1 // SPDX-License-Identifier: GPL-2.0
3 * Common Block IO controller cgroup interface
5 * Based on ideas and code from CFQ, CFS and BFQ:
6 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
8 * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
9 * Paolo Valente <paolo.valente@unimore.it>
11 * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
12 * Nauman Rafique <nauman@google.com>
14 * For policy-specific per-blkcg data:
15 * Copyright (C) 2015 Paolo Valente <paolo.valente@unimore.it>
16 * Arianna Avanzini <avanzini.arianna@gmail.com>
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/genhd.h>
27 #include <linux/delay.h>
28 #include <linux/atomic.h>
29 #include <linux/ctype.h>
30 #include <linux/blk-cgroup.h>
31 #include <linux/tracehook.h>
32 #include <linux/psi.h>
34 #include "blk-ioprio.h"
37 * blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation.
38 * blkcg_pol_register_mutex nests outside of it and synchronizes entire
39 * policy [un]register operations including cgroup file additions /
40 * removals. Putting cgroup file registration outside blkcg_pol_mutex
41 * allows grabbing it from cgroup callbacks.
43 static DEFINE_MUTEX(blkcg_pol_register_mutex);
44 static DEFINE_MUTEX(blkcg_pol_mutex);
46 struct blkcg blkcg_root;
47 EXPORT_SYMBOL_GPL(blkcg_root);
49 struct cgroup_subsys_state * const blkcg_root_css = &blkcg_root.css;
50 EXPORT_SYMBOL_GPL(blkcg_root_css);
52 static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];
54 static LIST_HEAD(all_blkcgs); /* protected by blkcg_pol_mutex */
56 bool blkcg_debug_stats = false;
57 static struct workqueue_struct *blkcg_punt_bio_wq;
59 static bool blkcg_policy_enabled(struct request_queue *q,
60 const struct blkcg_policy *pol)
62 return pol && test_bit(pol->plid, q->blkcg_pols);
66 * blkg_free - free a blkg
69 * Free @blkg which may be partially allocated.
71 static void blkg_free(struct blkcg_gq *blkg)
78 for (i = 0; i < BLKCG_MAX_POLS; i++)
80 blkcg_policy[i]->pd_free_fn(blkg->pd[i]);
82 free_percpu(blkg->iostat_cpu);
83 percpu_ref_exit(&blkg->refcnt);
87 static void __blkg_release(struct rcu_head *rcu)
89 struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head);
91 WARN_ON(!bio_list_empty(&blkg->async_bios));
93 /* release the blkcg and parent blkg refs this blkg has been holding */
94 css_put(&blkg->blkcg->css);
96 blkg_put(blkg->parent);
101 * A group is RCU protected, but having an rcu lock does not mean that one
102 * can access all the fields of blkg and assume these are valid. For
103 * example, don't try to follow throtl_data and request queue links.
105 * Having a reference to blkg under an rcu allows accesses to only values
106 * local to groups like group stats and group rate limits.
108 static void blkg_release(struct percpu_ref *ref)
110 struct blkcg_gq *blkg = container_of(ref, struct blkcg_gq, refcnt);
112 call_rcu(&blkg->rcu_head, __blkg_release);
115 static void blkg_async_bio_workfn(struct work_struct *work)
117 struct blkcg_gq *blkg = container_of(work, struct blkcg_gq,
119 struct bio_list bios = BIO_EMPTY_LIST;
121 struct blk_plug plug;
122 bool need_plug = false;
124 /* as long as there are pending bios, @blkg can't go away */
125 spin_lock_bh(&blkg->async_bio_lock);
126 bio_list_merge(&bios, &blkg->async_bios);
127 bio_list_init(&blkg->async_bios);
128 spin_unlock_bh(&blkg->async_bio_lock);
130 /* start plug only when bio_list contains at least 2 bios */
131 if (bios.head && bios.head->bi_next) {
133 blk_start_plug(&plug);
135 while ((bio = bio_list_pop(&bios)))
138 blk_finish_plug(&plug);
142 * blkg_alloc - allocate a blkg
143 * @blkcg: block cgroup the new blkg is associated with
144 * @q: request_queue the new blkg is associated with
145 * @gfp_mask: allocation mask to use
147 * Allocate a new blkg assocating @blkcg and @q.
149 static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
152 struct blkcg_gq *blkg;
155 /* alloc and init base part */
156 blkg = kzalloc_node(sizeof(*blkg), gfp_mask, q->node);
160 if (percpu_ref_init(&blkg->refcnt, blkg_release, 0, gfp_mask))
163 blkg->iostat_cpu = alloc_percpu_gfp(struct blkg_iostat_set, gfp_mask);
164 if (!blkg->iostat_cpu)
168 INIT_LIST_HEAD(&blkg->q_node);
169 spin_lock_init(&blkg->async_bio_lock);
170 bio_list_init(&blkg->async_bios);
171 INIT_WORK(&blkg->async_bio_work, blkg_async_bio_workfn);
174 u64_stats_init(&blkg->iostat.sync);
175 for_each_possible_cpu(cpu)
176 u64_stats_init(&per_cpu_ptr(blkg->iostat_cpu, cpu)->sync);
178 for (i = 0; i < BLKCG_MAX_POLS; i++) {
179 struct blkcg_policy *pol = blkcg_policy[i];
180 struct blkg_policy_data *pd;
182 if (!blkcg_policy_enabled(q, pol))
185 /* alloc per-policy data and attach it to blkg */
186 pd = pol->pd_alloc_fn(gfp_mask, q, blkcg);
202 struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
203 struct request_queue *q, bool update_hint)
205 struct blkcg_gq *blkg;
208 * Hint didn't match. Look up from the radix tree. Note that the
209 * hint can only be updated under queue_lock as otherwise @blkg
210 * could have already been removed from blkg_tree. The caller is
211 * responsible for grabbing queue_lock if @update_hint.
213 blkg = radix_tree_lookup(&blkcg->blkg_tree, q->id);
214 if (blkg && blkg->q == q) {
216 lockdep_assert_held(&q->queue_lock);
217 rcu_assign_pointer(blkcg->blkg_hint, blkg);
224 EXPORT_SYMBOL_GPL(blkg_lookup_slowpath);
227 * If @new_blkg is %NULL, this function tries to allocate a new one as
228 * necessary using %GFP_NOWAIT. @new_blkg is always consumed on return.
