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_MUTEX(blkcg_pol_mutex);
28 static DEFINE_MUTEX(all_q_mutex);
29 static LIST_HEAD(all_q_list);
31 struct blkio_cgroup blkio_root_cgroup = { .cfq_weight = 2 * CFQ_WEIGHT_DEFAULT };
32 EXPORT_SYMBOL_GPL(blkio_root_cgroup);
34 static struct blkio_policy_type *blkio_policy[BLKCG_MAX_POLS];
36 struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
38 return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
39 struct blkio_cgroup, css);
41 EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);
43 static struct blkio_cgroup *task_blkio_cgroup(struct task_struct *tsk)
45 return container_of(task_subsys_state(tsk, blkio_subsys_id),
46 struct blkio_cgroup, css);
49 struct blkio_cgroup *bio_blkio_cgroup(struct bio *bio)
51 if (bio && bio->bi_css)
52 return container_of(bio->bi_css, struct blkio_cgroup, css);
53 return task_blkio_cgroup(current);
55 EXPORT_SYMBOL_GPL(bio_blkio_cgroup);
57 static bool blkcg_policy_enabled(struct request_queue *q,
58 const struct blkio_policy_type *pol)
60 return pol && test_bit(pol->plid, q->blkcg_pols);
63 static size_t blkg_pd_size(const struct blkio_policy_type *pol)
65 return sizeof(struct blkg_policy_data) + pol->pdata_size;
69 * blkg_free - free a blkg
72 * Free @blkg which may be partially allocated.
74 static void blkg_free(struct blkio_group *blkg)
81 for (i = 0; i < BLKCG_MAX_POLS; i++) {
82 struct blkio_policy_type *pol = blkio_policy[i];
83 struct blkg_policy_data *pd = blkg->pd[i];
88 if (pol && pol->ops.blkio_exit_group_fn)
89 pol->ops.blkio_exit_group_fn(blkg);
98 * blkg_alloc - allocate a blkg
99 * @blkcg: block cgroup the new blkg is associated with
100 * @q: request_queue the new blkg is associated with
102 * Allocate a new blkg assocating @blkcg and @q.
104 static struct blkio_group *blkg_alloc(struct blkio_cgroup *blkcg,
105 struct request_queue *q)
107 struct blkio_group *blkg;
110 /* alloc and init base part */
111 blkg = kzalloc_node(sizeof(*blkg), GFP_ATOMIC, q->node);
116 INIT_LIST_HEAD(&blkg->q_node);
119 cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
121 for (i = 0; i < BLKCG_MAX_POLS; i++) {
122 struct blkio_policy_type *pol = blkio_policy[i];
123 struct blkg_policy_data *pd;
125 if (!blkcg_policy_enabled(q, pol))
128 /* alloc per-policy data and attach it to blkg */
129 pd = kzalloc_node(blkg_pd_size(pol), GFP_ATOMIC, q->node);
139 /* invoke per-policy init */
140 for (i = 0; i < BLKCG_MAX_POLS; i++) {
141 struct blkio_policy_type *pol = blkio_policy[i];
143 if (blkcg_policy_enabled(blkg->q, pol))
144 pol->ops.blkio_init_group_fn(blkg);
150 static struct blkio_group *__blkg_lookup(struct blkio_cgroup *blkcg,
151 struct request_queue *q)
153 struct blkio_group *blkg;
154 struct hlist_node *n;
156 hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node)
163 * blkg_lookup - lookup blkg for the specified blkcg - q pair
164 * @blkcg: blkcg of interest
165 * @q: request_queue of interest
167 * Lookup blkg for the @blkcg - @q pair. This function should be called
168 * under RCU read lock and is guaranteed to return %NULL if @q is bypassing
169 * - see blk_queue_bypass_start() for details.
