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 * For policy-specific per-blkcg data:
14 * Copyright (C) 2015 Paolo Valente <paolo.valente@unimore.it>
15 * Arianna Avanzini <avanzini.arianna@gmail.com>
17 #include <linux/ioprio.h>
18 #include <linux/kdev_t.h>
19 #include <linux/module.h>
20 #include <linux/err.h>
21 #include <linux/blkdev.h>
22 #include <linux/backing-dev.h>
23 #include <linux/slab.h>
24 #include <linux/genhd.h>
25 #include <linux/delay.h>
26 #include <linux/atomic.h>
27 #include <linux/blk-cgroup.h>
30 #define MAX_KEY_LEN 100
33 * blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation.
34 * blkcg_pol_register_mutex nests outside of it and synchronizes entire
35 * policy [un]register operations including cgroup file additions /
36 * removals. Putting cgroup file registration outside blkcg_pol_mutex
37 * allows grabbing it from cgroup callbacks.
39 static DEFINE_MUTEX(blkcg_pol_register_mutex);
40 static DEFINE_MUTEX(blkcg_pol_mutex);
42 struct blkcg blkcg_root;
43 EXPORT_SYMBOL_GPL(blkcg_root);
45 struct cgroup_subsys_state * const blkcg_root_css = &blkcg_root.css;
47 static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];
49 static LIST_HEAD(all_blkcgs); /* protected by blkcg_pol_mutex */
51 static bool blkcg_policy_enabled(struct request_queue *q,
52 const struct blkcg_policy *pol)
54 return pol && test_bit(pol->plid, q->blkcg_pols);
58 * blkg_free - free a blkg
61 * Free @blkg which may be partially allocated.
63 static void blkg_free(struct blkcg_gq *blkg)
70 for (i = 0; i < BLKCG_MAX_POLS; i++)
72 blkcg_policy[i]->pd_free_fn(blkg->pd[i]);
74 if (blkg->blkcg != &blkcg_root)
75 blk_exit_rl(&blkg->rl);
77 blkg_rwstat_exit(&blkg->stat_ios);
78 blkg_rwstat_exit(&blkg->stat_bytes);
83 * blkg_alloc - allocate a blkg
84 * @blkcg: block cgroup the new blkg is associated with
85 * @q: request_queue the new blkg is associated with
86 * @gfp_mask: allocation mask to use
88 * Allocate a new blkg assocating @blkcg and @q.
90 static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
93 struct blkcg_gq *blkg;
96 /* alloc and init base part */
97 blkg = kzalloc_node(sizeof(*blkg), gfp_mask, q->node);
101 if (blkg_rwstat_init(&blkg->stat_bytes, gfp_mask) ||
102 blkg_rwstat_init(&blkg->stat_ios, gfp_mask))
106 INIT_LIST_HEAD(&blkg->q_node);
108 atomic_set(&blkg->refcnt, 1);
110 /* root blkg uses @q->root_rl, init rl only for !root blkgs */
111 if (blkcg != &blkcg_root) {
112 if (blk_init_rl(&blkg->rl, q, gfp_mask))
114 blkg->rl.blkg = blkg;
117 for (i = 0; i < BLKCG_MAX_POLS; i++) {
118 struct blkcg_policy *pol = blkcg_policy[i];
119 struct blkg_policy_data *pd;
121 if (!blkcg_policy_enabled(q, pol))
124 /* alloc per-policy data and attach it to blkg */
125 pd = pol->pd_alloc_fn(gfp_mask, q->node);
141 struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
142 struct request_queue *q, bool update_hint)
144 struct blkcg_gq *blkg;
147 * Hint didn't match. Look up from the radix tree. Note that the
148 * hint can only be updated under queue_lock as otherwise @blkg
149 * could have already been removed from blkg_tree. The caller is
150 * responsible for grabbing queue_lock if @update_hint.
152 blkg = radix_tree_lookup(&blkcg->blkg_tree, q->id);
153 if (blkg && blkg->q == q) {
155 lockdep_assert_held(q->queue_lock);
156 rcu_assign_pointer(blkcg->blkg_hint, blkg);
163 EXPORT_SYMBOL_GPL(blkg_lookup_slowpath);
166 * If @new_blkg is %NULL, this function tries to allocate a new one as
167 * necessary using %GFP_NOWAIT. @new_blkg is always consumed on return.
