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 #include "internal.h"
20
21 struct backing_dev_info noop_backing_dev_info;
22 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
23
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
bdi_debug_init(void)44 static void bdi_debug_init(void)
45 {
46 bdi_debug_root = debugfs_create_dir("bdi", NULL);
47 }
48
bdi_debug_stats_show(struct seq_file * m,void * v)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 seq_printf(m,
76 "BdiWriteback: %10lu kB\n"
77 "BdiReclaimable: %10lu kB\n"
78 "BdiDirtyThresh: %10lu kB\n"
79 "DirtyThresh: %10lu kB\n"
80 "BackgroundThresh: %10lu kB\n"
81 "BdiDirtied: %10lu kB\n"
82 "BdiWritten: %10lu kB\n"
83 "BdiWriteBandwidth: %10lu kBps\n"
84 "b_dirty: %10lu\n"
85 "b_io: %10lu\n"
86 "b_more_io: %10lu\n"
87 "b_dirty_time: %10lu\n"
88 "bdi_list: %10u\n"
89 "state: %10lx\n",
90 (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
91 (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
92 K(wb_thresh),
93 K(dirty_thresh),
94 K(background_thresh),
95 (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
96 (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
97 (unsigned long) K(wb->write_bandwidth),
98 nr_dirty,
99 nr_io,
100 nr_more_io,
101 nr_dirty_time,
102 !list_empty(&bdi->bdi_list), bdi->wb.state);
103
104 return 0;
105 }
106 DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
107
bdi_debug_register(struct backing_dev_info * bdi,const char * name)108 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
109 {
110 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
111
112 debugfs_create_file("stats", 0444, bdi->debug_dir, bdi,
113 &bdi_debug_stats_fops);
114 }
115
bdi_debug_unregister(struct backing_dev_info * bdi)116 static void bdi_debug_unregister(struct backing_dev_info *bdi)
117 {
118 debugfs_remove_recursive(bdi->debug_dir);
119 }
120 #else
bdi_debug_init(void)121 static inline void bdi_debug_init(void)
122 {
123 }
bdi_debug_register(struct backing_dev_info * bdi,const char * name)124 static inline void bdi_debug_register(struct backing_dev_info *bdi,
125 const char *name)
126 {
127 }
bdi_debug_unregister(struct backing_dev_info * bdi)128 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
129 {
130 }
131 #endif
132
read_ahead_kb_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)133 static ssize_t read_ahead_kb_store(struct device *dev,
134 struct device_attribute *attr,
135 const char *buf, size_t count)
136 {
137 struct backing_dev_info *bdi = dev_get_drvdata(dev);
138 unsigned long read_ahead_kb;
139 ssize_t ret;
140
141 ret = kstrtoul(buf, 10, &read_ahead_kb);
142 if (ret < 0)
143 return ret;
144
145 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
146
147 return count;
148 }
149
150 #define BDI_SHOW(name, expr) \
151 static ssize_t name##_show(struct device *dev, \
152 struct device_attribute *attr, char *buf) \
153 { \
154 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
155 \
156 return sysfs_emit(buf, "%lld\n", (long long)expr); \
157 } \
158 static DEVICE_ATTR_RW(name);
159
160 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
161
min_ratio_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)162 static ssize_t min_ratio_store(struct device *dev,
163 struct device_attribute *attr, const char *buf, size_t count)
164 {
165 struct backing_dev_info *bdi = dev_get_drvdata(dev);
166 unsigned int ratio;
167 ssize_t ret;
168
169 ret = kstrtouint(buf, 10, &ratio);
170 if (ret < 0)
171 return ret;
172
173 ret = bdi_set_min_ratio(bdi, ratio);
174 if (!ret)
175 ret = count;
176
177 return ret;
178 }
179 BDI_SHOW(min_ratio, bdi->min_ratio / BDI_RATIO_SCALE)
180
min_ratio_fine_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)181 static ssize_t min_ratio_fine_store(struct device *dev,
182 struct device_attribute *attr, const char *buf, size_t count)
183 {
184 struct backing_dev_info *bdi = dev_get_drvdata(dev);
185 unsigned int ratio;
186 ssize_t ret;
187
188 ret = kstrtouint(buf, 10, &ratio);
189 if (ret < 0)
190 return ret;
191
192 ret = bdi_set_min_ratio_no_scale(bdi, ratio);
193 if (!ret)
194 ret = count;
195
196 return ret;
197 }
198 BDI_SHOW(min_ratio_fine, bdi->min_ratio)
199
