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 spin_unlock(&blkcg
->lock
);
227 /* @blkg failed fully initialized, use the usual release path */
232 css_put(&blkcg
->css
);
239 * blkg_lookup_create - lookup blkg, try to create one if not there
240 * @blkcg: blkcg of interest
241 * @q: request_queue of interest
243 * Lookup blkg for the @blkcg - @q pair. If it doesn't exist, try to
244 * create one. blkg creation is performed recursively from blkcg_root such
245 * that all non-root blkg's have access to the parent blkg. This function
246 * should be called under RCU read lock and @q->queue_lock.
248 * Returns pointer to the looked up or created blkg on success, ERR_PTR()
249 * value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not
250 * dead and bypassing, returns ERR_PTR(-EBUSY).
252 struct blkcg_gq
*blkg_lookup_create(struct blkcg
*blkcg
,
253 struct request_queue
*q
)
255 struct blkcg_gq
*blkg
;
257 WARN_ON_ONCE(!rcu_read_lock_held());
258 lockdep_assert_held(q
->queue_lock
);
261 * This could be the first entry point of blkcg implementation and
262 * we shouldn't allow anything to go through for a bypassing queue.
264 if (unlikely(blk_queue_bypass(q
)))
265 return ERR_PTR(blk_queue_dying(q
) ? -EINVAL
: -EBUSY
);
267 blkg
= __blkg_lookup(blkcg
, q
, true);
272 * Create blkgs walking down from blkcg_root to @blkcg, so that all
273 * non-root blkgs have access to their parents.
276 struct blkcg
*pos
= blkcg
;
277 struct blkcg
*parent
= blkcg_parent(blkcg
);
279 while (parent
&& !__blkg_lookup(parent
, q
, false)) {
281 parent
= blkcg_parent(parent
);
284 blkg
= blkg_create(pos
, q
, NULL
);
285 if (pos
== blkcg
|| IS_ERR(blkg
))
289 EXPORT_SYMBOL_GPL(blkg_lookup_create
);
291 static void blkg_destroy(struct blkcg_gq
*blkg
)
293 struct blkcg
*blkcg
= blkg
->blkcg
;
295 lockdep_assert_held(blkg
->q
->queue_lock
);
296 lockdep_assert_held(&blkcg
->lock
);
298 /* Something wrong if we are trying to remove same group twice */
299 WARN_ON_ONCE(list_empty(&blkg
->q_node
));
300 WARN_ON_ONCE(hlist_unhashed(&blkg
->blkcg_node
));
302 radix_tree_delete(&blkcg
->blkg_tree
, blkg
->q
->id
);
303 list_del_init(&blkg
->q_node
);
304 hlist_del_init_rcu(&blkg
->blkcg_node
);
307 * Both setting lookup hint to and clearing it from @blkg are done
308 * under queue_lock. If it's not pointing to @blkg now, it never
309 * will. Hint assignment itself can race safely.
311 if (rcu_dereference_raw(blkcg
->blkg_hint
) == blkg
)
312 rcu_assign_pointer(blkcg
->blkg_hint
, NULL
);
315 * Put the reference taken at the time of creation so that when all
316 * queues are gone, group can be destroyed.
322 * blkg_destroy_all - destroy all blkgs associated with a request_queue
323 * @q: request_queue of interest
325 * Destroy all blkgs associated with @q.
327 static void blkg_destroy_all(struct request_queue
*q
)
329 struct blkcg_gq
*blkg
, *n
;
331 lockdep_assert_held(q
->queue_lock
);
333 list_for_each_entry_safe(blkg
, n
, &q
->blkg_list
, q_node
) {
334 struct blkcg
*blkcg
= blkg
->blkcg
;
336 spin_lock(&blkcg
->lock
);
338 spin_unlock(&blkcg
->lock
);
342 * root blkg is destroyed. Just clear the pointer since
343 * root_rl does not take reference on root blkg.
