1 // SPDX-License-Identifier: GPL-2.0
3 * Common Block IO controller cgroup interface
5 * Based on ideas and code from CFQ, CFS and BFQ:
6 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
8 * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
9 * Paolo Valente <paolo.valente@unimore.it>
11 * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
12 * Nauman Rafique <nauman@google.com>
14 * For policy-specific per-blkcg data:
15 * Copyright (C) 2015 Paolo Valente <paolo.valente@unimore.it>
16 * Arianna Avanzini <avanzini.arianna@gmail.com>
18 #include <linux/ioprio.h>
19 #include <linux/kdev_t.h>
20 #include <linux/module.h>
21 #include <linux/sched/signal.h>
22 #include <linux/err.h>
23 #include <linux/blkdev.h>
24 #include <linux/backing-dev.h>
25 #include <linux/slab.h>
26 #include <linux/delay.h>
27 #include <linux/atomic.h>
28 #include <linux/ctype.h>
29 #include <linux/resume_user_mode.h>
30 #include <linux/psi.h>
31 #include <linux/part_stat.h>
33 #include "blk-cgroup.h"
34 #include "blk-ioprio.h"
35 #include "blk-throttle.h"
38 * blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation.
39 * blkcg_pol_register_mutex nests outside of it and synchronizes entire
40 * policy [un]register operations including cgroup file additions /
41 * removals. Putting cgroup file registration outside blkcg_pol_mutex
42 * allows grabbing it from cgroup callbacks.
44 static DEFINE_MUTEX(blkcg_pol_register_mutex
);
45 static DEFINE_MUTEX(blkcg_pol_mutex
);
47 struct blkcg blkcg_root
;
48 EXPORT_SYMBOL_GPL(blkcg_root
);
50 struct cgroup_subsys_state
* const blkcg_root_css
= &blkcg_root
.css
;
51 EXPORT_SYMBOL_GPL(blkcg_root_css
);
53 static struct blkcg_policy
*blkcg_policy
[BLKCG_MAX_POLS
];
55 static LIST_HEAD(all_blkcgs
); /* protected by blkcg_pol_mutex */
57 bool blkcg_debug_stats
= false;
58 static struct workqueue_struct
*blkcg_punt_bio_wq
;
60 #define BLKG_DESTROY_BATCH_SIZE 64
62 static bool blkcg_policy_enabled(struct request_queue
*q
,
63 const struct blkcg_policy
*pol
)
65 return pol
&& test_bit(pol
->plid
, q
->blkcg_pols
);
69 * blkg_free - free a blkg
72 * Free @blkg which may be partially allocated.
74 static void blkg_free(struct blkcg_gq
*blkg
)
81 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++)
83 blkcg_policy
[i
]->pd_free_fn(blkg
->pd
[i
]);
86 blk_put_queue(blkg
->q
);
87 free_percpu(blkg
->iostat_cpu
);
88 percpu_ref_exit(&blkg
->refcnt
);
92 static void __blkg_release(struct rcu_head
*rcu
)
94 struct blkcg_gq
*blkg
= container_of(rcu
, struct blkcg_gq
, rcu_head
);
96 WARN_ON(!bio_list_empty(&blkg
->async_bios
));
98 /* release the blkcg and parent blkg refs this blkg has been holding */
99 css_put(&blkg
->blkcg
->css
);
101 blkg_put(blkg
->parent
);
106 * A group is RCU protected, but having an rcu lock does not mean that one
107 * can access all the fields of blkg and assume these are valid. For
108 * example, don't try to follow throtl_data and request queue links.
110 * Having a reference to blkg under an rcu allows accesses to only values
111 * local to groups like group stats and group rate limits.
113 static void blkg_release(struct percpu_ref
*ref
)
115 struct blkcg_gq
*blkg
= container_of(ref
, struct blkcg_gq
, refcnt
);
117 call_rcu(&blkg
->rcu_head
, __blkg_release
);
120 static void blkg_async_bio_workfn(struct work_struct
*work
)
122 struct blkcg_gq
*blkg
= container_of(work
, struct blkcg_gq
,
124 struct bio_list bios
= BIO_EMPTY_LIST
;
126 struct blk_plug plug
;
127 bool need_plug
= false;
129 /* as long as there are pending bios, @blkg can't go away */
130 spin_lock_bh(&blkg
->async_bio_lock
);
131 bio_list_merge(&bios
, &blkg
->async_bios
);
132 bio_list_init(&blkg
->async_bios
);
133 spin_unlock_bh(&blkg
->async_bio_lock
);
135 /* start plug only when bio_list contains at least 2 bios */
136 if (bios
.head
&& bios
.head
->bi_next
) {
138 blk_start_plug(&plug
);
140 while ((bio
= bio_list_pop(&bios
)))
143 blk_finish_plug(&plug
);
147 * blkg_alloc - allocate a blkg
148 * @blkcg: block cgroup the new blkg is associated with
149 * @q: request_queue the new blkg is associated with
150 * @gfp_mask: allocation mask to use
152 * Allocate a new blkg assocating @blkcg and @q.
