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 struct class *bdi_class;
24 : static const char *bdi_unknown_name = "(unknown)";
25 :
26 : /*
27 : * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
28 : * reader side locking.
29 : */
30 : DEFINE_SPINLOCK(bdi_lock);
31 : static u64 bdi_id_cursor;
32 : static struct rb_root bdi_tree = RB_ROOT;
33 : LIST_HEAD(bdi_list);
34 :
35 : /* bdi_wq serves all asynchronous writeback tasks */
36 : struct workqueue_struct *bdi_wq;
37 :
38 : #define K(x) ((x) << (PAGE_SHIFT - 10))
39 :
40 : #ifdef CONFIG_DEBUG_FS
41 : #include <linux/debugfs.h>
42 : #include <linux/seq_file.h>
43 :
44 : static struct dentry *bdi_debug_root;
45 :
46 : static void bdi_debug_init(void)
47 : {
48 : bdi_debug_root = debugfs_create_dir("bdi", NULL);
49 : }
50 :
51 : static int bdi_debug_stats_show(struct seq_file *m, void *v)
52 : {
53 : struct backing_dev_info *bdi = m->private;
54 : struct bdi_writeback *wb = &bdi->wb;
55 : unsigned long background_thresh;
56 : unsigned long dirty_thresh;
57 : unsigned long wb_thresh;
58 : unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
59 : struct inode *inode;
60 :
61 : nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
62 : spin_lock(&wb->list_lock);
63 : list_for_each_entry(inode, &wb->b_dirty, i_io_list)
64 : nr_dirty++;
65 : list_for_each_entry(inode, &wb->b_io, i_io_list)
66 : nr_io++;
67 : list_for_each_entry(inode, &wb->b_more_io, i_io_list)
68 : nr_more_io++;
69 : list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
70 : if (inode->i_state & I_DIRTY_TIME)
71 : nr_dirty_time++;
72 : spin_unlock(&wb->list_lock);
73 :
74 : global_dirty_limits(&background_thresh, &dirty_thresh);
75 : wb_thresh = wb_calc_thresh(wb, dirty_thresh);
76 :
77 : seq_printf(m,
78 : "BdiWriteback: %10lu kB\n"
79 : "BdiReclaimable: %10lu kB\n"
80 : "BdiDirtyThresh: %10lu kB\n"
81 : "DirtyThresh: %10lu kB\n"
82 : "BackgroundThresh: %10lu kB\n"
83 : "BdiDirtied: %10lu kB\n"
84 : "BdiWritten: %10lu kB\n"
85 : "BdiWriteBandwidth: %10lu kBps\n"
86 : "b_dirty: %10lu\n"
87 : "b_io: %10lu\n"
88 : "b_more_io: %10lu\n"
89 : "b_dirty_time: %10lu\n"
90 : "bdi_list: %10u\n"
91 : "state: %10lx\n",
92 : (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
93 : (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
94 : K(wb_thresh),
95 : K(dirty_thresh),
96 : K(background_thresh),
97 : (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
98 : (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
99 : (unsigned long) K(wb->write_bandwidth),
100 : nr_dirty,
101 : nr_io,
102 : nr_more_io,
103 : nr_dirty_time,
104 : !list_empty(&bdi->bdi_list), bdi->wb.state);
105 :
106 : return 0;
107 : }
108 : DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
109 :
110 : static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
111 : {
112 : bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
113 :
114 : debugfs_create_file("stats", 0444, bdi->debug_dir, bdi,
115 : &bdi_debug_stats_fops);
116 : }
117 :
118 : static void bdi_debug_unregister(struct backing_dev_info *bdi)
119 : {
120 : debugfs_remove_recursive(bdi->debug_dir);
121 : }
122 : #else
123 : static inline void bdi_debug_init(void)
124 : {
125 : }
126 : static inline void bdi_debug_register(struct backing_dev_info *bdi,
127 : const char *name)
128 : {
129 : }
130 : static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
131 : {
132 : }
133 : #endif
134 :
135 0 : static ssize_t read_ahead_kb_store(struct device *dev,
136 : struct device_attribute *attr,
137 : const char *buf, size_t count)
138 : {
139 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
140 : unsigned long read_ahead_kb;
141 : ssize_t ret;
142 :
143 0 : ret = kstrtoul(buf, 10, &read_ahead_kb);
144 0 : if (ret < 0)
145 : return ret;
146 :
147 0 : bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
148 :
149 0 : return count;
150 : }
151 :
152 : #define BDI_SHOW(name, expr) \
153 : static ssize_t name##_show(struct device *dev, \
154 : struct device_attribute *attr, char *buf) \
155 : { \
156 : struct backing_dev_info *bdi = dev_get_drvdata(dev); \
157 : \
158 : return sysfs_emit(buf, "%lld\n", (long long)expr); \
159 : } \
160 : static DEVICE_ATTR_RW(name);
161 :
162 0 : BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
163 :
164 0 : static ssize_t min_ratio_store(struct device *dev,
165 : struct device_attribute *attr, const char *buf, size_t count)
166 : {
167 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
168 : unsigned int ratio;
169 : ssize_t ret;
170 :
