1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Common Block IO controller cgroup interface
4 *
5 * Based on ideas and code from CFQ, CFS and BFQ:
6 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
7 *
8 * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
9 * Paolo Valente <paolo.valente@unimore.it>
10 *
11 * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
12 * Nauman Rafique <nauman@google.com>
13 *
14 * For policy-specific per-blkcg data:
15 * Copyright (C) 2015 Paolo Valente <paolo.valente@unimore.it>
16 * Arianna Avanzini <avanzini.arianna@gmail.com>
17 */
18 #include <linux/ioprio.h>
19 #include <linux/kdev_t.h>
20 #include <linux/module.h>
21 #include <linux/sched/signal.h>
22 #include <linux/err.h>
23 #include <linux/blkdev.h>
24 #include <linux/backing-dev.h>
25 #include <linux/slab.h>
26 #include <linux/delay.h>
27 #include <linux/atomic.h>
28 #include <linux/ctype.h>
29 #include <linux/resume_user_mode.h>
30 #include <linux/psi.h>
31 #include <linux/part_stat.h>
32 #include "blk.h"
33 #include "blk-cgroup.h"
34 #include "blk-ioprio.h"
35 #include "blk-throttle.h"
36 #include "blk-rq-qos.h"
37
38 /*
39 * blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation.
40 * blkcg_pol_register_mutex nests outside of it and synchronizes entire
41 * policy [un]register operations including cgroup file additions /
42 * removals. Putting cgroup file registration outside blkcg_pol_mutex
43 * allows grabbing it from cgroup callbacks.
44 */
45 static DEFINE_MUTEX(blkcg_pol_register_mutex);
46 static DEFINE_MUTEX(blkcg_pol_mutex);
47
48 struct blkcg blkcg_root;
49 EXPORT_SYMBOL_GPL(blkcg_root);
50
51 struct cgroup_subsys_state * const blkcg_root_css = &blkcg_root.css;
52 EXPORT_SYMBOL_GPL(blkcg_root_css);
53
54 static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];
55
56 static LIST_HEAD(all_blkcgs); /* protected by blkcg_pol_mutex */
57
58 bool blkcg_debug_stats = false;
59 static struct workqueue_struct *blkcg_punt_bio_wq;
60
61 #define BLKG_DESTROY_BATCH_SIZE 64
62
63 /**
64 * blkcg_css - find the current css
65 *
66 * Find the css associated with either the kthread or the current task.
67 * This may return a dying css, so it is up to the caller to use tryget logic
68 * to confirm it is alive and well.
69 */
blkcg_css(void)70 static struct cgroup_subsys_state *blkcg_css(void)
71 {
72 struct cgroup_subsys_state *css;
73
74 css = kthread_blkcg();
75 if (css)
76 return css;
77 return task_css(current, io_cgrp_id);
78 }
79
blkcg_policy_enabled(struct request_queue * q,const struct blkcg_policy * pol)80 static bool blkcg_policy_enabled(struct request_queue *q,
81 const struct blkcg_policy *pol)
82 {
83 return pol && test_bit(pol->plid, q->blkcg_pols);
84 }
85
blkg_free_workfn(struct work_struct * work)86 static void blkg_free_workfn(struct work_struct *work)
87 {
88 struct blkcg_gq *blkg = container_of(work, struct blkcg_gq,
89 free_work);
90 int i;
91
92 for (i = 0; i < BLKCG_MAX_POLS; i++)
93 if (blkg->pd[i])
94 blkcg_policy[i]->pd_free_fn(blkg->pd[i]);
95
96 if (blkg->q)
97 blk_put_queue(blkg->q);
98 free_percpu(blkg->iostat_cpu);
99 percpu_ref_exit(&blkg->refcnt);
100 kfree(blkg);
101 }
102
103 /**
104 * blkg_free - free a blkg
105 * @blkg: blkg to free
106 *
107 * Free @blkg which may be partially allocated.
108 */
blkg_free(struct blkcg_gq * blkg)109 static void blkg_free(struct blkcg_gq *blkg)
110 {
111 if (!blkg)
112 return;
113
114 /*
115 * Both ->pd_free_fn() and request queue's release handler may
116 * sleep, so free us by scheduling one work func
117 */
118 INIT_WORK(&blkg->free_work, blkg_free_workfn);
119 schedule_work(&blkg->free_work);
120 }
121
__blkg_release(struct rcu_head * rcu)122 static void __blkg_release(struct rcu_head *rcu)
123 {
124 struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head);
125
126 WARN_ON(!bio_list_empty(&blkg->async_bios));
127
128 /* release the blkcg and parent blkg refs this blkg has been holding */
129 css_put(&blkg->blkcg->css);
130 if (blkg->parent)
131 blkg_put(blkg->parent);
132 blkg_free(blkg);
133 }
134
135 /*
136 * A group is RCU protected, but having an rcu lock does not mean that one
137 * can access all the fields of blkg and assume these are valid. For
138 * example, don't try to follow throtl_data and request queue links.
139 *
140 * Having a reference to blkg under an rcu allows accesses to only values
141 * local to groups like group stats and group rate limits.
142 */
blkg_release(struct percpu_ref * ref)143 static void blkg_release(struct percpu_ref *ref)
144 {
145 struct blkcg_gq *blkg = container_of(ref, struct blkcg_gq, refcnt);
146
147 call_rcu(&blkg->rcu_head, __blkg_release);
148 }
149
blkg_async_bio_workfn(struct work_struct * work)150 static void blkg_async_bio_workfn(struct work_struct *work)
151 {
152 struct blkcg_gq *blkg = container_of(work, struct blkcg_gq,
153 async_bio_work);
154 struct bio_list bios = BIO_EMPTY_LIST;
155 struct bio *bio;
156 struct blk_plug plug;
157 bool need_plug = false;
158
159 /* as long as there are pending bios, @blkg can't go away */
160 spin_lock_bh(&blkg->async_bio_lock);
161 bio_list_merge(&bios, &blkg->async_bios);
162 bio_list_init(&blkg->async_bios);
163 spin_unlock_bh(&blkg->async_bio_lock);
164
165 /* start plug only when bio_list contains at least 2 bios */
166 if (bios.head && bios.head->bi_next) {
167 need_plug = true;
168 blk_start_plug(&plug);
169 }
170 while ((bio = bio_list_pop(&bios)))
171 submit_bio(bio);
172 if (need_plug)
173 blk_finish_plug(&plug);
174 }
175
176 /**
177 * bio_blkcg_css - return the blkcg CSS associated with a bio
178 * @bio: target bio
179 *
180 * This returns the CSS for the blkcg associated with a bio, or %NULL if not
181 * associated. Callers are expected to either handle %NULL or know association
182 * has been done prior to calling this.
183 */
bio_blkcg_css(struct bio * bio)184 struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio)
185 {
186 if (!bio || !bio->bi_blkg)
187 return NULL;
188 return &bio->bi_blkg->blkcg->css;
189 }
190 EXPORT_SYMBOL_GPL(bio_blkcg_css);
191
192 /**
193 * blkcg_parent - get the parent of a blkcg
194 * @blkcg: blkcg of interest
195 *
196 * Return the parent blkcg of @blkcg. Can be called anytime.
197 */
blkcg_parent(struct blkcg * blkcg)198 static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
199 {
200 return css_to_blkcg(blkcg->css.parent);
201 }
202
203 /**
204 * blkg_alloc - allocate a blkg
205 * @blkcg: block cgroup the new blkg is associated with
206 * @disk: gendisk the new blkg is associated with
207 * @gfp_mask: allocation mask to use
208 *
209 * Allocate a new blkg assocating @blkcg and @q.
210 */
blkg_alloc(struct blkcg * blkcg,struct gendisk * disk,gfp_t gfp_mask)211 static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct gendisk *disk,
212 gfp_t gfp_mask)
213 {
214 struct blkcg_gq *blkg;
215 int i, cpu;
216
217 /* alloc and init base part */
218 blkg = kzalloc_node(sizeof(*blkg), gfp_mask, disk->queue->node);
219 if (!blkg)
220 return NULL;
221
222 if (percpu_ref_init(&blkg->refcnt, blkg_release, 0, gfp_mask))
223 goto err_free;
224
225 blkg->iostat_cpu = alloc_percpu_gfp(struct blkg_iostat_set, gfp_mask);
226 if (!blkg->iostat_cpu)
227 goto err_free;
228
229 if (!blk_get_queue(disk->queue))
230 goto err_free;
231
232 blkg->q = disk->queue;
233 INIT_LIST_HEAD(&blkg->q_node);
234 spin_lock_init(&blkg->async_bio_lock);
235 bio_list_init(&blkg->async_bios);
236 INIT_WORK(&blkg->async_bio_work, blkg_async_bio_workfn);
237 blkg->blkcg = blkcg;
238
239 u64_stats_init(&blkg->iostat.sync);
240 for_each_possible_cpu(cpu)
241 u64_stats_init(&per_cpu_ptr(blkg->iostat_cpu, cpu)->sync);
242
243 for (i = 0; i < BLKCG_MAX_POLS; i++) {
244 struct blkcg_policy *pol = blkcg_policy[i];
245 struct blkg_policy_data *pd;
246
247 if (!blkcg_policy_enabled(disk->queue, pol))
248 continue;
249
250 /* alloc per-policy data and attach it to blkg */
251 pd = pol->pd_alloc_fn(gfp_mask, disk->queue, blkcg);
252 if (!pd)
253 goto err_free;
254
255 blkg->pd[i] = pd;
256 pd->blkg = blkg;
257 pd->plid = i;
258 }
259
260 return blkg;
261
262 err_free:
263 blkg_free(blkg);
264 return NULL;
265 }
266
267 /*
268 * If @new_blkg is %NULL, this function tries to allocate a new one as
269 * necessary using %GFP_NOWAIT. @new_blkg is always consumed on return.