230 static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
231 struct request_queue *q,
232 struct blkcg_gq *new_blkg)
234 struct blkcg_gq *blkg;
237 WARN_ON_ONCE(!rcu_read_lock_held());
238 lockdep_assert_held(&q->queue_lock);
240 /* request_queue is dying, do not create/recreate a blkg */
241 if (blk_queue_dying(q)) {
246 /* blkg holds a reference to blkcg */
247 if (!css_tryget_online(&blkcg->css)) {
254 new_blkg = blkg_alloc(blkcg, q, GFP_NOWAIT | __GFP_NOWARN);
255 if (unlikely(!new_blkg)) {
263 if (blkcg_parent(blkcg)) {
264 blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false);
265 if (WARN_ON_ONCE(!blkg->parent)) {
269 blkg_get(blkg->parent);
272 /* invoke per-policy init */
273 for (i = 0; i < BLKCG_MAX_POLS; i++) {
274 struct blkcg_policy *pol = blkcg_policy[i];
276 if (blkg->pd[i] && pol->pd_init_fn)
277 pol->pd_init_fn(blkg->pd[i]);
281 spin_lock(&blkcg->lock);
282 ret = radix_tree_insert(&blkcg->blkg_tree, q->id, blkg);
284 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
285 list_add(&blkg->q_node, &q->blkg_list);
287 for (i = 0; i < BLKCG_MAX_POLS; i++) {
288 struct blkcg_policy *pol = blkcg_policy[i];
290 if (blkg->pd[i] && pol->pd_online_fn)
291 pol->pd_online_fn(blkg->pd[i]);
295 spin_unlock(&blkcg->lock);
300 /* @blkg failed fully initialized, use the usual release path */
305 css_put(&blkcg->css);
312 * blkg_lookup_create - lookup blkg, try to create one if not there
313 * @blkcg: blkcg of interest
314 * @q: request_queue of interest
316 * Lookup blkg for the @blkcg - @q pair. If it doesn't exist, try to
317 * create one. blkg creation is performed recursively from blkcg_root such
318 * that all non-root blkg's have access to the parent blkg. This function
319 * should be called under RCU read lock and takes @q->queue_lock.
321 * Returns the blkg or the closest blkg if blkg_create() fails as it walks
324 static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
325 struct request_queue *q)
327 struct blkcg_gq *blkg;
330 WARN_ON_ONCE(!rcu_read_lock_held());
332 blkg = blkg_lookup(blkcg, q);
336 spin_lock_irqsave(&q->queue_lock, flags);
337 blkg = __blkg_lookup(blkcg, q, true);
342 * Create blkgs walking down from blkcg_root to @blkcg, so that all
343 * non-root blkgs have access to their parents. Returns the closest
344 * blkg to the intended blkg should blkg_create() fail.
347 struct blkcg *pos = blkcg;
348 struct blkcg *parent = blkcg_parent(blkcg);
349 struct blkcg_gq *ret_blkg = q->root_blkg;
352 blkg = __blkg_lookup(parent, q, false);
354 /* remember closest blkg */
359 parent = blkcg_parent(parent);
362 blkg = blkg_create(pos, q, NULL);
372 spin_unlock_irqrestore(&q->queue_lock, flags);
376 static void blkg_destroy(struct blkcg_gq *blkg)
378 struct blkcg *blkcg = blkg->blkcg;
381 lockdep_assert_held(&blkg->q->queue_lock);
382 lockdep_assert_held(&blkcg->lock);
384 /* Something wrong if we are trying to remove same group twice */
385 WARN_ON_ONCE(list_empty(&blkg->q_node));
386 WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
388 for (i = 0; i < BLKCG_MAX_POLS; i++) {
389 struct blkcg_policy *pol = blkcg_policy[i];
391 if (blkg->pd[i] && pol->pd_offline_fn)
392 pol->pd_offline_fn(blkg->pd[i]);
395 blkg->online = false;
397 radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
398 list_del_init(&blkg->q_node);
399 hlist_del_init_rcu(&blkg->blkcg_node);
402 * Both setting lookup hint to and clearing it from @blkg are done
403 * under queue_lock. If it's not pointing to @blkg now, it never
404 * will. Hint assignment itself can race safely.
406 if (rcu_access_pointer(blkcg->blkg_hint) == blkg)
407 rcu_assign_pointer(blkcg->blkg_hint, NULL);
410 * Put the reference taken at the time of creation so that when all
411 * queues are gone, group can be destroyed.
413 percpu_ref_kill(&blkg->refcnt);
417 * blkg_destroy_all - destroy all blkgs associated with a request_queue
418 * @q: request_queue of interest
420 * Destroy all blkgs associated with @q.
422 static void blkg_destroy_all(struct request_queue *q)
424 struct blkcg_gq *blkg, *n;
426 spin_lock_irq(&q->queue_lock);
427 list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
428 struct blkcg *blkcg = blkg->blkcg;
430 spin_lock(&blkcg->lock);
432 spin_unlock(&blkcg->lock);
436 spin_unlock_irq(&q->queue_lock);
439 static int blkcg_reset_stats(struct cgroup_subsys_state *css,
440 struct cftype *cftype, u64 val)
442 struct blkcg *blkcg = css_to_blkcg(css);
443 struct blkcg_gq *blkg;
446 mutex_lock(&blkcg_pol_mutex);
447 spin_lock_irq(&blkcg->lock);
450 * Note that stat reset is racy - it doesn't synchronize against
451 * stat updates. This is a debug feature which shouldn't exist
452 * anyway. If you get hit by a race, retry.
454 hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
455 for_each_possible_cpu(cpu) {
456 struct blkg_iostat_set *bis =
457 per_cpu_ptr(blkg->iostat_cpu, cpu);
458 memset(bis, 0, sizeof(*bis));
460 memset(&blkg->iostat, 0, sizeof(blkg->iostat));
462 for (i = 0; i < BLKCG_MAX_POLS; i++) {
463 struct blkcg_policy *pol = blkcg_policy[i];
465 if (blkg->pd[i] && pol->pd_reset_stats_fn)
466 pol->pd_reset_stats_fn(blkg->pd[i]);
470 spin_unlock_irq(&blkcg->lock);
471 mutex_unlock(&blkcg_pol_mutex);
475 const char *blkg_dev_name(struct blkcg_gq *blkg)
477 /* some drivers (floppy) instantiate a queue w/o disk registered */
478 if (blkg->q->backing_dev_info->dev)
479 return bdi_dev_name(blkg->q->backing_dev_info);
484 * blkcg_print_blkgs - helper for printing per-blkg data
485 * @sf: seq_file to print to
486 * @blkcg: blkcg of interest
487 * @prfill: fill function to print out a blkg
488 * @pol: policy in question
489 * @data: data to be passed to @prfill
490 * @show_total: to print out sum of prfill return values or not
492 * This function invokes @prfill on each blkg of @blkcg if pd for the
493 * policy specified by @pol exists. @prfill is invoked with @sf, the
494 * policy data and @data and the matching queue lock held. If @show_total
495 * is %true, the sum of the return values from @prfill is printed with
496 * "Total" label at the end.
498 * This is to be used to construct print functions for
499 * cftype->read_seq_string method.