171 struct blkio_group *blkg_lookup(struct blkio_cgroup *blkcg,
172 struct request_queue *q)
174 WARN_ON_ONCE(!rcu_read_lock_held());
176 if (unlikely(blk_queue_bypass(q)))
178 return __blkg_lookup(blkcg, q);
180 EXPORT_SYMBOL_GPL(blkg_lookup);
182 struct blkio_group *blkg_lookup_create(struct blkio_cgroup *blkcg,
183 struct request_queue *q,
185 __releases(q->queue_lock) __acquires(q->queue_lock)
187 struct blkio_group *blkg;
189 WARN_ON_ONCE(!rcu_read_lock_held());
190 lockdep_assert_held(q->queue_lock);
193 * This could be the first entry point of blkcg implementation and
194 * we shouldn't allow anything to go through for a bypassing queue.
196 if (unlikely(blk_queue_bypass(q)) && !for_root)
197 return ERR_PTR(blk_queue_dead(q) ? -EINVAL : -EBUSY);
199 blkg = __blkg_lookup(blkcg, q);
203 /* blkg holds a reference to blkcg */
204 if (!css_tryget(&blkcg->css))
205 return ERR_PTR(-EINVAL);
208 * Allocate and initialize.
210 blkg = blkg_alloc(blkcg, q);
212 /* did alloc fail? */
213 if (unlikely(!blkg)) {
214 blkg = ERR_PTR(-ENOMEM);
219 spin_lock(&blkcg->lock);
220 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
221 list_add(&blkg->q_node, &q->blkg_list);
222 spin_unlock(&blkcg->lock);
226 EXPORT_SYMBOL_GPL(blkg_lookup_create);
228 static void blkg_destroy(struct blkio_group *blkg)
230 struct request_queue *q = blkg->q;
231 struct blkio_cgroup *blkcg = blkg->blkcg;
233 lockdep_assert_held(q->queue_lock);
234 lockdep_assert_held(&blkcg->lock);
236 /* Something wrong if we are trying to remove same group twice */
237 WARN_ON_ONCE(list_empty(&blkg->q_node));
238 WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
239 list_del_init(&blkg->q_node);
240 hlist_del_init_rcu(&blkg->blkcg_node);
243 * Put the reference taken at the time of creation so that when all
244 * queues are gone, group can be destroyed.
250 * blkg_destroy_all - destroy all blkgs associated with a request_queue
251 * @q: request_queue of interest
252 * @destroy_root: whether to destroy root blkg or not
254 * Destroy blkgs associated with @q. If @destroy_root is %true, all are
255 * destroyed; otherwise, root blkg is left alone.
257 void blkg_destroy_all(struct request_queue *q, bool destroy_root)
259 struct blkio_group *blkg, *n;
261 spin_lock_irq(q->queue_lock);
263 list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
264 struct blkio_cgroup *blkcg = blkg->blkcg;
267 if (!destroy_root && blkg->blkcg == &blkio_root_cgroup)
270 spin_lock(&blkcg->lock);
272 spin_unlock(&blkcg->lock);
275 spin_unlock_irq(q->queue_lock);
277 EXPORT_SYMBOL_GPL(blkg_destroy_all);
279 static void blkg_rcu_free(struct rcu_head *rcu_head)
281 blkg_free(container_of(rcu_head, struct blkio_group, rcu_head));
284 void __blkg_release(struct blkio_group *blkg)
286 /* release the extra blkcg reference this blkg has been holding */
287 css_put(&blkg->blkcg->css);
290 * A group is freed in rcu manner. But having an rcu lock does not
291 * mean that one can access all the fields of blkg and assume these
292 * are valid. For example, don't try to follow throtl_data and
293 * request queue links.
295 * Having a reference to blkg under an rcu allows acess to only
296 * values local to groups like group stats and group rate limits
298 call_rcu(&blkg->rcu_head, blkg_rcu_free);
300 EXPORT_SYMBOL_GPL(__blkg_release);
303 blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
305 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
306 struct blkio_group *blkg;
307 struct hlist_node *n;
310 mutex_lock(&blkcg_pol_mutex);
311 spin_lock_irq(&blkcg->lock);
314 * Note that stat reset is racy - it doesn't synchronize against
315 * stat updates. This is a debug feature which shouldn't exist
316 * anyway. If you get hit by a race, retry.