171 0 : ret = kstrtouint(buf, 10, &ratio);
172 0 : if (ret < 0)
173 : return ret;
174 :
175 0 : ret = bdi_set_min_ratio(bdi, ratio);
176 0 : if (!ret)
177 0 : ret = count;
178 :
179 : return ret;
180 : }
181 0 : BDI_SHOW(min_ratio, bdi->min_ratio / BDI_RATIO_SCALE)
182 :
183 0 : static ssize_t min_ratio_fine_store(struct device *dev,
184 : struct device_attribute *attr, const char *buf, size_t count)
185 : {
186 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
187 : unsigned int ratio;
188 : ssize_t ret;
189 :
190 0 : ret = kstrtouint(buf, 10, &ratio);
191 0 : if (ret < 0)
192 : return ret;
193 :
194 0 : ret = bdi_set_min_ratio_no_scale(bdi, ratio);
195 0 : if (!ret)
196 0 : ret = count;
197 :
198 : return ret;
199 : }
200 0 : BDI_SHOW(min_ratio_fine, bdi->min_ratio)
201 :
202 0 : static ssize_t max_ratio_store(struct device *dev,
203 : struct device_attribute *attr, const char *buf, size_t count)
204 : {
205 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
206 : unsigned int ratio;
207 : ssize_t ret;
208 :
209 0 : ret = kstrtouint(buf, 10, &ratio);
210 0 : if (ret < 0)
211 : return ret;
212 :
213 0 : ret = bdi_set_max_ratio(bdi, ratio);
214 0 : if (!ret)
215 0 : ret = count;
216 :
217 : return ret;
218 : }
219 0 : BDI_SHOW(max_ratio, bdi->max_ratio / BDI_RATIO_SCALE)
220 :
221 0 : static ssize_t max_ratio_fine_store(struct device *dev,
222 : struct device_attribute *attr, const char *buf, size_t count)
223 : {
224 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
225 : unsigned int ratio;
226 : ssize_t ret;
227 :
228 0 : ret = kstrtouint(buf, 10, &ratio);
229 0 : if (ret < 0)
230 : return ret;
231 :
232 0 : ret = bdi_set_max_ratio_no_scale(bdi, ratio);
233 0 : if (!ret)
234 0 : ret = count;
235 :
236 : return ret;
237 : }
238 0 : BDI_SHOW(max_ratio_fine, bdi->max_ratio)
239 :
240 0 : static ssize_t min_bytes_show(struct device *dev,
241 : struct device_attribute *attr,
242 : char *buf)
243 : {
244 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
245 :
246 0 : return sysfs_emit(buf, "%llu\n", bdi_get_min_bytes(bdi));
247 : }
248 :
249 0 : static ssize_t min_bytes_store(struct device *dev,
250 : struct device_attribute *attr, const char *buf, size_t count)
251 : {
252 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
253 : u64 bytes;
254 : ssize_t ret;
255 :
256 0 : ret = kstrtoull(buf, 10, &bytes);
257 0 : if (ret < 0)
258 : return ret;
259 :
260 0 : ret = bdi_set_min_bytes(bdi, bytes);
261 0 : if (!ret)
262 0 : ret = count;
263 :
264 : return ret;
265 : }
266 : DEVICE_ATTR_RW(min_bytes);
267 :
268 0 : static ssize_t max_bytes_show(struct device *dev,
269 : struct device_attribute *attr,
270 : char *buf)
271 : {
272 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
273 :
274 0 : return sysfs_emit(buf, "%llu\n", bdi_get_max_bytes(bdi));
275 : }
276 :
277 0 : static ssize_t max_bytes_store(struct device *dev,
278 : struct device_attribute *attr, const char *buf, size_t count)
279 : {
280 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
281 : u64 bytes;
282 : ssize_t ret;
283 :
284 0 : ret = kstrtoull(buf, 10, &bytes);
285 0 : if (ret < 0)
286 : return ret;
287 :
288 0 : ret = bdi_set_max_bytes(bdi, bytes);
289 0 : if (!ret)
290 0 : ret = count;
291 :
292 : return ret;
293 : }
294 : DEVICE_ATTR_RW(max_bytes);
295 :
296 0 : static ssize_t stable_pages_required_show(struct device *dev,
297 : struct device_attribute *attr,
298 : char *buf)
299 : {
300 0 : dev_warn_once(dev,
301 : "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n");
302 0 : return sysfs_emit(buf, "%d\n", 0);
303 : }
304 : static DEVICE_ATTR_RO(stable_pages_required);
305 :
306 0 : static ssize_t strict_limit_store(struct device *dev,
307 : struct device_attribute *attr, const char *buf, size_t count)
308 : {
309 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
310 : unsigned int strict_limit;
311 : ssize_t ret;
312 :
313 0 : ret = kstrtouint(buf, 10, &strict_limit);
314 0 : if (ret < 0)
315 : return ret;
316 :
317 0 : ret = bdi_set_strict_limit(bdi, strict_limit);
318 0 : if (!ret)
319 0 : ret = count;
320 :
321 : return ret;
322 : }
323 :
324 0 : static ssize_t strict_limit_show(struct device *dev,
325 : struct device_attribute *attr, char *buf)
326 : {
327 0 : struct backing_dev_info *bdi = dev_get_drvdata(dev);
328 :
329 0 : return sysfs_emit(buf, "%d\n",
330 0 : !!(bdi->capabilities & BDI_CAP_STRICTLIMIT));
331 : }
332 : static DEVICE_ATTR_RW(strict_limit);
333 :
334 : static struct attribute *bdi_dev_attrs[] = {
