Line data Source code
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 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 :
45 : static void bdi_debug_init(void)
46 : {
47 : bdi_debug_root = debugfs_create_dir("bdi", NULL);
48 : }
49 :
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 :
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 :
117 : static void bdi_debug_unregister(struct backing_dev_info *bdi)
118 : {
119 : debugfs_remove_recursive(bdi->debug_dir);
120 : }
121 : #else
122 : static inline void bdi_debug_init(void)
123 : {
124 : }
125 : static inline void bdi_debug_register(struct backing_dev_info *bdi,
126 : const char *name)
127 : {
128 : }
129 : static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
130 : {
131 : }
132 : #endif
133 :
134 0 : static ssize_t read_ahead_kb_store(struct device *dev,
135 : struct device_attribute *attr,
136 : const char *buf, size_t count)
137 : {
138 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
139 : unsigned long read_ahead_kb;
140 : ssize_t ret;
141 :
142 0 : ret = kstrtoul(buf, 10, &read_ahead_kb);
143 0 : if (ret < 0)
144 : return ret;
145 :
146 0 : bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
147 :
148 0 : 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 0 : BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
162 :
163 0 : static ssize_t min_ratio_store(struct device *dev,
164 : struct device_attribute *attr, const char *buf, size_t count)
165 : {
166 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
167 : unsigned int ratio;
168 : ssize_t ret;
169 :
170 0 : ret = kstrtouint(buf, 10, &ratio);
171 0 : if (ret < 0)
172 : return ret;
173 :
174 0 : ret = bdi_set_min_ratio(bdi, ratio);
175 0 : if (!ret)
176 0 : ret = count;
177 :
178 : return ret;
179 : }
180 0 : BDI_SHOW(min_ratio, bdi->min_ratio / BDI_RATIO_SCALE)
181 :
182 0 : static ssize_t min_ratio_fine_store(struct device *dev,
183 : struct device_attribute *attr, const char *buf, size_t count)
184 : {
185 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
186 : unsigned int ratio;
187 : ssize_t ret;
188 :
189 0 : ret = kstrtouint(buf, 10, &ratio);
190 0 : if (ret < 0)
191 : return ret;
192 :
193 0 : ret = bdi_set_min_ratio_no_scale(bdi, ratio);
194 0 : if (!ret)
195 0 : ret = count;
196 :
197 : return ret;
198 : }
199 0 : BDI_SHOW(min_ratio_fine, bdi->min_ratio)
200 :
201 0 : static ssize_t max_ratio_store(struct device *dev,
202 : struct device_attribute *attr, const char *buf, size_t count)
203 : {
204 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
205 : unsigned int ratio;
206 : ssize_t ret;
207 :
208 0 : ret = kstrtouint(buf, 10, &ratio);
209 0 : if (ret < 0)
210 : return ret;
211 :
212 0 : ret = bdi_set_max_ratio(bdi, ratio);
213 0 : if (!ret)
214 0 : ret = count;
215 :
216 : return ret;
217 : }
218 0 : BDI_SHOW(max_ratio, bdi->max_ratio / BDI_RATIO_SCALE)
219 :
220 0 : static ssize_t max_ratio_fine_store(struct device *dev,
221 : struct device_attribute *attr, const char *buf, size_t count)
222 : {
223 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
224 : unsigned int ratio;
225 : ssize_t ret;
226 :
227 0 : ret = kstrtouint(buf, 10, &ratio);
228 0 : if (ret < 0)
229 : return ret;
230 :
231 0 : ret = bdi_set_max_ratio_no_scale(bdi, ratio);
232 0 : if (!ret)
233 0 : ret = count;
234 :
235 : return ret;
236 : }
237 0 : BDI_SHOW(max_ratio_fine, bdi->max_ratio)
238 :
239 0 : static ssize_t min_bytes_show(struct device *dev,
240 : struct device_attribute *attr,
241 : char *buf)
242 : {
243 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
244 :
245 0 : return sysfs_emit(buf, "%llu\n", bdi_get_min_bytes(bdi));
246 : }
247 :
248 0 : static ssize_t min_bytes_store(struct device *dev,
249 : struct device_attribute *attr, const char *buf, size_t count)
250 : {
251 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
252 : u64 bytes;
253 : ssize_t ret;
254 :