501 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
502 u64 (*prfill)(struct seq_file *,
503 struct blkg_policy_data *, int),
504 const struct blkcg_policy *pol, int data,
507 struct blkcg_gq *blkg;
511 hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
512 spin_lock_irq(&blkg->q->queue_lock);
513 if (blkcg_policy_enabled(blkg->q, pol))
514 total += prfill(sf, blkg->pd[pol->plid], data);
515 spin_unlock_irq(&blkg->q->queue_lock);
520 seq_printf(sf, "Total %llu\n", (unsigned long long)total);
522 EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
525 * __blkg_prfill_u64 - prfill helper for a single u64 value
526 * @sf: seq_file to print to
527 * @pd: policy private data of interest
530 * Print @v to @sf for the device assocaited with @pd.
532 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
534 const char *dname = blkg_dev_name(pd->blkg);
539 seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
542 EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
544 /* Performs queue bypass and policy enabled checks then looks up blkg. */
545 static struct blkcg_gq *blkg_lookup_check(struct blkcg *blkcg,
546 const struct blkcg_policy *pol,
547 struct request_queue *q)
549 WARN_ON_ONCE(!rcu_read_lock_held());
550 lockdep_assert_held(&q->queue_lock);
552 if (!blkcg_policy_enabled(q, pol))
553 return ERR_PTR(-EOPNOTSUPP);
554 return __blkg_lookup(blkcg, q, true /* update_hint */);
558 * blkcg_conf_open_bdev - parse and open bdev for per-blkg config update
559 * @inputp: input string pointer
561 * Parse the device node prefix part, MAJ:MIN, of per-blkg config update
562 * from @input and get and return the matching bdev. *@inputp is
563 * updated to point past the device node prefix. Returns an ERR_PTR()
566 * Use this function iff blkg_conf_prep() can't be used for some reason.
568 struct block_device *blkcg_conf_open_bdev(char **inputp)
570 char *input = *inputp;
571 unsigned int major, minor;
572 struct block_device *bdev;
575 if (sscanf(input, "%u:%u%n", &major, &minor, &key_len) != 2)
576 return ERR_PTR(-EINVAL);
579 if (!isspace(*input))
580 return ERR_PTR(-EINVAL);
581 input = skip_spaces(input);
583 bdev = blkdev_get_no_open(MKDEV(major, minor));
585 return ERR_PTR(-ENODEV);
586 if (bdev_is_partition(bdev)) {
587 blkdev_put_no_open(bdev);
588 return ERR_PTR(-ENODEV);
596 * blkg_conf_prep - parse and prepare for per-blkg config update
597 * @blkcg: target block cgroup
598 * @pol: target policy
599 * @input: input string
600 * @ctx: blkg_conf_ctx to be filled
602 * Parse per-blkg config update from @input and initialize @ctx with the
603 * result. @ctx->blkg points to the blkg to be updated and @ctx->body the
604 * part of @input following MAJ:MIN. This function returns with RCU read
605 * lock and queue lock held and must be paired with blkg_conf_finish().
607 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
608 char *input, struct blkg_conf_ctx *ctx)
609 __acquires(rcu) __acquires(&bdev->bd_disk->queue->queue_lock)
611 struct block_device *bdev;
612 struct request_queue *q;
613 struct blkcg_gq *blkg;
616 bdev = blkcg_conf_open_bdev(&input);
618 return PTR_ERR(bdev);
620 q = bdev->bd_disk->queue;
623 spin_lock_irq(&q->queue_lock);
625 blkg = blkg_lookup_check(blkcg, pol, q);
635 * Create blkgs walking down from blkcg_root to @blkcg, so that all
636 * non-root blkgs have access to their parents.
639 struct blkcg *pos = blkcg;
640 struct blkcg *parent;
641 struct blkcg_gq *new_blkg;
643 parent = blkcg_parent(blkcg);
644 while (parent && !__blkg_lookup(parent, q, false)) {
646 parent = blkcg_parent(parent);
649 /* Drop locks to do new blkg allocation with GFP_KERNEL. */
650 spin_unlock_irq(&q->queue_lock);
653 new_blkg = blkg_alloc(pos, q, GFP_KERNEL);
654 if (unlikely(!new_blkg)) {
659 if (radix_tree_preload(GFP_KERNEL)) {
666 spin_lock_irq(&q->queue_lock);
668 blkg = blkg_lookup_check(pos, pol, q);
678 blkg = blkg_create(pos, q, new_blkg);
685 radix_tree_preload_end();
697 radix_tree_preload_end();
699 spin_unlock_irq(&q->queue_lock);
702 blkdev_put_no_open(bdev);
704 * If queue was bypassing, we should retry. Do so after a
705 * short msleep(). It isn't strictly necessary but queue
706 * can be bypassing for some time and it's always nice to
707 * avoid busy looping.
711 ret = restart_syscall();
715 EXPORT_SYMBOL_GPL(blkg_conf_prep);
718 * blkg_conf_finish - finish up per-blkg config update
719 * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
721 * Finish up after per-blkg config update. This function must be paired
722 * with blkg_conf_prep().
724 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
725 __releases(&ctx->bdev->bd_disk->queue->queue_lock) __releases(rcu)
727 spin_unlock_irq(&ctx->bdev->bd_disk->queue->queue_lock);
729 blkdev_put_no_open(ctx->bdev);
731 EXPORT_SYMBOL_GPL(blkg_conf_finish);
733 static void blkg_iostat_set(struct blkg_iostat *dst, struct blkg_iostat *src)
737 for (i = 0; i < BLKG_IOSTAT_NR; i++) {
738 dst->bytes[i] = src->bytes[i];
739 dst->ios[i] = src->ios[i];
743 static void blkg_iostat_add(struct blkg_iostat *dst, struct blkg_iostat *src)
747 for (i = 0; i < BLKG_IOSTAT_NR; i++) {
748 dst->bytes[i] += src->bytes[i];
749 dst->ios[i] += src->ios[i];
753 static void blkg_iostat_sub(struct blkg_iostat *dst, struct blkg_iostat *src)
757 for (i = 0; i < BLKG_IOSTAT_NR; i++) {
758 dst->bytes[i] -= src->bytes[i];
759 dst->ios[i] -= src->ios[i];
763 static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu)
765 struct blkcg *blkcg = css_to_blkcg(css);
766 struct blkcg_gq *blkg;
768 /* Root-level stats are sourced from system-wide IO stats */
769 if (!cgroup_parent(css->cgroup))
774 hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
775 struct blkcg_gq *parent = blkg->parent;
776 struct blkg_iostat_set *bisc = per_cpu_ptr(blkg->iostat_cpu, cpu);
777 struct blkg_iostat cur, delta;
780 /* fetch the current per-cpu values */
782 seq = u64_stats_fetch_begin(&bisc->sync);
783 blkg_iostat_set(&cur, &bisc->cur);
784 } while (u64_stats_fetch_retry(&bisc->sync, seq));
786 /* propagate percpu delta to global */
787 u64_stats_update_begin(&blkg->iostat.sync);
788 blkg_iostat_set(&delta, &cur);
789 blkg_iostat_sub(&delta, &bisc->last);
790 blkg_iostat_add(&blkg->iostat.cur, &delta);
791 blkg_iostat_add(&bisc->last, &delta);
792 u64_stats_update_end(&blkg->iostat.sync);
794 /* propagate global delta to parent (unless that's root) */
795 if (parent && parent->parent) {
796 u64_stats_update_begin(&parent->iostat.sync);
797 blkg_iostat_set(&delta, &blkg->iostat.cur);
798 blkg_iostat_sub(&delta, &blkg->iostat.last);
799 blkg_iostat_add(&parent->iostat.cur, &delta);
800 blkg_iostat_add(&blkg->iostat.last, &delta);
801 u64_stats_update_end(&parent->iostat.sync);
809 * We source root cgroup stats from the system-wide stats to avoid
810 * tracking the same information twice and incurring overhead when no
811 * cgroups are defined. For that reason, cgroup_rstat_flush in
812 * blkcg_print_stat does not actually fill out the iostat in the root
815 * However, we would like to re-use the printing code between the root and
816 * non-root cgroups to the extent possible. For that reason, we simulate
817 * flushing the root cgroup's stats by explicitly filling in the iostat
818 * with disk level statistics.
