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 .cfq_leaf_weight = 2 * CFQ_WEIGHT_DEFAULT, };
31 EXPORT_SYMBOL_GPL(blkcg_root);
33 static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];
35 static bool blkcg_policy_enabled(struct request_queue *q,
36 const struct blkcg_policy *pol)
38 return pol && test_bit(pol->plid, q->blkcg_pols);
42 * blkg_free - free a blkg
45 * Free @blkg which may be partially allocated.
47 static void blkg_free(struct blkcg_gq *blkg)
54 for (i = 0; i < BLKCG_MAX_POLS; i++) {
55 struct blkcg_policy *pol = blkcg_policy[i];
56 struct blkg_policy_data *pd = blkg->pd[i];
61 if (pol && pol->pd_exit_fn)
62 pol->pd_exit_fn(blkg);
67 blk_exit_rl(&blkg->rl);
72 * blkg_alloc - allocate a blkg
73 * @blkcg: block cgroup the new blkg is associated with
74 * @q: request_queue the new blkg is associated with
75 * @gfp_mask: allocation mask to use
77 * Allocate a new blkg assocating @blkcg and @q.
79 static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
82 struct blkcg_gq *blkg;
85 /* alloc and init base part */
86 blkg = kzalloc_node(sizeof(*blkg), gfp_mask, q->node);
91 INIT_LIST_HEAD(&blkg->q_node);
95 /* root blkg uses @q->root_rl, init rl only for !root blkgs */
96 if (blkcg != &blkcg_root) {
97 if (blk_init_rl(&blkg->rl, q, gfp_mask))
102 for (i = 0; i < BLKCG_MAX_POLS; i++) {
103 struct blkcg_policy *pol = blkcg_policy[i];
104 struct blkg_policy_data *pd;
106 if (!blkcg_policy_enabled(q, pol))
109 /* alloc per-policy data and attach it to blkg */
110 pd = kzalloc_node(pol->pd_size, gfp_mask, q->node);
118 /* invoke per-policy init */
120 pol->pd_init_fn(blkg);
130 static struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg,
131 struct request_queue *q, bool update_hint)
133 struct blkcg_gq *blkg;
135 blkg = rcu_dereference(blkcg->blkg_hint);
136 if (blkg && blkg->q == q)
140 * Hint didn't match. Look up from the radix tree. Note that the
141 * hint can only be updated under queue_lock as otherwise @blkg
142 * could have already been removed from blkg_tree. The caller is
143 * responsible for grabbing queue_lock if @update_hint.
145 blkg = radix_tree_lookup(&blkcg->blkg_tree, q->id);
146 if (blkg && blkg->q == q) {
148 lockdep_assert_held(q->queue_lock);
149 rcu_assign_pointer(blkcg->blkg_hint, blkg);
158 * blkg_lookup - lookup blkg for the specified blkcg - q pair
159 * @blkcg: blkcg of interest
160 * @q: request_queue of interest
162 * Lookup blkg for the @blkcg - @q pair. This function should be called
163 * under RCU read lock and is guaranteed to return %NULL if @q is bypassing
164 * - see blk_queue_bypass_start() for details.
166 struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, struct request_queue *q)
168 WARN_ON_ONCE(!rcu_read_lock_held());
170 if (unlikely(blk_queue_bypass(q)))
172 return __blkg_lookup(blkcg, q, false);
174 EXPORT_SYMBOL_GPL(blkg_lookup);
177 * If @new_blkg is %NULL, this function tries to allocate a new one as
178 * necessary using %GFP_ATOMIC. @new_blkg is always consumed on return.
180 static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
181 struct request_queue *q,
182 struct blkcg_gq *new_blkg)
184 struct blkcg_gq *blkg;
187 WARN_ON_ONCE(!rcu_read_lock_held());
188 lockdep_assert_held(q->queue_lock);
190 /* blkg holds a reference to blkcg */
191 if (!css_tryget(&blkcg->css)) {
198 new_blkg = blkg_alloc(blkcg, q, GFP_ATOMIC);
199 if (unlikely(!new_blkg)) {
206 /* link parent and insert */
207 if (blkcg_parent(blkcg)) {
208 blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false);
209 if (WARN_ON_ONCE(!blkg->parent)) {
210 blkg = ERR_PTR(-EINVAL);
213 blkg_get(blkg->parent);
216 spin_lock(&blkcg->lock);
217 ret = radix_tree_insert(&blkcg->blkg_tree, q->id, blkg);
219 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
220 list_add(&blkg->q_node, &q->blkg_list);
222 for (i = 0; i < BLKCG_MAX_POLS; i++) {
223 struct blkcg_policy *pol = blkcg_policy[i];
225 if (blkg->pd[i] && pol->pd_online_fn)
226 pol->pd_online_fn(blkg);
230 spin_unlock(&blkcg->lock);
235 /* @blkg failed fully initialized, use the usual release path */
240 css_put(&blkcg->css);
247 * blkg_lookup_create - lookup blkg, try to create one if not there
248 * @blkcg: blkcg of interest
249 * @q: request_queue of interest
251 * Lookup blkg for the @blkcg - @q pair. If it doesn't exist, try to
252 * create one. blkg creation is performed recursively from blkcg_root such
253 * that all non-root blkg's have access to the parent blkg. This function
254 * should be called under RCU read lock and @q->queue_lock.