154 static struct blkcg_gq
*blkg_alloc(struct blkcg
*blkcg
, struct request_queue
*q
,
157 struct blkcg_gq
*blkg
;
160 /* alloc and init base part */
161 blkg
= kzalloc_node(sizeof(*blkg
), gfp_mask
, q
->node
);
165 if (percpu_ref_init(&blkg
->refcnt
, blkg_release
, 0, gfp_mask
))
168 blkg
->iostat_cpu
= alloc_percpu_gfp(struct blkg_iostat_set
, gfp_mask
);
169 if (!blkg
->iostat_cpu
)
172 if (!blk_get_queue(q
))
176 INIT_LIST_HEAD(&blkg
->q_node
);
177 spin_lock_init(&blkg
->async_bio_lock
);
178 bio_list_init(&blkg
->async_bios
);
179 INIT_WORK(&blkg
->async_bio_work
, blkg_async_bio_workfn
);
182 u64_stats_init(&blkg
->iostat
.sync
);
183 for_each_possible_cpu(cpu
)
184 u64_stats_init(&per_cpu_ptr(blkg
->iostat_cpu
, cpu
)->sync
);
186 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
187 struct blkcg_policy
*pol
= blkcg_policy
[i
];
188 struct blkg_policy_data
*pd
;
190 if (!blkcg_policy_enabled(q
, pol
))
193 /* alloc per-policy data and attach it to blkg */
194 pd
= pol
->pd_alloc_fn(gfp_mask
, q
, blkcg
);
210 struct blkcg_gq
*blkg_lookup_slowpath(struct blkcg
*blkcg
,
211 struct request_queue
*q
, bool update_hint
)
213 struct blkcg_gq
*blkg
;
216 * Hint didn't match. Look up from the radix tree. Note that the
217 * hint can only be updated under queue_lock as otherwise @blkg
218 * could have already been removed from blkg_tree. The caller is
219 * responsible for grabbing queue_lock if @update_hint.
221 blkg
= radix_tree_lookup(&blkcg
->blkg_tree
, q
->id
);
222 if (blkg
&& blkg
->q
== q
) {
224 lockdep_assert_held(&q
->queue_lock
);
225 rcu_assign_pointer(blkcg
->blkg_hint
, blkg
);
232 EXPORT_SYMBOL_GPL(blkg_lookup_slowpath
);
235 * If @new_blkg is %NULL, this function tries to allocate a new one as
236 * necessary using %GFP_NOWAIT. @new_blkg is always consumed on return.
238 static struct blkcg_gq
*blkg_create(struct blkcg
*blkcg
,
239 struct request_queue
*q
,
240 struct blkcg_gq
*new_blkg
)
242 struct blkcg_gq
*blkg
;
245 WARN_ON_ONCE(!rcu_read_lock_held());
246 lockdep_assert_held(&q
->queue_lock
);
248 /* request_queue is dying, do not create/recreate a blkg */
249 if (blk_queue_dying(q
)) {
254 /* blkg holds a reference to blkcg */
255 if (!css_tryget_online(&blkcg
->css
)) {
262 new_blkg
= blkg_alloc(blkcg
, q
, GFP_NOWAIT
| __GFP_NOWARN
);
263 if (unlikely(!new_blkg
)) {
271 if (blkcg_parent(blkcg
)) {
272 blkg
->parent
= __blkg_lookup(blkcg_parent(blkcg
), q
, false);
273 if (WARN_ON_ONCE(!blkg
->parent
)) {
277 blkg_get(blkg
->parent
);
280 /* invoke per-policy init */
281 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
282 struct blkcg_policy
*pol
= blkcg_policy
[i
];
284 if (blkg
->pd
[i
] && pol
->pd_init_fn
)
285 pol
->pd_init_fn(blkg
->pd
[i
]);
289 spin_lock(&blkcg
->lock
);
290 ret
= radix_tree_insert(&blkcg
->blkg_tree
, q
->id
, blkg
);
292 hlist_add_head_rcu(&blkg
->blkcg_node
, &blkcg
->blkg_list
);
293 list_add(&blkg
->q_node
, &q
->blkg_list
);
295 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
296 struct blkcg_policy
*pol
= blkcg_policy
[i
];
298 if (blkg
->pd
[i
] && pol
->pd_online_fn
)
299 pol
->pd_online_fn(blkg
->pd
[i
]);
303 spin_unlock(&blkcg
->lock
);
308 /* @blkg failed fully initialized, use the usual release path */
313 css_put(&blkcg
->css
);
320 * blkg_lookup_create - lookup blkg, try to create one if not there
321 * @blkcg: blkcg of interest
322 * @q: request_queue of interest
324 * Lookup blkg for the @blkcg - @q pair. If it doesn't exist, try to
325 * create one. blkg creation is performed recursively from blkcg_root such
326 * that all non-root blkg's have access to the parent blkg. This function
327 * should be called under RCU read lock and takes @q->queue_lock.
