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 static bool blkcg_policy_enabled(struct request_queue *q,
35 const struct blkcg_policy *pol)
37 return pol && test_bit(pol->plid, q->blkcg_pols);
41 * blkg_free - free a blkg
44 * Free @blkg which may be partially allocated.
46 static void blkg_free(struct blkcg_gq *blkg)
53 for (i = 0; i < BLKCG_MAX_POLS; i++) {
54 struct blkcg_policy *pol = blkcg_policy[i];
55 struct blkg_policy_data *pd = blkg->pd[i];
60 if (pol && pol->pd_exit_fn)
61 pol->pd_exit_fn(blkg);
66 blk_exit_rl(&blkg->rl);
71 * blkg_alloc - allocate a blkg
72 * @blkcg: block cgroup the new blkg is associated with
73 * @q: request_queue the new blkg is associated with
74 * @gfp_mask: allocation mask to use
76 * Allocate a new blkg assocating @blkcg and @q.
78 static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
81 struct blkcg_gq *blkg;
84 /* alloc and init base part */
85 blkg = kzalloc_node(sizeof(*blkg), gfp_mask, q->node);
90 INIT_LIST_HEAD(&blkg->q_node);
94 /* root blkg uses @q->root_rl, init rl only for !root blkgs */
95 if (blkcg != &blkcg_root) {
96 if (blk_init_rl(&blkg->rl, q, gfp_mask))
101 for (i = 0; i < BLKCG_MAX_POLS; i++) {
102 struct blkcg_policy *pol = blkcg_policy[i];
103 struct blkg_policy_data *pd;
105 if (!blkcg_policy_enabled(q, pol))
108 /* alloc per-policy data and attach it to blkg */
109 pd = kzalloc_node(pol->pd_size, gfp_mask, q->node);
116 /* invoke per-policy init */
118 pol->pd_init_fn(blkg);
128 static struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg,
129 struct request_queue *q, bool update_hint)
131 struct blkcg_gq *blkg;
133 blkg = rcu_dereference(blkcg->blkg_hint);
134 if (blkg && blkg->q == q)
138 * Hint didn't match. Look up from the radix tree. Note that the
139 * hint can only be updated under queue_lock as otherwise @blkg
140 * could have already been removed from blkg_tree. The caller is
141 * responsible for grabbing queue_lock if @update_hint.
143 blkg = radix_tree_lookup(&blkcg->blkg_tree, q->id);
144 if (blkg && blkg->q == q) {
146 lockdep_assert_held(q->queue_lock);
147 rcu_assign_pointer(blkcg->blkg_hint, blkg);
156 * blkg_lookup - lookup blkg for the specified blkcg - q pair
157 * @blkcg: blkcg of interest
158 * @q: request_queue of interest
160 * Lookup blkg for the @blkcg - @q pair. This function should be called
161 * under RCU read lock and is guaranteed to return %NULL if @q is bypassing
162 * - see blk_queue_bypass_start() for details.
164 struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, struct request_queue *q)
166 WARN_ON_ONCE(!rcu_read_lock_held());
168 if (unlikely(blk_queue_bypass(q)))
170 return __blkg_lookup(blkcg, q, false);
172 EXPORT_SYMBOL_GPL(blkg_lookup);
175 * If @new_blkg is %NULL, this function tries to allocate a new one as
176 * necessary using %GFP_ATOMIC. @new_blkg is always consumed on return.
178 static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
179 struct request_queue *q,
180 struct blkcg_gq *new_blkg)
182 struct blkcg_gq *blkg;
185 WARN_ON_ONCE(!rcu_read_lock_held());
186 lockdep_assert_held(q->queue_lock);
188 /* blkg holds a reference to blkcg */
189 if (!css_tryget(&blkcg->css)) {
196 new_blkg = blkg_alloc(blkcg, q, GFP_ATOMIC);
197 if (unlikely(!new_blkg)) {
204 /* link parent and insert */
205 if (blkcg_parent(blkcg)) {
206 blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false);
207 if (WARN_ON_ONCE(!blkg->parent)) {
208 blkg = ERR_PTR(-EINVAL);
211 blkg_get(blkg->parent);
214 spin_lock(&blkcg->lock);
215 ret = radix_tree_insert(&blkcg->blkg_tree, q->id, blkg);
217 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
218 list_add(&blkg->q_node, &q->blkg_list);
220 spin_unlock(&blkcg->lock);
225 /* @blkg failed fully initialized, use the usual release path */
230 css_put(&blkcg->css);
237 * blkg_lookup_create - lookup blkg, try to create one if not there
238 * @blkcg: blkcg of interest
239 * @q: request_queue of interest
241 * Lookup blkg for the @blkcg - @q pair. If it doesn't exist, try to
242 * create one. blkg creation is performed recursively from blkcg_root such
243 * that all non-root blkg's have access to the parent blkg. This function
244 * should be called under RCU read lock and @q->queue_lock.
