2 * Common Block IO controller cgroup interface
4 * Based on ideas and code from CFQ, CFS and BFQ:
5 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
7 * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
8 * Paolo Valente <paolo.valente@unimore.it>
10 * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
11 * Nauman Rafique <nauman@google.com>
13 #include <linux/ioprio.h>
14 #include <linux/kdev_t.h>
15 #include <linux/module.h>
16 #include <linux/err.h>
17 #include <linux/blkdev.h>
18 #include <linux/slab.h>
19 #include <linux/genhd.h>
20 #include <linux/delay.h>
21 #include <linux/atomic.h>
22 #include "blk-cgroup.h"
25 #define MAX_KEY_LEN 100
27 static DEFINE_SPINLOCK(blkio_list_lock);
28 static LIST_HEAD(blkio_list);
30 static DEFINE_MUTEX(all_q_mutex);
31 static LIST_HEAD(all_q_list);
33 /* List of groups pending per cpu stats allocation */
34 static DEFINE_SPINLOCK(alloc_list_lock);
35 static LIST_HEAD(alloc_list);
37 static void blkio_stat_alloc_fn(struct work_struct *);
38 static DECLARE_DELAYED_WORK(blkio_stat_alloc_work, blkio_stat_alloc_fn);
40 struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
41 EXPORT_SYMBOL_GPL(blkio_root_cgroup);
43 static struct blkio_policy_type *blkio_policy[BLKIO_NR_POLICIES];
45 struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
47 return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
48 struct blkio_cgroup, css);
50 EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);
52 static struct blkio_cgroup *task_blkio_cgroup(struct task_struct *tsk)
54 return container_of(task_subsys_state(tsk, blkio_subsys_id),
55 struct blkio_cgroup, css);
58 struct blkio_cgroup *bio_blkio_cgroup(struct bio *bio)
60 if (bio && bio->bi_css)
61 return container_of(bio->bi_css, struct blkio_cgroup, css);
62 return task_blkio_cgroup(current);
64 EXPORT_SYMBOL_GPL(bio_blkio_cgroup);
67 * Worker for allocating per cpu stat for blk groups. This is scheduled on
68 * the system_nrt_wq once there are some groups on the alloc_list waiting
71 static void blkio_stat_alloc_fn(struct work_struct *work)
73 static void *pcpu_stats[BLKIO_NR_POLICIES];
74 struct delayed_work *dwork = to_delayed_work(work);
75 struct blkio_group *blkg;
80 for (i = 0; i < BLKIO_NR_POLICIES; i++) {
81 if (pcpu_stats[i] != NULL)
84 pcpu_stats[i] = alloc_percpu(struct blkio_group_stats_cpu);
86 /* Allocation failed. Try again after some time. */
87 if (pcpu_stats[i] == NULL) {
88 queue_delayed_work(system_nrt_wq, dwork,
89 msecs_to_jiffies(10));
94 spin_lock_irq(&blkio_list_lock);
95 spin_lock(&alloc_list_lock);
97 /* cgroup got deleted or queue exited. */
98 if (!list_empty(&alloc_list)) {
99 blkg = list_first_entry(&alloc_list, struct blkio_group,
101 for (i = 0; i < BLKIO_NR_POLICIES; i++) {
102 struct blkg_policy_data *pd = blkg->pd[i];
104 if (blkio_policy[i] && pd && !pd->stats_cpu)
105 swap(pd->stats_cpu, pcpu_stats[i]);
108 list_del_init(&blkg->alloc_node);
111 empty = list_empty(&alloc_list);
113 spin_unlock(&alloc_list_lock);
114 spin_unlock_irq(&blkio_list_lock);
121 * blkg_free - free a blkg
122 * @blkg: blkg to free
124 * Free @blkg which may be partially allocated.