255 0 : ret = kstrtoull(buf, 10, &bytes);
256 0 : if (ret < 0)
257 : return ret;
258 :
259 0 : ret = bdi_set_min_bytes(bdi, bytes);
260 0 : if (!ret)
261 0 : ret = count;
262 :
263 : return ret;
264 : }
265 : static DEVICE_ATTR_RW(min_bytes);
266 :
267 0 : static ssize_t max_bytes_show(struct device *dev,
268 : struct device_attribute *attr,
269 : char *buf)
270 : {
271 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
272 :
273 0 : return sysfs_emit(buf, "%llu\n", bdi_get_max_bytes(bdi));
274 : }
275 :
276 0 : static ssize_t max_bytes_store(struct device *dev,
277 : struct device_attribute *attr, const char *buf, size_t count)
278 : {
279 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
280 : u64 bytes;
281 : ssize_t ret;
282 :
283 0 : ret = kstrtoull(buf, 10, &bytes);
284 0 : if (ret < 0)
285 : return ret;
286 :
287 0 : ret = bdi_set_max_bytes(bdi, bytes);
288 0 : if (!ret)
289 0 : ret = count;
290 :
291 : return ret;
292 : }
293 : static DEVICE_ATTR_RW(max_bytes);
294 :
295 0 : static ssize_t stable_pages_required_show(struct device *dev,
296 : struct device_attribute *attr,
297 : char *buf)
298 : {
299 0 : dev_warn_once(dev,
300 : "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n");
301 0 : return sysfs_emit(buf, "%d\n", 0);
302 : }
303 : static DEVICE_ATTR_RO(stable_pages_required);
304 :
305 0 : static ssize_t strict_limit_store(struct device *dev,
306 : struct device_attribute *attr, const char *buf, size_t count)
307 : {
308 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
309 : unsigned int strict_limit;
310 : ssize_t ret;
311 :
312 0 : ret = kstrtouint(buf, 10, &strict_limit);
313 0 : if (ret < 0)
314 : return ret;
315 :
316 0 : ret = bdi_set_strict_limit(bdi, strict_limit);
317 0 : if (!ret)
318 0 : ret = count;
319 :
320 : return ret;
321 : }
322 :
323 0 : static ssize_t strict_limit_show(struct device *dev,
324 : struct device_attribute *attr, char *buf)
325 : {
326 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
327 :
328 0 : return sysfs_emit(buf, "%d\n",
329 0 : !!(bdi->capabilities & BDI_CAP_STRICTLIMIT));
330 : }
331 : static DEVICE_ATTR_RW(strict_limit);
332 :
333 : static struct attribute *bdi_dev_attrs[] = {
334 : &dev_attr_read_ahead_kb.attr,
335 : &dev_attr_min_ratio.attr,
336 : &dev_attr_min_ratio_fine.attr,
337 : &dev_attr_max_ratio.attr,
338 : &dev_attr_max_ratio_fine.attr,
339 : &dev_attr_min_bytes.attr,
340 : &dev_attr_max_bytes.attr,
341 : &dev_attr_stable_pages_required.attr,
342 : &dev_attr_strict_limit.attr,
343 : NULL,
344 : };
345 : ATTRIBUTE_GROUPS(bdi_dev);
346 :
347 : static const struct class bdi_class = {
348 : .name = "bdi",
349 : .dev_groups = bdi_dev_groups,
350 : };
351 :
352 1 : static __init int bdi_class_init(void)
353 : {
354 : int ret;
355 :
356 1 : ret = class_register(&bdi_class);
357 1 : if (ret)
358 : return ret;
359 :
360 : bdi_debug_init();
361 :
362 1 : return 0;
363 : }
364 : postcore_initcall(bdi_class_init);
365 :
366 1 : static int __init default_bdi_init(void)
367 : {
368 1 : bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
369 : WQ_SYSFS, 0);
370 1 : if (!bdi_wq)
371 : return -ENOMEM;
372 1 : return 0;
373 : }
374 : subsys_initcall(default_bdi_init);
375 :
376 : /*
377 : * This function is used when the first inode for this wb is marked dirty. It
378 : * wakes-up the corresponding bdi thread which should then take care of the
379 : * periodic background write-out of dirty inodes. Since the write-out would
380 : * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
381 : * set up a timer which wakes the bdi thread up later.
382 : *
383 : * Note, we wouldn't bother setting up the timer, but this function is on the
384 : * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
385 : * by delaying the wake-up.
386 : *
387 : * We have to be careful not to postpone flush work if it is scheduled for
388 : * earlier. Thus we use queue_delayed_work().
