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1 | // SPDX-License-Identifier: GPL-2.0-only | |
2 | ||
3 | #include <linux/wait.h> | |
4 | #include <linux/rbtree.h> | |
5 | #include <linux/backing-dev.h> | |
6 | #include <linux/kthread.h> | |
7 | #include <linux/freezer.h> | |
8 | #include <linux/fs.h> | |
9 | #include <linux/pagemap.h> | |
10 | #include <linux/mm.h> | |
11 | #include <linux/sched/mm.h> | |
12 | #include <linux/sched.h> | |
13 | #include <linux/module.h> | |
14 | #include <linux/writeback.h> | |
15 | #include <linux/device.h> | |
16 | #include <trace/events/writeback.h> | |
17 | ||
18 | struct backing_dev_info noop_backing_dev_info; | |
19 | EXPORT_SYMBOL_GPL(noop_backing_dev_info); | |
20 | ||
21 | static struct class *bdi_class; | |
22 | static const char *bdi_unknown_name = "(unknown)"; | |
23 | ||
24 | /* | |
25 | * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU | |
26 | * reader side locking. | |
27 | */ | |
28 | DEFINE_SPINLOCK(bdi_lock); | |
29 | static u64 bdi_id_cursor; | |
30 | static struct rb_root bdi_tree = RB_ROOT; | |
31 | LIST_HEAD(bdi_list); | |
32 | ||
33 | /* bdi_wq serves all asynchronous writeback tasks */ | |
34 | struct workqueue_struct *bdi_wq; | |
35 | ||
36 | #define K(x) ((x) << (PAGE_SHIFT - 10)) | |
37 | ||
38 | #ifdef CONFIG_DEBUG_FS | |
39 | #include <linux/debugfs.h> | |
40 | #include <linux/seq_file.h> | |
41 | ||
42 | static struct dentry *bdi_debug_root; | |
43 | ||
44 | static void bdi_debug_init(void) | |
45 | { | |
46 | bdi_debug_root = debugfs_create_dir("bdi", NULL); | |
47 | } | |
48 | ||
49 | static int bdi_debug_stats_show(struct seq_file *m, void *v) | |
50 | { | |
51 | struct backing_dev_info *bdi = m->private; | |
52 | struct bdi_writeback *wb = &bdi->wb; | |
53 | unsigned long background_thresh; | |
54 | unsigned long dirty_thresh; | |
55 | unsigned long wb_thresh; | |
56 | unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time; | |
57 | struct inode *inode; | |
58 | ||
59 | nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0; | |
60 | spin_lock(&wb->list_lock); | |
61 | list_for_each_entry(inode, &wb->b_dirty, i_io_list) | |
62 | nr_dirty++; | |
63 | list_for_each_entry(inode, &wb->b_io, i_io_list) | |
64 | nr_io++; | |
65 | list_for_each_entry(inode, &wb->b_more_io, i_io_list) | |
66 | nr_more_io++; | |
67 | list_for_each_entry(inode, &wb->b_dirty_time, i_io_list) | |
68 | if (inode->i_state & I_DIRTY_TIME) | |
69 | nr_dirty_time++; | |
70 | spin_unlock(&wb->list_lock); | |
71 | ||
72 | global_dirty_limits(&background_thresh, &dirty_thresh); | |
73 | wb_thresh = wb_calc_thresh(wb, dirty_thresh); | |
74 | ||
75 | seq_printf(m, | |
76 | "BdiWriteback: %10lu kB\n" | |
77 | "BdiReclaimable: %10lu kB\n" | |
78 | "BdiDirtyThresh: %10lu kB\n" | |
79 | "DirtyThresh: %10lu kB\n" | |
80 | "BackgroundThresh: %10lu kB\n" | |
81 | "BdiDirtied: %10lu kB\n" | |
82 | "BdiWritten: %10lu kB\n" | |
83 | "BdiWriteBandwidth: %10lu kBps\n" | |
84 | "b_dirty: %10lu\n" | |
85 | "b_io: %10lu\n" | |
86 | "b_more_io: %10lu\n" | |
87 | "b_dirty_time: %10lu\n" | |
88 | "bdi_list: %10u\n" | |
89 | "state: %10lx\n", | |
90 | (unsigned long) K(wb_stat(wb, WB_WRITEBACK)), | |
91 | (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)), | |
92 | K(wb_thresh), | |
93 | K(dirty_thresh), | |
94 | K(background_thresh), | |
95 | (unsigned long) K(wb_stat(wb, WB_DIRTIED)), | |
96 | (unsigned long) K(wb_stat(wb, WB_WRITTEN)), | |
97 | (unsigned long) K(wb->write_bandwidth), | |
98 | nr_dirty, | |
99 | nr_io, | |
100 | nr_more_io, | |
101 | nr_dirty_time, | |
102 | !list_empty(&bdi->bdi_list), bdi->wb.state); | |
103 | ||
104 | return 0; | |
105 | } | |
106 | DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats); | |
107 | ||
108 | static void bdi_debug_register(struct backing_dev_info *bdi, const char *name) | |
109 | { | |
110 | bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root); | |
111 | ||
112 | debugfs_create_file("stats", 0444, bdi->debug_dir, bdi, | |
113 | &bdi_debug_stats_fops); | |
114 | } | |
115 | ||
116 | static void bdi_debug_unregister(struct backing_dev_info *bdi) | |
117 | { | |
118 | debugfs_remove_recursive(bdi->debug_dir); | |
119 | } | |
120 | #else | |
121 | static inline void bdi_debug_init(void) | |
122 | { | |