335 : &dev_attr_read_ahead_kb.attr,
336 : &dev_attr_min_ratio.attr,
337 : &dev_attr_min_ratio_fine.attr,
338 : &dev_attr_max_ratio.attr,
339 : &dev_attr_max_ratio_fine.attr,
340 : &dev_attr_min_bytes.attr,
341 : &dev_attr_max_bytes.attr,
342 : &dev_attr_stable_pages_required.attr,
343 : &dev_attr_strict_limit.attr,
344 : NULL,
345 : };
346 : ATTRIBUTE_GROUPS(bdi_dev);
347 :
348 1 : static __init int bdi_class_init(void)
349 : {
350 1 : bdi_class = class_create(THIS_MODULE, "bdi");
351 2 : if (IS_ERR(bdi_class))
352 0 : return PTR_ERR(bdi_class);
353 :
354 1 : bdi_class->dev_groups = bdi_dev_groups;
355 : bdi_debug_init();
356 :
357 1 : return 0;
358 : }
359 : postcore_initcall(bdi_class_init);
360 :
361 1 : static int __init default_bdi_init(void)
362 : {
363 1 : bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
364 : WQ_SYSFS, 0);
365 1 : if (!bdi_wq)
366 : return -ENOMEM;
367 1 : return 0;
368 : }
369 : subsys_initcall(default_bdi_init);
370 :
371 : /*
372 : * This function is used when the first inode for this wb is marked dirty. It
373 : * wakes-up the corresponding bdi thread which should then take care of the
374 : * periodic background write-out of dirty inodes. Since the write-out would
375 : * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
376 : * set up a timer which wakes the bdi thread up later.
377 : *
378 : * Note, we wouldn't bother setting up the timer, but this function is on the
379 : * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
380 : * by delaying the wake-up.
381 : *
382 : * We have to be careful not to postpone flush work if it is scheduled for
383 : * earlier. Thus we use queue_delayed_work().
384 : */
385 0 : void wb_wakeup_delayed(struct bdi_writeback *wb)
386 : {
387 : unsigned long timeout;
388 :
389 0 : timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
390 0 : spin_lock_irq(&wb->work_lock);
391 0 : if (test_bit(WB_registered, &wb->state))
392 0 : queue_delayed_work(bdi_wq, &wb->dwork, timeout);
393 0 : spin_unlock_irq(&wb->work_lock);
394 0 : }
395 :
396 0 : static void wb_update_bandwidth_workfn(struct work_struct *work)
397 : {
398 0 : struct bdi_writeback *wb = container_of(to_delayed_work(work),
399 : struct bdi_writeback, bw_dwork);
400 :
401 0 : wb_update_bandwidth(wb);
402 0 : }
403 :
404 : /*
405 : * Initial write bandwidth: 100 MB/s
406 : */
407 : #define INIT_BW (100 << (20 - PAGE_SHIFT))
408 :
409 1 : static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
410 : gfp_t gfp)
411 : {
412 : int i, err;
413 :
414 1 : memset(wb, 0, sizeof(*wb));
415 :
416 1 : wb->bdi = bdi;
417 1 : wb->last_old_flush = jiffies;
418 2 : INIT_LIST_HEAD(&wb->b_dirty);
419 2 : INIT_LIST_HEAD(&wb->b_io);
420 2 : INIT_LIST_HEAD(&wb->b_more_io);
421 2 : INIT_LIST_HEAD(&wb->b_dirty_time);
422 1 : spin_lock_init(&wb->list_lock);
423 :
424 2 : atomic_set(&wb->writeback_inodes, 0);
425 1 : wb->bw_time_stamp = jiffies;
426 1 : wb->balanced_dirty_ratelimit = INIT_BW;
427 1 : wb->dirty_ratelimit = INIT_BW;
428 1 : wb->write_bandwidth = INIT_BW;
429 1 : wb->avg_write_bandwidth = INIT_BW;
430 :
431 1 : spin_lock_init(&wb->work_lock);
432 2 : INIT_LIST_HEAD(&wb->work_list);
433 2 : INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
434 2 : INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn);
435 1 : wb->dirty_sleep = jiffies;
436 :
437 1 : err = fprop_local_init_percpu(&wb->completions, gfp);
438 1 : if (err)
439 : return err;
440 :
441 4 : for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
442 8 : err = percpu_counter_init(&wb->stat[i], 0, gfp);
443 : if (err)
444 : goto out_destroy_stat;
445 : }
446 :
447 : return 0;
448 :
449 : out_destroy_stat:
450 : while (i--)
451 : percpu_counter_destroy(&wb->stat[i]);
452 : fprop_local_destroy_percpu(&wb->completions);
453 : return err;
454 : }
455 :
456 : static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
457 :
458 : /*
459 : * Remove bdi from the global list and shutdown any threads we have running
460 : */
461 0 : static void wb_shutdown(struct bdi_writeback *wb)
462 : {
463 : /* Make sure nobody queues further work */
464 0 : spin_lock_irq(&wb->work_lock);
465 0 : if (!test_and_clear_bit(WB_registered, &wb->state)) {
466 0 : spin_unlock_irq(&wb->work_lock);
467 : return;
468 : }
469 0 : spin_unlock_irq(&wb->work_lock);
470 :
471 0 : cgwb_remove_from_bdi_list(wb);
472 : /*
473 : * Drain work list and shutdown the delayed_work. !WB_registered
474 : * tells wb_workfn() that @wb is dying and its work_list needs to
475 : * be drained no matter what.