169 static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
170 struct request_queue *q,
171 struct blkcg_gq *new_blkg)
173 struct blkcg_gq *blkg;
174 struct bdi_writeback_congested *wb_congested;
177 WARN_ON_ONCE(!rcu_read_lock_held());
178 lockdep_assert_held(q->queue_lock);
180 /* blkg holds a reference to blkcg */
181 if (!css_tryget_online(&blkcg->css)) {
186 wb_congested = wb_congested_get_create(&q->backing_dev_info,
187 blkcg->css.id, GFP_NOWAIT);
195 new_blkg = blkg_alloc(blkcg, q, GFP_NOWAIT);
196 if (unlikely(!new_blkg)) {
198 goto err_put_congested;
202 blkg->wb_congested = wb_congested;
205 if (blkcg_parent(blkcg)) {
206 blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false);
207 if (WARN_ON_ONCE(!blkg->parent)) {
209 goto err_put_congested;
211 blkg_get(blkg->parent);
214 /* invoke per-policy init */
215 for (i = 0; i < BLKCG_MAX_POLS; i++) {
216 struct blkcg_policy *pol = blkcg_policy[i];
218 if (blkg->pd[i] && pol->pd_init_fn)
219 pol->pd_init_fn(blkg->pd[i]);
223 spin_lock(&blkcg->lock);
224 ret = radix_tree_insert(&blkcg->blkg_tree, q->id, blkg);
226 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
227 list_add(&blkg->q_node, &q->blkg_list);
229 for (i = 0; i < BLKCG_MAX_POLS; i++) {
230 struct blkcg_policy *pol = blkcg_policy[i];
232 if (blkg->pd[i] && pol->pd_online_fn)
233 pol->pd_online_fn(blkg->pd[i]);
237 spin_unlock(&blkcg->lock);
242 /* @blkg failed fully initialized, use the usual release path */
247 wb_congested_put(wb_congested);
249 css_put(&blkcg->css);
256 * blkg_lookup_create - lookup blkg, try to create one if not there
257 * @blkcg: blkcg of interest
258 * @q: request_queue of interest
260 * Lookup blkg for the @blkcg - @q pair. If it doesn't exist, try to
261 * create one. blkg creation is performed recursively from blkcg_root such
262 * that all non-root blkg's have access to the parent blkg. This function
263 * should be called under RCU read lock and @q->queue_lock.
265 * Returns pointer to the looked up or created blkg on success, ERR_PTR()
266 * value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not
267 * dead and bypassing, returns ERR_PTR(-EBUSY).
269 struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
270 struct request_queue *q)
272 struct blkcg_gq *blkg;
274 WARN_ON_ONCE(!rcu_read_lock_held());
275 lockdep_assert_held(q->queue_lock);
278 * This could be the first entry point of blkcg implementation and
279 * we shouldn't allow anything to go through for a bypassing queue.
281 if (unlikely(blk_queue_bypass(q)))
282 return ERR_PTR(blk_queue_dying(q) ? -EINVAL : -EBUSY);
284 blkg = __blkg_lookup(blkcg, q, true);
289 * Create blkgs walking down from blkcg_root to @blkcg, so that all
290 * non-root blkgs have access to their parents.
293 struct blkcg *pos = blkcg;
294 struct blkcg *parent = blkcg_parent(blkcg);
296 while (parent && !__blkg_lookup(parent, q, false)) {
298 parent = blkcg_parent(parent);
301 blkg = blkg_create(pos, q, NULL);
302 if (pos == blkcg || IS_ERR(blkg))
307 static void blkg_destroy(struct blkcg_gq *blkg)
309 struct blkcg *blkcg = blkg->blkcg;
310 struct blkcg_gq *parent = blkg->parent;
313 lockdep_assert_held(blkg->q->queue_lock);
314 lockdep_assert_held(&blkcg->lock);
316 /* Something wrong if we are trying to remove same group twice */
317 WARN_ON_ONCE(list_empty(&blkg->q_node));
318 WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
320 for (i = 0; i < BLKCG_MAX_POLS; i++) {
321 struct blkcg_policy *pol = blkcg_policy[i];
323 if (blkg->pd[i] && pol->pd_offline_fn)
324 pol->pd_offline_fn(blkg->pd[i]);
328 blkg_rwstat_add_aux(&parent->stat_bytes, &blkg->stat_bytes);
329 blkg_rwstat_add_aux(&parent->stat_ios, &blkg->stat_ios);
332 blkg->online = false;
334 radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
335 list_del_init(&blkg->q_node);
336 hlist_del_init_rcu(&blkg->blkcg_node);
339 * Both setting lookup hint to and clearing it from @blkg are done
340 * under queue_lock. If it's not pointing to @blkg now, it never
341 * will. Hint assignment itself can race safely.