270 */
blkg_create(struct blkcg * blkcg,struct gendisk * disk,struct blkcg_gq * new_blkg)271 static struct blkcg_gq *blkg_create(struct blkcg *blkcg, struct gendisk *disk,
272 struct blkcg_gq *new_blkg)
273 {
274 struct blkcg_gq *blkg;
275 int i, ret;
276
277 lockdep_assert_held(&disk->queue->queue_lock);
278
279 /* request_queue is dying, do not create/recreate a blkg */
280 if (blk_queue_dying(disk->queue)) {
281 ret = -ENODEV;
282 goto err_free_blkg;
283 }
284
285 /* blkg holds a reference to blkcg */
286 if (!css_tryget_online(&blkcg->css)) {
287 ret = -ENODEV;
288 goto err_free_blkg;
289 }
290
291 /* allocate */
292 if (!new_blkg) {
293 new_blkg = blkg_alloc(blkcg, disk, GFP_NOWAIT | __GFP_NOWARN);
294 if (unlikely(!new_blkg)) {
295 ret = -ENOMEM;
296 goto err_put_css;
297 }
298 }
299 blkg = new_blkg;
300
301 /* link parent */
302 if (blkcg_parent(blkcg)) {
303 blkg->parent = blkg_lookup(blkcg_parent(blkcg), disk->queue);
304 if (WARN_ON_ONCE(!blkg->parent)) {
305 ret = -ENODEV;
306 goto err_put_css;
307 }
308 blkg_get(blkg->parent);
309 }
310
311 /* invoke per-policy init */
312 for (i = 0; i < BLKCG_MAX_POLS; i++) {
313 struct blkcg_policy *pol = blkcg_policy[i];
314
315 if (blkg->pd[i] && pol->pd_init_fn)
316 pol->pd_init_fn(blkg->pd[i]);
317 }
318
319 /* insert */
320 spin_lock(&blkcg->lock);
321 ret = radix_tree_insert(&blkcg->blkg_tree, disk->queue->id, blkg);
322 if (likely(!ret)) {
323 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
324 list_add(&blkg->q_node, &disk->queue->blkg_list);
325
326 for (i = 0; i < BLKCG_MAX_POLS; i++) {
327 struct blkcg_policy *pol = blkcg_policy[i];
328
329 if (blkg->pd[i] && pol->pd_online_fn)
330 pol->pd_online_fn(blkg->pd[i]);
331 }
332 }
333 blkg->online = true;
334 spin_unlock(&blkcg->lock);
335
336 if (!ret)
337 return blkg;
338
339 /* @blkg failed fully initialized, use the usual release path */
340 blkg_put(blkg);
341 return ERR_PTR(ret);
342
343 err_put_css:
344 css_put(&blkcg->css);
345 err_free_blkg:
346 blkg_free(new_blkg);
347 return ERR_PTR(ret);
348 }
349
350 /**
351 * blkg_lookup_create - lookup blkg, try to create one if not there
352 * @blkcg: blkcg of interest
353 * @disk: gendisk of interest
354 *
355 * Lookup blkg for the @blkcg - @disk pair. If it doesn't exist, try to
356 * create one. blkg creation is performed recursively from blkcg_root such
357 * that all non-root blkg's have access to the parent blkg. This function
358 * should be called under RCU read lock and takes @disk->queue->queue_lock.
359 *
360 * Returns the blkg or the closest blkg if blkg_create() fails as it walks
361 * down from root.
362 */
blkg_lookup_create(struct blkcg * blkcg,struct gendisk * disk)363 static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
364 struct gendisk *disk)
365 {
366 struct request_queue *q = disk->queue;
367 struct blkcg_gq *blkg;
368 unsigned long flags;
369
370 WARN_ON_ONCE(!rcu_read_lock_held());
371
372 blkg = blkg_lookup(blkcg, q);
373 if (blkg)
374 return blkg;
375
376 spin_lock_irqsave(&q->queue_lock, flags);
377 blkg = blkg_lookup(blkcg, q);
378 if (blkg) {
379 if (blkcg != &blkcg_root &&
380 blkg != rcu_dereference(blkcg->blkg_hint))
381 rcu_assign_pointer(blkcg->blkg_hint, blkg);
382 goto found;
383 }
384
385 /*
386 * Create blkgs walking down from blkcg_root to @blkcg, so that all
387 * non-root blkgs have access to their parents. Returns the closest
388 * blkg to the intended blkg should blkg_create() fail.
389 */
390 while (true) {
391 struct blkcg *pos = blkcg;
392 struct blkcg *parent = blkcg_parent(blkcg);
393 struct blkcg_gq *ret_blkg = q->root_blkg;
394
395 while (parent) {
396 blkg = blkg_lookup(parent, q);
397 if (blkg) {
398 /* remember closest blkg */
399 ret_blkg = blkg;
400 break;
401 }
402 pos = parent;
403 parent = blkcg_parent(parent);
404 }
405
406 blkg = blkg_create(pos, disk, NULL);
407 if (IS_ERR(blkg)) {
408 blkg = ret_blkg;
409 break;
410 }
411 if (pos == blkcg)
412 break;
413 }
414
415 found:
416 spin_unlock_irqrestore(&q->queue_lock, flags);
417 return blkg;
418 }
419
blkg_destroy(struct blkcg_gq * blkg)420 static void blkg_destroy(struct blkcg_gq *blkg)
421 {
422 struct blkcg *blkcg = blkg->blkcg;
423 int i;
424
425 lockdep_assert_held(&blkg->q->queue_lock);
426 lockdep_assert_held(&blkcg->lock);
427
428 /* Something wrong if we are trying to remove same group twice */
429 WARN_ON_ONCE(list_empty(&blkg->q_node));
430 WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
431
432 for (i = 0; i < BLKCG_MAX_POLS; i++) {
433 struct blkcg_policy *pol = blkcg_policy[i];
434
435 if (blkg->pd[i] && pol->pd_offline_fn)
436 pol->pd_offline_fn(blkg->pd[i]);
437 }
438
439 blkg->online = false;
440
441 radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
442 list_del_init(&blkg->q_node);
443 hlist_del_init_rcu(&blkg->blkcg_node);
444
445 /*
446 * Both setting lookup hint to and clearing it from @blkg are done
447 * under queue_lock. If it's not pointing to @blkg now, it never
448 * will. Hint assignment itself can race safely.
449 */
450 if (rcu_access_pointer(blkcg->blkg_hint) == blkg)
451 rcu_assign_pointer(blkcg->blkg_hint, NULL);
452
453 /*
454 * Put the reference taken at the time of creation so that when all
455 * queues are gone, group can be destroyed.
456 */
457 percpu_ref_kill(&blkg->refcnt);
458 }
459
blkg_destroy_all(struct gendisk * disk)460 static void blkg_destroy_all(struct gendisk *disk)
461 {
462 struct request_queue *q = disk->queue;
463 struct blkcg_gq *blkg, *n;
464 int count = BLKG_DESTROY_BATCH_SIZE;
465
466 restart:
467 spin_lock_irq(&q->queue_lock);
468 list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
469 struct blkcg *blkcg = blkg->blkcg;
470
471 spin_lock(&blkcg->lock);
472 blkg_destroy(blkg);
473 spin_unlock(&blkcg->lock);
474
475 /*
476 * in order to avoid holding the spin lock for too long, release
477 * it when a batch of blkgs are destroyed.
478 */
479 if (!(--count)) {
480 count = BLKG_DESTROY_BATCH_SIZE;
481 spin_unlock_irq(&q->queue_lock);
482 cond_resched();
483 goto restart;
484 }
485 }
486
487 q->root_blkg = NULL;
488 spin_unlock_irq(&q->queue_lock);
489 }
490
blkcg_reset_stats(struct cgroup_subsys_state * css,struct cftype * cftype,u64 val)491 static int blkcg_reset_stats(struct cgroup_subsys_state *css,
492 struct cftype *cftype, u64 val)
493 {
494 struct blkcg *blkcg = css_to_blkcg(css);
495 struct blkcg_gq *blkg;
496 int i, cpu;
497
498 mutex_lock(&blkcg_pol_mutex);
499 spin_lock_irq(&blkcg->lock);
500
501 /*
502 * Note that stat reset is racy - it doesn't synchronize against
503 * stat updates. This is a debug feature which shouldn't exist
504 * anyway. If you get hit by a race, retry.
505 */
506 hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
507 for_each_possible_cpu(cpu) {
508 struct blkg_iostat_set *bis =
509 per_cpu_ptr(blkg->iostat_cpu, cpu);
510 memset(bis, 0, sizeof(*bis));
511 }
512 memset(&blkg->iostat, 0, sizeof(blkg->iostat));
513
514 for (i = 0; i < BLKCG_MAX_POLS; i++) {
515 struct blkcg_policy *pol = blkcg_policy[i];
516
517 if (blkg->pd[i] && pol->pd_reset_stats_fn)
518 pol->pd_reset_stats_fn(blkg->pd[i]);
519 }
520 }
521
522 spin_unlock_irq(&blkcg->lock);
523 mutex_unlock(&blkcg_pol_mutex);
524 return 0;
525 }
526
blkg_dev_name(struct blkcg_gq * blkg)527 const char *blkg_dev_name(struct blkcg_gq *blkg)
528 {
529 if (!blkg->q->disk || !blkg->q->disk->bdi->dev)
530 return NULL;
531 return bdi_dev_name(blkg->q->disk->bdi);
532 }
533
534 /**
535 * blkcg_print_blkgs - helper for printing per-blkg data
536 * @sf: seq_file to print to
537 * @blkcg: blkcg of interest
538 * @prfill: fill function to print out a blkg
539 * @pol: policy in question
540 * @data: data to be passed to @prfill
541 * @show_total: to print out sum of prfill return values or not
542 *
543 * This function invokes @prfill on each blkg of @blkcg if pd for the
544 * policy specified by @pol exists. @prfill is invoked with @sf, the
545 * policy data and @data and the matching queue lock held. If @show_total
546 * is %true, the sum of the return values from @prfill is printed with
547 * "Total" label at the end.
