1 // SPDX-License-Identifier: GPL-2.0-only
2
3 #include <linux/wait.h>
4 #include <linux/rbtree.h>
5 #include <linux/kthread.h>
6 #include <linux/backing-dev.h>
7 #include <linux/blk-cgroup.h>
8 #include <linux/freezer.h>
9 #include <linux/fs.h>
10 #include <linux/pagemap.h>
11 #include <linux/mm.h>
12 #include <linux/sched/mm.h>
13 #include <linux/sched.h>
14 #include <linux/module.h>
15 #include <linux/writeback.h>
16 #include <linux/device.h>
17 #include <trace/events/writeback.h>
18
19 struct backing_dev_info noop_backing_dev_info;
20 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
21
22 static struct class *bdi_class;
23 static const char *bdi_unknown_name = "(unknown)";
24
25 /*
26 * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
27 * reader side locking.
28 */
29 DEFINE_SPINLOCK(bdi_lock);
30 static u64 bdi_id_cursor;
31 static struct rb_root bdi_tree = RB_ROOT;
32 LIST_HEAD(bdi_list);
33
34 /* bdi_wq serves all asynchronous writeback tasks */
35 struct workqueue_struct *bdi_wq;
36
37 #define K(x) ((x) << (PAGE_SHIFT - 10))
38
39 #ifdef CONFIG_DEBUG_FS
40 #include <linux/debugfs.h>
41 #include <linux/seq_file.h>
42
43 static struct dentry *bdi_debug_root;
44
bdi_debug_init(void)45 static void bdi_debug_init(void)
46 {
47 bdi_debug_root = debugfs_create_dir("bdi", NULL);
48 }
49
bdi_debug_stats_show(struct seq_file * m,void * v)50 static int bdi_debug_stats_show(struct seq_file *m, void *v)
51 {
52 struct backing_dev_info *bdi = m->private;
53 struct bdi_writeback *wb = &bdi->wb;
54 unsigned long background_thresh;
55 unsigned long dirty_thresh;
56 unsigned long wb_thresh;
57 unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
58 struct inode *inode;
59
60 nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
61 spin_lock(&wb->list_lock);
62 list_for_each_entry(inode, &wb->b_dirty, i_io_list)
63 nr_dirty++;
64 list_for_each_entry(inode, &wb->b_io, i_io_list)
65 nr_io++;
66 list_for_each_entry(inode, &wb->b_more_io, i_io_list)
67 nr_more_io++;
68 list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
69 if (inode->i_state & I_DIRTY_TIME)
70 nr_dirty_time++;
71 spin_unlock(&wb->list_lock);
72
73 global_dirty_limits(&background_thresh, &dirty_thresh);
74 wb_thresh = wb_calc_thresh(wb, dirty_thresh);
75
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
105 return 0;
106 }
107 DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
108
bdi_debug_register(struct backing_dev_info * bdi,const char * name)109 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
110 {
111 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
112
113 debugfs_create_file("stats", 0444, bdi->debug_dir, bdi,
114 &bdi_debug_stats_fops);
115 }
116
bdi_debug_unregister(struct backing_dev_info * bdi)117 static void bdi_debug_unregister(struct backing_dev_info *bdi)
118 {
119 debugfs_remove_recursive(bdi->debug_dir);
120 }
121 #else
bdi_debug_init(void)122 static inline void bdi_debug_init(void)
123 {
124 }
bdi_debug_register(struct backing_dev_info * bdi,const char * name)125 static inline void bdi_debug_register(struct backing_dev_info *bdi,
126 const char *name)
127 {
128 }
bdi_debug_unregister(struct backing_dev_info * bdi)129 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
130 {
131 }
132 #endif
133
read_ahead_kb_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)134 static ssize_t read_ahead_kb_store(struct device *dev,
135 struct device_attribute *attr,
136 const char *buf, size_t count)
137 {
138 struct backing_dev_info *bdi = dev_get_drvdata(dev);
139 unsigned long read_ahead_kb;
140 ssize_t ret;
