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
)) {
190 blkg
= ERR_PTR(-EINVAL
);
196 new_blkg
= blkg_alloc(blkcg
, q
, GFP_ATOMIC
);
197 if (unlikely(!new_blkg
)) {
198 blkg
= ERR_PTR(-ENOMEM
);
205 spin_lock(&blkcg
->lock
);
206 ret
= radix_tree_insert(&blkcg
->blkg_tree
, q
->id
, blkg
);
208 hlist_add_head_rcu(&blkg
->blkcg_node
, &blkcg
->blkg_list
);
209 list_add(&blkg
->q_node
, &q
->blkg_list
);
211 spin_unlock(&blkcg
->lock
);
218 css_put(&blkcg
->css
);
225 * blkg_lookup_create - lookup blkg, try to create one if not there
226 * @blkcg: blkcg of interest
227 * @q: request_queue of interest
229 * Lookup blkg for the @blkcg - @q pair. If it doesn't exist, try to
230 * create one. This function should be called under RCU read lock and
233 * Returns pointer to the looked up or created blkg on success, ERR_PTR()
234 * value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not
235 * dead and bypassing, returns ERR_PTR(-EBUSY).
237 struct blkcg_gq
*blkg_lookup_create(struct blkcg
*blkcg
,
238 struct request_queue
*q
)
240 struct blkcg_gq
*blkg
;
242 WARN_ON_ONCE(!rcu_read_lock_held());
243 lockdep_assert_held(q
->queue_lock
);
246 * This could be the first entry point of blkcg implementation and
247 * we shouldn't allow anything to go through for a bypassing queue.
249 if (unlikely(blk_queue_bypass(q
)))
250 return ERR_PTR(blk_queue_dying(q
) ? -EINVAL
: -EBUSY
);
252 blkg
= __blkg_lookup(blkcg
, q
, true);
256 return blkg_create(blkcg
, q
, NULL
);
258 EXPORT_SYMBOL_GPL(blkg_lookup_create
);
260 static void blkg_destroy(struct blkcg_gq
*blkg
)
262 struct blkcg
*blkcg
= blkg
->blkcg
;
264 lockdep_assert_held(blkg
->q
->queue_lock
);
265 lockdep_assert_held(&blkcg
->lock
);
267 /* Something wrong if we are trying to remove same group twice */
268 WARN_ON_ONCE(list_empty(&blkg
->q_node
));
269 WARN_ON_ONCE(hlist_unhashed(&blkg
->blkcg_node
));
271 radix_tree_delete(&blkcg
->blkg_tree
, blkg
->q
->id
);
272 list_del_init(&blkg
->q_node
);
273 hlist_del_init_rcu(&blkg
->blkcg_node
);
276 * Both setting lookup hint to and clearing it from @blkg are done
277 * under queue_lock. If it's not pointing to @blkg now, it never
278 * will. Hint assignment itself can race safely.
280 if (rcu_dereference_raw(blkcg
->blkg_hint
) == blkg
)
281 rcu_assign_pointer(blkcg
->blkg_hint
, NULL
);
284 * Put the reference taken at the time of creation so that when all
285 * queues are gone, group can be destroyed.
291 * blkg_destroy_all - destroy all blkgs associated with a request_queue
292 * @q: request_queue of interest
294 * Destroy all blkgs associated with @q.
296 static void blkg_destroy_all(struct request_queue
*q
)
298 struct blkcg_gq
*blkg
, *n
;
300 lockdep_assert_held(q
->queue_lock
);
302 list_for_each_entry_safe(blkg
, n
, &q
->blkg_list
, q_node
) {
303 struct blkcg
*blkcg
= blkg
->blkcg
;
305 spin_lock(&blkcg
->lock
);
307 spin_unlock(&blkcg
->lock
);
311 * root blkg is destroyed. Just clear the pointer since
312 * root_rl does not take reference on root blkg.
