1 | |
2 | #include <linux/wait.h> |
3 | #include <linux/backing-dev.h> |
4 | #include <linux/kthread.h> |
5 | #include <linux/freezer.h> |
6 | #include <linux/fs.h> |
7 | #include <linux/pagemap.h> |
8 | #include <linux/mm.h> |
9 | #include <linux/sched.h> |
10 | #include <linux/module.h> |
11 | #include <linux/writeback.h> |
12 | #include <linux/device.h> |
13 | #include <trace/events/writeback.h> |
14 | |
15 | struct backing_dev_info noop_backing_dev_info = { |
16 | .name = "noop" , |
17 | .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK, |
18 | }; |
19 | EXPORT_SYMBOL_GPL(noop_backing_dev_info); |
20 | |
21 | static struct class *bdi_class; |
22 | |
23 | /* |
24 | * bdi_lock protects updates to bdi_list. bdi_list has RCU reader side |
25 | * locking. |
26 | */ |
27 | DEFINE_SPINLOCK(bdi_lock); |
28 | LIST_HEAD(bdi_list); |
29 | |
30 | /* bdi_wq serves all asynchronous writeback tasks */ |
31 | struct workqueue_struct *bdi_wq; |
32 | |
33 | #ifdef CONFIG_DEBUG_FS |
34 | #include <linux/debugfs.h> |
35 | #include <linux/seq_file.h> |
36 | |
37 | static struct dentry *bdi_debug_root; |
38 | |
39 | static void bdi_debug_init(void) |
40 | { |
41 | bdi_debug_root = debugfs_create_dir("bdi" , NULL); |
42 | } |
43 | |
44 | static int bdi_debug_stats_show(struct seq_file *m, void *v) |
45 | { |
46 | struct backing_dev_info *bdi = m->private; |
47 | struct bdi_writeback *wb = &bdi->wb; |
48 | unsigned long background_thresh; |
49 | unsigned long dirty_thresh; |
50 | unsigned long wb_thresh; |
51 | unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time; |
52 | struct inode *inode; |
53 | |
54 | nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0; |
55 | spin_lock(&wb->list_lock); |
56 | list_for_each_entry(inode, &wb->b_dirty, i_io_list) |
57 | nr_dirty++; |
58 | list_for_each_entry(inode, &wb->b_io, i_io_list) |
59 | nr_io++; |
60 | list_for_each_entry(inode, &wb->b_more_io, i_io_list) |
61 | nr_more_io++; |
62 | list_for_each_entry(inode, &wb->b_dirty_time, i_io_list) |
63 | if (inode->i_state & I_DIRTY_TIME) |
64 | nr_dirty_time++; |
65 | spin_unlock(&wb->list_lock); |
66 | |
67 | global_dirty_limits(&background_thresh, &dirty_thresh); |
68 | wb_thresh = wb_calc_thresh(wb, dirty_thresh); |
69 | |
70 | #define K(x) ((x) << (PAGE_SHIFT - 10)) |
71 | seq_printf(m, |
72 | "BdiWriteback: %10lu kB\n" |
73 | "BdiReclaimable: %10lu kB\n" |
74 | "BdiDirtyThresh: %10lu kB\n" |
75 | "DirtyThresh: %10lu kB\n" |
76 | "BackgroundThresh: %10lu kB\n" |
77 | "BdiDirtied: %10lu kB\n" |
78 | "BdiWritten: %10lu kB\n" |
79 | "BdiWriteBandwidth: %10lu kBps\n" |
80 | "b_dirty: %10lu\n" |
81 | "b_io: %10lu\n" |
82 | "b_more_io: %10lu\n" |
83 | "b_dirty_time: %10lu\n" |
84 | "bdi_list: %10u\n" |
85 | "state: %10lx\n" , |
86 | (unsigned long) K(wb_stat(wb, WB_WRITEBACK)), |
87 | (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)), |
88 | K(wb_thresh), |
89 | K(dirty_thresh), |
90 | K(background_thresh), |
91 | (unsigned long) K(wb_stat(wb, WB_DIRTIED)), |
92 | (unsigned long) K(wb_stat(wb, WB_WRITTEN)), |
93 | (unsigned long) K(wb->write_bandwidth), |
94 | nr_dirty, |
95 | nr_io, |
96 | nr_more_io, |
97 | nr_dirty_time, |
98 | !list_empty(&bdi->bdi_list), bdi->wb.state); |
99 | #undef K |
100 | |
101 | return 0; |
102 | } |
103 | DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats); |
104 | |
105 | static int bdi_debug_register(struct backing_dev_info *bdi, const char *name) |
106 | { |
107 | if (!bdi_debug_root) |
108 | return -ENOMEM; |
109 | |
110 | bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root); |
111 | if (!bdi->debug_dir) |
112 | return -ENOMEM; |
113 | |
114 | bdi->debug_stats = debugfs_create_file("stats" , 0444, bdi->debug_dir, |
115 | bdi, &bdi_debug_stats_fops); |
116 | if (!bdi->debug_stats) { |
117 | debugfs_remove(bdi->debug_dir); |
118 | bdi->debug_dir = NULL; |
119 | return -ENOMEM; |
120 | } |
121 | |
122 | return 0; |
123 | } |
124 | |
125 | static void bdi_debug_unregister(struct backing_dev_info *bdi) |
126 | { |
127 | debugfs_remove(bdi->debug_stats); |
128 | debugfs_remove(bdi->debug_dir); |
129 | } |
130 | #else |
131 | static inline void bdi_debug_init(void) |
132 | { |
133 | } |
134 | static inline int bdi_debug_register(struct backing_dev_info *bdi, |
135 | const char *name) |
136 | { |
137 | return 0; |
138 | } |