141
142 ret = kstrtoul(buf, 10, &read_ahead_kb);
143 if (ret < 0)
144 return ret;
145
146 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
147
148 return count;
149 }
150
151 #define BDI_SHOW(name, expr) \
152 static ssize_t name##_show(struct device *dev, \
153 struct device_attribute *attr, char *buf) \
154 { \
155 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
156 \
157 return sysfs_emit(buf, "%lld\n", (long long)expr); \
158 } \
159 static DEVICE_ATTR_RW(name);
160
161 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
162
min_ratio_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)163 static ssize_t min_ratio_store(struct device *dev,
164 struct device_attribute *attr, const char *buf, size_t count)
165 {
166 struct backing_dev_info *bdi = dev_get_drvdata(dev);
167 unsigned int ratio;
168 ssize_t ret;
169
170 ret = kstrtouint(buf, 10, &ratio);
171 if (ret < 0)
172 return ret;
173
174 ret = bdi_set_min_ratio(bdi, ratio);
175 if (!ret)
176 ret = count;
177
178 return ret;
179 }
180 BDI_SHOW(min_ratio, bdi->min_ratio)
181
max_ratio_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)182 static ssize_t max_ratio_store(struct device *dev,
183 struct device_attribute *attr, const char *buf, size_t count)
184 {
185 struct backing_dev_info *bdi = dev_get_drvdata(dev);
186 unsigned int ratio;
187 ssize_t ret;
188
189 ret = kstrtouint(buf, 10, &ratio);
190 if (ret < 0)
191 return ret;
192
193 ret = bdi_set_max_ratio(bdi, ratio);
194 if (!ret)
195 ret = count;
196
197 return ret;
198 }
199 BDI_SHOW(max_ratio, bdi->max_ratio)
200
stable_pages_required_show(struct device * dev,struct device_attribute * attr,char * buf)201 static ssize_t stable_pages_required_show(struct device *dev,
202 struct device_attribute *attr,
203 char *buf)
204 {
205 dev_warn_once(dev,
206 "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n");
207 return sysfs_emit(buf, "%d\n", 0);
208 }
209 static DEVICE_ATTR_RO(stable_pages_required);
210
211 static struct attribute *bdi_dev_attrs[] = {
212 &dev_attr_read_ahead_kb.attr,
213 &dev_attr_min_ratio.attr,
214 &dev_attr_max_ratio.attr,
215 &dev_attr_stable_pages_required.attr,
216 NULL,
217 };
218 ATTRIBUTE_GROUPS(bdi_dev);
219
bdi_class_init(void)220 static __init int bdi_class_init(void)
221 {
222 bdi_class = class_create(THIS_MODULE, "bdi");
223 if (IS_ERR(bdi_class))
224 return PTR_ERR(bdi_class);
225
226 bdi_class->dev_groups = bdi_dev_groups;
227 bdi_debug_init();
228
229 return 0;
230 }
231 postcore_initcall(bdi_class_init);
232
233 static int bdi_init(struct backing_dev_info *bdi);
234
default_bdi_init(void)235 static int __init default_bdi_init(void)
236 {
237 int err;
238
239 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
240 WQ_SYSFS, 0);
241 if (!bdi_wq)
242 return -ENOMEM;
243
244 err = bdi_init(&noop_backing_dev_info);
245
246 return err;
247 }
248 subsys_initcall(default_bdi_init);
249
250 /*
251 * This function is used when the first inode for this wb is marked dirty. It
252 * wakes-up the corresponding bdi thread which should then take care of the
253 * periodic background write-out of dirty inodes. Since the write-out would
254 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
255 * set up a timer which wakes the bdi thread up later.
256 *
257 * Note, we wouldn't bother setting up the timer, but this function is on the
258 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
259 * by delaying the wake-up.
260 *
261 * We have to be careful not to postpone flush work if it is scheduled for
262 * earlier. Thus we use queue_delayed_work().