126 static void blkg_free(struct blkio_group *blkg)
133 for (i = 0; i < BLKIO_NR_POLICIES; i++) {
134 struct blkio_policy_type *pol = blkio_policy[i];
135 struct blkg_policy_data *pd = blkg->pd[i];
140 if (pol && pol->ops.blkio_exit_group_fn)
141 pol->ops.blkio_exit_group_fn(blkg);
143 free_percpu(pd->stats_cpu);
151 * blkg_alloc - allocate a blkg
152 * @blkcg: block cgroup the new blkg is associated with
153 * @q: request_queue the new blkg is associated with
155 * Allocate a new blkg assocating @blkcg and @q.
157 static struct blkio_group *blkg_alloc(struct blkio_cgroup *blkcg,
158 struct request_queue *q)
160 struct blkio_group *blkg;
163 /* alloc and init base part */
164 blkg = kzalloc_node(sizeof(*blkg), GFP_ATOMIC, q->node);
169 INIT_LIST_HEAD(&blkg->q_node);
170 INIT_LIST_HEAD(&blkg->alloc_node);
173 cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
175 for (i = 0; i < BLKIO_NR_POLICIES; i++) {
176 struct blkio_policy_type *pol = blkio_policy[i];
177 struct blkg_policy_data *pd;
182 /* alloc per-policy data and attach it to blkg */
183 pd = kzalloc_node(sizeof(*pd) + pol->pdata_size, GFP_ATOMIC,
194 /* invoke per-policy init */
195 for (i = 0; i < BLKIO_NR_POLICIES; i++) {
196 struct blkio_policy_type *pol = blkio_policy[i];
199 pol->ops.blkio_init_group_fn(blkg);
205 struct blkio_group *blkg_lookup_create(struct blkio_cgroup *blkcg,
206 struct request_queue *q,
208 __releases(q->queue_lock) __acquires(q->queue_lock)
210 struct blkio_group *blkg;
212 WARN_ON_ONCE(!rcu_read_lock_held());
213 lockdep_assert_held(q->queue_lock);
216 * This could be the first entry point of blkcg implementation and
217 * we shouldn't allow anything to go through for a bypassing queue.
218 * The following can be removed if blkg lookup is guaranteed to
219 * fail on a bypassing queue.
221 if (unlikely(blk_queue_bypass(q)) && !for_root)
222 return ERR_PTR(blk_queue_dead(q) ? -EINVAL : -EBUSY);
224 blkg = blkg_lookup(blkcg, q);
228 /* blkg holds a reference to blkcg */
229 if (!css_tryget(&blkcg->css))
230 return ERR_PTR(-EINVAL);
233 * Allocate and initialize.
235 blkg = blkg_alloc(blkcg, q);
237 /* did alloc fail? */
238 if (unlikely(!blkg)) {
239 blkg = ERR_PTR(-ENOMEM);
244 spin_lock(&blkcg->lock);
245 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
246 list_add(&blkg->q_node, &q->blkg_list);
247 spin_unlock(&blkcg->lock);
249 spin_lock(&alloc_list_lock);
250 list_add(&blkg->alloc_node, &alloc_list);
251 /* Queue per cpu stat allocation from worker thread. */
252 queue_delayed_work(system_nrt_wq, &blkio_stat_alloc_work, 0);
253 spin_unlock(&alloc_list_lock);
257 EXPORT_SYMBOL_GPL(blkg_lookup_create);
259 /* called under rcu_read_lock(). */
260 struct blkio_group *blkg_lookup(struct blkio_cgroup *blkcg,
261 struct request_queue *q)
263 struct blkio_group *blkg;
264 struct hlist_node *n;
266 hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node)
271 EXPORT_SYMBOL_GPL(blkg_lookup);
273 static void blkg_destroy(struct blkio_group *blkg)
275 struct request_queue *q = blkg->q;
276 struct blkio_cgroup *blkcg = blkg->blkcg;
278 lockdep_assert_held(q->queue_lock);
279 lockdep_assert_held(&blkcg->lock);
281 /* Something wrong if we are trying to remove same group twice */
282 WARN_ON_ONCE(list_empty(&blkg->q_node));
283 WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
284 list_del_init(&blkg->q_node);
285 hlist_del_init_rcu(&blkg->blkcg_node);
287 spin_lock(&alloc_list_lock);
288 list_del_init(&blkg->alloc_node);
289 spin_unlock(&alloc_list_lock);
292 * Put the reference taken at the time of creation so that when all
293 * queues are gone, group can be destroyed.
