perf machine: Add nr_cpus_avail()
[linux/fpc-iii.git] / block / blk-cgroup.c
blobeb85cb87c40f46f54b96cd06ae078600e8e8cac4
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 * 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/sched/signal.h>
21 #include <linux/err.h>
22 #include <linux/blkdev.h>
23 #include <linux/backing-dev.h>
24 #include <linux/slab.h>
25 #include <linux/genhd.h>
26 #include <linux/delay.h>
27 #include <linux/atomic.h>
28 #include <linux/ctype.h>
29 #include <linux/blk-cgroup.h>
30 #include "blk.h"
32 #define MAX_KEY_LEN 100
35 * blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation.
36 * blkcg_pol_register_mutex nests outside of it and synchronizes entire
37 * policy [un]register operations including cgroup file additions /
38 * removals. Putting cgroup file registration outside blkcg_pol_mutex
39 * allows grabbing it from cgroup callbacks.
41 static DEFINE_MUTEX(blkcg_pol_register_mutex);
42 static DEFINE_MUTEX(blkcg_pol_mutex);
44 struct blkcg blkcg_root;
45 EXPORT_SYMBOL_GPL(blkcg_root);
47 struct cgroup_subsys_state * const blkcg_root_css = &blkcg_root.css;
49 static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];
51 static LIST_HEAD(all_blkcgs); /* protected by blkcg_pol_mutex */
53 static bool blkcg_policy_enabled(struct request_queue *q,
54 const struct blkcg_policy *pol)
56 return pol && test_bit(pol->plid, q->blkcg_pols);
59 /**
60 * blkg_free - free a blkg
61 * @blkg: blkg to free
63 * Free @blkg which may be partially allocated.
65 static void blkg_free(struct blkcg_gq *blkg)
67 int i;
69 if (!blkg)
70 return;
72 for (i = 0; i < BLKCG_MAX_POLS; i++)
73 if (blkg->pd[i])
74 blkcg_policy[i]->pd_free_fn(blkg->pd[i]);
76 if (blkg->blkcg != &blkcg_root)
77 blk_exit_rl(blkg->q, &blkg->rl);
79 blkg_rwstat_exit(&blkg->stat_ios);
80 blkg_rwstat_exit(&blkg->stat_bytes);
81 kfree(blkg);
84 /**
85 * blkg_alloc - allocate a blkg
86 * @blkcg: block cgroup the new blkg is associated with
87 * @q: request_queue the new blkg is associated with
88 * @gfp_mask: allocation mask to use
90 * Allocate a new blkg assocating @blkcg and @q.
92 static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
93 gfp_t gfp_mask)
95 struct blkcg_gq *blkg;
96 int i;
98 /* alloc and init base part */
99 blkg = kzalloc_node(sizeof(*blkg), gfp_mask, q->node);
100 if (!blkg)
101 return NULL;
103 if (blkg_rwstat_init(&blkg->stat_bytes, gfp_mask) ||
104 blkg_rwstat_init(&blkg->stat_ios, gfp_mask))
105 goto err_free;
107 blkg->q = q;
108 INIT_LIST_HEAD(&blkg->q_node);
109 blkg->blkcg = blkcg;
110 atomic_set(&blkg->refcnt, 1);
112 /* root blkg uses @q->root_rl, init rl only for !root blkgs */
113 if (blkcg != &blkcg_root) {
114 if (blk_init_rl(&blkg->rl, q, gfp_mask))
115 goto err_free;
116 blkg->rl.blkg = blkg;
119 for (i = 0; i < BLKCG_MAX_POLS; i++) {
120 struct blkcg_policy *pol = blkcg_policy[i];
121 struct blkg_policy_data *pd;
123 if (!blkcg_policy_enabled(q, pol))
124 continue;
126 /* alloc per-policy data and attach it to blkg */
127 pd = pol->pd_alloc_fn(gfp_mask, q->node);
128 if (!pd)
129 goto err_free;
131 blkg->pd[i] = pd;
132 pd->blkg = blkg;
133 pd->plid = i;
136 return blkg;
138 err_free:
139 blkg_free(blkg);
140 return NULL;
143 struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
144 struct request_queue *q, bool update_hint)
146 struct blkcg_gq *blkg;
149 * Hint didn't match. Look up from the radix tree. Note that the
150 * hint can only be updated under queue_lock as otherwise @blkg
151 * could have already been removed from blkg_tree. The caller is
152 * responsible for grabbing queue_lock if @update_hint.
154 blkg = radix_tree_lookup(&blkcg->blkg_tree, q->id);
155 if (blkg && blkg->q == q) {
156 if (update_hint) {
157 lockdep_assert_held(q->queue_lock);
158 rcu_assign_pointer(blkcg->blkg_hint, blkg);
160 return blkg;
163 return NULL;
165 EXPORT_SYMBOL_GPL(blkg_lookup_slowpath);
168 * If @new_blkg is %NULL, this function tries to allocate a new one as
169 * necessary using %GFP_NOWAIT. @new_blkg is always consumed on return.
