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);
29 struct blkcg blkcg_root = { .cfq_weight = 2 * CFQ_WEIGHT_DEFAULT };
30 EXPORT_SYMBOL_GPL(blkcg_root);
32 static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];
34 struct blkcg *cgroup_to_blkcg(struct cgroup *cgroup)
36 return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
39 EXPORT_SYMBOL_GPL(cgroup_to_blkcg);
41 static struct blkcg *task_blkcg(struct task_struct *tsk)
43 return container_of(task_subsys_state(tsk, blkio_subsys_id),
47 struct blkcg *bio_blkcg(struct bio *bio)
49 if (bio && bio->bi_css)
50 return container_of(bio->bi_css, struct blkcg, css);
51 return task_blkcg(current);
53 EXPORT_SYMBOL_GPL(bio_blkcg);
55 static bool blkcg_policy_enabled(struct request_queue *q,
56 const struct blkcg_policy *pol)
58 return pol && test_bit(pol->plid, q->blkcg_pols);
61 static size_t blkg_pd_size(const struct blkcg_policy *pol)
63 return sizeof(struct blkg_policy_data) + pol->pdata_size;
67 * blkg_free - free a blkg
70 * Free @blkg which may be partially allocated.
72 static void blkg_free(struct blkcg_gq *blkg)
79 for (i = 0; i < BLKCG_MAX_POLS; i++) {
80 struct blkcg_policy *pol = blkcg_policy[i];
81 struct blkg_policy_data *pd = blkg->pd[i];
86 if (pol && pol->ops.pd_exit_fn)
87 pol->ops.pd_exit_fn(blkg);
96 * blkg_alloc - allocate a blkg
97 * @blkcg: block cgroup the new blkg is associated with
98 * @q: request_queue the new blkg is associated with
100 * Allocate a new blkg assocating @blkcg and @q.
102 static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q)
104 struct blkcg_gq *blkg;
107 /* alloc and init base part */
108 blkg = kzalloc_node(sizeof(*blkg), GFP_ATOMIC, q->node);
113 INIT_LIST_HEAD(&blkg->q_node);
117 for (i = 0; i < BLKCG_MAX_POLS; i++) {
118 struct blkcg_policy *pol = blkcg_policy[i];
119 struct blkg_policy_data *pd;
121 if (!blkcg_policy_enabled(q, pol))
124 /* alloc per-policy data and attach it to blkg */
125 pd = kzalloc_node(blkg_pd_size(pol), GFP_ATOMIC, q->node);
135 /* invoke per-policy init */
136 for (i = 0; i < BLKCG_MAX_POLS; i++) {
137 struct blkcg_policy *pol = blkcg_policy[i];
139 if (blkcg_policy_enabled(blkg->q, pol))
140 pol->ops.pd_init_fn(blkg);
146 static struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg,
147 struct request_queue *q)
149 struct blkcg_gq *blkg;
150 struct hlist_node *n;
152 hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node)
159 * blkg_lookup - lookup blkg for the specified blkcg - q pair
160 * @blkcg: blkcg of interest
161 * @q: request_queue of interest
163 * Lookup blkg for the @blkcg - @q pair. This function should be called
164 * under RCU read lock and is guaranteed to return %NULL if @q is bypassing
165 * - see blk_queue_bypass_start() for details.
167 struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, struct request_queue *q)
169 WARN_ON_ONCE(!rcu_read_lock_held());
171 if (unlikely(blk_queue_bypass(q)))
173 return __blkg_lookup(blkcg, q);
175 EXPORT_SYMBOL_GPL(blkg_lookup);
177 static struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
178 struct request_queue *q)
179 __releases(q->queue_lock) __acquires(q->queue_lock)
181 struct blkcg_gq *blkg;
183 WARN_ON_ONCE(!rcu_read_lock_held());
184 lockdep_assert_held(q->queue_lock);
186 blkg = __blkg_lookup(blkcg, q);
190 /* blkg holds a reference to blkcg */
191 if (!css_tryget(&blkcg->css))
192 return ERR_PTR(-EINVAL);
195 * Allocate and initialize.
197 blkg = blkg_alloc(blkcg, q);
199 /* did alloc fail? */
200 if (unlikely(!blkg)) {
201 blkg = ERR_PTR(-ENOMEM);
206 spin_lock(&blkcg->lock);
207 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
208 list_add(&blkg->q_node, &q->blkg_list);
209 spin_unlock(&blkcg->lock);
214 struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
215 struct request_queue *q)
218 * This could be the first entry point of blkcg implementation and
219 * we shouldn't allow anything to go through for a bypassing queue.