476 : */
477 0 : mod_delayed_work(bdi_wq, &wb->dwork, 0);
478 0 : flush_delayed_work(&wb->dwork);
479 0 : WARN_ON(!list_empty(&wb->work_list));
480 0 : flush_delayed_work(&wb->bw_dwork);
481 : }
482 :
483 0 : static void wb_exit(struct bdi_writeback *wb)
484 : {
485 : int i;
486 :
487 0 : WARN_ON(delayed_work_pending(&wb->dwork));
488 :
489 : for (i = 0; i < NR_WB_STAT_ITEMS; i++)
490 : percpu_counter_destroy(&wb->stat[i]);
491 :
492 0 : fprop_local_destroy_percpu(&wb->completions);
493 0 : }
494 :
495 : #ifdef CONFIG_CGROUP_WRITEBACK
496 :
497 : #include <linux/memcontrol.h>
498 :
499 : /*
500 : * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
501 : * memcg->cgwb_list. bdi->cgwb_tree is also RCU protected.
502 : */
503 : static DEFINE_SPINLOCK(cgwb_lock);
504 : static struct workqueue_struct *cgwb_release_wq;
505 :
506 : static LIST_HEAD(offline_cgwbs);
507 : static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
508 : static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
509 :
510 : static void cgwb_release_workfn(struct work_struct *work)
511 : {
512 : struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
513 : release_work);
514 : struct backing_dev_info *bdi = wb->bdi;
515 :
516 : mutex_lock(&wb->bdi->cgwb_release_mutex);
517 : wb_shutdown(wb);
518 :
519 : css_put(wb->memcg_css);
520 : css_put(wb->blkcg_css);
521 : mutex_unlock(&wb->bdi->cgwb_release_mutex);
522 :
523 : /* triggers blkg destruction if no online users left */
524 : blkcg_unpin_online(wb->blkcg_css);
525 :
526 : fprop_local_destroy_percpu(&wb->memcg_completions);
527 :
528 : spin_lock_irq(&cgwb_lock);
529 : list_del(&wb->offline_node);
530 : spin_unlock_irq(&cgwb_lock);
531 :
532 : percpu_ref_exit(&wb->refcnt);
533 : wb_exit(wb);
534 : bdi_put(bdi);
535 : WARN_ON_ONCE(!list_empty(&wb->b_attached));
536 : kfree_rcu(wb, rcu);
537 : }
538 :
539 : static void cgwb_release(struct percpu_ref *refcnt)
540 : {
541 : struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
542 : refcnt);
543 : queue_work(cgwb_release_wq, &wb->release_work);
544 : }
545 :
546 : static void cgwb_kill(struct bdi_writeback *wb)
547 : {
548 : lockdep_assert_held(&cgwb_lock);
549 :
550 : WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
551 : list_del(&wb->memcg_node);
552 : list_del(&wb->blkcg_node);
553 : list_add(&wb->offline_node, &offline_cgwbs);
554 : percpu_ref_kill(&wb->refcnt);
555 : }
556 :
557 : static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
558 : {
559 : spin_lock_irq(&cgwb_lock);
560 : list_del_rcu(&wb->bdi_node);
561 : spin_unlock_irq(&cgwb_lock);
562 : }
563 :
564 : static int cgwb_create(struct backing_dev_info *bdi,
565 : struct cgroup_subsys_state *memcg_css, gfp_t gfp)
566 : {
567 : struct mem_cgroup *memcg;
568 : struct cgroup_subsys_state *blkcg_css;
569 : struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
570 : struct bdi_writeback *wb;
571 : unsigned long flags;
572 : int ret = 0;
573 :
574 : memcg = mem_cgroup_from_css(memcg_css);
575 : blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
576 : memcg_cgwb_list = &memcg->cgwb_list;
577 : blkcg_cgwb_list = blkcg_get_cgwb_list(blkcg_css);
578 :
579 : /* look up again under lock and discard on blkcg mismatch */
580 : spin_lock_irqsave(&cgwb_lock, flags);
581 : wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
582 : if (wb && wb->blkcg_css != blkcg_css) {
583 : cgwb_kill(wb);
584 : wb = NULL;
585 : }
586 : spin_unlock_irqrestore(&cgwb_lock, flags);
587 : if (wb)
588 : goto out_put;
589 :
590 : /* need to create a new one */
591 : wb = kmalloc(sizeof(*wb), gfp);
592 : if (!wb) {
593 : ret = -ENOMEM;
594 : goto out_put;
595 : }
596 :
597 : ret = wb_init(wb, bdi, gfp);
598 : if (ret)
599 : goto err_free;
600 :
601 : ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
602 : if (ret)