548 *
549 * This is to be used to construct print functions for
550 * cftype->read_seq_string method.
551 */
blkcg_print_blkgs(struct seq_file * sf,struct blkcg * blkcg,u64 (* prfill)(struct seq_file *,struct blkg_policy_data *,int),const struct blkcg_policy * pol,int data,bool show_total)552 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
553 u64 (*prfill)(struct seq_file *,
554 struct blkg_policy_data *, int),
555 const struct blkcg_policy *pol, int data,
556 bool show_total)
557 {
558 struct blkcg_gq *blkg;
559 u64 total = 0;
560
561 rcu_read_lock();
562 hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
563 spin_lock_irq(&blkg->q->queue_lock);
564 if (blkcg_policy_enabled(blkg->q, pol))
565 total += prfill(sf, blkg->pd[pol->plid], data);
566 spin_unlock_irq(&blkg->q->queue_lock);
567 }
568 rcu_read_unlock();
569
570 if (show_total)
571 seq_printf(sf, "Total %llu\n", (unsigned long long)total);
572 }
573 EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
574
575 /**
576 * __blkg_prfill_u64 - prfill helper for a single u64 value
577 * @sf: seq_file to print to
578 * @pd: policy private data of interest
579 * @v: value to print
580 *
581 * Print @v to @sf for the device assocaited with @pd.
582 */
__blkg_prfill_u64(struct seq_file * sf,struct blkg_policy_data * pd,u64 v)583 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
584 {
585 const char *dname = blkg_dev_name(pd->blkg);
586
587 if (!dname)
588 return 0;
589
590 seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
591 return v;
592 }
593 EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
594
595 /**
596 * blkcg_conf_open_bdev - parse and open bdev for per-blkg config update
597 * @inputp: input string pointer
598 *
599 * Parse the device node prefix part, MAJ:MIN, of per-blkg config update
600 * from @input and get and return the matching bdev. *@inputp is
601 * updated to point past the device node prefix. Returns an ERR_PTR()
602 * value on error.
603 *
604 * Use this function iff blkg_conf_prep() can't be used for some reason.
605 */
blkcg_conf_open_bdev(char ** inputp)606 struct block_device *blkcg_conf_open_bdev(char **inputp)
607 {
608 char *input = *inputp;
609 unsigned int major, minor;
610 struct block_device *bdev;
611 int key_len;
612
613 if (sscanf(input, "%u:%u%n", &major, &minor, &key_len) != 2)
614 return ERR_PTR(-EINVAL);
615
616 input += key_len;
617 if (!isspace(*input))
618 return ERR_PTR(-EINVAL);
619 input = skip_spaces(input);
620
621 bdev = blkdev_get_no_open(MKDEV(major, minor));
622 if (!bdev)
623 return ERR_PTR(-ENODEV);
624 if (bdev_is_partition(bdev)) {
625 blkdev_put_no_open(bdev);
626 return ERR_PTR(-ENODEV);
627 }
628
629 *inputp = input;
630 return bdev;
631 }
632
633 /**
634 * blkg_conf_prep - parse and prepare for per-blkg config update
635 * @blkcg: target block cgroup
636 * @pol: target policy
637 * @input: input string
638 * @ctx: blkg_conf_ctx to be filled
639 *
640 * Parse per-blkg config update from @input and initialize @ctx with the
641 * result. @ctx->blkg points to the blkg to be updated and @ctx->body the
642 * part of @input following MAJ:MIN. This function returns with RCU read
643 * lock and queue lock held and must be paired with blkg_conf_finish().
644 */
blkg_conf_prep(struct blkcg * blkcg,const struct blkcg_policy * pol,char * input,struct blkg_conf_ctx * ctx)645 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
646 char *input, struct blkg_conf_ctx *ctx)
647 __acquires(rcu) __acquires(&bdev->bd_queue->queue_lock)
648 {
649 struct block_device *bdev;
650 struct gendisk *disk;
651 struct request_queue *q;
652 struct blkcg_gq *blkg;
653 int ret;
654
655 bdev = blkcg_conf_open_bdev(&input);
656 if (IS_ERR(bdev))
657 return PTR_ERR(bdev);
658 disk = bdev->bd_disk;
659 q = disk->queue;
660
661 /*
662 * blkcg_deactivate_policy() requires queue to be frozen, we can grab
663 * q_usage_counter to prevent concurrent with blkcg_deactivate_policy().
664 */
665 ret = blk_queue_enter(q, 0);
666 if (ret)
667 goto fail;
668
669 rcu_read_lock();
670 spin_lock_irq(&q->queue_lock);
671
672 if (!blkcg_policy_enabled(q, pol)) {
673 ret = -EOPNOTSUPP;
674 goto fail_unlock;
675 }
676
677 blkg = blkg_lookup(blkcg, q);
678 if (blkg)
679 goto success;
680
681 /*
682 * Create blkgs walking down from blkcg_root to @blkcg, so that all
683 * non-root blkgs have access to their parents.
684 */
685 while (true) {
686 struct blkcg *pos = blkcg;
687 struct blkcg *parent;
688 struct blkcg_gq *new_blkg;
689
690 parent = blkcg_parent(blkcg);
691 while (parent && !blkg_lookup(parent, q)) {
692 pos = parent;
693 parent = blkcg_parent(parent);
694 }
695
696 /* Drop locks to do new blkg allocation with GFP_KERNEL. */
697 spin_unlock_irq(&q->queue_lock);
698 rcu_read_unlock();
699
700 new_blkg = blkg_alloc(pos, disk, GFP_KERNEL);
701 if (unlikely(!new_blkg)) {
702 ret = -ENOMEM;
703 goto fail_exit_queue;
704 }
705
706 if (radix_tree_preload(GFP_KERNEL)) {
707 blkg_free(new_blkg);
708 ret = -ENOMEM;
709 goto fail_exit_queue;
710 }
711
712 rcu_read_lock();
713 spin_lock_irq(&q->queue_lock);
714
715 if (!blkcg_policy_enabled(q, pol)) {
716 blkg_free(new_blkg);
717 ret = -EOPNOTSUPP;
718 goto fail_preloaded;
719 }
720
721 blkg = blkg_lookup(pos, q);
722 if (blkg) {
723 blkg_free(new_blkg);
724 } else {
725 blkg = blkg_create(pos, disk, new_blkg);
726 if (IS_ERR(blkg)) {
727 ret = PTR_ERR(blkg);
728 goto fail_preloaded;
729 }
730 }
731
732 radix_tree_preload_end();
733
734 if (pos == blkcg)
735 goto success;
736 }
737 success:
738 blk_queue_exit(q);
739 ctx->bdev = bdev;
740 ctx->blkg = blkg;
741 ctx->body = input;
742 return 0;
743
744 fail_preloaded:
745 radix_tree_preload_end();
746 fail_unlock:
747 spin_unlock_irq(&q->queue_lock);
748 rcu_read_unlock();
749 fail_exit_queue:
750 blk_queue_exit(q);
751 fail:
752 blkdev_put_no_open(bdev);
753 /*
754 * If queue was bypassing, we should retry. Do so after a
755 * short msleep(). It isn't strictly necessary but queue
756 * can be bypassing for some time and it's always nice to
757 * avoid busy looping.
758 */
759 if (ret == -EBUSY) {
760 msleep(10);
761 ret = restart_syscall();
762 }
763 return ret;
764 }
765 EXPORT_SYMBOL_GPL(blkg_conf_prep);
766
767 /**
768 * blkg_conf_finish - finish up per-blkg config update
769 * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
770 *
771 * Finish up after per-blkg config update. This function must be paired
772 * with blkg_conf_prep().