263 */
wb_wakeup_delayed(struct bdi_writeback * wb)264 void wb_wakeup_delayed(struct bdi_writeback *wb)
265 {
266 unsigned long timeout;
267
268 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
269 spin_lock_bh(&wb->work_lock);
270 if (test_bit(WB_registered, &wb->state))
271 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
272 spin_unlock_bh(&wb->work_lock);
273 }
274
wb_update_bandwidth_workfn(struct work_struct * work)275 static void wb_update_bandwidth_workfn(struct work_struct *work)
276 {
277 struct bdi_writeback *wb = container_of(to_delayed_work(work),
278 struct bdi_writeback, bw_dwork);
279
280 wb_update_bandwidth(wb);
281 }
282
283 /*
284 * Initial write bandwidth: 100 MB/s
285 */
286 #define INIT_BW (100 << (20 - PAGE_SHIFT))
287
wb_init(struct bdi_writeback * wb,struct backing_dev_info * bdi,gfp_t gfp)288 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
289 gfp_t gfp)
290 {
291 int i, err;
292
293 memset(wb, 0, sizeof(*wb));
294
295 wb->bdi = bdi;
296 wb->last_old_flush = jiffies;
297 INIT_LIST_HEAD(&wb->b_dirty);
298 INIT_LIST_HEAD(&wb->b_io);
299 INIT_LIST_HEAD(&wb->b_more_io);
300 INIT_LIST_HEAD(&wb->b_dirty_time);
301 spin_lock_init(&wb->list_lock);
302
303 atomic_set(&wb->writeback_inodes, 0);
304 wb->bw_time_stamp = jiffies;
305 wb->balanced_dirty_ratelimit = INIT_BW;
306 wb->dirty_ratelimit = INIT_BW;
307 wb->write_bandwidth = INIT_BW;
308 wb->avg_write_bandwidth = INIT_BW;
309
310 spin_lock_init(&wb->work_lock);
311 INIT_LIST_HEAD(&wb->work_list);
312 INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
313 INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn);
314 wb->dirty_sleep = jiffies;
315
316 err = fprop_local_init_percpu(&wb->completions, gfp);
317 if (err)
318 return err;
319
320 for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
321 err = percpu_counter_init(&wb->stat[i], 0, gfp);
322 if (err)
323 goto out_destroy_stat;
324 }
325
326 return 0;
327
328 out_destroy_stat:
329 while (i--)
330 percpu_counter_destroy(&wb->stat[i]);
331 fprop_local_destroy_percpu(&wb->completions);
332 return err;
333 }
334
335 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
336
337 /*
338 * Remove bdi from the global list and shutdown any threads we have running
339 */
wb_shutdown(struct bdi_writeback * wb)340 static void wb_shutdown(struct bdi_writeback *wb)
341 {
342 /* Make sure nobody queues further work */
343 spin_lock_bh(&wb->work_lock);
344 if (!test_and_clear_bit(WB_registered, &wb->state)) {
345 spin_unlock_bh(&wb->work_lock);
346 return;
347 }
348 spin_unlock_bh(&wb->work_lock);
349
350 cgwb_remove_from_bdi_list(wb);
351 /*
352 * Drain work list and shutdown the delayed_work. !WB_registered
353 * tells wb_workfn() that @wb is dying and its work_list needs to
354 * be drained no matter what.
355 */
356 mod_delayed_work(bdi_wq, &wb->dwork, 0);
357 flush_delayed_work(&wb->dwork);
358 WARN_ON(!list_empty(&wb->work_list));
359 flush_delayed_work(&wb->bw_dwork);
360 }
361
wb_exit(struct bdi_writeback * wb)362 static void wb_exit(struct bdi_writeback *wb)
363 {
364 int i;
365
366 WARN_ON(delayed_work_pending(&wb->dwork));
367
368 for (i = 0; i < NR_WB_STAT_ITEMS; i++)
369 percpu_counter_destroy(&wb->stat[i]);
370
371 fprop_local_destroy_percpu(&wb->completions);
372 }
373
374 #ifdef CONFIG_CGROUP_WRITEBACK
375
376 #include <linux/memcontrol.h>
377
378 /*
379 * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
380 * memcg->cgwb_list. bdi->cgwb_tree is also RCU protected.