343 if (rcu_access_pointer(blkcg->blkg_hint) == blkg)
344 rcu_assign_pointer(blkcg->blkg_hint, NULL);
347 * Put the reference taken at the time of creation so that when all
348 * queues are gone, group can be destroyed.
354 * blkg_destroy_all - destroy all blkgs associated with a request_queue
355 * @q: request_queue of interest
357 * Destroy all blkgs associated with @q.
359 static void blkg_destroy_all(struct request_queue *q)
361 struct blkcg_gq *blkg, *n;
363 lockdep_assert_held(q->queue_lock);
365 list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
366 struct blkcg *blkcg = blkg->blkcg;
368 spin_lock(&blkcg->lock);
370 spin_unlock(&blkcg->lock);
375 * A group is RCU protected, but having an rcu lock does not mean that one
376 * can access all the fields of blkg and assume these are valid. For
377 * example, don't try to follow throtl_data and request queue links.
379 * Having a reference to blkg under an rcu allows accesses to only values
380 * local to groups like group stats and group rate limits.
382 void __blkg_release_rcu(struct rcu_head *rcu_head)
384 struct blkcg_gq *blkg = container_of(rcu_head, struct blkcg_gq, rcu_head);
386 /* release the blkcg and parent blkg refs this blkg has been holding */
387 css_put(&blkg->blkcg->css);
389 blkg_put(blkg->parent);
391 wb_congested_put(blkg->wb_congested);
395 EXPORT_SYMBOL_GPL(__blkg_release_rcu);
398 * The next function used by blk_queue_for_each_rl(). It's a bit tricky
399 * because the root blkg uses @q->root_rl instead of its own rl.
401 struct request_list *__blk_queue_next_rl(struct request_list *rl,
402 struct request_queue *q)
404 struct list_head *ent;
405 struct blkcg_gq *blkg;
408 * Determine the current blkg list_head. The first entry is
409 * root_rl which is off @q->blkg_list and mapped to the head.
411 if (rl == &q->root_rl) {
413 /* There are no more block groups, hence no request lists */
417 blkg = container_of(rl, struct blkcg_gq, rl);
421 /* walk to the next list_head, skip root blkcg */
423 if (ent == &q->root_blkg->q_node)
425 if (ent == &q->blkg_list)
428 blkg = container_of(ent, struct blkcg_gq, q_node);
432 static int blkcg_reset_stats(struct cgroup_subsys_state *css,
433 struct cftype *cftype, u64 val)
435 struct blkcg *blkcg = css_to_blkcg(css);
436 struct blkcg_gq *blkg;
439 mutex_lock(&blkcg_pol_mutex);
440 spin_lock_irq(&blkcg->lock);
443 * Note that stat reset is racy - it doesn't synchronize against
444 * stat updates. This is a debug feature which shouldn't exist
445 * anyway. If you get hit by a race, retry.
447 hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
448 blkg_rwstat_reset(&blkg->stat_bytes);
449 blkg_rwstat_reset(&blkg->stat_ios);
451 for (i = 0; i < BLKCG_MAX_POLS; i++) {
452 struct blkcg_policy *pol = blkcg_policy[i];
454 if (blkg->pd[i] && pol->pd_reset_stats_fn)
455 pol->pd_reset_stats_fn(blkg->pd[i]);
459 spin_unlock_irq(&blkcg->lock);
460 mutex_unlock(&blkcg_pol_mutex);
464 static const char *blkg_dev_name(struct blkcg_gq *blkg)
466 /* some drivers (floppy) instantiate a queue w/o disk registered */
467 if (blkg->q->backing_dev_info.dev)
468 return dev_name(blkg->q->backing_dev_info.dev);
473 * blkcg_print_blkgs - helper for printing per-blkg data
474 * @sf: seq_file to print to
475 * @blkcg: blkcg of interest
476 * @prfill: fill function to print out a blkg
477 * @pol: policy in question
478 * @data: data to be passed to @prfill
479 * @show_total: to print out sum of prfill return values or not
481 * This function invokes @prfill on each blkg of @blkcg if pd for the
482 * policy specified by @pol exists. @prfill is invoked with @sf, the
483 * policy data and @data and the matching queue lock held. If @show_total
484 * is %true, the sum of the return values from @prfill is printed with
485 * "Total" label at the end.
487 * This is to be used to construct print functions for
488 * cftype->read_seq_string method.
