Linux 3.8-rc7
[cris-mirror.git] / block / blk-cgroup.c
blobb8858fb0cafa34e491f6ad0e719a16ba3cd8d015
1 /*
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"
23 #include "blk.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);
40 /**
41 * blkg_free - free a blkg
42 * @blkg: blkg to free
44 * Free @blkg which may be partially allocated.
46 static void blkg_free(struct blkcg_gq *blkg)
48 int i;
50 if (!blkg)
51 return;
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];
57 if (!pd)
58 continue;
60 if (pol && pol->pd_exit_fn)
61 pol->pd_exit_fn(blkg);
63 kfree(pd);
66 blk_exit_rl(&blkg->rl);
67 kfree(blkg);
70 /**
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,
79 gfp_t gfp_mask)
81 struct blkcg_gq *blkg;
82 int i;
84 /* alloc and init base part */
85 blkg = kzalloc_node(sizeof(*blkg), gfp_mask, q->node);
86 if (!blkg)
87 return NULL;
89 blkg->q = q;
90 INIT_LIST_HEAD(&blkg->q_node);
91 blkg->blkcg = blkcg;
92 blkg->refcnt = 1;
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))
97 goto err_free;
98 blkg->rl.blkg = blkg;
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))
106 continue;
108 /* alloc per-policy data and attach it to blkg */
109 pd = kzalloc_node(pol->pd_size, gfp_mask, q->node);
110 if (!pd)
111 goto err_free;
113 blkg->pd[i] = pd;
114 pd->blkg = blkg;
116 /* invoke per-policy init */
117 if (blkcg_policy_enabled(blkg->q, pol))
118 pol->pd_init_fn(blkg);
121 return blkg;
123 err_free:
124 blkg_free(blkg);
125 return NULL;
128 static struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg,
129 struct request_queue *q)
131 struct blkcg_gq *blkg;
133 blkg = rcu_dereference(blkcg->blkg_hint);
134 if (blkg && blkg->q == q)
135 return blkg;
138 * Hint didn't match. Look up from the radix tree. Note that we
139 * may not be holding queue_lock and thus are not sure whether
140 * @blkg from blkg_tree has already been removed or not, so we
141 * can't update hint to the lookup result. Leave it to the caller.
143 blkg = radix_tree_lookup(&blkcg->blkg_tree, q->id);
144 if (blkg && blkg->q == q)
145 return blkg;
147 return NULL;
151 * blkg_lookup - lookup blkg for the specified blkcg - q pair
152 * @blkcg: blkcg of interest
153 * @q: request_queue of interest
155 * Lookup blkg for the @blkcg - @q pair. This function should be called
156 * under RCU read lock and is guaranteed to return %NULL if @q is bypassing
157 * - see blk_queue_bypass_start() for details.
159 struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, struct request_queue *q)
161 WARN_ON_ONCE(!rcu_read_lock_held());
163 if (unlikely(blk_queue_bypass(q)))
164 return NULL;
165 return __blkg_lookup(blkcg, q);
167 EXPORT_SYMBOL_GPL(blkg_lookup);
170 * If @new_blkg is %NULL, this function tries to allocate a new one as
171 * necessary using %GFP_ATOMIC. @new_blkg is always consumed on return.