171 static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
172 struct request_queue *q,
173 struct blkcg_gq *new_blkg)
175 struct blkcg_gq *blkg;
176 struct bdi_writeback_congested *wb_congested;
177 int i, ret;
179 WARN_ON_ONCE(!rcu_read_lock_held());
180 lockdep_assert_held(q->queue_lock);
182 /* blkg holds a reference to blkcg */
183 if (!css_tryget_online(&blkcg->css)) {
184 ret = -ENODEV;
185 goto err_free_blkg;
188 wb_congested = wb_congested_get_create(q->backing_dev_info,
189 blkcg->css.id,
190 GFP_NOWAIT | __GFP_NOWARN);
191 if (!wb_congested) {
192 ret = -ENOMEM;
193 goto err_put_css;
196 /* allocate */
197 if (!new_blkg) {
198 new_blkg = blkg_alloc(blkcg, q, GFP_NOWAIT | __GFP_NOWARN);
199 if (unlikely(!new_blkg)) {
200 ret = -ENOMEM;
201 goto err_put_congested;
204 blkg = new_blkg;
205 blkg->wb_congested = wb_congested;
207 /* link parent */
208 if (blkcg_parent(blkcg)) {
209 blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false);
210 if (WARN_ON_ONCE(!blkg->parent)) {
211 ret = -ENODEV;
212 goto err_put_congested;
214 blkg_get(blkg->parent);
217 /* invoke per-policy init */
218 for (i = 0; i < BLKCG_MAX_POLS; i++) {
219 struct blkcg_policy *pol = blkcg_policy[i];
221 if (blkg->pd[i] && pol->pd_init_fn)
222 pol->pd_init_fn(blkg->pd[i]);
225 /* insert */
226 spin_lock(&blkcg->lock);
227 ret = radix_tree_insert(&blkcg->blkg_tree, q->id, blkg);
228 if (likely(!ret)) {
229 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
230 list_add(&blkg->q_node, &q->blkg_list);
232 for (i = 0; i < BLKCG_MAX_POLS; i++) {
233 struct blkcg_policy *pol = blkcg_policy[i];
235 if (blkg->pd[i] && pol->pd_online_fn)
236 pol->pd_online_fn(blkg->pd[i]);
239 blkg->online = true;
240 spin_unlock(&blkcg->lock);
242 if (!ret)
243 return blkg;
245 /* @blkg failed fully initialized, use the usual release path */
246 blkg_put(blkg);
247 return ERR_PTR(ret);
249 err_put_congested:
250 wb_congested_put(wb_congested);
251 err_put_css:
252 css_put(&blkcg->css);
253 err_free_blkg:
254 blkg_free(new_blkg);
255 return ERR_PTR(ret);
259 * blkg_lookup_create - lookup blkg, try to create one if not there
260 * @blkcg: blkcg of interest
261 * @q: request_queue of interest
263 * Lookup blkg for the @blkcg - @q pair. If it doesn't exist, try to
264 * create one. blkg creation is performed recursively from blkcg_root such
265 * that all non-root blkg's have access to the parent blkg. This function
266 * should be called under RCU read lock and @q->queue_lock.
268 * Returns pointer to the looked up or created blkg on success, ERR_PTR()
269 * value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not
270 * dead and bypassing, returns ERR_PTR(-EBUSY).
272 struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
273 struct request_queue *q)
275 struct blkcg_gq *blkg;
277 WARN_ON_ONCE(!rcu_read_lock_held());
278 lockdep_assert_held(q->queue_lock);
281 * This could be the first entry point of blkcg implementation and
282 * we shouldn't allow anything to go through for a bypassing queue.
284 if (unlikely(blk_queue_bypass(q)))
285 return ERR_PTR(blk_queue_dying(q) ? -ENODEV : -EBUSY);
287 blkg = __blkg_lookup(blkcg, q, true);
288 if (blkg)
289 return blkg;
292 * Create blkgs walking down from blkcg_root to @blkcg, so that all
293 * non-root blkgs have access to their parents.
295 while (true) {
296 struct blkcg *pos = blkcg;
297 struct blkcg *parent = blkcg_parent(blkcg);
299 while (parent && !__blkg_lookup(parent, q, false)) {
300 pos = parent;
301 parent = blkcg_parent(parent);
304 blkg = blkg_create(pos, q, NULL);
305 if (pos == blkcg || IS_ERR(blkg))
306 return blkg;
310 static void blkg_pd_offline(struct blkcg_gq *blkg)
312 int i;
314 lockdep_assert_held(blkg->q->queue_lock);
315 lockdep_assert_held(&blkg->blkcg->lock);
317 for (i = 0; i < BLKCG_MAX_POLS; i++) {
318 struct blkcg_policy *pol = blkcg_policy[i];
320 if (blkg->pd[i] && !blkg->pd[i]->offline &&
321 pol->pd_offline_fn) {
322 pol->pd_offline_fn(blkg->pd[i]);
323 blkg->pd[i]->offline = true;
328 static void blkg_destroy(struct blkcg_gq *blkg)
330 struct blkcg *blkcg = blkg->blkcg;
331 struct blkcg_gq *parent = blkg->parent;
333 lockdep_assert_held(blkg->q->queue_lock);
334 lockdep_assert_held(&blkcg->lock);
336 /* Something wrong if we are trying to remove same group twice */
337 WARN_ON_ONCE(list_empty(&blkg->q_node));
338 WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
340 if (parent) {
341 blkg_rwstat_add_aux(&parent->stat_bytes, &blkg->stat_bytes);
342 blkg_rwstat_add_aux(&parent->stat_ios, &blkg->stat_ios);
345 blkg->online = false;
347 radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
348 list_del_init(&blkg->q_node);
349 hlist_del_init_rcu(&blkg->blkcg_node);
352 * Both setting lookup hint to and clearing it from @blkg are done
353 * under queue_lock. If it's not pointing to @blkg now, it never
354 * will. Hint assignment itself can race safely.
356 if (rcu_access_pointer(blkcg->blkg_hint) == blkg)
357 rcu_assign_pointer(blkcg->blkg_hint, NULL);
360 * Put the reference taken at the time of creation so that when all
361 * queues are gone, group can be destroyed.
363 blkg_put(blkg);
367 * blkg_destroy_all - destroy all blkgs associated with a request_queue
368 * @q: request_queue of interest
370 * Destroy all blkgs associated with @q.
372 static void blkg_destroy_all(struct request_queue *q)
374 struct blkcg_gq *blkg, *n;
376 lockdep_assert_held(q->queue_lock);
378 list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
379 struct blkcg *blkcg = blkg->blkcg;
381 spin_lock(&blkcg->lock);
382 blkg_pd_offline(blkg);
383 blkg_destroy(blkg);
384 spin_unlock(&blkcg->lock);
387 q->root_blkg = NULL;
388 q->root_rl.blkg = NULL;
392 * A group is RCU protected, but having an rcu lock does not mean that one
393 * can access all the fields of blkg and assume these are valid. For
394 * example, don't try to follow throtl_data and request queue links.
396 * Having a reference to blkg under an rcu allows accesses to only values
397 * local to groups like group stats and group rate limits.