329 * Returns the blkg or the closest blkg if blkg_create() fails as it walks
332 static struct blkcg_gq
*blkg_lookup_create(struct blkcg
*blkcg
,
333 struct request_queue
*q
)
335 struct blkcg_gq
*blkg
;
338 WARN_ON_ONCE(!rcu_read_lock_held());
340 blkg
= blkg_lookup(blkcg
, q
);
344 spin_lock_irqsave(&q
->queue_lock
, flags
);
345 blkg
= __blkg_lookup(blkcg
, q
, true);
350 * Create blkgs walking down from blkcg_root to @blkcg, so that all
351 * non-root blkgs have access to their parents. Returns the closest
352 * blkg to the intended blkg should blkg_create() fail.
355 struct blkcg
*pos
= blkcg
;
356 struct blkcg
*parent
= blkcg_parent(blkcg
);
357 struct blkcg_gq
*ret_blkg
= q
->root_blkg
;
360 blkg
= __blkg_lookup(parent
, q
, false);
362 /* remember closest blkg */
367 parent
= blkcg_parent(parent
);
370 blkg
= blkg_create(pos
, q
, NULL
);
380 spin_unlock_irqrestore(&q
->queue_lock
, flags
);
384 static void blkg_destroy(struct blkcg_gq
*blkg
)
386 struct blkcg
*blkcg
= blkg
->blkcg
;
389 lockdep_assert_held(&blkg
->q
->queue_lock
);
390 lockdep_assert_held(&blkcg
->lock
);
392 /* Something wrong if we are trying to remove same group twice */
393 WARN_ON_ONCE(list_empty(&blkg
->q_node
));
394 WARN_ON_ONCE(hlist_unhashed(&blkg
->blkcg_node
));
396 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
397 struct blkcg_policy
*pol
= blkcg_policy
[i
];
399 if (blkg
->pd
[i
] && pol
->pd_offline_fn
)
400 pol
->pd_offline_fn(blkg
->pd
[i
]);
403 blkg
->online
= false;
405 radix_tree_delete(&blkcg
->blkg_tree
, blkg
->q
->id
);
406 list_del_init(&blkg
->q_node
);
407 hlist_del_init_rcu(&blkg
->blkcg_node
);
410 * Both setting lookup hint to and clearing it from @blkg are done
411 * under queue_lock. If it's not pointing to @blkg now, it never
412 * will. Hint assignment itself can race safely.
414 if (rcu_access_pointer(blkcg
->blkg_hint
) == blkg
)
415 rcu_assign_pointer(blkcg
->blkg_hint
, NULL
);
418 * Put the reference taken at the time of creation so that when all
419 * queues are gone, group can be destroyed.
421 percpu_ref_kill(&blkg
->refcnt
);
425 * blkg_destroy_all - destroy all blkgs associated with a request_queue
426 * @q: request_queue of interest
428 * Destroy all blkgs associated with @q.
430 static void blkg_destroy_all(struct request_queue
*q
)
432 struct blkcg_gq
*blkg
, *n
;
433 int count
= BLKG_DESTROY_BATCH_SIZE
;
436 spin_lock_irq(&q
->queue_lock
);
437 list_for_each_entry_safe(blkg
, n
, &q
->blkg_list
, q_node
) {
438 struct blkcg
*blkcg
= blkg
->blkcg
;
440 spin_lock(&blkcg
->lock
);
442 spin_unlock(&blkcg
->lock
);
445 * in order to avoid holding the spin lock for too long, release
446 * it when a batch of blkgs are destroyed.
449 count
= BLKG_DESTROY_BATCH_SIZE
;
450 spin_unlock_irq(&q
->queue_lock
);
457 spin_unlock_irq(&q
->queue_lock
);
460 static int blkcg_reset_stats(struct cgroup_subsys_state
*css
,
461 struct cftype
*cftype
, u64 val
)
463 struct blkcg
*blkcg
= css_to_blkcg(css
);
464 struct blkcg_gq
*blkg
;
467 mutex_lock(&blkcg_pol_mutex
);
468 spin_lock_irq(&blkcg
->lock
);
471 * Note that stat reset is racy - it doesn't synchronize against
472 * stat updates. This is a debug feature which shouldn't exist
473 * anyway. If you get hit by a race, retry.
475 hlist_for_each_entry(blkg
, &blkcg
->blkg_list
, blkcg_node
) {
476 for_each_possible_cpu(cpu
) {
477 struct blkg_iostat_set
*bis
=
478 per_cpu_ptr(blkg
->iostat_cpu
, cpu
);
479 memset(bis
, 0, sizeof(*bis
));
481 memset(&blkg
->iostat
, 0, sizeof(blkg
->iostat
));
483 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
484 struct blkcg_policy
*pol
= blkcg_policy
[i
];
486 if (blkg
->pd
[i
] && pol
->pd_reset_stats_fn
)
487 pol
->pd_reset_stats_fn(blkg
->pd
[i
]);
491 spin_unlock_irq(&blkcg
->lock
);
492 mutex_unlock(&blkcg_pol_mutex
);
496 const char *blkg_dev_name(struct blkcg_gq
*blkg
)
498 if (!blkg
->q
->disk
|| !blkg
->q
->disk
->bdi
->dev
)
500 return bdi_dev_name(blkg
->q
->disk
->bdi
);
504 * blkcg_print_blkgs - helper for printing per-blkg data
505 * @sf: seq_file to print to
506 * @blkcg: blkcg of interest
507 * @prfill: fill function to print out a blkg
508 * @pol: policy in question
509 * @data: data to be passed to @prfill
510 * @show_total: to print out sum of prfill return values or not
512 * This function invokes @prfill on each blkg of @blkcg if pd for the
513 * policy specified by @pol exists. @prfill is invoked with @sf, the
514 * policy data and @data and the matching queue lock held. If @show_total
515 * is %true, the sum of the return values from @prfill is printed with
516 * "Total" label at the end.