173 static struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
174 struct request_queue *q,
175 struct blkcg_gq *new_blkg)
177 struct blkcg_gq *blkg;
178 int ret;
180 WARN_ON_ONCE(!rcu_read_lock_held());
181 lockdep_assert_held(q->queue_lock);
183 /* lookup and update hint on success, see __blkg_lookup() for details */
184 blkg = __blkg_lookup(blkcg, q);
185 if (blkg) {
186 rcu_assign_pointer(blkcg->blkg_hint, blkg);
187 goto out_free;
190 /* blkg holds a reference to blkcg */
191 if (!css_tryget(&blkcg->css)) {
192 blkg = ERR_PTR(-EINVAL);
193 goto out_free;
196 /* allocate */
197 if (!new_blkg) {
198 new_blkg = blkg_alloc(blkcg, q, GFP_ATOMIC);
199 if (unlikely(!new_blkg)) {
200 blkg = ERR_PTR(-ENOMEM);
201 goto out_put;
204 blkg = new_blkg;
206 /* insert */
207 spin_lock(&blkcg->lock);
208 ret = radix_tree_insert(&blkcg->blkg_tree, q->id, blkg);
209 if (likely(!ret)) {
210 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
211 list_add(&blkg->q_node, &q->blkg_list);
213 spin_unlock(&blkcg->lock);
215 if (!ret)
216 return blkg;
218 blkg = ERR_PTR(ret);
219 out_put:
220 css_put(&blkcg->css);
221 out_free:
222 blkg_free(new_blkg);
223 return blkg;
226 struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
227 struct request_queue *q)
230 * This could be the first entry point of blkcg implementation and
231 * we shouldn't allow anything to go through for a bypassing queue.
233 if (unlikely(blk_queue_bypass(q)))
234 return ERR_PTR(blk_queue_dying(q) ? -EINVAL : -EBUSY);
235 return __blkg_lookup_create(blkcg, q, NULL);
237 EXPORT_SYMBOL_GPL(blkg_lookup_create);
239 static void blkg_destroy(struct blkcg_gq *blkg)
241 struct blkcg *blkcg = blkg->blkcg;
243 lockdep_assert_held(blkg->q->queue_lock);
244 lockdep_assert_held(&blkcg->lock);
246 /* Something wrong if we are trying to remove same group twice */
247 WARN_ON_ONCE(list_empty(&blkg->q_node));
248 WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
250 radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
251 list_del_init(&blkg->q_node);
252 hlist_del_init_rcu(&blkg->blkcg_node);
255 * Both setting lookup hint to and clearing it from @blkg are done
256 * under queue_lock. If it's not pointing to @blkg now, it never
257 * will. Hint assignment itself can race safely.
259 if (rcu_dereference_raw(blkcg->blkg_hint) == blkg)
260 rcu_assign_pointer(blkcg->blkg_hint, NULL);
263 * Put the reference taken at the time of creation so that when all
264 * queues are gone, group can be destroyed.
266 blkg_put(blkg);
270 * blkg_destroy_all - destroy all blkgs associated with a request_queue
271 * @q: request_queue of interest
273 * Destroy all blkgs associated with @q.
275 static void blkg_destroy_all(struct request_queue *q)
277 struct blkcg_gq *blkg, *n;
279 lockdep_assert_held(q->queue_lock);
281 list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
282 struct blkcg *blkcg = blkg->blkcg;
284 spin_lock(&blkcg->lock);
285 blkg_destroy(blkg);
286 spin_unlock(&blkcg->lock);
290 * root blkg is destroyed. Just clear the pointer since
291 * root_rl does not take reference on root blkg.
293 q->root_blkg = NULL;
294 q->root_rl.blkg = NULL;
297 static void blkg_rcu_free(struct rcu_head *rcu_head)
299 blkg_free(container_of(rcu_head, struct blkcg_gq, rcu_head));
302 void __blkg_release(struct blkcg_gq *blkg)
304 /* release the extra blkcg reference this blkg has been holding */
305 css_put(&blkg->blkcg->css);
308 * A group is freed in rcu manner. But having an rcu lock does not
309 * mean that one can access all the fields of blkg and assume these
310 * are valid. For example, don't try to follow throtl_data and
311 * request queue links.
313 * Having a reference to blkg under an rcu allows acess to only
314 * values local to groups like group stats and group rate limits
316 call_rcu(&blkg->rcu_head, blkg_rcu_free);
318 EXPORT_SYMBOL_GPL(__blkg_release);
321 * The next function used by blk_queue_for_each_rl(). It's a bit tricky
322 * because the root blkg uses @q->root_rl instead of its own rl.