381 */
382 static DEFINE_SPINLOCK(cgwb_lock);
383 static struct workqueue_struct *cgwb_release_wq;
384
385 static LIST_HEAD(offline_cgwbs);
386 static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
387 static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
388
cgwb_release_workfn(struct work_struct * work)389 static void cgwb_release_workfn(struct work_struct *work)
390 {
391 struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
392 release_work);
393 struct blkcg *blkcg = css_to_blkcg(wb->blkcg_css);
394 struct backing_dev_info *bdi = wb->bdi;
395
396 mutex_lock(&wb->bdi->cgwb_release_mutex);
397 wb_shutdown(wb);
398
399 css_put(wb->memcg_css);
400 css_put(wb->blkcg_css);
401 mutex_unlock(&wb->bdi->cgwb_release_mutex);
402
403 /* triggers blkg destruction if no online users left */
404 blkcg_unpin_online(blkcg);
405
406 fprop_local_destroy_percpu(&wb->memcg_completions);
407
408 spin_lock_irq(&cgwb_lock);
409 list_del(&wb->offline_node);
410 spin_unlock_irq(&cgwb_lock);
411
412 percpu_ref_exit(&wb->refcnt);
413 wb_exit(wb);
414 bdi_put(bdi);
415 WARN_ON_ONCE(!list_empty(&wb->b_attached));
416 kfree_rcu(wb, rcu);
417 }
418
cgwb_release(struct percpu_ref * refcnt)419 static void cgwb_release(struct percpu_ref *refcnt)
420 {
421 struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
422 refcnt);
423 queue_work(cgwb_release_wq, &wb->release_work);
424 }
425
cgwb_kill(struct bdi_writeback * wb)426 static void cgwb_kill(struct bdi_writeback *wb)
427 {
428 lockdep_assert_held(&cgwb_lock);
429
430 WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
431 list_del(&wb->memcg_node);
432 list_del(&wb->blkcg_node);
433 list_add(&wb->offline_node, &offline_cgwbs);
434 percpu_ref_kill(&wb->refcnt);
435 }
436
cgwb_remove_from_bdi_list(struct bdi_writeback * wb)437 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
438 {
439 spin_lock_irq(&cgwb_lock);
440 list_del_rcu(&wb->bdi_node);
441 spin_unlock_irq(&cgwb_lock);
442 }
443
cgwb_create(struct backing_dev_info * bdi,struct cgroup_subsys_state * memcg_css,gfp_t gfp)444 static int cgwb_create(struct backing_dev_info *bdi,
445 struct cgroup_subsys_state *memcg_css, gfp_t gfp)
446 {
447 struct mem_cgroup *memcg;
448 struct cgroup_subsys_state *blkcg_css;
449 struct blkcg *blkcg;
450 struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
451 struct bdi_writeback *wb;
452 unsigned long flags;
453 int ret = 0;
454
455 memcg = mem_cgroup_from_css(memcg_css);
456 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
457 blkcg = css_to_blkcg(blkcg_css);
458 memcg_cgwb_list = &memcg->cgwb_list;
459 blkcg_cgwb_list = &blkcg->cgwb_list;
460
461 /* look up again under lock and discard on blkcg mismatch */
462 spin_lock_irqsave(&cgwb_lock, flags);
463 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
464 if (wb && wb->blkcg_css != blkcg_css) {
465 cgwb_kill(wb);
466 wb = NULL;
467 }
468 spin_unlock_irqrestore(&cgwb_lock, flags);
469 if (wb)
470 goto out_put;
471
472 /* need to create a new one */
473 wb = kmalloc(sizeof(*wb), gfp);
474 if (!wb) {
475 ret = -ENOMEM;
476 goto out_put;
477 }
478
479 ret = wb_init(wb, bdi, gfp);
480 if (ret)
481 goto err_free;
482
483 ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
484 if (ret)
485 goto err_wb_exit;
486
487 ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
488 if (ret)
489 goto err_ref_exit;
490
491 wb->memcg_css = memcg_css;
492 wb->blkcg_css = blkcg_css;
493 INIT_LIST_HEAD(&wb->b_attached);
494 INIT_WORK(&wb->release_work, cgwb_release_workfn);
495 set_bit(WB_registered, &wb->state);
496 bdi_get(bdi);
497
498 /*
499 * The root wb determines the registered state of the whole bdi and
500 * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
501 * whether they're still online. Don't link @wb if any is dead.
502 * See wb_memcg_offline() and wb_blkcg_offline().
503 */
504 ret = -ENODEV;
505 spin_lock_irqsave(&cgwb_lock, flags);
506 if (test_bit(WB_registered, &bdi->wb.state) &&
507 blkcg_cgwb_list->next && memcg_cgwb_list->next) {
508 /* we might have raced another instance of this function */
509 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
510 if (!ret) {
511 list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
512 list_add(&wb->memcg_node, memcg_cgwb_list);
513 list_add(&wb->blkcg_node, blkcg_cgwb_list);
514 blkcg_pin_online(blkcg);
515 css_get(memcg_css);
516 css_get(blkcg_css);
517 }
518 }
519 spin_unlock_irqrestore(&cgwb_lock, flags);
520 if (ret) {
521 if (ret == -EEXIST)
522 ret = 0;
523 goto err_fprop_exit;
524 }
525 goto out_put;
526
527 err_fprop_exit:
528 bdi_put(bdi);
529 fprop_local_destroy_percpu(&wb->memcg_completions);
530 err_ref_exit:
531 percpu_ref_exit(&wb->refcnt);
532 err_wb_exit:
533 wb_exit(wb);
534 err_free:
535 kfree(wb);
536 out_put:
537 css_put(blkcg_css);
538 return ret;
539 }
540
541 /**
542 * wb_get_lookup - get wb for a given memcg
543 * @bdi: target bdi
544 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
545 *
546 * Try to get the wb for @memcg_css on @bdi. The returned wb has its
547 * refcount incremented.