490 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
491 u64 (*prfill)(struct seq_file *,
492 struct blkg_policy_data *, int),
493 const struct blkcg_policy *pol, int data,
496 struct blkcg_gq *blkg;
500 hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
501 spin_lock_irq(blkg->q->queue_lock);
502 if (blkcg_policy_enabled(blkg->q, pol))
503 total += prfill(sf, blkg->pd[pol->plid], data);
504 spin_unlock_irq(blkg->q->queue_lock);
509 seq_printf(sf, "Total %llu\n", (unsigned long long)total);
511 EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
514 * __blkg_prfill_u64 - prfill helper for a single u64 value
515 * @sf: seq_file to print to
516 * @pd: policy private data of interest
519 * Print @v to @sf for the device assocaited with @pd.
521 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
523 const char *dname = blkg_dev_name(pd->blkg);
528 seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
531 EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
534 * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
535 * @sf: seq_file to print to
536 * @pd: policy private data of interest
537 * @rwstat: rwstat to print
539 * Print @rwstat to @sf for the device assocaited with @pd.
541 u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
542 const struct blkg_rwstat *rwstat)
544 static const char *rwstr[] = {
545 [BLKG_RWSTAT_READ] = "Read",
546 [BLKG_RWSTAT_WRITE] = "Write",
547 [BLKG_RWSTAT_SYNC] = "Sync",
548 [BLKG_RWSTAT_ASYNC] = "Async",
550 const char *dname = blkg_dev_name(pd->blkg);
557 for (i = 0; i < BLKG_RWSTAT_NR; i++)
558 seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
559 (unsigned long long)atomic64_read(&rwstat->aux_cnt[i]));
561 v = atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_READ]) +
562 atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_WRITE]);
563 seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
566 EXPORT_SYMBOL_GPL(__blkg_prfill_rwstat);
569 * blkg_prfill_stat - prfill callback for blkg_stat
570 * @sf: seq_file to print to
571 * @pd: policy private data of interest
572 * @off: offset to the blkg_stat in @pd
574 * prfill callback for printing a blkg_stat.
576 u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off)
578 return __blkg_prfill_u64(sf, pd, blkg_stat_read((void *)pd + off));
580 EXPORT_SYMBOL_GPL(blkg_prfill_stat);
583 * blkg_prfill_rwstat - prfill callback for blkg_rwstat
584 * @sf: seq_file to print to
585 * @pd: policy private data of interest
586 * @off: offset to the blkg_rwstat in @pd
588 * prfill callback for printing a blkg_rwstat.
590 u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
593 struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd + off);
595 return __blkg_prfill_rwstat(sf, pd, &rwstat);
597 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
599 static u64 blkg_prfill_rwstat_field(struct seq_file *sf,
600 struct blkg_policy_data *pd, int off)
602 struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd->blkg + off);
604 return __blkg_prfill_rwstat(sf, pd, &rwstat);
608 * blkg_print_stat_bytes - seq_show callback for blkg->stat_bytes
609 * @sf: seq_file to print to
612 * To be used as cftype->seq_show to print blkg->stat_bytes.
613 * cftype->private must be set to the blkcg_policy.
615 int blkg_print_stat_bytes(struct seq_file *sf, void *v)
617 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
618 blkg_prfill_rwstat_field, (void *)seq_cft(sf)->private,
619 offsetof(struct blkcg_gq, stat_bytes), true);
622 EXPORT_SYMBOL_GPL(blkg_print_stat_bytes);
625 * blkg_print_stat_bytes - seq_show callback for blkg->stat_ios
626 * @sf: seq_file to print to
629 * To be used as cftype->seq_show to print blkg->stat_ios. cftype->private
630 * must be set to the blkcg_policy.
632 int blkg_print_stat_ios(struct seq_file *sf, void *v)
634 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
635 blkg_prfill_rwstat_field, (void *)seq_cft(sf)->private,
636 offsetof(struct blkcg_gq, stat_ios), true);
639 EXPORT_SYMBOL_GPL(blkg_print_stat_ios);
641 static u64 blkg_prfill_rwstat_field_recursive(struct seq_file *sf,
642 struct blkg_policy_data *pd,
645 struct blkg_rwstat rwstat = blkg_rwstat_recursive_sum(pd->blkg,
647 return __blkg_prfill_rwstat(sf, pd, &rwstat);
651 * blkg_print_stat_bytes_recursive - recursive version of blkg_print_stat_bytes
652 * @sf: seq_file to print to
655 int blkg_print_stat_bytes_recursive(struct seq_file *sf, void *v)
657 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
658 blkg_prfill_rwstat_field_recursive,
659 (void *)seq_cft(sf)->private,
660 offsetof(struct blkcg_gq, stat_bytes), true);
663 EXPORT_SYMBOL_GPL(blkg_print_stat_bytes_recursive);
666 * blkg_print_stat_ios_recursive - recursive version of blkg_print_stat_ios
667 * @sf: seq_file to print to
670 int blkg_print_stat_ios_recursive(struct seq_file *sf, void *v)
672 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
673 blkg_prfill_rwstat_field_recursive,
674 (void *)seq_cft(sf)->private,
675 offsetof(struct blkcg_gq, stat_ios), true);
678 EXPORT_SYMBOL_GPL(blkg_print_stat_ios_recursive);
681 * blkg_stat_recursive_sum - collect hierarchical blkg_stat
682 * @blkg: blkg of interest
683 * @pol: blkcg_policy which contains the blkg_stat
684 * @off: offset to the blkg_stat in blkg_policy_data or @blkg
686 * Collect the blkg_stat specified by @blkg, @pol and @off and all its
687 * online descendants and their aux counts. The caller must be holding the
688 * queue lock for online tests.