318 hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
319 for (i = 0; i < BLKCG_MAX_POLS; i++) {
320 struct blkio_policy_type *pol = blkio_policy[i];
322 if (blkcg_policy_enabled(blkg->q, pol) &&
323 pol->ops.blkio_reset_group_stats_fn)
324 pol->ops.blkio_reset_group_stats_fn(blkg);
328 spin_unlock_irq(&blkcg->lock);
329 mutex_unlock(&blkcg_pol_mutex);
333 static const char *blkg_dev_name(struct blkio_group *blkg)
335 /* some drivers (floppy) instantiate a queue w/o disk registered */
336 if (blkg->q->backing_dev_info.dev)
337 return dev_name(blkg->q->backing_dev_info.dev);
342 * blkcg_print_blkgs - helper for printing per-blkg data
343 * @sf: seq_file to print to
344 * @blkcg: blkcg of interest
345 * @prfill: fill function to print out a blkg
346 * @pol: policy in question
347 * @data: data to be passed to @prfill
348 * @show_total: to print out sum of prfill return values or not
350 * This function invokes @prfill on each blkg of @blkcg if pd for the
351 * policy specified by @pol exists. @prfill is invoked with @sf, the
352 * policy data and @data. If @show_total is %true, the sum of the return
353 * values from @prfill is printed with "Total" label at the end.
355 * This is to be used to construct print functions for
356 * cftype->read_seq_string method.
358 void blkcg_print_blkgs(struct seq_file *sf, struct blkio_cgroup *blkcg,
359 u64 (*prfill)(struct seq_file *, void *, int),
360 const struct blkio_policy_type *pol, int data,
363 struct blkio_group *blkg;
364 struct hlist_node *n;
367 spin_lock_irq(&blkcg->lock);
368 hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
369 if (blkcg_policy_enabled(blkg->q, pol))
370 total += prfill(sf, blkg->pd[pol->plid]->pdata, data);
371 spin_unlock_irq(&blkcg->lock);
374 seq_printf(sf, "Total %llu\n", (unsigned long long)total);
376 EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
379 * __blkg_prfill_u64 - prfill helper for a single u64 value
380 * @sf: seq_file to print to
381 * @pdata: policy private data of interest
384 * Print @v to @sf for the device assocaited with @pdata.
386 u64 __blkg_prfill_u64(struct seq_file *sf, void *pdata, u64 v)
388 const char *dname = blkg_dev_name(pdata_to_blkg(pdata));
393 seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
396 EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
399 * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
400 * @sf: seq_file to print to
401 * @pdata: policy private data of interest
402 * @rwstat: rwstat to print
404 * Print @rwstat to @sf for the device assocaited with @pdata.
406 u64 __blkg_prfill_rwstat(struct seq_file *sf, void *pdata,
407 const struct blkg_rwstat *rwstat)
409 static const char *rwstr[] = {
410 [BLKG_RWSTAT_READ] = "Read",
411 [BLKG_RWSTAT_WRITE] = "Write",
412 [BLKG_RWSTAT_SYNC] = "Sync",
413 [BLKG_RWSTAT_ASYNC] = "Async",
415 const char *dname = blkg_dev_name(pdata_to_blkg(pdata));
422 for (i = 0; i < BLKG_RWSTAT_NR; i++)
423 seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
424 (unsigned long long)rwstat->cnt[i]);
426 v = rwstat->cnt[BLKG_RWSTAT_READ] + rwstat->cnt[BLKG_RWSTAT_WRITE];
427 seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
432 * blkg_prfill_stat - prfill callback for blkg_stat
433 * @sf: seq_file to print to
434 * @pdata: policy private data of interest
435 * @off: offset to the blkg_stat in @pdata
437 * prfill callback for printing a blkg_stat.
439 u64 blkg_prfill_stat(struct seq_file *sf, void *pdata, int off)
441 return __blkg_prfill_u64(sf, pdata, blkg_stat_read(pdata + off));
443 EXPORT_SYMBOL_GPL(blkg_prfill_stat);
446 * blkg_prfill_rwstat - prfill callback for blkg_rwstat
447 * @sf: seq_file to print to
448 * @pdata: policy private data of interest
449 * @off: offset to the blkg_rwstat in @pdata
451 * prfill callback for printing a blkg_rwstat.