399 void __blkg_release_rcu(struct rcu_head *rcu_head)
401 struct blkcg_gq *blkg = container_of(rcu_head, struct blkcg_gq, rcu_head);
403 /* release the blkcg and parent blkg refs this blkg has been holding */
404 css_put(&blkg->blkcg->css);
405 if (blkg->parent)
406 blkg_put(blkg->parent);
408 wb_congested_put(blkg->wb_congested);
410 blkg_free(blkg);
412 EXPORT_SYMBOL_GPL(__blkg_release_rcu);
415 * The next function used by blk_queue_for_each_rl(). It's a bit tricky
416 * because the root blkg uses @q->root_rl instead of its own rl.
418 struct request_list *__blk_queue_next_rl(struct request_list *rl,
419 struct request_queue *q)
421 struct list_head *ent;
422 struct blkcg_gq *blkg;
425 * Determine the current blkg list_head. The first entry is
426 * root_rl which is off @q->blkg_list and mapped to the head.
428 if (rl == &q->root_rl) {
429 ent = &q->blkg_list;
430 /* There are no more block groups, hence no request lists */
431 if (list_empty(ent))
432 return NULL;
433 } else {
434 blkg = container_of(rl, struct blkcg_gq, rl);
435 ent = &blkg->q_node;
438 /* walk to the next list_head, skip root blkcg */
439 ent = ent->next;
440 if (ent == &q->root_blkg->q_node)
441 ent = ent->next;
442 if (ent == &q->blkg_list)
443 return NULL;
445 blkg = container_of(ent, struct blkcg_gq, q_node);
446 return &blkg->rl;
449 static int blkcg_reset_stats(struct cgroup_subsys_state *css,
450 struct cftype *cftype, u64 val)
452 struct blkcg *blkcg = css_to_blkcg(css);
453 struct blkcg_gq *blkg;
454 int i;
456 mutex_lock(&blkcg_pol_mutex);
457 spin_lock_irq(&blkcg->lock);
460 * Note that stat reset is racy - it doesn't synchronize against
461 * stat updates. This is a debug feature which shouldn't exist
462 * anyway. If you get hit by a race, retry.
464 hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
465 blkg_rwstat_reset(&blkg->stat_bytes);
466 blkg_rwstat_reset(&blkg->stat_ios);
468 for (i = 0; i < BLKCG_MAX_POLS; i++) {
469 struct blkcg_policy *pol = blkcg_policy[i];
471 if (blkg->pd[i] && pol->pd_reset_stats_fn)
472 pol->pd_reset_stats_fn(blkg->pd[i]);
476 spin_unlock_irq(&blkcg->lock);
477 mutex_unlock(&blkcg_pol_mutex);
478 return 0;
481 const char *blkg_dev_name(struct blkcg_gq *blkg)
483 /* some drivers (floppy) instantiate a queue w/o disk registered */
484 if (blkg->q->backing_dev_info->dev)
485 return dev_name(blkg->q->backing_dev_info->dev);
486 return NULL;
488 EXPORT_SYMBOL_GPL(blkg_dev_name);
491 * blkcg_print_blkgs - helper for printing per-blkg data
492 * @sf: seq_file to print to
493 * @blkcg: blkcg of interest
494 * @prfill: fill function to print out a blkg
495 * @pol: policy in question
496 * @data: data to be passed to @prfill
497 * @show_total: to print out sum of prfill return values or not
499 * This function invokes @prfill on each blkg of @blkcg if pd for the
500 * policy specified by @pol exists. @prfill is invoked with @sf, the
501 * policy data and @data and the matching queue lock held. If @show_total
502 * is %true, the sum of the return values from @prfill is printed with
503 * "Total" label at the end.
505 * This is to be used to construct print functions for
506 * cftype->read_seq_string method.
508 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
509 u64 (*prfill)(struct seq_file *,
510 struct blkg_policy_data *, int),
511 const struct blkcg_policy *pol, int data,
512 bool show_total)
514 struct blkcg_gq *blkg;
515 u64 total = 0;
517 rcu_read_lock();
518 hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
519 spin_lock_irq(blkg->q->queue_lock);
520 if (blkcg_policy_enabled(blkg->q, pol))
521 total += prfill(sf, blkg->pd[pol->plid], data);
522 spin_unlock_irq(blkg->q->queue_lock);
524 rcu_read_unlock();
526 if (show_total)
527 seq_printf(sf, "Total %llu\n", (unsigned long long)total);
529 EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
532 * __blkg_prfill_u64 - prfill helper for a single u64 value
533 * @sf: seq_file to print to
534 * @pd: policy private data of interest
535 * @v: value to print
537 * Print @v to @sf for the device assocaited with @pd.
539 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
541 const char *dname = blkg_dev_name(pd->blkg);
543 if (!dname)
544 return 0;
546 seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
547 return v;
549 EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
552 * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
553 * @sf: seq_file to print to
554 * @pd: policy private data of interest
555 * @rwstat: rwstat to print
557 * Print @rwstat to @sf for the device assocaited with @pd.
559 u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
560 const struct blkg_rwstat *rwstat)
562 static const char *rwstr[] = {
563 [BLKG_RWSTAT_READ] = "Read",
564 [BLKG_RWSTAT_WRITE] = "Write",
565 [BLKG_RWSTAT_SYNC] = "Sync",
566 [BLKG_RWSTAT_ASYNC] = "Async",
568 const char *dname = blkg_dev_name(pd->blkg);
569 u64 v;
570 int i;
572 if (!dname)
573 return 0;
575 for (i = 0; i < BLKG_RWSTAT_NR; i++)
576 seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
577 (unsigned long long)atomic64_read(&rwstat->aux_cnt[i]));
579 v = atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_READ]) +
580 atomic64_read(&rwstat->aux_cnt[BLKG_RWSTAT_WRITE]);
581 seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
582 return v;
584 EXPORT_SYMBOL_GPL(__blkg_prfill_rwstat);
587 * blkg_prfill_stat - prfill callback for blkg_stat
588 * @sf: seq_file to print to
589 * @pd: policy private data of interest
590 * @off: offset to the blkg_stat in @pd
592 * prfill callback for printing a blkg_stat.