690 * If @pol is NULL, blkg_stat is at @off bytes into @blkg; otherwise, it is
691 * at @off bytes into @blkg's blkg_policy_data of the policy.
693 u64 blkg_stat_recursive_sum(struct blkcg_gq *blkg,
694 struct blkcg_policy *pol, int off)
696 struct blkcg_gq *pos_blkg;
697 struct cgroup_subsys_state *pos_css;
700 lockdep_assert_held(blkg->q->queue_lock);
703 blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
704 struct blkg_stat *stat;
706 if (!pos_blkg->online)
710 stat = (void *)blkg_to_pd(pos_blkg, pol) + off;
712 stat = (void *)blkg + off;
714 sum += blkg_stat_read(stat) + atomic64_read(&stat->aux_cnt);
720 EXPORT_SYMBOL_GPL(blkg_stat_recursive_sum);
723 * blkg_rwstat_recursive_sum - collect hierarchical blkg_rwstat
724 * @blkg: blkg of interest
725 * @pol: blkcg_policy which contains the blkg_rwstat
726 * @off: offset to the blkg_rwstat in blkg_policy_data or @blkg
728 * Collect the blkg_rwstat specified by @blkg, @pol and @off and all its
729 * online descendants and their aux counts. The caller must be holding the
730 * queue lock for online tests.
732 * If @pol is NULL, blkg_rwstat is at @off bytes into @blkg; otherwise, it
733 * is at @off bytes into @blkg's blkg_policy_data of the policy.
735 struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkcg_gq *blkg,
736 struct blkcg_policy *pol, int off)
738 struct blkcg_gq *pos_blkg;
739 struct cgroup_subsys_state *pos_css;
740 struct blkg_rwstat sum = { };
743 lockdep_assert_held(blkg->q->queue_lock);
746 blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
747 struct blkg_rwstat *rwstat, tmp;
749 if (!pos_blkg->online)
753 rwstat = (void *)blkg_to_pd(pos_blkg, pol) + off;
755 rwstat = (void *)pos_blkg + off;
757 tmp = blkg_rwstat_read(rwstat);
759 for (i = 0; i < BLKG_RWSTAT_NR; i++)
760 atomic64_add(atomic64_read(&tmp.aux_cnt[i]) +
761 atomic64_read(&rwstat->aux_cnt[i]),
768 EXPORT_SYMBOL_GPL(blkg_rwstat_recursive_sum);
771 * blkg_conf_prep - parse and prepare for per-blkg config update
772 * @blkcg: target block cgroup
773 * @pol: target policy
774 * @input: input string
775 * @ctx: blkg_conf_ctx to be filled
777 * Parse per-blkg config update from @input and initialize @ctx with the
778 * result. @ctx->blkg points to the blkg to be updated and @ctx->v the new
779 * value. This function returns with RCU read lock and queue lock held and
780 * must be paired with blkg_conf_finish().
782 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
783 const char *input, struct blkg_conf_ctx *ctx)
784 __acquires(rcu) __acquires(disk->queue->queue_lock)
786 struct gendisk *disk;
787 struct blkcg_gq *blkg;
788 unsigned int major, minor;
789 unsigned long long v;
792 if (sscanf(input, "%u:%u %llu", &major, &minor, &v) != 3)
795 disk = get_gendisk(MKDEV(major, minor), &part);
804 spin_lock_irq(disk->queue->queue_lock);
806 if (blkcg_policy_enabled(disk->queue, pol))
807 blkg = blkg_lookup_create(blkcg, disk->queue);
809 blkg = ERR_PTR(-EINVAL);
814 spin_unlock_irq(disk->queue->queue_lock);
817 * If queue was bypassing, we should retry. Do so after a
818 * short msleep(). It isn't strictly necessary but queue
819 * can be bypassing for some time and it's always nice to
820 * avoid busy looping.