518 * This is to be used to construct print functions for
519 * cftype->read_seq_string method.
521 void blkcg_print_blkgs(struct seq_file
*sf
, struct blkcg
*blkcg
,
522 u64 (*prfill
)(struct seq_file
*,
523 struct blkg_policy_data
*, int),
524 const struct blkcg_policy
*pol
, int data
,
527 struct blkcg_gq
*blkg
;
531 hlist_for_each_entry_rcu(blkg
, &blkcg
->blkg_list
, blkcg_node
) {
532 spin_lock_irq(&blkg
->q
->queue_lock
);
533 if (blkcg_policy_enabled(blkg
->q
, pol
))
534 total
+= prfill(sf
, blkg
->pd
[pol
->plid
], data
);
535 spin_unlock_irq(&blkg
->q
->queue_lock
);
540 seq_printf(sf
, "Total %llu\n", (unsigned long long)total
);
542 EXPORT_SYMBOL_GPL(blkcg_print_blkgs
);
545 * __blkg_prfill_u64 - prfill helper for a single u64 value
546 * @sf: seq_file to print to
547 * @pd: policy private data of interest
550 * Print @v to @sf for the device assocaited with @pd.
552 u64
__blkg_prfill_u64(struct seq_file
*sf
, struct blkg_policy_data
*pd
, u64 v
)
554 const char *dname
= blkg_dev_name(pd
->blkg
);
559 seq_printf(sf
, "%s %llu\n", dname
, (unsigned long long)v
);
562 EXPORT_SYMBOL_GPL(__blkg_prfill_u64
);
564 /* Performs queue bypass and policy enabled checks then looks up blkg. */
565 static struct blkcg_gq
*blkg_lookup_check(struct blkcg
*blkcg
,
566 const struct blkcg_policy
*pol
,
567 struct request_queue
*q
)
569 WARN_ON_ONCE(!rcu_read_lock_held());
570 lockdep_assert_held(&q
->queue_lock
);
572 if (!blkcg_policy_enabled(q
, pol
))
573 return ERR_PTR(-EOPNOTSUPP
);
574 return __blkg_lookup(blkcg
, q
, true /* update_hint */);
578 * blkcg_conf_open_bdev - parse and open bdev for per-blkg config update
579 * @inputp: input string pointer
581 * Parse the device node prefix part, MAJ:MIN, of per-blkg config update
582 * from @input and get and return the matching bdev. *@inputp is
583 * updated to point past the device node prefix. Returns an ERR_PTR()
586 * Use this function iff blkg_conf_prep() can't be used for some reason.
588 struct block_device
*blkcg_conf_open_bdev(char **inputp
)
590 char *input
= *inputp
;
591 unsigned int major
, minor
;
592 struct block_device
*bdev
;
595 if (sscanf(input
, "%u:%u%n", &major
, &minor
, &key_len
) != 2)
596 return ERR_PTR(-EINVAL
);
599 if (!isspace(*input
))
600 return ERR_PTR(-EINVAL
);
601 input
= skip_spaces(input
);
603 bdev
= blkdev_get_no_open(MKDEV(major
, minor
));
605 return ERR_PTR(-ENODEV
);
606 if (bdev_is_partition(bdev
)) {
607 blkdev_put_no_open(bdev
);
608 return ERR_PTR(-ENODEV
);
616 * blkg_conf_prep - parse and prepare for per-blkg config update
617 * @blkcg: target block cgroup
618 * @pol: target policy
619 * @input: input string
620 * @ctx: blkg_conf_ctx to be filled
622 * Parse per-blkg config update from @input and initialize @ctx with the
623 * result. @ctx->blkg points to the blkg to be updated and @ctx->body the
624 * part of @input following MAJ:MIN. This function returns with RCU read
625 * lock and queue lock held and must be paired with blkg_conf_finish().
627 int blkg_conf_prep(struct blkcg
*blkcg
, const struct blkcg_policy
*pol
,
628 char *input
, struct blkg_conf_ctx
*ctx
)
629 __acquires(rcu
) __acquires(&bdev
->bd_queue
->queue_lock
)
631 struct block_device
*bdev
;
632 struct request_queue
*q
;
633 struct blkcg_gq
*blkg
;
636 bdev
= blkcg_conf_open_bdev(&input
);
638 return PTR_ERR(bdev
);
640 q
= bdev_get_queue(bdev
);
643 * blkcg_deactivate_policy() requires queue to be frozen, we can grab
644 * q_usage_counter to prevent concurrent with blkcg_deactivate_policy().