603 : goto err_wb_exit;
604 :
605 : ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
606 : if (ret)
607 : goto err_ref_exit;
608 :
609 : wb->memcg_css = memcg_css;
610 : wb->blkcg_css = blkcg_css;
611 : INIT_LIST_HEAD(&wb->b_attached);
612 : INIT_WORK(&wb->release_work, cgwb_release_workfn);
613 : set_bit(WB_registered, &wb->state);
614 : bdi_get(bdi);
615 :
616 : /*
617 : * The root wb determines the registered state of the whole bdi and
618 : * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
619 : * whether they're still online. Don't link @wb if any is dead.
620 : * See wb_memcg_offline() and wb_blkcg_offline().
621 : */
622 : ret = -ENODEV;
623 : spin_lock_irqsave(&cgwb_lock, flags);
624 : if (test_bit(WB_registered, &bdi->wb.state) &&
625 : blkcg_cgwb_list->next && memcg_cgwb_list->next) {
626 : /* we might have raced another instance of this function */
627 : ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
628 : if (!ret) {
629 : list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
630 : list_add(&wb->memcg_node, memcg_cgwb_list);
631 : list_add(&wb->blkcg_node, blkcg_cgwb_list);
632 : blkcg_pin_online(blkcg_css);
633 : css_get(memcg_css);
634 : css_get(blkcg_css);
635 : }
636 : }
637 : spin_unlock_irqrestore(&cgwb_lock, flags);
638 : if (ret) {
639 : if (ret == -EEXIST)
640 : ret = 0;
641 : goto err_fprop_exit;
642 : }
643 : goto out_put;
644 :
645 : err_fprop_exit:
646 : bdi_put(bdi);
647 : fprop_local_destroy_percpu(&wb->memcg_completions);
648 : err_ref_exit:
649 : percpu_ref_exit(&wb->refcnt);
650 : err_wb_exit:
651 : wb_exit(wb);
652 : err_free:
653 : kfree(wb);
654 : out_put:
655 : css_put(blkcg_css);
656 : return ret;
657 : }
658 :
659 : /**
660 : * wb_get_lookup - get wb for a given memcg
661 : * @bdi: target bdi
662 : * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
663 : *
664 : * Try to get the wb for @memcg_css on @bdi. The returned wb has its
665 : * refcount incremented.
666 : *
667 : * This function uses css_get() on @memcg_css and thus expects its refcnt
668 : * to be positive on invocation. IOW, rcu_read_lock() protection on
669 : * @memcg_css isn't enough. try_get it before calling this function.
670 : *
671 : * A wb is keyed by its associated memcg. As blkcg implicitly enables
672 : * memcg on the default hierarchy, memcg association is guaranteed to be
673 : * more specific (equal or descendant to the associated blkcg) and thus can
674 : * identify both the memcg and blkcg associations.
675 : *
676 : * Because the blkcg associated with a memcg may change as blkcg is enabled
677 : * and disabled closer to root in the hierarchy, each wb keeps track of
678 : * both the memcg and blkcg associated with it and verifies the blkcg on
679 : * each lookup. On mismatch, the existing wb is discarded and a new one is
680 : * created.
681 : */
682 : struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
683 : struct cgroup_subsys_state *memcg_css)
684 : {
685 : struct bdi_writeback *wb;
686 :
687 : if (!memcg_css->parent)
688 : return &bdi->wb;
689 :
690 : rcu_read_lock();
691 : wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
692 : if (wb) {
693 : struct cgroup_subsys_state *blkcg_css;
694 :
695 : /* see whether the blkcg association has changed */
696 : blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
697 : if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
698 : wb = NULL;
699 : css_put(blkcg_css);
700 : }
701 : rcu_read_unlock();
702 :
703 : return wb;
704 : }
705 :
706 : /**
707 : * wb_get_create - get wb for a given memcg, create if necessary
708 : * @bdi: target bdi
709 : * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
710 : * @gfp: allocation mask to use
711 : *
712 : * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
713 : * create one. See wb_get_lookup() for more details.