824 ret = restart_syscall();
834 EXPORT_SYMBOL_GPL(blkg_conf_prep);
837 * blkg_conf_finish - finish up per-blkg config update
838 * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
840 * Finish up after per-blkg config update. This function must be paired
841 * with blkg_conf_prep().
843 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
844 __releases(ctx->disk->queue->queue_lock) __releases(rcu)
846 spin_unlock_irq(ctx->disk->queue->queue_lock);
850 EXPORT_SYMBOL_GPL(blkg_conf_finish);
852 struct cftype blkcg_files[] = {
854 .name = "reset_stats",
855 .write_u64 = blkcg_reset_stats,
861 * blkcg_css_offline - cgroup css_offline callback
862 * @css: css of interest
864 * This function is called when @css is about to go away and responsible
865 * for shooting down all blkgs associated with @css. blkgs should be
866 * removed while holding both q and blkcg locks. As blkcg lock is nested
867 * inside q lock, this function performs reverse double lock dancing.
869 * This is the blkcg counterpart of ioc_release_fn().
871 static void blkcg_css_offline(struct cgroup_subsys_state *css)
873 struct blkcg *blkcg = css_to_blkcg(css);
875 spin_lock_irq(&blkcg->lock);
877 while (!hlist_empty(&blkcg->blkg_list)) {
878 struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
879 struct blkcg_gq, blkcg_node);
880 struct request_queue *q = blkg->q;
882 if (spin_trylock(q->queue_lock)) {
884 spin_unlock(q->queue_lock);
886 spin_unlock_irq(&blkcg->lock);
888 spin_lock_irq(&blkcg->lock);
892 spin_unlock_irq(&blkcg->lock);
894 wb_blkcg_offline(blkcg);
897 static void blkcg_css_free(struct cgroup_subsys_state *css)
899 struct blkcg *blkcg = css_to_blkcg(css);
902 mutex_lock(&blkcg_pol_mutex);
904 list_del(&blkcg->all_blkcgs_node);
906 for (i = 0; i < BLKCG_MAX_POLS; i++)
908 blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
910 mutex_unlock(&blkcg_pol_mutex);
915 static struct cgroup_subsys_state *
916 blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
919 struct cgroup_subsys_state *ret;
922 mutex_lock(&blkcg_pol_mutex);
927 blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
929 ret = ERR_PTR(-ENOMEM);
934 for (i = 0; i < BLKCG_MAX_POLS ; i++) {
935 struct blkcg_policy *pol = blkcg_policy[i];
936 struct blkcg_policy_data *cpd;
939 * If the policy hasn't been attached yet, wait for it
940 * to be attached before doing anything else. Otherwise,
941 * check if the policy requires any specific per-cgroup
942 * data: if it does, allocate and initialize it.
944 if (!pol || !pol->cpd_alloc_fn)
947 cpd = pol->cpd_alloc_fn(GFP_KERNEL);
949 ret = ERR_PTR(-ENOMEM);
955 if (pol->cpd_init_fn)
956 pol->cpd_init_fn(cpd);
959 spin_lock_init(&blkcg->lock);
960 INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT);
961 INIT_HLIST_HEAD(&blkcg->blkg_list);
962 #ifdef CONFIG_CGROUP_WRITEBACK
963 INIT_LIST_HEAD(&blkcg->cgwb_list);
965 list_add_tail(&blkcg->all_blkcgs_node, &all_blkcgs);
967 mutex_unlock(&blkcg_pol_mutex);
971 for (i--; i >= 0; i--)
973 blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
976 mutex_unlock(&blkcg_pol_mutex);
981 * blkcg_init_queue - initialize blkcg part of request queue
982 * @q: request_queue to initialize
984 * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
985 * part of new request_queue @q.
988 * 0 on success, -errno on failure.
990 int blkcg_init_queue(struct request_queue *q)
992 struct blkcg_gq *new_blkg, *blkg;
996 new_blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
1000 preloaded = !radix_tree_preload(GFP_KERNEL);
1003 * Make sure the root blkg exists and count the existing blkgs. As
1004 * @q is bypassing at this point, blkg_lookup_create() can't be
1005 * used. Open code insertion.