246 * Returns pointer to the looked up or created blkg on success, ERR_PTR()
247 * value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not
248 * dead and bypassing, returns ERR_PTR(-EBUSY).
250 struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
251 struct request_queue *q)
253 struct blkcg_gq *blkg;
255 WARN_ON_ONCE(!rcu_read_lock_held());
256 lockdep_assert_held(q->queue_lock);
259 * This could be the first entry point of blkcg implementation and
260 * we shouldn't allow anything to go through for a bypassing queue.
262 if (unlikely(blk_queue_bypass(q)))
263 return ERR_PTR(blk_queue_dying(q) ? -EINVAL : -EBUSY);
265 blkg = __blkg_lookup(blkcg, q, true);
270 * Create blkgs walking down from blkcg_root to @blkcg, so that all
271 * non-root blkgs have access to their parents.
274 struct blkcg *pos = blkcg;
275 struct blkcg *parent = blkcg_parent(blkcg);
277 while (parent && !__blkg_lookup(parent, q, false)) {
279 parent = blkcg_parent(parent);
282 blkg = blkg_create(pos, q, NULL);
283 if (pos == blkcg || IS_ERR(blkg))
287 EXPORT_SYMBOL_GPL(blkg_lookup_create);
289 static void blkg_destroy(struct blkcg_gq *blkg)
291 struct blkcg *blkcg = blkg->blkcg;
293 lockdep_assert_held(blkg->q->queue_lock);
294 lockdep_assert_held(&blkcg->lock);
296 /* Something wrong if we are trying to remove same group twice */
297 WARN_ON_ONCE(list_empty(&blkg->q_node));
298 WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
300 radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
301 list_del_init(&blkg->q_node);
302 hlist_del_init_rcu(&blkg->blkcg_node);
305 * Both setting lookup hint to and clearing it from @blkg are done
306 * under queue_lock. If it's not pointing to @blkg now, it never
307 * will. Hint assignment itself can race safely.
309 if (rcu_dereference_raw(blkcg->blkg_hint) == blkg)
310 rcu_assign_pointer(blkcg->blkg_hint, NULL);
313 * Put the reference taken at the time of creation so that when all
314 * queues are gone, group can be destroyed.
320 * blkg_destroy_all - destroy all blkgs associated with a request_queue
321 * @q: request_queue of interest
323 * Destroy all blkgs associated with @q.
325 static void blkg_destroy_all(struct request_queue *q)
327 struct blkcg_gq *blkg, *n;
329 lockdep_assert_held(q->queue_lock);
331 list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
332 struct blkcg *blkcg = blkg->blkcg;
334 spin_lock(&blkcg->lock);
336 spin_unlock(&blkcg->lock);
340 * root blkg is destroyed. Just clear the pointer since
341 * root_rl does not take reference on root blkg.
344 q->root_rl.blkg = NULL;
347 static void blkg_rcu_free(struct rcu_head *rcu_head)
349 blkg_free(container_of(rcu_head, struct blkcg_gq, rcu_head));
352 void __blkg_release(struct blkcg_gq *blkg)
354 /* release the blkcg and parent blkg refs this blkg has been holding */
355 css_put(&blkg->blkcg->css);
357 blkg_put(blkg->parent);
360 * A group is freed in rcu manner. But having an rcu lock does not
361 * mean that one can access all the fields of blkg and assume these
362 * are valid. For example, don't try to follow throtl_data and
363 * request queue links.
365 * Having a reference to blkg under an rcu allows acess to only
366 * values local to groups like group stats and group rate limits
368 call_rcu(&blkg->rcu_head, blkg_rcu_free);
370 EXPORT_SYMBOL_GPL(__blkg_release);
373 * The next function used by blk_queue_for_each_rl(). It's a bit tricky
374 * because the root blkg uses @q->root_rl instead of its own rl.