max_ratio_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)200 static ssize_t max_ratio_store(struct device *dev,
201 struct device_attribute *attr, const char *buf, size_t count)
202 {
203 struct backing_dev_info *bdi = dev_get_drvdata(dev);
204 unsigned int ratio;
205 ssize_t ret;
206
207 ret = kstrtouint(buf, 10, &ratio);
208 if (ret < 0)
209 return ret;
210
211 ret = bdi_set_max_ratio(bdi, ratio);
212 if (!ret)
213 ret = count;
214
215 return ret;
216 }
217 BDI_SHOW(max_ratio, bdi->max_ratio / BDI_RATIO_SCALE)
218
max_ratio_fine_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)219 static ssize_t max_ratio_fine_store(struct device *dev,
220 struct device_attribute *attr, const char *buf, size_t count)
221 {
222 struct backing_dev_info *bdi = dev_get_drvdata(dev);
223 unsigned int ratio;
224 ssize_t ret;
225
226 ret = kstrtouint(buf, 10, &ratio);
227 if (ret < 0)
228 return ret;
229
230 ret = bdi_set_max_ratio_no_scale(bdi, ratio);
231 if (!ret)
232 ret = count;
233
234 return ret;
235 }
236 BDI_SHOW(max_ratio_fine, bdi->max_ratio)
237
min_bytes_show(struct device * dev,struct device_attribute * attr,char * buf)238 static ssize_t min_bytes_show(struct device *dev,
239 struct device_attribute *attr,
240 char *buf)
241 {
242 struct backing_dev_info *bdi = dev_get_drvdata(dev);
243
244 return sysfs_emit(buf, "%llu\n", bdi_get_min_bytes(bdi));
245 }
246
min_bytes_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)247 static ssize_t min_bytes_store(struct device *dev,
248 struct device_attribute *attr, const char *buf, size_t count)
249 {
250 struct backing_dev_info *bdi = dev_get_drvdata(dev);
251 u64 bytes;
252 ssize_t ret;
253
254 ret = kstrtoull(buf, 10, &bytes);
255 if (ret < 0)
256 return ret;
257
258 ret = bdi_set_min_bytes(bdi, bytes);
259 if (!ret)
260 ret = count;
261
262 return ret;
263 }
264 static DEVICE_ATTR_RW(min_bytes);
265
max_bytes_show(struct device * dev,struct device_attribute * attr,char * buf)266 static ssize_t max_bytes_show(struct device *dev,
267 struct device_attribute *attr,
268 char *buf)
269 {
270 struct backing_dev_info *bdi = dev_get_drvdata(dev);
271
272 return sysfs_emit(buf, "%llu\n", bdi_get_max_bytes(bdi));
273 }
274
max_bytes_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)275 static ssize_t max_bytes_store(struct device *dev,
276 struct device_attribute *attr, const char *buf, size_t count)
277 {
278 struct backing_dev_info *bdi = dev_get_drvdata(dev);
279 u64 bytes;
280 ssize_t ret;
281
282 ret = kstrtoull(buf, 10, &bytes);
283 if (ret < 0)
284 return ret;
285
286 ret = bdi_set_max_bytes(bdi, bytes);
287 if (!ret)
288 ret = count;
289
290 return ret;
291 }
292 static DEVICE_ATTR_RW(max_bytes);
293
stable_pages_required_show(struct device * dev,struct device_attribute * attr,char * buf)294 static ssize_t stable_pages_required_show(struct device *dev,
295 struct device_attribute *attr,
296 char *buf)
297 {
298 dev_warn_once(dev,
299 "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n");
300 return sysfs_emit(buf, "%d\n", 0);
301 }
302 static DEVICE_ATTR_RO(stable_pages_required);
303
strict_limit_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)304 static ssize_t strict_limit_store(struct device *dev,
305 struct device_attribute *attr, const char *buf, size_t count)
306 {
307 struct backing_dev_info *bdi = dev_get_drvdata(dev);
308 unsigned int strict_limit;
309 ssize_t ret;
310
311 ret = kstrtouint(buf, 10, &strict_limit);
312 if (ret < 0)
313 return ret;
314
315 ret = bdi_set_strict_limit(bdi, strict_limit);
316 if (!ret)
317 ret = count;
318
319 return ret;
320 }
321
strict_limit_show(struct device * dev,struct device_attribute * attr,char * buf)322 static ssize_t strict_limit_show(struct device *dev,
323 struct device_attribute *attr, char *buf)
324 {
325 struct backing_dev_info *bdi = dev_get_drvdata(dev);
326
327 return sysfs_emit(buf, "%d\n",
328 !!(bdi->capabilities & BDI_CAP_STRICTLIMIT));
329 }
330 static DEVICE_ATTR_RW(strict_limit);
331
332 static struct attribute *bdi_dev_attrs[] = {
333 &dev_attr_read_ahead_kb.attr,
334 &dev_attr_min_ratio.attr,
335 &dev_attr_min_ratio_fine.attr,
336 &dev_attr_max_ratio.attr,
337 &dev_attr_max_ratio_fine.attr,
338 &dev_attr_min_bytes.attr,
339 &dev_attr_max_bytes.attr,
