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 struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg,
36 struct request_queue *q, bool update_hint);
39 * blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants
40 * @d_blkg: loop cursor pointing to the current descendant
41 * @pos_cgrp: used for iteration
42 * @p_blkg: target blkg to walk descendants of
44 * Walk @c_blkg through the descendants of @p_blkg. Must be used with RCU
45 * read locked. If called under either blkcg or queue lock, the iteration
46 * is guaranteed to include all and only online blkgs. The caller may
47 * update @pos_cgrp by calling cgroup_rightmost_descendant() to skip
50 #define blkg_for_each_descendant_pre(d_blkg, pos_cgrp, p_blkg) \
51 cgroup_for_each_descendant_pre((pos_cgrp), (p_blkg)->blkcg->css.cgroup) \
52 if (((d_blkg) = __blkg_lookup(cgroup_to_blkcg(pos_cgrp), \
55 static bool blkcg_policy_enabled(struct request_queue *q,
56 const struct blkcg_policy *pol)
58 return pol && test_bit(pol->plid, q->blkcg_pols);
62 * blkg_free - free a blkg
65 * Free @blkg which may be partially allocated.
67 static void blkg_free(struct blkcg_gq *blkg)
74 for (i = 0; i < BLKCG_MAX_POLS; i++) {
75 struct blkcg_policy *pol = blkcg_policy[i];
76 struct blkg_policy_data *pd = blkg->pd[i];
81 if (pol && pol->pd_exit_fn)
82 pol->pd_exit_fn(blkg);
87 blk_exit_rl(&blkg->rl);
92 * blkg_alloc - allocate a blkg
93 * @blkcg: block cgroup the new blkg is associated with
94 * @q: request_queue the new blkg is associated with
95 * @gfp_mask: allocation mask to use
97 * Allocate a new blkg assocating @blkcg and @q.
99 static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
102 struct blkcg_gq *blkg;
105 /* alloc and init base part */
106 blkg = kzalloc_node(sizeof(*blkg), gfp_mask, q->node);
111 INIT_LIST_HEAD(&blkg->q_node);
115 /* root blkg uses @q->root_rl, init rl only for !root blkgs */
116 if (blkcg != &blkcg_root) {
117 if (blk_init_rl(&blkg->rl, q, gfp_mask))
119 blkg->rl.blkg = blkg;
122 for (i = 0; i < BLKCG_MAX_POLS; i++) {
123 struct blkcg_policy *pol = blkcg_policy[i];
124 struct blkg_policy_data *pd;
126 if (!blkcg_policy_enabled(q, pol))
129 /* alloc per-policy data and attach it to blkg */
130 pd = kzalloc_node(pol->pd_size, gfp_mask, q->node);
138 /* invoke per-policy init */
140 pol->pd_init_fn(blkg);
151 * __blkg_lookup - internal version of blkg_lookup()
152 * @blkcg: blkcg of interest
153 * @q: request_queue of interest
154 * @update_hint: whether to update lookup hint with the result or not
156 * This is internal version and shouldn't be used by policy
157 * implementations. Looks up blkgs for the @blkcg - @q pair regardless of
158 * @q's bypass state. If @update_hint is %true, the caller should be
159 * holding @q->queue_lock and lookup hint is updated on success.
161 static struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg,
162 struct request_queue *q, bool update_hint)
164 struct blkcg_gq *blkg;
166 blkg = rcu_dereference(blkcg->blkg_hint);
167 if (blkg && blkg->q == q)
171 * Hint didn't match. Look up from the radix tree. Note that the
172 * hint can only be updated under queue_lock as otherwise @blkg
173 * could have already been removed from blkg_tree. The caller is
174 * responsible for grabbing queue_lock if @update_hint.