221 if (unlikely(blk_queue_bypass(q)))
222 return ERR_PTR(blk_queue_dead(q) ? -EINVAL : -EBUSY);
223 return __blkg_lookup_create(blkcg, q);
225 EXPORT_SYMBOL_GPL(blkg_lookup_create);
227 static void blkg_destroy(struct blkcg_gq *blkg)
229 struct request_queue *q = blkg->q;
230 struct blkcg *blkcg = blkg->blkcg;
232 lockdep_assert_held(q->queue_lock);
233 lockdep_assert_held(&blkcg->lock);
235 /* Something wrong if we are trying to remove same group twice */
236 WARN_ON_ONCE(list_empty(&blkg->q_node));
237 WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
238 list_del_init(&blkg->q_node);
239 hlist_del_init_rcu(&blkg->blkcg_node);
242 * Put the reference taken at the time of creation so that when all
243 * queues are gone, group can be destroyed.
249 * blkg_destroy_all - destroy all blkgs associated with a request_queue
250 * @q: request_queue of interest
252 * Destroy all blkgs associated with @q.
254 static void blkg_destroy_all(struct request_queue *q)
256 struct blkcg_gq *blkg, *n;
258 lockdep_assert_held(q->queue_lock);
260 list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
261 struct blkcg *blkcg = blkg->blkcg;
263 spin_lock(&blkcg->lock);
265 spin_unlock(&blkcg->lock);
269 static void blkg_rcu_free(struct rcu_head *rcu_head)
271 blkg_free(container_of(rcu_head, struct blkcg_gq, rcu_head));
274 void __blkg_release(struct blkcg_gq *blkg)
276 /* release the extra blkcg reference this blkg has been holding */
277 css_put(&blkg->blkcg->css);
280 * A group is freed in rcu manner. But having an rcu lock does not
281 * mean that one can access all the fields of blkg and assume these
282 * are valid. For example, don't try to follow throtl_data and
283 * request queue links.
285 * Having a reference to blkg under an rcu allows acess to only
286 * values local to groups like group stats and group rate limits
288 call_rcu(&blkg->rcu_head, blkg_rcu_free);
290 EXPORT_SYMBOL_GPL(__blkg_release);
292 static int blkcg_reset_stats(struct cgroup *cgroup, struct cftype *cftype,
295 struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
296 struct blkcg_gq *blkg;
297 struct hlist_node *n;
300 mutex_lock(&blkcg_pol_mutex);
301 spin_lock_irq(&blkcg->lock);
304 * Note that stat reset is racy - it doesn't synchronize against
305 * stat updates. This is a debug feature which shouldn't exist
306 * anyway. If you get hit by a race, retry.
308 hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
309 for (i = 0; i < BLKCG_MAX_POLS; i++) {
310 struct blkcg_policy *pol = blkcg_policy[i];
312 if (blkcg_policy_enabled(blkg->q, pol) &&
313 pol->ops.pd_reset_stats_fn)
314 pol->ops.pd_reset_stats_fn(blkg);
318 spin_unlock_irq(&blkcg->lock);
319 mutex_unlock(&blkcg_pol_mutex);
323 static const char *blkg_dev_name(struct blkcg_gq *blkg)
325 /* some drivers (floppy) instantiate a queue w/o disk registered */
326 if (blkg->q->backing_dev_info.dev)
327 return dev_name(blkg->q->backing_dev_info.dev);
332 * blkcg_print_blkgs - helper for printing per-blkg data
333 * @sf: seq_file to print to
334 * @blkcg: blkcg of interest
335 * @prfill: fill function to print out a blkg
336 * @pol: policy in question
337 * @data: data to be passed to @prfill
338 * @show_total: to print out sum of prfill return values or not
340 * This function invokes @prfill on each blkg of @blkcg if pd for the
341 * policy specified by @pol exists. @prfill is invoked with @sf, the
342 * policy data and @data. If @show_total is %true, the sum of the return
343 * values from @prfill is printed with "Total" label at the end.
345 * This is to be used to construct print functions for
346 * cftype->read_seq_string method.
348 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
349 u64 (*prfill)(struct seq_file *, void *, int),
350 const struct blkcg_policy *pol, int data,
353 struct blkcg_gq *blkg;
354 struct hlist_node *n;
357 spin_lock_irq(&blkcg->lock);
358 hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
359 if (blkcg_policy_enabled(blkg->q, pol))
360 total += prfill(sf, blkg->pd[pol->plid]->pdata, data);
361 spin_unlock_irq(&blkcg->lock);
364 seq_printf(sf, "Total %llu\n", (unsigned long long)total);
366 EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
369 * __blkg_prfill_u64 - prfill helper for a single u64 value
370 * @sf: seq_file to print to
371 * @pdata: policy private data of interest
374 * Print @v to @sf for the device assocaited with @pdata.