340 &dev_attr_stable_pages_required.attr,
341 &dev_attr_strict_limit.attr,
342 NULL,
343 };
344 ATTRIBUTE_GROUPS(bdi_dev);
345
346 static const struct class bdi_class = {
347 .name = "bdi",
348 .dev_groups = bdi_dev_groups,
349 };
350
bdi_class_init(void)351 static __init int bdi_class_init(void)
352 {
353 int ret;
354
355 ret = class_register(&bdi_class);
356 if (ret)
357 return ret;
358
359 bdi_debug_init();
360
361 return 0;
362 }
363 postcore_initcall(bdi_class_init);
364
default_bdi_init(void)365 static int __init default_bdi_init(void)
366 {
367 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
368 WQ_SYSFS, 0);
369 if (!bdi_wq)
370 return -ENOMEM;
371 return 0;
372 }
373 subsys_initcall(default_bdi_init);
374
375 /*
376 * This function is used when the first inode for this wb is marked dirty. It
377 * wakes-up the corresponding bdi thread which should then take care of the
378 * periodic background write-out of dirty inodes. Since the write-out would
379 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
380 * set up a timer which wakes the bdi thread up later.
381 *
382 * Note, we wouldn't bother setting up the timer, but this function is on the
383 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
384 * by delaying the wake-up.
385 *
386 * We have to be careful not to postpone flush work if it is scheduled for
387 * earlier. Thus we use queue_delayed_work().
388 */
wb_wakeup_delayed(struct bdi_writeback * wb)389 void wb_wakeup_delayed(struct bdi_writeback *wb)
390 {
391 unsigned long timeout;
392
393 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
394 spin_lock_irq(&wb->work_lock);
395 if (test_bit(WB_registered, &wb->state))
396 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
397 spin_unlock_irq(&wb->work_lock);
398 }
399
wb_update_bandwidth_workfn(struct work_struct * work)400 static void wb_update_bandwidth_workfn(struct work_struct *work)
401 {
402 struct bdi_writeback *wb = container_of(to_delayed_work(work),
403 struct bdi_writeback, bw_dwork);
404
405 wb_update_bandwidth(wb);
406 }
407
408 /*
409 * Initial write bandwidth: 100 MB/s
410 */
411 #define INIT_BW (100 << (20 - PAGE_SHIFT))
412
wb_init(struct bdi_writeback * wb,struct backing_dev_info * bdi,gfp_t gfp)413 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
414 gfp_t gfp)
415 {
416 int i, err;
417
418 memset(wb, 0, sizeof(*wb));
419
420 wb->bdi = bdi;
421 wb->last_old_flush = jiffies;
422 INIT_LIST_HEAD(&wb->b_dirty);
423 INIT_LIST_HEAD(&wb->b_io);
424 INIT_LIST_HEAD(&wb->b_more_io);
425 INIT_LIST_HEAD(&wb->b_dirty_time);
426 spin_lock_init(&wb->list_lock);
427
428 atomic_set(&wb->writeback_inodes, 0);
429 wb->bw_time_stamp = jiffies;
430 wb->balanced_dirty_ratelimit = INIT_BW;
431 wb->dirty_ratelimit = INIT_BW;
432 wb->write_bandwidth = INIT_BW;
433 wb->avg_write_bandwidth = INIT_BW;
434
435 spin_lock_init(&wb->work_lock);
436 INIT_LIST_HEAD(&wb->work_list);
437 INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
438 INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn);
439 wb->dirty_sleep = jiffies;
440
441 err = fprop_local_init_percpu(&wb->completions, gfp);
442 if (err)
443 return err;
444
445 for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
446 err = percpu_counter_init(&wb->stat[i], 0, gfp);
447 if (err)
448 goto out_destroy_stat;
449 }
450
451 return 0;
452
453 out_destroy_stat:
454 while (i--)
455 percpu_counter_destroy(&wb->stat[i]);
456 fprop_local_destroy_percpu(&wb->completions);
457 return err;
458 }
459
460 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
461
462 /*
463 * Remove bdi from the global list and shutdown any threads we have running
464 */
wb_shutdown(struct bdi_writeback * wb)465 static void wb_shutdown(struct bdi_writeback *wb)
466 {
467 /* Make sure nobody queues further work */
468 spin_lock_irq(&wb->work_lock);
469 if (!test_and_clear_bit(WB_registered, &wb->state)) {
470 spin_unlock_irq(&wb->work_lock);
471 return;
472 }
473 spin_unlock_irq(&wb->work_lock);
474
475 cgwb_remove_from_bdi_list(wb);
476 /*
477 * Drain work list and shutdown the delayed_work. !WB_registered
478 * tells wb_workfn() that @wb is dying and its work_list needs to
479 * be drained no matter what.