315 q
->root_rl
.blkg
= NULL
;
318 static void blkg_rcu_free(struct rcu_head
*rcu_head
)
320 blkg_free(container_of(rcu_head
, struct blkcg_gq
, rcu_head
));
323 void __blkg_release(struct blkcg_gq
*blkg
)
325 /* release the extra blkcg reference this blkg has been holding */
326 css_put(&blkg
->blkcg
->css
);
329 * A group is freed in rcu manner. But having an rcu lock does not
330 * mean that one can access all the fields of blkg and assume these
331 * are valid. For example, don't try to follow throtl_data and
332 * request queue links.
334 * Having a reference to blkg under an rcu allows acess to only
335 * values local to groups like group stats and group rate limits
337 call_rcu(&blkg
->rcu_head
, blkg_rcu_free
);
339 EXPORT_SYMBOL_GPL(__blkg_release
);
342 * The next function used by blk_queue_for_each_rl(). It's a bit tricky
343 * because the root blkg uses @q->root_rl instead of its own rl.
345 struct request_list
*__blk_queue_next_rl(struct request_list
*rl
,
346 struct request_queue
*q
)
348 struct list_head
*ent
;
349 struct blkcg_gq
*blkg
;
352 * Determine the current blkg list_head. The first entry is
353 * root_rl which is off @q->blkg_list and mapped to the head.
355 if (rl
== &q
->root_rl
) {
357 /* There are no more block groups, hence no request lists */
361 blkg
= container_of(rl
, struct blkcg_gq
, rl
);
365 /* walk to the next list_head, skip root blkcg */
367 if (ent
== &q
->root_blkg
->q_node
)
369 if (ent
== &q
->blkg_list
)
372 blkg
= container_of(ent
, struct blkcg_gq
, q_node
);
376 static int blkcg_reset_stats(struct cgroup
*cgroup
, struct cftype
*cftype
,
379 struct blkcg
*blkcg
= cgroup_to_blkcg(cgroup
);
380 struct blkcg_gq
*blkg
;
381 struct hlist_node
*n
;
384 mutex_lock(&blkcg_pol_mutex
);
385 spin_lock_irq(&blkcg
->lock
);
388 * Note that stat reset is racy - it doesn't synchronize against
389 * stat updates. This is a debug feature which shouldn't exist
390 * anyway. If you get hit by a race, retry.
392 hlist_for_each_entry(blkg
, n
, &blkcg
->blkg_list
, blkcg_node
) {
393 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
394 struct blkcg_policy
*pol
= blkcg_policy
[i
];
396 if (blkcg_policy_enabled(blkg
->q
, pol
) &&
397 pol
->pd_reset_stats_fn
)
398 pol
->pd_reset_stats_fn(blkg
);
402 spin_unlock_irq(&blkcg
->lock
);
403 mutex_unlock(&blkcg_pol_mutex
);
407 static const char *blkg_dev_name(struct blkcg_gq
*blkg
)
409 /* some drivers (floppy) instantiate a queue w/o disk registered */
410 if (blkg
->q
->backing_dev_info
.dev
)
411 return dev_name(blkg
->q
->backing_dev_info
.dev
);
416 * blkcg_print_blkgs - helper for printing per-blkg data
417 * @sf: seq_file to print to
418 * @blkcg: blkcg of interest
419 * @prfill: fill function to print out a blkg
420 * @pol: policy in question
421 * @data: data to be passed to @prfill
422 * @show_total: to print out sum of prfill return values or not
424 * This function invokes @prfill on each blkg of @blkcg if pd for the
425 * policy specified by @pol exists. @prfill is invoked with @sf, the
426 * policy data and @data. If @show_total is %true, the sum of the return
427 * values from @prfill is printed with "Total" label at the end.
429 * This is to be used to construct print functions for
430 * cftype->read_seq_string method.
432 void blkcg_print_blkgs(struct seq_file
*sf
, struct blkcg
*blkcg
,
433 u64 (*prfill
)(struct seq_file
*,
434 struct blkg_policy_data
*, int),
435 const struct blkcg_policy
*pol
, int data
,
438 struct blkcg_gq
*blkg
;
439 struct hlist_node
*n
;
442 spin_lock_irq(&blkcg
->lock
);
443 hlist_for_each_entry(blkg
, n
, &blkcg
->blkg_list
, blkcg_node
)
444 if (blkcg_policy_enabled(blkg
->q
, pol
))
445 total
+= prfill(sf
, blkg
->pd
[pol
->plid
], data
);
446 spin_unlock_irq(&blkcg
->lock
);
449 seq_printf(sf
, "Total %llu\n", (unsigned long long)total
);
451 EXPORT_SYMBOL_GPL(blkcg_print_blkgs
);
454 * __blkg_prfill_u64 - prfill helper for a single u64 value
455 * @sf: seq_file to print to
456 * @pd: policy private data of interest
459 * Print @v to @sf for the device assocaited with @pd.