123 | } | |
124 | static inline void bdi_debug_register(struct backing_dev_info *bdi, | |
125 | const char *name) | |
126 | { | |
127 | } | |
128 | static inline void bdi_debug_unregister(struct backing_dev_info *bdi) | |
129 | { | |
130 | } | |
131 | #endif | |
132 | ||
133 | static ssize_t read_ahead_kb_store(struct device *dev, | |
134 | struct device_attribute *attr, | |
135 | const char *buf, size_t count) | |
136 | { | |
137 | struct backing_dev_info *bdi = dev_get_drvdata(dev); | |
138 | unsigned long read_ahead_kb; | |
139 | ssize_t ret; | |
140 | ||
141 | ret = kstrtoul(buf, 10, &read_ahead_kb); | |
142 | if (ret < 0) | |
143 | return ret; | |
144 | ||
145 | bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10); | |
146 | ||
147 | return count; | |
148 | } | |
149 | ||
150 | #define BDI_SHOW(name, expr) \ | |
151 | static ssize_t name##_show(struct device *dev, \ | |
152 | struct device_attribute *attr, char *buf) \ | |
153 | { \ | |
154 | struct backing_dev_info *bdi = dev_get_drvdata(dev); \ | |
155 | \ | |
156 | return sysfs_emit(buf, "%lld\n", (long long)expr); \ | |
157 | } \ | |
158 | static DEVICE_ATTR_RW(name); | |
159 | ||
160 | BDI_SHOW(read_ahead_kb, K(bdi->ra_pages)) | |
161 | ||
162 | static ssize_t min_ratio_store(struct device *dev, | |
163 | struct device_attribute *attr, const char *buf, size_t count) | |
164 | { | |
165 | struct backing_dev_info *bdi = dev_get_drvdata(dev); | |
166 | unsigned int ratio; | |
167 | ssize_t ret; | |
168 | ||
169 | ret = kstrtouint(buf, 10, &ratio); | |
170 | if (ret < 0) | |
171 | return ret; | |
172 | ||
173 | ret = bdi_set_min_ratio(bdi, ratio); | |
174 | if (!ret) | |
175 | ret = count; | |
176 | ||
177 | return ret; | |
178 | } | |
179 | BDI_SHOW(min_ratio, bdi->min_ratio) | |
180 | ||
181 | static ssize_t max_ratio_store(struct device *dev, | |
182 | struct device_attribute *attr, const char *buf, size_t count) | |
183 | { | |
184 | struct backing_dev_info *bdi = dev_get_drvdata(dev); | |
185 | unsigned int ratio; | |
186 | ssize_t ret; | |
187 | ||
188 | ret = kstrtouint(buf, 10, &ratio); | |
189 | if (ret < 0) | |
190 | return ret; | |
191 | ||
192 | ret = bdi_set_max_ratio(bdi, ratio); | |
193 | if (!ret) | |
194 | ret = count; | |
195 | ||
196 | return ret; | |
197 | } | |
198 | BDI_SHOW(max_ratio, bdi->max_ratio) | |
199 | ||
200 | static ssize_t stable_pages_required_show(struct device *dev, | |
201 | struct device_attribute *attr, | |
202 | char *buf) | |
203 | { | |
204 | dev_warn_once(dev, | |
205 | "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n"); | |
206 | return sysfs_emit(buf, "%d\n", 0); | |
207 | } | |
208 | static DEVICE_ATTR_RO(stable_pages_required); | |
209 | ||
210 | static struct attribute *bdi_dev_attrs[] = { | |
211 | &dev_attr_read_ahead_kb.attr, | |
212 | &dev_attr_min_ratio.attr, | |
213 | &dev_attr_max_ratio.attr, | |
214 | &dev_attr_stable_pages_required.attr, | |
215 | NULL, | |
216 | }; | |
217 | ATTRIBUTE_GROUPS(bdi_dev); | |
218 | ||
219 | static __init int bdi_class_init(void) | |
220 | { | |
221 | bdi_class = class_create(THIS_MODULE, "bdi"); | |
222 | if (IS_ERR(bdi_class)) | |
223 | return PTR_ERR(bdi_class); | |
224 | ||
225 | bdi_class->dev_groups = bdi_dev_groups; | |
226 | bdi_debug_init(); | |
227 | ||
228 | return 0; | |
229 | } | |
230 | postcore_initcall(bdi_class_init); | |
231 | ||
232 | static int bdi_init(struct backing_dev_info *bdi); | |
233 | ||
234 | static int __init default_bdi_init(void) | |
235 | { | |
236 | int err; | |
237 | ||
238 | bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND | | |
239 | WQ_SYSFS, 0); | |
240 | if (!bdi_wq) | |
241 | return -ENOMEM; | |
242 | ||
243 | err = bdi_init(&noop_backing_dev_info); | |
244 | ||
245 | return err; | |
246 | } | |
247 | subsys_initcall(default_bdi_init); | |
248 | ||
249 | /* | |
250 | * This function is used when the first inode for this wb is marked dirty. It | |
251 | * wakes-up the corresponding bdi thread which should then take care of the | |
252 | * periodic background write-out of dirty inodes. Since the write-out would | |
253 | * starts only 'dirty_writeback_interval' centisecs from now anyway, we just | |
254 | * set up a timer which wakes the bdi thread up later. | |
255 | * | |