820 static void blkcg_fill_root_iostats(void)
822 struct class_dev_iter iter;
825 class_dev_iter_init(&iter, &block_class, NULL, &disk_type);
826 while ((dev = class_dev_iter_next(&iter))) {
827 struct block_device *bdev = dev_to_bdev(dev);
828 struct blkcg_gq *blkg =
829 blk_queue_root_blkg(bdev->bd_disk->queue);
830 struct blkg_iostat tmp;
833 memset(&tmp, 0, sizeof(tmp));
834 for_each_possible_cpu(cpu) {
835 struct disk_stats *cpu_dkstats;
837 cpu_dkstats = per_cpu_ptr(bdev->bd_stats, cpu);
838 tmp.ios[BLKG_IOSTAT_READ] +=
839 cpu_dkstats->ios[STAT_READ];
840 tmp.ios[BLKG_IOSTAT_WRITE] +=
841 cpu_dkstats->ios[STAT_WRITE];
842 tmp.ios[BLKG_IOSTAT_DISCARD] +=
843 cpu_dkstats->ios[STAT_DISCARD];
844 // convert sectors to bytes
845 tmp.bytes[BLKG_IOSTAT_READ] +=
846 cpu_dkstats->sectors[STAT_READ] << 9;
847 tmp.bytes[BLKG_IOSTAT_WRITE] +=
848 cpu_dkstats->sectors[STAT_WRITE] << 9;
849 tmp.bytes[BLKG_IOSTAT_DISCARD] +=
850 cpu_dkstats->sectors[STAT_DISCARD] << 9;
852 u64_stats_update_begin(&blkg->iostat.sync);
853 blkg_iostat_set(&blkg->iostat.cur, &tmp);
854 u64_stats_update_end(&blkg->iostat.sync);
859 static int blkcg_print_stat(struct seq_file *sf, void *v)
861 struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
862 struct blkcg_gq *blkg;
864 if (!seq_css(sf)->parent)
865 blkcg_fill_root_iostats();
867 cgroup_rstat_flush(blkcg->css.cgroup);
871 hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
872 struct blkg_iostat_set *bis = &blkg->iostat;
875 u64 rbytes, wbytes, rios, wios, dbytes, dios;
876 size_t size = seq_get_buf(sf, &buf), off = 0;
878 bool has_stats = false;
881 spin_lock_irq(&blkg->q->queue_lock);
886 dname = blkg_dev_name(blkg);
891 * Hooray string manipulation, count is the size written NOT
892 * INCLUDING THE \0, so size is now count+1 less than what we
893 * had before, but we want to start writing the next bit from
894 * the \0 so we only add count to buf.
896 off += scnprintf(buf+off, size-off, "%s ", dname);
899 seq = u64_stats_fetch_begin(&bis->sync);
901 rbytes = bis->cur.bytes[BLKG_IOSTAT_READ];
902 wbytes = bis->cur.bytes[BLKG_IOSTAT_WRITE];
903 dbytes = bis->cur.bytes[BLKG_IOSTAT_DISCARD];
904 rios = bis->cur.ios[BLKG_IOSTAT_READ];
905 wios = bis->cur.ios[BLKG_IOSTAT_WRITE];
906 dios = bis->cur.ios[BLKG_IOSTAT_DISCARD];
907 } while (u64_stats_fetch_retry(&bis->sync, seq));
909 if (rbytes || wbytes || rios || wios) {
911 off += scnprintf(buf+off, size-off,
912 "rbytes=%llu wbytes=%llu rios=%llu wios=%llu dbytes=%llu dios=%llu",
913 rbytes, wbytes, rios, wios,
917 if (blkcg_debug_stats && atomic_read(&blkg->use_delay)) {
919 off += scnprintf(buf+off, size-off,
920 " use_delay=%d delay_nsec=%llu",
921 atomic_read(&blkg->use_delay),
922 (unsigned long long)atomic64_read(&blkg->delay_nsec));
925 for (i = 0; i < BLKCG_MAX_POLS; i++) {
926 struct blkcg_policy *pol = blkcg_policy[i];
929 if (!blkg->pd[i] || !pol->pd_stat_fn)
932 written = pol->pd_stat_fn(blkg->pd[i], buf+off, size-off);
939 if (off < size - 1) {
940 off += scnprintf(buf+off, size-off, "\n");
947 spin_unlock_irq(&blkg->q->queue_lock);
954 static struct cftype blkcg_files[] = {
957 .seq_show = blkcg_print_stat,
962 static struct cftype blkcg_legacy_files[] = {
964 .name = "reset_stats",
965 .write_u64 = blkcg_reset_stats,
971 * blkcg destruction is a three-stage process.
973 * 1. Destruction starts. The blkcg_css_offline() callback is invoked
974 * which offlines writeback. Here we tie the next stage of blkg destruction
975 * to the completion of writeback associated with the blkcg. This lets us
976 * avoid punting potentially large amounts of outstanding writeback to root
977 * while maintaining any ongoing policies. The next stage is triggered when
978 * the nr_cgwbs count goes to zero.
980 * 2. When the nr_cgwbs count goes to zero, blkcg_destroy_blkgs() is called
981 * and handles the destruction of blkgs. Here the css reference held by
982 * the blkg is put back eventually allowing blkcg_css_free() to be called.
983 * This work may occur in cgwb_release_workfn() on the cgwb_release
984 * workqueue. Any submitted ios that fail to get the blkg ref will be
985 * punted to the root_blkg.
987 * 3. Once the blkcg ref count goes to zero, blkcg_css_free() is called.
988 * This finally frees the blkcg.
992 * blkcg_css_offline - cgroup css_offline callback
993 * @css: css of interest
995 * This function is called when @css is about to go away. Here the cgwbs are
996 * offlined first and only once writeback associated with the blkcg has
997 * finished do we start step 2 (see above).