389 : */
390 0 : void wb_wakeup_delayed(struct bdi_writeback *wb)
391 : {
392 : unsigned long timeout;
393 :
394 0 : timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
395 0 : spin_lock_irq(&wb->work_lock);
396 0 : if (test_bit(WB_registered, &wb->state))
397 0 : queue_delayed_work(bdi_wq, &wb->dwork, timeout);
398 0 : spin_unlock_irq(&wb->work_lock);
399 0 : }
400 :
401 0 : static void wb_update_bandwidth_workfn(struct work_struct *work)
402 : {
403 0 : struct bdi_writeback *wb = container_of(to_delayed_work(work),
404 : struct bdi_writeback, bw_dwork);
405 :
406 0 : wb_update_bandwidth(wb);
407 0 : }
408 :
409 : /*
410 : * Initial write bandwidth: 100 MB/s
411 : */
412 : #define INIT_BW (100 << (20 - PAGE_SHIFT))
413 :
414 1 : static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
415 : gfp_t gfp)
416 : {
417 : int i, err;
418 :
419 2 : memset(wb, 0, sizeof(*wb));
420 :
421 1 : wb->bdi = bdi;
422 1 : wb->last_old_flush = jiffies;
423 2 : INIT_LIST_HEAD(&wb->b_dirty);
424 2 : INIT_LIST_HEAD(&wb->b_io);
425 2 : INIT_LIST_HEAD(&wb->b_more_io);
426 2 : INIT_LIST_HEAD(&wb->b_dirty_time);
427 1 : spin_lock_init(&wb->list_lock);
428 :
429 2 : atomic_set(&wb->writeback_inodes, 0);
430 1 : wb->bw_time_stamp = jiffies;
431 1 : wb->balanced_dirty_ratelimit = INIT_BW;
432 1 : wb->dirty_ratelimit = INIT_BW;
433 1 : wb->write_bandwidth = INIT_BW;
434 1 : wb->avg_write_bandwidth = INIT_BW;
435 :
436 1 : spin_lock_init(&wb->work_lock);
437 2 : INIT_LIST_HEAD(&wb->work_list);
438 2 : INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
439 2 : INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn);
440 1 : wb->dirty_sleep = jiffies;
441 :
442 1 : err = fprop_local_init_percpu(&wb->completions, gfp);
443 1 : if (err)
444 : return err;
445 :
446 4 : for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
447 8 : err = percpu_counter_init(&wb->stat[i], 0, gfp);
448 : if (err)
449 : goto out_destroy_stat;
450 : }
451 :
452 : return 0;
453 :
454 : out_destroy_stat:
455 : while (i--)
456 : percpu_counter_destroy(&wb->stat[i]);
457 : fprop_local_destroy_percpu(&wb->completions);
458 : return err;
459 : }
460 :
461 : static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
462 :
463 : /*
464 : * Remove bdi from the global list and shutdown any threads we have running
465 : */
466 0 : static void wb_shutdown(struct bdi_writeback *wb)
467 : {
468 : /* Make sure nobody queues further work */
469 0 : spin_lock_irq(&wb->work_lock);
470 0 : if (!test_and_clear_bit(WB_registered, &wb->state)) {
471 0 : spin_unlock_irq(&wb->work_lock);
472 : return;
473 : }
474 0 : spin_unlock_irq(&wb->work_lock);
475 :
476 0 : cgwb_remove_from_bdi_list(wb);
477 : /*
478 : * Drain work list and shutdown the delayed_work. !WB_registered
479 : * tells wb_workfn() that @wb is dying and its work_list needs to
480 : * be drained no matter what.
481 : */
482 0 : mod_delayed_work(bdi_wq, &wb->dwork, 0);
483 0 : flush_delayed_work(&wb->dwork);
484 0 : WARN_ON(!list_empty(&wb->work_list));
485 0 : flush_delayed_work(&wb->bw_dwork);
486 : }
487 :
488 0 : static void wb_exit(struct bdi_writeback *wb)
489 : {
490 : int i;
491 :
492 0 : WARN_ON(delayed_work_pending(&wb->dwork));
493 :
494 : for (i = 0; i < NR_WB_STAT_ITEMS; i++)
495 : percpu_counter_destroy(&wb->stat[i]);
496 :
497 0 : fprop_local_destroy_percpu(&wb->completions);
498 0 : }
499 :
500 : #ifdef CONFIG_CGROUP_WRITEBACK
501 :
502 : #include <linux/memcontrol.h>
503 :
504 : /*
505 : * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
506 : * memcg->cgwb_list. bdi->cgwb_tree is also RCU protected.