646 ret
= blk_queue_enter(q
, 0);
651 spin_lock_irq(&q
->queue_lock
);
653 blkg
= blkg_lookup_check(blkcg
, pol
, q
);
663 * Create blkgs walking down from blkcg_root to @blkcg, so that all
664 * non-root blkgs have access to their parents.
667 struct blkcg
*pos
= blkcg
;
668 struct blkcg
*parent
;
669 struct blkcg_gq
*new_blkg
;
671 parent
= blkcg_parent(blkcg
);
672 while (parent
&& !__blkg_lookup(parent
, q
, false)) {
674 parent
= blkcg_parent(parent
);
677 /* Drop locks to do new blkg allocation with GFP_KERNEL. */
678 spin_unlock_irq(&q
->queue_lock
);
681 new_blkg
= blkg_alloc(pos
, q
, GFP_KERNEL
);
682 if (unlikely(!new_blkg
)) {
684 goto fail_exit_queue
;
687 if (radix_tree_preload(GFP_KERNEL
)) {
690 goto fail_exit_queue
;
694 spin_lock_irq(&q
->queue_lock
);
696 blkg
= blkg_lookup_check(pos
, pol
, q
);
706 blkg
= blkg_create(pos
, q
, new_blkg
);
713 radix_tree_preload_end();
726 radix_tree_preload_end();
728 spin_unlock_irq(&q
->queue_lock
);
733 blkdev_put_no_open(bdev
);
735 * If queue was bypassing, we should retry. Do so after a
736 * short msleep(). It isn't strictly necessary but queue
737 * can be bypassing for some time and it's always nice to
738 * avoid busy looping.
742 ret
= restart_syscall();
746 EXPORT_SYMBOL_GPL(blkg_conf_prep
);
749 * blkg_conf_finish - finish up per-blkg config update
750 * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
752 * Finish up after per-blkg config update. This function must be paired
753 * with blkg_conf_prep().
755 void blkg_conf_finish(struct blkg_conf_ctx
*ctx
)
756 __releases(&ctx
->bdev
->bd_queue
->queue_lock
) __releases(rcu
)
758 spin_unlock_irq(&bdev_get_queue(ctx
->bdev
)->queue_lock
);
760 blkdev_put_no_open(ctx
->bdev
);
762 EXPORT_SYMBOL_GPL(blkg_conf_finish
);
764 static void blkg_iostat_set(struct blkg_iostat
*dst
, struct blkg_iostat
*src
)
768 for (i
= 0; i
< BLKG_IOSTAT_NR
; i
++) {
769 dst
->bytes
[i
] = src
->bytes
[i
];
770 dst
->ios
[i
] = src
->ios
[i
];
774 static void blkg_iostat_add(struct blkg_iostat
*dst
, struct blkg_iostat
*src
)
778 for (i
= 0; i
< BLKG_IOSTAT_NR
; i
++) {
779 dst
->bytes
[i
] += src
->bytes
[i
];
780 dst
->ios
[i
] += src
->ios
[i
];
784 static void blkg_iostat_sub(struct blkg_iostat
*dst
, struct blkg_iostat
*src
)
788 for (i
= 0; i
< BLKG_IOSTAT_NR
; i
++) {
789 dst
->bytes
[i
] -= src
->bytes
[i
];
790 dst
->ios
[i
] -= src
->ios
[i
];
794 static void blkcg_rstat_flush(struct cgroup_subsys_state
*css
, int cpu
)
796 struct blkcg
*blkcg
= css_to_blkcg(css
);
797 struct blkcg_gq
*blkg
;
799 /* Root-level stats are sourced from system-wide IO stats */
800 if (!cgroup_parent(css
->cgroup
))
805 hlist_for_each_entry_rcu(blkg
, &blkcg
->blkg_list
, blkcg_node
) {
806 struct blkcg_gq
*parent
= blkg
->parent
;
807 struct blkg_iostat_set
*bisc
= per_cpu_ptr(blkg
->iostat_cpu
, cpu
);
808 struct blkg_iostat cur
, delta
;
812 /* fetch the current per-cpu values */
814 seq
= u64_stats_fetch_begin(&bisc
->sync
);
815 blkg_iostat_set(&cur
, &bisc
->cur
);
816 } while (u64_stats_fetch_retry(&bisc
->sync
, seq
));
818 /* propagate percpu delta to global */
819 flags
= u64_stats_update_begin_irqsave(&blkg
->iostat
.sync
);
820 blkg_iostat_set(&delta
, &cur
);
821 blkg_iostat_sub(&delta
, &bisc
->last
);
822 blkg_iostat_add(&blkg
->iostat
.cur
, &delta
);
823 blkg_iostat_add(&bisc
->last
, &delta
);
824 u64_stats_update_end_irqrestore(&blkg
->iostat
.sync
, flags
);
826 /* propagate global delta to parent (unless that's root) */
827 if (parent
&& parent
->parent
) {
828 flags
= u64_stats_update_begin_irqsave(&parent
->iostat
.sync
);
829 blkg_iostat_set(&delta
, &blkg
->iostat
.cur
);
830 blkg_iostat_sub(&delta
, &blkg
->iostat
.last
);
831 blkg_iostat_add(&parent
->iostat
.cur
, &delta
);
832 blkg_iostat_add(&blkg
->iostat
.last
, &delta
);
833 u64_stats_update_end_irqrestore(&parent
->iostat
.sync
, flags
);
841 * We source root cgroup stats from the system-wide stats to avoid
842 * tracking the same information twice and incurring overhead when no
843 * cgroups are defined. For that reason, cgroup_rstat_flush in
844 * blkcg_print_stat does not actually fill out the iostat in the root
847 * However, we would like to re-use the printing code between the root and
848 * non-root cgroups to the extent possible. For that reason, we simulate
849 * flushing the root cgroup's stats by explicitly filling in the iostat
850 * with disk level statistics.