714 : */
715 : struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
716 : struct cgroup_subsys_state *memcg_css,
717 : gfp_t gfp)
718 : {
719 : struct bdi_writeback *wb;
720 :
721 : might_alloc(gfp);
722 :
723 : if (!memcg_css->parent)
724 : return &bdi->wb;
725 :
726 : do {
727 : wb = wb_get_lookup(bdi, memcg_css);
728 : } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
729 :
730 : return wb;
731 : }
732 :
733 : static int cgwb_bdi_init(struct backing_dev_info *bdi)
734 : {
735 : int ret;
736 :
737 : INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
738 : mutex_init(&bdi->cgwb_release_mutex);
739 : init_rwsem(&bdi->wb_switch_rwsem);
740 :
741 : ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
742 : if (!ret) {
743 : bdi->wb.memcg_css = &root_mem_cgroup->css;
744 : bdi->wb.blkcg_css = blkcg_root_css;
745 : }
746 : return ret;
747 : }
748 :
749 : static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
750 : {
751 : struct radix_tree_iter iter;
752 : void **slot;
753 : struct bdi_writeback *wb;
754 :
755 : WARN_ON(test_bit(WB_registered, &bdi->wb.state));
756 :
757 : spin_lock_irq(&cgwb_lock);
758 : radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
759 : cgwb_kill(*slot);
760 : spin_unlock_irq(&cgwb_lock);
761 :
762 : mutex_lock(&bdi->cgwb_release_mutex);
763 : spin_lock_irq(&cgwb_lock);
764 : while (!list_empty(&bdi->wb_list)) {
765 : wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
766 : bdi_node);
767 : spin_unlock_irq(&cgwb_lock);
768 : wb_shutdown(wb);
769 : spin_lock_irq(&cgwb_lock);
770 : }
771 : spin_unlock_irq(&cgwb_lock);
772 : mutex_unlock(&bdi->cgwb_release_mutex);
773 : }
774 :
775 : /*
776 : * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
777 : *
778 : * Try to release dying cgwbs by switching attached inodes to the nearest
779 : * living ancestor's writeback. Processed wbs are placed at the end
780 : * of the list to guarantee the forward progress.
781 : */
782 : static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
783 : {
784 : struct bdi_writeback *wb;
785 : LIST_HEAD(processed);
786 :
787 : spin_lock_irq(&cgwb_lock);
788 :
789 : while (!list_empty(&offline_cgwbs)) {
790 : wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
791 : offline_node);
792 : list_move(&wb->offline_node, &processed);
793 :
794 : /*
795 : * If wb is dirty, cleaning up the writeback by switching
796 : * attached inodes will result in an effective removal of any
797 : * bandwidth restrictions, which isn't the goal. Instead,
798 : * it can be postponed until the next time, when all io
799 : * will be likely completed. If in the meantime some inodes
800 : * will get re-dirtied, they should be eventually switched to
801 : * a new cgwb.
802 : */
803 : if (wb_has_dirty_io(wb))
804 : continue;
805 :
806 : if (!wb_tryget(wb))
807 : continue;
808 :
809 : spin_unlock_irq(&cgwb_lock);
810 : while (cleanup_offline_cgwb(wb))
811 : cond_resched();
812 : spin_lock_irq(&cgwb_lock);
813 :
814 : wb_put(wb);
815 : }
816 :
817 : if (!list_empty(&processed))
818 : list_splice_tail(&processed, &offline_cgwbs);
819 :
820 : spin_unlock_irq(&cgwb_lock);
821 : }
822 :
823 : /**
824 : * wb_memcg_offline - kill all wb's associated with a memcg being offlined
825 : * @memcg: memcg being offlined
826 : *
827 : * Also prevents creation of any new wb's associated with @memcg.
828 : */
829 : void wb_memcg_offline(struct mem_cgroup *memcg)
830 : {
831 : struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
832 : struct bdi_writeback *wb, *next;
833 :
834 : spin_lock_irq(&cgwb_lock);
835 : list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
836 : cgwb_kill(wb);
837 : memcg_cgwb_list->next = NULL; /* prevent new wb's */
838 : spin_unlock_irq(&cgwb_lock);
839 :
840 : queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
841 : }
842 :
843 : /**
844 : * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
845 : * @css: blkcg being offlined
846 : *
847 : * Also prevents creation of any new wb's associated with @blkcg.