507 : */
508 : static DEFINE_SPINLOCK(cgwb_lock);
509 : static struct workqueue_struct *cgwb_release_wq;
510 :
511 : static LIST_HEAD(offline_cgwbs);
512 : static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
513 : static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
514 :
515 : static void cgwb_free_rcu(struct rcu_head *rcu_head)
516 : {
517 : struct bdi_writeback *wb = container_of(rcu_head,
518 : struct bdi_writeback, rcu);
519 :
520 : percpu_ref_exit(&wb->refcnt);
521 : kfree(wb);
522 : }
523 :
524 : static void cgwb_release_workfn(struct work_struct *work)
525 : {
526 : struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
527 : release_work);
528 : struct backing_dev_info *bdi = wb->bdi;
529 :
530 : mutex_lock(&wb->bdi->cgwb_release_mutex);
531 : wb_shutdown(wb);
532 :
533 : css_put(wb->memcg_css);
534 : css_put(wb->blkcg_css);
535 : mutex_unlock(&wb->bdi->cgwb_release_mutex);
536 :
537 : /* triggers blkg destruction if no online users left */
538 : blkcg_unpin_online(wb->blkcg_css);
539 :
540 : fprop_local_destroy_percpu(&wb->memcg_completions);
541 :
542 : spin_lock_irq(&cgwb_lock);
543 : list_del(&wb->offline_node);
544 : spin_unlock_irq(&cgwb_lock);
545 :
546 : wb_exit(wb);
547 : bdi_put(bdi);
548 : WARN_ON_ONCE(!list_empty(&wb->b_attached));
549 : call_rcu(&wb->rcu, cgwb_free_rcu);
550 : }
551 :
552 : static void cgwb_release(struct percpu_ref *refcnt)
553 : {
554 : struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
555 : refcnt);
556 : queue_work(cgwb_release_wq, &wb->release_work);
557 : }
558 :
559 : static void cgwb_kill(struct bdi_writeback *wb)
560 : {
561 : lockdep_assert_held(&cgwb_lock);
562 :
563 : WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
564 : list_del(&wb->memcg_node);
565 : list_del(&wb->blkcg_node);
566 : list_add(&wb->offline_node, &offline_cgwbs);
567 : percpu_ref_kill(&wb->refcnt);
568 : }
569 :
570 : static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
571 : {
572 : spin_lock_irq(&cgwb_lock);
573 : list_del_rcu(&wb->bdi_node);
574 : spin_unlock_irq(&cgwb_lock);
575 : }
576 :
577 : static int cgwb_create(struct backing_dev_info *bdi,
578 : struct cgroup_subsys_state *memcg_css, gfp_t gfp)
579 : {
580 : struct mem_cgroup *memcg;
581 : struct cgroup_subsys_state *blkcg_css;
582 : struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
583 : struct bdi_writeback *wb;
584 : unsigned long flags;
585 : int ret = 0;
586 :
587 : memcg = mem_cgroup_from_css(memcg_css);
588 : blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
589 : memcg_cgwb_list = &memcg->cgwb_list;
590 : blkcg_cgwb_list = blkcg_get_cgwb_list(blkcg_css);
591 :
592 : /* look up again under lock and discard on blkcg mismatch */
593 : spin_lock_irqsave(&cgwb_lock, flags);
594 : wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
595 : if (wb && wb->blkcg_css != blkcg_css) {
596 : cgwb_kill(wb);
597 : wb = NULL;
598 : }
599 : spin_unlock_irqrestore(&cgwb_lock, flags);
600 : if (wb)
601 : goto out_put;
602 :
603 : /* need to create a new one */
604 : wb = kmalloc(sizeof(*wb), gfp);
605 : if (!wb) {
606 : ret = -ENOMEM;
607 : goto out_put;
608 : }
609 :
610 : ret = wb_init(wb, bdi, gfp);
611 : if (ret)
612 : goto err_free;
613 :
614 : ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
615 : if (ret)
616 : goto err_wb_exit;
617 :
618 : ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
619 : if (ret)
620 : goto err_ref_exit;
621 :
622 : wb->memcg_css = memcg_css;
623 : wb->blkcg_css = blkcg_css;
624 : INIT_LIST_HEAD(&wb->b_attached);
625 : INIT_WORK(&wb->release_work, cgwb_release_workfn);
626 : set_bit(WB_registered, &wb->state);
627 : bdi_get(bdi);
628 :
629 : /*
630 : * The root wb determines the registered state of the whole bdi and
631 : * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
632 : * whether they're still online. Don't link @wb if any is dead.