480 */
481 mod_delayed_work(bdi_wq, &wb->dwork, 0);
482 flush_delayed_work(&wb->dwork);
483 WARN_ON(!list_empty(&wb->work_list));
484 flush_delayed_work(&wb->bw_dwork);
485 }
486
wb_exit(struct bdi_writeback * wb)487 static void wb_exit(struct bdi_writeback *wb)
488 {
489 int i;
490
491 WARN_ON(delayed_work_pending(&wb->dwork));
492
493 for (i = 0; i < NR_WB_STAT_ITEMS; i++)
494 percpu_counter_destroy(&wb->stat[i]);
495
496 fprop_local_destroy_percpu(&wb->completions);
497 }
498
499 #ifdef CONFIG_CGROUP_WRITEBACK
500
501 #include <linux/memcontrol.h>
502
503 /*
504 * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
505 * memcg->cgwb_list. bdi->cgwb_tree is also RCU protected.
506 */
507 static DEFINE_SPINLOCK(cgwb_lock);
508 static struct workqueue_struct *cgwb_release_wq;
509
510 static LIST_HEAD(offline_cgwbs);
511 static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
512 static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
513
cgwb_free_rcu(struct rcu_head * rcu_head)514 static void cgwb_free_rcu(struct rcu_head *rcu_head)
515 {
516 struct bdi_writeback *wb = container_of(rcu_head,
517 struct bdi_writeback, rcu);
518
519 percpu_ref_exit(&wb->refcnt);
520 kfree(wb);
521 }
522
cgwb_release_workfn(struct work_struct * work)523 static void cgwb_release_workfn(struct work_struct *work)
524 {
525 struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
526 release_work);
527 struct backing_dev_info *bdi = wb->bdi;
528
529 mutex_lock(&wb->bdi->cgwb_release_mutex);
530 wb_shutdown(wb);
531
532 css_put(wb->memcg_css);
533 css_put(wb->blkcg_css);
534 mutex_unlock(&wb->bdi->cgwb_release_mutex);
535
536 /* triggers blkg destruction if no online users left */
537 blkcg_unpin_online(wb->blkcg_css);
538
539 fprop_local_destroy_percpu(&wb->memcg_completions);
540
541 spin_lock_irq(&cgwb_lock);
542 list_del(&wb->offline_node);
543 spin_unlock_irq(&cgwb_lock);
544
545 wb_exit(wb);
546 bdi_put(bdi);
547 WARN_ON_ONCE(!list_empty(&wb->b_attached));
548 call_rcu(&wb->rcu, cgwb_free_rcu);
549 }
550
cgwb_release(struct percpu_ref * refcnt)551 static void cgwb_release(struct percpu_ref *refcnt)
552 {
553 struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
554 refcnt);
555 queue_work(cgwb_release_wq, &wb->release_work);
556 }
557
cgwb_kill(struct bdi_writeback * wb)558 static void cgwb_kill(struct bdi_writeback *wb)
559 {
560 lockdep_assert_held(&cgwb_lock);
561
562 WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
563 list_del(&wb->memcg_node);
564 list_del(&wb->blkcg_node);
565 list_add(&wb->offline_node, &offline_cgwbs);
566 percpu_ref_kill(&wb->refcnt);
567 }
568
cgwb_remove_from_bdi_list(struct bdi_writeback * wb)569 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
570 {
571 spin_lock_irq(&cgwb_lock);
572 list_del_rcu(&wb->bdi_node);
573 spin_unlock_irq(&cgwb_lock);
574 }
575
cgwb_create(struct backing_dev_info * bdi,struct cgroup_subsys_state * memcg_css,gfp_t gfp)576 static int cgwb_create(struct backing_dev_info *bdi,
577 struct cgroup_subsys_state *memcg_css, gfp_t gfp)
578 {
579 struct mem_cgroup *memcg;
580 struct cgroup_subsys_state *blkcg_css;
581 struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
582 struct bdi_writeback *wb;
583 unsigned long flags;
584 int ret = 0;
585
586 memcg = mem_cgroup_from_css(memcg_css);
587 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
588 memcg_cgwb_list = &memcg->cgwb_list;
589 blkcg_cgwb_list = blkcg_get_cgwb_list(blkcg_css);
590
591 /* look up again under lock and discard on blkcg mismatch */
592 spin_lock_irqsave(&cgwb_lock, flags);
593 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
594 if (wb && wb->blkcg_css != blkcg_css) {
595 cgwb_kill(wb);
596 wb = NULL;
597 }
598 spin_unlock_irqrestore(&cgwb_lock, flags);
599 if (wb)
600 goto out_put;
601
602 /* need to create a new one */
603 wb = kmalloc(sizeof(*wb), gfp);
604 if (!wb) {
605 ret = -ENOMEM;
606 goto out_put;
607 }
608
609 ret = wb_init(wb, bdi, gfp);
610 if (ret)
611 goto err_free;
612
613 ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
614 if (ret)
615 goto err_wb_exit;
616
617 ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
618 if (ret)
619 goto err_ref_exit;
620
621 wb->memcg_css = memcg_css;
622 wb->blkcg_css = blkcg_css;
623 INIT_LIST_HEAD(&wb->b_attached);
624 INIT_WORK(&wb->release_work, cgwb_release_workfn);
625 set_bit(WB_registered, &wb->state);
626 bdi_get(bdi);
627
628 /*
629 * The root wb determines the registered state of the whole bdi and
630 * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
631 * whether they're still online. Don't link @wb if any is dead.