176 blkg = radix_tree_lookup(&blkcg->blkg_tree, q->id);
177 if (blkg && blkg->q == q) {
179 lockdep_assert_held(q->queue_lock);
180 rcu_assign_pointer(blkcg->blkg_hint, blkg);
189 * blkg_lookup - lookup blkg for the specified blkcg - q pair
190 * @blkcg: blkcg of interest
191 * @q: request_queue of interest
193 * Lookup blkg for the @blkcg - @q pair. This function should be called
194 * under RCU read lock and is guaranteed to return %NULL if @q is bypassing
195 * - see blk_queue_bypass_start() for details.
197 struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, struct request_queue *q)
199 WARN_ON_ONCE(!rcu_read_lock_held());
201 if (unlikely(blk_queue_bypass(q)))
203 return __blkg_lookup(blkcg, q, false);
205 EXPORT_SYMBOL_GPL(blkg_lookup);
208 * If @new_blkg is %NULL, this function tries to allocate a new one as
209 * necessary using %GFP_ATOMIC. @new_blkg is always consumed on return.
211 static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
212 struct request_queue *q,
213 struct blkcg_gq *new_blkg)
215 struct blkcg_gq *blkg;
218 WARN_ON_ONCE(!rcu_read_lock_held());
219 lockdep_assert_held(q->queue_lock);
221 /* blkg holds a reference to blkcg */
222 if (!css_tryget(&blkcg->css)) {
229 new_blkg = blkg_alloc(blkcg, q, GFP_ATOMIC);
230 if (unlikely(!new_blkg)) {
237 /* link parent and insert */
238 if (blkcg_parent(blkcg)) {
239 blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false);
240 if (WARN_ON_ONCE(!blkg->parent)) {
241 blkg = ERR_PTR(-EINVAL);
244 blkg_get(blkg->parent);
247 spin_lock(&blkcg->lock);
248 ret = radix_tree_insert(&blkcg->blkg_tree, q->id, blkg);
250 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
251 list_add(&blkg->q_node, &q->blkg_list);
253 for (i = 0; i < BLKCG_MAX_POLS; i++) {
254 struct blkcg_policy *pol = blkcg_policy[i];
256 if (blkg->pd[i] && pol->pd_online_fn)
257 pol->pd_online_fn(blkg);
261 spin_unlock(&blkcg->lock);
266 /* @blkg failed fully initialized, use the usual release path */
271 css_put(&blkcg->css);
278 * blkg_lookup_create - lookup blkg, try to create one if not there
279 * @blkcg: blkcg of interest
280 * @q: request_queue of interest
282 * Lookup blkg for the @blkcg - @q pair. If it doesn't exist, try to
283 * create one. blkg creation is performed recursively from blkcg_root such
284 * that all non-root blkg's have access to the parent blkg. This function
285 * should be called under RCU read lock and @q->queue_lock.
287 * Returns pointer to the looked up or created blkg on success, ERR_PTR()
288 * value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not
289 * dead and bypassing, returns ERR_PTR(-EBUSY).
291 struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
292 struct request_queue *q)
294 struct blkcg_gq *blkg;
296 WARN_ON_ONCE(!rcu_read_lock_held());
297 lockdep_assert_held(q->queue_lock);
300 * This could be the first entry point of blkcg implementation and
301 * we shouldn't allow anything to go through for a bypassing queue.
303 if (unlikely(blk_queue_bypass(q)))
304 return ERR_PTR(blk_queue_dying(q) ? -EINVAL : -EBUSY);
306 blkg = __blkg_lookup(blkcg, q, true);
311 * Create blkgs walking down from blkcg_root to @blkcg, so that all
312 * non-root blkgs have access to their parents.