852 static void blkcg_fill_root_iostats(void)
854 struct class_dev_iter iter
;
857 class_dev_iter_init(&iter
, &block_class
, NULL
, &disk_type
);
858 while ((dev
= class_dev_iter_next(&iter
))) {
859 struct block_device
*bdev
= dev_to_bdev(dev
);
860 struct blkcg_gq
*blkg
=
861 blk_queue_root_blkg(bdev_get_queue(bdev
));
862 struct blkg_iostat tmp
;
866 memset(&tmp
, 0, sizeof(tmp
));
867 for_each_possible_cpu(cpu
) {
868 struct disk_stats
*cpu_dkstats
;
870 cpu_dkstats
= per_cpu_ptr(bdev
->bd_stats
, cpu
);
871 tmp
.ios
[BLKG_IOSTAT_READ
] +=
872 cpu_dkstats
->ios
[STAT_READ
];
873 tmp
.ios
[BLKG_IOSTAT_WRITE
] +=
874 cpu_dkstats
->ios
[STAT_WRITE
];
875 tmp
.ios
[BLKG_IOSTAT_DISCARD
] +=
876 cpu_dkstats
->ios
[STAT_DISCARD
];
877 // convert sectors to bytes
878 tmp
.bytes
[BLKG_IOSTAT_READ
] +=
879 cpu_dkstats
->sectors
[STAT_READ
] << 9;
880 tmp
.bytes
[BLKG_IOSTAT_WRITE
] +=
881 cpu_dkstats
->sectors
[STAT_WRITE
] << 9;
882 tmp
.bytes
[BLKG_IOSTAT_DISCARD
] +=
883 cpu_dkstats
->sectors
[STAT_DISCARD
] << 9;
886 flags
= u64_stats_update_begin_irqsave(&blkg
->iostat
.sync
);
887 blkg_iostat_set(&blkg
->iostat
.cur
, &tmp
);
888 u64_stats_update_end_irqrestore(&blkg
->iostat
.sync
, flags
);
892 static void blkcg_print_one_stat(struct blkcg_gq
*blkg
, struct seq_file
*s
)
894 struct blkg_iostat_set
*bis
= &blkg
->iostat
;
895 u64 rbytes
, wbytes
, rios
, wios
, dbytes
, dios
;
896 bool has_stats
= false;
904 dname
= blkg_dev_name(blkg
);
908 seq_printf(s
, "%s ", dname
);
911 seq
= u64_stats_fetch_begin(&bis
->sync
);
913 rbytes
= bis
->cur
.bytes
[BLKG_IOSTAT_READ
];
914 wbytes
= bis
->cur
.bytes
[BLKG_IOSTAT_WRITE
];
915 dbytes
= bis
->cur
.bytes
[BLKG_IOSTAT_DISCARD
];
916 rios
= bis
->cur
.ios
[BLKG_IOSTAT_READ
];
917 wios
= bis
->cur
.ios
[BLKG_IOSTAT_WRITE
];
918 dios
= bis
->cur
.ios
[BLKG_IOSTAT_DISCARD
];
919 } while (u64_stats_fetch_retry(&bis
->sync
, seq
));
921 if (rbytes
|| wbytes
|| rios
|| wios
) {
923 seq_printf(s
, "rbytes=%llu wbytes=%llu rios=%llu wios=%llu dbytes=%llu dios=%llu",
924 rbytes
, wbytes
, rios
, wios
,
928 if (blkcg_debug_stats
&& atomic_read(&blkg
->use_delay
)) {
930 seq_printf(s
, " use_delay=%d delay_nsec=%llu",
931 atomic_read(&blkg
->use_delay
),
932 atomic64_read(&blkg
->delay_nsec
));
935 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
936 struct blkcg_policy
*pol
= blkcg_policy
[i
];
938 if (!blkg
->pd
[i
] || !pol
->pd_stat_fn
)
941 if (pol
->pd_stat_fn(blkg
->pd
[i
], s
))
949 static int blkcg_print_stat(struct seq_file
*sf
, void *v
)
951 struct blkcg
*blkcg
= css_to_blkcg(seq_css(sf
));
952 struct blkcg_gq
*blkg
;
954 if (!seq_css(sf
)->parent
)
955 blkcg_fill_root_iostats();
957 cgroup_rstat_flush(blkcg
->css
.cgroup
);
960 hlist_for_each_entry_rcu(blkg
, &blkcg
->blkg_list
, blkcg_node
) {
961 spin_lock_irq(&blkg
->q
->queue_lock
);
962 blkcg_print_one_stat(blkg
, sf
);
963 spin_unlock_irq(&blkg
->q
->queue_lock
);
969 static struct cftype blkcg_files
[] = {
972 .seq_show
= blkcg_print_stat
,
977 static struct cftype blkcg_legacy_files
[] = {
979 .name
= "reset_stats",
980 .write_u64
= blkcg_reset_stats
,
986 * blkcg destruction is a three-stage process.