139 | static inline void bdi_debug_unregister(struct backing_dev_info *bdi) |
140 | { |
141 | } |
142 | #endif |
143 | |
144 | static ssize_t read_ahead_kb_store(struct device *dev, |
145 | struct device_attribute *attr, |
146 | const char *buf, size_t count) |
147 | { |
148 | struct backing_dev_info *bdi = dev_get_drvdata(dev); |
149 | unsigned long read_ahead_kb; |
150 | ssize_t ret; |
151 | |
152 | ret = kstrtoul(buf, 10, &read_ahead_kb); |
153 | if (ret < 0) |
154 | return ret; |
155 | |
156 | bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10); |
157 | |
158 | return count; |
159 | } |
160 | |
161 | #define K(pages) ((pages) << (PAGE_SHIFT - 10)) |
162 | |
163 | #define BDI_SHOW(name, expr) \ |
164 | static ssize_t name##_show(struct device *dev, \ |
165 | struct device_attribute *attr, char *page) \ |
166 | { \ |
167 | struct backing_dev_info *bdi = dev_get_drvdata(dev); \ |
168 | \ |
169 | return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \ |
170 | } \ |
171 | static DEVICE_ATTR_RW(name); |
172 | |
173 | BDI_SHOW(read_ahead_kb, K(bdi->ra_pages)) |
174 | |
175 | static ssize_t min_ratio_store(struct device *dev, |
176 | struct device_attribute *attr, const char *buf, size_t count) |
177 | { |
178 | struct backing_dev_info *bdi = dev_get_drvdata(dev); |
179 | unsigned int ratio; |
180 | ssize_t ret; |
181 | |
182 | ret = kstrtouint(buf, 10, &ratio); |
183 | if (ret < 0) |
184 | return ret; |
185 | |
186 | ret = bdi_set_min_ratio(bdi, ratio); |
187 | if (!ret) |
188 | ret = count; |
189 | |
190 | return ret; |
191 | } |
192 | BDI_SHOW(min_ratio, bdi->min_ratio) |
193 | |
194 | static ssize_t max_ratio_store(struct device *dev, |
195 | struct device_attribute *attr, const char *buf, size_t count) |
196 | { |
197 | struct backing_dev_info *bdi = dev_get_drvdata(dev); |
198 | unsigned int ratio; |
199 | ssize_t ret; |
200 | |
201 | ret = kstrtouint(buf, 10, &ratio); |
202 | if (ret < 0) |
203 | return ret; |
204 | |
205 | ret = bdi_set_max_ratio(bdi, ratio); |
206 | if (!ret) |
207 | ret = count; |
208 | |
209 | return ret; |
210 | } |
211 | BDI_SHOW(max_ratio, bdi->max_ratio) |
212 | |
213 | static ssize_t stable_pages_required_show(struct device *dev, |
214 | struct device_attribute *attr, |
215 | char *page) |
216 | { |
217 | struct backing_dev_info *bdi = dev_get_drvdata(dev); |
218 | |
219 | return snprintf(page, PAGE_SIZE-1, "%d\n" , |
220 | bdi_cap_stable_pages_required(bdi) ? 1 : 0); |
221 | } |
222 | static DEVICE_ATTR_RO(stable_pages_required); |
223 | |
224 | static struct attribute *bdi_dev_attrs[] = { |
225 | &dev_attr_read_ahead_kb.attr, |
226 | &dev_attr_min_ratio.attr, |
227 | &dev_attr_max_ratio.attr, |
228 | &dev_attr_stable_pages_required.attr, |
229 | NULL, |
230 | }; |
231 | ATTRIBUTE_GROUPS(bdi_dev); |
232 | |
233 | static __init int bdi_class_init(void) |
234 | { |
235 | bdi_class = class_create(THIS_MODULE, "bdi" ); |
236 | if (IS_ERR(bdi_class)) |
237 | return PTR_ERR(bdi_class); |
238 | |
239 | bdi_class->dev_groups = bdi_dev_groups; |
240 | bdi_debug_init(); |
241 | |
242 | return 0; |
243 | } |
244 | postcore_initcall(bdi_class_init); |
245 | |
246 | static int bdi_init(struct backing_dev_info *bdi); |
247 | |
248 | static int __init default_bdi_init(void) |
249 | { |
250 | int err; |
251 | |
252 | bdi_wq = alloc_workqueue("writeback" , WQ_MEM_RECLAIM | WQ_FREEZABLE | |
253 | WQ_UNBOUND | WQ_SYSFS, 0); |
254 | if (!bdi_wq) |
255 | return -ENOMEM; |
256 | |
257 | err = bdi_init(&noop_backing_dev_info); |
258 | |
259 | return err; |
260 | } |
261 | subsys_initcall(default_bdi_init); |
262 | |
263 | /* |
264 | * This function is used when the first inode for this wb is marked dirty. It |
265 | * wakes-up the corresponding bdi thread which should then take care of the |
266 | * periodic background write-out of dirty inodes. Since the write-out would |
267 | * starts only 'dirty_writeback_interval' centisecs from now anyway, we just |
268 | * set up a timer which wakes the bdi thread up later. |
269 | * |
270 | * Note, we wouldn't bother setting up the timer, but this function is on the |
271 | * fast-path (used by '__mark_inode_dirty()'), so we save few context switches |
272 | * by delaying the wake-up. |
273 | * |
274 | * We have to be careful not to postpone flush work if it is scheduled for |
275 | * earlier. Thus we use queue_delayed_work(). |