632 * See wb_memcg_offline() and wb_blkcg_offline().
633 */
634 ret = -ENODEV;
635 spin_lock_irqsave(&cgwb_lock, flags);
636 if (test_bit(WB_registered, &bdi->wb.state) &&
637 blkcg_cgwb_list->next && memcg_cgwb_list->next) {
638 /* we might have raced another instance of this function */
639 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
640 if (!ret) {
641 list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
642 list_add(&wb->memcg_node, memcg_cgwb_list);
643 list_add(&wb->blkcg_node, blkcg_cgwb_list);
644 blkcg_pin_online(blkcg_css);
645 css_get(memcg_css);
646 css_get(blkcg_css);
647 }
648 }
649 spin_unlock_irqrestore(&cgwb_lock, flags);
650 if (ret) {
651 if (ret == -EEXIST)
652 ret = 0;
653 goto err_fprop_exit;
654 }
655 goto out_put;
656
657 err_fprop_exit:
658 bdi_put(bdi);
659 fprop_local_destroy_percpu(&wb->memcg_completions);
660 err_ref_exit:
661 percpu_ref_exit(&wb->refcnt);
662 err_wb_exit:
663 wb_exit(wb);
664 err_free:
665 kfree(wb);
666 out_put:
667 css_put(blkcg_css);
668 return ret;
669 }
670
671 /**
672 * wb_get_lookup - get wb for a given memcg
673 * @bdi: target bdi
674 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
675 *
676 * Try to get the wb for @memcg_css on @bdi. The returned wb has its
677 * refcount incremented.
678 *
679 * This function uses css_get() on @memcg_css and thus expects its refcnt
680 * to be positive on invocation. IOW, rcu_read_lock() protection on
681 * @memcg_css isn't enough. try_get it before calling this function.
682 *
683 * A wb is keyed by its associated memcg. As blkcg implicitly enables
684 * memcg on the default hierarchy, memcg association is guaranteed to be
685 * more specific (equal or descendant to the associated blkcg) and thus can
686 * identify both the memcg and blkcg associations.
687 *
688 * Because the blkcg associated with a memcg may change as blkcg is enabled
689 * and disabled closer to root in the hierarchy, each wb keeps track of
690 * both the memcg and blkcg associated with it and verifies the blkcg on
691 * each lookup. On mismatch, the existing wb is discarded and a new one is
692 * created.
693 */
wb_get_lookup(struct backing_dev_info * bdi,struct cgroup_subsys_state * memcg_css)694 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
695 struct cgroup_subsys_state *memcg_css)
696 {
697 struct bdi_writeback *wb;
698
699 if (!memcg_css->parent)
700 return &bdi->wb;
701
702 rcu_read_lock();
703 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
704 if (wb) {
705 struct cgroup_subsys_state *blkcg_css;
706
707 /* see whether the blkcg association has changed */
708 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
709 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
710 wb = NULL;
711 css_put(blkcg_css);
712 }
713 rcu_read_unlock();
714
715 return wb;
716 }
717
718 /**
719 * wb_get_create - get wb for a given memcg, create if necessary
720 * @bdi: target bdi
721 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
722 * @gfp: allocation mask to use
723 *
724 * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
725 * create one. See wb_get_lookup() for more details.