461 u64
__blkg_prfill_u64(struct seq_file
*sf
, struct blkg_policy_data
*pd
, u64 v
)
463 const char *dname
= blkg_dev_name(pd
->blkg
);
468 seq_printf(sf
, "%s %llu\n", dname
, (unsigned long long)v
);
471 EXPORT_SYMBOL_GPL(__blkg_prfill_u64
);
474 * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
475 * @sf: seq_file to print to
476 * @pd: policy private data of interest
477 * @rwstat: rwstat to print
479 * Print @rwstat to @sf for the device assocaited with @pd.
481 u64
__blkg_prfill_rwstat(struct seq_file
*sf
, struct blkg_policy_data
*pd
,
482 const struct blkg_rwstat
*rwstat
)
484 static const char *rwstr
[] = {
485 [BLKG_RWSTAT_READ
] = "Read",
486 [BLKG_RWSTAT_WRITE
] = "Write",
487 [BLKG_RWSTAT_SYNC
] = "Sync",
488 [BLKG_RWSTAT_ASYNC
] = "Async",
490 const char *dname
= blkg_dev_name(pd
->blkg
);
497 for (i
= 0; i
< BLKG_RWSTAT_NR
; i
++)
498 seq_printf(sf
, "%s %s %llu\n", dname
, rwstr
[i
],
499 (unsigned long long)rwstat
->cnt
[i
]);
501 v
= rwstat
->cnt
[BLKG_RWSTAT_READ
] + rwstat
->cnt
[BLKG_RWSTAT_WRITE
];
502 seq_printf(sf
, "%s Total %llu\n", dname
, (unsigned long long)v
);
507 * blkg_prfill_stat - prfill callback for blkg_stat
508 * @sf: seq_file to print to
509 * @pd: policy private data of interest
510 * @off: offset to the blkg_stat in @pd
512 * prfill callback for printing a blkg_stat.
514 u64
blkg_prfill_stat(struct seq_file
*sf
, struct blkg_policy_data
*pd
, int off
)
516 return __blkg_prfill_u64(sf
, pd
, blkg_stat_read((void *)pd
+ off
));
518 EXPORT_SYMBOL_GPL(blkg_prfill_stat
);
521 * blkg_prfill_rwstat - prfill callback for blkg_rwstat
522 * @sf: seq_file to print to
523 * @pd: policy private data of interest
524 * @off: offset to the blkg_rwstat in @pd
526 * prfill callback for printing a blkg_rwstat.
528 u64
blkg_prfill_rwstat(struct seq_file
*sf
, struct blkg_policy_data
*pd
,
531 struct blkg_rwstat rwstat
= blkg_rwstat_read((void *)pd
+ off
);
533 return __blkg_prfill_rwstat(sf
, pd
, &rwstat
);
535 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat
);
538 * blkg_conf_prep - parse and prepare for per-blkg config update
539 * @blkcg: target block cgroup
540 * @pol: target policy
541 * @input: input string
542 * @ctx: blkg_conf_ctx to be filled
544 * Parse per-blkg config update from @input and initialize @ctx with the
545 * result. @ctx->blkg points to the blkg to be updated and @ctx->v the new
546 * value. This function returns with RCU read lock and queue lock held and
547 * must be paired with blkg_conf_finish().