276 | */ |
277 | void wb_wakeup_delayed(struct bdi_writeback *wb) |
278 | { |
279 | unsigned long timeout; |
280 | |
281 | timeout = msecs_to_jiffies(dirty_writeback_interval * 10); |
282 | spin_lock_bh(&wb->work_lock); |
283 | if (test_bit(WB_registered, &wb->state)) |
284 | queue_delayed_work(bdi_wq, &wb->dwork, timeout); |
285 | spin_unlock_bh(&wb->work_lock); |
286 | } |
287 | |
288 | /* |
289 | * Initial write bandwidth: 100 MB/s |
290 | */ |
291 | #define INIT_BW (100 << (20 - PAGE_SHIFT)) |
292 | |
293 | static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi, |
294 | int blkcg_id, gfp_t gfp) |
295 | { |
296 | int i, err; |
297 | |
298 | memset(wb, 0, sizeof(*wb)); |
299 | |
300 | if (wb != &bdi->wb) |
301 | bdi_get(bdi); |
302 | wb->bdi = bdi; |
303 | wb->last_old_flush = jiffies; |
304 | INIT_LIST_HEAD(&wb->b_dirty); |
305 | INIT_LIST_HEAD(&wb->b_io); |
306 | INIT_LIST_HEAD(&wb->b_more_io); |
307 | INIT_LIST_HEAD(&wb->b_dirty_time); |
308 | spin_lock_init(&wb->list_lock); |
309 | |
310 | wb->bw_time_stamp = jiffies; |
311 | wb->balanced_dirty_ratelimit = INIT_BW; |
312 | wb->dirty_ratelimit = INIT_BW; |
313 | wb->write_bandwidth = INIT_BW; |
314 | wb->avg_write_bandwidth = INIT_BW; |
315 | |
316 | spin_lock_init(&wb->work_lock); |
317 | INIT_LIST_HEAD(&wb->work_list); |
318 | INIT_DELAYED_WORK(&wb->dwork, wb_workfn); |
319 | wb->dirty_sleep = jiffies; |
320 | |
321 | wb->congested = wb_congested_get_create(bdi, blkcg_id, gfp); |
322 | if (!wb->congested) { |
323 | err = -ENOMEM; |
324 | goto out_put_bdi; |
325 | } |
326 | |
327 | err = fprop_local_init_percpu(&wb->completions, gfp); |
328 | if (err) |
329 | goto out_put_cong; |
330 | |
331 | for (i = 0; i < NR_WB_STAT_ITEMS; i++) { |
332 | err = percpu_counter_init(&wb->stat[i], 0, gfp); |
333 | if (err) |
334 | goto out_destroy_stat; |
335 | } |
336 | |
337 | return 0; |
338 | |
339 | out_destroy_stat: |
340 | while (i--) |
341 | percpu_counter_destroy(&wb->stat[i]); |
342 | fprop_local_destroy_percpu(&wb->completions); |
343 | out_put_cong: |
344 | wb_congested_put(wb->congested); |
345 | out_put_bdi: |
346 | if (wb != &bdi->wb) |
347 | bdi_put(bdi); |
348 | return err; |
349 | } |
350 | |
351 | static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb); |
352 | |
353 | /* |
354 | * Remove bdi from the global list and shutdown any threads we have running |
355 | */ |
356 | static void wb_shutdown(struct bdi_writeback *wb) |
357 | { |
358 | /* Make sure nobody queues further work */ |
359 | spin_lock_bh(&wb->work_lock); |
360 | if (!test_and_clear_bit(WB_registered, &wb->state)) { |
361 | spin_unlock_bh(&wb->work_lock); |
362 | return; |
363 | } |
364 | spin_unlock_bh(&wb->work_lock); |
365 | |
366 | cgwb_remove_from_bdi_list(wb); |
367 | /* |
368 | * Drain work list and shutdown the delayed_work. !WB_registered |
369 | * tells wb_workfn() that @wb is dying and its work_list needs to |
370 | * be drained no matter what. |
371 | */ |
372 | mod_delayed_work(bdi_wq, &wb->dwork, 0); |
373 | flush_delayed_work(&wb->dwork); |
374 | WARN_ON(!list_empty(&wb->work_list)); |
375 | } |
376 | |
377 | static void wb_exit(struct bdi_writeback *wb) |
378 | { |
379 | int i; |
380 | |
381 | WARN_ON(delayed_work_pending(&wb->dwork)); |
382 | |
383 | for (i = 0; i < NR_WB_STAT_ITEMS; i++) |
384 | percpu_counter_destroy(&wb->stat[i]); |
385 | |
386 | fprop_local_destroy_percpu(&wb->completions); |
387 | wb_congested_put(wb->congested); |
388 | if (wb != &wb->bdi->wb) |
389 | bdi_put(wb->bdi); |
390 | } |
391 | |
392 | #ifdef CONFIG_CGROUP_WRITEBACK |
393 | |
394 | #include <linux/memcontrol.h> |
395 | |
396 | /* |
397 | * cgwb_lock protects bdi->cgwb_tree, bdi->cgwb_congested_tree, |
398 | * blkcg->cgwb_list, and memcg->cgwb_list. bdi->cgwb_tree is also RCU |
399 | * protected. |
400 | */ |
401 | static DEFINE_SPINLOCK(cgwb_lock); |
402 | static struct workqueue_struct *cgwb_release_wq; |
403 | |
404 | /** |
405 | * wb_congested_get_create - get or create a wb_congested |
406 | * @bdi: associated bdi |
407 | * @blkcg_id: ID of the associated blkcg |
408 | * @gfp: allocation mask |
409 | * |
410 | * Look up the wb_congested for @blkcg_id on @bdi. If missing, create one. |
411 | * The returned wb_congested has its reference count incremented. Returns |
412 | * NULL on failure. |
413 | */ |
414 | struct bdi_writeback_congested * |