256 * Returns pointer to the looked up or created blkg on success, ERR_PTR()
257 * value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not
258 * dead and bypassing, returns ERR_PTR(-EBUSY).
260 struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
261 struct request_queue *q)
263 struct blkcg_gq *blkg;
265 WARN_ON_ONCE(!rcu_read_lock_held());
266 lockdep_assert_held(q->queue_lock);
269 * This could be the first entry point of blkcg implementation and
270 * we shouldn't allow anything to go through for a bypassing queue.
272 if (unlikely(blk_queue_bypass(q)))
273 return ERR_PTR(blk_queue_dying(q) ? -EINVAL : -EBUSY);
275 blkg = __blkg_lookup(blkcg, q, true);
280 * Create blkgs walking down from blkcg_root to @blkcg, so that all
281 * non-root blkgs have access to their parents.
284 struct blkcg *pos = blkcg;
285 struct blkcg *parent = blkcg_parent(blkcg);
287 while (parent && !__blkg_lookup(parent, q, false)) {
289 parent = blkcg_parent(parent);
292 blkg = blkg_create(pos, q, NULL);
293 if (pos == blkcg || IS_ERR(blkg))
297 EXPORT_SYMBOL_GPL(blkg_lookup_create);
299 static void blkg_destroy(struct blkcg_gq *blkg)
301 struct blkcg *blkcg = blkg->blkcg;
304 lockdep_assert_held(blkg->q->queue_lock);
305 lockdep_assert_held(&blkcg->lock);
307 /* Something wrong if we are trying to remove same group twice */
308 WARN_ON_ONCE(list_empty(&blkg->q_node));
309 WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
311 for (i = 0; i < BLKCG_MAX_POLS; i++) {
312 struct blkcg_policy *pol = blkcg_policy[i];
314 if (blkg->pd[i] && pol->pd_offline_fn)
315 pol->pd_offline_fn(blkg);
317 blkg->online = false;
319 radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
320 list_del_init(&blkg->q_node);
321 hlist_del_init_rcu(&blkg->blkcg_node);
324 * Both setting lookup hint to and clearing it from @blkg are done
325 * under queue_lock. If it's not pointing to @blkg now, it never
326 * will. Hint assignment itself can race safely.
328 if (rcu_dereference_raw(blkcg->blkg_hint) == blkg)
329 rcu_assign_pointer(blkcg->blkg_hint, NULL);
332 * Put the reference taken at the time of creation so that when all
333 * queues are gone, group can be destroyed.
339 * blkg_destroy_all - destroy all blkgs associated with a request_queue
340 * @q: request_queue of interest
342 * Destroy all blkgs associated with @q.
344 static void blkg_destroy_all(struct request_queue *q)
346 struct blkcg_gq *blkg, *n;
348 lockdep_assert_held(q->queue_lock);
350 list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
351 struct blkcg *blkcg = blkg->blkcg;
353 spin_lock(&blkcg->lock);
355 spin_unlock(&blkcg->lock);
359 * root blkg is destroyed. Just clear the pointer since
360 * root_rl does not take reference on root blkg.
363 q->root_rl.blkg = NULL;
366 static void blkg_rcu_free(struct rcu_head *rcu_head)
368 blkg_free(container_of(rcu_head, struct blkcg_gq, rcu_head));
371 void __blkg_release(struct blkcg_gq *blkg)
373 /* release the blkcg and parent blkg refs this blkg has been holding */
374 css_put(&blkg->blkcg->css);
376 blkg_put(blkg->parent);
379 * A group is freed in rcu manner. But having an rcu lock does not
380 * mean that one can access all the fields of blkg and assume these
381 * are valid. For example, don't try to follow throtl_data and
382 * request queue links.