548 *
549 * This function uses css_get() on @memcg_css and thus expects its refcnt
550 * to be positive on invocation. IOW, rcu_read_lock() protection on
551 * @memcg_css isn't enough. try_get it before calling this function.
552 *
553 * A wb is keyed by its associated memcg. As blkcg implicitly enables
554 * memcg on the default hierarchy, memcg association is guaranteed to be
555 * more specific (equal or descendant to the associated blkcg) and thus can
556 * identify both the memcg and blkcg associations.
557 *
558 * Because the blkcg associated with a memcg may change as blkcg is enabled
559 * and disabled closer to root in the hierarchy, each wb keeps track of
560 * both the memcg and blkcg associated with it and verifies the blkcg on
561 * each lookup. On mismatch, the existing wb is discarded and a new one is
562 * created.
563 */
wb_get_lookup(struct backing_dev_info * bdi,struct cgroup_subsys_state * memcg_css)564 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
565 struct cgroup_subsys_state *memcg_css)
566 {
567 struct bdi_writeback *wb;
568
569 if (!memcg_css->parent)
570 return &bdi->wb;
571
572 rcu_read_lock();
573 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
574 if (wb) {
575 struct cgroup_subsys_state *blkcg_css;
576
577 /* see whether the blkcg association has changed */
578 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
579 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
580 wb = NULL;
581 css_put(blkcg_css);
582 }
583 rcu_read_unlock();
584
585 return wb;
586 }
587
588 /**
589 * wb_get_create - get wb for a given memcg, create if necessary
590 * @bdi: target bdi
591 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
592 * @gfp: allocation mask to use
593 *
594 * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
595 * create one. See wb_get_lookup() for more details.
596 */
wb_get_create(struct backing_dev_info * bdi,struct cgroup_subsys_state * memcg_css,gfp_t gfp)597 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
598 struct cgroup_subsys_state *memcg_css,
599 gfp_t gfp)
600 {
601 struct bdi_writeback *wb;
602
603 might_alloc(gfp);
604
605 if (!memcg_css->parent)
606 return &bdi->wb;
607
608 do {
609 wb = wb_get_lookup(bdi, memcg_css);
610 } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
611
612 return wb;
613 }
614
cgwb_bdi_init(struct backing_dev_info * bdi)615 static int cgwb_bdi_init(struct backing_dev_info *bdi)
616 {
617 int ret;
618
619 INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
620 mutex_init(&bdi->cgwb_release_mutex);
621 init_rwsem(&bdi->wb_switch_rwsem);
622
623 ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
624 if (!ret) {
625 bdi->wb.memcg_css = &root_mem_cgroup->css;
626 bdi->wb.blkcg_css = blkcg_root_css;
627 }
628 return ret;
629 }
630
cgwb_bdi_unregister(struct backing_dev_info * bdi)631 static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
632 {
633 struct radix_tree_iter iter;
634 void **slot;
635 struct bdi_writeback *wb;
636
637 WARN_ON(test_bit(WB_registered, &bdi->wb.state));
638
639 spin_lock_irq(&cgwb_lock);
640 radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
641 cgwb_kill(*slot);
642 spin_unlock_irq(&cgwb_lock);
643
644 mutex_lock(&bdi->cgwb_release_mutex);
645 spin_lock_irq(&cgwb_lock);
646 while (!list_empty(&bdi->wb_list)) {
647 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
648 bdi_node);
649 spin_unlock_irq(&cgwb_lock);
650 wb_shutdown(wb);
651 spin_lock_irq(&cgwb_lock);
652 }
653 spin_unlock_irq(&cgwb_lock);
654 mutex_unlock(&bdi->cgwb_release_mutex);
655 }
656
657 /*
658 * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
659 *
660 * Try to release dying cgwbs by switching attached inodes to the nearest
661 * living ancestor's writeback. Processed wbs are placed at the end
662 * of the list to guarantee the forward progress.