415 | wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp) |
416 | { |
417 | struct bdi_writeback_congested *new_congested = NULL, *congested; |
418 | struct rb_node **node, *parent; |
419 | unsigned long flags; |
420 | retry: |
421 | spin_lock_irqsave(&cgwb_lock, flags); |
422 | |
423 | node = &bdi->cgwb_congested_tree.rb_node; |
424 | parent = NULL; |
425 | |
426 | while (*node != NULL) { |
427 | parent = *node; |
428 | congested = rb_entry(parent, struct bdi_writeback_congested, |
429 | rb_node); |
430 | if (congested->blkcg_id < blkcg_id) |
431 | node = &parent->rb_left; |
432 | else if (congested->blkcg_id > blkcg_id) |
433 | node = &parent->rb_right; |
434 | else |
435 | goto found; |
436 | } |
437 | |
438 | if (new_congested) { |
439 | /* !found and storage for new one already allocated, insert */ |
440 | congested = new_congested; |
441 | rb_link_node(&congested->rb_node, parent, node); |
442 | rb_insert_color(&congested->rb_node, &bdi->cgwb_congested_tree); |
443 | spin_unlock_irqrestore(&cgwb_lock, flags); |
444 | return congested; |
445 | } |
446 | |
447 | spin_unlock_irqrestore(&cgwb_lock, flags); |
448 | |
449 | /* allocate storage for new one and retry */ |
450 | new_congested = kzalloc(sizeof(*new_congested), gfp); |
451 | if (!new_congested) |
452 | return NULL; |
453 | |
454 | refcount_set(&new_congested->refcnt, 1); |
455 | new_congested->__bdi = bdi; |
456 | new_congested->blkcg_id = blkcg_id; |
457 | goto retry; |
458 | |
459 | found: |
460 | refcount_inc(&congested->refcnt); |
461 | spin_unlock_irqrestore(&cgwb_lock, flags); |
462 | kfree(new_congested); |
463 | return congested; |
464 | } |
465 | |
466 | /** |
467 | * wb_congested_put - put a wb_congested |
468 | * @congested: wb_congested to put |
469 | * |
470 | * Put @congested and destroy it if the refcnt reaches zero. |
471 | */ |
472 | void wb_congested_put(struct bdi_writeback_congested *congested) |
473 | { |
474 | unsigned long flags; |
475 | |
476 | if (!refcount_dec_and_lock_irqsave(&congested->refcnt, &cgwb_lock, &flags)) |
477 | return; |
478 | |
479 | /* bdi might already have been destroyed leaving @congested unlinked */ |
480 | if (congested->__bdi) { |
481 | rb_erase(&congested->rb_node, |
482 | &congested->__bdi->cgwb_congested_tree); |
483 | congested->__bdi = NULL; |
484 | } |
485 | |
486 | spin_unlock_irqrestore(&cgwb_lock, flags); |
487 | kfree(congested); |
488 | } |
489 | |
490 | static void cgwb_release_workfn(struct work_struct *work) |
491 | { |
492 | struct bdi_writeback *wb = container_of(work, struct bdi_writeback, |
493 | release_work); |
494 | struct blkcg *blkcg = css_to_blkcg(wb->blkcg_css); |
495 | |
496 | mutex_lock(&wb->bdi->cgwb_release_mutex); |
497 | wb_shutdown(wb); |
498 | |
499 | css_put(wb->memcg_css); |
500 | css_put(wb->blkcg_css); |
501 | mutex_unlock(&wb->bdi->cgwb_release_mutex); |
502 | |
503 | /* triggers blkg destruction if cgwb_refcnt becomes zero */ |
504 | blkcg_cgwb_put(blkcg); |
505 | |
506 | fprop_local_destroy_percpu(&wb->memcg_completions); |
507 | percpu_ref_exit(&wb->refcnt); |
508 | wb_exit(wb); |
509 | kfree_rcu(wb, rcu); |
510 | } |
511 | |
512 | static void cgwb_release(struct percpu_ref *refcnt) |
513 | { |
514 | struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback, |
515 | refcnt); |
516 | queue_work(cgwb_release_wq, &wb->release_work); |
517 | } |
518 | |
519 | static void cgwb_kill(struct bdi_writeback *wb) |
520 | { |
521 | lockdep_assert_held(&cgwb_lock); |
522 | |
523 | WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id)); |
524 | list_del(&wb->memcg_node); |
525 | list_del(&wb->blkcg_node); |
526 | percpu_ref_kill(&wb->refcnt); |
527 | } |
528 | |
529 | static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb) |
530 | { |
531 | spin_lock_irq(&cgwb_lock); |
532 | list_del_rcu(&wb->bdi_node); |
533 | spin_unlock_irq(&cgwb_lock); |
534 | } |
535 | |
536 | static int cgwb_create(struct backing_dev_info *bdi, |
537 | struct cgroup_subsys_state *memcg_css, gfp_t gfp) |
538 | { |
539 | struct mem_cgroup *memcg; |
540 | struct cgroup_subsys_state *blkcg_css; |
541 | struct blkcg *blkcg; |
542 | struct list_head *memcg_cgwb_list, *blkcg_cgwb_list; |
543 | struct bdi_writeback *wb; |
544 | unsigned long flags; |
545 | int ret = 0; |
546 | |
547 | memcg = mem_cgroup_from_css(memcg_css); |