299 * XXX: This updates blkg policy data in-place for root blkg, which is
300 * necessary across elevator switch and policy registration as root blkgs
301 * aren't shot down. This broken and racy implementation is temporary.
302 * Eventually, blkg shoot down will be replaced by proper in-place update.
304 void update_root_blkg_pd(struct request_queue *q, enum blkio_policy_id plid)
306 struct blkio_policy_type *pol = blkio_policy[plid];
307 struct blkio_group *blkg = blkg_lookup(&blkio_root_cgroup, q);
308 struct blkg_policy_data *pd;
313 kfree(blkg->pd[plid]);
314 blkg->pd[plid] = NULL;
319 pd = kzalloc(sizeof(*pd) + pol->pdata_size, GFP_KERNEL);
322 pd->stats_cpu = alloc_percpu(struct blkio_group_stats_cpu);
323 WARN_ON_ONCE(!pd->stats_cpu);
327 pol->ops.blkio_init_group_fn(blkg);
329 EXPORT_SYMBOL_GPL(update_root_blkg_pd);
332 * blkg_destroy_all - destroy all blkgs associated with a request_queue
333 * @q: request_queue of interest
334 * @destroy_root: whether to destroy root blkg or not
336 * Destroy blkgs associated with @q. If @destroy_root is %true, all are
337 * destroyed; otherwise, root blkg is left alone.
339 void blkg_destroy_all(struct request_queue *q, bool destroy_root)
341 struct blkio_group *blkg, *n;
343 spin_lock_irq(q->queue_lock);
345 list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
346 struct blkio_cgroup *blkcg = blkg->blkcg;
349 if (!destroy_root && blkg->blkcg == &blkio_root_cgroup)
352 spin_lock(&blkcg->lock);
354 spin_unlock(&blkcg->lock);
357 spin_unlock_irq(q->queue_lock);
359 EXPORT_SYMBOL_GPL(blkg_destroy_all);
361 static void blkg_rcu_free(struct rcu_head *rcu_head)
363 blkg_free(container_of(rcu_head, struct blkio_group, rcu_head));
366 void __blkg_release(struct blkio_group *blkg)
368 /* release the extra blkcg reference this blkg has been holding */
369 css_put(&blkg->blkcg->css);
372 * A group is freed in rcu manner. But having an rcu lock does not
373 * mean that one can access all the fields of blkg and assume these
374 * are valid. For example, don't try to follow throtl_data and
375 * request queue links.
377 * Having a reference to blkg under an rcu allows acess to only
378 * values local to groups like group stats and group rate limits
380 call_rcu(&blkg->rcu_head, blkg_rcu_free);
382 EXPORT_SYMBOL_GPL(__blkg_release);
384 static void blkio_reset_stats_cpu(struct blkio_group *blkg, int plid)
386 struct blkg_policy_data *pd = blkg->pd[plid];
389 if (pd->stats_cpu == NULL)
392 for_each_possible_cpu(cpu) {
393 struct blkio_group_stats_cpu *sc =
394 per_cpu_ptr(pd->stats_cpu, cpu);
396 blkg_rwstat_reset(&sc->service_bytes);
397 blkg_rwstat_reset(&sc->serviced);
402 blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
404 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
405 struct blkio_group *blkg;
406 struct hlist_node *n;
408 spin_lock(&blkio_list_lock);
409 spin_lock_irq(&blkcg->lock);
412 * Note that stat reset is racy - it doesn't synchronize against
413 * stat updates. This is a debug feature which shouldn't exist
414 * anyway. If you get hit by a race, retry.