376 struct request_list *__blk_queue_next_rl(struct request_list *rl,
377 struct request_queue *q)
379 struct list_head *ent;
380 struct blkcg_gq *blkg;
383 * Determine the current blkg list_head. The first entry is
384 * root_rl which is off @q->blkg_list and mapped to the head.
386 if (rl == &q->root_rl) {
388 /* There are no more block groups, hence no request lists */
392 blkg = container_of(rl, struct blkcg_gq, rl);
396 /* walk to the next list_head, skip root blkcg */
398 if (ent == &q->root_blkg->q_node)
400 if (ent == &q->blkg_list)
403 blkg = container_of(ent, struct blkcg_gq, q_node);
407 static int blkcg_reset_stats(struct cgroup *cgroup, struct cftype *cftype,
410 struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
411 struct blkcg_gq *blkg;
412 struct hlist_node *n;
415 mutex_lock(&blkcg_pol_mutex);
416 spin_lock_irq(&blkcg->lock);
419 * Note that stat reset is racy - it doesn't synchronize against
420 * stat updates. This is a debug feature which shouldn't exist
421 * anyway. If you get hit by a race, retry.
423 hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
424 for (i = 0; i < BLKCG_MAX_POLS; i++) {
425 struct blkcg_policy *pol = blkcg_policy[i];
427 if (blkcg_policy_enabled(blkg->q, pol) &&
428 pol->pd_reset_stats_fn)
429 pol->pd_reset_stats_fn(blkg);
433 spin_unlock_irq(&blkcg->lock);
434 mutex_unlock(&blkcg_pol_mutex);
438 static const char *blkg_dev_name(struct blkcg_gq *blkg)
440 /* some drivers (floppy) instantiate a queue w/o disk registered */
441 if (blkg->q->backing_dev_info.dev)
442 return dev_name(blkg->q->backing_dev_info.dev);
447 * blkcg_print_blkgs - helper for printing per-blkg data
448 * @sf: seq_file to print to
449 * @blkcg: blkcg of interest
450 * @prfill: fill function to print out a blkg
451 * @pol: policy in question
452 * @data: data to be passed to @prfill
453 * @show_total: to print out sum of prfill return values or not
455 * This function invokes @prfill on each blkg of @blkcg if pd for the
456 * policy specified by @pol exists. @prfill is invoked with @sf, the
457 * policy data and @data. If @show_total is %true, the sum of the return
458 * values from @prfill is printed with "Total" label at the end.
460 * This is to be used to construct print functions for
461 * cftype->read_seq_string method.
463 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
464 u64 (*prfill)(struct seq_file *,
465 struct blkg_policy_data *, int),
466 const struct blkcg_policy *pol, int data,
469 struct blkcg_gq *blkg;
470 struct hlist_node *n;
473 spin_lock_irq(&blkcg->lock);
474 hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
475 if (blkcg_policy_enabled(blkg->q, pol))
476 total += prfill(sf, blkg->pd[pol->plid], data);
477 spin_unlock_irq(&blkcg->lock);
480 seq_printf(sf, "Total %llu\n", (unsigned long long)total);
482 EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
485 * __blkg_prfill_u64 - prfill helper for a single u64 value
486 * @sf: seq_file to print to
487 * @pd: policy private data of interest
490 * Print @v to @sf for the device assocaited with @pd.
492 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
494 const char *dname = blkg_dev_name(pd->blkg);
499 seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
502 EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
505 * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
506 * @sf: seq_file to print to
507 * @pd: policy private data of interest
508 * @rwstat: rwstat to print
510 * Print @rwstat to @sf for the device assocaited with @pd.
512 u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
513 const struct blkg_rwstat *rwstat)
515 static const char *rwstr[] = {
516 [BLKG_RWSTAT_READ] = "Read",
517 [BLKG_RWSTAT_WRITE] = "Write",
518 [BLKG_RWSTAT_SYNC] = "Sync",
519 [BLKG_RWSTAT_ASYNC] = "Async",
521 const char *dname = blkg_dev_name(pd->blkg);
528 for (i = 0; i < BLKG_RWSTAT_NR; i++)
529 seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
530 (unsigned long long)rwstat->cnt[i]);
532 v = rwstat->cnt[BLKG_RWSTAT_READ] + rwstat->cnt[BLKG_RWSTAT_WRITE];
533 seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
538 * blkg_prfill_stat - prfill callback for blkg_stat
539 * @sf: seq_file to print to
540 * @pd: policy private data of interest
541 * @off: offset to the blkg_stat in @pd
543 * prfill callback for printing a blkg_stat.