1008 spin_lock_irq(q->queue_lock);
1009 blkg = blkg_create(&blkcg_root, q, new_blkg);
1010 spin_unlock_irq(q->queue_lock);
1014 radix_tree_preload_end();
1017 blkg_free(new_blkg);
1018 return PTR_ERR(blkg);
1021 q->root_blkg = blkg;
1022 q->root_rl.blkg = blkg;
1024 ret = blk_throtl_init(q);
1026 spin_lock_irq(q->queue_lock);
1027 blkg_destroy_all(q);
1028 spin_unlock_irq(q->queue_lock);
1034 * blkcg_drain_queue - drain blkcg part of request_queue
1035 * @q: request_queue to drain
1037 * Called from blk_drain_queue(). Responsible for draining blkcg part.
1039 void blkcg_drain_queue(struct request_queue *q)
1041 lockdep_assert_held(q->queue_lock);
1044 * @q could be exiting and already have destroyed all blkgs as
1045 * indicated by NULL root_blkg. If so, don't confuse policies.
1050 blk_throtl_drain(q);
1054 * blkcg_exit_queue - exit and release blkcg part of request_queue
1055 * @q: request_queue being released
1057 * Called from blk_release_queue(). Responsible for exiting blkcg part.
1059 void blkcg_exit_queue(struct request_queue *q)
1061 spin_lock_irq(q->queue_lock);
1062 blkg_destroy_all(q);
1063 spin_unlock_irq(q->queue_lock);
1069 * We cannot support shared io contexts, as we have no mean to support
1070 * two tasks with the same ioc in two different groups without major rework
1071 * of the main cic data structures. For now we allow a task to change
1072 * its cgroup only if it's the only owner of its ioc.
1074 static int blkcg_can_attach(struct cgroup_subsys_state *css,
1075 struct cgroup_taskset *tset)
1077 struct task_struct *task;
1078 struct io_context *ioc;
1081 /* task_lock() is needed to avoid races with exit_io_context() */
1082 cgroup_taskset_for_each(task, tset) {
1084 ioc = task->io_context;
1085 if (ioc && atomic_read(&ioc->nr_tasks) > 1)
1094 struct cgroup_subsys blkio_cgrp_subsys = {
1095 .css_alloc = blkcg_css_alloc,
1096 .css_offline = blkcg_css_offline,
1097 .css_free = blkcg_css_free,
1098 .can_attach = blkcg_can_attach,
1099 .legacy_cftypes = blkcg_files,
1102 * This ensures that, if available, memcg is automatically enabled
1103 * together on the default hierarchy so that the owner cgroup can
1104 * be retrieved from writeback pages.
1106 .depends_on = 1 << memory_cgrp_id,
1109 EXPORT_SYMBOL_GPL(blkio_cgrp_subsys);
1112 * blkcg_activate_policy - activate a blkcg policy on a request_queue
1113 * @q: request_queue of interest
1114 * @pol: blkcg policy to activate
1116 * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through
1117 * bypass mode to populate its blkgs with policy_data for @pol.
1119 * Activation happens with @q bypassed, so nobody would be accessing blkgs
1120 * from IO path. Update of each blkg is protected by both queue and blkcg
1121 * locks so that holding either lock and testing blkcg_policy_enabled() is
1122 * always enough for dereferencing policy data.
1124 * The caller is responsible for synchronizing [de]activations and policy
1125 * [un]registerations. Returns 0 on success, -errno on failure.
1127 int blkcg_activate_policy(struct request_queue *q,
1128 const struct blkcg_policy *pol)
1130 struct blkg_policy_data *pd_prealloc = NULL;
1131 struct blkcg_gq *blkg;
1134 if (blkcg_policy_enabled(q, pol))
1137 blk_queue_bypass_start(q);
1140 pd_prealloc = pol->pd_alloc_fn(GFP_KERNEL, q->node);
1143 goto out_bypass_end;
1147 spin_lock_irq(q->queue_lock);
1149 list_for_each_entry(blkg, &q->blkg_list, q_node) {
1150 struct blkg_policy_data *pd;
1152 if (blkg->pd[pol->plid])
1155 pd = pol->pd_alloc_fn(GFP_NOWAIT, q->node);
1157 swap(pd, pd_prealloc);
1159 spin_unlock_irq(q->queue_lock);
1163 blkg->pd[pol->plid] = pd;
1165 pd->plid = pol->plid;
1166 if (pol->pd_init_fn)
1167 pol->pd_init_fn(pd);
1170 __set_bit(pol->plid, q->blkcg_pols);
1173 spin_unlock_irq(q->queue_lock);
1175 blk_queue_bypass_end(q);
1177 pol->pd_free_fn(pd_prealloc);
1180 EXPORT_SYMBOL_GPL(blkcg_activate_policy);
1183 * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
1184 * @q: request_queue of interest
1185 * @pol: blkcg policy to deactivate
1187 * Deactivate @pol on @q. Follows the same synchronization rules as
1188 * blkcg_activate_policy().