999 static void blkcg_css_offline(struct cgroup_subsys_state *css)
1001 struct blkcg *blkcg = css_to_blkcg(css);
1003 /* this prevents anyone from attaching or migrating to this blkcg */
1004 wb_blkcg_offline(blkcg);
1006 /* put the base online pin allowing step 2 to be triggered */
1007 blkcg_unpin_online(blkcg);
1011 * blkcg_destroy_blkgs - responsible for shooting down blkgs
1012 * @blkcg: blkcg of interest
1014 * blkgs should be removed while holding both q and blkcg locks. As blkcg lock
1015 * is nested inside q lock, this function performs reverse double lock dancing.
1016 * Destroying the blkgs releases the reference held on the blkcg's css allowing
1017 * blkcg_css_free to eventually be called.
1019 * This is the blkcg counterpart of ioc_release_fn().
1021 void blkcg_destroy_blkgs(struct blkcg *blkcg)
1025 spin_lock_irq(&blkcg->lock);
1027 while (!hlist_empty(&blkcg->blkg_list)) {
1028 struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
1029 struct blkcg_gq, blkcg_node);
1030 struct request_queue *q = blkg->q;
1032 if (need_resched() || !spin_trylock(&q->queue_lock)) {
1034 * Given that the system can accumulate a huge number
1035 * of blkgs in pathological cases, check to see if we
1036 * need to rescheduling to avoid softlockup.
1038 spin_unlock_irq(&blkcg->lock);
1040 spin_lock_irq(&blkcg->lock);
1045 spin_unlock(&q->queue_lock);
1048 spin_unlock_irq(&blkcg->lock);
1051 static void blkcg_css_free(struct cgroup_subsys_state *css)
1053 struct blkcg *blkcg = css_to_blkcg(css);
1056 mutex_lock(&blkcg_pol_mutex);
1058 list_del(&blkcg->all_blkcgs_node);
1060 for (i = 0; i < BLKCG_MAX_POLS; i++)
1062 blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
1064 mutex_unlock(&blkcg_pol_mutex);
1069 static struct cgroup_subsys_state *
1070 blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
1072 struct blkcg *blkcg;
1073 struct cgroup_subsys_state *ret;
1076 mutex_lock(&blkcg_pol_mutex);
1079 blkcg = &blkcg_root;
1081 blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
1083 ret = ERR_PTR(-ENOMEM);
1088 for (i = 0; i < BLKCG_MAX_POLS ; i++) {
1089 struct blkcg_policy *pol = blkcg_policy[i];
1090 struct blkcg_policy_data *cpd;
1093 * If the policy hasn't been attached yet, wait for it
1094 * to be attached before doing anything else. Otherwise,
1095 * check if the policy requires any specific per-cgroup
1096 * data: if it does, allocate and initialize it.
1098 if (!pol || !pol->cpd_alloc_fn)
1101 cpd = pol->cpd_alloc_fn(GFP_KERNEL);
1103 ret = ERR_PTR(-ENOMEM);
1106 blkcg->cpd[i] = cpd;
1109 if (pol->cpd_init_fn)
1110 pol->cpd_init_fn(cpd);
1113 spin_lock_init(&blkcg->lock);
1114 refcount_set(&blkcg->online_pin, 1);
1115 INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT | __GFP_NOWARN);
1116 INIT_HLIST_HEAD(&blkcg->blkg_list);
1117 #ifdef CONFIG_CGROUP_WRITEBACK
1118 INIT_LIST_HEAD(&blkcg->cgwb_list);
1120 list_add_tail(&blkcg->all_blkcgs_node, &all_blkcgs);
1122 mutex_unlock(&blkcg_pol_mutex);
1126 for (i--; i >= 0; i--)
1128 blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
1130 if (blkcg != &blkcg_root)
1133 mutex_unlock(&blkcg_pol_mutex);
1137 static int blkcg_css_online(struct cgroup_subsys_state *css)
1139 struct blkcg *blkcg = css_to_blkcg(css);
1140 struct blkcg *parent = blkcg_parent(blkcg);
1143 * blkcg_pin_online() is used to delay blkcg offline so that blkgs
1144 * don't go offline while cgwbs are still active on them. Pin the
1145 * parent so that offline always happens towards the root.
1148 blkcg_pin_online(parent);
1153 * blkcg_init_queue - initialize blkcg part of request queue
1154 * @q: request_queue to initialize
1156 * Called from blk_alloc_queue(). Responsible for initializing blkcg
1157 * part of new request_queue @q.
1160 * 0 on success, -errno on failure.
1162 int blkcg_init_queue(struct request_queue *q)
1164 struct blkcg_gq *new_blkg, *blkg;
1168 new_blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
1172 preloaded = !radix_tree_preload(GFP_KERNEL);
1174 /* Make sure the root blkg exists. */
1176 spin_lock_irq(&q->queue_lock);
1177 blkg = blkg_create(&blkcg_root, q, new_blkg);
1180 q->root_blkg = blkg;
1181 spin_unlock_irq(&q->queue_lock);
1185 radix_tree_preload_end();
1187 ret = blk_iolatency_init(q);
1189 goto err_destroy_all;
1191 ret = blk_ioprio_init(q);
1193 goto err_destroy_all;
1195 ret = blk_throtl_init(q);
1197 goto err_destroy_all;
1202 blkg_destroy_all(q);
1205 spin_unlock_irq(&q->queue_lock);
1208 radix_tree_preload_end();
1209 return PTR_ERR(blkg);
1213 * blkcg_exit_queue - exit and release blkcg part of request_queue
1214 * @q: request_queue being released
1216 * Called from blk_exit_queue(). Responsible for exiting blkcg part.
1218 void blkcg_exit_queue(struct request_queue *q)
1220 blkg_destroy_all(q);
1224 static void blkcg_bind(struct cgroup_subsys_state *root_css)
1228 mutex_lock(&blkcg_pol_mutex);
1230 for (i = 0; i < BLKCG_MAX_POLS; i++) {
1231 struct blkcg_policy *pol = blkcg_policy[i];
1232 struct blkcg *blkcg;
1234 if (!pol || !pol->cpd_bind_fn)
1237 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node)
1238 if (blkcg->cpd[pol->plid])
1239 pol->cpd_bind_fn(blkcg->cpd[pol->plid]);
1241 mutex_unlock(&blkcg_pol_mutex);
1244 static void blkcg_exit(struct task_struct *tsk)
1246 if (tsk->throttle_queue)
1247 blk_put_queue(tsk->throttle_queue);
1248 tsk->throttle_queue = NULL;
1251 struct cgroup_subsys io_cgrp_subsys = {
1252 .css_alloc = blkcg_css_alloc,
1253 .css_online = blkcg_css_online,
1254 .css_offline = blkcg_css_offline,
1255 .css_free = blkcg_css_free,
1256 .css_rstat_flush = blkcg_rstat_flush,
1258 .dfl_cftypes = blkcg_files,
1259 .legacy_cftypes = blkcg_legacy_files,
1260 .legacy_name = "blkio",
1264 * This ensures that, if available, memcg is automatically enabled
1265 * together on the default hierarchy so that the owner cgroup can
1266 * be retrieved from writeback pages.