545 u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off)
547 return __blkg_prfill_u64(sf, pd, blkg_stat_read((void *)pd + off));
549 EXPORT_SYMBOL_GPL(blkg_prfill_stat);
552 * blkg_prfill_rwstat - prfill callback for blkg_rwstat
553 * @sf: seq_file to print to
554 * @pd: policy private data of interest
555 * @off: offset to the blkg_rwstat in @pd
557 * prfill callback for printing a blkg_rwstat.
559 u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
562 struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd + off);
564 return __blkg_prfill_rwstat(sf, pd, &rwstat);
566 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
569 * blkg_conf_prep - parse and prepare for per-blkg config update
570 * @blkcg: target block cgroup
571 * @pol: target policy
572 * @input: input string
573 * @ctx: blkg_conf_ctx to be filled
575 * Parse per-blkg config update from @input and initialize @ctx with the
576 * result. @ctx->blkg points to the blkg to be updated and @ctx->v the new
577 * value. This function returns with RCU read lock and queue lock held and
578 * must be paired with blkg_conf_finish().
580 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
581 const char *input, struct blkg_conf_ctx *ctx)
582 __acquires(rcu) __acquires(disk->queue->queue_lock)
584 struct gendisk *disk;
585 struct blkcg_gq *blkg;
586 unsigned int major, minor;
587 unsigned long long v;
590 if (sscanf(input, "%u:%u %llu", &major, &minor, &v) != 3)
593 disk = get_gendisk(MKDEV(major, minor), &part);
598 spin_lock_irq(disk->queue->queue_lock);
600 if (blkcg_policy_enabled(disk->queue, pol))
601 blkg = blkg_lookup_create(blkcg, disk->queue);
603 blkg = ERR_PTR(-EINVAL);
608 spin_unlock_irq(disk->queue->queue_lock);
611 * If queue was bypassing, we should retry. Do so after a
612 * short msleep(). It isn't strictly necessary but queue
613 * can be bypassing for some time and it's always nice to
614 * avoid busy looping.
618 ret = restart_syscall();
628 EXPORT_SYMBOL_GPL(blkg_conf_prep);
631 * blkg_conf_finish - finish up per-blkg config update
632 * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
634 * Finish up after per-blkg config update. This function must be paired
635 * with blkg_conf_prep().
637 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
638 __releases(ctx->disk->queue->queue_lock) __releases(rcu)
640 spin_unlock_irq(ctx->disk->queue->queue_lock);
644 EXPORT_SYMBOL_GPL(blkg_conf_finish);
646 struct cftype blkcg_files[] = {
648 .name = "reset_stats",
649 .write_u64 = blkcg_reset_stats,
655 * blkcg_css_offline - cgroup css_offline callback
656 * @cgroup: cgroup of interest
658 * This function is called when @cgroup is about to go away and responsible
659 * for shooting down all blkgs associated with @cgroup. blkgs should be
660 * removed while holding both q and blkcg locks. As blkcg lock is nested
661 * inside q lock, this function performs reverse double lock dancing.
663 * This is the blkcg counterpart of ioc_release_fn().
665 static void blkcg_css_offline(struct cgroup *cgroup)
667 struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
669 spin_lock_irq(&blkcg->lock);
671 while (!hlist_empty(&blkcg->blkg_list)) {
672 struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
673 struct blkcg_gq, blkcg_node);
674 struct request_queue *q = blkg->q;
676 if (spin_trylock(q->queue_lock)) {
678 spin_unlock(q->queue_lock);
680 spin_unlock_irq(&blkcg->lock);
682 spin_lock_irq(&blkcg->lock);
686 spin_unlock_irq(&blkcg->lock);
689 static void blkcg_css_free(struct cgroup *cgroup)
691 struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
693 if (blkcg != &blkcg_root)
697 static struct cgroup_subsys_state *blkcg_css_alloc(struct cgroup *cgroup)
699 static atomic64_t id_seq = ATOMIC64_INIT(0);
701 struct cgroup *parent = cgroup->parent;
708 blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
710 return ERR_PTR(-ENOMEM);
712 blkcg->cfq_weight = CFQ_WEIGHT_DEFAULT;
713 blkcg->id = atomic64_inc_return(&id_seq); /* root is 0, start from 1 */
715 spin_lock_init(&blkcg->lock);
716 INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_ATOMIC);
717 INIT_HLIST_HEAD(&blkcg->blkg_list);
723 * blkcg_init_queue - initialize blkcg part of request queue
724 * @q: request_queue to initialize
726 * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
727 * part of new request_queue @q.