346 q
->root_rl
.blkg
= NULL
;
349 static void blkg_rcu_free(struct rcu_head
*rcu_head
)
351 blkg_free(container_of(rcu_head
, struct blkcg_gq
, rcu_head
));
354 void __blkg_release(struct blkcg_gq
*blkg
)
356 /* release the blkcg and parent blkg refs this blkg has been holding */
357 css_put(&blkg
->blkcg
->css
);
359 blkg_put(blkg
->parent
);
362 * A group is freed in rcu manner. But having an rcu lock does not
363 * mean that one can access all the fields of blkg and assume these
364 * are valid. For example, don't try to follow throtl_data and
365 * request queue links.
367 * Having a reference to blkg under an rcu allows acess to only
368 * values local to groups like group stats and group rate limits
370 call_rcu(&blkg
->rcu_head
, blkg_rcu_free
);
372 EXPORT_SYMBOL_GPL(__blkg_release
);
375 * The next function used by blk_queue_for_each_rl(). It's a bit tricky
376 * because the root blkg uses @q->root_rl instead of its own rl.
378 struct request_list
*__blk_queue_next_rl(struct request_list
*rl
,
379 struct request_queue
*q
)
381 struct list_head
*ent
;
382 struct blkcg_gq
*blkg
;
385 * Determine the current blkg list_head. The first entry is
386 * root_rl which is off @q->blkg_list and mapped to the head.
388 if (rl
== &q
->root_rl
) {
390 /* There are no more block groups, hence no request lists */
394 blkg
= container_of(rl
, struct blkcg_gq
, rl
);
398 /* walk to the next list_head, skip root blkcg */
400 if (ent
== &q
->root_blkg
->q_node
)
402 if (ent
== &q
->blkg_list
)
405 blkg
= container_of(ent
, struct blkcg_gq
, q_node
);
409 static int blkcg_reset_stats(struct cgroup
*cgroup
, struct cftype
*cftype
,
412 struct blkcg
*blkcg
= cgroup_to_blkcg(cgroup
);
413 struct blkcg_gq
*blkg
;
414 struct hlist_node
*n
;
417 mutex_lock(&blkcg_pol_mutex
);
418 spin_lock_irq(&blkcg
->lock
);
421 * Note that stat reset is racy - it doesn't synchronize against
422 * stat updates. This is a debug feature which shouldn't exist
423 * anyway. If you get hit by a race, retry.
425 hlist_for_each_entry(blkg
, n
, &blkcg
->blkg_list
, blkcg_node
) {
426 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
427 struct blkcg_policy
*pol
= blkcg_policy
[i
];
429 if (blkcg_policy_enabled(blkg
->q
, pol
) &&
430 pol
->pd_reset_stats_fn
)
431 pol
->pd_reset_stats_fn(blkg
);
435 spin_unlock_irq(&blkcg
->lock
);
436 mutex_unlock(&blkcg_pol_mutex
);
440 static const char *blkg_dev_name(struct blkcg_gq
*blkg
)
442 /* some drivers (floppy) instantiate a queue w/o disk registered */
443 if (blkg
->q
->backing_dev_info
.dev
)
444 return dev_name(blkg
->q
->backing_dev_info
.dev
);
449 * blkcg_print_blkgs - helper for printing per-blkg data
450 * @sf: seq_file to print to
451 * @blkcg: blkcg of interest
452 * @prfill: fill function to print out a blkg
453 * @pol: policy in question
454 * @data: data to be passed to @prfill
455 * @show_total: to print out sum of prfill return values or not
457 * This function invokes @prfill on each blkg of @blkcg if pd for the
458 * policy specified by @pol exists. @prfill is invoked with @sf, the
459 * policy data and @data. If @show_total is %true, the sum of the return
460 * values from @prfill is printed with "Total" label at the end.
462 * This is to be used to construct print functions for
463 * cftype->read_seq_string method.
465 void blkcg_print_blkgs(struct seq_file
*sf
, struct blkcg
*blkcg
,
466 u64 (*prfill
)(struct seq_file
*,
467 struct blkg_policy_data
*, int),
468 const struct blkcg_policy
*pol
, int data
,
471 struct blkcg_gq
*blkg
;
472 struct hlist_node
*n
;
475 spin_lock_irq(&blkcg
->lock
);
476 hlist_for_each_entry(blkg
, n
, &blkcg
->blkg_list
, blkcg_node
)
477 if (blkcg_policy_enabled(blkg
->q
, pol
))
478 total
+= prfill(sf
, blkg
->pd
[pol
->plid
], data
);
479 spin_unlock_irq(&blkcg
->lock
);
482 seq_printf(sf
, "Total %llu\n", (unsigned long long)total
);
484 EXPORT_SYMBOL_GPL(blkcg_print_blkgs
);
487 * __blkg_prfill_u64 - prfill helper for a single u64 value
488 * @sf: seq_file to print to
489 * @pd: policy private data of interest
492 * Print @v to @sf for the device assocaited with @pd.