453 u64 blkg_prfill_rwstat(struct seq_file *sf, void *pdata, int off)
455 struct blkg_rwstat rwstat = blkg_rwstat_read(pdata + off);
457 return __blkg_prfill_rwstat(sf, pdata, &rwstat);
459 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
462 * blkg_conf_prep - parse and prepare for per-blkg config update
463 * @blkcg: target block cgroup
464 * @pol: target policy
465 * @input: input string
466 * @ctx: blkg_conf_ctx to be filled
468 * Parse per-blkg config update from @input and initialize @ctx with the
469 * result. @ctx->blkg points to the blkg to be updated and @ctx->v the new
470 * value. This function returns with RCU read lock and queue lock held and
471 * must be paired with blkg_conf_finish().
473 int blkg_conf_prep(struct blkio_cgroup *blkcg,
474 const struct blkio_policy_type *pol, const char *input,
475 struct blkg_conf_ctx *ctx)
476 __acquires(rcu) __acquires(disk->queue->queue_lock)
478 struct gendisk *disk;
479 struct blkio_group *blkg;
480 unsigned int major, minor;
481 unsigned long long v;
484 if (sscanf(input, "%u:%u %llu", &major, &minor, &v) != 3)
487 disk = get_gendisk(MKDEV(major, minor), &part);
492 spin_lock_irq(disk->queue->queue_lock);
494 if (blkcg_policy_enabled(disk->queue, pol))
495 blkg = blkg_lookup_create(blkcg, disk->queue, false);
497 blkg = ERR_PTR(-EINVAL);
502 spin_unlock_irq(disk->queue->queue_lock);
505 * If queue was bypassing, we should retry. Do so after a
506 * short msleep(). It isn't strictly necessary but queue
507 * can be bypassing for some time and it's always nice to
508 * avoid busy looping.
512 ret = restart_syscall();
522 EXPORT_SYMBOL_GPL(blkg_conf_prep);
525 * blkg_conf_finish - finish up per-blkg config update
526 * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
528 * Finish up after per-blkg config update. This function must be paired
529 * with blkg_conf_prep().
531 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
532 __releases(ctx->disk->queue->queue_lock) __releases(rcu)
534 spin_unlock_irq(ctx->disk->queue->queue_lock);
538 EXPORT_SYMBOL_GPL(blkg_conf_finish);
540 struct cftype blkio_files[] = {
542 .name = "reset_stats",
543 .write_u64 = blkiocg_reset_stats,
549 * blkiocg_pre_destroy - cgroup pre_destroy callback
550 * @cgroup: cgroup of interest
552 * This function is called when @cgroup is about to go away and responsible
553 * for shooting down all blkgs associated with @cgroup. blkgs should be
554 * removed while holding both q and blkcg locks. As blkcg lock is nested
555 * inside q lock, this function performs reverse double lock dancing.
557 * This is the blkcg counterpart of ioc_release_fn().
559 static int blkiocg_pre_destroy(struct cgroup *cgroup)
561 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
563 spin_lock_irq(&blkcg->lock);
565 while (!hlist_empty(&blkcg->blkg_list)) {
566 struct blkio_group *blkg = hlist_entry(blkcg->blkg_list.first,
567 struct blkio_group, blkcg_node);
568 struct request_queue *q = blkg->q;
570 if (spin_trylock(q->queue_lock)) {
572 spin_unlock(q->queue_lock);
574 spin_unlock_irq(&blkcg->lock);
576 spin_lock_irq(&blkcg->lock);
580 spin_unlock_irq(&blkcg->lock);
584 static void blkiocg_destroy(struct cgroup *cgroup)
586 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
588 if (blkcg != &blkio_root_cgroup)
592 static struct cgroup_subsys_state *blkiocg_create(struct cgroup *cgroup)
594 static atomic64_t id_seq = ATOMIC64_INIT(0);
595 struct blkio_cgroup *blkcg;
596 struct cgroup *parent = cgroup->parent;
599 blkcg = &blkio_root_cgroup;
603 blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
605 return ERR_PTR(-ENOMEM);
607 blkcg->cfq_weight = CFQ_WEIGHT_DEFAULT;
608 blkcg->id = atomic64_inc_return(&id_seq); /* root is 0, start from 1 */
610 spin_lock_init(&blkcg->lock);
611 INIT_HLIST_HEAD(&blkcg->blkg_list);
617 * blkcg_init_queue - initialize blkcg part of request queue
618 * @q: request_queue to initialize
620 * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
621 * part of new request_queue @q.