315 struct blkcg *pos = blkcg;
316 struct blkcg *parent = blkcg_parent(blkcg);
318 while (parent && !__blkg_lookup(parent, q, false)) {
320 parent = blkcg_parent(parent);
323 blkg = blkg_create(pos, q, NULL);
324 if (pos == blkcg || IS_ERR(blkg))
328 EXPORT_SYMBOL_GPL(blkg_lookup_create);
330 static void blkg_destroy(struct blkcg_gq *blkg)
332 struct blkcg *blkcg = blkg->blkcg;
335 lockdep_assert_held(blkg->q->queue_lock);
336 lockdep_assert_held(&blkcg->lock);
338 /* Something wrong if we are trying to remove same group twice */
339 WARN_ON_ONCE(list_empty(&blkg->q_node));
340 WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
342 for (i = 0; i < BLKCG_MAX_POLS; i++) {
343 struct blkcg_policy *pol = blkcg_policy[i];
345 if (blkg->pd[i] && pol->pd_offline_fn)
346 pol->pd_offline_fn(blkg);
348 blkg->online = false;
350 radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
351 list_del_init(&blkg->q_node);
352 hlist_del_init_rcu(&blkg->blkcg_node);
355 * Both setting lookup hint to and clearing it from @blkg are done
356 * under queue_lock. If it's not pointing to @blkg now, it never
357 * will. Hint assignment itself can race safely.
359 if (rcu_dereference_raw(blkcg->blkg_hint) == blkg)
360 rcu_assign_pointer(blkcg->blkg_hint, NULL);
363 * Put the reference taken at the time of creation so that when all
364 * queues are gone, group can be destroyed.
370 * blkg_destroy_all - destroy all blkgs associated with a request_queue
371 * @q: request_queue of interest
373 * Destroy all blkgs associated with @q.
375 static void blkg_destroy_all(struct request_queue *q)
377 struct blkcg_gq *blkg, *n;
379 lockdep_assert_held(q->queue_lock);
381 list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
382 struct blkcg *blkcg = blkg->blkcg;
384 spin_lock(&blkcg->lock);
386 spin_unlock(&blkcg->lock);
390 * root blkg is destroyed. Just clear the pointer since
391 * root_rl does not take reference on root blkg.
394 q->root_rl.blkg = NULL;
397 static void blkg_rcu_free(struct rcu_head *rcu_head)
399 blkg_free(container_of(rcu_head, struct blkcg_gq, rcu_head));
402 void __blkg_release(struct blkcg_gq *blkg)
404 /* release the blkcg and parent blkg refs this blkg has been holding */
405 css_put(&blkg->blkcg->css);
407 blkg_put(blkg->parent);
410 * A group is freed in rcu manner. But having an rcu lock does not
411 * mean that one can access all the fields of blkg and assume these
412 * are valid. For example, don't try to follow throtl_data and
413 * request queue links.
415 * Having a reference to blkg under an rcu allows acess to only
416 * values local to groups like group stats and group rate limits
418 call_rcu(&blkg->rcu_head, blkg_rcu_free);
420 EXPORT_SYMBOL_GPL(__blkg_release);
423 * The next function used by blk_queue_for_each_rl(). It's a bit tricky
424 * because the root blkg uses @q->root_rl instead of its own rl.
426 struct request_list *__blk_queue_next_rl(struct request_list *rl,
427 struct request_queue *q)
429 struct list_head *ent;
430 struct blkcg_gq *blkg;
433 * Determine the current blkg list_head. The first entry is
434 * root_rl which is off @q->blkg_list and mapped to the head.
436 if (rl == &q->root_rl) {
438 /* There are no more block groups, hence no request lists */
442 blkg = container_of(rl, struct blkcg_gq, rl);
446 /* walk to the next list_head, skip root blkcg */
448 if (ent == &q->root_blkg->q_node)
450 if (ent == &q->blkg_list)
453 blkg = container_of(ent, struct blkcg_gq, q_node);
457 static int blkcg_reset_stats(struct cgroup *cgroup, struct cftype *cftype,
460 struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
461 struct blkcg_gq *blkg;
462 struct hlist_node *n;
465 mutex_lock(&blkcg_pol_mutex);
466 spin_lock_irq(&blkcg->lock);
469 * Note that stat reset is racy - it doesn't synchronize against
470 * stat updates. This is a debug feature which shouldn't exist
471 * anyway. If you get hit by a race, retry.