494 u64
__blkg_prfill_u64(struct seq_file
*sf
, struct blkg_policy_data
*pd
, u64 v
)
496 const char *dname
= blkg_dev_name(pd
->blkg
);
501 seq_printf(sf
, "%s %llu\n", dname
, (unsigned long long)v
);
504 EXPORT_SYMBOL_GPL(__blkg_prfill_u64
);
507 * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
508 * @sf: seq_file to print to
509 * @pd: policy private data of interest
510 * @rwstat: rwstat to print
512 * Print @rwstat to @sf for the device assocaited with @pd.
514 u64
__blkg_prfill_rwstat(struct seq_file
*sf
, struct blkg_policy_data
*pd
,
515 const struct blkg_rwstat
*rwstat
)
517 static const char *rwstr
[] = {
518 [BLKG_RWSTAT_READ
] = "Read",
519 [BLKG_RWSTAT_WRITE
] = "Write",
520 [BLKG_RWSTAT_SYNC
] = "Sync",
521 [BLKG_RWSTAT_ASYNC
] = "Async",
523 const char *dname
= blkg_dev_name(pd
->blkg
);
530 for (i
= 0; i
< BLKG_RWSTAT_NR
; i
++)
531 seq_printf(sf
, "%s %s %llu\n", dname
, rwstr
[i
],
532 (unsigned long long)rwstat
->cnt
[i
]);
534 v
= rwstat
->cnt
[BLKG_RWSTAT_READ
] + rwstat
->cnt
[BLKG_RWSTAT_WRITE
];
535 seq_printf(sf
, "%s Total %llu\n", dname
, (unsigned long long)v
);
540 * blkg_prfill_stat - prfill callback for blkg_stat
541 * @sf: seq_file to print to
542 * @pd: policy private data of interest
543 * @off: offset to the blkg_stat in @pd
545 * prfill callback for printing a blkg_stat.
547 u64
blkg_prfill_stat(struct seq_file
*sf
, struct blkg_policy_data
*pd
, int off
)
549 return __blkg_prfill_u64(sf
, pd
, blkg_stat_read((void *)pd
+ off
));
551 EXPORT_SYMBOL_GPL(blkg_prfill_stat
);
554 * blkg_prfill_rwstat - prfill callback for blkg_rwstat
555 * @sf: seq_file to print to
556 * @pd: policy private data of interest
557 * @off: offset to the blkg_rwstat in @pd
559 * prfill callback for printing a blkg_rwstat.
561 u64
blkg_prfill_rwstat(struct seq_file
*sf
, struct blkg_policy_data
*pd
,
564 struct blkg_rwstat rwstat
= blkg_rwstat_read((void *)pd
+ off
);
566 return __blkg_prfill_rwstat(sf
, pd
, &rwstat
);
568 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat
);
571 * blkg_conf_prep - parse and prepare for per-blkg config update
572 * @blkcg: target block cgroup
573 * @pol: target policy
574 * @input: input string
575 * @ctx: blkg_conf_ctx to be filled
577 * Parse per-blkg config update from @input and initialize @ctx with the
578 * result. @ctx->blkg points to the blkg to be updated and @ctx->v the new
579 * value. This function returns with RCU read lock and queue lock held and
580 * must be paired with blkg_conf_finish().