663 */
cleanup_offline_cgwbs_workfn(struct work_struct * work)664 static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
665 {
666 struct bdi_writeback *wb;
667 LIST_HEAD(processed);
668
669 spin_lock_irq(&cgwb_lock);
670
671 while (!list_empty(&offline_cgwbs)) {
672 wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
673 offline_node);
674 list_move(&wb->offline_node, &processed);
675
676 /*
677 * If wb is dirty, cleaning up the writeback by switching
678 * attached inodes will result in an effective removal of any
679 * bandwidth restrictions, which isn't the goal. Instead,
680 * it can be postponed until the next time, when all io
681 * will be likely completed. If in the meantime some inodes
682 * will get re-dirtied, they should be eventually switched to
683 * a new cgwb.
684 */
685 if (wb_has_dirty_io(wb))
686 continue;
687
688 if (!wb_tryget(wb))
689 continue;
690
691 spin_unlock_irq(&cgwb_lock);
692 while (cleanup_offline_cgwb(wb))
693 cond_resched();
694 spin_lock_irq(&cgwb_lock);
695
696 wb_put(wb);
697 }
698
699 if (!list_empty(&processed))
700 list_splice_tail(&processed, &offline_cgwbs);
701
702 spin_unlock_irq(&cgwb_lock);
703 }
704
705 /**
706 * wb_memcg_offline - kill all wb's associated with a memcg being offlined
707 * @memcg: memcg being offlined
708 *
709 * Also prevents creation of any new wb's associated with @memcg.
710 */
wb_memcg_offline(struct mem_cgroup * memcg)711 void wb_memcg_offline(struct mem_cgroup *memcg)
712 {
713 struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
714 struct bdi_writeback *wb, *next;
715
716 spin_lock_irq(&cgwb_lock);
717 list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
718 cgwb_kill(wb);
719 memcg_cgwb_list->next = NULL; /* prevent new wb's */
720 spin_unlock_irq(&cgwb_lock);
721
722 queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
723 }
724
725 /**
726 * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
727 * @blkcg: blkcg being offlined
728 *
729 * Also prevents creation of any new wb's associated with @blkcg.
730 */
wb_blkcg_offline(struct blkcg * blkcg)731 void wb_blkcg_offline(struct blkcg *blkcg)
732 {
733 struct bdi_writeback *wb, *next;
734
735 spin_lock_irq(&cgwb_lock);
736 list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node)
737 cgwb_kill(wb);
738 blkcg->cgwb_list.next = NULL; /* prevent new wb's */
739 spin_unlock_irq(&cgwb_lock);
740 }
741
cgwb_bdi_register(struct backing_dev_info * bdi)742 static void cgwb_bdi_register(struct backing_dev_info *bdi)
743 {
744 spin_lock_irq(&cgwb_lock);
745 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
746 spin_unlock_irq(&cgwb_lock);
747 }
748
cgwb_init(void)749 static int __init cgwb_init(void)
750 {
751 /*
752 * There can be many concurrent release work items overwhelming
753 * system_wq. Put them in a separate wq and limit concurrency.
754 * There's no point in executing many of these in parallel.
755 */
756 cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
757 if (!cgwb_release_wq)
758 return -ENOMEM;
759
760 return 0;
761 }
762 subsys_initcall(cgwb_init);
763
764 #else /* CONFIG_CGROUP_WRITEBACK */
765
cgwb_bdi_init(struct backing_dev_info * bdi)766 static int cgwb_bdi_init(struct backing_dev_info *bdi)
767 {
768 return wb_init(&bdi->wb, bdi, GFP_KERNEL);
769 }
770
cgwb_bdi_unregister(struct backing_dev_info * bdi)771 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
772
cgwb_bdi_register(struct backing_dev_info * bdi)773 static void cgwb_bdi_register(struct backing_dev_info *bdi)
774 {
775 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
776 }
777
cgwb_remove_from_bdi_list(struct bdi_writeback * wb)778 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
779 {
780 list_del_rcu(&wb->bdi_node);
781 }
782
783 #endif /* CONFIG_CGROUP_WRITEBACK */
784
bdi_init(struct backing_dev_info * bdi)785 static int bdi_init(struct backing_dev_info *bdi)
786 {
787 int ret;
788
789 bdi->dev = NULL;
790
791 kref_init(&bdi->refcnt);
792 bdi->min_ratio = 0;
793 bdi->max_ratio = 100;
794 bdi->max_prop_frac = FPROP_FRAC_BASE;
795 INIT_LIST_HEAD(&bdi->bdi_list);
796 INIT_LIST_HEAD(&bdi->wb_list);