416 hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
417 struct blkio_policy_type *pol;
419 list_for_each_entry(pol, &blkio_list, list) {
420 blkio_reset_stats_cpu(blkg, pol->plid);
422 if (pol->ops.blkio_reset_group_stats_fn)
423 pol->ops.blkio_reset_group_stats_fn(blkg);
427 spin_unlock_irq(&blkcg->lock);
428 spin_unlock(&blkio_list_lock);
432 static const char *blkg_dev_name(struct blkio_group *blkg)
434 /* some drivers (floppy) instantiate a queue w/o disk registered */
435 if (blkg->q->backing_dev_info.dev)
436 return dev_name(blkg->q->backing_dev_info.dev);
441 * blkcg_print_blkgs - helper for printing per-blkg data
442 * @sf: seq_file to print to
443 * @blkcg: blkcg of interest
444 * @prfill: fill function to print out a blkg
445 * @pol: policy in question
446 * @data: data to be passed to @prfill
447 * @show_total: to print out sum of prfill return values or not
449 * This function invokes @prfill on each blkg of @blkcg if pd for the
450 * policy specified by @pol exists. @prfill is invoked with @sf, the
451 * policy data and @data. If @show_total is %true, the sum of the return
452 * values from @prfill is printed with "Total" label at the end.
454 * This is to be used to construct print functions for
455 * cftype->read_seq_string method.
457 void blkcg_print_blkgs(struct seq_file *sf, struct blkio_cgroup *blkcg,
458 u64 (*prfill)(struct seq_file *, struct blkg_policy_data *, int),
459 int pol, int data, bool show_total)
461 struct blkio_group *blkg;
462 struct hlist_node *n;
465 spin_lock_irq(&blkcg->lock);
466 hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
468 total += prfill(sf, blkg->pd[pol], data);
469 spin_unlock_irq(&blkcg->lock);
472 seq_printf(sf, "Total %llu\n", (unsigned long long)total);
474 EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
477 * __blkg_prfill_u64 - prfill helper for a single u64 value
478 * @sf: seq_file to print to
479 * @pd: policy data of interest
482 * Print @v to @sf for the device assocaited with @pd.
484 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
486 const char *dname = blkg_dev_name(pd->blkg);
491 seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
494 EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
497 * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
498 * @sf: seq_file to print to
499 * @pd: policy data of interest
500 * @rwstat: rwstat to print
502 * Print @rwstat to @sf for the device assocaited with @pd.
504 u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
505 const struct blkg_rwstat *rwstat)
507 static const char *rwstr[] = {
508 [BLKG_RWSTAT_READ] = "Read",
509 [BLKG_RWSTAT_WRITE] = "Write",
510 [BLKG_RWSTAT_SYNC] = "Sync",
511 [BLKG_RWSTAT_ASYNC] = "Async",
513 const char *dname = blkg_dev_name(pd->blkg);
520 for (i = 0; i < BLKG_RWSTAT_NR; i++)
521 seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
522 (unsigned long long)rwstat->cnt[i]);
524 v = rwstat->cnt[BLKG_RWSTAT_READ] + rwstat->cnt[BLKG_RWSTAT_WRITE];
525 seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
529 static u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd,
532 return __blkg_prfill_u64(sf, pd,
533 blkg_stat_read((void *)pd->pdata + off));
536 static u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
539 struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd->pdata + off);
541 return __blkg_prfill_rwstat(sf, pd, &rwstat);
544 /* print blkg_stat specified by BLKCG_STAT_PRIV() */
545 int blkcg_print_stat(struct cgroup *cgrp, struct cftype *cft,
548 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);
550 blkcg_print_blkgs(sf, blkcg, blkg_prfill_stat,
551 BLKCG_STAT_POL(cft->private),
552 BLKCG_STAT_OFF(cft->private), false);
555 EXPORT_SYMBOL_GPL(blkcg_print_stat);
557 /* print blkg_rwstat specified by BLKCG_STAT_PRIV() */
558 int blkcg_print_rwstat(struct cgroup *cgrp, struct cftype *cft,
561 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);
563 blkcg_print_blkgs(sf, blkcg, blkg_prfill_rwstat,
564 BLKCG_STAT_POL(cft->private),
565 BLKCG_STAT_OFF(cft->private), true);
568 EXPORT_SYMBOL_GPL(blkcg_print_rwstat);
571 * blkg_conf_prep - parse and prepare for per-blkg config update
572 * @blkcg: target block cgroup
573 * @input: input string
574 * @ctx: blkg_conf_ctx to be filled
576 * Parse per-blkg config update from @input and initialize @ctx with the
577 * result. @ctx->blkg points to the blkg to be updated and @ctx->v the new
578 * value. This function returns with RCU read locked and must be paired
579 * with blkg_conf_finish().