256 | * Note, we wouldn't bother setting up the timer, but this function is on the | |
257 | * fast-path (used by '__mark_inode_dirty()'), so we save few context switches | |
258 | * by delaying the wake-up. | |
259 | * | |
260 | * We have to be careful not to postpone flush work if it is scheduled for | |
261 | * earlier. Thus we use queue_delayed_work(). | |
262 | */ | |
263 | void wb_wakeup_delayed(struct bdi_writeback *wb) | |
264 | { | |
265 | unsigned long timeout; | |
266 | ||
267 | timeout = msecs_to_jiffies(dirty_writeback_interval * 10); | |
268 | spin_lock_bh(&wb->work_lock); | |
269 | if (test_bit(WB_registered, &wb->state)) | |
270 | queue_delayed_work(bdi_wq, &wb->dwork, timeout); | |
271 | spin_unlock_bh(&wb->work_lock); | |
272 | } | |
273 | ||
274 | /* | |
275 | * Initial write bandwidth: 100 MB/s | |
276 | */ | |
277 | #define INIT_BW (100 << (20 - PAGE_SHIFT)) | |
278 | ||
279 | static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi, | |
280 | gfp_t gfp) | |
281 | { | |
282 | int i, err; | |
283 | ||
284 | memset(wb, 0, sizeof(*wb)); | |
285 | ||
286 | if (wb != &bdi->wb) | |
287 | bdi_get(bdi); | |
288 | wb->bdi = bdi; | |
289 | wb->last_old_flush = jiffies; | |
290 | INIT_LIST_HEAD(&wb->b_dirty); | |
291 | INIT_LIST_HEAD(&wb->b_io); | |
292 | INIT_LIST_HEAD(&wb->b_more_io); | |
293 | INIT_LIST_HEAD(&wb->b_dirty_time); | |
294 | spin_lock_init(&wb->list_lock); | |
295 | ||
296 | wb->bw_time_stamp = jiffies; | |
297 | wb->balanced_dirty_ratelimit = INIT_BW; | |
298 | wb->dirty_ratelimit = INIT_BW; | |
299 | wb->write_bandwidth = INIT_BW; | |
300 | wb->avg_write_bandwidth = INIT_BW; | |
301 | ||
302 | spin_lock_init(&wb->work_lock); | |
303 | INIT_LIST_HEAD(&wb->work_list); | |
304 | INIT_DELAYED_WORK(&wb->dwork, wb_workfn); | |
305 | wb->dirty_sleep = jiffies; | |
306 | ||
307 | err = fprop_local_init_percpu(&wb->completions, gfp); | |
308 | if (err) | |
309 | goto out_put_bdi; | |
310 | ||
311 | for (i = 0; i < NR_WB_STAT_ITEMS; i++) { | |
312 | err = percpu_counter_init(&wb->stat[i], 0, gfp); | |
313 | if (err) | |
314 | goto out_destroy_stat; | |
315 | } | |
316 | ||
317 | return 0; | |
318 | ||
319 | out_destroy_stat: | |
320 | while (i--) | |
321 | percpu_counter_destroy(&wb->stat[i]); | |
322 | fprop_local_destroy_percpu(&wb->completions); | |
323 | out_put_bdi: | |
324 | if (wb != &bdi->wb) | |
325 | bdi_put(bdi); | |
326 | return err; | |
327 | } | |
328 | ||
329 | static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb); | |
330 | ||
331 | /* | |
332 | * Remove bdi from the global list and shutdown any threads we have running | |
333 | */ | |
334 | static void wb_shutdown(struct bdi_writeback *wb) | |
335 | { | |
336 | /* Make sure nobody queues further work */ | |
337 | spin_lock_bh(&wb->work_lock); | |
338 | if (!test_and_clear_bit(WB_registered, &wb->state)) { | |
339 | spin_unlock_bh(&wb->work_lock); | |
340 | return; | |
341 | } | |
342 | spin_unlock_bh(&wb->work_lock); | |
343 | ||
344 | cgwb_remove_from_bdi_list(wb); | |
345 | /* | |
346 | * Drain work list and shutdown the delayed_work. !WB_registered | |
347 | * tells wb_workfn() that @wb is dying and its work_list needs to | |
348 | * be drained no matter what. | |
349 | */ | |
350 | mod_delayed_work(bdi_wq, &wb->dwork, 0); | |
351 | flush_delayed_work(&wb->dwork); | |
352 | WARN_ON(!list_empty(&wb->work_list)); | |
353 | } | |
354 | ||
355 | static void wb_exit(struct bdi_writeback *wb) | |
356 | { | |
357 | int i; | |
358 | ||
359 | WARN_ON(delayed_work_pending(&wb->dwork)); | |
360 | ||
361 | for (i = 0; i < NR_WB_STAT_ITEMS; i++) | |
362 | percpu_counter_destroy(&wb->stat[i]); | |
363 | ||
364 | fprop_local_destroy_percpu(&wb->completions); | |
365 | if (wb != &wb->bdi->wb) | |
366 | bdi_put(wb->bdi); | |
367 | } | |
368 | ||
369 | #ifdef CONFIG_CGROUP_WRITEBACK | |
370 | ||
371 | #include <linux/memcontrol.h> | |
372 | ||
373 | /* | |
374 | * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, and memcg->cgwb_list. | |
375 | * bdi->cgwb_tree is also RCU protected. | |
376 | */ | |
377 | static DEFINE_SPINLOCK(cgwb_lock); | |
378 | static struct workqueue_struct *cgwb_release_wq; | |
379 | ||
380 | static void cgwb_release_workfn(struct work_struct *work) | |
381 | { | |
382 | struct bdi_writeback *wb = container_of(work, struct bdi_writeback, | |