582 int blkg_conf_prep(struct blkcg
*blkcg
, const struct blkcg_policy
*pol
,
583 const char *input
, struct blkg_conf_ctx
*ctx
)
584 __acquires(rcu
) __acquires(disk
->queue
->queue_lock
)
586 struct gendisk
*disk
;
587 struct blkcg_gq
*blkg
;
588 unsigned int major
, minor
;
589 unsigned long long v
;
592 if (sscanf(input
, "%u:%u %llu", &major
, &minor
, &v
) != 3)
595 disk
= get_gendisk(MKDEV(major
, minor
), &part
);
600 spin_lock_irq(disk
->queue
->queue_lock
);
602 if (blkcg_policy_enabled(disk
->queue
, pol
))
603 blkg
= blkg_lookup_create(blkcg
, disk
->queue
);
605 blkg
= ERR_PTR(-EINVAL
);
610 spin_unlock_irq(disk
->queue
->queue_lock
);
613 * If queue was bypassing, we should retry. Do so after a
614 * short msleep(). It isn't strictly necessary but queue
615 * can be bypassing for some time and it's always nice to
616 * avoid busy looping.
620 ret
= restart_syscall();
630 EXPORT_SYMBOL_GPL(blkg_conf_prep
);
633 * blkg_conf_finish - finish up per-blkg config update
634 * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
636 * Finish up after per-blkg config update. This function must be paired
637 * with blkg_conf_prep().
639 void blkg_conf_finish(struct blkg_conf_ctx
*ctx
)
640 __releases(ctx
->disk
->queue
->queue_lock
) __releases(rcu
)
642 spin_unlock_irq(ctx
->disk
->queue
->queue_lock
);
646 EXPORT_SYMBOL_GPL(blkg_conf_finish
);
648 struct cftype blkcg_files
[] = {
650 .name
= "reset_stats",
651 .write_u64
= blkcg_reset_stats
,
657 * blkcg_css_offline - cgroup css_offline callback
658 * @cgroup: cgroup of interest
660 * This function is called when @cgroup is about to go away and responsible
661 * for shooting down all blkgs associated with @cgroup. blkgs should be
662 * removed while holding both q and blkcg locks. As blkcg lock is nested
663 * inside q lock, this function performs reverse double lock dancing.
665 * This is the blkcg counterpart of ioc_release_fn().
667 static void blkcg_css_offline(struct cgroup
*cgroup
)
669 struct blkcg
*blkcg
= cgroup_to_blkcg(cgroup
);
671 spin_lock_irq(&blkcg
->lock
);
673 while (!hlist_empty(&blkcg
->blkg_list
)) {
674 struct blkcg_gq
*blkg
= hlist_entry(blkcg
->blkg_list
.first
,
675 struct blkcg_gq
, blkcg_node
);
676 struct request_queue
*q
= blkg
->q
;
678 if (spin_trylock(q
->queue_lock
)) {
680 spin_unlock(q
->queue_lock
);
682 spin_unlock_irq(&blkcg
->lock
);
684 spin_lock_irq(&blkcg
->lock
);
688 spin_unlock_irq(&blkcg
->lock
);
691 static void blkcg_css_free(struct cgroup
*cgroup
)
693 struct blkcg
*blkcg
= cgroup_to_blkcg(cgroup
);
695 if (blkcg
!= &blkcg_root
)
699 static struct cgroup_subsys_state
*blkcg_css_alloc(struct cgroup
*cgroup
)
701 static atomic64_t id_seq
= ATOMIC64_INIT(0);
703 struct cgroup
*parent
= cgroup
->parent
;
710 blkcg
= kzalloc(sizeof(*blkcg
), GFP_KERNEL
);
712 return ERR_PTR(-ENOMEM
);
714 blkcg
->cfq_weight
= CFQ_WEIGHT_DEFAULT
;
715 blkcg
->cfq_leaf_weight
= CFQ_WEIGHT_DEFAULT
;
716 blkcg
->id
= atomic64_inc_return(&id_seq
); /* root is 0, start from 1 */
718 spin_lock_init(&blkcg
->lock
);
719 INIT_RADIX_TREE(&blkcg
->blkg_tree
, GFP_ATOMIC
);
720 INIT_HLIST_HEAD(&blkcg
->blkg_list
);
726 * blkcg_init_queue - initialize blkcg part of request queue
727 * @q: request_queue to initialize
729 * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
730 * part of new request_queue @q.
733 * 0 on success, -errno on failure.
735 int blkcg_init_queue(struct request_queue
*q
)
739 return blk_throtl_init(q
);
743 * blkcg_drain_queue - drain blkcg part of request_queue
744 * @q: request_queue to drain
746 * Called from blk_drain_queue(). Responsible for draining blkcg part.