549 int blkg_conf_prep(struct blkcg
*blkcg
, const struct blkcg_policy
*pol
,
550 const char *input
, struct blkg_conf_ctx
*ctx
)
551 __acquires(rcu
) __acquires(disk
->queue
->queue_lock
)
553 struct gendisk
*disk
;
554 struct blkcg_gq
*blkg
;
555 unsigned int major
, minor
;
556 unsigned long long v
;
559 if (sscanf(input
, "%u:%u %llu", &major
, &minor
, &v
) != 3)
562 disk
= get_gendisk(MKDEV(major
, minor
), &part
);
567 spin_lock_irq(disk
->queue
->queue_lock
);
569 if (blkcg_policy_enabled(disk
->queue
, pol
))
570 blkg
= blkg_lookup_create(blkcg
, disk
->queue
);
572 blkg
= ERR_PTR(-EINVAL
);
577 spin_unlock_irq(disk
->queue
->queue_lock
);
580 * If queue was bypassing, we should retry. Do so after a
581 * short msleep(). It isn't strictly necessary but queue
582 * can be bypassing for some time and it's always nice to
583 * avoid busy looping.
587 ret
= restart_syscall();
597 EXPORT_SYMBOL_GPL(blkg_conf_prep
);
600 * blkg_conf_finish - finish up per-blkg config update
601 * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
603 * Finish up after per-blkg config update. This function must be paired
604 * with blkg_conf_prep().
606 void blkg_conf_finish(struct blkg_conf_ctx
*ctx
)
607 __releases(ctx
->disk
->queue
->queue_lock
) __releases(rcu
)
609 spin_unlock_irq(ctx
->disk
->queue
->queue_lock
);
613 EXPORT_SYMBOL_GPL(blkg_conf_finish
);
615 struct cftype blkcg_files
[] = {
617 .name
= "reset_stats",
618 .write_u64
= blkcg_reset_stats
,
624 * blkcg_css_offline - cgroup css_offline callback
625 * @cgroup: cgroup of interest
627 * This function is called when @cgroup is about to go away and responsible
628 * for shooting down all blkgs associated with @cgroup. blkgs should be
629 * removed while holding both q and blkcg locks. As blkcg lock is nested
630 * inside q lock, this function performs reverse double lock dancing.
632 * This is the blkcg counterpart of ioc_release_fn().
634 static void blkcg_css_offline(struct cgroup
*cgroup
)
636 struct blkcg
*blkcg
= cgroup_to_blkcg(cgroup
);
638 spin_lock_irq(&blkcg
->lock
);
640 while (!hlist_empty(&blkcg
->blkg_list
)) {
641 struct blkcg_gq
*blkg
= hlist_entry(blkcg
->blkg_list
.first
,
642 struct blkcg_gq
, blkcg_node
);
643 struct request_queue
*q
= blkg
->q
;
645 if (spin_trylock(q
->queue_lock
)) {
647 spin_unlock(q
->queue_lock
);
649 spin_unlock_irq(&blkcg
->lock
);
651 spin_lock_irq(&blkcg
->lock
);
655 spin_unlock_irq(&blkcg
->lock
);
658 static void blkcg_css_free(struct cgroup
*cgroup
)
660 struct blkcg
*blkcg
= cgroup_to_blkcg(cgroup
);
662 if (blkcg
!= &blkcg_root
)
666 static struct cgroup_subsys_state
*blkcg_css_alloc(struct cgroup
*cgroup
)
668 static atomic64_t id_seq
= ATOMIC64_INIT(0);
670 struct cgroup
*parent
= cgroup
->parent
;
677 blkcg
= kzalloc(sizeof(*blkcg
), GFP_KERNEL
);
679 return ERR_PTR(-ENOMEM
);
681 blkcg
->cfq_weight
= CFQ_WEIGHT_DEFAULT
;
682 blkcg
->id
= atomic64_inc_return(&id_seq
); /* root is 0, start from 1 */
684 spin_lock_init(&blkcg
->lock
);
685 INIT_RADIX_TREE(&blkcg
->blkg_tree
, GFP_ATOMIC
);
686 INIT_HLIST_HEAD(&blkcg
->blkg_list
);
692 * blkcg_init_queue - initialize blkcg part of request queue
693 * @q: request_queue to initialize
695 * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
696 * part of new request_queue @q.
699 * 0 on success, -errno on failure.
701 int blkcg_init_queue(struct request_queue
*q
)
705 return blk_throtl_init(q
);
709 * blkcg_drain_queue - drain blkcg part of request_queue
710 * @q: request_queue to drain
712 * Called from blk_drain_queue(). Responsible for draining blkcg part.