773 */
blkg_conf_finish(struct blkg_conf_ctx * ctx)774 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
775 __releases(&ctx->bdev->bd_queue->queue_lock) __releases(rcu)
776 {
777 spin_unlock_irq(&bdev_get_queue(ctx->bdev)->queue_lock);
778 rcu_read_unlock();
779 blkdev_put_no_open(ctx->bdev);
780 }
781 EXPORT_SYMBOL_GPL(blkg_conf_finish);
782
blkg_iostat_set(struct blkg_iostat * dst,struct blkg_iostat * src)783 static void blkg_iostat_set(struct blkg_iostat *dst, struct blkg_iostat *src)
784 {
785 int i;
786
787 for (i = 0; i < BLKG_IOSTAT_NR; i++) {
788 dst->bytes[i] = src->bytes[i];
789 dst->ios[i] = src->ios[i];
790 }
791 }
792
blkg_iostat_add(struct blkg_iostat * dst,struct blkg_iostat * src)793 static void blkg_iostat_add(struct blkg_iostat *dst, struct blkg_iostat *src)
794 {
795 int i;
796
797 for (i = 0; i < BLKG_IOSTAT_NR; i++) {
798 dst->bytes[i] += src->bytes[i];
799 dst->ios[i] += src->ios[i];
800 }
801 }
802
blkg_iostat_sub(struct blkg_iostat * dst,struct blkg_iostat * src)803 static void blkg_iostat_sub(struct blkg_iostat *dst, struct blkg_iostat *src)
804 {
805 int i;
806
807 for (i = 0; i < BLKG_IOSTAT_NR; i++) {
808 dst->bytes[i] -= src->bytes[i];
809 dst->ios[i] -= src->ios[i];
810 }
811 }
812
blkcg_iostat_update(struct blkcg_gq * blkg,struct blkg_iostat * cur,struct blkg_iostat * last)813 static void blkcg_iostat_update(struct blkcg_gq *blkg, struct blkg_iostat *cur,
814 struct blkg_iostat *last)
815 {
816 struct blkg_iostat delta;
817 unsigned long flags;
818
819 /* propagate percpu delta to global */
820 flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync);
821 blkg_iostat_set(&delta, cur);
822 blkg_iostat_sub(&delta, last);
823 blkg_iostat_add(&blkg->iostat.cur, &delta);
824 blkg_iostat_add(last, &delta);
825 u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags);
826 }
827
blkcg_rstat_flush(struct cgroup_subsys_state * css,int cpu)828 static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu)
829 {
830 struct blkcg *blkcg = css_to_blkcg(css);
831 struct blkcg_gq *blkg;
832
833 /* Root-level stats are sourced from system-wide IO stats */
834 if (!cgroup_parent(css->cgroup))
835 return;
836
837 rcu_read_lock();
838
839 hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
840 struct blkcg_gq *parent = blkg->parent;
841 struct blkg_iostat_set *bisc = per_cpu_ptr(blkg->iostat_cpu, cpu);
842 struct blkg_iostat cur;
843 unsigned int seq;
844
845 /* fetch the current per-cpu values */
846 do {
847 seq = u64_stats_fetch_begin(&bisc->sync);
848 blkg_iostat_set(&cur, &bisc->cur);
849 } while (u64_stats_fetch_retry(&bisc->sync, seq));
850
851 blkcg_iostat_update(blkg, &cur, &bisc->last);
852
853 /* propagate global delta to parent (unless that's root) */
854 if (parent && parent->parent)
855 blkcg_iostat_update(parent, &blkg->iostat.cur,
856 &blkg->iostat.last);
857 }
858
859 rcu_read_unlock();
860 }
861
862 /*
863 * We source root cgroup stats from the system-wide stats to avoid
864 * tracking the same information twice and incurring overhead when no
865 * cgroups are defined. For that reason, cgroup_rstat_flush in
866 * blkcg_print_stat does not actually fill out the iostat in the root
867 * cgroup's blkcg_gq.
868 *
869 * However, we would like to re-use the printing code between the root and
870 * non-root cgroups to the extent possible. For that reason, we simulate
871 * flushing the root cgroup's stats by explicitly filling in the iostat
872 * with disk level statistics.
873 */
blkcg_fill_root_iostats(void)874 static void blkcg_fill_root_iostats(void)
875 {
876 struct class_dev_iter iter;
877 struct device *dev;
878
879 class_dev_iter_init(&iter, &block_class, NULL, &disk_type);
880 while ((dev = class_dev_iter_next(&iter))) {
881 struct block_device *bdev = dev_to_bdev(dev);
882 struct blkcg_gq *blkg = bdev->bd_disk->queue->root_blkg;
883 struct blkg_iostat tmp;
884 int cpu;
885 unsigned long flags;
886
887 memset(&tmp, 0, sizeof(tmp));
888 for_each_possible_cpu(cpu) {
889 struct disk_stats *cpu_dkstats;
890
891 cpu_dkstats = per_cpu_ptr(bdev->bd_stats, cpu);
892 tmp.ios[BLKG_IOSTAT_READ] +=
893 cpu_dkstats->ios[STAT_READ];
894 tmp.ios[BLKG_IOSTAT_WRITE] +=
895 cpu_dkstats->ios[STAT_WRITE];
896 tmp.ios[BLKG_IOSTAT_DISCARD] +=
897 cpu_dkstats->ios[STAT_DISCARD];
898 // convert sectors to bytes
899 tmp.bytes[BLKG_IOSTAT_READ] +=
900 cpu_dkstats->sectors[STAT_READ] << 9;
901 tmp.bytes[BLKG_IOSTAT_WRITE] +=
902 cpu_dkstats->sectors[STAT_WRITE] << 9;
903 tmp.bytes[BLKG_IOSTAT_DISCARD] +=
904 cpu_dkstats->sectors[STAT_DISCARD] << 9;
905 }
906
907 flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync);
908 blkg_iostat_set(&blkg->iostat.cur, &tmp);
909 u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags);
910 }
911 }
912
blkcg_print_one_stat(struct blkcg_gq * blkg,struct seq_file * s)913 static void blkcg_print_one_stat(struct blkcg_gq *blkg, struct seq_file *s)
914 {
915 struct blkg_iostat_set *bis = &blkg->iostat;
916 u64 rbytes, wbytes, rios, wios, dbytes, dios;
917 const char *dname;
918 unsigned seq;
919 int i;
920
921 if (!blkg->online)
922 return;
923
924 dname = blkg_dev_name(blkg);
925 if (!dname)
926 return;
927
928 seq_printf(s, "%s ", dname);
929
930 do {
931 seq = u64_stats_fetch_begin(&bis->sync);
932
933 rbytes = bis->cur.bytes[BLKG_IOSTAT_READ];
934 wbytes = bis->cur.bytes[BLKG_IOSTAT_WRITE];
935 dbytes = bis->cur.bytes[BLKG_IOSTAT_DISCARD];
936 rios = bis->cur.ios[BLKG_IOSTAT_READ];
937 wios = bis->cur.ios[BLKG_IOSTAT_WRITE];
938 dios = bis->cur.ios[BLKG_IOSTAT_DISCARD];
939 } while (u64_stats_fetch_retry(&bis->sync, seq));
940
941 if (rbytes || wbytes || rios || wios) {
942 seq_printf(s, "rbytes=%llu wbytes=%llu rios=%llu wios=%llu dbytes=%llu dios=%llu",
943 rbytes, wbytes, rios, wios,
944 dbytes, dios);
945 }
946
947 if (blkcg_debug_stats && atomic_read(&blkg->use_delay)) {
948 seq_printf(s, " use_delay=%d delay_nsec=%llu",
949 atomic_read(&blkg->use_delay),
950 atomic64_read(&blkg->delay_nsec));
951 }
952
953 for (i = 0; i < BLKCG_MAX_POLS; i++) {
954 struct blkcg_policy *pol = blkcg_policy[i];
955
956 if (!blkg->pd[i] || !pol->pd_stat_fn)
957 continue;
958
959 pol->pd_stat_fn(blkg->pd[i], s);
960 }
961
962 seq_puts(s, "\n");
963 }
964
blkcg_print_stat(struct seq_file * sf,void * v)965 static int blkcg_print_stat(struct seq_file *sf, void *v)
966 {
967 struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
968 struct blkcg_gq *blkg;
969
970 if (!seq_css(sf)->parent)
971 blkcg_fill_root_iostats();
972 else
973 cgroup_rstat_flush(blkcg->css.cgroup);
974
975 rcu_read_lock();
976 hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
977 spin_lock_irq(&blkg->q->queue_lock);
978 blkcg_print_one_stat(blkg, sf);
979 spin_unlock_irq(&blkg->q->queue_lock);
980 }
981 rcu_read_unlock();
982 return 0;
983 }
984
985 static struct cftype blkcg_files[] = {
986 {
987 .name = "stat",
988 .seq_show = blkcg_print_stat,
989 },
990 { } /* terminate */
991 };
992
993 static struct cftype blkcg_legacy_files[] = {
994 {
995 .name = "reset_stats",
996 .write_u64 = blkcg_reset_stats,
997 },
998 { } /* terminate */
999 };
1000
1001 #ifdef CONFIG_CGROUP_WRITEBACK
blkcg_get_cgwb_list(struct cgroup_subsys_state * css)1002 struct list_head *blkcg_get_cgwb_list(struct cgroup_subsys_state *css)
1003 {
1004 return &css_to_blkcg(css)->cgwb_list;
1005 }
1006 #endif
1007
1008 /*
1009 * blkcg destruction is a three-stage process.
1010 *
1011 * 1. Destruction starts. The blkcg_css_offline() callback is invoked
1012 * which offlines writeback. Here we tie the next stage of blkg destruction
1013 * to the completion of writeback associated with the blkcg. This lets us
1014 * avoid punting potentially large amounts of outstanding writeback to root
1015 * while maintaining any ongoing policies. The next stage is triggered when
1016 * the nr_cgwbs count goes to zero.
1017 *
1018 * 2. When the nr_cgwbs count goes to zero, blkcg_destroy_blkgs() is called
1019 * and handles the destruction of blkgs. Here the css reference held by
1020 * the blkg is put back eventually allowing blkcg_css_free() to be called.
1021 * This work may occur in cgwb_release_workfn() on the cgwb_release
1022 * workqueue. Any submitted ios that fail to get the blkg ref will be
1023 * punted to the root_blkg.
1024 *
1025 * 3. Once the blkcg ref count goes to zero, blkcg_css_free() is called.
1026 * This finally frees the blkcg.
1027 */
1028
1029 /**
1030 * blkcg_destroy_blkgs - responsible for shooting down blkgs
1031 * @blkcg: blkcg of interest
1032 *
1033 * blkgs should be removed while holding both q and blkcg locks. As blkcg lock
1034 * is nested inside q lock, this function performs reverse double lock dancing.
