevent new wb's */
858 spin_unlock_irq(&cgwb_lock);
859 }
860
cgwb_bdi_register(struct backing_dev_info * bdi)861 static void cgwb_bdi_register(struct backing_dev_info *bdi)
862 {
863 spin_lock_irq(&cgwb_lock);
864 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
865 spin_unlock_irq(&cgwb_lock);
866 }
867
cgwb_init(void)868 static int __init cgwb_init(void)
869 {
870 /*
871 * There can be many concurrent release work items overwhelming
872 * system_wq. Put them in a separate wq and limit concurrency.
873 * There's no point in executing many of these in parallel.
874 */
875 cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
876 if (!cgwb_release_wq)
877 return -ENOMEM;
878
879 return 0;
880 }
881 subsys_initcall(cgwb_init);
882
883 #else /* CONFIG_CGROUP_WRITEBACK */
884
cgwb_bdi_init(struct backing_dev_info * bdi)885 static int cgwb_bdi_init(struct backing_dev_info *bdi)
886 {
887 return wb_init(&bdi->wb, bdi, GFP_KERNEL);
888 }
889
cgwb_bdi_unregister(struct backing_dev_info * bdi)890 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
891
cgwb_bdi_register(struct backing_dev_info * bdi)892 static void cgwb_bdi_register(struct backing_dev_info *bdi)
893 {
894 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
895 }
896
cgwb_remove_from_bdi_list(struct bdi_writeback * wb)897 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
898 {
899 list_del_rcu(&wb->bdi_node);
900 }
901
902 #endif /* CONFIG_CGROUP_WRITEBACK */
903
bdi_init(struct backing_dev_info * bdi)904 int bdi_init(struct backing_dev_info *bdi)
905 {
906 bdi->dev = NULL;
907
908 kref_init(&bdi->refcnt);
909 bdi->min_ratio = 0;
910 bdi->max_ratio = 100 * BDI_RATIO_SCALE;
911 bdi->max_prop_frac = FPROP_FRAC_BASE;
912 INIT_LIST_HEAD(&bdi->bdi_list);
913 INIT_LIST_HEAD(&bdi->wb_list);
914 init_waitqueue_head(&bdi->wb_waitq);
915
916 return cgwb_bdi_init(bdi);
917 }
918
bdi_alloc(int node_id)919 struct backing_dev_info *bdi_alloc(int node_id)
920 {
921 struct backing_dev_info *bdi;
922
923 bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
924 if (!bdi)
925 return NULL;
926
927 if (bdi_init(bdi)) {
928 kfree(bdi);
929 return NULL;
930 }
931 bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
932 bdi->ra_pages = VM_READAHEAD_PAGES;
933 bdi->io_pages = VM_READAHEAD_PAGES;
934 timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
935 return bdi;
936 }
937 EXPORT_SYMBOL(bdi_alloc);
938
bdi_lookup_rb_node(u64 id,struct rb_node ** parentp)939 static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
940 {
941 struct rb_node **p = &bdi_tree.rb_node;
942 struct rb_node *parent = NULL;
943 struct backing_dev_info *bdi;
944
945 lockdep_assert_held(&bdi_lock);
946
947 while (*p) {
948 parent = *p;
949 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
950
951 if (bdi->id > id)
952 p = &(*p)->rb_left;
953 else if (bdi->id < id)
954 p = &(*p)->rb_right;
955 else
956 break;
957 }
958
959 if (parentp)
960 *parentp = parent;
961 return p;
962 }
963
964 /**
965 * bdi_get_by_id - lookup and get bdi from its id
966 * @id: bdi id to lookup
967 *
968 * Find bdi matching @id and get it. Returns NULL if the matching bdi
969 * doesn't exist or is already unregistered.