383 | release_work); | |
384 | struct blkcg *blkcg = css_to_blkcg(wb->blkcg_css); | |
385 | ||
386 | mutex_lock(&wb->bdi->cgwb_release_mutex); | |
387 | wb_shutdown(wb); | |
388 | ||
389 | css_put(wb->memcg_css); | |
390 | css_put(wb->blkcg_css); | |
391 | mutex_unlock(&wb->bdi->cgwb_release_mutex); | |
392 | ||
393 | /* triggers blkg destruction if no online users left */ | |
394 | blkcg_unpin_online(blkcg); | |
395 | ||
396 | fprop_local_destroy_percpu(&wb->memcg_completions); | |
397 | percpu_ref_exit(&wb->refcnt); | |
398 | wb_exit(wb); | |
399 | kfree_rcu(wb, rcu); | |
400 | } | |
401 | ||
402 | static void cgwb_release(struct percpu_ref *refcnt) | |
403 | { | |
404 | struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback, | |
405 | refcnt); | |
406 | queue_work(cgwb_release_wq, &wb->release_work); | |
407 | } | |
408 | ||
409 | static void cgwb_kill(struct bdi_writeback *wb) | |
410 | { | |
411 | lockdep_assert_held(&cgwb_lock); | |
412 | ||
413 | WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id)); | |
414 | list_del(&wb->memcg_node); | |
415 | list_del(&wb->blkcg_node); | |
416 | percpu_ref_kill(&wb->refcnt); | |
417 | } | |
418 | ||
419 | static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb) | |
420 | { | |
421 | spin_lock_irq(&cgwb_lock); | |
422 | list_del_rcu(&wb->bdi_node); | |
423 | spin_unlock_irq(&cgwb_lock); | |
424 | } | |
425 | ||
426 | static int cgwb_create(struct backing_dev_info *bdi, | |
427 | struct cgroup_subsys_state *memcg_css, gfp_t gfp) | |
428 | { | |
429 | struct mem_cgroup *memcg; | |
430 | struct cgroup_subsys_state *blkcg_css; | |
431 | struct blkcg *blkcg; | |
432 | struct list_head *memcg_cgwb_list, *blkcg_cgwb_list; | |
433 | struct bdi_writeback *wb; | |
434 | unsigned long flags; | |
435 | int ret = 0; | |
436 | ||
437 | memcg = mem_cgroup_from_css(memcg_css); | |
438 | blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys); | |
439 | blkcg = css_to_blkcg(blkcg_css); | |
440 | memcg_cgwb_list = &memcg->cgwb_list; | |
441 | blkcg_cgwb_list = &blkcg->cgwb_list; | |
442 | ||
443 | /* look up again under lock and discard on blkcg mismatch */ | |
444 | spin_lock_irqsave(&cgwb_lock, flags); | |
445 | wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id); | |
446 | if (wb && wb->blkcg_css != blkcg_css) { | |
447 | cgwb_kill(wb); | |
448 | wb = NULL; | |
449 | } | |
450 | spin_unlock_irqrestore(&cgwb_lock, flags); | |
451 | if (wb) | |
452 | goto out_put; | |
453 | ||
454 | /* need to create a new one */ | |
455 | wb = kmalloc(sizeof(*wb), gfp); | |
456 | if (!wb) { | |
457 | ret = -ENOMEM; | |
458 | goto out_put; | |
459 | } | |
460 | ||
461 | ret = wb_init(wb, bdi, gfp); | |
462 | if (ret) | |
463 | goto err_free; | |
464 | ||
465 | ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp); | |
466 | if (ret) | |
467 | goto err_wb_exit; | |
468 | ||
469 | ret = fprop_local_init_percpu(&wb->memcg_completions, gfp); | |
470 | if (ret) | |
471 | goto err_ref_exit; | |
472 | ||
473 | wb->memcg_css = memcg_css; | |
474 | wb->blkcg_css = blkcg_css; | |
475 | INIT_WORK(&wb->release_work, cgwb_release_workfn); | |
476 | set_bit(WB_registered, &wb->state); | |
477 | ||
478 | /* | |
479 | * The root wb determines the registered state of the whole bdi and | |
480 | * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate | |
481 | * whether they're still online. Don't link @wb if any is dead. | |
482 | * See wb_memcg_offline() and wb_blkcg_offline(). | |
483 | */ | |
484 | ret = -ENODEV; | |
485 | spin_lock_irqsave(&cgwb_lock, flags); | |
486 | if (test_bit(WB_registered, &bdi->wb.state) && | |
487 | blkcg_cgwb_list->next && memcg_cgwb_list->next) { | |
488 | /* we might have raced another instance of this function */ | |
489 | ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb); | |
490 | if (!ret) { | |
491 | list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list); | |
492 | list_add(&wb->memcg_node, memcg_cgwb_list); | |
493 | list_add(&wb->blkcg_node, blkcg_cgwb_list); | |
494 | blkcg_pin_online(blkcg); | |
495 | css_get(memcg_css); | |
496 | css_get(blkcg_css); | |
497 | } | |
498 | } | |
499 | spin_unlock_irqrestore(&cgwb_lock, flags); | |
500 | if (ret) { | |
501 | if (ret == -EEXIST) | |
502 | ret = 0; | |