594 u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off)
596 return __blkg_prfill_u64(sf, pd, blkg_stat_read((void *)pd + off));
598 EXPORT_SYMBOL_GPL(blkg_prfill_stat);
601 * blkg_prfill_rwstat - prfill callback for blkg_rwstat
602 * @sf: seq_file to print to
603 * @pd: policy private data of interest
604 * @off: offset to the blkg_rwstat in @pd
606 * prfill callback for printing a blkg_rwstat.
608 u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
609 int off)
611 struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd + off);
613 return __blkg_prfill_rwstat(sf, pd, &rwstat);
615 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
617 static u64 blkg_prfill_rwstat_field(struct seq_file *sf,
618 struct blkg_policy_data *pd, int off)
620 struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd->blkg + off);
622 return __blkg_prfill_rwstat(sf, pd, &rwstat);
626 * blkg_print_stat_bytes - seq_show callback for blkg->stat_bytes
627 * @sf: seq_file to print to
628 * @v: unused
630 * To be used as cftype->seq_show to print blkg->stat_bytes.
631 * cftype->private must be set to the blkcg_policy.
633 int blkg_print_stat_bytes(struct seq_file *sf, void *v)
635 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
636 blkg_prfill_rwstat_field, (void *)seq_cft(sf)->private,
637 offsetof(struct blkcg_gq, stat_bytes), true);
638 return 0;
640 EXPORT_SYMBOL_GPL(blkg_print_stat_bytes);
643 * blkg_print_stat_bytes - seq_show callback for blkg->stat_ios
644 * @sf: seq_file to print to
645 * @v: unused
647 * To be used as cftype->seq_show to print blkg->stat_ios. cftype->private
648 * must be set to the blkcg_policy.
650 int blkg_print_stat_ios(struct seq_file *sf, void *v)
652 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
653 blkg_prfill_rwstat_field, (void *)seq_cft(sf)->private,
654 offsetof(struct blkcg_gq, stat_ios), true);
655 return 0;
657 EXPORT_SYMBOL_GPL(blkg_print_stat_ios);
659 static u64 blkg_prfill_rwstat_field_recursive(struct seq_file *sf,
660 struct blkg_policy_data *pd,
661 int off)
663 struct blkg_rwstat rwstat = blkg_rwstat_recursive_sum(pd->blkg,
664 NULL, off);
665 return __blkg_prfill_rwstat(sf, pd, &rwstat);
669 * blkg_print_stat_bytes_recursive - recursive version of blkg_print_stat_bytes
670 * @sf: seq_file to print to
671 * @v: unused
673 int blkg_print_stat_bytes_recursive(struct seq_file *sf, void *v)
675 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
676 blkg_prfill_rwstat_field_recursive,
677 (void *)seq_cft(sf)->private,
678 offsetof(struct blkcg_gq, stat_bytes), true);
679 return 0;
681 EXPORT_SYMBOL_GPL(blkg_print_stat_bytes_recursive);
684 * blkg_print_stat_ios_recursive - recursive version of blkg_print_stat_ios
685 * @sf: seq_file to print to
686 * @v: unused
688 int blkg_print_stat_ios_recursive(struct seq_file *sf, void *v)
690 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
691 blkg_prfill_rwstat_field_recursive,
692 (void *)seq_cft(sf)->private,
693 offsetof(struct blkcg_gq, stat_ios), true);
694 return 0;
696 EXPORT_SYMBOL_GPL(blkg_print_stat_ios_recursive);
699 * blkg_stat_recursive_sum - collect hierarchical blkg_stat
700 * @blkg: blkg of interest
701 * @pol: blkcg_policy which contains the blkg_stat
702 * @off: offset to the blkg_stat in blkg_policy_data or @blkg
704 * Collect the blkg_stat specified by @blkg, @pol and @off and all its
705 * online descendants and their aux counts. The caller must be holding the
706 * queue lock for online tests.
708 * If @pol is NULL, blkg_stat is at @off bytes into @blkg; otherwise, it is
709 * at @off bytes into @blkg's blkg_policy_data of the policy.
711 u64 blkg_stat_recursive_sum(struct blkcg_gq *blkg,
712 struct blkcg_policy *pol, int off)
714 struct blkcg_gq *pos_blkg;
715 struct cgroup_subsys_state *pos_css;
716 u64 sum = 0;
718 lockdep_assert_held(blkg->q->queue_lock);
720 rcu_read_lock();
721 blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
722 struct blkg_stat *stat;
724 if (!pos_blkg->online)
725 continue;
727 if (pol)
728 stat = (void *)blkg_to_pd(pos_blkg, pol) + off;
729 else
730 stat = (void *)blkg + off;
732 sum += blkg_stat_read(stat) + atomic64_read(&stat->aux_cnt);
734 rcu_read_unlock();
736 return sum;
738 EXPORT_SYMBOL_GPL(blkg_stat_recursive_sum);
741 * blkg_rwstat_recursive_sum - collect hierarchical blkg_rwstat
742 * @blkg: blkg of interest
743 * @pol: blkcg_policy which contains the blkg_rwstat
744 * @off: offset to the blkg_rwstat in blkg_policy_data or @blkg
746 * Collect the blkg_rwstat specified by @blkg, @pol and @off and all its
747 * online descendants and their aux counts. The caller must be holding the
748 * queue lock for online tests.
750 * If @pol is NULL, blkg_rwstat is at @off bytes into @blkg; otherwise, it
751 * is at @off bytes into @blkg's blkg_policy_data of the policy.
753 struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkcg_gq *blkg,
754 struct blkcg_policy *pol, int off)
756 struct blkcg_gq *pos_blkg;
757 struct cgroup_subsys_state *pos_css;
758 struct blkg_rwstat sum = { };
759 int i;
761 lockdep_assert_held(blkg->q->queue_lock);
763 rcu_read_lock();
764 blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
765 struct blkg_rwstat *rwstat;
767 if (!pos_blkg->online)
768 continue;
770 if (pol)
771 rwstat = (void *)blkg_to_pd(pos_blkg, pol) + off;
772 else
773 rwstat = (void *)pos_blkg + off;
775 for (i = 0; i < BLKG_RWSTAT_NR; i++)
776 atomic64_add(atomic64_read(&rwstat->aux_cnt[i]) +
777 percpu_counter_sum_positive(&rwstat->cpu_cnt[i]),
778 &sum.aux_cnt[i]);
780 rcu_read_unlock();
782 return sum;
784 EXPORT_SYMBOL_GPL(blkg_rwstat_recursive_sum);
786 /* Performs queue bypass and policy enabled checks then looks up blkg. */
787 static struct blkcg_gq *blkg_lookup_check(struct blkcg *blkcg,
788 const struct blkcg_policy *pol,
789 struct request_queue *q)
791 WARN_ON_ONCE(!rcu_read_lock_held());
792 lockdep_assert_held(q->queue_lock);
794 if (!blkcg_policy_enabled(q, pol))
795 return ERR_PTR(-EOPNOTSUPP);
798 * This could be the first entry point of blkcg implementation and
799 * we shouldn't allow anything to go through for a bypassing queue.