581 int blkg_conf_prep(struct blkio_cgroup *blkcg, const char *input,
582 struct blkg_conf_ctx *ctx)
585 struct gendisk *disk;
586 struct blkio_group *blkg;
587 unsigned int major, minor;
588 unsigned long long v;
591 if (sscanf(input, "%u:%u %llu", &major, &minor, &v) != 3)
594 disk = get_gendisk(MKDEV(major, minor), &part);
600 spin_lock_irq(disk->queue->queue_lock);
601 blkg = blkg_lookup_create(blkcg, disk->queue, false);
602 spin_unlock_irq(disk->queue->queue_lock);
609 * If queue was bypassing, we should retry. Do so after a
610 * short msleep(). It isn't strictly necessary but queue
611 * can be bypassing for some time and it's always nice to
612 * avoid busy looping.
616 ret = restart_syscall();
626 EXPORT_SYMBOL_GPL(blkg_conf_prep);
629 * blkg_conf_finish - finish up per-blkg config update
630 * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
632 * Finish up after per-blkg config update. This function must be paired
633 * with blkg_conf_prep().
635 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
641 EXPORT_SYMBOL_GPL(blkg_conf_finish);
643 struct cftype blkio_files[] = {
645 .name = "reset_stats",
646 .write_u64 = blkiocg_reset_stats,
652 * blkiocg_pre_destroy - cgroup pre_destroy callback
653 * @cgroup: cgroup of interest
655 * This function is called when @cgroup is about to go away and responsible
656 * for shooting down all blkgs associated with @cgroup. blkgs should be
657 * removed while holding both q and blkcg locks. As blkcg lock is nested
658 * inside q lock, this function performs reverse double lock dancing.
660 * This is the blkcg counterpart of ioc_release_fn().
662 static int blkiocg_pre_destroy(struct cgroup *cgroup)
664 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
666 spin_lock_irq(&blkcg->lock);
668 while (!hlist_empty(&blkcg->blkg_list)) {
669 struct blkio_group *blkg = hlist_entry(blkcg->blkg_list.first,
670 struct blkio_group, blkcg_node);
671 struct request_queue *q = blkg->q;
673 if (spin_trylock(q->queue_lock)) {
675 spin_unlock(q->queue_lock);
677 spin_unlock_irq(&blkcg->lock);
679 spin_lock_irq(&blkcg->lock);
683 spin_unlock_irq(&blkcg->lock);
687 static void blkiocg_destroy(struct cgroup *cgroup)
689 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
691 if (blkcg != &blkio_root_cgroup)
695 static struct cgroup_subsys_state *blkiocg_create(struct cgroup *cgroup)
697 static atomic64_t id_seq = ATOMIC64_INIT(0);
698 struct blkio_cgroup *blkcg;
699 struct cgroup *parent = cgroup->parent;
702 blkcg = &blkio_root_cgroup;
706 blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
708 return ERR_PTR(-ENOMEM);
710 blkcg->weight = BLKIO_WEIGHT_DEFAULT;
711 blkcg->id = atomic64_inc_return(&id_seq); /* root is 0, start from 1 */
713 spin_lock_init(&blkcg->lock);
714 INIT_HLIST_HEAD(&blkcg->blkg_list);
720 * blkcg_init_queue - initialize blkcg part of request queue
721 * @q: request_queue to initialize
723 * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
724 * part of new request_queue @q.
727 * 0 on success, -errno on failure.