633 : * See wb_memcg_offline() and wb_blkcg_offline().
634 : */
635 : ret = -ENODEV;
636 : spin_lock_irqsave(&cgwb_lock, flags);
637 : if (test_bit(WB_registered, &bdi->wb.state) &&
638 : blkcg_cgwb_list->next && memcg_cgwb_list->next) {
639 : /* we might have raced another instance of this function */
640 : ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
641 : if (!ret) {
642 : list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
643 : list_add(&wb->memcg_node, memcg_cgwb_list);
644 : list_add(&wb->blkcg_node, blkcg_cgwb_list);
645 : blkcg_pin_online(blkcg_css);
646 : css_get(memcg_css);
647 : css_get(blkcg_css);
648 : }
649 : }
650 : spin_unlock_irqrestore(&cgwb_lock, flags);
651 : if (ret) {
652 : if (ret == -EEXIST)
653 : ret = 0;
654 : goto err_fprop_exit;
655 : }
656 : goto out_put;
657 :
658 : err_fprop_exit:
659 : bdi_put(bdi);
660 : fprop_local_destroy_percpu(&wb->memcg_completions);
661 : err_ref_exit:
662 : percpu_ref_exit(&wb->refcnt);
663 : err_wb_exit:
664 : wb_exit(wb);
665 : err_free:
666 : kfree(wb);
667 : out_put:
668 : css_put(blkcg_css);
669 : return ret;
670 : }
671 :
672 : /**
673 : * wb_get_lookup - get wb for a given memcg
674 : * @bdi: target bdi
675 : * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
676 : *
677 : * Try to get the wb for @memcg_css on @bdi. The returned wb has its
678 : * refcount incremented.
679 : *
680 : * This function uses css_get() on @memcg_css and thus expects its refcnt
681 : * to be positive on invocation. IOW, rcu_read_lock() protection on
682 : * @memcg_css isn't enough. try_get it before calling this function.
683 : *
684 : * A wb is keyed by its associated memcg. As blkcg implicitly enables
685 : * memcg on the default hierarchy, memcg association is guaranteed to be
686 : * more specific (equal or descendant to the associated blkcg) and thus can
687 : * identify both the memcg and blkcg associations.
688 : *
689 : * Because the blkcg associated with a memcg may change as blkcg is enabled
690 : * and disabled closer to root in the hierarchy, each wb keeps track of
691 : * both the memcg and blkcg associated with it and verifies the blkcg on
692 : * each lookup. On mismatch, the existing wb is discarded and a new one is
693 : * created.
694 : */
695 : struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
696 : struct cgroup_subsys_state *memcg_css)
697 : {
698 : struct bdi_writeback *wb;
699 :
700 : if (!memcg_css->parent)
701 : return &bdi->wb;
702 :
703 : rcu_read_lock();
704 : wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
705 : if (wb) {
706 : struct cgroup_subsys_state *blkcg_css;
707 :
708 : /* see whether the blkcg association has changed */
709 : blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
710 : if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
711 : wb = NULL;
712 : css_put(blkcg_css);
713 : }
714 : rcu_read_unlock();
715 :
716 : return wb;
717 : }
718 :
719 : /**
720 : * wb_get_create - get wb for a given memcg, create if necessary
721 : * @bdi: target bdi
722 : * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
723 : * @gfp: allocation mask to use
724 : *
725 : * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
726 : * create one. See wb_get_lookup() for more details.