376 u64 __blkg_prfill_u64(struct seq_file *sf, void *pdata, u64 v)
378 const char *dname = blkg_dev_name(pdata_to_blkg(pdata));
383 seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
386 EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
389 * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
390 * @sf: seq_file to print to
391 * @pdata: policy private data of interest
392 * @rwstat: rwstat to print
394 * Print @rwstat to @sf for the device assocaited with @pdata.
396 u64 __blkg_prfill_rwstat(struct seq_file *sf, void *pdata,
397 const struct blkg_rwstat *rwstat)
399 static const char *rwstr[] = {
400 [BLKG_RWSTAT_READ] = "Read",
401 [BLKG_RWSTAT_WRITE] = "Write",
402 [BLKG_RWSTAT_SYNC] = "Sync",
403 [BLKG_RWSTAT_ASYNC] = "Async",
405 const char *dname = blkg_dev_name(pdata_to_blkg(pdata));
412 for (i = 0; i < BLKG_RWSTAT_NR; i++)
413 seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
414 (unsigned long long)rwstat->cnt[i]);
416 v = rwstat->cnt[BLKG_RWSTAT_READ] + rwstat->cnt[BLKG_RWSTAT_WRITE];
417 seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
422 * blkg_prfill_stat - prfill callback for blkg_stat
423 * @sf: seq_file to print to
424 * @pdata: policy private data of interest
425 * @off: offset to the blkg_stat in @pdata
427 * prfill callback for printing a blkg_stat.
429 u64 blkg_prfill_stat(struct seq_file *sf, void *pdata, int off)
431 return __blkg_prfill_u64(sf, pdata, blkg_stat_read(pdata + off));
433 EXPORT_SYMBOL_GPL(blkg_prfill_stat);
436 * blkg_prfill_rwstat - prfill callback for blkg_rwstat
437 * @sf: seq_file to print to
438 * @pdata: policy private data of interest
439 * @off: offset to the blkg_rwstat in @pdata
441 * prfill callback for printing a blkg_rwstat.
443 u64 blkg_prfill_rwstat(struct seq_file *sf, void *pdata, int off)
445 struct blkg_rwstat rwstat = blkg_rwstat_read(pdata + off);
447 return __blkg_prfill_rwstat(sf, pdata, &rwstat);
449 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
452 * blkg_conf_prep - parse and prepare for per-blkg config update
453 * @blkcg: target block cgroup
454 * @pol: target policy
455 * @input: input string
456 * @ctx: blkg_conf_ctx to be filled
458 * Parse per-blkg config update from @input and initialize @ctx with the
459 * result. @ctx->blkg points to the blkg to be updated and @ctx->v the new
460 * value. This function returns with RCU read lock and queue lock held and
461 * must be paired with blkg_conf_finish().
463 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
464 const char *input, struct blkg_conf_ctx *ctx)
465 __acquires(rcu) __acquires(disk->queue->queue_lock)
467 struct gendisk *disk;
468 struct blkcg_gq *blkg;
469 unsigned int major, minor;
470 unsigned long long v;
473 if (sscanf(input, "%u:%u %llu", &major, &minor, &v) != 3)
476 disk = get_gendisk(MKDEV(major, minor), &part);
481 spin_lock_irq(disk->queue->queue_lock);
483 if (blkcg_policy_enabled(disk->queue, pol))
484 blkg = blkg_lookup_create(blkcg, disk->queue);
486 blkg = ERR_PTR(-EINVAL);
491 spin_unlock_irq(disk->queue->queue_lock);
494 * If queue was bypassing, we should retry. Do so after a
495 * short msleep(). It isn't strictly necessary but queue
496 * can be bypassing for some time and it's always nice to
497 * avoid busy looping.
501 ret = restart_syscall();
511 EXPORT_SYMBOL_GPL(blkg_conf_prep);
514 * blkg_conf_finish - finish up per-blkg config update
515 * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
517 * Finish up after per-blkg config update. This function must be paired
518 * with blkg_conf_prep().