548 | blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys); |
549 | blkcg = css_to_blkcg(blkcg_css); |
550 | memcg_cgwb_list = &memcg->cgwb_list; |
551 | blkcg_cgwb_list = &blkcg->cgwb_list; |
552 | |
553 | /* look up again under lock and discard on blkcg mismatch */ |
554 | spin_lock_irqsave(&cgwb_lock, flags); |
555 | wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id); |
556 | if (wb && wb->blkcg_css != blkcg_css) { |
557 | cgwb_kill(wb); |
558 | wb = NULL; |
559 | } |
560 | spin_unlock_irqrestore(&cgwb_lock, flags); |
561 | if (wb) |
562 | goto out_put; |
563 | |
564 | /* need to create a new one */ |
565 | wb = kmalloc(sizeof(*wb), gfp); |
566 | if (!wb) { |
567 | ret = -ENOMEM; |
568 | goto out_put; |
569 | } |
570 | |
571 | ret = wb_init(wb, bdi, blkcg_css->id, gfp); |
572 | if (ret) |
573 | goto err_free; |
574 | |
575 | ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp); |
576 | if (ret) |
577 | goto err_wb_exit; |
578 | |
579 | ret = fprop_local_init_percpu(&wb->memcg_completions, gfp); |
580 | if (ret) |
581 | goto err_ref_exit; |
582 | |
583 | wb->memcg_css = memcg_css; |
584 | wb->blkcg_css = blkcg_css; |
585 | INIT_WORK(&wb->release_work, cgwb_release_workfn); |
586 | set_bit(WB_registered, &wb->state); |
587 | |
588 | /* |
589 | * The root wb determines the registered state of the whole bdi and |
590 | * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate |
591 | * whether they're still online. Don't link @wb if any is dead. |
592 | * See wb_memcg_offline() and wb_blkcg_offline(). |
593 | */ |
594 | ret = -ENODEV; |
595 | spin_lock_irqsave(&cgwb_lock, flags); |
596 | if (test_bit(WB_registered, &bdi->wb.state) && |
597 | blkcg_cgwb_list->next && memcg_cgwb_list->next) { |
598 | /* we might have raced another instance of this function */ |
599 | ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb); |
600 | if (!ret) { |
601 | list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list); |
602 | list_add(&wb->memcg_node, memcg_cgwb_list); |
603 | list_add(&wb->blkcg_node, blkcg_cgwb_list); |
604 | blkcg_cgwb_get(blkcg); |
605 | css_get(memcg_css); |
606 | css_get(blkcg_css); |
607 | } |
608 | } |
609 | spin_unlock_irqrestore(&cgwb_lock, flags); |
610 | if (ret) { |
611 | if (ret == -EEXIST) |
612 | ret = 0; |
613 | goto err_fprop_exit; |
614 | } |
615 | goto out_put; |
616 | |
617 | err_fprop_exit: |
618 | fprop_local_destroy_percpu(&wb->memcg_completions); |
619 | err_ref_exit: |
620 | percpu_ref_exit(&wb->refcnt); |
621 | err_wb_exit: |
622 | wb_exit(wb); |
623 | err_free: |
624 | kfree(wb); |
625 | out_put: |
626 | css_put(blkcg_css); |
627 | return ret; |
628 | } |
629 | |
630 | /** |
631 | * wb_get_create - get wb for a given memcg, create if necessary |
632 | * @bdi: target bdi |
633 | * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref) |
634 | * @gfp: allocation mask to use |
635 | * |
636 | * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to |
637 | * create one. The returned wb has its refcount incremented. |
638 | * |
639 | * This function uses css_get() on @memcg_css and thus expects its refcnt |
640 | * to be positive on invocation. IOW, rcu_read_lock() protection on |
641 | * @memcg_css isn't enough. try_get it before calling this function. |
642 | * |
643 | * A wb is keyed by its associated memcg. As blkcg implicitly enables |
644 | * memcg on the default hierarchy, memcg association is guaranteed to be |
645 | * more specific (equal or descendant to the associated blkcg) and thus can |
646 | * identify both the memcg and blkcg associations. |
647 | * |
648 | * Because the blkcg associated with a memcg may change as blkcg is enabled |
649 | * and disabled closer to root in the hierarchy, each wb keeps track of |
650 | * both the memcg and blkcg associated with it and verifies the blkcg on |
651 | * each lookup. On mismatch, the existing wb is discarded and a new one is |
652 | * created. |
653 | */ |
654 | struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi, |
655 | struct cgroup_subsys_state *memcg_css, |
656 | gfp_t gfp) |
657 | { |
658 | struct bdi_writeback *wb; |
659 | |
660 | might_sleep_if(gfpflags_allow_blocking(gfp)); |
661 | |
662 | if (!memcg_css->parent) |
663 | return &bdi->wb; |
664 | |
665 | do { |
666 | rcu_read_lock(); |
667 | wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id); |