1268 .depends_on = 1 << memory_cgrp_id,
1271 EXPORT_SYMBOL_GPL(io_cgrp_subsys);
1274 * blkcg_activate_policy - activate a blkcg policy on a request_queue
1275 * @q: request_queue of interest
1276 * @pol: blkcg policy to activate
1278 * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through
1279 * bypass mode to populate its blkgs with policy_data for @pol.
1281 * Activation happens with @q bypassed, so nobody would be accessing blkgs
1282 * from IO path. Update of each blkg is protected by both queue and blkcg
1283 * locks so that holding either lock and testing blkcg_policy_enabled() is
1284 * always enough for dereferencing policy data.
1286 * The caller is responsible for synchronizing [de]activations and policy
1287 * [un]registerations. Returns 0 on success, -errno on failure.
1289 int blkcg_activate_policy(struct request_queue *q,
1290 const struct blkcg_policy *pol)
1292 struct blkg_policy_data *pd_prealloc = NULL;
1293 struct blkcg_gq *blkg, *pinned_blkg = NULL;
1296 if (blkcg_policy_enabled(q, pol))
1300 blk_mq_freeze_queue(q);
1302 spin_lock_irq(&q->queue_lock);
1304 /* blkg_list is pushed at the head, reverse walk to allocate parents first */
1305 list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) {
1306 struct blkg_policy_data *pd;
1308 if (blkg->pd[pol->plid])
1311 /* If prealloc matches, use it; otherwise try GFP_NOWAIT */
1312 if (blkg == pinned_blkg) {
1316 pd = pol->pd_alloc_fn(GFP_NOWAIT | __GFP_NOWARN, q,
1322 * GFP_NOWAIT failed. Free the existing one and
1323 * prealloc for @blkg w/ GFP_KERNEL.
1326 blkg_put(pinned_blkg);
1330 spin_unlock_irq(&q->queue_lock);
1333 pol->pd_free_fn(pd_prealloc);
1334 pd_prealloc = pol->pd_alloc_fn(GFP_KERNEL, q,
1342 blkg->pd[pol->plid] = pd;
1344 pd->plid = pol->plid;
1347 /* all allocated, init in the same order */
1348 if (pol->pd_init_fn)
1349 list_for_each_entry_reverse(blkg, &q->blkg_list, q_node)
1350 pol->pd_init_fn(blkg->pd[pol->plid]);
1352 __set_bit(pol->plid, q->blkcg_pols);
1355 spin_unlock_irq(&q->queue_lock);
1358 blk_mq_unfreeze_queue(q);
1360 blkg_put(pinned_blkg);
1362 pol->pd_free_fn(pd_prealloc);
1366 /* alloc failed, nothing's initialized yet, free everything */
1367 spin_lock_irq(&q->queue_lock);
1368 list_for_each_entry(blkg, &q->blkg_list, q_node) {
1369 if (blkg->pd[pol->plid]) {
1370 pol->pd_free_fn(blkg->pd[pol->plid]);
1371 blkg->pd[pol->plid] = NULL;
1374 spin_unlock_irq(&q->queue_lock);
1378 EXPORT_SYMBOL_GPL(blkcg_activate_policy);
1381 * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
1382 * @q: request_queue of interest
1383 * @pol: blkcg policy to deactivate
1385 * Deactivate @pol on @q. Follows the same synchronization rules as
1386 * blkcg_activate_policy().
1388 void blkcg_deactivate_policy(struct request_queue *q,
1389 const struct blkcg_policy *pol)
1391 struct blkcg_gq *blkg;
1393 if (!blkcg_policy_enabled(q, pol))
1397 blk_mq_freeze_queue(q);
1399 spin_lock_irq(&q->queue_lock);
1401 __clear_bit(pol->plid, q->blkcg_pols);
1403 list_for_each_entry(blkg, &q->blkg_list, q_node) {
1404 if (blkg->pd[pol->plid]) {
1405 if (pol->pd_offline_fn)
1406 pol->pd_offline_fn(blkg->pd[pol->plid]);
1407 pol->pd_free_fn(blkg->pd[pol->plid]);
1408 blkg->pd[pol->plid] = NULL;
1412 spin_unlock_irq(&q->queue_lock);
1415 blk_mq_unfreeze_queue(q);
1417 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
1420 * blkcg_policy_register - register a blkcg policy
1421 * @pol: blkcg policy to register
1423 * Register @pol with blkcg core. Might sleep and @pol may be modified on
1424 * successful registration. Returns 0 on success and -errno on failure.
1426 int blkcg_policy_register(struct blkcg_policy *pol)
1428 struct blkcg *blkcg;
1431 mutex_lock(&blkcg_pol_register_mutex);
1432 mutex_lock(&blkcg_pol_mutex);
1434 /* find an empty slot */
1436 for (i = 0; i < BLKCG_MAX_POLS; i++)
1437 if (!blkcg_policy[i])
1439 if (i >= BLKCG_MAX_POLS) {
1440 pr_warn("blkcg_policy_register: BLKCG_MAX_POLS too small\n");
1444 /* Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs */
1445 if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) ||
1446 (!pol->pd_alloc_fn ^ !pol->pd_free_fn))
1451 blkcg_policy[pol->plid] = pol;
1453 /* allocate and install cpd's */
1454 if (pol->cpd_alloc_fn) {
1455 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1456 struct blkcg_policy_data *cpd;
1458 cpd = pol->cpd_alloc_fn(GFP_KERNEL);
1462 blkcg->cpd[pol->plid] = cpd;
1464 cpd->plid = pol->plid;
1465 if (pol->cpd_init_fn)
1466 pol->cpd_init_fn(cpd);
1470 mutex_unlock(&blkcg_pol_mutex);
1472 /* everything is in place, add intf files for the new policy */
1473 if (pol->dfl_cftypes)
1474 WARN_ON(cgroup_add_dfl_cftypes(&io_cgrp_subsys,
1476 if (pol->legacy_cftypes)
1477 WARN_ON(cgroup_add_legacy_cftypes(&io_cgrp_subsys,
1478 pol->legacy_cftypes));
1479 mutex_unlock(&blkcg_pol_register_mutex);
1483 if (pol->cpd_free_fn) {
1484 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1485 if (blkcg->cpd[pol->plid]) {
1486 pol->cpd_free_fn(blkcg->cpd[pol->plid]);
1487 blkcg->cpd[pol->plid] = NULL;
1491 blkcg_policy[pol->plid] = NULL;
1493 mutex_unlock(&blkcg_pol_mutex);
1494 mutex_unlock(&blkcg_pol_register_mutex);
1497 EXPORT_SYMBOL_GPL(blkcg_policy_register);
1500 * blkcg_policy_unregister - unregister a blkcg policy
1501 * @pol: blkcg policy to unregister
1503 * Undo blkcg_policy_register(@pol). Might sleep.