730 * 0 on success, -errno on failure.
732 int blkcg_init_queue(struct request_queue *q)
736 return blk_throtl_init(q);
740 * blkcg_drain_queue - drain blkcg part of request_queue
741 * @q: request_queue to drain
743 * Called from blk_drain_queue(). Responsible for draining blkcg part.
745 void blkcg_drain_queue(struct request_queue *q)
747 lockdep_assert_held(q->queue_lock);
753 * blkcg_exit_queue - exit and release blkcg part of request_queue
754 * @q: request_queue being released
756 * Called from blk_release_queue(). Responsible for exiting blkcg part.
758 void blkcg_exit_queue(struct request_queue *q)
760 spin_lock_irq(q->queue_lock);
762 spin_unlock_irq(q->queue_lock);
768 * We cannot support shared io contexts, as we have no mean to support
769 * two tasks with the same ioc in two different groups without major rework
770 * of the main cic data structures. For now we allow a task to change
771 * its cgroup only if it's the only owner of its ioc.
773 static int blkcg_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
775 struct task_struct *task;
776 struct io_context *ioc;
779 /* task_lock() is needed to avoid races with exit_io_context() */
780 cgroup_taskset_for_each(task, cgrp, tset) {
782 ioc = task->io_context;
783 if (ioc && atomic_read(&ioc->nr_tasks) > 1)
792 struct cgroup_subsys blkio_subsys = {
794 .css_alloc = blkcg_css_alloc,
795 .css_offline = blkcg_css_offline,
796 .css_free = blkcg_css_free,
797 .can_attach = blkcg_can_attach,
798 .subsys_id = blkio_subsys_id,
799 .base_cftypes = blkcg_files,
800 .module = THIS_MODULE,
803 * blkio subsystem is utterly broken in terms of hierarchy support.
804 * It treats all cgroups equally regardless of where they're
805 * located in the hierarchy - all cgroups are treated as if they're
806 * right below the root. Fix it and remove the following.
808 .broken_hierarchy = true,
810 EXPORT_SYMBOL_GPL(blkio_subsys);
813 * blkcg_activate_policy - activate a blkcg policy on a request_queue
814 * @q: request_queue of interest
815 * @pol: blkcg policy to activate
817 * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through
818 * bypass mode to populate its blkgs with policy_data for @pol.
820 * Activation happens with @q bypassed, so nobody would be accessing blkgs
821 * from IO path. Update of each blkg is protected by both queue and blkcg
822 * locks so that holding either lock and testing blkcg_policy_enabled() is
823 * always enough for dereferencing policy data.
825 * The caller is responsible for synchronizing [de]activations and policy
826 * [un]registerations. Returns 0 on success, -errno on failure.
828 int blkcg_activate_policy(struct request_queue *q,
829 const struct blkcg_policy *pol)
832 struct blkcg_gq *blkg, *new_blkg;
833 struct blkg_policy_data *pd, *n;
837 if (blkcg_policy_enabled(q, pol))
840 /* preallocations for root blkg */
841 new_blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
845 preloaded = !radix_tree_preload(GFP_KERNEL);
847 blk_queue_bypass_start(q);
850 * Make sure the root blkg exists and count the existing blkgs. As
851 * @q is bypassing at this point, blkg_lookup_create() can't be
852 * used. Open code it.
854 spin_lock_irq(q->queue_lock);
857 blkg = __blkg_lookup(&blkcg_root, q, false);
861 blkg = blkg_create(&blkcg_root, q, new_blkg);
865 radix_tree_preload_end();
872 q->root_rl.blkg = blkg;
874 list_for_each_entry(blkg, &q->blkg_list, q_node)
877 spin_unlock_irq(q->queue_lock);
879 /* allocate policy_data for all existing blkgs */
881 pd = kzalloc_node(pol->pd_size, GFP_KERNEL, q->node);
886 list_add_tail(&pd->alloc_node, &pds);
890 * Install the allocated pds. With @q bypassing, no new blkg
891 * should have been created while the queue lock was dropped.