1190 void blkcg_deactivate_policy(struct request_queue *q,
1191 const struct blkcg_policy *pol)
1193 struct blkcg_gq *blkg;
1195 if (!blkcg_policy_enabled(q, pol))
1198 blk_queue_bypass_start(q);
1199 spin_lock_irq(q->queue_lock);
1201 __clear_bit(pol->plid, q->blkcg_pols);
1203 list_for_each_entry(blkg, &q->blkg_list, q_node) {
1204 /* grab blkcg lock too while removing @pd from @blkg */
1205 spin_lock(&blkg->blkcg->lock);
1207 if (blkg->pd[pol->plid]) {
1208 if (pol->pd_offline_fn)
1209 pol->pd_offline_fn(blkg->pd[pol->plid]);
1210 pol->pd_free_fn(blkg->pd[pol->plid]);
1211 blkg->pd[pol->plid] = NULL;
1214 spin_unlock(&blkg->blkcg->lock);
1217 spin_unlock_irq(q->queue_lock);
1218 blk_queue_bypass_end(q);
1220 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
1223 * blkcg_policy_register - register a blkcg policy
1224 * @pol: blkcg policy to register
1226 * Register @pol with blkcg core. Might sleep and @pol may be modified on
1227 * successful registration. Returns 0 on success and -errno on failure.
1229 int blkcg_policy_register(struct blkcg_policy *pol)
1231 struct blkcg *blkcg;
1234 mutex_lock(&blkcg_pol_register_mutex);
1235 mutex_lock(&blkcg_pol_mutex);
1237 /* find an empty slot */
1239 for (i = 0; i < BLKCG_MAX_POLS; i++)
1240 if (!blkcg_policy[i])
1242 if (i >= BLKCG_MAX_POLS)
1247 blkcg_policy[pol->plid] = pol;
1249 /* allocate and install cpd's */
1250 if (pol->cpd_alloc_fn) {
1251 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1252 struct blkcg_policy_data *cpd;
1254 cpd = pol->cpd_alloc_fn(GFP_KERNEL);
1256 mutex_unlock(&blkcg_pol_mutex);
1260 blkcg->cpd[pol->plid] = cpd;
1262 cpd->plid = pol->plid;
1263 pol->cpd_init_fn(cpd);
1267 mutex_unlock(&blkcg_pol_mutex);
1269 /* everything is in place, add intf files for the new policy */
1271 WARN_ON(cgroup_add_legacy_cftypes(&blkio_cgrp_subsys,
1273 mutex_unlock(&blkcg_pol_register_mutex);
1277 if (pol->cpd_alloc_fn) {
1278 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1279 if (blkcg->cpd[pol->plid]) {
1280 pol->cpd_free_fn(blkcg->cpd[pol->plid]);
1281 blkcg->cpd[pol->plid] = NULL;
1285 blkcg_policy[pol->plid] = NULL;
1287 mutex_unlock(&blkcg_pol_mutex);
1288 mutex_unlock(&blkcg_pol_register_mutex);
1291 EXPORT_SYMBOL_GPL(blkcg_policy_register);
1294 * blkcg_policy_unregister - unregister a blkcg policy
1295 * @pol: blkcg policy to unregister
1297 * Undo blkcg_policy_register(@pol). Might sleep.
1299 void blkcg_policy_unregister(struct blkcg_policy *pol)
1301 struct blkcg *blkcg;
1303 mutex_lock(&blkcg_pol_register_mutex);
1305 if (WARN_ON(blkcg_policy[pol->plid] != pol))
1308 /* kill the intf files first */
1310 cgroup_rm_cftypes(pol->cftypes);
1312 /* remove cpds and unregister */
1313 mutex_lock(&blkcg_pol_mutex);
1315 if (pol->cpd_alloc_fn) {
1316 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1317 if (blkcg->cpd[pol->plid]) {
1318 pol->cpd_free_fn(blkcg->cpd[pol->plid]);
1319 blkcg->cpd[pol->plid] = NULL;
1323 blkcg_policy[pol->plid] = NULL;
1325 mutex_unlock(&blkcg_pol_mutex);
1327 mutex_unlock(&blkcg_pol_register_mutex);
1329 EXPORT_SYMBOL_GPL(blkcg_policy_unregister);