1505 void blkcg_policy_unregister(struct blkcg_policy *pol)
1507 struct blkcg *blkcg;
1509 mutex_lock(&blkcg_pol_register_mutex);
1511 if (WARN_ON(blkcg_policy[pol->plid] != pol))
1514 /* kill the intf files first */
1515 if (pol->dfl_cftypes)
1516 cgroup_rm_cftypes(pol->dfl_cftypes);
1517 if (pol->legacy_cftypes)
1518 cgroup_rm_cftypes(pol->legacy_cftypes);
1520 /* remove cpds and unregister */
1521 mutex_lock(&blkcg_pol_mutex);
1523 if (pol->cpd_free_fn) {
1524 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1525 if (blkcg->cpd[pol->plid]) {
1526 pol->cpd_free_fn(blkcg->cpd[pol->plid]);
1527 blkcg->cpd[pol->plid] = NULL;
1531 blkcg_policy[pol->plid] = NULL;
1533 mutex_unlock(&blkcg_pol_mutex);
1535 mutex_unlock(&blkcg_pol_register_mutex);
1537 EXPORT_SYMBOL_GPL(blkcg_policy_unregister);
1539 bool __blkcg_punt_bio_submit(struct bio *bio)
1541 struct blkcg_gq *blkg = bio->bi_blkg;
1543 /* consume the flag first */
1544 bio->bi_opf &= ~REQ_CGROUP_PUNT;
1546 /* never bounce for the root cgroup */
1550 spin_lock_bh(&blkg->async_bio_lock);
1551 bio_list_add(&blkg->async_bios, bio);
1552 spin_unlock_bh(&blkg->async_bio_lock);
1554 queue_work(blkcg_punt_bio_wq, &blkg->async_bio_work);
1559 * Scale the accumulated delay based on how long it has been since we updated
1560 * the delay. We only call this when we are adding delay, in case it's been a
1561 * while since we added delay, and when we are checking to see if we need to
1562 * delay a task, to account for any delays that may have occurred.
1564 static void blkcg_scale_delay(struct blkcg_gq *blkg, u64 now)
1566 u64 old = atomic64_read(&blkg->delay_start);
1568 /* negative use_delay means no scaling, see blkcg_set_delay() */
1569 if (atomic_read(&blkg->use_delay) < 0)
1573 * We only want to scale down every second. The idea here is that we
1574 * want to delay people for min(delay_nsec, NSEC_PER_SEC) in a certain
1575 * time window. We only want to throttle tasks for recent delay that
1576 * has occurred, in 1 second time windows since that's the maximum
1577 * things can be throttled. We save the current delay window in
1578 * blkg->last_delay so we know what amount is still left to be charged
1579 * to the blkg from this point onward. blkg->last_use keeps track of
1580 * the use_delay counter. The idea is if we're unthrottling the blkg we
1581 * are ok with whatever is happening now, and we can take away more of
1582 * the accumulated delay as we've already throttled enough that
1583 * everybody is happy with their IO latencies.
1585 if (time_before64(old + NSEC_PER_SEC, now) &&
1586 atomic64_cmpxchg(&blkg->delay_start, old, now) == old) {
1587 u64 cur = atomic64_read(&blkg->delay_nsec);
1588 u64 sub = min_t(u64, blkg->last_delay, now - old);
1589 int cur_use = atomic_read(&blkg->use_delay);
1592 * We've been unthrottled, subtract a larger chunk of our
1593 * accumulated delay.
1595 if (cur_use < blkg->last_use)
1596 sub = max_t(u64, sub, blkg->last_delay >> 1);
1599 * This shouldn't happen, but handle it anyway. Our delay_nsec
1600 * should only ever be growing except here where we subtract out
1601 * min(last_delay, 1 second), but lord knows bugs happen and I'd
1602 * rather not end up with negative numbers.
1604 if (unlikely(cur < sub)) {
1605 atomic64_set(&blkg->delay_nsec, 0);
1606 blkg->last_delay = 0;
1608 atomic64_sub(sub, &blkg->delay_nsec);
1609 blkg->last_delay = cur - sub;
1611 blkg->last_use = cur_use;
1616 * This is called when we want to actually walk up the hierarchy and check to
1617 * see if we need to throttle, and then actually throttle if there is some
1618 * accumulated delay. This should only be called upon return to user space so
1619 * we're not holding some lock that would induce a priority inversion.
1621 static void blkcg_maybe_throttle_blkg(struct blkcg_gq *blkg, bool use_memdelay)
1623 unsigned long pflags;
1625 u64 now = ktime_to_ns(ktime_get());
1630 while (blkg->parent) {
1631 int use_delay = atomic_read(&blkg->use_delay);
1636 blkcg_scale_delay(blkg, now);
1637 this_delay = atomic64_read(&blkg->delay_nsec);
1638 if (this_delay > delay_nsec) {
1639 delay_nsec = this_delay;
1640 clamp = use_delay > 0;
1643 blkg = blkg->parent;
1650 * Let's not sleep for all eternity if we've amassed a huge delay.
1651 * Swapping or metadata IO can accumulate 10's of seconds worth of
1652 * delay, and we want userspace to be able to do _something_ so cap the
1653 * delays at 0.25s. If there's 10's of seconds worth of delay then the
1654 * tasks will be delayed for 0.25 second for every syscall. If
1655 * blkcg_set_delay() was used as indicated by negative use_delay, the
1656 * caller is responsible for regulating the range.
1659 delay_nsec = min_t(u64, delay_nsec, 250 * NSEC_PER_MSEC);
1662 psi_memstall_enter(&pflags);
1664 exp = ktime_add_ns(now, delay_nsec);
1665 tok = io_schedule_prepare();
1667 __set_current_state(TASK_KILLABLE);
1668 if (!schedule_hrtimeout(&exp, HRTIMER_MODE_ABS))
1670 } while (!fatal_signal_pending(current));
1671 io_schedule_finish(tok);
1674 psi_memstall_leave(&pflags);
1678 * blkcg_maybe_throttle_current - throttle the current task if it has been marked
1680 * This is only called if we've been marked with set_notify_resume(). Obviously
1681 * we can be set_notify_resume() for reasons other than blkcg throttling, so we
1682 * check to see if current->throttle_queue is set and if not this doesn't do
1683 * anything. This should only ever be called by the resume code, it's not meant
1684 * to be called by people willy-nilly as it will actually do the work to
1685 * throttle the task if it is setup for throttling.