988 * 1. Destruction starts. The blkcg_css_offline() callback is invoked
989 * which offlines writeback. Here we tie the next stage of blkg destruction
990 * to the completion of writeback associated with the blkcg. This lets us
991 * avoid punting potentially large amounts of outstanding writeback to root
992 * while maintaining any ongoing policies. The next stage is triggered when
993 * the nr_cgwbs count goes to zero.
995 * 2. When the nr_cgwbs count goes to zero, blkcg_destroy_blkgs() is called
996 * and handles the destruction of blkgs. Here the css reference held by
997 * the blkg is put back eventually allowing blkcg_css_free() to be called.
998 * This work may occur in cgwb_release_workfn() on the cgwb_release
999 * workqueue. Any submitted ios that fail to get the blkg ref will be
1000 * punted to the root_blkg.
1002 * 3. Once the blkcg ref count goes to zero, blkcg_css_free() is called.
1003 * This finally frees the blkcg.
1007 * blkcg_css_offline - cgroup css_offline callback
1008 * @css: css of interest
1010 * This function is called when @css is about to go away. Here the cgwbs are
1011 * offlined first and only once writeback associated with the blkcg has
1012 * finished do we start step 2 (see above).
1014 static void blkcg_css_offline(struct cgroup_subsys_state
*css
)
1016 struct blkcg
*blkcg
= css_to_blkcg(css
);
1018 /* this prevents anyone from attaching or migrating to this blkcg */
1019 wb_blkcg_offline(blkcg
);
1021 /* put the base online pin allowing step 2 to be triggered */
1022 blkcg_unpin_online(blkcg
);
1026 * blkcg_destroy_blkgs - responsible for shooting down blkgs
1027 * @blkcg: blkcg of interest
1029 * blkgs should be removed while holding both q and blkcg locks. As blkcg lock
1030 * is nested inside q lock, this function performs reverse double lock dancing.
1031 * Destroying the blkgs releases the reference held on the blkcg's css allowing
1032 * blkcg_css_free to eventually be called.
1034 * This is the blkcg counterpart of ioc_release_fn().
1036 void blkcg_destroy_blkgs(struct blkcg
*blkcg
)
1040 spin_lock_irq(&blkcg
->lock
);
1042 while (!hlist_empty(&blkcg
->blkg_list
)) {
1043 struct blkcg_gq
*blkg
= hlist_entry(blkcg
->blkg_list
.first
,
1044 struct blkcg_gq
, blkcg_node
);
1045 struct request_queue
*q
= blkg
->q
;
1047 if (need_resched() || !spin_trylock(&q
->queue_lock
)) {
1049 * Given that the system can accumulate a huge number
1050 * of blkgs in pathological cases, check to see if we
1051 * need to rescheduling to avoid softlockup.
1053 spin_unlock_irq(&blkcg
->lock
);
1055 spin_lock_irq(&blkcg
->lock
);
1060 spin_unlock(&q
->queue_lock
);
1063 spin_unlock_irq(&blkcg
->lock
);
1066 static void blkcg_css_free(struct cgroup_subsys_state
*css
)
1068 struct blkcg
*blkcg
= css_to_blkcg(css
);
1071 mutex_lock(&blkcg_pol_mutex
);
1073 list_del(&blkcg
->all_blkcgs_node
);
1075 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++)
1077 blkcg_policy
[i
]->cpd_free_fn(blkcg
->cpd
[i
]);
1079 mutex_unlock(&blkcg_pol_mutex
);
1084 static struct cgroup_subsys_state
*
1085 blkcg_css_alloc(struct cgroup_subsys_state
*parent_css
)
1087 struct blkcg
*blkcg
;
1088 struct cgroup_subsys_state
*ret
;
1091 mutex_lock(&blkcg_pol_mutex
);
1094 blkcg
= &blkcg_root
;
1096 blkcg
= kzalloc(sizeof(*blkcg
), GFP_KERNEL
);
1098 ret
= ERR_PTR(-ENOMEM
);
1103 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
1104 struct blkcg_policy
*pol
= blkcg_policy
[i
];
1105 struct blkcg_policy_data
*cpd
;
1108 * If the policy hasn't been attached yet, wait for it
1109 * to be attached before doing anything else. Otherwise,
1110 * check if the policy requires any specific per-cgroup
1111 * data: if it does, allocate and initialize it.