726 */
wb_get_create(struct backing_dev_info * bdi,struct cgroup_subsys_state * memcg_css,gfp_t gfp)727 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
728 struct cgroup_subsys_state *memcg_css,
729 gfp_t gfp)
730 {
731 struct bdi_writeback *wb;
732
733 might_alloc(gfp);
734
735 do {
736 wb = wb_get_lookup(bdi, memcg_css);
737 } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
738
739 return wb;
740 }
741
cgwb_bdi_init(struct backing_dev_info * bdi)742 static int cgwb_bdi_init(struct backing_dev_info *bdi)
743 {
744 int ret;
745
746 INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
747 mutex_init(&bdi->cgwb_release_mutex);
748 init_rwsem(&bdi->wb_switch_rwsem);
749
750 ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
751 if (!ret) {
752 bdi->wb.memcg_css = &root_mem_cgroup->css;
753 bdi->wb.blkcg_css = blkcg_root_css;
754 }
755 return ret;
756 }
757
cgwb_bdi_unregister(struct backing_dev_info * bdi)758 static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
759 {
760 struct radix_tree_iter iter;
761 void **slot;
762 struct bdi_writeback *wb;
763
764 WARN_ON(test_bit(WB_registered, &bdi->wb.state));
765
766 spin_lock_irq(&cgwb_lock);
767 radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
768 cgwb_kill(*slot);
769 spin_unlock_irq(&cgwb_lock);
770
771 mutex_lock(&bdi->cgwb_release_mutex);
772 spin_lock_irq(&cgwb_lock);
773 while (!list_empty(&bdi->wb_list)) {
774 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
775 bdi_node);
776 spin_unlock_irq(&cgwb_lock);
777 wb_shutdown(wb);
778 spin_lock_irq(&cgwb_lock);
779 }
780 spin_unlock_irq(&cgwb_lock);
781 mutex_unlock(&bdi->cgwb_release_mutex);
782 }
783
784 /*
785 * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
786 *
787 * Try to release dying cgwbs by switching attached inodes to the nearest
788 * living ancestor's writeback. Processed wbs are placed at the end
789 * of the list to guarantee the forward progress.
790 */
cleanup_offline_cgwbs_workfn(struct work_struct * work)791 static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
792 {
793 struct bdi_writeback *wb;
794 LIST_HEAD(processed);
795
796 spin_lock_irq(&cgwb_lock);
797
798 while (!list_empty(&offline_cgwbs)) {
799 wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
800 offline_node);
801 list_move(&wb->offline_node, &processed);
802
803 /*
804 * If wb is dirty, cleaning up the writeback by switching
805 * attached inodes will result in an effective removal of any
806 * bandwidth restrictions, which isn't the goal. Instead,
807 * it can be postponed until the next time, when all io
808 * will be likely completed. If in the meantime some inodes
809 * will get re-dirtied, they should be eventually switched to
810 * a new cgwb.
811 */
812 if (wb_has_dirty_io(wb))
813 continue;
814
815 if (!wb_tryget(wb))
816 continue;
817
818 spin_unlock_irq(&cgwb_lock);
819 while (cleanup_offline_cgwb(wb))
820 cond_resched();
821 spin_lock_irq(&cgwb_lock);
822
823 wb_put(wb);
824 }
825
826 if (!list_empty(&processed))
827 list_splice_tail(&processed, &offline_cgwbs);
828
829 spin_unlock_irq(&cgwb_lock);
830 }
831
832 /**
833 * wb_memcg_offline - kill all wb's associated with a memcg being offlined
834 * @memcg: memcg being offlined
835 *
836 * Also prevents creation of any new wb's associated with @memcg.
837 */
wb_memcg_offline(struct mem_cgroup * memcg)838 void wb_memcg_offline(struct mem_cgroup *memcg)
839 {
840 struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
841 struct bdi_writeback *wb, *next;
842
843 spin_lock_irq(&cgwb_lock);
844 list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
845 cgwb_kill(wb);
846 memcg_cgwb_list->next = NULL; /* prevent new wb's */
847 spin_unlock_irq(&cgwb_lock);
848
849 queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
850 }
851
852 /**
853 * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
854 * @css: blkcg being offlined
855 *
856 * Also prevents creation of any new wb's associated with @blkcg.