473 hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
474 for (i = 0; i < BLKCG_MAX_POLS; i++) {
475 struct blkcg_policy *pol = blkcg_policy[i];
477 if (blkcg_policy_enabled(blkg->q, pol) &&
478 pol->pd_reset_stats_fn)
479 pol->pd_reset_stats_fn(blkg);
483 spin_unlock_irq(&blkcg->lock);
484 mutex_unlock(&blkcg_pol_mutex);
488 static const char *blkg_dev_name(struct blkcg_gq *blkg)
490 /* some drivers (floppy) instantiate a queue w/o disk registered */
491 if (blkg->q->backing_dev_info.dev)
492 return dev_name(blkg->q->backing_dev_info.dev);
497 * blkcg_print_blkgs - helper for printing per-blkg data
498 * @sf: seq_file to print to
499 * @blkcg: blkcg of interest
500 * @prfill: fill function to print out a blkg
501 * @pol: policy in question
502 * @data: data to be passed to @prfill
503 * @show_total: to print out sum of prfill return values or not
505 * This function invokes @prfill on each blkg of @blkcg if pd for the
506 * policy specified by @pol exists. @prfill is invoked with @sf, the
507 * policy data and @data and the matching queue lock held. If @show_total
508 * is %true, the sum of the return values from @prfill is printed with
509 * "Total" label at the end.
511 * This is to be used to construct print functions for
512 * cftype->read_seq_string method.
514 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
515 u64 (*prfill)(struct seq_file *,
516 struct blkg_policy_data *, int),
517 const struct blkcg_policy *pol, int data,
520 struct blkcg_gq *blkg;
521 struct hlist_node *n;
525 hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
526 spin_lock_irq(blkg->q->queue_lock);
527 if (blkcg_policy_enabled(blkg->q, pol))
528 total += prfill(sf, blkg->pd[pol->plid], data);
529 spin_unlock_irq(blkg->q->queue_lock);
534 seq_printf(sf, "Total %llu\n", (unsigned long long)total);
536 EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
539 * __blkg_prfill_u64 - prfill helper for a single u64 value
540 * @sf: seq_file to print to
541 * @pd: policy private data of interest
544 * Print @v to @sf for the device assocaited with @pd.
546 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
548 const char *dname = blkg_dev_name(pd->blkg);
553 seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
556 EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
559 * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
560 * @sf: seq_file to print to
561 * @pd: policy private data of interest
562 * @rwstat: rwstat to print
564 * Print @rwstat to @sf for the device assocaited with @pd.
566 u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
567 const struct blkg_rwstat *rwstat)
569 static const char *rwstr[] = {
570 [BLKG_RWSTAT_READ] = "Read",
571 [BLKG_RWSTAT_WRITE] = "Write",
572 [BLKG_RWSTAT_SYNC] = "Sync",
573 [BLKG_RWSTAT_ASYNC] = "Async",
575 const char *dname = blkg_dev_name(pd->blkg);
582 for (i = 0; i < BLKG_RWSTAT_NR; i++)
583 seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
584 (unsigned long long)rwstat->cnt[i]);
586 v = rwstat->cnt[BLKG_RWSTAT_READ] + rwstat->cnt[BLKG_RWSTAT_WRITE];
587 seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
590 EXPORT_SYMBOL_GPL(__blkg_prfill_rwstat);
593 * blkg_prfill_stat - prfill callback for blkg_stat
594 * @sf: seq_file to print to
595 * @pd: policy private data of interest
596 * @off: offset to the blkg_stat in @pd
598 * prfill callback for printing a blkg_stat.