797 init_waitqueue_head(&bdi->wb_waitq);
798
799 ret = cgwb_bdi_init(bdi);
800
801 return ret;
802 }
803
bdi_alloc(int node_id)804 struct backing_dev_info *bdi_alloc(int node_id)
805 {
806 struct backing_dev_info *bdi;
807
808 bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
809 if (!bdi)
810 return NULL;
811
812 if (bdi_init(bdi)) {
813 kfree(bdi);
814 return NULL;
815 }
816 bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
817 bdi->ra_pages = VM_READAHEAD_PAGES;
818 bdi->io_pages = VM_READAHEAD_PAGES;
819 timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
820 return bdi;
821 }
822 EXPORT_SYMBOL(bdi_alloc);
823
bdi_lookup_rb_node(u64 id,struct rb_node ** parentp)824 static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
825 {
826 struct rb_node **p = &bdi_tree.rb_node;
827 struct rb_node *parent = NULL;
828 struct backing_dev_info *bdi;
829
830 lockdep_assert_held(&bdi_lock);
831
832 while (*p) {
833 parent = *p;
834 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
835
836 if (bdi->id > id)
837 p = &(*p)->rb_left;
838 else if (bdi->id < id)
839 p = &(*p)->rb_right;
840 else
841 break;
842 }
843
844 if (parentp)
845 *parentp = parent;
846 return p;
847 }
848
849 /**
850 * bdi_get_by_id - lookup and get bdi from its id
851 * @id: bdi id to lookup
852 *
853 * Find bdi matching @id and get it. Returns NULL if the matching bdi
854 * doesn't exist or is already unregistered.
855 */
bdi_get_by_id(u64 id)856 struct backing_dev_info *bdi_get_by_id(u64 id)
857 {
858 struct backing_dev_info *bdi = NULL;
859 struct rb_node **p;
860
861 spin_lock_bh(&bdi_lock);
862 p = bdi_lookup_rb_node(id, NULL);
863 if (*p) {
864 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
865 bdi_get(bdi);
866 }
867 spin_unlock_bh(&bdi_lock);
868
869 return bdi;
870 }
871
bdi_register_va(struct backing_dev_info * bdi,const char * fmt,va_list args)872 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
873 {
874 struct device *dev;
875 struct rb_node *parent, **p;
876
877 if (bdi->dev) /* The driver needs to use separate queues per device */
878 return 0;
879
880 vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
881 dev = device_create(bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
882 if (IS_ERR(dev))
883 return PTR_ERR(dev);
884
885 cgwb_bdi_register(bdi);
886 bdi->dev = dev;
887
888 bdi_debug_register(bdi, dev_name(dev));
889 set_bit(WB_registered, &bdi->wb.state);
890
891 spin_lock_bh(&bdi_lock);
892
893 bdi->id = ++bdi_id_cursor;
894
895 p = bdi_lookup_rb_node(bdi->id, &parent);
896 rb_link_node(&bdi->rb_node, parent, p);
897 rb_insert_color(&bdi->rb_node, &bdi_tree);
898
899 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
900
901 spin_unlock_bh(&bdi_lock);
902
903 trace_writeback_bdi_register(bdi);
904 return 0;
905 }
906
bdi_register(struct backing_dev_info * bdi,const char * fmt,...)907 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
908 {
909 va_list args;
910 int ret;
911
912 va_start(args, fmt);
913 ret = bdi_register_va(bdi, fmt, args);
914 va_end(args);
915 return ret;
916 }
917 EXPORT_SYMBOL(bdi_register);
918
bdi_set_owner(struct backing_dev_info * bdi,struct device * owner)919 void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
920 {
921 WARN_ON_ONCE(bdi->owner);
922 bdi->owner = owner;
923 get_device(owner);
924 }
925
926 /*
927 * Remove bdi from bdi_list, and ensure that it is no longer visible
928 */
bdi_remove_from_list(struct backing_dev_info * bdi)929 static void bdi_remove_from_list(struct backing_dev_info *bdi)
930 {
931 spin_lock_bh(&bdi_lock);
932 rb_erase(&bdi->rb_node, &bdi_tree);
933 list_del_rcu(&bdi->bdi_list);
934 spin_unlock_bh(&bdi_lock);
935
936 synchronize_rcu_expedited();
937 }
938
bdi_unregister(struct backing_dev_info * bdi)939 void bdi_unregister(struct backing_dev_info *bdi)
940 {
941 del_timer_sync(&bdi->laptop_mode_wb_timer);
942
943 /* make sure nobody finds us on the bdi_list anymore */
944 bdi_remove_from_list(bdi);
945 wb_shutdown(&bdi->wb);
946 cgwb_bdi_unregister(bdi);
947
948 /*
949 * If this BDI's min ratio has been set, use bdi_set_min_ratio() to
950 * update the global bdi_min_ratio.