801 if (unlikely(blk_queue_bypass(q)))
802 return ERR_PTR(blk_queue_dying(q) ? -ENODEV : -EBUSY);
804 return __blkg_lookup(blkcg, q, true /* update_hint */);
808 * blkg_conf_prep - parse and prepare for per-blkg config update
809 * @blkcg: target block cgroup
810 * @pol: target policy
811 * @input: input string
812 * @ctx: blkg_conf_ctx to be filled
814 * Parse per-blkg config update from @input and initialize @ctx with the
815 * result. @ctx->blkg points to the blkg to be updated and @ctx->body the
816 * part of @input following MAJ:MIN. This function returns with RCU read
817 * lock and queue lock held and must be paired with blkg_conf_finish().
819 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
820 char *input, struct blkg_conf_ctx *ctx)
821 __acquires(rcu) __acquires(disk->queue->queue_lock)
823 struct gendisk *disk;
824 struct request_queue *q;
825 struct blkcg_gq *blkg;
826 unsigned int major, minor;
827 int key_len, part, ret;
828 char *body;
830 if (sscanf(input, "%u:%u%n", &major, &minor, &key_len) != 2)
831 return -EINVAL;
833 body = input + key_len;
834 if (!isspace(*body))
835 return -EINVAL;
836 body = skip_spaces(body);
838 disk = get_gendisk(MKDEV(major, minor), &part);
839 if (!disk)
840 return -ENODEV;
841 if (part) {
842 ret = -ENODEV;
843 goto fail;
846 q = disk->queue;
848 rcu_read_lock();
849 spin_lock_irq(q->queue_lock);
851 blkg = blkg_lookup_check(blkcg, pol, q);
852 if (IS_ERR(blkg)) {
853 ret = PTR_ERR(blkg);
854 goto fail_unlock;
857 if (blkg)
858 goto success;
861 * Create blkgs walking down from blkcg_root to @blkcg, so that all
862 * non-root blkgs have access to their parents.
864 while (true) {
865 struct blkcg *pos = blkcg;
866 struct blkcg *parent;
867 struct blkcg_gq *new_blkg;
869 parent = blkcg_parent(blkcg);
870 while (parent && !__blkg_lookup(parent, q, false)) {
871 pos = parent;
872 parent = blkcg_parent(parent);
875 /* Drop locks to do new blkg allocation with GFP_KERNEL. */
876 spin_unlock_irq(q->queue_lock);
877 rcu_read_unlock();
879 new_blkg = blkg_alloc(pos, q, GFP_KERNEL);
880 if (unlikely(!new_blkg)) {
881 ret = -ENOMEM;
882 goto fail;
885 rcu_read_lock();
886 spin_lock_irq(q->queue_lock);
888 blkg = blkg_lookup_check(pos, pol, q);
889 if (IS_ERR(blkg)) {
890 ret = PTR_ERR(blkg);
891 goto fail_unlock;
894 if (blkg) {
895 blkg_free(new_blkg);
896 } else {
897 blkg = blkg_create(pos, q, new_blkg);
898 if (unlikely(IS_ERR(blkg))) {
899 ret = PTR_ERR(blkg);
900 goto fail_unlock;
904 if (pos == blkcg)
905 goto success;
907 success:
908 ctx->disk = disk;
909 ctx->blkg = blkg;
910 ctx->body = body;
911 return 0;
913 fail_unlock:
914 spin_unlock_irq(q->queue_lock);
915 rcu_read_unlock();
916 fail:
917 put_disk_and_module(disk);
919 * If queue was bypassing, we should retry. Do so after a
920 * short msleep(). It isn't strictly necessary but queue
921 * can be bypassing for some time and it's always nice to
922 * avoid busy looping.
924 if (ret == -EBUSY) {
925 msleep(10);
926 ret = restart_syscall();
928 return ret;
930 EXPORT_SYMBOL_GPL(blkg_conf_prep);
933 * blkg_conf_finish - finish up per-blkg config update
934 * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
936 * Finish up after per-blkg config update. This function must be paired
937 * with blkg_conf_prep().
939 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
940 __releases(ctx->disk->queue->queue_lock) __releases(rcu)
942 spin_unlock_irq(ctx->disk->queue->queue_lock);
943 rcu_read_unlock();
944 put_disk_and_module(ctx->disk);
946 EXPORT_SYMBOL_GPL(blkg_conf_finish);
948 static int blkcg_print_stat(struct seq_file *sf, void *v)
950 struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
951 struct blkcg_gq *blkg;
953 rcu_read_lock();
955 hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
956 const char *dname;
957 struct blkg_rwstat rwstat;
958 u64 rbytes, wbytes, rios, wios;
960 dname = blkg_dev_name(blkg);
961 if (!dname)
962 continue;
964 spin_lock_irq(blkg->q->queue_lock);
966 rwstat = blkg_rwstat_recursive_sum(blkg, NULL,
967 offsetof(struct blkcg_gq, stat_bytes));
968 rbytes = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_READ]);
969 wbytes = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_WRITE]);
971 rwstat = blkg_rwstat_recursive_sum(blkg, NULL,
972 offsetof(struct blkcg_gq, stat_ios));
973 rios = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_READ]);
974 wios = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_WRITE]);
976 spin_unlock_irq(blkg->q->queue_lock);
978 if (rbytes || wbytes || rios || wios)
979 seq_printf(sf, "%s rbytes=%llu wbytes=%llu rios=%llu wios=%llu\n",
980 dname, rbytes, wbytes, rios, wios);
983 rcu_read_unlock();
984 return 0;
987 static struct cftype blkcg_files[] = {
989 .name = "stat",
990 .flags = CFTYPE_NOT_ON_ROOT,
991 .seq_show = blkcg_print_stat,
993 { } /* terminate */
996 static struct cftype blkcg_legacy_files[] = {
998 .name = "reset_stats",
999 .write_u64 = blkcg_reset_stats,
1001 { } /* terminate */
1005 * blkcg_css_offline - cgroup css_offline callback
1006 * @css: css of interest
1008 * This function is called when @css is about to go away and responsible
1009 * for offlining all blkgs pd and killing all wbs associated with @css.