727 : */
728 : struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
729 : struct cgroup_subsys_state *memcg_css,
730 : gfp_t gfp)
731 : {
732 : struct bdi_writeback *wb;
733 :
734 : might_alloc(gfp);
735 :
736 : if (!memcg_css->parent)
737 : return &bdi->wb;
738 :
739 : do {
740 : wb = wb_get_lookup(bdi, memcg_css);
741 : } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
742 :
743 : return wb;
744 : }
745 :
746 : static int cgwb_bdi_init(struct backing_dev_info *bdi)
747 : {
748 : int ret;
749 :
750 : INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
751 : mutex_init(&bdi->cgwb_release_mutex);
752 : init_rwsem(&bdi->wb_switch_rwsem);
753 :
754 : ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
755 : if (!ret) {
756 : bdi->wb.memcg_css = &root_mem_cgroup->css;
757 : bdi->wb.blkcg_css = blkcg_root_css;
758 : }
759 : return ret;
760 : }
761 :
762 : static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
763 : {
764 : struct radix_tree_iter iter;
765 : void **slot;
766 : struct bdi_writeback *wb;
767 :
768 : WARN_ON(test_bit(WB_registered, &bdi->wb.state));
769 :
770 : spin_lock_irq(&cgwb_lock);
771 : radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
772 : cgwb_kill(*slot);
773 : spin_unlock_irq(&cgwb_lock);
774 :
775 : mutex_lock(&bdi->cgwb_release_mutex);
776 : spin_lock_irq(&cgwb_lock);
777 : while (!list_empty(&bdi->wb_list)) {
778 : wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
779 : bdi_node);
780 : spin_unlock_irq(&cgwb_lock);
781 : wb_shutdown(wb);
782 : spin_lock_irq(&cgwb_lock);
783 : }
784 : spin_unlock_irq(&cgwb_lock);
785 : mutex_unlock(&bdi->cgwb_release_mutex);
786 : }
787 :
788 : /*
789 : * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
790 : *
791 : * Try to release dying cgwbs by switching attached inodes to the nearest
792 : * living ancestor's writeback. Processed wbs are placed at the end
793 : * of the list to guarantee the forward progress.
794 : */
795 : static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
796 : {
797 : struct bdi_writeback *wb;
798 : LIST_HEAD(processed);
799 :
800 : spin_lock_irq(&cgwb_lock);
801 :
802 : while (!list_empty(&offline_cgwbs)) {
803 : wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
804 : offline_node);
805 : list_move(&wb->offline_node, &processed);
806 :
807 : /*
808 : * If wb is dirty, cleaning up the writeback by switching
809 : * attached inodes will result in an effective removal of any
810 : * bandwidth restrictions, which isn't the goal. Instead,
811 : * it can be postponed until the next time, when all io
812 : * will be likely completed. If in the meantime some inodes
813 : * will get re-dirtied, they should be eventually switched to
814 : * a new cgwb.
815 : */
816 : if (wb_has_dirty_io(wb))
817 : continue;
818 :
819 : if (!wb_tryget(wb))
820 : continue;
821 :
822 : spin_unlock_irq(&cgwb_lock);
823 : while (cleanup_offline_cgwb(wb))
824 : cond_resched();
825 : spin_lock_irq(&cgwb_lock);
826 :
827 : wb_put(wb);
828 : }
829 :
830 : if (!list_empty(&processed))
831 : list_splice_tail(&processed, &offline_cgwbs);
832 :
833 : spin_unlock_irq(&cgwb_lock);
834 : }
835 :
836 : /**
837 : * wb_memcg_offline - kill all wb's associated with a memcg being offlined
838 : * @memcg: memcg being offlined
839 : *
840 : * Also prevents creation of any new wb's associated with @memcg.
841 : */
842 : void wb_memcg_offline(struct mem_cgroup *memcg)
843 : {
844 : struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
845 : struct bdi_writeback *wb, *next;
846 :
847 : spin_lock_irq(&cgwb_lock);
848 : list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
849 : cgwb_kill(wb);
850 : memcg_cgwb_list->next = NULL; /* prevent new wb's */
851 : spin_unlock_irq(&cgwb_lock);
852 :
853 : queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
854 : }
855 :
856 : /**
857 : * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
858 : * @css: blkcg being offlined
859 : *
860 : * Also prevents creation of any new wb's associated with @blkcg.
861 : */
862 : void wb_blkcg_offline(struct cgroup_subsys_state *css)
863 : {
864 : struct bdi_writeback *wb, *next;
865 : struct list_head *list = blkcg_get_cgwb_list(css);
866 :
867 : spin_lock_irq(&cgwb_lock);
868 : list_for_each_entry_safe(wb, next, list, blkcg_node)
869 : cgwb_kill(wb);
870 : list->next = NULL; /* prevent new wb's */
871 : spin_unlock_irq(&cgwb_lock);
872 : }
873 :
874 : static void cgwb_bdi_register(struct backing_dev_info *bdi)
875 : {
876 : spin_lock_irq(&cgwb_lock);
877 : list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
878 : spin_unlock_irq(&cgwb_lock);
879 : }
880 :
881 : static int __init cgwb_init(void)
882 : {
883 : /*
884 : * There can be many concurrent release work items overwhelming
885 : * system_wq. Put them in a separate wq and limit concurrency.
886 : * There's no point in executing many of these in parallel.