970 */
bdi_get_by_id(u64 id)971 struct backing_dev_info *bdi_get_by_id(u64 id)
972 {
973 struct backing_dev_info *bdi = NULL;
974 struct rb_node **p;
975
976 spin_lock_bh(&bdi_lock);
977 p = bdi_lookup_rb_node(id, NULL);
978 if (*p) {
979 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
980 bdi_get(bdi);
981 }
982 spin_unlock_bh(&bdi_lock);
983
984 return bdi;
985 }
986
bdi_register_va(struct backing_dev_info * bdi,const char * fmt,va_list args)987 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
988 {
989 struct device *dev;
990 struct rb_node *parent, **p;
991
992 if (bdi->dev) /* The driver needs to use separate queues per device */
993 return 0;
994
995 vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
996 dev = device_create(bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
997 if (IS_ERR(dev))
998 return PTR_ERR(dev);
999
1000 cgwb_bdi_register(bdi);
1001 bdi->dev = dev;
1002
1003 bdi_debug_register(bdi, dev_name(dev));
1004 set_bit(WB_registered, &bdi->wb.state);
1005
1006 spin_lock_bh(&bdi_lock);
1007
1008 bdi->id = ++bdi_id_cursor;
1009
1010 p = bdi_lookup_rb_node(bdi->id, &parent);
1011 rb_link_node(&bdi->rb_node, parent, p);
1012 rb_insert_color(&bdi->rb_node, &bdi_tree);
1013
1014 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
1015
1016 spin_unlock_bh(&bdi_lock);
1017
1018 trace_writeback_bdi_register(bdi);
1019 return 0;
1020 }
1021
bdi_register(struct backing_dev_info * bdi,const char * fmt,...)1022 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
1023 {
1024 va_list args;
1025 int ret;
1026
1027 va_start(args, fmt);
1028 ret = bdi_register_va(bdi, fmt, args);
1029 va_end(args);
1030 return ret;
1031 }
1032 EXPORT_SYMBOL(bdi_register);
1033
bdi_set_owner(struct backing_dev_info * bdi,struct device * owner)1034 void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
1035 {
1036 WARN_ON_ONCE(bdi->owner);
1037 bdi->owner = owner;
1038 get_device(owner);
1039 }
1040
1041 /*
1042 * Remove bdi from bdi_list, and ensure that it is no longer visible
1043 */
bdi_remove_from_list(struct backing_dev_info * bdi)1044 static void bdi_remove_from_list(struct backing_dev_info *bdi)
1045 {
1046 spin_lock_bh(&bdi_lock);
1047 rb_erase(&bdi->rb_node, &bdi_tree);
1048 list_del_rcu(&bdi->bdi_list);
1049 spin_unlock_bh(&bdi_lock);
1050
1051 synchronize_rcu_expedited();
1052 }
1053
bdi_unregister(struct backing_dev_info * bdi)1054 void bdi_unregister(struct backing_dev_info *bdi)
1055 {
1056 del_timer_sync(&bdi->laptop_mode_wb_timer);
1057
1058 /* make sure nobody finds us on the bdi_list anymore */
1059 bdi_remove_from_list(bdi);
1060 wb_shutdown(&bdi->wb);
1061 cgwb_bdi_unregister(bdi);
1062
1063 /*
1064 * If this BDI's min ratio has been set, use bdi_set_min_ratio() to
1065 * update the global bdi_min_ratio.
1066 */
1067 if (bdi->min_ratio)
1068 bdi_set_min_ratio(bdi, 0);
1069
1070 if (bdi->dev) {
1071 bdi_debug_unregister(bdi);
1072 device_unregister(bdi->dev);
1073 bdi->dev = NULL;
1074 }
1075
1076 if (bdi->owner) {
1077 put_device(bdi->owner);
1078 bdi->owner = NULL;
1079 }
1080 }
1081 EXPORT_SYMBOL(bdi_unregister);
1082
release_bdi(struct kref * ref)1083 static void release_bdi(struct kref *ref)
1084 {
1085 struct backing_dev_info *bdi =
1086 container_of(ref, struct backing_dev_info, refcnt);
1087
1088 WARN_ON_ONCE(test_bit(WB_registered, &bdi->wb.state));
1089 WARN_ON_ONCE(bdi->dev);
1090 wb_exit(&bdi->wb);
1091 kfree(bdi);
1092 }
1093
bdi_put(struct backing_dev_info * bdi)1094 void bdi_put(struct backing_dev_info *bdi)
1095 {
1096 kref_put(&bdi->refcnt, release_bdi);
1097 }
1098 EXPORT_SYMBOL(bdi_put);
1099
inode_to_bdi(struct inode * inode)1100 struct backing_dev_info *inode_to_bdi(struct inode *inode)
1101 {
1102 struct super_block *sb;
1103
1104 if (!inode)
1105 return &noop_backing_dev_info;
1106
1107 sb = inode->i_sb;
1108 #ifdef CONFIG_BLOCK
1109 if (sb_is_blkdev_sb(sb))
1110 return I_BDEV(inode)->bd_disk->bdi;
1111 #endif
1112 return sb->s_bdi;
1113 }
1114 EXPORT_SYMBOL(inode_to_bdi);
1115
bdi_dev_name(struct backing_dev_info * bdi)1116 const char *bdi_dev_name(struct backing_dev_info *bdi)
1117 {
1118 if (!bdi || !bdi->dev)
1119 return bdi_unknown_name;
1120 return bdi->dev_name;
1121 }
1122 EXPORT_SYMBOL_GPL(bdi_dev_name);
1123