848 : */
849 : void wb_blkcg_offline(struct cgroup_subsys_state *css)
850 : {
851 : struct bdi_writeback *wb, *next;
852 : struct list_head *list = blkcg_get_cgwb_list(css);
853 :
854 : spin_lock_irq(&cgwb_lock);
855 : list_for_each_entry_safe(wb, next, list, blkcg_node)
856 : cgwb_kill(wb);
857 : list->next = NULL; /* prevent new wb's */
858 : spin_unlock_irq(&cgwb_lock);
859 : }
860 :
861 : static void cgwb_bdi_register(struct backing_dev_info *bdi)
862 : {
863 : spin_lock_irq(&cgwb_lock);
864 : list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
865 : spin_unlock_irq(&cgwb_lock);
866 : }
867 :
868 : static int __init cgwb_init(void)
869 : {
870 : /*
871 : * There can be many concurrent release work items overwhelming
872 : * system_wq. Put them in a separate wq and limit concurrency.
873 : * There's no point in executing many of these in parallel.
874 : */
875 : cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
876 : if (!cgwb_release_wq)
877 : return -ENOMEM;
878 :
879 : return 0;
880 : }
881 : subsys_initcall(cgwb_init);
882 :
883 : #else /* CONFIG_CGROUP_WRITEBACK */
884 :
885 : static int cgwb_bdi_init(struct backing_dev_info *bdi)
886 : {
887 1 : return wb_init(&bdi->wb, bdi, GFP_KERNEL);
888 : }
889 :
890 : static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
891 :
892 : static void cgwb_bdi_register(struct backing_dev_info *bdi)
893 : {
894 0 : list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
895 : }
896 :
897 : static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
898 : {
899 0 : list_del_rcu(&wb->bdi_node);
900 : }
901 :
902 : #endif /* CONFIG_CGROUP_WRITEBACK */
903 :
904 1 : int bdi_init(struct backing_dev_info *bdi)
905 : {
906 1 : bdi->dev = NULL;
907 :
908 2 : kref_init(&bdi->refcnt);
909 1 : bdi->min_ratio = 0;
910 1 : bdi->max_ratio = 100 * BDI_RATIO_SCALE;
911 1 : bdi->max_prop_frac = FPROP_FRAC_BASE;
912 2 : INIT_LIST_HEAD(&bdi->bdi_list);
913 2 : INIT_LIST_HEAD(&bdi->wb_list);
914 1 : init_waitqueue_head(&bdi->wb_waitq);
915 :
916 1 : return cgwb_bdi_init(bdi);
917 : }
918 :
919 0 : struct backing_dev_info *bdi_alloc(int node_id)
920 : {
921 : struct backing_dev_info *bdi;
922 :
923 0 : bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
924 0 : if (!bdi)
925 : return NULL;
926 :
927 0 : if (bdi_init(bdi)) {
928 0 : kfree(bdi);
929 0 : return NULL;
930 : }
931 0 : bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
932 0 : bdi->ra_pages = VM_READAHEAD_PAGES;
933 0 : bdi->io_pages = VM_READAHEAD_PAGES;
934 0 : timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
935 0 : return bdi;
936 : }
937 : EXPORT_SYMBOL(bdi_alloc);
938 :
939 : static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
940 : {
941 : struct rb_node **p = &bdi_tree.rb_node;
942 : struct rb_node *parent = NULL;
943 : struct backing_dev_info *bdi;
944 :
945 : lockdep_assert_held(&bdi_lock);
946 :
947 0 : while (*p) {
948 0 : parent = *p;
949 0 : bdi = rb_entry(parent, struct backing_dev_info, rb_node);
950 :
951 0 : if (bdi->id > id)
952 0 : p = &(*p)->rb_left;
953 0 : else if (bdi->id < id)
954 0 : p = &(*p)->rb_right;
955 : else
956 : break;
957 : }
958 :
959 : if (parentp)
960 0 : *parentp = parent;
961 : return p;
962 : }
963 :
964 : /**
965 : * bdi_get_by_id - lookup and get bdi from its id
966 : * @id: bdi id to lookup
967 : *
968 : * Find bdi matching @id and get it. Returns NULL if the matching bdi
969 : * doesn't exist or is already unregistered.