857 */
wb_blkcg_offline(struct cgroup_subsys_state * css)858 void wb_blkcg_offline(struct cgroup_subsys_state *css)
859 {
860 struct bdi_writeback *wb, *next;
861 struct list_head *list = blkcg_get_cgwb_list(css);
862
863 spin_lock_irq(&cgwb_lock);
864 list_for_each_entry_safe(wb, next, list, blkcg_node)
865 cgwb_kill(wb);
866 list->next = NULL; /* prevent new wb's */
867 spin_unlock_irq(&cgwb_lock);
868 }
869
cgwb_bdi_register(struct backing_dev_info * bdi)870 static void cgwb_bdi_register(struct backing_dev_info *bdi)
871 {
872 spin_lock_irq(&cgwb_lock);
873 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
874 spin_unlock_irq(&cgwb_lock);
875 }
876
cgwb_init(void)877 static int __init cgwb_init(void)
878 {
879 /*
880 * There can be many concurrent release work items overwhelming
881 * system_wq. Put them in a separate wq and limit concurrency.
882 * There's no point in executing many of these in parallel.
883 */
884 cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
885 if (!cgwb_release_wq)
886 return -ENOMEM;
887
888 return 0;
889 }
890 subsys_initcall(cgwb_init);
891
892 #else /* CONFIG_CGROUP_WRITEBACK */
893
cgwb_bdi_init(struct backing_dev_info * bdi)894 static int cgwb_bdi_init(struct backing_dev_info *bdi)
895 {
896 return wb_init(&bdi->wb, bdi, GFP_KERNEL);
897 }
898
cgwb_bdi_unregister(struct backing_dev_info * bdi)899 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
900
cgwb_bdi_register(struct backing_dev_info * bdi)901 static void cgwb_bdi_register(struct backing_dev_info *bdi)
902 {
903 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
904 }
905
cgwb_remove_from_bdi_list(struct bdi_writeback * wb)906 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
907 {
908 list_del_rcu(&wb->bdi_node);
909 }
910
911 #endif /* CONFIG_CGROUP_WRITEBACK */
912
bdi_init(struct backing_dev_info * bdi)913 int bdi_init(struct backing_dev_info *bdi)
914 {
915 bdi->dev = NULL;
916
917 kref_init(&bdi->refcnt);
918 bdi->min_ratio = 0;
919 bdi->max_ratio = 100 * BDI_RATIO_SCALE;
920 bdi->max_prop_frac = FPROP_FRAC_BASE;
921 INIT_LIST_HEAD(&bdi->bdi_list);
922 INIT_LIST_HEAD(&bdi->wb_list);
923 init_waitqueue_head(&bdi->wb_waitq);
924
925 return cgwb_bdi_init(bdi);
926 }
927
bdi_alloc(int node_id)928 struct backing_dev_info *bdi_alloc(int node_id)
929 {
930 struct backing_dev_info *bdi;
931
932 bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
933 if (!bdi)
934 return NULL;
935
936 if (bdi_init(bdi)) {
937 kfree(bdi);
938 return NULL;
939 }
940 bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
941 bdi->ra_pages = VM_READAHEAD_PAGES;
942 bdi->io_pages = VM_READAHEAD_PAGES;
943 timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
944 return bdi;
945 }
946 EXPORT_SYMBOL(bdi_alloc);
947
bdi_lookup_rb_node(u64 id,struct rb_node ** parentp)948 static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
949 {
950 struct rb_node **p = &bdi_tree.rb_node;
951 struct rb_node *parent = NULL;
952 struct backing_dev_info *bdi;
953
954 lockdep_assert_held(&bdi_lock);
955
956 while (*p) {
957 parent = *p;
958 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
959
960 if (bdi->id > id)
961 p = &(*p)->rb_left;
962 else if (bdi->id < id)
963 p = &(*p)->rb_right;
964 else
965 break;
966 }
967
968 if (parentp)
969 *parentp = parent;
970 return p;
971 }
972
973 /**
974 * bdi_get_by_id - lookup and get bdi from its id
975 * @id: bdi id to lookup
976 *
977 * Find bdi matching @id and get it. Returns NULL if the matching bdi
978 * doesn't exist or is already unregistered.