384 * Having a reference to blkg under an rcu allows acess to only
385 * values local to groups like group stats and group rate limits
387 call_rcu(&blkg->rcu_head, blkg_rcu_free);
389 EXPORT_SYMBOL_GPL(__blkg_release);
392 * The next function used by blk_queue_for_each_rl(). It's a bit tricky
393 * because the root blkg uses @q->root_rl instead of its own rl.
395 struct request_list *__blk_queue_next_rl(struct request_list *rl,
396 struct request_queue *q)
398 struct list_head *ent;
399 struct blkcg_gq *blkg;
402 * Determine the current blkg list_head. The first entry is
403 * root_rl which is off @q->blkg_list and mapped to the head.
405 if (rl == &q->root_rl) {
407 /* There are no more block groups, hence no request lists */
411 blkg = container_of(rl, struct blkcg_gq, rl);
415 /* walk to the next list_head, skip root blkcg */
417 if (ent == &q->root_blkg->q_node)
419 if (ent == &q->blkg_list)
422 blkg = container_of(ent, struct blkcg_gq, q_node);
426 static int blkcg_reset_stats(struct cgroup *cgroup, struct cftype *cftype,
429 struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
430 struct blkcg_gq *blkg;
431 struct hlist_node *n;
434 mutex_lock(&blkcg_pol_mutex);
435 spin_lock_irq(&blkcg->lock);
438 * Note that stat reset is racy - it doesn't synchronize against
439 * stat updates. This is a debug feature which shouldn't exist
440 * anyway. If you get hit by a race, retry.
442 hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
443 for (i = 0; i < BLKCG_MAX_POLS; i++) {
444 struct blkcg_policy *pol = blkcg_policy[i];
446 if (blkcg_policy_enabled(blkg->q, pol) &&
447 pol->pd_reset_stats_fn)
448 pol->pd_reset_stats_fn(blkg);
452 spin_unlock_irq(&blkcg->lock);
453 mutex_unlock(&blkcg_pol_mutex);
457 static const char *blkg_dev_name(struct blkcg_gq *blkg)
459 /* some drivers (floppy) instantiate a queue w/o disk registered */
460 if (blkg->q->backing_dev_info.dev)
461 return dev_name(blkg->q->backing_dev_info.dev);
466 * blkcg_print_blkgs - helper for printing per-blkg data
467 * @sf: seq_file to print to
468 * @blkcg: blkcg of interest
469 * @prfill: fill function to print out a blkg
470 * @pol: policy in question
471 * @data: data to be passed to @prfill
472 * @show_total: to print out sum of prfill return values or not
474 * This function invokes @prfill on each blkg of @blkcg if pd for the
475 * policy specified by @pol exists. @prfill is invoked with @sf, the
476 * policy data and @data. If @show_total is %true, the sum of the return
477 * values from @prfill is printed with "Total" label at the end.
479 * This is to be used to construct print functions for
480 * cftype->read_seq_string method.
482 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
483 u64 (*prfill)(struct seq_file *,
484 struct blkg_policy_data *, int),
485 const struct blkcg_policy *pol, int data,
488 struct blkcg_gq *blkg;
489 struct hlist_node *n;
492 spin_lock_irq(&blkcg->lock);
493 hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
494 if (blkcg_policy_enabled(blkg->q, pol))
495 total += prfill(sf, blkg->pd[pol->plid], data);
496 spin_unlock_irq(&blkcg->lock);
499 seq_printf(sf, "Total %llu\n", (unsigned long long)total);
501 EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
504 * __blkg_prfill_u64 - prfill helper for a single u64 value
505 * @sf: seq_file to print to
506 * @pd: policy private data of interest
509 * Print @v to @sf for the device assocaited with @pd.
511 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
513 const char *dname = blkg_dev_name(pd->blkg);
518 seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
521 EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
524 * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
525 * @sf: seq_file to print to
526 * @pd: policy private data of interest
527 * @rwstat: rwstat to print
529 * Print @rwstat to @sf for the device assocaited with @pd.