324 struct request_list *__blk_queue_next_rl(struct request_list *rl,
325 struct request_queue *q)
327 struct list_head *ent;
328 struct blkcg_gq *blkg;
331 * Determine the current blkg list_head. The first entry is
332 * root_rl which is off @q->blkg_list and mapped to the head.
334 if (rl == &q->root_rl) {
335 ent = &q->blkg_list;
336 /* There are no more block groups, hence no request lists */
337 if (list_empty(ent))
338 return NULL;
339 } else {
340 blkg = container_of(rl, struct blkcg_gq, rl);
341 ent = &blkg->q_node;
344 /* walk to the next list_head, skip root blkcg */
345 ent = ent->next;
346 if (ent == &q->root_blkg->q_node)
347 ent = ent->next;
348 if (ent == &q->blkg_list)
349 return NULL;
351 blkg = container_of(ent, struct blkcg_gq, q_node);
352 return &blkg->rl;
355 static int blkcg_reset_stats(struct cgroup *cgroup, struct cftype *cftype,
356 u64 val)
358 struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
359 struct blkcg_gq *blkg;
360 struct hlist_node *n;
361 int i;
363 mutex_lock(&blkcg_pol_mutex);
364 spin_lock_irq(&blkcg->lock);
367 * Note that stat reset is racy - it doesn't synchronize against
368 * stat updates. This is a debug feature which shouldn't exist
369 * anyway. If you get hit by a race, retry.
371 hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
372 for (i = 0; i < BLKCG_MAX_POLS; i++) {
373 struct blkcg_policy *pol = blkcg_policy[i];
375 if (blkcg_policy_enabled(blkg->q, pol) &&
376 pol->pd_reset_stats_fn)
377 pol->pd_reset_stats_fn(blkg);
381 spin_unlock_irq(&blkcg->lock);
382 mutex_unlock(&blkcg_pol_mutex);
383 return 0;
386 static const char *blkg_dev_name(struct blkcg_gq *blkg)
388 /* some drivers (floppy) instantiate a queue w/o disk registered */
389 if (blkg->q->backing_dev_info.dev)
390 return dev_name(blkg->q->backing_dev_info.dev);
391 return NULL;
395 * blkcg_print_blkgs - helper for printing per-blkg data
396 * @sf: seq_file to print to
397 * @blkcg: blkcg of interest
398 * @prfill: fill function to print out a blkg
399 * @pol: policy in question
400 * @data: data to be passed to @prfill
401 * @show_total: to print out sum of prfill return values or not
403 * This function invokes @prfill on each blkg of @blkcg if pd for the
404 * policy specified by @pol exists. @prfill is invoked with @sf, the
405 * policy data and @data. If @show_total is %true, the sum of the return
406 * values from @prfill is printed with "Total" label at the end.
408 * This is to be used to construct print functions for
409 * cftype->read_seq_string method.
411 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
412 u64 (*prfill)(struct seq_file *,
413 struct blkg_policy_data *, int),
414 const struct blkcg_policy *pol, int data,
415 bool show_total)
417 struct blkcg_gq *blkg;
418 struct hlist_node *n;
419 u64 total = 0;
421 spin_lock_irq(&blkcg->lock);
422 hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
423 if (blkcg_policy_enabled(blkg->q, pol))
424 total += prfill(sf, blkg->pd[pol->plid], data);
425 spin_unlock_irq(&blkcg->lock);
427 if (show_total)
428 seq_printf(sf, "Total %llu\n", (unsigned long long)total);
430 EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
433 * __blkg_prfill_u64 - prfill helper for a single u64 value
434 * @sf: seq_file to print to
435 * @pd: policy private data of interest
436 * @v: value to print
438 * Print @v to @sf for the device assocaited with @pd.
440 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
442 const char *dname = blkg_dev_name(pd->blkg);
444 if (!dname)
445 return 0;
447 seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
448 return v;
450 EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
453 * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
454 * @sf: seq_file to print to
455 * @pd: policy private data of interest
456 * @rwstat: rwstat to print
458 * Print @rwstat to @sf for the device assocaited with @pd.