520 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
521 __releases(ctx->disk->queue->queue_lock) __releases(rcu)
523 spin_unlock_irq(ctx->disk->queue->queue_lock);
527 EXPORT_SYMBOL_GPL(blkg_conf_finish);
529 struct cftype blkcg_files[] = {
531 .name = "reset_stats",
532 .write_u64 = blkcg_reset_stats,
538 * blkcg_pre_destroy - cgroup pre_destroy callback
539 * @cgroup: cgroup of interest
541 * This function is called when @cgroup is about to go away and responsible
542 * for shooting down all blkgs associated with @cgroup. blkgs should be
543 * removed while holding both q and blkcg locks. As blkcg lock is nested
544 * inside q lock, this function performs reverse double lock dancing.
546 * This is the blkcg counterpart of ioc_release_fn().
548 static int blkcg_pre_destroy(struct cgroup *cgroup)
550 struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
552 spin_lock_irq(&blkcg->lock);
554 while (!hlist_empty(&blkcg->blkg_list)) {
555 struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
556 struct blkcg_gq, blkcg_node);
557 struct request_queue *q = blkg->q;
559 if (spin_trylock(q->queue_lock)) {
561 spin_unlock(q->queue_lock);
563 spin_unlock_irq(&blkcg->lock);
565 spin_lock_irq(&blkcg->lock);
569 spin_unlock_irq(&blkcg->lock);
573 static void blkcg_destroy(struct cgroup *cgroup)
575 struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
577 if (blkcg != &blkcg_root)
581 static struct cgroup_subsys_state *blkcg_create(struct cgroup *cgroup)
583 static atomic64_t id_seq = ATOMIC64_INIT(0);
585 struct cgroup *parent = cgroup->parent;
592 blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
594 return ERR_PTR(-ENOMEM);
596 blkcg->cfq_weight = CFQ_WEIGHT_DEFAULT;
597 blkcg->id = atomic64_inc_return(&id_seq); /* root is 0, start from 1 */
599 spin_lock_init(&blkcg->lock);
600 INIT_HLIST_HEAD(&blkcg->blkg_list);
606 * blkcg_init_queue - initialize blkcg part of request queue
607 * @q: request_queue to initialize
609 * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
610 * part of new request_queue @q.
613 * 0 on success, -errno on failure.
615 int blkcg_init_queue(struct request_queue *q)
619 return blk_throtl_init(q);
623 * blkcg_drain_queue - drain blkcg part of request_queue
624 * @q: request_queue to drain
626 * Called from blk_drain_queue(). Responsible for draining blkcg part.
628 void blkcg_drain_queue(struct request_queue *q)
630 lockdep_assert_held(q->queue_lock);
636 * blkcg_exit_queue - exit and release blkcg part of request_queue
637 * @q: request_queue being released
639 * Called from blk_release_queue(). Responsible for exiting blkcg part.
641 void blkcg_exit_queue(struct request_queue *q)
643 spin_lock_irq(q->queue_lock);
645 spin_unlock_irq(q->queue_lock);
651 * We cannot support shared io contexts, as we have no mean to support
652 * two tasks with the same ioc in two different groups without major rework
653 * of the main cic data structures. For now we allow a task to change
654 * its cgroup only if it's the only owner of its ioc.
656 static int blkcg_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
658 struct task_struct *task;
659 struct io_context *ioc;
662 /* task_lock() is needed to avoid races with exit_io_context() */
663 cgroup_taskset_for_each(task, cgrp, tset) {
665 ioc = task->io_context;
666 if (ioc && atomic_read(&ioc->nr_tasks) > 1)
675 struct cgroup_subsys blkio_subsys = {
677 .create = blkcg_create,
678 .can_attach = blkcg_can_attach,
679 .pre_destroy = blkcg_pre_destroy,
680 .destroy = blkcg_destroy,
681 .subsys_id = blkio_subsys_id,
682 .base_cftypes = blkcg_files,
683 .module = THIS_MODULE,
685 EXPORT_SYMBOL_GPL(blkio_subsys);
688 * blkcg_activate_policy - activate a blkcg policy on a request_queue
689 * @q: request_queue of interest
690 * @pol: blkcg policy to activate
692 * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through
693 * bypass mode to populate its blkgs with policy_data for @pol.
695 * Activation happens with @q bypassed, so nobody would be accessing blkgs
696 * from IO path. Update of each blkg is protected by both queue and blkcg
697 * locks so that holding either lock and testing blkcg_policy_enabled() is
698 * always enough for dereferencing policy data.
700 * The caller is responsible for synchronizing [de]activations and policy
701 * [un]registerations. Returns 0 on success, -errno on failure.