503 | goto err_fprop_exit; | |
504 | } | |
505 | goto out_put; | |
506 | ||
507 | err_fprop_exit: | |
508 | fprop_local_destroy_percpu(&wb->memcg_completions); | |
509 | err_ref_exit: | |
510 | percpu_ref_exit(&wb->refcnt); | |
511 | err_wb_exit: | |
512 | wb_exit(wb); | |
513 | err_free: | |
514 | kfree(wb); | |
515 | out_put: | |
516 | css_put(blkcg_css); | |
517 | return ret; | |
518 | } | |
519 | ||
520 | /** | |
521 | * wb_get_lookup - get wb for a given memcg | |
522 | * @bdi: target bdi | |
523 | * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref) | |
524 | * | |
525 | * Try to get the wb for @memcg_css on @bdi. The returned wb has its | |
526 | * refcount incremented. | |
527 | * | |
528 | * This function uses css_get() on @memcg_css and thus expects its refcnt | |
529 | * to be positive on invocation. IOW, rcu_read_lock() protection on | |
530 | * @memcg_css isn't enough. try_get it before calling this function. | |
531 | * | |
532 | * A wb is keyed by its associated memcg. As blkcg implicitly enables | |
533 | * memcg on the default hierarchy, memcg association is guaranteed to be | |
534 | * more specific (equal or descendant to the associated blkcg) and thus can | |
535 | * identify both the memcg and blkcg associations. | |
536 | * | |
537 | * Because the blkcg associated with a memcg may change as blkcg is enabled | |
538 | * and disabled closer to root in the hierarchy, each wb keeps track of | |
539 | * both the memcg and blkcg associated with it and verifies the blkcg on | |
540 | * each lookup. On mismatch, the existing wb is discarded and a new one is | |
541 | * created. | |
542 | */ | |
543 | struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi, | |
544 | struct cgroup_subsys_state *memcg_css) | |
545 | { | |
546 | struct bdi_writeback *wb; | |
547 | ||
548 | if (!memcg_css->parent) | |
549 | return &bdi->wb; | |
550 | ||
551 | rcu_read_lock(); | |
552 | wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id); | |
553 | if (wb) { | |
554 | struct cgroup_subsys_state *blkcg_css; | |
555 | ||
556 | /* see whether the blkcg association has changed */ | |
557 | blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys); | |
558 | if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb))) | |
559 | wb = NULL; | |
560 | css_put(blkcg_css); | |
561 | } | |
562 | rcu_read_unlock(); | |
563 | ||
564 | return wb; | |
565 | } | |
566 | ||
567 | /** | |
568 | * wb_get_create - get wb for a given memcg, create if necessary | |
569 | * @bdi: target bdi | |
570 | * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref) | |
571 | * @gfp: allocation mask to use | |
572 | * | |
573 | * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to | |
574 | * create one. See wb_get_lookup() for more details. | |
575 | */ | |
576 | struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi, | |
577 | struct cgroup_subsys_state *memcg_css, | |
578 | gfp_t gfp) | |
579 | { | |
580 | struct bdi_writeback *wb; | |
581 | ||
582 | might_alloc(gfp); | |
583 | ||
584 | if (!memcg_css->parent) | |
585 | return &bdi->wb; | |
586 | ||
587 | do { | |
588 | wb = wb_get_lookup(bdi, memcg_css); | |
589 | } while (!wb && !cgwb_create(bdi, memcg_css, gfp)); | |
590 | ||
591 | return wb; | |
592 | } | |
593 | ||
594 | static int cgwb_bdi_init(struct backing_dev_info *bdi) | |
595 | { | |
596 | int ret; | |
597 | ||
598 | INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC); | |
599 | mutex_init(&bdi->cgwb_release_mutex); | |
600 | init_rwsem(&bdi->wb_switch_rwsem); | |
601 | ||
602 | ret = wb_init(&bdi->wb, bdi, GFP_KERNEL); | |
603 | if (!ret) { | |
604 | bdi->wb.memcg_css = &root_mem_cgroup->css; | |
605 | bdi->wb.blkcg_css = blkcg_root_css; | |
606 | } | |
607 | return ret; | |
608 | } | |
609 | ||
610 | static void cgwb_bdi_unregister(struct backing_dev_info *bdi) | |
611 | { | |
612 | struct radix_tree_iter iter; | |
613 | void **slot; | |
614 | struct bdi_writeback *wb; | |
615 | ||
616 | WARN_ON(test_bit(WB_registered, &bdi->wb.state)); | |
617 | ||
618 | spin_lock_irq(&cgwb_lock); | |
619 | radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0) | |
620 | cgwb_kill(*slot); | |
621 | spin_unlock_irq(&cgwb_lock); | |
622 | ||
623 | mutex_lock(&bdi->cgwb_release_mutex); | |