1687 void blkcg_maybe_throttle_current(void)
1689 struct request_queue *q = current->throttle_queue;
1690 struct cgroup_subsys_state *css;
1691 struct blkcg *blkcg;
1692 struct blkcg_gq *blkg;
1693 bool use_memdelay = current->use_memdelay;
1698 current->throttle_queue = NULL;
1699 current->use_memdelay = false;
1702 css = kthread_blkcg();
1704 blkcg = css_to_blkcg(css);
1706 blkcg = css_to_blkcg(task_css(current, io_cgrp_id));
1710 blkg = blkg_lookup(blkcg, q);
1713 if (!blkg_tryget(blkg))
1717 blkcg_maybe_throttle_blkg(blkg, use_memdelay);
1727 * blkcg_schedule_throttle - this task needs to check for throttling
1728 * @q: the request queue IO was submitted on
1729 * @use_memdelay: do we charge this to memory delay for PSI
1731 * This is called by the IO controller when we know there's delay accumulated
1732 * for the blkg for this task. We do not pass the blkg because there are places
1733 * we call this that may not have that information, the swapping code for
1734 * instance will only have a request_queue at that point. This set's the
1735 * notify_resume for the task to check and see if it requires throttling before
1736 * returning to user space.
1738 * We will only schedule once per syscall. You can call this over and over
1739 * again and it will only do the check once upon return to user space, and only
1740 * throttle once. If the task needs to be throttled again it'll need to be
1741 * re-set at the next time we see the task.
1743 void blkcg_schedule_throttle(struct request_queue *q, bool use_memdelay)
1745 if (unlikely(current->flags & PF_KTHREAD))
1748 if (current->throttle_queue != q) {
1749 if (!blk_get_queue(q))
1752 if (current->throttle_queue)
1753 blk_put_queue(current->throttle_queue);
1754 current->throttle_queue = q;
1758 current->use_memdelay = use_memdelay;
1759 set_notify_resume(current);
1763 * blkcg_add_delay - add delay to this blkg
1764 * @blkg: blkg of interest
1765 * @now: the current time in nanoseconds
1766 * @delta: how many nanoseconds of delay to add
1768 * Charge @delta to the blkg's current delay accumulation. This is used to
1769 * throttle tasks if an IO controller thinks we need more throttling.
1771 void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta)
1773 if (WARN_ON_ONCE(atomic_read(&blkg->use_delay) < 0))
1775 blkcg_scale_delay(blkg, now);
1776 atomic64_add(delta, &blkg->delay_nsec);
1780 * blkg_tryget_closest - try and get a blkg ref on the closet blkg
1784 * As the failure mode here is to walk up the blkg tree, this ensure that the
1785 * blkg->parent pointers are always valid. This returns the blkg that it ended
1786 * up taking a reference on or %NULL if no reference was taken.
1788 static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio,
1789 struct cgroup_subsys_state *css)
1791 struct blkcg_gq *blkg, *ret_blkg = NULL;
1794 blkg = blkg_lookup_create(css_to_blkcg(css),
1795 bio->bi_bdev->bd_disk->queue);
1797 if (blkg_tryget(blkg)) {
1801 blkg = blkg->parent;
1809 * bio_associate_blkg_from_css - associate a bio with a specified css
1813 * Associate @bio with the blkg found by combining the css's blkg and the
1814 * request_queue of the @bio. An association failure is handled by walking up
1815 * the blkg tree. Therefore, the blkg associated can be anything between @blkg
1816 * and q->root_blkg. This situation only happens when a cgroup is dying and
1817 * then the remaining bios will spill to the closest alive blkg.
1819 * A reference will be taken on the blkg and will be released when @bio is
1822 void bio_associate_blkg_from_css(struct bio *bio,
1823 struct cgroup_subsys_state *css)
1826 blkg_put(bio->bi_blkg);
1828 if (css && css->parent) {
1829 bio->bi_blkg = blkg_tryget_closest(bio, css);
1831 blkg_get(bio->bi_bdev->bd_disk->queue->root_blkg);
1832 bio->bi_blkg = bio->bi_bdev->bd_disk->queue->root_blkg;
1835 EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);
1838 * bio_associate_blkg - associate a bio with a blkg
1841 * Associate @bio with the blkg found from the bio's css and request_queue.
1842 * If one is not found, bio_lookup_blkg() creates the blkg. If a blkg is
1843 * already associated, the css is reused and association redone as the
1844 * request_queue may have changed.
1846 void bio_associate_blkg(struct bio *bio)
1848 struct cgroup_subsys_state *css;
1853 css = &bio_blkcg(bio)->css;
1857 bio_associate_blkg_from_css(bio, css);
1861 EXPORT_SYMBOL_GPL(bio_associate_blkg);
1864 * bio_clone_blkg_association - clone blkg association from src to dst bio
1865 * @dst: destination bio
1868 void bio_clone_blkg_association(struct bio *dst, struct bio *src)
1872 blkg_put(dst->bi_blkg);
1873 blkg_get(src->bi_blkg);
1874 dst->bi_blkg = src->bi_blkg;
1877 EXPORT_SYMBOL_GPL(bio_clone_blkg_association);
1879 static int blk_cgroup_io_type(struct bio *bio)
1881 if (op_is_discard(bio->bi_opf))
1882 return BLKG_IOSTAT_DISCARD;
1883 if (op_is_write(bio->bi_opf))
1884 return BLKG_IOSTAT_WRITE;
1885 return BLKG_IOSTAT_READ;
1888 void blk_cgroup_bio_start(struct bio *bio)
1890 int rwd = blk_cgroup_io_type(bio), cpu;
1891 struct blkg_iostat_set *bis;
1894 bis = per_cpu_ptr(bio->bi_blkg->iostat_cpu, cpu);
1895 u64_stats_update_begin(&bis->sync);
1898 * If the bio is flagged with BIO_CGROUP_ACCT it means this is a split
1899 * bio and we would have already accounted for the size of the bio.
1901 if (!bio_flagged(bio, BIO_CGROUP_ACCT)) {
1902 bio_set_flag(bio, BIO_CGROUP_ACCT);
1903 bis->cur.bytes[rwd] += bio->bi_iter.bi_size;
1905 bis->cur.ios[rwd]++;
1907 u64_stats_update_end(&bis->sync);
1908 if (cgroup_subsys_on_dfl(io_cgrp_subsys))
1909 cgroup_rstat_updated(bio->bi_blkg->blkcg->css.cgroup, cpu);
1913 static int __init blkcg_init(void)
1915 blkcg_punt_bio_wq = alloc_workqueue("blkcg_punt_bio",
1916 WQ_MEM_RECLAIM | WQ_FREEZABLE |
1917 WQ_UNBOUND | WQ_SYSFS, 0);
1918 if (!blkcg_punt_bio_wq)
1922 subsys_initcall(blkcg_init);
1924 module_param(blkcg_debug_stats, bool, 0644);
1925 MODULE_PARM_DESC(blkcg_debug_stats, "True if you want debug stats, false if not");