729 int blkcg_init_queue(struct request_queue *q)
735 ret = blk_throtl_init(q);
739 mutex_lock(&all_q_mutex);
740 INIT_LIST_HEAD(&q->all_q_node);
741 list_add_tail(&q->all_q_node, &all_q_list);
742 mutex_unlock(&all_q_mutex);
748 * blkcg_drain_queue - drain blkcg part of request_queue
749 * @q: request_queue to drain
751 * Called from blk_drain_queue(). Responsible for draining blkcg part.
753 void blkcg_drain_queue(struct request_queue *q)
755 lockdep_assert_held(q->queue_lock);
761 * blkcg_exit_queue - exit and release blkcg part of request_queue
762 * @q: request_queue being released
764 * Called from blk_release_queue(). Responsible for exiting blkcg part.
766 void blkcg_exit_queue(struct request_queue *q)
768 mutex_lock(&all_q_mutex);
769 list_del_init(&q->all_q_node);
770 mutex_unlock(&all_q_mutex);
772 blkg_destroy_all(q, true);
778 * We cannot support shared io contexts, as we have no mean to support
779 * two tasks with the same ioc in two different groups without major rework
780 * of the main cic data structures. For now we allow a task to change
781 * its cgroup only if it's the only owner of its ioc.
783 static int blkiocg_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
785 struct task_struct *task;
786 struct io_context *ioc;
789 /* task_lock() is needed to avoid races with exit_io_context() */
790 cgroup_taskset_for_each(task, cgrp, tset) {
792 ioc = task->io_context;
793 if (ioc && atomic_read(&ioc->nr_tasks) > 1)
802 static void blkcg_bypass_start(void)
803 __acquires(&all_q_mutex)
805 struct request_queue *q;
807 mutex_lock(&all_q_mutex);
809 list_for_each_entry(q, &all_q_list, all_q_node) {
810 blk_queue_bypass_start(q);
811 blkg_destroy_all(q, false);
815 static void blkcg_bypass_end(void)
816 __releases(&all_q_mutex)
818 struct request_queue *q;
820 list_for_each_entry(q, &all_q_list, all_q_node)
821 blk_queue_bypass_end(q);
823 mutex_unlock(&all_q_mutex);
826 struct cgroup_subsys blkio_subsys = {
828 .create = blkiocg_create,
829 .can_attach = blkiocg_can_attach,
830 .pre_destroy = blkiocg_pre_destroy,
831 .destroy = blkiocg_destroy,
832 .subsys_id = blkio_subsys_id,
833 .base_cftypes = blkio_files,
834 .module = THIS_MODULE,
836 EXPORT_SYMBOL_GPL(blkio_subsys);
838 void blkio_policy_register(struct blkio_policy_type *blkiop)
840 struct request_queue *q;
842 blkcg_bypass_start();
843 spin_lock(&blkio_list_lock);
845 BUG_ON(blkio_policy[blkiop->plid]);
846 blkio_policy[blkiop->plid] = blkiop;
847 list_add_tail(&blkiop->list, &blkio_list);
849 spin_unlock(&blkio_list_lock);
850 list_for_each_entry(q, &all_q_list, all_q_node)
851 update_root_blkg_pd(q, blkiop->plid);
855 WARN_ON(cgroup_add_cftypes(&blkio_subsys, blkiop->cftypes));
857 EXPORT_SYMBOL_GPL(blkio_policy_register);
859 void blkio_policy_unregister(struct blkio_policy_type *blkiop)
861 struct request_queue *q;
864 cgroup_rm_cftypes(&blkio_subsys, blkiop->cftypes);
866 blkcg_bypass_start();
867 spin_lock(&blkio_list_lock);
869 BUG_ON(blkio_policy[blkiop->plid] != blkiop);
870 blkio_policy[blkiop->plid] = NULL;
871 list_del_init(&blkiop->list);
873 spin_unlock(&blkio_list_lock);
874 list_for_each_entry(q, &all_q_list, all_q_node)
875 update_root_blkg_pd(q, blkiop->plid);
878 EXPORT_SYMBOL_GPL(blkio_policy_unregister);