714 void blkcg_drain_queue(struct request_queue
*q
)
716 lockdep_assert_held(q
->queue_lock
);
722 * blkcg_exit_queue - exit and release blkcg part of request_queue
723 * @q: request_queue being released
725 * Called from blk_release_queue(). Responsible for exiting blkcg part.
727 void blkcg_exit_queue(struct request_queue
*q
)
729 spin_lock_irq(q
->queue_lock
);
731 spin_unlock_irq(q
->queue_lock
);
737 * We cannot support shared io contexts, as we have no mean to support
738 * two tasks with the same ioc in two different groups without major rework
739 * of the main cic data structures. For now we allow a task to change
740 * its cgroup only if it's the only owner of its ioc.
742 static int blkcg_can_attach(struct cgroup
*cgrp
, struct cgroup_taskset
*tset
)
744 struct task_struct
*task
;
745 struct io_context
*ioc
;
748 /* task_lock() is needed to avoid races with exit_io_context() */
749 cgroup_taskset_for_each(task
, cgrp
, tset
) {
751 ioc
= task
->io_context
;
752 if (ioc
&& atomic_read(&ioc
->nr_tasks
) > 1)
761 struct cgroup_subsys blkio_subsys
= {
763 .css_alloc
= blkcg_css_alloc
,
764 .css_offline
= blkcg_css_offline
,
765 .css_free
= blkcg_css_free
,
766 .can_attach
= blkcg_can_attach
,
767 .subsys_id
= blkio_subsys_id
,
768 .base_cftypes
= blkcg_files
,
769 .module
= THIS_MODULE
,
772 * blkio subsystem is utterly broken in terms of hierarchy support.
773 * It treats all cgroups equally regardless of where they're
774 * located in the hierarchy - all cgroups are treated as if they're
775 * right below the root. Fix it and remove the following.
777 .broken_hierarchy
= true,
779 EXPORT_SYMBOL_GPL(blkio_subsys
);
782 * blkcg_activate_policy - activate a blkcg policy on a request_queue
783 * @q: request_queue of interest
784 * @pol: blkcg policy to activate
786 * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through
787 * bypass mode to populate its blkgs with policy_data for @pol.
789 * Activation happens with @q bypassed, so nobody would be accessing blkgs
790 * from IO path. Update of each blkg is protected by both queue and blkcg
791 * locks so that holding either lock and testing blkcg_policy_enabled() is
792 * always enough for dereferencing policy data.
794 * The caller is responsible for synchronizing [de]activations and policy
795 * [un]registerations. Returns 0 on success, -errno on failure.
797 int blkcg_activate_policy(struct request_queue
*q
,
798 const struct blkcg_policy
*pol
)
801 struct blkcg_gq
*blkg
, *new_blkg
;
802 struct blkg_policy_data
*pd
, *n
;
806 if (blkcg_policy_enabled(q
, pol
))
809 /* preallocations for root blkg */
810 new_blkg
= blkg_alloc(&blkcg_root
, q
, GFP_KERNEL
);
814 preloaded
= !radix_tree_preload(GFP_KERNEL
);
816 blk_queue_bypass_start(q
);
819 * Make sure the root blkg exists and count the existing blkgs. As
820 * @q is bypassing at this point, blkg_lookup_create() can't be
821 * used. Open code it.
823 spin_lock_irq(q
->queue_lock
);
826 blkg
= __blkg_lookup(&blkcg_root
, q
, false);
830 blkg
= blkg_create(&blkcg_root
, q
, new_blkg
);
834 radix_tree_preload_end();
841 q
->root_rl
.blkg
= blkg
;
843 list_for_each_entry(blkg
, &q
->blkg_list
, q_node
)
846 spin_unlock_irq(q
->queue_lock
);
848 /* allocate policy_data for all existing blkgs */
850 pd
= kzalloc_node(pol
->pd_size
, GFP_KERNEL
, q
->node
);
855 list_add_tail(&pd
->alloc_node
, &pds
);
859 * Install the allocated pds. With @q bypassing, no new blkg
860 * should have been created while the queue lock was dropped.