531 u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
532 const struct blkg_rwstat *rwstat)
534 static const char *rwstr[] = {
535 [BLKG_RWSTAT_READ] = "Read",
536 [BLKG_RWSTAT_WRITE] = "Write",
537 [BLKG_RWSTAT_SYNC] = "Sync",
538 [BLKG_RWSTAT_ASYNC] = "Async",
540 const char *dname = blkg_dev_name(pd->blkg);
547 for (i = 0; i < BLKG_RWSTAT_NR; i++)
548 seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
549 (unsigned long long)rwstat->cnt[i]);
551 v = rwstat->cnt[BLKG_RWSTAT_READ] + rwstat->cnt[BLKG_RWSTAT_WRITE];
552 seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
555 EXPORT_SYMBOL_GPL(__blkg_prfill_rwstat);
558 * blkg_prfill_stat - prfill callback for blkg_stat
559 * @sf: seq_file to print to
560 * @pd: policy private data of interest
561 * @off: offset to the blkg_stat in @pd
563 * prfill callback for printing a blkg_stat.
565 u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off)
567 return __blkg_prfill_u64(sf, pd, blkg_stat_read((void *)pd + off));
569 EXPORT_SYMBOL_GPL(blkg_prfill_stat);
572 * blkg_prfill_rwstat - prfill callback for blkg_rwstat
573 * @sf: seq_file to print to
574 * @pd: policy private data of interest
575 * @off: offset to the blkg_rwstat in @pd
577 * prfill callback for printing a blkg_rwstat.
579 u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
582 struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd + off);
584 return __blkg_prfill_rwstat(sf, pd, &rwstat);
586 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
589 * blkg_conf_prep - parse and prepare for per-blkg config update
590 * @blkcg: target block cgroup
591 * @pol: target policy
592 * @input: input string
593 * @ctx: blkg_conf_ctx to be filled
595 * Parse per-blkg config update from @input and initialize @ctx with the
596 * result. @ctx->blkg points to the blkg to be updated and @ctx->v the new
597 * value. This function returns with RCU read lock and queue lock held and
598 * must be paired with blkg_conf_finish().
600 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
601 const char *input, struct blkg_conf_ctx *ctx)
602 __acquires(rcu) __acquires(disk->queue->queue_lock)
604 struct gendisk *disk;
605 struct blkcg_gq *blkg;
606 unsigned int major, minor;
607 unsigned long long v;
610 if (sscanf(input, "%u:%u %llu", &major, &minor, &v) != 3)
613 disk = get_gendisk(MKDEV(major, minor), &part);
618 spin_lock_irq(disk->queue->queue_lock);
620 if (blkcg_policy_enabled(disk->queue, pol))
621 blkg = blkg_lookup_create(blkcg, disk->queue);
623 blkg = ERR_PTR(-EINVAL);
628 spin_unlock_irq(disk->queue->queue_lock);
631 * If queue was bypassing, we should retry. Do so after a
632 * short msleep(). It isn't strictly necessary but queue
633 * can be bypassing for some time and it's always nice to
634 * avoid busy looping.
638 ret = restart_syscall();
648 EXPORT_SYMBOL_GPL(blkg_conf_prep);
651 * blkg_conf_finish - finish up per-blkg config update
652 * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
654 * Finish up after per-blkg config update. This function must be paired
655 * with blkg_conf_prep().
657 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
658 __releases(ctx->disk->queue->queue_lock) __releases(rcu)
660 spin_unlock_irq(ctx->disk->queue->queue_lock);
664 EXPORT_SYMBOL_GPL(blkg_conf_finish);
666 struct cftype blkcg_files[] = {
668 .name = "reset_stats",
669 .write_u64 = blkcg_reset_stats,
675 * blkcg_css_offline - cgroup css_offline callback
676 * @cgroup: cgroup of interest
678 * This function is called when @cgroup is about to go away and responsible
679 * for shooting down all blkgs associated with @cgroup. blkgs should be
680 * removed while holding both q and blkcg locks. As blkcg lock is nested
681 * inside q lock, this function performs reverse double lock dancing.
683 * This is the blkcg counterpart of ioc_release_fn().