668 | if (wb) { |
669 | struct cgroup_subsys_state *blkcg_css; |
670 | |
671 | /* see whether the blkcg association has changed */ |
672 | blkcg_css = cgroup_get_e_css(memcg_css->cgroup, |
673 | &io_cgrp_subsys); |
674 | if (unlikely(wb->blkcg_css != blkcg_css || |
675 | !wb_tryget(wb))) |
676 | wb = NULL; |
677 | css_put(blkcg_css); |
678 | } |
679 | rcu_read_unlock(); |
680 | } while (!wb && !cgwb_create(bdi, memcg_css, gfp)); |
681 | |
682 | return wb; |
683 | } |
684 | |
685 | static int cgwb_bdi_init(struct backing_dev_info *bdi) |
686 | { |
687 | int ret; |
688 | |
689 | INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC); |
690 | bdi->cgwb_congested_tree = RB_ROOT; |
691 | mutex_init(&bdi->cgwb_release_mutex); |
692 | init_rwsem(&bdi->wb_switch_rwsem); |
693 | |
694 | ret = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL); |
695 | if (!ret) { |
696 | bdi->wb.memcg_css = &root_mem_cgroup->css; |
697 | bdi->wb.blkcg_css = blkcg_root_css; |
698 | } |
699 | return ret; |
700 | } |
701 | |
702 | static void cgwb_bdi_unregister(struct backing_dev_info *bdi) |
703 | { |
704 | struct radix_tree_iter iter; |
705 | void **slot; |
706 | struct bdi_writeback *wb; |
707 | |
708 | WARN_ON(test_bit(WB_registered, &bdi->wb.state)); |
709 | |
710 | spin_lock_irq(&cgwb_lock); |
711 | radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0) |
712 | cgwb_kill(*slot); |
713 | spin_unlock_irq(&cgwb_lock); |
714 | |
715 | mutex_lock(&bdi->cgwb_release_mutex); |
716 | spin_lock_irq(&cgwb_lock); |
717 | while (!list_empty(&bdi->wb_list)) { |
718 | wb = list_first_entry(&bdi->wb_list, struct bdi_writeback, |
719 | bdi_node); |
720 | spin_unlock_irq(&cgwb_lock); |
721 | wb_shutdown(wb); |
722 | spin_lock_irq(&cgwb_lock); |
723 | } |
724 | spin_unlock_irq(&cgwb_lock); |
725 | mutex_unlock(&bdi->cgwb_release_mutex); |
726 | } |
727 | |
728 | /** |
729 | * wb_memcg_offline - kill all wb's associated with a memcg being offlined |
730 | * @memcg: memcg being offlined |
731 | * |
732 | * Also prevents creation of any new wb's associated with @memcg. |
733 | */ |
734 | void wb_memcg_offline(struct mem_cgroup *memcg) |
735 | { |
736 | struct list_head *memcg_cgwb_list = &memcg->cgwb_list; |
737 | struct bdi_writeback *wb, *next; |
738 | |
739 | spin_lock_irq(&cgwb_lock); |
740 | list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node) |
741 | cgwb_kill(wb); |
742 | memcg_cgwb_list->next = NULL; /* prevent new wb's */ |
743 | spin_unlock_irq(&cgwb_lock); |
744 | } |
745 | |
746 | /** |
747 | * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined |
748 | * @blkcg: blkcg being offlined |
749 | * |
750 | * Also prevents creation of any new wb's associated with @blkcg. |
751 | */ |
752 | void wb_blkcg_offline(struct blkcg *blkcg) |
753 | { |
754 | struct bdi_writeback *wb, *next; |
755 | |
756 | spin_lock_irq(&cgwb_lock); |
757 | list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node) |
758 | cgwb_kill(wb); |
759 | blkcg->cgwb_list.next = NULL; /* prevent new wb's */ |
760 | spin_unlock_irq(&cgwb_lock); |
761 | } |
762 | |
763 | static void cgwb_bdi_exit(struct backing_dev_info *bdi) |
764 | { |
765 | struct rb_node *rbn; |
766 | |
767 | spin_lock_irq(&cgwb_lock); |
768 | while ((rbn = rb_first(&bdi->cgwb_congested_tree))) { |
769 | struct bdi_writeback_congested *congested = |
770 | rb_entry(rbn, struct bdi_writeback_congested, rb_node); |
771 | |
772 | rb_erase(rbn, &bdi->cgwb_congested_tree); |
773 | congested->__bdi = NULL; /* mark @congested unlinked */ |
774 | } |
775 | spin_unlock_irq(&cgwb_lock); |
776 | } |
777 | |
778 | static void cgwb_bdi_register(struct backing_dev_info *bdi) |
779 | { |
780 | spin_lock_irq(&cgwb_lock); |
781 | list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list); |
782 | spin_unlock_irq(&cgwb_lock); |
783 | } |
784 | |
785 | static int __init cgwb_init(void) |
786 | { |
787 | /* |
788 | * There can be many concurrent release work items overwhelming |
789 | * system_wq. Put them in a separate wq and limit concurrency. |
790 | * There's no point in executing many of these in parallel. |
791 | */ |
792 | cgwb_release_wq = alloc_workqueue("cgwb_release" , 0, 1); |
793 | if (!cgwb_release_wq) |
794 | return -ENOMEM; |
795 | |
796 | return 0; |
797 | } |
798 | subsys_initcall(cgwb_init); |
799 | |
800 | #else /* CONFIG_CGROUP_WRITEBACK */ |