624 | spin_lock_irq(&cgwb_lock); | |
625 | while (!list_empty(&bdi->wb_list)) { | |
626 | wb = list_first_entry(&bdi->wb_list, struct bdi_writeback, | |
627 | bdi_node); | |
628 | spin_unlock_irq(&cgwb_lock); | |
629 | wb_shutdown(wb); | |
630 | spin_lock_irq(&cgwb_lock); | |
631 | } | |
632 | spin_unlock_irq(&cgwb_lock); | |
633 | mutex_unlock(&bdi->cgwb_release_mutex); | |
634 | } | |
635 | ||
636 | /** | |
637 | * wb_memcg_offline - kill all wb's associated with a memcg being offlined | |
638 | * @memcg: memcg being offlined | |
639 | * | |
640 | * Also prevents creation of any new wb's associated with @memcg. | |
641 | */ | |
642 | void wb_memcg_offline(struct mem_cgroup *memcg) | |
643 | { | |
644 | struct list_head *memcg_cgwb_list = &memcg->cgwb_list; | |
645 | struct bdi_writeback *wb, *next; | |
646 | ||
647 | spin_lock_irq(&cgwb_lock); | |
648 | list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node) | |
649 | cgwb_kill(wb); | |
650 | memcg_cgwb_list->next = NULL; /* prevent new wb's */ | |
651 | spin_unlock_irq(&cgwb_lock); | |
652 | } | |
653 | ||
654 | /** | |
655 | * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined | |
656 | * @blkcg: blkcg being offlined | |
657 | * | |
658 | * Also prevents creation of any new wb's associated with @blkcg. | |
659 | */ | |
660 | void wb_blkcg_offline(struct blkcg *blkcg) | |
661 | { | |
662 | struct bdi_writeback *wb, *next; | |
663 | ||
664 | spin_lock_irq(&cgwb_lock); | |
665 | list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node) | |
666 | cgwb_kill(wb); | |
667 | blkcg->cgwb_list.next = NULL; /* prevent new wb's */ | |
668 | spin_unlock_irq(&cgwb_lock); | |
669 | } | |
670 | ||
671 | static void cgwb_bdi_register(struct backing_dev_info *bdi) | |
672 | { | |
673 | spin_lock_irq(&cgwb_lock); | |
674 | list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list); | |
675 | spin_unlock_irq(&cgwb_lock); | |
676 | } | |
677 | ||
678 | static int __init cgwb_init(void) | |
679 | { | |
680 | /* | |
681 | * There can be many concurrent release work items overwhelming | |
682 | * system_wq. Put them in a separate wq and limit concurrency. | |
683 | * There's no point in executing many of these in parallel. | |
684 | */ | |
685 | cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1); | |
686 | if (!cgwb_release_wq) | |
687 | return -ENOMEM; | |
688 | ||
689 | return 0; | |
690 | } | |
691 | subsys_initcall(cgwb_init); | |
692 | ||
693 | #else /* CONFIG_CGROUP_WRITEBACK */ | |
694 | ||
695 | static int cgwb_bdi_init(struct backing_dev_info *bdi) | |
696 | { | |
697 | return wb_init(&bdi->wb, bdi, GFP_KERNEL); | |
698 | } | |
699 | ||
700 | static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { } | |
701 | ||
702 | static void cgwb_bdi_register(struct backing_dev_info *bdi) | |
703 | { | |
704 | list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list); | |
705 | } | |
706 | ||
707 | static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb) | |
708 | { | |
709 | list_del_rcu(&wb->bdi_node); | |
710 | } | |
711 | ||
712 | #endif /* CONFIG_CGROUP_WRITEBACK */ | |
713 | ||
714 | static int bdi_init(struct backing_dev_info *bdi) | |
715 | { | |
716 | int ret; | |
717 | ||
718 | bdi->dev = NULL; | |
719 | ||
720 | kref_init(&bdi->refcnt); | |
721 | bdi->min_ratio = 0; | |
722 | bdi->max_ratio = 100; | |
723 | bdi->max_prop_frac = FPROP_FRAC_BASE; | |
724 | INIT_LIST_HEAD(&bdi->bdi_list); | |
725 | INIT_LIST_HEAD(&bdi->wb_list); | |
726 | init_waitqueue_head(&bdi->wb_waitq); | |
727 | ||
728 | ret = cgwb_bdi_init(bdi); | |
729 | ||
730 | return ret; | |
731 | } | |
732 | ||
733 | struct backing_dev_info *bdi_alloc(int node_id) | |
734 | { | |
735 | struct backing_dev_info *bdi; | |
736 | ||
737 | bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id); | |
738 | if (!bdi) | |
739 | return NULL; | |
740 | ||
741 | if (bdi_init(bdi)) { | |
742 | kfree(bdi); | |
743 | return NULL; | |
744 | } | |
745 | bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT; | |
746 | bdi->ra_pages = VM_READAHEAD_PAGES; | |
747 | bdi->io_pages = VM_READAHEAD_PAGES; | |
748 | return bdi; | |
749 | } | |
750 | EXPORT_SYMBOL(bdi_alloc); | |
751 | ||
752 | static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp) | |
753 | { | |
754 | struct rb_node **p = &bdi_tree.rb_node; | |