624 * 0 on success, -errno on failure.
626 int blkcg_init_queue(struct request_queue *q)
632 ret = blk_throtl_init(q);
636 mutex_lock(&all_q_mutex);
637 INIT_LIST_HEAD(&q->all_q_node);
638 list_add_tail(&q->all_q_node, &all_q_list);
639 mutex_unlock(&all_q_mutex);
645 * blkcg_drain_queue - drain blkcg part of request_queue
646 * @q: request_queue to drain
648 * Called from blk_drain_queue(). Responsible for draining blkcg part.
650 void blkcg_drain_queue(struct request_queue *q)
652 lockdep_assert_held(q->queue_lock);
658 * blkcg_exit_queue - exit and release blkcg part of request_queue
659 * @q: request_queue being released
661 * Called from blk_release_queue(). Responsible for exiting blkcg part.
663 void blkcg_exit_queue(struct request_queue *q)
665 mutex_lock(&all_q_mutex);
666 list_del_init(&q->all_q_node);
667 mutex_unlock(&all_q_mutex);
669 blkg_destroy_all(q, true);
675 * We cannot support shared io contexts, as we have no mean to support
676 * two tasks with the same ioc in two different groups without major rework
677 * of the main cic data structures. For now we allow a task to change
678 * its cgroup only if it's the only owner of its ioc.
680 static int blkiocg_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
682 struct task_struct *task;
683 struct io_context *ioc;
686 /* task_lock() is needed to avoid races with exit_io_context() */
687 cgroup_taskset_for_each(task, cgrp, tset) {
689 ioc = task->io_context;
690 if (ioc && atomic_read(&ioc->nr_tasks) > 1)
699 struct cgroup_subsys blkio_subsys = {
701 .create = blkiocg_create,
702 .can_attach = blkiocg_can_attach,
703 .pre_destroy = blkiocg_pre_destroy,
704 .destroy = blkiocg_destroy,
705 .subsys_id = blkio_subsys_id,
706 .base_cftypes = blkio_files,
707 .module = THIS_MODULE,
709 EXPORT_SYMBOL_GPL(blkio_subsys);
712 * blkcg_activate_policy - activate a blkcg policy on a request_queue
713 * @q: request_queue of interest
714 * @pol: blkcg policy to activate
716 * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through
717 * bypass mode to populate its blkgs with policy_data for @pol.
719 * Activation happens with @q bypassed, so nobody would be accessing blkgs
720 * from IO path. Update of each blkg is protected by both queue and blkcg
721 * locks so that holding either lock and testing blkcg_policy_enabled() is
722 * always enough for dereferencing policy data.
724 * The caller is responsible for synchronizing [de]activations and policy
725 * [un]registerations. Returns 0 on success, -errno on failure.
727 int blkcg_activate_policy(struct request_queue *q,
728 const struct blkio_policy_type *pol)
731 struct blkio_group *blkg;
732 struct blkg_policy_data *pd, *n;
735 if (blkcg_policy_enabled(q, pol))
738 blk_queue_bypass_start(q);
740 /* make sure the root blkg exists and count the existing blkgs */
741 spin_lock_irq(q->queue_lock);
744 blkg = blkg_lookup_create(&blkio_root_cgroup, q, true);
753 list_for_each_entry(blkg, &q->blkg_list, q_node)
756 spin_unlock_irq(q->queue_lock);
758 /* allocate policy_data for all existing blkgs */
760 pd = kzalloc_node(blkg_pd_size(pol), GFP_KERNEL, q->node);
765 list_add_tail(&pd->alloc_node, &pds);
769 * Install the allocated pds. With @q bypassing, no new blkg
770 * should have been created while the queue lock was dropped.