893 spin_lock_irq(q->queue_lock);
895 list_for_each_entry(blkg, &q->blkg_list, q_node) {
896 if (WARN_ON(list_empty(&pds))) {
897 /* umm... this shouldn't happen, just abort */
901 pd = list_first_entry(&pds, struct blkg_policy_data, alloc_node);
902 list_del_init(&pd->alloc_node);
904 /* grab blkcg lock too while installing @pd on @blkg */
905 spin_lock(&blkg->blkcg->lock);
907 blkg->pd[pol->plid] = pd;
909 pol->pd_init_fn(blkg);
911 spin_unlock(&blkg->blkcg->lock);
914 __set_bit(pol->plid, q->blkcg_pols);
917 spin_unlock_irq(q->queue_lock);
919 blk_queue_bypass_end(q);
920 list_for_each_entry_safe(pd, n, &pds, alloc_node)
924 EXPORT_SYMBOL_GPL(blkcg_activate_policy);
927 * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
928 * @q: request_queue of interest
929 * @pol: blkcg policy to deactivate
931 * Deactivate @pol on @q. Follows the same synchronization rules as
932 * blkcg_activate_policy().
934 void blkcg_deactivate_policy(struct request_queue *q,
935 const struct blkcg_policy *pol)
937 struct blkcg_gq *blkg;
939 if (!blkcg_policy_enabled(q, pol))
942 blk_queue_bypass_start(q);
943 spin_lock_irq(q->queue_lock);
945 __clear_bit(pol->plid, q->blkcg_pols);
947 /* if no policy is left, no need for blkgs - shoot them down */
948 if (bitmap_empty(q->blkcg_pols, BLKCG_MAX_POLS))
951 list_for_each_entry(blkg, &q->blkg_list, q_node) {
952 /* grab blkcg lock too while removing @pd from @blkg */
953 spin_lock(&blkg->blkcg->lock);
956 pol->pd_exit_fn(blkg);
958 kfree(blkg->pd[pol->plid]);
959 blkg->pd[pol->plid] = NULL;
961 spin_unlock(&blkg->blkcg->lock);
964 spin_unlock_irq(q->queue_lock);
965 blk_queue_bypass_end(q);
967 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
970 * blkcg_policy_register - register a blkcg policy
971 * @pol: blkcg policy to register
973 * Register @pol with blkcg core. Might sleep and @pol may be modified on
974 * successful registration. Returns 0 on success and -errno on failure.
976 int blkcg_policy_register(struct blkcg_policy *pol)
980 if (WARN_ON(pol->pd_size < sizeof(struct blkg_policy_data)))
983 mutex_lock(&blkcg_pol_mutex);
985 /* find an empty slot */
987 for (i = 0; i < BLKCG_MAX_POLS; i++)
988 if (!blkcg_policy[i])
990 if (i >= BLKCG_MAX_POLS)
993 /* register and update blkgs */
995 blkcg_policy[i] = pol;
997 /* everything is in place, add intf files for the new policy */
999 WARN_ON(cgroup_add_cftypes(&blkio_subsys, pol->cftypes));
1002 mutex_unlock(&blkcg_pol_mutex);
1005 EXPORT_SYMBOL_GPL(blkcg_policy_register);
1008 * blkcg_policy_unregister - unregister a blkcg policy
1009 * @pol: blkcg policy to unregister
1011 * Undo blkcg_policy_register(@pol). Might sleep.
1013 void blkcg_policy_unregister(struct blkcg_policy *pol)
1015 mutex_lock(&blkcg_pol_mutex);
1017 if (WARN_ON(blkcg_policy[pol->plid] != pol))
1020 /* kill the intf files first */
1022 cgroup_rm_cftypes(&blkio_subsys, pol->cftypes);
1024 /* unregister and update blkgs */
1025 blkcg_policy[pol->plid] = NULL;
1027 mutex_unlock(&blkcg_pol_mutex);
1029 EXPORT_SYMBOL_GPL(blkcg_policy_unregister);