1035 * Destroying the blkgs releases the reference held on the blkcg's css allowing
1036 * blkcg_css_free to eventually be called.
1037 *
1038 * This is the blkcg counterpart of ioc_release_fn().
1039 */
blkcg_destroy_blkgs(struct blkcg * blkcg)1040 static void blkcg_destroy_blkgs(struct blkcg *blkcg)
1041 {
1042 might_sleep();
1043
1044 spin_lock_irq(&blkcg->lock);
1045
1046 while (!hlist_empty(&blkcg->blkg_list)) {
1047 struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
1048 struct blkcg_gq, blkcg_node);
1049 struct request_queue *q = blkg->q;
1050
1051 if (need_resched() || !spin_trylock(&q->queue_lock)) {
1052 /*
1053 * Given that the system can accumulate a huge number
1054 * of blkgs in pathological cases, check to see if we
1055 * need to rescheduling to avoid softlockup.
1056 */
1057 spin_unlock_irq(&blkcg->lock);
1058 cond_resched();
1059 spin_lock_irq(&blkcg->lock);
1060 continue;
1061 }
1062
1063 blkg_destroy(blkg);
1064 spin_unlock(&q->queue_lock);
1065 }
1066
1067 spin_unlock_irq(&blkcg->lock);
1068 }
1069
1070 /**
1071 * blkcg_pin_online - pin online state
1072 * @blkcg_css: blkcg of interest
1073 *
1074 * While pinned, a blkcg is kept online. This is primarily used to
1075 * impedance-match blkg and cgwb lifetimes so that blkg doesn't go offline
1076 * while an associated cgwb is still active.
1077 */
blkcg_pin_online(struct cgroup_subsys_state * blkcg_css)1078 void blkcg_pin_online(struct cgroup_subsys_state *blkcg_css)
1079 {
1080 refcount_inc(&css_to_blkcg(blkcg_css)->online_pin);
1081 }
1082
1083 /**
1084 * blkcg_unpin_online - unpin online state
1085 * @blkcg_css: blkcg of interest
1086 *
1087 * This is primarily used to impedance-match blkg and cgwb lifetimes so
1088 * that blkg doesn't go offline while an associated cgwb is still active.
1089 * When this count goes to zero, all active cgwbs have finished so the
1090 * blkcg can continue destruction by calling blkcg_destroy_blkgs().
1091 */
blkcg_unpin_online(struct cgroup_subsys_state * blkcg_css)1092 void blkcg_unpin_online(struct cgroup_subsys_state *blkcg_css)
1093 {
1094 struct blkcg *blkcg = css_to_blkcg(blkcg_css);
1095
1096 do {
1097 if (!refcount_dec_and_test(&blkcg->online_pin))
1098 break;
1099 blkcg_destroy_blkgs(blkcg);
1100 blkcg = blkcg_parent(blkcg);
1101 } while (blkcg);
1102 }
1103
1104 /**
1105 * blkcg_css_offline - cgroup css_offline callback
1106 * @css: css of interest
1107 *
1108 * This function is called when @css is about to go away. Here the cgwbs are
1109 * offlined first and only once writeback associated with the blkcg has
1110 * finished do we start step 2 (see above).
1111 */
blkcg_css_offline(struct cgroup_subsys_state * css)1112 static void blkcg_css_offline(struct cgroup_subsys_state *css)
1113 {
1114 /* this prevents anyone from attaching or migrating to this blkcg */
1115 wb_blkcg_offline(css);
1116
1117 /* put the base online pin allowing step 2 to be triggered */
1118 blkcg_unpin_online(css);
1119 }
1120
blkcg_css_free(struct cgroup_subsys_state * css)1121 static void blkcg_css_free(struct cgroup_subsys_state *css)
1122 {
1123 struct blkcg *blkcg = css_to_blkcg(css);
1124 int i;
1125
1126 mutex_lock(&blkcg_pol_mutex);
1127
1128 list_del(&blkcg->all_blkcgs_node);
1129
1130 for (i = 0; i < BLKCG_MAX_POLS; i++)
1131 if (blkcg->cpd[i])
1132 blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
1133
1134 mutex_unlock(&blkcg_pol_mutex);
1135
1136 kfree(blkcg);
1137 }
1138
1139 static struct cgroup_subsys_state *
blkcg_css_alloc(struct cgroup_subsys_state * parent_css)1140 blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
1141 {
1142 struct blkcg *blkcg;
1143 struct cgroup_subsys_state *ret;
1144 int i;
1145
1146 mutex_lock(&blkcg_pol_mutex);
1147
1148 if (!parent_css) {
1149 blkcg = &blkcg_root;
1150 } else {
1151 blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
1152 if (!blkcg) {
1153 ret = ERR_PTR(-ENOMEM);
1154 goto unlock;
1155 }
1156 }
1157
1158 for (i = 0; i < BLKCG_MAX_POLS ; i++) {
1159 struct blkcg_policy *pol = blkcg_policy[i];
1160 struct blkcg_policy_data *cpd;
1161
1162 /*
1163 * If the policy hasn't been attached yet, wait for it
1164 * to be attached before doing anything else. Otherwise,
1165 * check if the policy requires any specific per-cgroup
1166 * data: if it does, allocate and initialize it.
1167 */
1168 if (!pol || !pol->cpd_alloc_fn)
1169 continue;
1170
1171 cpd = pol->cpd_alloc_fn(GFP_KERNEL);
1172 if (!cpd) {
1173 ret = ERR_PTR(-ENOMEM);
1174 goto free_pd_blkcg;
1175 }
1176 blkcg->cpd[i] = cpd;
1177 cpd->blkcg = blkcg;
1178 cpd->plid = i;
1179 if (pol->cpd_init_fn)
1180 pol->cpd_init_fn(cpd);
1181 }
1182
1183 spin_lock_init(&blkcg->lock);
1184 refcount_set(&blkcg->online_pin, 1);
1185 INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT | __GFP_NOWARN);
1186 INIT_HLIST_HEAD(&blkcg->blkg_list);
1187 #ifdef CONFIG_CGROUP_WRITEBACK
1188 INIT_LIST_HEAD(&blkcg->cgwb_list);
1189 #endif
1190 list_add_tail(&blkcg->all_blkcgs_node, &all_blkcgs);
1191
1192 mutex_unlock(&blkcg_pol_mutex);
1193 return &blkcg->css;
1194
1195 free_pd_blkcg:
1196 for (i--; i >= 0; i--)
1197 if (blkcg->cpd[i])
1198 blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
1199
1200 if (blkcg != &blkcg_root)
1201 kfree(blkcg);
1202 unlock:
1203 mutex_unlock(&blkcg_pol_mutex);
1204 return ret;
1205 }
1206
blkcg_css_online(struct cgroup_subsys_state * css)1207 static int blkcg_css_online(struct cgroup_subsys_state *css)
1208 {
1209 struct blkcg *parent = blkcg_parent(css_to_blkcg(css));
1210
1211 /*
1212 * blkcg_pin_online() is used to delay blkcg offline so that blkgs
1213 * don't go offline while cgwbs are still active on them. Pin the
1214 * parent so that offline always happens towards the root.
1215 */
1216 if (parent)
1217 blkcg_pin_online(&parent->css);
1218 return 0;
1219 }
1220
blkcg_init_disk(struct gendisk * disk)1221 int blkcg_init_disk(struct gendisk *disk)
1222 {
1223 struct request_queue *q = disk->queue;
1224 struct blkcg_gq *new_blkg, *blkg;
1225 bool preloaded;
1226 int ret;
1227
1228 INIT_LIST_HEAD(&q->blkg_list);
1229
1230 new_blkg = blkg_alloc(&blkcg_root, disk, GFP_KERNEL);
1231 if (!new_blkg)
1232 return -ENOMEM;
1233
1234 preloaded = !radix_tree_preload(GFP_KERNEL);
1235
1236 /* Make sure the root blkg exists. */
1237 /* spin_lock_irq can serve as RCU read-side critical section. */
1238 spin_lock_irq(&q->queue_lock);
1239 blkg = blkg_create(&blkcg_root, disk, new_blkg);
1240 if (IS_ERR(blkg))
1241 goto err_unlock;
1242 q->root_blkg = blkg;
1243 spin_unlock_irq(&q->queue_lock);
1244
1245 if (preloaded)
1246 radix_tree_preload_end();
1247
1248 ret = blk_ioprio_init(disk);
1249 if (ret)
1250 goto err_destroy_all;
1251
1252 ret = blk_throtl_init(disk);
1253 if (ret)
1254 goto err_ioprio_exit;
1255
1256 ret = blk_iolatency_init(disk);
1257 if (ret)
1258 goto err_throtl_exit;
1259
1260 return 0;
1261
1262 err_throtl_exit:
1263 blk_throtl_exit(disk);
1264 err_ioprio_exit:
1265 blk_ioprio_exit(disk);
1266 err_destroy_all:
1267 blkg_destroy_all(disk);
1268 return ret;
1269 err_unlock:
1270 spin_unlock_irq(&q->queue_lock);
1271 if (preloaded)
1272 radix_tree_preload_end();
1273 return PTR_ERR(blkg);
1274 }
1275
blkcg_exit_disk(struct gendisk * disk)1276 void blkcg_exit_disk(struct gendisk *disk)
1277 {
1278 blkg_destroy_all(disk);
1279 rq_qos_exit(disk->queue);
1280 blk_throtl_exit(disk);
1281 }
1282
blkcg_bind(struct cgroup_subsys_state * root_css)1283 static void blkcg_bind(struct cgroup_subsys_state *root_css)
1284 {
1285 int i;
1286
1287 mutex_lock(&blkcg_pol_mutex);
1288
1289 for (i = 0; i < BLKCG_MAX_POLS; i++) {
1290 struct blkcg_policy *pol = blkcg_policy[i];
1291 struct blkcg *blkcg;
1292
1293 if (!pol || !pol->cpd_bind_fn)
1294 continue;
1295
1296 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node)
1297 if (blkcg->cpd[pol->plid])
1298 pol->cpd_bind_fn(blkcg->cpd[pol->plid]);
1299 }
1300 mutex_unlock(&blkcg_pol_mutex);
1301 }
1302
blkcg_exit(struct task_struct * tsk)1303 static void blkcg_exit(struct task_struct *tsk)
1304 {
1305 if (tsk->throttle_queue)
1306 blk_put_queue(tsk->throttle_queue);
1307 tsk->throttle_queue = NULL;
1308 }
1309
1310 struct cgroup_subsys io_cgrp_subsys = {
1311 .css_alloc = blkcg_css_alloc,
1312 .css_online = blkcg_css_online,
1313 .css_offline = blkcg_css_offline,
1314 .css_free = blkcg_css_free,
1315 .css_rstat_flush = blkcg_rstat_flush,
1316 .bind = blkcg_bind,
1317 .dfl_cftypes = blkcg_files,
1318 .legacy_cftypes = blkcg_legacy_files,
1319 .legacy_name = "blkio",
1320 .exit = blkcg_exit,
1321 #ifdef CONFIG_MEMCG
1322 /*
1323 * This ensures that, if available, memcg is automatically enabled
1324 * together on the default hierarchy so that the owner cgroup can
1325 * be retrieved from writeback pages.