460 u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
461 const struct blkg_rwstat *rwstat)
463 static const char *rwstr[] = {
464 [BLKG_RWSTAT_READ] = "Read",
465 [BLKG_RWSTAT_WRITE] = "Write",
466 [BLKG_RWSTAT_SYNC] = "Sync",
467 [BLKG_RWSTAT_ASYNC] = "Async",
469 const char *dname = blkg_dev_name(pd->blkg);
470 u64 v;
471 int i;
473 if (!dname)
474 return 0;
476 for (i = 0; i < BLKG_RWSTAT_NR; i++)
477 seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
478 (unsigned long long)rwstat->cnt[i]);
480 v = rwstat->cnt[BLKG_RWSTAT_READ] + rwstat->cnt[BLKG_RWSTAT_WRITE];
481 seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
482 return v;
486 * blkg_prfill_stat - prfill callback for blkg_stat
487 * @sf: seq_file to print to
488 * @pd: policy private data of interest
489 * @off: offset to the blkg_stat in @pd
491 * prfill callback for printing a blkg_stat.
493 u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off)
495 return __blkg_prfill_u64(sf, pd, blkg_stat_read((void *)pd + off));
497 EXPORT_SYMBOL_GPL(blkg_prfill_stat);
500 * blkg_prfill_rwstat - prfill callback for blkg_rwstat
501 * @sf: seq_file to print to
502 * @pd: policy private data of interest
503 * @off: offset to the blkg_rwstat in @pd
505 * prfill callback for printing a blkg_rwstat.
507 u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
508 int off)
510 struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd + off);
512 return __blkg_prfill_rwstat(sf, pd, &rwstat);
514 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
517 * blkg_conf_prep - parse and prepare for per-blkg config update
518 * @blkcg: target block cgroup
519 * @pol: target policy
520 * @input: input string
521 * @ctx: blkg_conf_ctx to be filled
523 * Parse per-blkg config update from @input and initialize @ctx with the
524 * result. @ctx->blkg points to the blkg to be updated and @ctx->v the new
525 * value. This function returns with RCU read lock and queue lock held and
526 * must be paired with blkg_conf_finish().
528 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
529 const char *input, struct blkg_conf_ctx *ctx)
530 __acquires(rcu) __acquires(disk->queue->queue_lock)
532 struct gendisk *disk;
533 struct blkcg_gq *blkg;
534 unsigned int major, minor;
535 unsigned long long v;
536 int part, ret;
538 if (sscanf(input, "%u:%u %llu", &major, &minor, &v) != 3)
539 return -EINVAL;
541 disk = get_gendisk(MKDEV(major, minor), &part);
542 if (!disk || part)
543 return -EINVAL;
545 rcu_read_lock();
546 spin_lock_irq(disk->queue->queue_lock);
548 if (blkcg_policy_enabled(disk->queue, pol))
549 blkg = blkg_lookup_create(blkcg, disk->queue);
550 else
551 blkg = ERR_PTR(-EINVAL);
553 if (IS_ERR(blkg)) {
554 ret = PTR_ERR(blkg);
555 rcu_read_unlock();
556 spin_unlock_irq(disk->queue->queue_lock);
557 put_disk(disk);
559 * If queue was bypassing, we should retry. Do so after a
560 * short msleep(). It isn't strictly necessary but queue
561 * can be bypassing for some time and it's always nice to
562 * avoid busy looping.
564 if (ret == -EBUSY) {
565 msleep(10);
566 ret = restart_syscall();
568 return ret;
571 ctx->disk = disk;
572 ctx->blkg = blkg;
573 ctx->v = v;
574 return 0;
576 EXPORT_SYMBOL_GPL(blkg_conf_prep);
579 * blkg_conf_finish - finish up per-blkg config update
580 * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
582 * Finish up after per-blkg config update. This function must be paired
583 * with blkg_conf_prep().