887 : */
888 : cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
889 : if (!cgwb_release_wq)
890 : return -ENOMEM;
891 :
892 : return 0;
893 : }
894 : subsys_initcall(cgwb_init);
895 :
896 : #else /* CONFIG_CGROUP_WRITEBACK */
897 :
898 : static int cgwb_bdi_init(struct backing_dev_info *bdi)
899 : {
900 1 : return wb_init(&bdi->wb, bdi, GFP_KERNEL);
901 : }
902 :
903 : static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
904 :
905 : static void cgwb_bdi_register(struct backing_dev_info *bdi)
906 : {
907 0 : list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
908 : }
909 :
910 : static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
911 : {
912 0 : list_del_rcu(&wb->bdi_node);
913 : }
914 :
915 : #endif /* CONFIG_CGROUP_WRITEBACK */
916 :
917 1 : int bdi_init(struct backing_dev_info *bdi)
918 : {
919 1 : bdi->dev = NULL;
920 :
921 2 : kref_init(&bdi->refcnt);
922 1 : bdi->min_ratio = 0;
923 1 : bdi->max_ratio = 100 * BDI_RATIO_SCALE;
924 1 : bdi->max_prop_frac = FPROP_FRAC_BASE;
925 2 : INIT_LIST_HEAD(&bdi->bdi_list);
926 2 : INIT_LIST_HEAD(&bdi->wb_list);
927 1 : init_waitqueue_head(&bdi->wb_waitq);
928 :
929 1 : return cgwb_bdi_init(bdi);
930 : }
931 :
932 0 : struct backing_dev_info *bdi_alloc(int node_id)
933 : {
934 : struct backing_dev_info *bdi;
935 :
936 0 : bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
937 0 : if (!bdi)
938 : return NULL;
939 :
940 0 : if (bdi_init(bdi)) {
941 0 : kfree(bdi);
942 0 : return NULL;
943 : }
944 0 : bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
945 0 : bdi->ra_pages = VM_READAHEAD_PAGES;
946 0 : bdi->io_pages = VM_READAHEAD_PAGES;
947 0 : timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
948 0 : return bdi;
949 : }
950 : EXPORT_SYMBOL(bdi_alloc);
951 :
952 : static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
953 : {
954 : struct rb_node **p = &bdi_tree.rb_node;
955 : struct rb_node *parent = NULL;
956 : struct backing_dev_info *bdi;
957 :
958 : lockdep_assert_held(&bdi_lock);
959 :
960 0 : while (*p) {
961 0 : parent = *p;
962 0 : bdi = rb_entry(parent, struct backing_dev_info, rb_node);
963 :
964 0 : if (bdi->id > id)
965 0 : p = &(*p)->rb_left;
966 0 : else if (bdi->id < id)
967 0 : p = &(*p)->rb_right;
968 : else
969 : break;
970 : }
971 :
972 : if (parentp)
973 0 : *parentp = parent;
974 : return p;
975 : }
976 :
977 : /**
978 : * bdi_get_by_id - lookup and get bdi from its id
979 : * @id: bdi id to lookup
980 : *
981 : * Find bdi matching @id and get it. Returns NULL if the matching bdi
982 : * doesn't exist or is already unregistered.
983 : */
984 0 : struct backing_dev_info *bdi_get_by_id(u64 id)
985 : {
986 0 : struct backing_dev_info *bdi = NULL;
987 : struct rb_node **p;
988 :
989 : spin_lock_bh(&bdi_lock);
990 0 : p = bdi_lookup_rb_node(id, NULL);
991 0 : if (*p) {
992 0 : bdi = rb_entry(*p, struct backing_dev_info, rb_node);
993 : bdi_get(bdi);
994 : }
995 0 : spin_unlock_bh(&bdi_lock);
996 :
997 0 : return bdi;
998 : }
999 :
1000 0 : int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
1001 : {
1002 : struct device *dev;
1003 : struct rb_node *parent, **p;
1004 :
1005 0 : if (bdi->dev) /* The driver needs to use separate queues per device */
1006 : return 0;
1007 :
1008 0 : vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
1009 0 : dev = device_create(&bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
1010 0 : if (IS_ERR(dev))
1011 0 : return PTR_ERR(dev);
1012 :