1326 */
1327 .depends_on = 1 << memory_cgrp_id,
1328 #endif
1329 };
1330 EXPORT_SYMBOL_GPL(io_cgrp_subsys);
1331
1332 /**
1333 * blkcg_activate_policy - activate a blkcg policy on a request_queue
1334 * @q: request_queue of interest
1335 * @pol: blkcg policy to activate
1336 *
1337 * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through
1338 * bypass mode to populate its blkgs with policy_data for @pol.
1339 *
1340 * Activation happens with @q bypassed, so nobody would be accessing blkgs
1341 * from IO path. Update of each blkg is protected by both queue and blkcg
1342 * locks so that holding either lock and testing blkcg_policy_enabled() is
1343 * always enough for dereferencing policy data.
1344 *
1345 * The caller is responsible for synchronizing [de]activations and policy
1346 * [un]registerations. Returns 0 on success, -errno on failure.
1347 */
blkcg_activate_policy(struct request_queue * q,const struct blkcg_policy * pol)1348 int blkcg_activate_policy(struct request_queue *q,
1349 const struct blkcg_policy *pol)
1350 {
1351 struct blkg_policy_data *pd_prealloc = NULL;
1352 struct blkcg_gq *blkg, *pinned_blkg = NULL;
1353 int ret;
1354
1355 if (blkcg_policy_enabled(q, pol))
1356 return 0;
1357
1358 if (queue_is_mq(q))
1359 blk_mq_freeze_queue(q);
1360 retry:
1361 spin_lock_irq(&q->queue_lock);
1362
1363 /* blkg_list is pushed at the head, reverse walk to allocate parents first */
1364 list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) {
1365 struct blkg_policy_data *pd;
1366
1367 if (blkg->pd[pol->plid])
1368 continue;
1369
1370 /* If prealloc matches, use it; otherwise try GFP_NOWAIT */
1371 if (blkg == pinned_blkg) {
1372 pd = pd_prealloc;
1373 pd_prealloc = NULL;
1374 } else {
1375 pd = pol->pd_alloc_fn(GFP_NOWAIT | __GFP_NOWARN, q,
1376 blkg->blkcg);
1377 }
1378
1379 if (!pd) {
1380 /*
1381 * GFP_NOWAIT failed. Free the existing one and
1382 * prealloc for @blkg w/ GFP_KERNEL.
1383 */
1384 if (pinned_blkg)
1385 blkg_put(pinned_blkg);
1386 blkg_get(blkg);
1387 pinned_blkg = blkg;
1388
1389 spin_unlock_irq(&q->queue_lock);
1390
1391 if (pd_prealloc)
1392 pol->pd_free_fn(pd_prealloc);
1393 pd_prealloc = pol->pd_alloc_fn(GFP_KERNEL, q,
1394 blkg->blkcg);
1395 if (pd_prealloc)
1396 goto retry;
1397 else
1398 goto enomem;
1399 }
1400
1401 blkg->pd[pol->plid] = pd;
1402 pd->blkg = blkg;
1403 pd->plid = pol->plid;
1404 }
1405
1406 /* all allocated, init in the same order */
1407 if (pol->pd_init_fn)
1408 list_for_each_entry_reverse(blkg, &q->blkg_list, q_node)
1409 pol->pd_init_fn(blkg->pd[pol->plid]);
1410
1411 __set_bit(pol->plid, q->blkcg_pols);
1412 ret = 0;
1413
1414 spin_unlock_irq(&q->queue_lock);
1415 out:
1416 if (queue_is_mq(q))
1417 blk_mq_unfreeze_queue(q);
1418 if (pinned_blkg)
1419 blkg_put(pinned_blkg);
1420 if (pd_prealloc)
1421 pol->pd_free_fn(pd_prealloc);
1422 return ret;
1423
1424 enomem:
1425 /* alloc failed, nothing's initialized yet, free everything */
1426 spin_lock_irq(&q->queue_lock);
1427 list_for_each_entry(blkg, &q->blkg_list, q_node) {
1428 struct blkcg *blkcg = blkg->blkcg;
1429
1430 spin_lock(&blkcg->lock);
1431 if (blkg->pd[pol->plid]) {
1432 pol->pd_free_fn(blkg->pd[pol->plid]);
1433 blkg->pd[pol->plid] = NULL;
1434 }
1435 spin_unlock(&blkcg->lock);
1436 }
1437 spin_unlock_irq(&q->queue_lock);
1438 ret = -ENOMEM;
1439 goto out;
1440 }
1441 EXPORT_SYMBOL_GPL(blkcg_activate_policy);
1442
1443 /**
1444 * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
1445 * @q: request_queue of interest
1446 * @pol: blkcg policy to deactivate
1447 *
1448 * Deactivate @pol on @q. Follows the same synchronization rules as
1449 * blkcg_activate_policy().
1450 */
blkcg_deactivate_policy(struct request_queue * q,const struct blkcg_policy * pol)1451 void blkcg_deactivate_policy(struct request_queue *q,
1452 const struct blkcg_policy *pol)
1453 {
1454 struct blkcg_gq *blkg;
1455
1456 if (!blkcg_policy_enabled(q, pol))
1457 return;
1458
1459 if (queue_is_mq(q))
1460 blk_mq_freeze_queue(q);
1461
1462 spin_lock_irq(&q->queue_lock);
1463
1464 __clear_bit(pol->plid, q->blkcg_pols);
1465
1466 list_for_each_entry(blkg, &q->blkg_list, q_node) {
1467 struct blkcg *blkcg = blkg->blkcg;
1468
1469 spin_lock(&blkcg->lock);
1470 if (blkg->pd[pol->plid]) {
1471 if (pol->pd_offline_fn)
1472 pol->pd_offline_fn(blkg->pd[pol->plid]);
1473 pol->pd_free_fn(blkg->pd[pol->plid]);
1474 blkg->pd[pol->plid] = NULL;
1475 }
1476 spin_unlock(&blkcg->lock);
1477 }
1478
1479 spin_unlock_irq(&q->queue_lock);
1480
1481 if (queue_is_mq(q))
1482 blk_mq_unfreeze_queue(q);
1483 }
1484 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
1485
blkcg_free_all_cpd(struct blkcg_policy * pol)1486 static void blkcg_free_all_cpd(struct blkcg_policy *pol)
1487 {
1488 struct blkcg *blkcg;
1489
1490 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1491 if (blkcg->cpd[pol->plid]) {
1492 pol->cpd_free_fn(blkcg->cpd[pol->plid]);
1493 blkcg->cpd[pol->plid] = NULL;
1494 }
1495 }
1496 }
1497
1498 /**
1499 * blkcg_policy_register - register a blkcg policy
1500 * @pol: blkcg policy to register
1501 *
1502 * Register @pol with blkcg core. Might sleep and @pol may be modified on
1503 * successful registration. Returns 0 on success and -errno on failure.