585 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
586 __releases(ctx->disk->queue->queue_lock) __releases(rcu)
588 spin_unlock_irq(ctx->disk->queue->queue_lock);
589 rcu_read_unlock();
590 put_disk(ctx->disk);
592 EXPORT_SYMBOL_GPL(blkg_conf_finish);
594 struct cftype blkcg_files[] = {
596 .name = "reset_stats",
597 .write_u64 = blkcg_reset_stats,
599 { } /* terminate */
603 * blkcg_css_offline - cgroup css_offline callback
604 * @cgroup: cgroup of interest
606 * This function is called when @cgroup is about to go away and responsible
607 * for shooting down all blkgs associated with @cgroup. blkgs should be
608 * removed while holding both q and blkcg locks. As blkcg lock is nested
609 * inside q lock, this function performs reverse double lock dancing.
611 * This is the blkcg counterpart of ioc_release_fn().
613 static void blkcg_css_offline(struct cgroup *cgroup)
615 struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
617 spin_lock_irq(&blkcg->lock);
619 while (!hlist_empty(&blkcg->blkg_list)) {
620 struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
621 struct blkcg_gq, blkcg_node);
622 struct request_queue *q = blkg->q;
624 if (spin_trylock(q->queue_lock)) {
625 blkg_destroy(blkg);
626 spin_unlock(q->queue_lock);
627 } else {
628 spin_unlock_irq(&blkcg->lock);
629 cpu_relax();
630 spin_lock_irq(&blkcg->lock);
634 spin_unlock_irq(&blkcg->lock);
637 static void blkcg_css_free(struct cgroup *cgroup)
639 struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
641 if (blkcg != &blkcg_root)
642 kfree(blkcg);
645 static struct cgroup_subsys_state *blkcg_css_alloc(struct cgroup *cgroup)
647 static atomic64_t id_seq = ATOMIC64_INIT(0);
648 struct blkcg *blkcg;
649 struct cgroup *parent = cgroup->parent;
651 if (!parent) {
652 blkcg = &blkcg_root;
653 goto done;
656 blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
657 if (!blkcg)
658 return ERR_PTR(-ENOMEM);
660 blkcg->cfq_weight = CFQ_WEIGHT_DEFAULT;
661 blkcg->id = atomic64_inc_return(&id_seq); /* root is 0, start from 1 */
662 done:
663 spin_lock_init(&blkcg->lock);
664 INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_ATOMIC);
665 INIT_HLIST_HEAD(&blkcg->blkg_list);
667 return &blkcg->css;
671 * blkcg_init_queue - initialize blkcg part of request queue
672 * @q: request_queue to initialize
674 * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
675 * part of new request_queue @q.
677 * RETURNS:
678 * 0 on success, -errno on failure.
680 int blkcg_init_queue(struct request_queue *q)
682 might_sleep();
684 return blk_throtl_init(q);
688 * blkcg_drain_queue - drain blkcg part of request_queue
689 * @q: request_queue to drain
691 * Called from blk_drain_queue(). Responsible for draining blkcg part.
693 void blkcg_drain_queue(struct request_queue *q)
695 lockdep_assert_held(q->queue_lock);
697 blk_throtl_drain(q);
701 * blkcg_exit_queue - exit and release blkcg part of request_queue
702 * @q: request_queue being released
704 * Called from blk_release_queue(). Responsible for exiting blkcg part.
706 void blkcg_exit_queue(struct request_queue *q)
708 spin_lock_irq(q->queue_lock);
709 blkg_destroy_all(q);
710 spin_unlock_irq(q->queue_lock);
712 blk_throtl_exit(q);
716 * We cannot support shared io contexts, as we have no mean to support
717 * two tasks with the same ioc in two different groups without major rework
718 * of the main cic data structures. For now we allow a task to change
719 * its cgroup only if it's the only owner of its ioc.