685 static void blkcg_css_offline(struct cgroup *cgroup)
687 struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
689 spin_lock_irq(&blkcg->lock);
691 while (!hlist_empty(&blkcg->blkg_list)) {
692 struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
693 struct blkcg_gq, blkcg_node);
694 struct request_queue *q = blkg->q;
696 if (spin_trylock(q->queue_lock)) {
698 spin_unlock(q->queue_lock);
700 spin_unlock_irq(&blkcg->lock);
702 spin_lock_irq(&blkcg->lock);
706 spin_unlock_irq(&blkcg->lock);
709 static void blkcg_css_free(struct cgroup *cgroup)
711 struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
713 if (blkcg != &blkcg_root)
717 static struct cgroup_subsys_state *blkcg_css_alloc(struct cgroup *cgroup)
719 static atomic64_t id_seq = ATOMIC64_INIT(0);
721 struct cgroup *parent = cgroup->parent;
728 blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
730 return ERR_PTR(-ENOMEM);
732 blkcg->cfq_weight = CFQ_WEIGHT_DEFAULT;
733 blkcg->cfq_leaf_weight = CFQ_WEIGHT_DEFAULT;
734 blkcg->id = atomic64_inc_return(&id_seq); /* root is 0, start from 1 */
736 spin_lock_init(&blkcg->lock);
737 INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_ATOMIC);
738 INIT_HLIST_HEAD(&blkcg->blkg_list);
744 * blkcg_init_queue - initialize blkcg part of request queue
745 * @q: request_queue to initialize
747 * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
748 * part of new request_queue @q.
751 * 0 on success, -errno on failure.
753 int blkcg_init_queue(struct request_queue *q)
757 return blk_throtl_init(q);
761 * blkcg_drain_queue - drain blkcg part of request_queue
762 * @q: request_queue to drain
764 * Called from blk_drain_queue(). Responsible for draining blkcg part.
766 void blkcg_drain_queue(struct request_queue *q)
768 lockdep_assert_held(q->queue_lock);
774 * blkcg_exit_queue - exit and release blkcg part of request_queue
775 * @q: request_queue being released
777 * Called from blk_release_queue(). Responsible for exiting blkcg part.
779 void blkcg_exit_queue(struct request_queue *q)
781 spin_lock_irq(q->queue_lock);
783 spin_unlock_irq(q->queue_lock);
789 * We cannot support shared io contexts, as we have no mean to support
790 * two tasks with the same ioc in two different groups without major rework
791 * of the main cic data structures. For now we allow a task to change
792 * its cgroup only if it's the only owner of its ioc.
794 static int blkcg_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
796 struct task_struct *task;
797 struct io_context *ioc;
800 /* task_lock() is needed to avoid races with exit_io_context() */
801 cgroup_taskset_for_each(task, cgrp, tset) {
803 ioc = task->io_context;
804 if (ioc && atomic_read(&ioc->nr_tasks) > 1)
813 struct cgroup_subsys blkio_subsys = {
815 .css_alloc = blkcg_css_alloc,
816 .css_offline = blkcg_css_offline,
817 .css_free = blkcg_css_free,
818 .can_attach = blkcg_can_attach,
819 .subsys_id = blkio_subsys_id,
820 .base_cftypes = blkcg_files,
821 .module = THIS_MODULE,
824 * blkio subsystem is utterly broken in terms of hierarchy support.
825 * It treats all cgroups equally regardless of where they're
826 * located in the hierarchy - all cgroups are treated as if they're
827 * right below the root. Fix it and remove the following.
829 .broken_hierarchy = true,
831 EXPORT_SYMBOL_GPL(blkio_subsys);
834 * blkcg_activate_policy - activate a blkcg policy on a request_queue
835 * @q: request_queue of interest
836 * @pol: blkcg policy to activate
838 * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through
839 * bypass mode to populate its blkgs with policy_data for @pol.
841 * Activation happens with @q bypassed, so nobody would be accessing blkgs
842 * from IO path. Update of each blkg is protected by both queue and blkcg
843 * locks so that holding either lock and testing blkcg_policy_enabled() is
844 * always enough for dereferencing policy data.
846 * The caller is responsible for synchronizing [de]activations and policy
847 * [un]registerations. Returns 0 on success, -errno on failure.
849 int blkcg_activate_policy(struct request_queue *q,
850 const struct blkcg_policy *pol)
853 struct blkcg_gq *blkg, *new_blkg;
854 struct blkg_policy_data *pd, *n;
858 if (blkcg_policy_enabled(q, pol))
861 /* preallocations for root blkg */
862 new_blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
866 preloaded = !radix_tree_preload(GFP_KERNEL);
868 blk_queue_bypass_start(q);
871 * Make sure the root blkg exists and count the existing blkgs. As
872 * @q is bypassing at this point, blkg_lookup_create() can't be
873 * used. Open code it.