1504 */
blkcg_policy_register(struct blkcg_policy * pol)1505 int blkcg_policy_register(struct blkcg_policy *pol)
1506 {
1507 struct blkcg *blkcg;
1508 int i, ret;
1509
1510 mutex_lock(&blkcg_pol_register_mutex);
1511 mutex_lock(&blkcg_pol_mutex);
1512
1513 /* find an empty slot */
1514 ret = -ENOSPC;
1515 for (i = 0; i < BLKCG_MAX_POLS; i++)
1516 if (!blkcg_policy[i])
1517 break;
1518 if (i >= BLKCG_MAX_POLS) {
1519 pr_warn("blkcg_policy_register: BLKCG_MAX_POLS too small\n");
1520 goto err_unlock;
1521 }
1522
1523 /* Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs */
1524 if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) ||
1525 (!pol->pd_alloc_fn ^ !pol->pd_free_fn))
1526 goto err_unlock;
1527
1528 /* register @pol */
1529 pol->plid = i;
1530 blkcg_policy[pol->plid] = pol;
1531
1532 /* allocate and install cpd's */
1533 if (pol->cpd_alloc_fn) {
1534 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1535 struct blkcg_policy_data *cpd;
1536
1537 cpd = pol->cpd_alloc_fn(GFP_KERNEL);
1538 if (!cpd)
1539 goto err_free_cpds;
1540
1541 blkcg->cpd[pol->plid] = cpd;
1542 cpd->blkcg = blkcg;
1543 cpd->plid = pol->plid;
1544 if (pol->cpd_init_fn)
1545 pol->cpd_init_fn(cpd);
1546 }
1547 }
1548
1549 mutex_unlock(&blkcg_pol_mutex);
1550
1551 /* everything is in place, add intf files for the new policy */
1552 if (pol->dfl_cftypes)
1553 WARN_ON(cgroup_add_dfl_cftypes(&io_cgrp_subsys,
1554 pol->dfl_cftypes));
1555 if (pol->legacy_cftypes)
1556 WARN_ON(cgroup_add_legacy_cftypes(&io_cgrp_subsys,
1557 pol->legacy_cftypes));
1558 mutex_unlock(&blkcg_pol_register_mutex);
1559 return 0;
1560
1561 err_free_cpds:
1562 if (pol->cpd_free_fn)
1563 blkcg_free_all_cpd(pol);
1564
1565 blkcg_policy[pol->plid] = NULL;
1566 err_unlock:
1567 mutex_unlock(&blkcg_pol_mutex);
1568 mutex_unlock(&blkcg_pol_register_mutex);
1569 return ret;
1570 }
1571 EXPORT_SYMBOL_GPL(blkcg_policy_register);
1572
1573 /**
1574 * blkcg_policy_unregister - unregister a blkcg policy
1575 * @pol: blkcg policy to unregister
1576 *
1577 * Undo blkcg_policy_register(@pol). Might sleep.
1578 */
blkcg_policy_unregister(struct blkcg_policy * pol)1579 void blkcg_policy_unregister(struct blkcg_policy *pol)
1580 {
1581 mutex_lock(&blkcg_pol_register_mutex);
1582
1583 if (WARN_ON(blkcg_policy[pol->plid] != pol))
1584 goto out_unlock;
1585
1586 /* kill the intf files first */
1587 if (pol->dfl_cftypes)
1588 cgroup_rm_cftypes(pol->dfl_cftypes);
1589 if (pol->legacy_cftypes)
1590 cgroup_rm_cftypes(pol->legacy_cftypes);
1591
1592 /* remove cpds and unregister */
1593 mutex_lock(&blkcg_pol_mutex);
1594
1595 if (pol->cpd_free_fn)
1596 blkcg_free_all_cpd(pol);
1597
1598 blkcg_policy[pol->plid] = NULL;
1599
1600 mutex_unlock(&blkcg_pol_mutex);
1601 out_unlock:
1602 mutex_unlock(&blkcg_pol_register_mutex);
1603 }
1604 EXPORT_SYMBOL_GPL(blkcg_policy_unregister);
1605
__blkcg_punt_bio_submit(struct bio * bio)1606 bool __blkcg_punt_bio_submit(struct bio *bio)
1607 {
1608 struct blkcg_gq *blkg = bio->bi_blkg;
1609
1610 /* consume the flag first */
1611 bio->bi_opf &= ~REQ_CGROUP_PUNT;
1612
1613 /* never bounce for the root cgroup */
1614 if (!blkg->parent)
1615 return false;
1616
1617 spin_lock_bh(&blkg->async_bio_lock);
1618 bio_list_add(&blkg->async_bios, bio);
1619 spin_unlock_bh(&blkg->async_bio_lock);
1620
1621 queue_work(blkcg_punt_bio_wq, &blkg->async_bio_work);
1622 return true;
1623 }
1624
1625 /*
1626 * Scale the accumulated delay based on how long it has been since we updated
1627 * the delay. We only call this when we are adding delay, in case it's been a
1628 * while since we added delay, and when we are checking to see if we need to
1629 * delay a task, to account for any delays that may have occurred.
1630 */
blkcg_scale_delay(struct blkcg_gq * blkg,u64 now)1631 static void blkcg_scale_delay(struct blkcg_gq *blkg, u64 now)
1632 {
1633 u64 old = atomic64_read(&blkg->delay_start);
1634
1635 /* negative use_delay means no scaling, see blkcg_set_delay() */
1636 if (atomic_read(&blkg->use_delay) < 0)
1637 return;
1638
1639 /*
1640 * We only want to scale down every second. The idea here is that we
1641 * want to delay people for min(delay_nsec, NSEC_PER_SEC) in a certain
1642 * time window. We only want to throttle tasks for recent delay that
1643 * has occurred, in 1 second time windows since that's the maximum
1644 * things can be throttled. We save the current delay window in
1645 * blkg->last_delay so we know what amount is still left to be charged
1646 * to the blkg from this point onward. blkg->last_use keeps track of
1647 * the use_delay counter. The idea is if we're unthrottling the blkg we
1648 * are ok with whatever is happening now, and we can take away more of
1649 * the accumulated delay as we've already throttled enough that
1650 * everybody is happy with their IO latencies.
1651 */
1652 if (time_before64(old + NSEC_PER_SEC, now) &&
1653 atomic64_try_cmpxchg(&blkg->delay_start, &old, now)) {
1654 u64 cur = atomic64_read(&blkg->delay_nsec);
1655 u64 sub = min_t(u64, blkg->last_delay, now - old);
1656 int cur_use = atomic_read(&blkg->use_delay);
1657
1658 /*
1659 * We've been unthrottled, subtract a larger chunk of our
1660 * accumulated delay.
1661 */
1662 if (cur_use < blkg->last_use)
1663 sub = max_t(u64, sub, blkg->last_delay >> 1);
1664
1665 /*
1666 * This shouldn't happen, but handle it anyway. Our delay_nsec
1667 * should only ever be growing except here where we subtract out
1668 * min(last_delay, 1 second), but lord knows bugs happen and I'd
1669 * rather not end up with negative numbers.
1670 */
1671 if (unlikely(cur < sub)) {
1672 atomic64_set(&blkg->delay_nsec, 0);
1673 blkg->last_delay = 0;
1674 } else {
1675 atomic64_sub(sub, &blkg->delay_nsec);
1676 blkg->last_delay = cur - sub;
1677 }
1678 blkg->last_use = cur_use;
1679 }
1680 }
1681
1682 /*
1683 * This is called when we want to actually walk up the hierarchy and check to
1684 * see if we need to throttle, and then actually throttle if there is some
1685 * accumulated delay. This should only be called upon return to user space so
1686 * we're not holding some lock that would induce a priority inversion.
1687 */
blkcg_maybe_throttle_blkg(struct blkcg_gq * blkg,bool use_memdelay)1688 static void blkcg_maybe_throttle_blkg(struct blkcg_gq *blkg, bool use_memdelay)
1689 {
1690 unsigned long pflags;
1691 bool clamp;
1692 u64 now = ktime_to_ns(ktime_get());
1693 u64 exp;
1694 u64 delay_nsec = 0;
1695 int tok;
1696
1697 while (blkg->parent) {
1698 int use_delay = atomic_read(&blkg->use_delay);
1699
1700 if (use_delay) {
1701 u64 this_delay;
1702
1703 blkcg_scale_delay(blkg, now);
1704 this_delay = atomic64_read(&blkg->delay_nsec);
1705 if (this_delay > delay_nsec) {
1706 delay_nsec = this_delay;
1707 clamp = use_delay > 0;
1708 }
1709 }
1710 blkg = blkg->parent;
1711 }
1712
1713 if (!delay_nsec)
1714 return;
1715
1716 /*
1717 * Let's not sleep for all eternity if we've amassed a huge delay.
1718 * Swapping or metadata IO can accumulate 10's of seconds worth of
1719 * delay, and we want userspace to be able to do _something_ so cap the
1720 * delays at 0.25s. If there's 10's of seconds worth of delay then the
1721 * tasks will be delayed for 0.25 second for every syscall. If
1722 * blkcg_set_delay() was used as indicated by negative use_delay, the
1723 * caller is responsible for regulating the range.
1724 */
1725 if (clamp)
1726 delay_nsec = min_t(u64, delay_nsec, 250 * NSEC_PER_MSEC);
1727
1728 if (use_memdelay)
1729 psi_memstall_enter(&pflags);
1730
1731 exp = ktime_add_ns(now, delay_nsec);
1732 tok = io_schedule_prepare();
1733 do {
1734 __set_current_state(TASK_KILLABLE);
1735 if (!schedule_hrtimeout(&exp, HRTIMER_MODE_ABS))
1736 break;
1737 } while (!fatal_signal_pending(current));
1738 io_schedule_finish(tok);
1739
1740 if (use_memdelay)
1741 psi_memstall_leave(&pflags);
1742 }
1743
1744 /**
1745 * blkcg_maybe_throttle_current - throttle the current task if it has been marked
1746 *
1747 * This is only called if we've been marked with set_notify_resume(). Obviously
1748 * we can be set_notify_resume() for reasons other than blkcg throttling, so we
1749 * check to see if current->throttle_queue is set and if not this doesn't do
1750 * anything. This should only ever be called by the resume code, it's not meant
1751 * to be called by people willy-nilly as it will actually do the work to
1752 * throttle the task if it is setup for throttling.