721 static int blkcg_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
723 struct task_struct *task;
724 struct io_context *ioc;
725 int ret = 0;
727 /* task_lock() is needed to avoid races with exit_io_context() */
728 cgroup_taskset_for_each(task, cgrp, tset) {
729 task_lock(task);
730 ioc = task->io_context;
731 if (ioc && atomic_read(&ioc->nr_tasks) > 1)
732 ret = -EINVAL;
733 task_unlock(task);
734 if (ret)
735 break;
737 return ret;
740 struct cgroup_subsys blkio_subsys = {
741 .name = "blkio",
742 .css_alloc = blkcg_css_alloc,
743 .css_offline = blkcg_css_offline,
744 .css_free = blkcg_css_free,
745 .can_attach = blkcg_can_attach,
746 .subsys_id = blkio_subsys_id,
747 .base_cftypes = blkcg_files,
748 .module = THIS_MODULE,
751 * blkio subsystem is utterly broken in terms of hierarchy support.
752 * It treats all cgroups equally regardless of where they're
753 * located in the hierarchy - all cgroups are treated as if they're
754 * right below the root. Fix it and remove the following.
756 .broken_hierarchy = true,
758 EXPORT_SYMBOL_GPL(blkio_subsys);
761 * blkcg_activate_policy - activate a blkcg policy on a request_queue
762 * @q: request_queue of interest
763 * @pol: blkcg policy to activate
765 * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through
766 * bypass mode to populate its blkgs with policy_data for @pol.
768 * Activation happens with @q bypassed, so nobody would be accessing blkgs
769 * from IO path. Update of each blkg is protected by both queue and blkcg
770 * locks so that holding either lock and testing blkcg_policy_enabled() is
771 * always enough for dereferencing policy data.
773 * The caller is responsible for synchronizing [de]activations and policy
774 * [un]registerations. Returns 0 on success, -errno on failure.
776 int blkcg_activate_policy(struct request_queue *q,
777 const struct blkcg_policy *pol)
779 LIST_HEAD(pds);
780 struct blkcg_gq *blkg;
781 struct blkg_policy_data *pd, *n;
782 int cnt = 0, ret;
783 bool preloaded;
785 if (blkcg_policy_enabled(q, pol))
786 return 0;
788 /* preallocations for root blkg */
789 blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
790 if (!blkg)
791 return -ENOMEM;
793 preloaded = !radix_tree_preload(GFP_KERNEL);
795 blk_queue_bypass_start(q);
797 /* make sure the root blkg exists and count the existing blkgs */
798 spin_lock_irq(q->queue_lock);
800 rcu_read_lock();
801 blkg = __blkg_lookup_create(&blkcg_root, q, blkg);
802 rcu_read_unlock();
804 if (preloaded)
805 radix_tree_preload_end();
807 if (IS_ERR(blkg)) {
808 ret = PTR_ERR(blkg);
809 goto out_unlock;
811 q->root_blkg = blkg;
812 q->root_rl.blkg = blkg;
814 list_for_each_entry(blkg, &q->blkg_list, q_node)
815 cnt++;
817 spin_unlock_irq(q->queue_lock);
819 /* allocate policy_data for all existing blkgs */
820 while (cnt--) {
821 pd = kzalloc_node(pol->pd_size, GFP_KERNEL, q->node);
822 if (!pd) {
823 ret = -ENOMEM;
824 goto out_free;
826 list_add_tail(&pd->alloc_node, &pds);
830 * Install the allocated pds. With @q bypassing, no new blkg
831 * should have been created while the queue lock was dropped.