600 u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off)
602 return __blkg_prfill_u64(sf, pd, blkg_stat_read((void *)pd + off));
604 EXPORT_SYMBOL_GPL(blkg_prfill_stat);
607 * blkg_prfill_rwstat - prfill callback for blkg_rwstat
608 * @sf: seq_file to print to
609 * @pd: policy private data of interest
610 * @off: offset to the blkg_rwstat in @pd
612 * prfill callback for printing a blkg_rwstat.
614 u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
617 struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd + off);
619 return __blkg_prfill_rwstat(sf, pd, &rwstat);
621 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
624 * blkg_stat_recursive_sum - collect hierarchical blkg_stat
625 * @pd: policy private data of interest
626 * @off: offset to the blkg_stat in @pd
628 * Collect the blkg_stat specified by @off from @pd and all its online
629 * descendants and return the sum. The caller must be holding the queue
630 * lock for online tests.
632 u64 blkg_stat_recursive_sum(struct blkg_policy_data *pd, int off)
634 struct blkcg_policy *pol = blkcg_policy[pd->plid];
635 struct blkcg_gq *pos_blkg;
636 struct cgroup *pos_cgrp;
639 lockdep_assert_held(pd->blkg->q->queue_lock);
641 sum = blkg_stat_read((void *)pd + off);
644 blkg_for_each_descendant_pre(pos_blkg, pos_cgrp, pd_to_blkg(pd)) {
645 struct blkg_policy_data *pos_pd = blkg_to_pd(pos_blkg, pol);
646 struct blkg_stat *stat = (void *)pos_pd + off;
648 if (pos_blkg->online)
649 sum += blkg_stat_read(stat);
655 EXPORT_SYMBOL_GPL(blkg_stat_recursive_sum);
658 * blkg_rwstat_recursive_sum - collect hierarchical blkg_rwstat
659 * @pd: policy private data of interest
660 * @off: offset to the blkg_stat in @pd
662 * Collect the blkg_rwstat specified by @off from @pd and all its online
663 * descendants and return the sum. The caller must be holding the queue
664 * lock for online tests.
666 struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkg_policy_data *pd,
669 struct blkcg_policy *pol = blkcg_policy[pd->plid];
670 struct blkcg_gq *pos_blkg;
671 struct cgroup *pos_cgrp;
672 struct blkg_rwstat sum;
675 lockdep_assert_held(pd->blkg->q->queue_lock);
677 sum = blkg_rwstat_read((void *)pd + off);
680 blkg_for_each_descendant_pre(pos_blkg, pos_cgrp, pd_to_blkg(pd)) {
681 struct blkg_policy_data *pos_pd = blkg_to_pd(pos_blkg, pol);
682 struct blkg_rwstat *rwstat = (void *)pos_pd + off;
683 struct blkg_rwstat tmp;
685 if (!pos_blkg->online)
688 tmp = blkg_rwstat_read(rwstat);
690 for (i = 0; i < BLKG_RWSTAT_NR; i++)
691 sum.cnt[i] += tmp.cnt[i];
697 EXPORT_SYMBOL_GPL(blkg_rwstat_recursive_sum);
700 * blkg_conf_prep - parse and prepare for per-blkg config update
701 * @blkcg: target block cgroup
702 * @pol: target policy
703 * @input: input string
704 * @ctx: blkg_conf_ctx to be filled
706 * Parse per-blkg config update from @input and initialize @ctx with the
707 * result. @ctx->blkg points to the blkg to be updated and @ctx->v the new
708 * value. This function returns with RCU read lock and queue lock held and
709 * must be paired with blkg_conf_finish().