1753 */
blkcg_maybe_throttle_current(void)1754 void blkcg_maybe_throttle_current(void)
1755 {
1756 struct request_queue *q = current->throttle_queue;
1757 struct blkcg *blkcg;
1758 struct blkcg_gq *blkg;
1759 bool use_memdelay = current->use_memdelay;
1760
1761 if (!q)
1762 return;
1763
1764 current->throttle_queue = NULL;
1765 current->use_memdelay = false;
1766
1767 rcu_read_lock();
1768 blkcg = css_to_blkcg(blkcg_css());
1769 if (!blkcg)
1770 goto out;
1771 blkg = blkg_lookup(blkcg, q);
1772 if (!blkg)
1773 goto out;
1774 if (!blkg_tryget(blkg))
1775 goto out;
1776 rcu_read_unlock();
1777
1778 blkcg_maybe_throttle_blkg(blkg, use_memdelay);
1779 blkg_put(blkg);
1780 blk_put_queue(q);
1781 return;
1782 out:
1783 rcu_read_unlock();
1784 blk_put_queue(q);
1785 }
1786
1787 /**
1788 * blkcg_schedule_throttle - this task needs to check for throttling
1789 * @gendisk: disk to throttle
1790 * @use_memdelay: do we charge this to memory delay for PSI
1791 *
1792 * This is called by the IO controller when we know there's delay accumulated
1793 * for the blkg for this task. We do not pass the blkg because there are places
1794 * we call this that may not have that information, the swapping code for
1795 * instance will only have a block_device at that point. This set's the
1796 * notify_resume for the task to check and see if it requires throttling before
1797 * returning to user space.
1798 *
1799 * We will only schedule once per syscall. You can call this over and over
1800 * again and it will only do the check once upon return to user space, and only
1801 * throttle once. If the task needs to be throttled again it'll need to be
1802 * re-set at the next time we see the task.
1803 */
blkcg_schedule_throttle(struct gendisk * disk,bool use_memdelay)1804 void blkcg_schedule_throttle(struct gendisk *disk, bool use_memdelay)
1805 {
1806 struct request_queue *q = disk->queue;
1807
1808 if (unlikely(current->flags & PF_KTHREAD))
1809 return;
1810
1811 if (current->throttle_queue != q) {
1812 if (!blk_get_queue(q))
1813 return;
1814
1815 if (current->throttle_queue)
1816 blk_put_queue(current->throttle_queue);
1817 current->throttle_queue = q;
1818 }
1819
1820 if (use_memdelay)
1821 current->use_memdelay = use_memdelay;
1822 set_notify_resume(current);
1823 }
1824
1825 /**
1826 * blkcg_add_delay - add delay to this blkg
1827 * @blkg: blkg of interest
1828 * @now: the current time in nanoseconds
1829 * @delta: how many nanoseconds of delay to add
1830 *
1831 * Charge @delta to the blkg's current delay accumulation. This is used to
1832 * throttle tasks if an IO controller thinks we need more throttling.
1833 */
blkcg_add_delay(struct blkcg_gq * blkg,u64 now,u64 delta)1834 void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta)
1835 {
1836 if (WARN_ON_ONCE(atomic_read(&blkg->use_delay) < 0))
1837 return;
1838 blkcg_scale_delay(blkg, now);
1839 atomic64_add(delta, &blkg->delay_nsec);
1840 }
1841
1842 /**
1843 * blkg_tryget_closest - try and get a blkg ref on the closet blkg
1844 * @bio: target bio
1845 * @css: target css
1846 *
1847 * As the failure mode here is to walk up the blkg tree, this ensure that the
1848 * blkg->parent pointers are always valid. This returns the blkg that it ended
1849 * up taking a reference on or %NULL if no reference was taken.
1850 */
blkg_tryget_closest(struct bio * bio,struct cgroup_subsys_state * css)1851 static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio,
1852 struct cgroup_subsys_state *css)
1853 {
1854 struct blkcg_gq *blkg, *ret_blkg = NULL;
1855
1856 rcu_read_lock();
1857 blkg = blkg_lookup_create(css_to_blkcg(css), bio->bi_bdev->bd_disk);
1858 while (blkg) {
1859 if (blkg_tryget(blkg)) {
1860 ret_blkg = blkg;
1861 break;
1862 }
1863 blkg = blkg->parent;
1864 }
1865 rcu_read_unlock();
1866
1867 return ret_blkg;
1868 }
1869
1870 /**
1871 * bio_associate_blkg_from_css - associate a bio with a specified css
1872 * @bio: target bio
1873 * @css: target css
1874 *
1875 * Associate @bio with the blkg found by combining the css's blkg and the
1876 * request_queue of the @bio. An association failure is handled by walking up
1877 * the blkg tree. Therefore, the blkg associated can be anything between @blkg
1878 * and q->root_blkg. This situation only happens when a cgroup is dying and
1879 * then the remaining bios will spill to the closest alive blkg.
1880 *
1881 * A reference will be taken on the blkg and will be released when @bio is
1882 * freed.
1883 */
bio_associate_blkg_from_css(struct bio * bio,struct cgroup_subsys_state * css)1884 void bio_associate_blkg_from_css(struct bio *bio,
1885 struct cgroup_subsys_state *css)
1886 {
1887 if (bio->bi_blkg)
1888 blkg_put(bio->bi_blkg);
1889
1890 if (css && css->parent) {
1891 bio->bi_blkg = blkg_tryget_closest(bio, css);
1892 } else {
1893 blkg_get(bdev_get_queue(bio->bi_bdev)->root_blkg);
1894 bio->bi_blkg = bdev_get_queue(bio->bi_bdev)->root_blkg;
1895 }
1896 }
1897 EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);
1898
1899 /**
1900 * bio_associate_blkg - associate a bio with a blkg
1901 * @bio: target bio
1902 *
1903 * Associate @bio with the blkg found from the bio's css and request_queue.
1904 * If one is not found, bio_lookup_blkg() creates the blkg. If a blkg is
1905 * already associated, the css is reused and association redone as the
1906 * request_queue may have changed.
1907 */
bio_associate_blkg(struct bio * bio)1908 void bio_associate_blkg(struct bio *bio)
1909 {
1910 struct cgroup_subsys_state *css;
1911
1912 rcu_read_lock();
1913
1914 if (bio->bi_blkg)
1915 css = bio_blkcg_css(bio);
1916 else
1917 css = blkcg_css();
1918
1919 bio_associate_blkg_from_css(bio, css);
1920
1921 rcu_read_unlock();
1922 }
1923 EXPORT_SYMBOL_GPL(bio_associate_blkg);
1924
1925 /**
1926 * bio_clone_blkg_association - clone blkg association from src to dst bio
1927 * @dst: destination bio
1928 * @src: source bio
1929 */
bio_clone_blkg_association(struct bio * dst,struct bio * src)1930 void bio_clone_blkg_association(struct bio *dst, struct bio *src)
1931 {
1932 if (src->bi_blkg)
1933 bio_associate_blkg_from_css(dst, bio_blkcg_css(src));
1934 }
1935 EXPORT_SYMBOL_GPL(bio_clone_blkg_association);
1936
blk_cgroup_io_type(struct bio * bio)1937 static int blk_cgroup_io_type(struct bio *bio)
1938 {
1939 if (op_is_discard(bio->bi_opf))
1940 return BLKG_IOSTAT_DISCARD;
1941 if (op_is_write(bio->bi_opf))
1942 return BLKG_IOSTAT_WRITE;
1943 return BLKG_IOSTAT_READ;
1944 }
1945
blk_cgroup_bio_start(struct bio * bio)1946 void blk_cgroup_bio_start(struct bio *bio)
1947 {
1948 int rwd = blk_cgroup_io_type(bio), cpu;
1949 struct blkg_iostat_set *bis;
1950 unsigned long flags;
1951
1952 cpu = get_cpu();
1953 bis = per_cpu_ptr(bio->bi_blkg->iostat_cpu, cpu);
1954 flags = u64_stats_update_begin_irqsave(&bis->sync);
1955
1956 /*
1957 * If the bio is flagged with BIO_CGROUP_ACCT it means this is a split
1958 * bio and we would have already accounted for the size of the bio.
1959 */
1960 if (!bio_flagged(bio, BIO_CGROUP_ACCT)) {
1961 bio_set_flag(bio, BIO_CGROUP_ACCT);
1962 bis->cur.bytes[rwd] += bio->bi_iter.bi_size;
1963 }
1964 bis->cur.ios[rwd]++;
1965
1966 u64_stats_update_end_irqrestore(&bis->sync, flags);
1967 if (cgroup_subsys_on_dfl(io_cgrp_subsys))
1968 cgroup_rstat_updated(bio->bi_blkg->blkcg->css.cgroup, cpu);
1969 put_cpu();
1970 }
1971
blk_cgroup_congested(void)1972 bool blk_cgroup_congested(void)
1973 {
1974 struct cgroup_subsys_state *css;
1975 bool ret = false;
1976
1977 rcu_read_lock();
1978 for (css = blkcg_css(); css; css = css->parent) {
1979 if (atomic_read(&css->cgroup->congestion_count)) {
1980 ret = true;
1981 break;
1982 }
1983 }
1984 rcu_read_unlock();
1985 return ret;
1986 }
1987
blkcg_init(void)1988 static int __init blkcg_init(void)
1989 {
1990 blkcg_punt_bio_wq = alloc_workqueue("blkcg_punt_bio",
1991 WQ_MEM_RECLAIM | WQ_FREEZABLE |
1992 WQ_UNBOUND | WQ_SYSFS, 0);
1993 if (!blkcg_punt_bio_wq)
1994 return -ENOMEM;
1995 return 0;
1996 }
1997 subsys_initcall(blkcg_init);
1998
1999 module_param(blkcg_debug_stats, bool, 0644);
2000 MODULE_PARM_DESC(blkcg_debug_stats, "True if you want debug stats, false if not");
2001