833 spin_lock_irq(q->queue_lock);
835 list_for_each_entry(blkg, &q->blkg_list, q_node) {
836 if (WARN_ON(list_empty(&pds))) {
837 /* umm... this shouldn't happen, just abort */
838 ret = -ENOMEM;
839 goto out_unlock;
841 pd = list_first_entry(&pds, struct blkg_policy_data, alloc_node);
842 list_del_init(&pd->alloc_node);
844 /* grab blkcg lock too while installing @pd on @blkg */
845 spin_lock(&blkg->blkcg->lock);
847 blkg->pd[pol->plid] = pd;
848 pd->blkg = blkg;
849 pol->pd_init_fn(blkg);
851 spin_unlock(&blkg->blkcg->lock);
854 __set_bit(pol->plid, q->blkcg_pols);
855 ret = 0;
856 out_unlock:
857 spin_unlock_irq(q->queue_lock);
858 out_free:
859 blk_queue_bypass_end(q);
860 list_for_each_entry_safe(pd, n, &pds, alloc_node)
861 kfree(pd);
862 return ret;
864 EXPORT_SYMBOL_GPL(blkcg_activate_policy);
867 * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
868 * @q: request_queue of interest
869 * @pol: blkcg policy to deactivate
871 * Deactivate @pol on @q. Follows the same synchronization rules as
872 * blkcg_activate_policy().
874 void blkcg_deactivate_policy(struct request_queue *q,
875 const struct blkcg_policy *pol)
877 struct blkcg_gq *blkg;
879 if (!blkcg_policy_enabled(q, pol))
880 return;
882 blk_queue_bypass_start(q);
883 spin_lock_irq(q->queue_lock);
885 __clear_bit(pol->plid, q->blkcg_pols);
887 /* if no policy is left, no need for blkgs - shoot them down */
888 if (bitmap_empty(q->blkcg_pols, BLKCG_MAX_POLS))
889 blkg_destroy_all(q);
891 list_for_each_entry(blkg, &q->blkg_list, q_node) {
892 /* grab blkcg lock too while removing @pd from @blkg */
893 spin_lock(&blkg->blkcg->lock);
895 if (pol->pd_exit_fn)
896 pol->pd_exit_fn(blkg);
898 kfree(blkg->pd[pol->plid]);
899 blkg->pd[pol->plid] = NULL;
901 spin_unlock(&blkg->blkcg->lock);
904 spin_unlock_irq(q->queue_lock);
905 blk_queue_bypass_end(q);
907 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
910 * blkcg_policy_register - register a blkcg policy
911 * @pol: blkcg policy to register
913 * Register @pol with blkcg core. Might sleep and @pol may be modified on
914 * successful registration. Returns 0 on success and -errno on failure.
916 int blkcg_policy_register(struct blkcg_policy *pol)
918 int i, ret;
920 if (WARN_ON(pol->pd_size < sizeof(struct blkg_policy_data)))
921 return -EINVAL;
923 mutex_lock(&blkcg_pol_mutex);
925 /* find an empty slot */
926 ret = -ENOSPC;
927 for (i = 0; i < BLKCG_MAX_POLS; i++)
928 if (!blkcg_policy[i])
929 break;
930 if (i >= BLKCG_MAX_POLS)
931 goto out_unlock;
933 /* register and update blkgs */
934 pol->plid = i;
935 blkcg_policy[i] = pol;
937 /* everything is in place, add intf files for the new policy */
938 if (pol->cftypes)
939 WARN_ON(cgroup_add_cftypes(&blkio_subsys, pol->cftypes));
940 ret = 0;
941 out_unlock:
942 mutex_unlock(&blkcg_pol_mutex);
943 return ret;
945 EXPORT_SYMBOL_GPL(blkcg_policy_register);
948 * blkcg_policy_unregister - unregister a blkcg policy
949 * @pol: blkcg policy to unregister
951 * Undo blkcg_policy_register(@pol). Might sleep.
953 void blkcg_policy_unregister(struct blkcg_policy *pol)
955 mutex_lock(&blkcg_pol_mutex);
957 if (WARN_ON(blkcg_policy[pol->plid] != pol))
958 goto out_unlock;
960 /* kill the intf files first */
961 if (pol->cftypes)
962 cgroup_rm_cftypes(&blkio_subsys, pol->cftypes);
964 /* unregister and update blkgs */
965 blkcg_policy[pol->plid] = NULL;
966 out_unlock:
967 mutex_unlock(&blkcg_pol_mutex);
969 EXPORT_SYMBOL_GPL(blkcg_policy_unregister);