801 | |
802 | static int cgwb_bdi_init(struct backing_dev_info *bdi) |
803 | { |
804 | int err; |
805 | |
806 | bdi->wb_congested = kzalloc(sizeof(*bdi->wb_congested), GFP_KERNEL); |
807 | if (!bdi->wb_congested) |
808 | return -ENOMEM; |
809 | |
810 | refcount_set(&bdi->wb_congested->refcnt, 1); |
811 | |
812 | err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL); |
813 | if (err) { |
814 | wb_congested_put(bdi->wb_congested); |
815 | return err; |
816 | } |
817 | return 0; |
818 | } |
819 | |
820 | static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { } |
821 | |
822 | static void cgwb_bdi_exit(struct backing_dev_info *bdi) |
823 | { |
824 | wb_congested_put(bdi->wb_congested); |
825 | } |
826 | |
827 | static void cgwb_bdi_register(struct backing_dev_info *bdi) |
828 | { |
829 | list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list); |
830 | } |
831 | |
832 | static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb) |
833 | { |
834 | list_del_rcu(&wb->bdi_node); |
835 | } |
836 | |
837 | #endif /* CONFIG_CGROUP_WRITEBACK */ |
838 | |
839 | static int bdi_init(struct backing_dev_info *bdi) |
840 | { |
841 | int ret; |
842 | |
843 | bdi->dev = NULL; |
844 | |
845 | kref_init(&bdi->refcnt); |
846 | bdi->min_ratio = 0; |
847 | bdi->max_ratio = 100; |
848 | bdi->max_prop_frac = FPROP_FRAC_BASE; |
849 | INIT_LIST_HEAD(&bdi->bdi_list); |
850 | INIT_LIST_HEAD(&bdi->wb_list); |
851 | init_waitqueue_head(&bdi->wb_waitq); |
852 | |
853 | ret = cgwb_bdi_init(bdi); |
854 | |
855 | return ret; |
856 | } |
857 | |
858 | struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id) |
859 | { |
860 | struct backing_dev_info *bdi; |
861 | |
862 | bdi = kmalloc_node(sizeof(struct backing_dev_info), |
863 | gfp_mask | __GFP_ZERO, node_id); |
864 | if (!bdi) |
865 | return NULL; |
866 | |
867 | if (bdi_init(bdi)) { |
868 | kfree(bdi); |
869 | return NULL; |
870 | } |
871 | return bdi; |
872 | } |
873 | EXPORT_SYMBOL(bdi_alloc_node); |
874 | |
875 | int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args) |
876 | { |
877 | struct device *dev; |
878 | |
879 | if (bdi->dev) /* The driver needs to use separate queues per device */ |
880 | return 0; |
881 | |
882 | dev = device_create_vargs(bdi_class, NULL, MKDEV(0, 0), bdi, fmt, args); |
883 | if (IS_ERR(dev)) |
884 | return PTR_ERR(dev); |
885 | |
886 | cgwb_bdi_register(bdi); |
887 | bdi->dev = dev; |
888 | |
889 | bdi_debug_register(bdi, dev_name(dev)); |
890 | set_bit(WB_registered, &bdi->wb.state); |
891 | |
892 | spin_lock_bh(&bdi_lock); |
893 | list_add_tail_rcu(&bdi->bdi_list, &bdi_list); |
894 | spin_unlock_bh(&bdi_lock); |
895 | |
896 | trace_writeback_bdi_register(bdi); |
897 | return 0; |
898 | } |
899 | EXPORT_SYMBOL(bdi_register_va); |
900 | |
901 | int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...) |
902 | { |
903 | va_list args; |
904 | int ret; |
905 | |
906 | va_start(args, fmt); |
907 | ret = bdi_register_va(bdi, fmt, args); |
908 | va_end(args); |
909 | return ret; |
910 | } |
911 | EXPORT_SYMBOL(bdi_register); |
912 | |
913 | int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner) |
914 | { |
915 | int rc; |
916 | |
917 | rc = bdi_register(bdi, "%u:%u" , MAJOR(owner->devt), MINOR(owner->devt)); |
918 | if (rc) |
919 | return rc; |
920 | /* Leaking owner reference... */ |
921 | WARN_ON(bdi->owner); |
922 | bdi->owner = owner; |
923 | get_device(owner); |
924 | return 0; |
925 | } |
926 | EXPORT_SYMBOL(bdi_register_owner); |
927 | |
928 | /* |
929 | * Remove bdi from bdi_list, and ensure that it is no longer visible |
930 | */ |
931 | static void bdi_remove_from_list(struct backing_dev_info *bdi) |
932 | { |
933 | spin_lock_bh(&bdi_lock); |
934 | list_del_rcu(&bdi->bdi_list); |
935 | spin_unlock_bh(&bdi_lock); |
936 | |
937 | synchronize_rcu_expedited(); |
938 | } |
939 | |
940 | void bdi_unregister(struct backing_dev_info *bdi) |
941 | { |
942 | /* make sure nobody finds us on the bdi_list anymore */ |
943 | bdi_remove_from_list(bdi); |
944 | wb_shutdown(&bdi->wb); |
945 | cgwb_bdi_unregister(bdi); |
946 | |
947 | if (bdi->dev) { |
948 | bdi_debug_unregister(bdi); |
949 | device_unregister(bdi->dev); |
950 | bdi->dev = NULL; |
951 | } |
952 | |
953 | if (bdi->owner) { |
954 | put_device(bdi->owner); |
955 | bdi->owner = NULL; |
956 | } |
957 | } |
958 | |