1010 * blkgs pd offline should be done while holding both q and blkcg locks.
1011 * As blkcg lock is nested inside q lock, this function performs reverse
1012 * double lock dancing.
1014 * This is the blkcg counterpart of ioc_release_fn().
1016 static void blkcg_css_offline(struct cgroup_subsys_state *css)
1018 struct blkcg *blkcg = css_to_blkcg(css);
1019 struct blkcg_gq *blkg;
1021 spin_lock_irq(&blkcg->lock);
1023 hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
1024 struct request_queue *q = blkg->q;
1026 if (spin_trylock(q->queue_lock)) {
1027 blkg_pd_offline(blkg);
1028 spin_unlock(q->queue_lock);
1029 } else {
1030 spin_unlock_irq(&blkcg->lock);
1031 cpu_relax();
1032 spin_lock_irq(&blkcg->lock);
1036 spin_unlock_irq(&blkcg->lock);
1038 wb_blkcg_offline(blkcg);
1042 * blkcg_destroy_all_blkgs - destroy all blkgs associated with a blkcg
1043 * @blkcg: blkcg of interest
1045 * This function is called when blkcg css is about to free and responsible for
1046 * destroying all blkgs associated with @blkcg.
1047 * blkgs should be removed while holding both q and blkcg locks. As blkcg lock
1048 * is nested inside q lock, this function performs reverse double lock dancing.
1050 static void blkcg_destroy_all_blkgs(struct blkcg *blkcg)
1052 spin_lock_irq(&blkcg->lock);
1053 while (!hlist_empty(&blkcg->blkg_list)) {
1054 struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
1055 struct blkcg_gq,
1056 blkcg_node);
1057 struct request_queue *q = blkg->q;
1059 if (spin_trylock(q->queue_lock)) {
1060 blkg_destroy(blkg);
1061 spin_unlock(q->queue_lock);
1062 } else {
1063 spin_unlock_irq(&blkcg->lock);
1064 cpu_relax();
1065 spin_lock_irq(&blkcg->lock);
1068 spin_unlock_irq(&blkcg->lock);
1071 static void blkcg_css_free(struct cgroup_subsys_state *css)
1073 struct blkcg *blkcg = css_to_blkcg(css);
1074 int i;
1076 blkcg_destroy_all_blkgs(blkcg);
1078 mutex_lock(&blkcg_pol_mutex);
1080 list_del(&blkcg->all_blkcgs_node);
1082 for (i = 0; i < BLKCG_MAX_POLS; i++)
1083 if (blkcg->cpd[i])
1084 blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
1086 mutex_unlock(&blkcg_pol_mutex);
1088 kfree(blkcg);
1091 static struct cgroup_subsys_state *
1092 blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
1094 struct blkcg *blkcg;
1095 struct cgroup_subsys_state *ret;
1096 int i;
1098 mutex_lock(&blkcg_pol_mutex);
1100 if (!parent_css) {
1101 blkcg = &blkcg_root;
1102 } else {
1103 blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
1104 if (!blkcg) {
1105 ret = ERR_PTR(-ENOMEM);
1106 goto unlock;
1110 for (i = 0; i < BLKCG_MAX_POLS ; i++) {
1111 struct blkcg_policy *pol = blkcg_policy[i];
1112 struct blkcg_policy_data *cpd;
1115 * If the policy hasn't been attached yet, wait for it
1116 * to be attached before doing anything else. Otherwise,
1117 * check if the policy requires any specific per-cgroup
1118 * data: if it does, allocate and initialize it.
1120 if (!pol || !pol->cpd_alloc_fn)
1121 continue;
1123 cpd = pol->cpd_alloc_fn(GFP_KERNEL);
1124 if (!cpd) {
1125 ret = ERR_PTR(-ENOMEM);
1126 goto free_pd_blkcg;
1128 blkcg->cpd[i] = cpd;
1129 cpd->blkcg = blkcg;
1130 cpd->plid = i;
1131 if (pol->cpd_init_fn)
1132 pol->cpd_init_fn(cpd);
1135 spin_lock_init(&blkcg->lock);
1136 INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT | __GFP_NOWARN);
1137 INIT_HLIST_HEAD(&blkcg->blkg_list);
1138 #ifdef CONFIG_CGROUP_WRITEBACK
1139 INIT_LIST_HEAD(&blkcg->cgwb_list);
1140 #endif
1141 list_add_tail(&blkcg->all_blkcgs_node, &all_blkcgs);
1143 mutex_unlock(&blkcg_pol_mutex);
1144 return &blkcg->css;
1146 free_pd_blkcg:
1147 for (i--; i >= 0; i--)
1148 if (blkcg->cpd[i])
1149 blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
1151 if (blkcg != &blkcg_root)
1152 kfree(blkcg);
1153 unlock:
1154 mutex_unlock(&blkcg_pol_mutex);
1155 return ret;
1159 * blkcg_init_queue - initialize blkcg part of request queue
1160 * @q: request_queue to initialize
1162 * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
1163 * part of new request_queue @q.
1165 * RETURNS:
1166 * 0 on success, -errno on failure.