711 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
712 const char *input, struct blkg_conf_ctx *ctx)
713 __acquires(rcu) __acquires(disk->queue->queue_lock)
715 struct gendisk *disk;
716 struct blkcg_gq *blkg;
717 unsigned int major, minor;
718 unsigned long long v;
721 if (sscanf(input, "%u:%u %llu", &major, &minor, &v) != 3)
724 disk = get_gendisk(MKDEV(major, minor), &part);
729 spin_lock_irq(disk->queue->queue_lock);
731 if (blkcg_policy_enabled(disk->queue, pol))
732 blkg = blkg_lookup_create(blkcg, disk->queue);
734 blkg = ERR_PTR(-EINVAL);
739 spin_unlock_irq(disk->queue->queue_lock);
742 * If queue was bypassing, we should retry. Do so after a
743 * short msleep(). It isn't strictly necessary but queue
744 * can be bypassing for some time and it's always nice to
745 * avoid busy looping.
749 ret = restart_syscall();
759 EXPORT_SYMBOL_GPL(blkg_conf_prep);
762 * blkg_conf_finish - finish up per-blkg config update
763 * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
765 * Finish up after per-blkg config update. This function must be paired
766 * with blkg_conf_prep().
768 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
769 __releases(ctx->disk->queue->queue_lock) __releases(rcu)
771 spin_unlock_irq(ctx->disk->queue->queue_lock);
775 EXPORT_SYMBOL_GPL(blkg_conf_finish);
777 struct cftype blkcg_files[] = {
779 .name = "reset_stats",
780 .write_u64 = blkcg_reset_stats,
786 * blkcg_css_offline - cgroup css_offline callback
787 * @cgroup: cgroup of interest
789 * This function is called when @cgroup is about to go away and responsible
790 * for shooting down all blkgs associated with @cgroup. blkgs should be
791 * removed while holding both q and blkcg locks. As blkcg lock is nested
792 * inside q lock, this function performs reverse double lock dancing.
794 * This is the blkcg counterpart of ioc_release_fn().
796 static void blkcg_css_offline(struct cgroup *cgroup)
798 struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
800 spin_lock_irq(&blkcg->lock);
802 while (!hlist_empty(&blkcg->blkg_list)) {
803 struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
804 struct blkcg_gq, blkcg_node);
805 struct request_queue *q = blkg->q;
807 if (spin_trylock(q->queue_lock)) {
809 spin_unlock(q->queue_lock);
811 spin_unlock_irq(&blkcg->lock);
813 spin_lock_irq(&blkcg->lock);
817 spin_unlock_irq(&blkcg->lock);
820 static void blkcg_css_free(struct cgroup *cgroup)
822 struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
824 if (blkcg != &blkcg_root)
828 static struct cgroup_subsys_state *blkcg_css_alloc(struct cgroup *cgroup)
830 static atomic64_t id_seq = ATOMIC64_INIT(0);
832 struct cgroup *parent = cgroup->parent;
839 blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
841 return ERR_PTR(-ENOMEM);
843 blkcg->cfq_weight = CFQ_WEIGHT_DEFAULT;
844 blkcg->cfq_leaf_weight = CFQ_WEIGHT_DEFAULT;
845 blkcg->id = atomic64_inc_return(&id_seq); /* root is 0, start from 1 */
847 spin_lock_init(&blkcg->lock);
848 INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_ATOMIC);
849 INIT_HLIST_HEAD(&blkcg->blkg_list);
855 * blkcg_init_queue - initialize blkcg part of request queue
856 * @q: request_queue to initialize
858 * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
859 * part of new request_queue @q.
862 * 0 on success, -errno on failure.
864 int blkcg_init_queue(struct request_queue *q)
868 return blk_throtl_init(q);
872 * blkcg_drain_queue - drain blkcg part of request_queue
873 * @q: request_queue to drain
875 * Called from blk_drain_queue(). Responsible for draining blkcg part.
877 void blkcg_drain_queue(struct request_queue *q)
879 lockdep_assert_held(q->queue_lock);
885 * blkcg_exit_queue - exit and release blkcg part of request_queue
886 * @q: request_queue being released
888 * Called from blk_release_queue(). Responsible for exiting blkcg part.