748 void blkcg_drain_queue(struct request_queue
*q
)
750 lockdep_assert_held(q
->queue_lock
);
756 * blkcg_exit_queue - exit and release blkcg part of request_queue
757 * @q: request_queue being released
759 * Called from blk_release_queue(). Responsible for exiting blkcg part.
761 void blkcg_exit_queue(struct request_queue
*q
)
763 spin_lock_irq(q
->queue_lock
);
765 spin_unlock_irq(q
->queue_lock
);
771 * We cannot support shared io contexts, as we have no mean to support
772 * two tasks with the same ioc in two different groups without major rework
773 * of the main cic data structures. For now we allow a task to change
774 * its cgroup only if it's the only owner of its ioc.
776 static int blkcg_can_attach(struct cgroup
*cgrp
, struct cgroup_taskset
*tset
)
778 struct task_struct
*task
;
779 struct io_context
*ioc
;
782 /* task_lock() is needed to avoid races with exit_io_context() */
783 cgroup_taskset_for_each(task
, cgrp
, tset
) {
785 ioc
= task
->io_context
;
786 if (ioc
&& atomic_read(&ioc
->nr_tasks
) > 1)
795 struct cgroup_subsys blkio_subsys
= {
797 .css_alloc
= blkcg_css_alloc
,
798 .css_offline
= blkcg_css_offline
,
799 .css_free
= blkcg_css_free
,
800 .can_attach
= blkcg_can_attach
,
801 .subsys_id
= blkio_subsys_id
,
802 .base_cftypes
= blkcg_files
,
803 .module
= THIS_MODULE
,
806 * blkio subsystem is utterly broken in terms of hierarchy support.
807 * It treats all cgroups equally regardless of where they're
808 * located in the hierarchy - all cgroups are treated as if they're
809 * right below the root. Fix it and remove the following.
811 .broken_hierarchy
= true,
813 EXPORT_SYMBOL_GPL(blkio_subsys
);
816 * blkcg_activate_policy - activate a blkcg policy on a request_queue
817 * @q: request_queue of interest
818 * @pol: blkcg policy to activate
820 * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through
821 * bypass mode to populate its blkgs with policy_data for @pol.
823 * Activation happens with @q bypassed, so nobody would be accessing blkgs
824 * from IO path. Update of each blkg is protected by both queue and blkcg
825 * locks so that holding either lock and testing blkcg_policy_enabled() is
826 * always enough for dereferencing policy data.
828 * The caller is responsible for synchronizing [de]activations and policy
829 * [un]registerations. Returns 0 on success, -errno on failure.
831 int blkcg_activate_policy(struct request_queue
*q
,
832 const struct blkcg_policy
*pol
)
835 struct blkcg_gq
*blkg
, *new_blkg
;
836 struct blkg_policy_data
*pd
, *n
;
840 if (blkcg_policy_enabled(q
, pol
))
843 /* preallocations for root blkg */
844 new_blkg
= blkg_alloc(&blkcg_root
, q
, GFP_KERNEL
);
848 preloaded
= !radix_tree_preload(GFP_KERNEL
);
850 blk_queue_bypass_start(q
);
853 * Make sure the root blkg exists and count the existing blkgs. As
854 * @q is bypassing at this point, blkg_lookup_create() can't be
855 * used. Open code it.
857 spin_lock_irq(q
->queue_lock
);
860 blkg
= __blkg_lookup(&blkcg_root
, q
, false);
864 blkg
= blkg_create(&blkcg_root
, q
, new_blkg
);
868 radix_tree_preload_end();
875 q
->root_rl
.blkg
= blkg
;
877 list_for_each_entry(blkg
, &q
->blkg_list
, q_node
)
880 spin_unlock_irq(q
->queue_lock
);
882 /* allocate policy_data for all existing blkgs */
884 pd
= kzalloc_node(pol
->pd_size
, GFP_KERNEL
, q
->node
);
889 list_add_tail(&pd
->alloc_node
, &pds
);
893 * Install the allocated pds. With @q bypassing, no new blkg
894 * should have been created while the queue lock was dropped.