1168 int blkcg_init_queue(struct request_queue *q)
1170 struct blkcg_gq *new_blkg, *blkg;
1171 bool preloaded;
1172 int ret;
1174 new_blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
1175 if (!new_blkg)
1176 return -ENOMEM;
1178 preloaded = !radix_tree_preload(GFP_KERNEL);
1180 /* Make sure the root blkg exists. */
1181 rcu_read_lock();
1182 spin_lock_irq(q->queue_lock);
1183 blkg = blkg_create(&blkcg_root, q, new_blkg);
1184 if (IS_ERR(blkg))
1185 goto err_unlock;
1186 q->root_blkg = blkg;
1187 q->root_rl.blkg = blkg;
1188 spin_unlock_irq(q->queue_lock);
1189 rcu_read_unlock();
1191 if (preloaded)
1192 radix_tree_preload_end();
1194 ret = blk_throtl_init(q);
1195 if (ret) {
1196 spin_lock_irq(q->queue_lock);
1197 blkg_destroy_all(q);
1198 spin_unlock_irq(q->queue_lock);
1200 return ret;
1202 err_unlock:
1203 spin_unlock_irq(q->queue_lock);
1204 rcu_read_unlock();
1205 if (preloaded)
1206 radix_tree_preload_end();
1207 return PTR_ERR(blkg);
1211 * blkcg_drain_queue - drain blkcg part of request_queue
1212 * @q: request_queue to drain
1214 * Called from blk_drain_queue(). Responsible for draining blkcg part.
1216 void blkcg_drain_queue(struct request_queue *q)
1218 lockdep_assert_held(q->queue_lock);
1221 * @q could be exiting and already have destroyed all blkgs as
1222 * indicated by NULL root_blkg. If so, don't confuse policies.
1224 if (!q->root_blkg)
1225 return;
1227 blk_throtl_drain(q);
1231 * blkcg_exit_queue - exit and release blkcg part of request_queue
1232 * @q: request_queue being released
1234 * Called from blk_release_queue(). Responsible for exiting blkcg part.
1236 void blkcg_exit_queue(struct request_queue *q)
1238 spin_lock_irq(q->queue_lock);
1239 blkg_destroy_all(q);
1240 spin_unlock_irq(q->queue_lock);
1242 blk_throtl_exit(q);
1246 * We cannot support shared io contexts, as we have no mean to support
1247 * two tasks with the same ioc in two different groups without major rework
1248 * of the main cic data structures. For now we allow a task to change
1249 * its cgroup only if it's the only owner of its ioc.
1251 static int blkcg_can_attach(struct cgroup_taskset *tset)
1253 struct task_struct *task;
1254 struct cgroup_subsys_state *dst_css;
1255 struct io_context *ioc;
1256 int ret = 0;
1258 /* task_lock() is needed to avoid races with exit_io_context() */
1259 cgroup_taskset_for_each(task, dst_css, tset) {
1260 task_lock(task);
1261 ioc = task->io_context;
1262 if (ioc && atomic_read(&ioc->nr_tasks) > 1)
1263 ret = -EINVAL;
1264 task_unlock(task);
1265 if (ret)
1266 break;
1268 return ret;
1271 static void blkcg_bind(struct cgroup_subsys_state *root_css)
1273 int i;
1275 mutex_lock(&blkcg_pol_mutex);
1277 for (i = 0; i < BLKCG_MAX_POLS; i++) {
1278 struct blkcg_policy *pol = blkcg_policy[i];
1279 struct blkcg *blkcg;
1281 if (!pol || !pol->cpd_bind_fn)
1282 continue;
1284 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node)
1285 if (blkcg->cpd[pol->plid])
1286 pol->cpd_bind_fn(blkcg->cpd[pol->plid]);
1288 mutex_unlock(&blkcg_pol_mutex);
1291 struct cgroup_subsys io_cgrp_subsys = {
1292 .css_alloc = blkcg_css_alloc,
1293 .css_offline = blkcg_css_offline,
1294 .css_free = blkcg_css_free,
1295 .can_attach = blkcg_can_attach,
1296 .bind = blkcg_bind,
1297 .dfl_cftypes = blkcg_files,
1298 .legacy_cftypes = blkcg_legacy_files,
1299 .legacy_name = "blkio",
1300 #ifdef CONFIG_MEMCG
1302 * This ensures that, if available, memcg is automatically enabled
1303 * together on the default hierarchy so that the owner cgroup can
1304 * be retrieved from writeback pages.
1306 .depends_on = 1 << memory_cgrp_id,
1307 #endif
1309 EXPORT_SYMBOL_GPL(io_cgrp_subsys);
1312 * blkcg_activate_policy - activate a blkcg policy on a request_queue
1313 * @q: request_queue of interest
1314 * @pol: blkcg policy to activate
1316 * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through
1317 * bypass mode to populate its blkgs with policy_data for @pol.
1319 * Activation happens with @q bypassed, so nobody would be accessing blkgs
1320 * from IO path. Update of each blkg is protected by both queue and blkcg
1321 * locks so that holding either lock and testing blkcg_policy_enabled() is
1322 * always enough for dereferencing policy data.
1324 * The caller is responsible for synchronizing [de]activations and policy
1325 * [un]registerations. Returns 0 on success, -errno on failure.
1327 int blkcg_activate_policy(struct request_queue *q,
1328 const struct blkcg_policy *pol)
1330 struct blkg_policy_data *pd_prealloc = NULL;
1331 struct blkcg_gq *blkg;
1332 int ret;
1334 if (blkcg_policy_enabled(q, pol))
1335 return 0;
1337 if (q->mq_ops)
1338 blk_mq_freeze_queue(q);
1339 else
1340 blk_queue_bypass_start(q);
1341 pd_prealloc:
1342 if (!pd_prealloc) {
1343 pd_prealloc = pol->pd_alloc_fn(GFP_KERNEL, q->node);
1344 if (!pd_prealloc) {
1345 ret = -ENOMEM;
1346 goto out_bypass_end;
1350 spin_lock_irq(q->queue_lock);
1352 list_for_each_entry(blkg, &q->blkg_list, q_node) {
1353 struct blkg_policy_data *pd;
1355 if (blkg->pd[pol->plid])
1356 continue;
1358 pd = pol->pd_alloc_fn(GFP_NOWAIT | __GFP_NOWARN, q->node);
1359 if (!pd)
1360 swap(pd, pd_prealloc);
1361 if (!pd) {
1362 spin_unlock_irq(q->queue_lock);
1363 goto pd_prealloc;
1366 blkg->pd[pol->plid] = pd;
1367 pd->blkg = blkg;
1368 pd->plid = pol->plid;
1369 if (pol->pd_init_fn)
1370 pol->pd_init_fn(pd);
1373 __set_bit(pol->plid, q->blkcg_pols);
1374 ret = 0;
1376 spin_unlock_irq(q->queue_lock);
1377 out_bypass_end:
1378 if (q->mq_ops)
1379 blk_mq_unfreeze_queue(q);
1380 else
1381 blk_queue_bypass_end(q);
1382 if (pd_prealloc)
1383 pol->pd_free_fn(pd_prealloc);
1384 return ret;
1386 EXPORT_SYMBOL_GPL(blkcg_activate_policy);
1389 * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
1390 * @q: request_queue of interest
1391 * @pol: blkcg policy to deactivate
1393 * Deactivate @pol on @q. Follows the same synchronization rules as
1394 * blkcg_activate_policy().