970 : */
971 0 : struct backing_dev_info *bdi_get_by_id(u64 id)
972 : {
973 0 : struct backing_dev_info *bdi = NULL;
974 : struct rb_node **p;
975 :
976 : spin_lock_bh(&bdi_lock);
977 0 : p = bdi_lookup_rb_node(id, NULL);
978 0 : if (*p) {
979 0 : bdi = rb_entry(*p, struct backing_dev_info, rb_node);
980 : bdi_get(bdi);
981 : }
982 0 : spin_unlock_bh(&bdi_lock);
983 :
984 0 : return bdi;
985 : }
986 :
987 0 : int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
988 : {
989 : struct device *dev;
990 : struct rb_node *parent, **p;
991 :
992 0 : if (bdi->dev) /* The driver needs to use separate queues per device */
993 : return 0;
994 :
995 0 : vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
996 0 : dev = device_create(bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
997 0 : if (IS_ERR(dev))
998 0 : return PTR_ERR(dev);
999 :
1000 0 : cgwb_bdi_register(bdi);
1001 0 : bdi->dev = dev;
1002 :
1003 0 : bdi_debug_register(bdi, dev_name(dev));
1004 0 : set_bit(WB_registered, &bdi->wb.state);
1005 :
1006 0 : spin_lock_bh(&bdi_lock);
1007 :
1008 0 : bdi->id = ++bdi_id_cursor;
1009 :
1010 0 : p = bdi_lookup_rb_node(bdi->id, &parent);
1011 0 : rb_link_node(&bdi->rb_node, parent, p);
1012 0 : rb_insert_color(&bdi->rb_node, &bdi_tree);
1013 :
1014 0 : list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
1015 :
1016 0 : spin_unlock_bh(&bdi_lock);
1017 :
1018 0 : trace_writeback_bdi_register(bdi);
1019 0 : return 0;
1020 : }
1021 :
1022 0 : int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
1023 : {
1024 : va_list args;
1025 : int ret;
1026 :
1027 0 : va_start(args, fmt);
1028 0 : ret = bdi_register_va(bdi, fmt, args);
1029 0 : va_end(args);
1030 0 : return ret;
1031 : }
1032 : EXPORT_SYMBOL(bdi_register);
1033 :
1034 0 : void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
1035 : {
1036 0 : WARN_ON_ONCE(bdi->owner);
1037 0 : bdi->owner = owner;
1038 0 : get_device(owner);
1039 0 : }
1040 :
1041 : /*
1042 : * Remove bdi from bdi_list, and ensure that it is no longer visible
1043 : */
1044 0 : static void bdi_remove_from_list(struct backing_dev_info *bdi)
1045 : {
1046 0 : spin_lock_bh(&bdi_lock);
1047 0 : rb_erase(&bdi->rb_node, &bdi_tree);
1048 0 : list_del_rcu(&bdi->bdi_list);
1049 0 : spin_unlock_bh(&bdi_lock);
1050 :
1051 : synchronize_rcu_expedited();
1052 0 : }
1053 :
1054 0 : void bdi_unregister(struct backing_dev_info *bdi)
1055 : {
1056 0 : del_timer_sync(&bdi->laptop_mode_wb_timer);
1057 :
1058 : /* make sure nobody finds us on the bdi_list anymore */
1059 0 : bdi_remove_from_list(bdi);
1060 0 : wb_shutdown(&bdi->wb);
1061 0 : cgwb_bdi_unregister(bdi);
1062 :
1063 : /*
1064 : * If this BDI's min ratio has been set, use bdi_set_min_ratio() to
1065 : * update the global bdi_min_ratio.
1066 : */
1067 0 : if (bdi->min_ratio)
1068 0 : bdi_set_min_ratio(bdi, 0);
1069 :
1070 0 : if (bdi->dev) {
1071 0 : bdi_debug_unregister(bdi);
1072 0 : device_unregister(bdi->dev);
1073 0 : bdi->dev = NULL;
1074 : }
1075 :
1076 0 : if (bdi->owner) {
1077 0 : put_device(bdi->owner);
1078 0 : bdi->owner = NULL;
1079 : }
1080 0 : }
1081 : EXPORT_SYMBOL(bdi_unregister);
1082 :
1083 0 : static void release_bdi(struct kref *ref)
1084 : {
1085 0 : struct backing_dev_info *bdi =
1086 0 : container_of(ref, struct backing_dev_info, refcnt);
1087 :
1088 0 : WARN_ON_ONCE(test_bit(WB_registered, &bdi->wb.state));
1089 0 : WARN_ON_ONCE(bdi->dev);
1090 0 : wb_exit(&bdi->wb);
1091 0 : kfree(bdi);
1092 0 : }
1093 :
1094 0 : void bdi_put(struct backing_dev_info *bdi)
1095 : {
1096 0 : kref_put(&bdi->refcnt, release_bdi);
1097 0 : }
1098 : EXPORT_SYMBOL(bdi_put);
1099 :
1100 0 : struct backing_dev_info *inode_to_bdi(struct inode *inode)
1101 : {
1102 : struct super_block *sb;
1103 :
1104 0 : if (!inode)
1105 : return &noop_backing_dev_info;
1106 :
1107 0 : sb = inode->i_sb;
1108 : #ifdef CONFIG_BLOCK
1109 0 : if (sb_is_blkdev_sb(sb))
1110 0 : return I_BDEV(inode)->bd_disk->bdi;
1111 : #endif
1112 0 : return sb->s_bdi;
1113 : }
1114 : EXPORT_SYMBOL(inode_to_bdi);
1115 :
1116 0 : const char *bdi_dev_name(struct backing_dev_info *bdi)
1117 : {
1118 0 : if (!bdi || !bdi->dev)
1119 0 : return bdi_unknown_name;
1120 0 : return bdi->dev_name;
1121 : }
1122 : EXPORT_SYMBOL_GPL(bdi_dev_name);
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