890 void blkcg_exit_queue(struct request_queue *q)
892 spin_lock_irq(q->queue_lock);
894 spin_unlock_irq(q->queue_lock);
900 * We cannot support shared io contexts, as we have no mean to support
901 * two tasks with the same ioc in two different groups without major rework
902 * of the main cic data structures. For now we allow a task to change
903 * its cgroup only if it's the only owner of its ioc.
905 static int blkcg_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
907 struct task_struct *task;
908 struct io_context *ioc;
911 /* task_lock() is needed to avoid races with exit_io_context() */
912 cgroup_taskset_for_each(task, cgrp, tset) {
914 ioc = task->io_context;
915 if (ioc && atomic_read(&ioc->nr_tasks) > 1)
924 struct cgroup_subsys blkio_subsys = {
926 .css_alloc = blkcg_css_alloc,
927 .css_offline = blkcg_css_offline,
928 .css_free = blkcg_css_free,
929 .can_attach = blkcg_can_attach,
930 .subsys_id = blkio_subsys_id,
931 .base_cftypes = blkcg_files,
932 .module = THIS_MODULE,
935 * blkio subsystem is utterly broken in terms of hierarchy support.
936 * It treats all cgroups equally regardless of where they're
937 * located in the hierarchy - all cgroups are treated as if they're
938 * right below the root. Fix it and remove the following.
940 .broken_hierarchy = true,
942 EXPORT_SYMBOL_GPL(blkio_subsys);
945 * blkcg_activate_policy - activate a blkcg policy on a request_queue
946 * @q: request_queue of interest
947 * @pol: blkcg policy to activate
949 * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through
950 * bypass mode to populate its blkgs with policy_data for @pol.
952 * Activation happens with @q bypassed, so nobody would be accessing blkgs
953 * from IO path. Update of each blkg is protected by both queue and blkcg
954 * locks so that holding either lock and testing blkcg_policy_enabled() is
955 * always enough for dereferencing policy data.
957 * The caller is responsible for synchronizing [de]activations and policy
958 * [un]registerations. Returns 0 on success, -errno on failure.
960 int blkcg_activate_policy(struct request_queue *q,
961 const struct blkcg_policy *pol)
964 struct blkcg_gq *blkg, *new_blkg;
965 struct blkg_policy_data *pd, *n;
969 if (blkcg_policy_enabled(q, pol))
972 /* preallocations for root blkg */
973 new_blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
977 preloaded = !radix_tree_preload(GFP_KERNEL);
979 blk_queue_bypass_start(q);
982 * Make sure the root blkg exists and count the existing blkgs. As
983 * @q is bypassing at this point, blkg_lookup_create() can't be
984 * used. Open code it.
986 spin_lock_irq(q->queue_lock);
989 blkg = __blkg_lookup(&blkcg_root, q, false);
993 blkg = blkg_create(&blkcg_root, q, new_blkg);
997 radix_tree_preload_end();
1000 ret = PTR_ERR(blkg);
1003 q->root_blkg = blkg;
1004 q->root_rl.blkg = blkg;
1006 list_for_each_entry(blkg, &q->blkg_list, q_node)
1009 spin_unlock_irq(q->queue_lock);
1011 /* allocate policy_data for all existing blkgs */
1013 pd = kzalloc_node(pol->pd_size, GFP_KERNEL, q->node);
1018 list_add_tail(&pd->alloc_node, &pds);
1022 * Install the allocated pds. With @q bypassing, no new blkg
1023 * should have been created while the queue lock was dropped.