1396 void blkcg_deactivate_policy(struct request_queue *q,
1397 const struct blkcg_policy *pol)
1399 struct blkcg_gq *blkg;
1401 if (!blkcg_policy_enabled(q, pol))
1402 return;
1404 if (q->mq_ops)
1405 blk_mq_freeze_queue(q);
1406 else
1407 blk_queue_bypass_start(q);
1409 spin_lock_irq(q->queue_lock);
1411 __clear_bit(pol->plid, q->blkcg_pols);
1413 list_for_each_entry(blkg, &q->blkg_list, q_node) {
1414 if (blkg->pd[pol->plid]) {
1415 if (!blkg->pd[pol->plid]->offline &&
1416 pol->pd_offline_fn) {
1417 pol->pd_offline_fn(blkg->pd[pol->plid]);
1418 blkg->pd[pol->plid]->offline = true;
1420 pol->pd_free_fn(blkg->pd[pol->plid]);
1421 blkg->pd[pol->plid] = NULL;
1425 spin_unlock_irq(q->queue_lock);
1427 if (q->mq_ops)
1428 blk_mq_unfreeze_queue(q);
1429 else
1430 blk_queue_bypass_end(q);
1432 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
1435 * blkcg_policy_register - register a blkcg policy
1436 * @pol: blkcg policy to register
1438 * Register @pol with blkcg core. Might sleep and @pol may be modified on
1439 * successful registration. Returns 0 on success and -errno on failure.
1441 int blkcg_policy_register(struct blkcg_policy *pol)
1443 struct blkcg *blkcg;
1444 int i, ret;
1446 mutex_lock(&blkcg_pol_register_mutex);
1447 mutex_lock(&blkcg_pol_mutex);
1449 /* find an empty slot */
1450 ret = -ENOSPC;
1451 for (i = 0; i < BLKCG_MAX_POLS; i++)
1452 if (!blkcg_policy[i])
1453 break;
1454 if (i >= BLKCG_MAX_POLS)
1455 goto err_unlock;
1457 /* Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs */
1458 if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) ||
1459 (!pol->pd_alloc_fn ^ !pol->pd_free_fn))
1460 goto err_unlock;
1462 /* register @pol */
1463 pol->plid = i;
1464 blkcg_policy[pol->plid] = pol;
1466 /* allocate and install cpd's */
1467 if (pol->cpd_alloc_fn) {
1468 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1469 struct blkcg_policy_data *cpd;
1471 cpd = pol->cpd_alloc_fn(GFP_KERNEL);
1472 if (!cpd)
1473 goto err_free_cpds;
1475 blkcg->cpd[pol->plid] = cpd;
1476 cpd->blkcg = blkcg;
1477 cpd->plid = pol->plid;
1478 pol->cpd_init_fn(cpd);
1482 mutex_unlock(&blkcg_pol_mutex);
1484 /* everything is in place, add intf files for the new policy */
1485 if (pol->dfl_cftypes)
1486 WARN_ON(cgroup_add_dfl_cftypes(&io_cgrp_subsys,
1487 pol->dfl_cftypes));
1488 if (pol->legacy_cftypes)
1489 WARN_ON(cgroup_add_legacy_cftypes(&io_cgrp_subsys,
1490 pol->legacy_cftypes));
1491 mutex_unlock(&blkcg_pol_register_mutex);
1492 return 0;
1494 err_free_cpds:
1495 if (pol->cpd_free_fn) {
1496 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1497 if (blkcg->cpd[pol->plid]) {
1498 pol->cpd_free_fn(blkcg->cpd[pol->plid]);
1499 blkcg->cpd[pol->plid] = NULL;
1503 blkcg_policy[pol->plid] = NULL;
1504 err_unlock:
1505 mutex_unlock(&blkcg_pol_mutex);
1506 mutex_unlock(&blkcg_pol_register_mutex);
1507 return ret;
1509 EXPORT_SYMBOL_GPL(blkcg_policy_register);
1512 * blkcg_policy_unregister - unregister a blkcg policy
1513 * @pol: blkcg policy to unregister
1515 * Undo blkcg_policy_register(@pol). Might sleep.
1517 void blkcg_policy_unregister(struct blkcg_policy *pol)
1519 struct blkcg *blkcg;
1521 mutex_lock(&blkcg_pol_register_mutex);
1523 if (WARN_ON(blkcg_policy[pol->plid] != pol))
1524 goto out_unlock;
1526 /* kill the intf files first */
1527 if (pol->dfl_cftypes)
1528 cgroup_rm_cftypes(pol->dfl_cftypes);
1529 if (pol->legacy_cftypes)
1530 cgroup_rm_cftypes(pol->legacy_cftypes);
1532 /* remove cpds and unregister */
1533 mutex_lock(&blkcg_pol_mutex);
1535 if (pol->cpd_free_fn) {
1536 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1537 if (blkcg->cpd[pol->plid]) {
1538 pol->cpd_free_fn(blkcg->cpd[pol->plid]);
1539 blkcg->cpd[pol->plid] = NULL;
1543 blkcg_policy[pol->plid] = NULL;
1545 mutex_unlock(&blkcg_pol_mutex);
1546 out_unlock:
1547 mutex_unlock(&blkcg_pol_register_mutex);
1549 EXPORT_SYMBOL_GPL(blkcg_policy_unregister);