979 */
bdi_get_by_id(u64 id)980 struct backing_dev_info *bdi_get_by_id(u64 id)
981 {
982 struct backing_dev_info *bdi = NULL;
983 struct rb_node **p;
984
985 spin_lock_bh(&bdi_lock);
986 p = bdi_lookup_rb_node(id, NULL);
987 if (*p) {
988 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
989 bdi_get(bdi);
990 }
991 spin_unlock_bh(&bdi_lock);
992
993 return bdi;
994 }
995
bdi_register_va(struct backing_dev_info * bdi,const char * fmt,va_list args)996 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
997 {
998 struct device *dev;
999 struct rb_node *parent, **p;
1000
1001 if (bdi->dev) /* The driver needs to use separate queues per device */
1002 return 0;
1003
1004 vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
1005 dev = device_create(&bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
1006 if (IS_ERR(dev))
1007 return PTR_ERR(dev);
1008
1009 cgwb_bdi_register(bdi);
1010 bdi->dev = dev;
1011
1012 bdi_debug_register(bdi, dev_name(dev));
1013 set_bit(WB_registered, &bdi->wb.state);
1014
1015 spin_lock_bh(&bdi_lock);
1016
1017 bdi->id = ++bdi_id_cursor;
1018
1019 p = bdi_lookup_rb_node(bdi->id, &parent);
1020 rb_link_node(&bdi->rb_node, parent, p);
1021 rb_insert_color(&bdi->rb_node, &bdi_tree);
1022
1023 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
1024
1025 spin_unlock_bh(&bdi_lock);
1026
1027 trace_writeback_bdi_register(bdi);
1028 return 0;
1029 }
1030
bdi_register(struct backing_dev_info * bdi,const char * fmt,...)1031 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
1032 {
1033 va_list args;
1034 int ret;
1035
1036 va_start(args, fmt);
1037 ret = bdi_register_va(bdi, fmt, args);
1038 va_end(args);
1039 return ret;
1040 }
1041 EXPORT_SYMBOL(bdi_register);
1042
bdi_set_owner(struct backing_dev_info * bdi,struct device * owner)1043 void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
1044 {
1045 WARN_ON_ONCE(bdi->owner);
1046 bdi->owner = owner;
1047 get_device(owner);
1048 }
1049
1050 /*
1051 * Remove bdi from bdi_list, and ensure that it is no longer visible
1052 */
bdi_remove_from_list(struct backing_dev_info * bdi)1053 static void bdi_remove_from_list(struct backing_dev_info *bdi)
1054 {
1055 spin_lock_bh(&bdi_lock);
1056 rb_erase(&bdi->rb_node, &bdi_tree);
1057 list_del_rcu(&bdi->bdi_list);
1058 spin_unlock_bh(&bdi_lock);
1059
1060 synchronize_rcu_expedited();
1061 }
1062
bdi_unregister(struct backing_dev_info * bdi)1063 void bdi_unregister(struct backing_dev_info *bdi)
1064 {
1065 del_timer_sync(&bdi->laptop_mode_wb_timer);
1066
1067 /* make sure nobody finds us on the bdi_list anymore */
1068 bdi_remove_from_list(bdi);
1069 wb_shutdown(&bdi->wb);
1070 cgwb_bdi_unregister(bdi);
1071
1072 /*
1073 * If this BDI's min ratio has been set, use bdi_set_min_ratio() to
1074 * update the global bdi_min_ratio.
1075 */
1076 if (bdi->min_ratio)
1077 bdi_set_min_ratio(bdi, 0);
1078
1079 if (bdi->dev) {
1080 bdi_debug_unregister(bdi);
1081 device_unregister(bdi->dev);
1082 bdi->dev = NULL;
1083 }
1084
1085 if (bdi->owner) {
1086 put_device(bdi->owner);
1087 bdi->owner = NULL;
1088 }
1089 }
1090 EXPORT_SYMBOL(bdi_unregister);
1091
release_bdi(struct kref * ref)1092 static void release_bdi(struct kref *ref)
1093 {
1094 struct backing_dev_info *bdi =
1095 container_of(ref, struct backing_dev_info, refcnt);
1096
1097 WARN_ON_ONCE(test_bit(WB_registered, &bdi->wb.state));
1098 WARN_ON_ONCE(bdi->dev);
1099 wb_exit(&bdi->wb);
1100 kfree(bdi);
1101 }
1102
bdi_put(struct backing_dev_info * bdi)1103 void bdi_put(struct backing_dev_info *bdi)
1104 {
1105 kref_put(&bdi->refcnt, release_bdi);
1106 }
1107 EXPORT_SYMBOL(bdi_put);
1108
inode_to_bdi(struct inode * inode)1109 struct backing_dev_info *inode_to_bdi(struct inode *inode)
1110 {
1111 struct super_block *sb;
1112
1113 if (!inode)
1114 return &noop_backing_dev_info;
1115
1116 sb = inode->i_sb;
1117 #ifdef CONFIG_BLOCK
1118 if (sb_is_blkdev_sb(sb))
1119 return I_BDEV(inode)->bd_disk->bdi;
1120 #endif
1121 return sb->s_bdi;
1122 }
1123 EXPORT_SYMBOL(inode_to_bdi);
1124
bdi_dev_name(struct backing_dev_info * bdi)1125 const char *bdi_dev_name(struct backing_dev_info *bdi)
1126 {
1127 if (!bdi || !bdi->dev)
1128 return bdi_unknown_name;
1129 return bdi->dev_name;
1130 }
1131 EXPORT_SYMBOL_GPL(bdi_dev_name);
1132