772 spin_lock_irq(q->queue_lock);
774 list_for_each_entry(blkg, &q->blkg_list, q_node) {
775 if (WARN_ON(list_empty(&pds))) {
776 /* umm... this shouldn't happen, just abort */
780 pd = list_first_entry(&pds, struct blkg_policy_data, alloc_node);
781 list_del_init(&pd->alloc_node);
783 /* grab blkcg lock too while installing @pd on @blkg */
784 spin_lock(&blkg->blkcg->lock);
786 blkg->pd[pol->plid] = pd;
788 pol->ops.blkio_init_group_fn(blkg);
790 spin_unlock(&blkg->blkcg->lock);
793 __set_bit(pol->plid, q->blkcg_pols);
796 spin_unlock_irq(q->queue_lock);
798 blk_queue_bypass_end(q);
799 list_for_each_entry_safe(pd, n, &pds, alloc_node)
803 EXPORT_SYMBOL_GPL(blkcg_activate_policy);
806 * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
807 * @q: request_queue of interest
808 * @pol: blkcg policy to deactivate
810 * Deactivate @pol on @q. Follows the same synchronization rules as
811 * blkcg_activate_policy().
813 void blkcg_deactivate_policy(struct request_queue *q,
814 const struct blkio_policy_type *pol)
816 struct blkio_group *blkg;
818 if (!blkcg_policy_enabled(q, pol))
821 blk_queue_bypass_start(q);
822 spin_lock_irq(q->queue_lock);
824 __clear_bit(pol->plid, q->blkcg_pols);
826 list_for_each_entry(blkg, &q->blkg_list, q_node) {
827 /* grab blkcg lock too while removing @pd from @blkg */
828 spin_lock(&blkg->blkcg->lock);
830 if (pol->ops.blkio_exit_group_fn)
831 pol->ops.blkio_exit_group_fn(blkg);
833 kfree(blkg->pd[pol->plid]);
834 blkg->pd[pol->plid] = NULL;
836 spin_unlock(&blkg->blkcg->lock);
839 spin_unlock_irq(q->queue_lock);
840 blk_queue_bypass_end(q);
842 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
845 * blkio_policy_register - register a blkcg policy
846 * @blkiop: blkcg policy to register
848 * Register @blkiop with blkcg core. Might sleep and @blkiop may be
849 * modified on successful registration. Returns 0 on success and -errno on
852 int blkio_policy_register(struct blkio_policy_type *blkiop)
856 mutex_lock(&blkcg_pol_mutex);
858 /* find an empty slot */
860 for (i = 0; i < BLKCG_MAX_POLS; i++)
861 if (!blkio_policy[i])
863 if (i >= BLKCG_MAX_POLS)
866 /* register and update blkgs */
868 blkio_policy[i] = blkiop;
870 /* everything is in place, add intf files for the new policy */
872 WARN_ON(cgroup_add_cftypes(&blkio_subsys, blkiop->cftypes));
875 mutex_unlock(&blkcg_pol_mutex);
878 EXPORT_SYMBOL_GPL(blkio_policy_register);
881 * blkiop_policy_unregister - unregister a blkcg policy
882 * @blkiop: blkcg policy to unregister
884 * Undo blkio_policy_register(@blkiop). Might sleep.
886 void blkio_policy_unregister(struct blkio_policy_type *blkiop)
888 mutex_lock(&blkcg_pol_mutex);
890 if (WARN_ON(blkio_policy[blkiop->plid] != blkiop))
893 /* kill the intf files first */
895 cgroup_rm_cftypes(&blkio_subsys, blkiop->cftypes);
897 /* unregister and update blkgs */
898 blkio_policy[blkiop->plid] = NULL;
900 mutex_unlock(&blkcg_pol_mutex);
902 EXPORT_SYMBOL_GPL(blkio_policy_unregister);