959 | static void release_bdi(struct kref *ref) |
960 | { |
961 | struct backing_dev_info *bdi = |
962 | container_of(ref, struct backing_dev_info, refcnt); |
963 | |
964 | if (test_bit(WB_registered, &bdi->wb.state)) |
965 | bdi_unregister(bdi); |
966 | WARN_ON_ONCE(bdi->dev); |
967 | wb_exit(&bdi->wb); |
968 | cgwb_bdi_exit(bdi); |
969 | kfree(bdi); |
970 | } |
971 | |
972 | void bdi_put(struct backing_dev_info *bdi) |
973 | { |
974 | kref_put(&bdi->refcnt, release_bdi); |
975 | } |
976 | EXPORT_SYMBOL(bdi_put); |
977 | |
978 | static wait_queue_head_t congestion_wqh[2] = { |
979 | __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]), |
980 | __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1]) |
981 | }; |
982 | static atomic_t nr_wb_congested[2]; |
983 | |
984 | void clear_wb_congested(struct bdi_writeback_congested *congested, int sync) |
985 | { |
986 | wait_queue_head_t *wqh = &congestion_wqh[sync]; |
987 | enum wb_congested_state bit; |
988 | |
989 | bit = sync ? WB_sync_congested : WB_async_congested; |
990 | if (test_and_clear_bit(bit, &congested->state)) |
991 | atomic_dec(&nr_wb_congested[sync]); |
992 | smp_mb__after_atomic(); |
993 | if (waitqueue_active(wqh)) |
994 | wake_up(wqh); |
995 | } |
996 | EXPORT_SYMBOL(clear_wb_congested); |
997 | |
998 | void set_wb_congested(struct bdi_writeback_congested *congested, int sync) |
999 | { |
1000 | enum wb_congested_state bit; |
1001 | |
1002 | bit = sync ? WB_sync_congested : WB_async_congested; |
1003 | if (!test_and_set_bit(bit, &congested->state)) |
1004 | atomic_inc(&nr_wb_congested[sync]); |
1005 | } |
1006 | EXPORT_SYMBOL(set_wb_congested); |
1007 | |
1008 | /** |
1009 | * congestion_wait - wait for a backing_dev to become uncongested |
1010 | * @sync: SYNC or ASYNC IO |
1011 | * @timeout: timeout in jiffies |
1012 | * |
1013 | * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit |
1014 | * write congestion. If no backing_devs are congested then just wait for the |
1015 | * next write to be completed. |
1016 | */ |
1017 | long congestion_wait(int sync, long timeout) |
1018 | { |
1019 | long ret; |
1020 | unsigned long start = jiffies; |
1021 | DEFINE_WAIT(wait); |
1022 | wait_queue_head_t *wqh = &congestion_wqh[sync]; |
1023 | |
1024 | prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE); |
1025 | ret = io_schedule_timeout(timeout); |
1026 | finish_wait(wqh, &wait); |
1027 | |
1028 | trace_writeback_congestion_wait(jiffies_to_usecs(timeout), |
1029 | jiffies_to_usecs(jiffies - start)); |
1030 | |
1031 | return ret; |
1032 | } |
1033 | EXPORT_SYMBOL(congestion_wait); |
1034 | |
1035 | /** |
1036 | * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a pgdat to complete writes |
1037 | * @sync: SYNC or ASYNC IO |
1038 | * @timeout: timeout in jiffies |
1039 | * |
1040 | * In the event of a congested backing_dev (any backing_dev) this waits |
1041 | * for up to @timeout jiffies for either a BDI to exit congestion of the |
1042 | * given @sync queue or a write to complete. |
1043 | * |
1044 | * The return value is 0 if the sleep is for the full timeout. Otherwise, |
1045 | * it is the number of jiffies that were still remaining when the function |
1046 | * returned. return_value == timeout implies the function did not sleep. |
1047 | */ |
1048 | long wait_iff_congested(int sync, long timeout) |
1049 | { |
1050 | long ret; |
1051 | unsigned long start = jiffies; |
1052 | DEFINE_WAIT(wait); |
1053 | wait_queue_head_t *wqh = &congestion_wqh[sync]; |
1054 | |
1055 | /* |
1056 | * If there is no congestion, yield if necessary instead |
1057 | * of sleeping on the congestion queue |
1058 | */ |
1059 | if (atomic_read(&nr_wb_congested[sync]) == 0) { |
1060 | cond_resched(); |
1061 | |
1062 | /* In case we scheduled, work out time remaining */ |
1063 | ret = timeout - (jiffies - start); |
1064 | if (ret < 0) |
1065 | ret = 0; |
1066 | |
1067 | goto out; |
1068 | } |
1069 | |
1070 | /* Sleep until uncongested or a write happens */ |
1071 | prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE); |
1072 | ret = io_schedule_timeout(timeout); |
1073 | finish_wait(wqh, &wait); |
1074 | |
1075 | out: |
1076 | trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout), |
1077 | jiffies_to_usecs(jiffies - start)); |
1078 | |
1079 | return ret; |
1080 | } |
1081 | EXPORT_SYMBOL(wait_iff_congested); |
1082 | |