755 | struct rb_node *parent = NULL; | |
756 | struct backing_dev_info *bdi; | |
757 | ||
758 | lockdep_assert_held(&bdi_lock); | |
759 | ||
760 | while (*p) { | |
761 | parent = *p; | |
762 | bdi = rb_entry(parent, struct backing_dev_info, rb_node); | |
763 | ||
764 | if (bdi->id > id) | |
765 | p = &(*p)->rb_left; | |
766 | else if (bdi->id < id) | |
767 | p = &(*p)->rb_right; | |
768 | else | |
769 | break; | |
770 | } | |
771 | ||
772 | if (parentp) | |
773 | *parentp = parent; | |
774 | return p; | |
775 | } | |
776 | ||
777 | /** | |
778 | * bdi_get_by_id - lookup and get bdi from its id | |
779 | * @id: bdi id to lookup | |
780 | * | |
781 | * Find bdi matching @id and get it. Returns NULL if the matching bdi | |
782 | * doesn't exist or is already unregistered. | |
783 | */ | |
784 | struct backing_dev_info *bdi_get_by_id(u64 id) | |
785 | { | |
786 | struct backing_dev_info *bdi = NULL; | |
787 | struct rb_node **p; | |
788 | ||
789 | spin_lock_bh(&bdi_lock); | |
790 | p = bdi_lookup_rb_node(id, NULL); | |
791 | if (*p) { | |
792 | bdi = rb_entry(*p, struct backing_dev_info, rb_node); | |
793 | bdi_get(bdi); | |
794 | } | |
795 | spin_unlock_bh(&bdi_lock); | |
796 | ||
797 | return bdi; | |
798 | } | |
799 | ||
800 | int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args) | |
801 | { | |
802 | struct device *dev; | |
803 | struct rb_node *parent, **p; | |
804 | ||
805 | if (bdi->dev) /* The driver needs to use separate queues per device */ | |
806 | return 0; | |
807 | ||
808 | vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args); | |
809 | dev = device_create(bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name); | |
810 | if (IS_ERR(dev)) | |
811 | return PTR_ERR(dev); | |
812 | ||
813 | cgwb_bdi_register(bdi); | |
814 | bdi->dev = dev; | |
815 | ||
816 | bdi_debug_register(bdi, dev_name(dev)); | |
817 | set_bit(WB_registered, &bdi->wb.state); | |
818 | ||
819 | spin_lock_bh(&bdi_lock); | |
820 | ||
821 | bdi->id = ++bdi_id_cursor; | |
822 | ||
823 | p = bdi_lookup_rb_node(bdi->id, &parent); | |
824 | rb_link_node(&bdi->rb_node, parent, p); | |
825 | rb_insert_color(&bdi->rb_node, &bdi_tree); | |
826 | ||
827 | list_add_tail_rcu(&bdi->bdi_list, &bdi_list); | |
828 | ||
829 | spin_unlock_bh(&bdi_lock); | |
830 | ||
831 | trace_writeback_bdi_register(bdi); | |
832 | return 0; | |
833 | } | |
834 | ||
835 | int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...) | |
836 | { | |
837 | va_list args; | |
838 | int ret; | |
839 | ||
840 | va_start(args, fmt); | |
841 | ret = bdi_register_va(bdi, fmt, args); | |
842 | va_end(args); | |
843 | return ret; | |
844 | } | |
845 | EXPORT_SYMBOL(bdi_register); | |
846 | ||
847 | void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner) | |
848 | { | |
849 | WARN_ON_ONCE(bdi->owner); | |
850 | bdi->owner = owner; | |
851 | get_device(owner); | |
852 | } | |
853 | ||
854 | /* | |
855 | * Remove bdi from bdi_list, and ensure that it is no longer visible | |
856 | */ | |
857 | static void bdi_remove_from_list(struct backing_dev_info *bdi) | |
858 | { | |
859 | spin_lock_bh(&bdi_lock); | |
860 | rb_erase(&bdi->rb_node, &bdi_tree); | |
861 | list_del_rcu(&bdi->bdi_list); | |
862 | spin_unlock_bh(&bdi_lock); | |
863 | ||
864 | synchronize_rcu_expedited(); | |
865 | } | |
866 | ||
867 | void bdi_unregister(struct backing_dev_info *bdi) | |
868 | { | |
869 | /* make sure nobody finds us on the bdi_list anymore */ | |
870 | bdi_remove_from_list(bdi); | |
871 | wb_shutdown(&bdi->wb); | |
872 | cgwb_bdi_unregister(bdi); | |
873 | ||
874 | if (bdi->dev) { | |
875 | bdi_debug_unregister(bdi); | |
876 | device_unregister(bdi->dev); | |
877 | bdi->dev = NULL; | |
878 | } | |
879 | ||
880 | if (bdi->owner) { | |
881 | put_device(bdi->owner); | |
882 | bdi->owner = NULL; | |
883 | } | |
884 | } | |
885 | ||
886 | static void release_bdi(struct kref *ref) | |
887 | { | |
888 | struct backing_dev_info *bdi = | |
889 | container_of(ref, struct backing_dev_info, refcnt); | |
890 | ||
891 | if (test_bit(WB_registered, &bdi->wb.state)) | |
892 | bdi_unregister(bdi); | |
893 | WARN_ON_ONCE(bdi->dev); | |
894 | wb_exit(&bdi->wb); | |
895 | kfree(bdi); | |
896 | } | |
897 | ||
898 | void bdi_put(struct backing_dev_info *bdi) | |