875 spin_lock_irq(q->queue_lock);
878 blkg = __blkg_lookup(&blkcg_root, q, false);
882 blkg = blkg_create(&blkcg_root, q, new_blkg);
886 radix_tree_preload_end();
893 q->root_rl.blkg = blkg;
895 list_for_each_entry(blkg, &q->blkg_list, q_node)
898 spin_unlock_irq(q->queue_lock);
900 /* allocate policy_data for all existing blkgs */
902 pd = kzalloc_node(pol->pd_size, GFP_KERNEL, q->node);
907 list_add_tail(&pd->alloc_node, &pds);
911 * Install the allocated pds. With @q bypassing, no new blkg
912 * should have been created while the queue lock was dropped.
914 spin_lock_irq(q->queue_lock);
916 list_for_each_entry(blkg, &q->blkg_list, q_node) {
917 if (WARN_ON(list_empty(&pds))) {
918 /* umm... this shouldn't happen, just abort */
922 pd = list_first_entry(&pds, struct blkg_policy_data, alloc_node);
923 list_del_init(&pd->alloc_node);
925 /* grab blkcg lock too while installing @pd on @blkg */
926 spin_lock(&blkg->blkcg->lock);
928 blkg->pd[pol->plid] = pd;
930 pd->plid = pol->plid;
931 pol->pd_init_fn(blkg);
933 spin_unlock(&blkg->blkcg->lock);
936 __set_bit(pol->plid, q->blkcg_pols);
939 spin_unlock_irq(q->queue_lock);
941 blk_queue_bypass_end(q);
942 list_for_each_entry_safe(pd, n, &pds, alloc_node)
946 EXPORT_SYMBOL_GPL(blkcg_activate_policy);
949 * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
950 * @q: request_queue of interest
951 * @pol: blkcg policy to deactivate
953 * Deactivate @pol on @q. Follows the same synchronization rules as
954 * blkcg_activate_policy().
956 void blkcg_deactivate_policy(struct request_queue *q,
957 const struct blkcg_policy *pol)
959 struct blkcg_gq *blkg;
961 if (!blkcg_policy_enabled(q, pol))
964 blk_queue_bypass_start(q);
965 spin_lock_irq(q->queue_lock);
967 __clear_bit(pol->plid, q->blkcg_pols);
969 /* if no policy is left, no need for blkgs - shoot them down */
970 if (bitmap_empty(q->blkcg_pols, BLKCG_MAX_POLS))
973 list_for_each_entry(blkg, &q->blkg_list, q_node) {
974 /* grab blkcg lock too while removing @pd from @blkg */
975 spin_lock(&blkg->blkcg->lock);
977 if (pol->pd_offline_fn)
978 pol->pd_offline_fn(blkg);
980 pol->pd_exit_fn(blkg);
982 kfree(blkg->pd[pol->plid]);
983 blkg->pd[pol->plid] = NULL;
985 spin_unlock(&blkg->blkcg->lock);
988 spin_unlock_irq(q->queue_lock);
989 blk_queue_bypass_end(q);
991 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
994 * blkcg_policy_register - register a blkcg policy
995 * @pol: blkcg policy to register
997 * Register @pol with blkcg core. Might sleep and @pol may be modified on
998 * successful registration. Returns 0 on success and -errno on failure.
1000 int blkcg_policy_register(struct blkcg_policy *pol)
1004 if (WARN_ON(pol->pd_size < sizeof(struct blkg_policy_data)))
1007 mutex_lock(&blkcg_pol_mutex);
1009 /* find an empty slot */
1011 for (i = 0; i < BLKCG_MAX_POLS; i++)
1012 if (!blkcg_policy[i])
1014 if (i >= BLKCG_MAX_POLS)
1017 /* register and update blkgs */
1019 blkcg_policy[i] = pol;
1021 /* everything is in place, add intf files for the new policy */
1023 WARN_ON(cgroup_add_cftypes(&blkio_subsys, pol->cftypes));
1026 mutex_unlock(&blkcg_pol_mutex);
1029 EXPORT_SYMBOL_GPL(blkcg_policy_register);
1032 * blkcg_policy_unregister - unregister a blkcg policy
1033 * @pol: blkcg policy to unregister
1035 * Undo blkcg_policy_register(@pol). Might sleep.
1037 void blkcg_policy_unregister(struct blkcg_policy *pol)
1039 mutex_lock(&blkcg_pol_mutex);
1041 if (WARN_ON(blkcg_policy[pol->plid] != pol))
1044 /* kill the intf files first */
1046 cgroup_rm_cftypes(&blkio_subsys, pol->cftypes);
1048 /* unregister and update blkgs */
1049 blkcg_policy[pol->plid] = NULL;
1051 mutex_unlock(&blkcg_pol_mutex);
1053 EXPORT_SYMBOL_GPL(blkcg_policy_unregister);