951 */
952 if (bdi->min_ratio)
953 bdi_set_min_ratio(bdi, 0);
954
955 if (bdi->dev) {
956 bdi_debug_unregister(bdi);
957 device_unregister(bdi->dev);
958 bdi->dev = NULL;
959 }
960
961 if (bdi->owner) {
962 put_device(bdi->owner);
963 bdi->owner = NULL;
964 }
965 }
966 EXPORT_SYMBOL(bdi_unregister);
967
release_bdi(struct kref * ref)968 static void release_bdi(struct kref *ref)
969 {
970 struct backing_dev_info *bdi =
971 container_of(ref, struct backing_dev_info, refcnt);
972
973 WARN_ON_ONCE(test_bit(WB_registered, &bdi->wb.state));
974 WARN_ON_ONCE(bdi->dev);
975 wb_exit(&bdi->wb);
976 kfree(bdi);
977 }
978
bdi_put(struct backing_dev_info * bdi)979 void bdi_put(struct backing_dev_info *bdi)
980 {
981 kref_put(&bdi->refcnt, release_bdi);
982 }
983 EXPORT_SYMBOL(bdi_put);
984
inode_to_bdi(struct inode * inode)985 struct backing_dev_info *inode_to_bdi(struct inode *inode)
986 {
987 struct super_block *sb;
988
989 if (!inode)
990 return &noop_backing_dev_info;
991
992 sb = inode->i_sb;
993 #ifdef CONFIG_BLOCK
994 if (sb_is_blkdev_sb(sb))
995 return I_BDEV(inode)->bd_disk->bdi;
996 #endif
997 return sb->s_bdi;
998 }
999 EXPORT_SYMBOL(inode_to_bdi);
1000
bdi_dev_name(struct backing_dev_info * bdi)1001 const char *bdi_dev_name(struct backing_dev_info *bdi)
1002 {
1003 if (!bdi || !bdi->dev)
1004 return bdi_unknown_name;
1005 return bdi->dev_name;
1006 }
1007 EXPORT_SYMBOL_GPL(bdi_dev_name);
1008
1009 static wait_queue_head_t congestion_wqh[2] = {
1010 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
1011 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
1012 };
1013 static atomic_t nr_wb_congested[2];
1014
clear_bdi_congested(struct backing_dev_info * bdi,int sync)1015 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
1016 {
1017 wait_queue_head_t *wqh = &congestion_wqh[sync];
1018 enum wb_congested_state bit;
1019
1020 bit = sync ? WB_sync_congested : WB_async_congested;
1021 if (test_and_clear_bit(bit, &bdi->wb.congested))
1022 atomic_dec(&nr_wb_congested[sync]);
1023 smp_mb__after_atomic();
1024 if (waitqueue_active(wqh))
1025 wake_up(wqh);
1026 }
1027 EXPORT_SYMBOL(clear_bdi_congested);
1028
set_bdi_congested(struct backing_dev_info * bdi,int sync)1029 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
1030 {
1031 enum wb_congested_state bit;
1032
1033 bit = sync ? WB_sync_congested : WB_async_congested;
1034 if (!test_and_set_bit(bit, &bdi->wb.congested))
1035 atomic_inc(&nr_wb_congested[sync]);
1036 }
1037 EXPORT_SYMBOL(set_bdi_congested);
1038
1039 /**
1040 * congestion_wait - wait for a backing_dev to become uncongested
1041 * @sync: SYNC or ASYNC IO
1042 * @timeout: timeout in jiffies
1043 *
1044 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
1045 * write congestion. If no backing_devs are congested then just wait for the
1046 * next write to be completed.
1047 */
congestion_wait(int sync,long timeout)1048 long congestion_wait(int sync, long timeout)
1049 {
1050 long ret;
1051 unsigned long start = jiffies;
1052 DEFINE_WAIT(wait);
1053 wait_queue_head_t *wqh = &congestion_wqh[sync];
1054
1055 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1056 ret = io_schedule_timeout(timeout);
1057 finish_wait(wqh, &wait);
1058
1059 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
1060 jiffies_to_usecs(jiffies - start));
1061
1062 return ret;
1063 }
1064 EXPORT_SYMBOL(congestion_wait);
1065