899 | { | |
900 | kref_put(&bdi->refcnt, release_bdi); | |
901 | } | |
902 | EXPORT_SYMBOL(bdi_put); | |
903 | ||
904 | const char *bdi_dev_name(struct backing_dev_info *bdi) | |
905 | { | |
906 | if (!bdi || !bdi->dev) | |
907 | return bdi_unknown_name; | |
908 | return bdi->dev_name; | |
909 | } | |
910 | EXPORT_SYMBOL_GPL(bdi_dev_name); | |
911 | ||
912 | static wait_queue_head_t congestion_wqh[2] = { | |
913 | __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]), | |
914 | __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1]) | |
915 | }; | |
916 | static atomic_t nr_wb_congested[2]; | |
917 | ||
918 | void clear_bdi_congested(struct backing_dev_info *bdi, int sync) | |
919 | { | |
920 | wait_queue_head_t *wqh = &congestion_wqh[sync]; | |
921 | enum wb_congested_state bit; | |
922 | ||
923 | bit = sync ? WB_sync_congested : WB_async_congested; | |
924 | if (test_and_clear_bit(bit, &bdi->wb.congested)) | |
925 | atomic_dec(&nr_wb_congested[sync]); | |
926 | smp_mb__after_atomic(); | |
927 | if (waitqueue_active(wqh)) | |
928 | wake_up(wqh); | |
929 | } | |
930 | EXPORT_SYMBOL(clear_bdi_congested); | |
931 | ||
932 | void set_bdi_congested(struct backing_dev_info *bdi, int sync) | |
933 | { | |
934 | enum wb_congested_state bit; | |
935 | ||
936 | bit = sync ? WB_sync_congested : WB_async_congested; | |
937 | if (!test_and_set_bit(bit, &bdi->wb.congested)) | |
938 | atomic_inc(&nr_wb_congested[sync]); | |
939 | } | |
940 | EXPORT_SYMBOL(set_bdi_congested); | |
941 | ||
942 | /** | |
943 | * congestion_wait - wait for a backing_dev to become uncongested | |
944 | * @sync: SYNC or ASYNC IO | |
945 | * @timeout: timeout in jiffies | |
946 | * | |
947 | * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit | |
948 | * write congestion. If no backing_devs are congested then just wait for the | |
949 | * next write to be completed. | |
950 | */ | |
951 | long congestion_wait(int sync, long timeout) | |
952 | { | |
953 | long ret; | |
954 | unsigned long start = jiffies; | |
955 | DEFINE_WAIT(wait); | |
956 | wait_queue_head_t *wqh = &congestion_wqh[sync]; | |
957 | ||
958 | prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE); | |
959 | ret = io_schedule_timeout(timeout); | |
960 | finish_wait(wqh, &wait); | |
961 | ||
962 | trace_writeback_congestion_wait(jiffies_to_usecs(timeout), | |
963 | jiffies_to_usecs(jiffies - start)); | |
964 | ||
965 | return ret; | |
966 | } | |
967 | EXPORT_SYMBOL(congestion_wait); | |
968 | ||
969 | /** | |
970 | * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a pgdat to complete writes | |
971 | * @sync: SYNC or ASYNC IO | |
972 | * @timeout: timeout in jiffies | |
973 | * | |
974 | * In the event of a congested backing_dev (any backing_dev) this waits | |
975 | * for up to @timeout jiffies for either a BDI to exit congestion of the | |
976 | * given @sync queue or a write to complete. | |
977 | * | |
978 | * The return value is 0 if the sleep is for the full timeout. Otherwise, | |
979 | * it is the number of jiffies that were still remaining when the function | |
980 | * returned. return_value == timeout implies the function did not sleep. | |
981 | */ | |
982 | long wait_iff_congested(int sync, long timeout) | |
983 | { | |
984 | long ret; | |
985 | unsigned long start = jiffies; | |
986 | DEFINE_WAIT(wait); | |
987 | wait_queue_head_t *wqh = &congestion_wqh[sync]; | |
988 | ||
989 | /* | |
990 | * If there is no congestion, yield if necessary instead | |
991 | * of sleeping on the congestion queue | |
992 | */ | |
993 | if (atomic_read(&nr_wb_congested[sync]) == 0) { | |
994 | cond_resched(); | |
995 | ||
996 | /* In case we scheduled, work out time remaining */ | |
997 | ret = timeout - (jiffies - start); | |
998 | if (ret < 0) | |
999 | ret = 0; | |
1000 | ||
1001 | goto out; | |
1002 | } | |
1003 | ||
1004 | /* Sleep until uncongested or a write happens */ | |
1005 | prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE); | |
1006 | ret = io_schedule_timeout(timeout); | |
1007 | finish_wait(wqh, &wait); | |
1008 | ||
1009 | out: | |
1010 | trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout), | |
1011 | jiffies_to_usecs(jiffies - start)); | |
1012 | ||
1013 | return ret; | |
1014 | } | |
1015 | EXPORT_SYMBOL(wait_iff_congested); |