896 spin_lock_irq(q
->queue_lock
);
898 list_for_each_entry(blkg
, &q
->blkg_list
, q_node
) {
899 if (WARN_ON(list_empty(&pds
))) {
900 /* umm... this shouldn't happen, just abort */
904 pd
= list_first_entry(&pds
, struct blkg_policy_data
, alloc_node
);
905 list_del_init(&pd
->alloc_node
);
907 /* grab blkcg lock too while installing @pd on @blkg */
908 spin_lock(&blkg
->blkcg
->lock
);
910 blkg
->pd
[pol
->plid
] = pd
;
912 pd
->plid
= pol
->plid
;
913 pol
->pd_init_fn(blkg
);
915 spin_unlock(&blkg
->blkcg
->lock
);
918 __set_bit(pol
->plid
, q
->blkcg_pols
);
921 spin_unlock_irq(q
->queue_lock
);
923 blk_queue_bypass_end(q
);
924 list_for_each_entry_safe(pd
, n
, &pds
, alloc_node
)
928 EXPORT_SYMBOL_GPL(blkcg_activate_policy
);
931 * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
932 * @q: request_queue of interest
933 * @pol: blkcg policy to deactivate
935 * Deactivate @pol on @q. Follows the same synchronization rules as
936 * blkcg_activate_policy().
938 void blkcg_deactivate_policy(struct request_queue
*q
,
939 const struct blkcg_policy
*pol
)
941 struct blkcg_gq
*blkg
;
943 if (!blkcg_policy_enabled(q
, pol
))
946 blk_queue_bypass_start(q
);
947 spin_lock_irq(q
->queue_lock
);
949 __clear_bit(pol
->plid
, q
->blkcg_pols
);
951 /* if no policy is left, no need for blkgs - shoot them down */
952 if (bitmap_empty(q
->blkcg_pols
, BLKCG_MAX_POLS
))
955 list_for_each_entry(blkg
, &q
->blkg_list
, q_node
) {
956 /* grab blkcg lock too while removing @pd from @blkg */
957 spin_lock(&blkg
->blkcg
->lock
);
960 pol
->pd_exit_fn(blkg
);
962 kfree(blkg
->pd
[pol
->plid
]);
963 blkg
->pd
[pol
->plid
] = NULL
;
965 spin_unlock(&blkg
->blkcg
->lock
);
968 spin_unlock_irq(q
->queue_lock
);
969 blk_queue_bypass_end(q
);
971 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy
);
974 * blkcg_policy_register - register a blkcg policy
975 * @pol: blkcg policy to register
977 * Register @pol with blkcg core. Might sleep and @pol may be modified on
978 * successful registration. Returns 0 on success and -errno on failure.
980 int blkcg_policy_register(struct blkcg_policy
*pol
)
984 if (WARN_ON(pol
->pd_size
< sizeof(struct blkg_policy_data
)))
987 mutex_lock(&blkcg_pol_mutex
);
989 /* find an empty slot */
991 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++)
992 if (!blkcg_policy
[i
])
994 if (i
>= BLKCG_MAX_POLS
)
997 /* register and update blkgs */
999 blkcg_policy
[i
] = pol
;
1001 /* everything is in place, add intf files for the new policy */
1003 WARN_ON(cgroup_add_cftypes(&blkio_subsys
, pol
->cftypes
));
1006 mutex_unlock(&blkcg_pol_mutex
);
1009 EXPORT_SYMBOL_GPL(blkcg_policy_register
);
1012 * blkcg_policy_unregister - unregister a blkcg policy
1013 * @pol: blkcg policy to unregister
1015 * Undo blkcg_policy_register(@pol). Might sleep.
1017 void blkcg_policy_unregister(struct blkcg_policy
*pol
)
1019 mutex_lock(&blkcg_pol_mutex
);
1021 if (WARN_ON(blkcg_policy
[pol
->plid
] != pol
))
1024 /* kill the intf files first */
1026 cgroup_rm_cftypes(&blkio_subsys
, pol
->cftypes
);
1028 /* unregister and update blkgs */
1029 blkcg_policy
[pol
->plid
] = NULL
;
1031 mutex_unlock(&blkcg_pol_mutex
);
1033 EXPORT_SYMBOL_GPL(blkcg_policy_unregister
);