1025 spin_lock_irq(q->queue_lock);
1027 list_for_each_entry(blkg, &q->blkg_list, q_node) {
1028 if (WARN_ON(list_empty(&pds))) {
1029 /* umm... this shouldn't happen, just abort */
1033 pd = list_first_entry(&pds, struct blkg_policy_data, alloc_node);
1034 list_del_init(&pd->alloc_node);
1036 /* grab blkcg lock too while installing @pd on @blkg */
1037 spin_lock(&blkg->blkcg->lock);
1039 blkg->pd[pol->plid] = pd;
1041 pd->plid = pol->plid;
1042 pol->pd_init_fn(blkg);
1044 spin_unlock(&blkg->blkcg->lock);
1047 __set_bit(pol->plid, q->blkcg_pols);
1050 spin_unlock_irq(q->queue_lock);
1052 blk_queue_bypass_end(q);
1053 list_for_each_entry_safe(pd, n, &pds, alloc_node)
1057 EXPORT_SYMBOL_GPL(blkcg_activate_policy);
1060 * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
1061 * @q: request_queue of interest
1062 * @pol: blkcg policy to deactivate
1064 * Deactivate @pol on @q. Follows the same synchronization rules as
1065 * blkcg_activate_policy().
1067 void blkcg_deactivate_policy(struct request_queue *q,
1068 const struct blkcg_policy *pol)
1070 struct blkcg_gq *blkg;
1072 if (!blkcg_policy_enabled(q, pol))
1075 blk_queue_bypass_start(q);
1076 spin_lock_irq(q->queue_lock);
1078 __clear_bit(pol->plid, q->blkcg_pols);
1080 /* if no policy is left, no need for blkgs - shoot them down */
1081 if (bitmap_empty(q->blkcg_pols, BLKCG_MAX_POLS))
1082 blkg_destroy_all(q);
1084 list_for_each_entry(blkg, &q->blkg_list, q_node) {
1085 /* grab blkcg lock too while removing @pd from @blkg */
1086 spin_lock(&blkg->blkcg->lock);
1088 if (pol->pd_offline_fn)
1089 pol->pd_offline_fn(blkg);
1090 if (pol->pd_exit_fn)
1091 pol->pd_exit_fn(blkg);
1093 kfree(blkg->pd[pol->plid]);
1094 blkg->pd[pol->plid] = NULL;
1096 spin_unlock(&blkg->blkcg->lock);
1099 spin_unlock_irq(q->queue_lock);
1100 blk_queue_bypass_end(q);
1102 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
1105 * blkcg_policy_register - register a blkcg policy
1106 * @pol: blkcg policy to register
1108 * Register @pol with blkcg core. Might sleep and @pol may be modified on
1109 * successful registration. Returns 0 on success and -errno on failure.
1111 int blkcg_policy_register(struct blkcg_policy *pol)
1115 if (WARN_ON(pol->pd_size < sizeof(struct blkg_policy_data)))
1118 mutex_lock(&blkcg_pol_mutex);
1120 /* find an empty slot */
1122 for (i = 0; i < BLKCG_MAX_POLS; i++)
1123 if (!blkcg_policy[i])
1125 if (i >= BLKCG_MAX_POLS)
1128 /* register and update blkgs */
1130 blkcg_policy[i] = pol;
1132 /* everything is in place, add intf files for the new policy */
1134 WARN_ON(cgroup_add_cftypes(&blkio_subsys, pol->cftypes));
1137 mutex_unlock(&blkcg_pol_mutex);
1140 EXPORT_SYMBOL_GPL(blkcg_policy_register);
1143 * blkcg_policy_unregister - unregister a blkcg policy
1144 * @pol: blkcg policy to unregister
1146 * Undo blkcg_policy_register(@pol). Might sleep.
1148 void blkcg_policy_unregister(struct blkcg_policy *pol)
1150 mutex_lock(&blkcg_pol_mutex);
1152 if (WARN_ON(blkcg_policy[pol->plid] != pol))
1155 /* kill the intf files first */
1157 cgroup_rm_cftypes(&blkio_subsys, pol->cftypes);
1159 /* unregister and update blkgs */
1160 blkcg_policy[pol->plid] = NULL;
1162 mutex_unlock(&blkcg_pol_mutex);
1164 EXPORT_SYMBOL_GPL(blkcg_policy_unregister);