862 spin_lock_irq(q
->queue_lock
);
864 list_for_each_entry(blkg
, &q
->blkg_list
, q_node
) {
865 if (WARN_ON(list_empty(&pds
))) {
866 /* umm... this shouldn't happen, just abort */
870 pd
= list_first_entry(&pds
, struct blkg_policy_data
, alloc_node
);
871 list_del_init(&pd
->alloc_node
);
873 /* grab blkcg lock too while installing @pd on @blkg */
874 spin_lock(&blkg
->blkcg
->lock
);
876 blkg
->pd
[pol
->plid
] = pd
;
878 pol
->pd_init_fn(blkg
);
880 spin_unlock(&blkg
->blkcg
->lock
);
883 __set_bit(pol
->plid
, q
->blkcg_pols
);
886 spin_unlock_irq(q
->queue_lock
);
888 blk_queue_bypass_end(q
);
889 list_for_each_entry_safe(pd
, n
, &pds
, alloc_node
)
893 EXPORT_SYMBOL_GPL(blkcg_activate_policy
);
896 * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
897 * @q: request_queue of interest
898 * @pol: blkcg policy to deactivate
900 * Deactivate @pol on @q. Follows the same synchronization rules as
901 * blkcg_activate_policy().
903 void blkcg_deactivate_policy(struct request_queue
*q
,
904 const struct blkcg_policy
*pol
)
906 struct blkcg_gq
*blkg
;
908 if (!blkcg_policy_enabled(q
, pol
))
911 blk_queue_bypass_start(q
);
912 spin_lock_irq(q
->queue_lock
);
914 __clear_bit(pol
->plid
, q
->blkcg_pols
);
916 /* if no policy is left, no need for blkgs - shoot them down */
917 if (bitmap_empty(q
->blkcg_pols
, BLKCG_MAX_POLS
))
920 list_for_each_entry(blkg
, &q
->blkg_list
, q_node
) {
921 /* grab blkcg lock too while removing @pd from @blkg */
922 spin_lock(&blkg
->blkcg
->lock
);
925 pol
->pd_exit_fn(blkg
);
927 kfree(blkg
->pd
[pol
->plid
]);
928 blkg
->pd
[pol
->plid
] = NULL
;
930 spin_unlock(&blkg
->blkcg
->lock
);
933 spin_unlock_irq(q
->queue_lock
);
934 blk_queue_bypass_end(q
);
936 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy
);
939 * blkcg_policy_register - register a blkcg policy
940 * @pol: blkcg policy to register
942 * Register @pol with blkcg core. Might sleep and @pol may be modified on
943 * successful registration. Returns 0 on success and -errno on failure.
945 int blkcg_policy_register(struct blkcg_policy
*pol
)
949 if (WARN_ON(pol
->pd_size
< sizeof(struct blkg_policy_data
)))
952 mutex_lock(&blkcg_pol_mutex
);
954 /* find an empty slot */
956 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++)
957 if (!blkcg_policy
[i
])
959 if (i
>= BLKCG_MAX_POLS
)
962 /* register and update blkgs */
964 blkcg_policy
[i
] = pol
;
966 /* everything is in place, add intf files for the new policy */
968 WARN_ON(cgroup_add_cftypes(&blkio_subsys
, pol
->cftypes
));
971 mutex_unlock(&blkcg_pol_mutex
);
974 EXPORT_SYMBOL_GPL(blkcg_policy_register
);
977 * blkcg_policy_unregister - unregister a blkcg policy
978 * @pol: blkcg policy to unregister
980 * Undo blkcg_policy_register(@pol). Might sleep.
982 void blkcg_policy_unregister(struct blkcg_policy
*pol
)
984 mutex_lock(&blkcg_pol_mutex
);
986 if (WARN_ON(blkcg_policy
[pol
->plid
] != pol
))
989 /* kill the intf files first */
991 cgroup_rm_cftypes(&blkio_subsys
, pol
->cftypes
);
993 /* unregister and update blkgs */
994 blkcg_policy
[pol
->plid
] = NULL
;
996 mutex_unlock(&blkcg_pol_mutex
);
998 EXPORT_SYMBOL_GPL(blkcg_policy_unregister
);