1013 0 : cgwb_bdi_register(bdi);
1014 0 : bdi->dev = dev;
1015 :
1016 0 : bdi_debug_register(bdi, dev_name(dev));
1017 0 : set_bit(WB_registered, &bdi->wb.state);
1018 :
1019 0 : spin_lock_bh(&bdi_lock);
1020 :
1021 0 : bdi->id = ++bdi_id_cursor;
1022 :
1023 0 : p = bdi_lookup_rb_node(bdi->id, &parent);
1024 0 : rb_link_node(&bdi->rb_node, parent, p);
1025 0 : rb_insert_color(&bdi->rb_node, &bdi_tree);
1026 :
1027 0 : list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
1028 :
1029 0 : spin_unlock_bh(&bdi_lock);
1030 :
1031 0 : trace_writeback_bdi_register(bdi);
1032 0 : return 0;
1033 : }
1034 :
1035 0 : int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
1036 : {
1037 : va_list args;
1038 : int ret;
1039 :
1040 0 : va_start(args, fmt);
1041 0 : ret = bdi_register_va(bdi, fmt, args);
1042 0 : va_end(args);
1043 0 : return ret;
1044 : }
1045 : EXPORT_SYMBOL(bdi_register);
1046 :
1047 0 : void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
1048 : {
1049 0 : WARN_ON_ONCE(bdi->owner);
1050 0 : bdi->owner = owner;
1051 0 : get_device(owner);
1052 0 : }
1053 :
1054 : /*
1055 : * Remove bdi from bdi_list, and ensure that it is no longer visible
1056 : */
1057 0 : static void bdi_remove_from_list(struct backing_dev_info *bdi)
1058 : {
1059 0 : spin_lock_bh(&bdi_lock);
1060 0 : rb_erase(&bdi->rb_node, &bdi_tree);
1061 0 : list_del_rcu(&bdi->bdi_list);
1062 0 : spin_unlock_bh(&bdi_lock);
1063 :
1064 : synchronize_rcu_expedited();
1065 0 : }
1066 :
1067 0 : void bdi_unregister(struct backing_dev_info *bdi)
1068 : {
1069 0 : del_timer_sync(&bdi->laptop_mode_wb_timer);
1070 :
1071 : /* make sure nobody finds us on the bdi_list anymore */
1072 0 : bdi_remove_from_list(bdi);
1073 0 : wb_shutdown(&bdi->wb);
1074 0 : cgwb_bdi_unregister(bdi);
1075 :
1076 : /*
1077 : * If this BDI's min ratio has been set, use bdi_set_min_ratio() to
1078 : * update the global bdi_min_ratio.
1079 : */
1080 0 : if (bdi->min_ratio)
1081 0 : bdi_set_min_ratio(bdi, 0);
1082 :
1083 0 : if (bdi->dev) {
1084 0 : bdi_debug_unregister(bdi);
1085 0 : device_unregister(bdi->dev);
1086 0 : bdi->dev = NULL;
1087 : }
1088 :
1089 0 : if (bdi->owner) {
1090 0 : put_device(bdi->owner);
1091 0 : bdi->owner = NULL;
1092 : }
1093 0 : }
1094 : EXPORT_SYMBOL(bdi_unregister);
1095 :
1096 0 : static void release_bdi(struct kref *ref)
1097 : {
1098 0 : struct backing_dev_info *bdi =
1099 0 : container_of(ref, struct backing_dev_info, refcnt);
1100 :
1101 0 : WARN_ON_ONCE(test_bit(WB_registered, &bdi->wb.state));
1102 0 : WARN_ON_ONCE(bdi->dev);
1103 0 : wb_exit(&bdi->wb);
1104 0 : kfree(bdi);
1105 0 : }
1106 :
1107 0 : void bdi_put(struct backing_dev_info *bdi)
1108 : {
1109 0 : kref_put(&bdi->refcnt, release_bdi);
1110 0 : }
1111 : EXPORT_SYMBOL(bdi_put);
1112 :
1113 0 : struct backing_dev_info *inode_to_bdi(struct inode *inode)
1114 : {
1115 : struct super_block *sb;
1116 :
1117 0 : if (!inode)
1118 : return &noop_backing_dev_info;
1119 :
1120 0 : sb = inode->i_sb;
1121 : #ifdef CONFIG_BLOCK
1122 0 : if (sb_is_blkdev_sb(sb))
1123 0 : return I_BDEV(inode)->bd_disk->bdi;
1124 : #endif
1125 0 : return sb->s_bdi;
1126 : }
1127 : EXPORT_SYMBOL(inode_to_bdi);
1128 :
1129 0 : const char *bdi_dev_name(struct backing_dev_info *bdi)
1130 : {
1131 0 : if (!bdi || !bdi->dev)
1132 0 : return bdi_unknown_name;
1133 0 : return bdi->dev_name;
1134 : }
1135 : EXPORT_SYMBOL_GPL(bdi_dev_name);
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