703 int blkcg_activate_policy(struct request_queue *q,
704 const struct blkcg_policy *pol)
707 struct blkcg_gq *blkg;
708 struct blkg_policy_data *pd, *n;
711 if (blkcg_policy_enabled(q, pol))
714 blk_queue_bypass_start(q);
716 /* make sure the root blkg exists and count the existing blkgs */
717 spin_lock_irq(q->queue_lock);
720 blkg = __blkg_lookup_create(&blkcg_root, q);
729 list_for_each_entry(blkg, &q->blkg_list, q_node)
732 spin_unlock_irq(q->queue_lock);
734 /* allocate policy_data for all existing blkgs */
736 pd = kzalloc_node(blkg_pd_size(pol), GFP_KERNEL, q->node);
741 list_add_tail(&pd->alloc_node, &pds);
745 * Install the allocated pds. With @q bypassing, no new blkg
746 * should have been created while the queue lock was dropped.
748 spin_lock_irq(q->queue_lock);
750 list_for_each_entry(blkg, &q->blkg_list, q_node) {
751 if (WARN_ON(list_empty(&pds))) {
752 /* umm... this shouldn't happen, just abort */
756 pd = list_first_entry(&pds, struct blkg_policy_data, alloc_node);
757 list_del_init(&pd->alloc_node);
759 /* grab blkcg lock too while installing @pd on @blkg */
760 spin_lock(&blkg->blkcg->lock);
762 blkg->pd[pol->plid] = pd;
764 pol->ops.pd_init_fn(blkg);
766 spin_unlock(&blkg->blkcg->lock);
769 __set_bit(pol->plid, q->blkcg_pols);
772 spin_unlock_irq(q->queue_lock);
774 blk_queue_bypass_end(q);
775 list_for_each_entry_safe(pd, n, &pds, alloc_node)
779 EXPORT_SYMBOL_GPL(blkcg_activate_policy);
782 * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
783 * @q: request_queue of interest
784 * @pol: blkcg policy to deactivate
786 * Deactivate @pol on @q. Follows the same synchronization rules as
787 * blkcg_activate_policy().
789 void blkcg_deactivate_policy(struct request_queue *q,
790 const struct blkcg_policy *pol)
792 struct blkcg_gq *blkg;
794 if (!blkcg_policy_enabled(q, pol))
797 blk_queue_bypass_start(q);
798 spin_lock_irq(q->queue_lock);
800 __clear_bit(pol->plid, q->blkcg_pols);
802 /* if no policy is left, no need for blkgs - shoot them down */
803 if (bitmap_empty(q->blkcg_pols, BLKCG_MAX_POLS))
806 list_for_each_entry(blkg, &q->blkg_list, q_node) {
807 /* grab blkcg lock too while removing @pd from @blkg */
808 spin_lock(&blkg->blkcg->lock);
810 if (pol->ops.pd_exit_fn)
811 pol->ops.pd_exit_fn(blkg);
813 kfree(blkg->pd[pol->plid]);
814 blkg->pd[pol->plid] = NULL;
816 spin_unlock(&blkg->blkcg->lock);
819 spin_unlock_irq(q->queue_lock);
820 blk_queue_bypass_end(q);
822 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
825 * blkcg_policy_register - register a blkcg policy
826 * @pol: blkcg policy to register
828 * Register @pol with blkcg core. Might sleep and @pol may be modified on
829 * successful registration. Returns 0 on success and -errno on failure.
831 int blkcg_policy_register(struct blkcg_policy *pol)
835 mutex_lock(&blkcg_pol_mutex);
837 /* find an empty slot */
839 for (i = 0; i < BLKCG_MAX_POLS; i++)
840 if (!blkcg_policy[i])
842 if (i >= BLKCG_MAX_POLS)
845 /* register and update blkgs */
847 blkcg_policy[i] = pol;
849 /* everything is in place, add intf files for the new policy */
851 WARN_ON(cgroup_add_cftypes(&blkio_subsys, pol->cftypes));
854 mutex_unlock(&blkcg_pol_mutex);
857 EXPORT_SYMBOL_GPL(blkcg_policy_register);
860 * blkcg_policy_unregister - unregister a blkcg policy
861 * @pol: blkcg policy to unregister
863 * Undo blkcg_policy_register(@pol). Might sleep.
865 void blkcg_policy_unregister(struct blkcg_policy *pol)
867 mutex_lock(&blkcg_pol_mutex);
869 if (WARN_ON(blkcg_policy[pol->plid] != pol))
872 /* kill the intf files first */
874 cgroup_rm_cftypes(&blkio_subsys, pol->cftypes);
876 /* unregister and update blkgs */
877 blkcg_policy[pol->plid] = NULL;
879 mutex_unlock(&blkcg_pol_mutex);
881 EXPORT_SYMBOL_GPL(blkcg_policy_unregister);