1113 if (!pol
|| !pol
->cpd_alloc_fn
)
1116 cpd
= pol
->cpd_alloc_fn(GFP_KERNEL
);
1118 ret
= ERR_PTR(-ENOMEM
);
1121 blkcg
->cpd
[i
] = cpd
;
1124 if (pol
->cpd_init_fn
)
1125 pol
->cpd_init_fn(cpd
);
1128 spin_lock_init(&blkcg
->lock
);
1129 refcount_set(&blkcg
->online_pin
, 1);
1130 INIT_RADIX_TREE(&blkcg
->blkg_tree
, GFP_NOWAIT
| __GFP_NOWARN
);
1131 INIT_HLIST_HEAD(&blkcg
->blkg_list
);
1132 #ifdef CONFIG_CGROUP_WRITEBACK
1133 INIT_LIST_HEAD(&blkcg
->cgwb_list
);
1135 list_add_tail(&blkcg
->all_blkcgs_node
, &all_blkcgs
);
1137 mutex_unlock(&blkcg_pol_mutex
);
1141 for (i
--; i
>= 0; i
--)
1143 blkcg_policy
[i
]->cpd_free_fn(blkcg
->cpd
[i
]);
1145 if (blkcg
!= &blkcg_root
)
1148 mutex_unlock(&blkcg_pol_mutex
);
1152 static int blkcg_css_online(struct cgroup_subsys_state
*css
)
1154 struct blkcg
*blkcg
= css_to_blkcg(css
);
1155 struct blkcg
*parent
= blkcg_parent(blkcg
);
1158 * blkcg_pin_online() is used to delay blkcg offline so that blkgs
1159 * don't go offline while cgwbs are still active on them. Pin the
1160 * parent so that offline always happens towards the root.
1163 blkcg_pin_online(parent
);
1168 * blkcg_init_queue - initialize blkcg part of request queue
1169 * @q: request_queue to initialize
1171 * Called from blk_alloc_queue(). Responsible for initializing blkcg
1172 * part of new request_queue @q.
1175 * 0 on success, -errno on failure.
1177 int blkcg_init_queue(struct request_queue
*q
)
1179 struct blkcg_gq
*new_blkg
, *blkg
;
1183 INIT_LIST_HEAD(&q
->blkg_list
);
1185 new_blkg
= blkg_alloc(&blkcg_root
, q
, GFP_KERNEL
);
1189 preloaded
= !radix_tree_preload(GFP_KERNEL
);
1191 /* Make sure the root blkg exists. */
1193 spin_lock_irq(&q
->queue_lock
);
1194 blkg
= blkg_create(&blkcg_root
, q
, new_blkg
);
1197 q
->root_blkg
= blkg
;
1198 spin_unlock_irq(&q
->queue_lock
);
1202 radix_tree_preload_end();
1204 ret
= blk_ioprio_init(q
);
1206 goto err_destroy_all
;
1208 ret
= blk_throtl_init(q
);
1210 goto err_destroy_all
;
1212 ret
= blk_iolatency_init(q
);
1215 goto err_destroy_all
;
1221 blkg_destroy_all(q
);
1224 spin_unlock_irq(&q
->queue_lock
);
1227 radix_tree_preload_end();
1228 return PTR_ERR(blkg
);
1232 * blkcg_exit_queue - exit and release blkcg part of request_queue
1233 * @q: request_queue being released
1235 * Called from blk_exit_queue(). Responsible for exiting blkcg part.
1237 void blkcg_exit_queue(struct request_queue
*q
)
1239 blkg_destroy_all(q
);
1243 static void blkcg_bind(struct cgroup_subsys_state
*root_css
)
1247 mutex_lock(&blkcg_pol_mutex
);
1249 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
1250 struct blkcg_policy
*pol
= blkcg_policy
[i
];
1251 struct blkcg
*blkcg
;
1253 if (!pol
|| !pol
->cpd_bind_fn
)
1256 list_for_each_entry(blkcg
, &all_blkcgs
, all_blkcgs_node
)
1257 if (blkcg
->cpd
[pol
->plid
])
1258 pol
->cpd_bind_fn(blkcg
->cpd
[pol
->plid
]);
1260 mutex_unlock(&blkcg_pol_mutex
);
1263 static void blkcg_exit(struct task_struct
*tsk
)
1265 if (tsk
->throttle_queue
)
1266 blk_put_queue(tsk
->throttle_queue
);
1267 tsk
->throttle_queue
= NULL
;
1270 struct cgroup_subsys io_cgrp_subsys
= {
1271 .css_alloc
= blkcg_css_alloc
,
1272 .css_online
= blkcg_css_online
,
1273 .css_offline
= blkcg_css_offline
,
1274 .css_free
= blkcg_css_free
,
1275 .css_rstat_flush
= blkcg_rstat_flush
,
1277 .dfl_cftypes
= blkcg_files
,
1278 .legacy_cftypes
= blkcg_legacy_files
,
1279 .legacy_name
= "blkio",
1283 * This ensures that, if available, memcg is automatically enabled
1284 * together on the default hierarchy so that the owner cgroup can
1285 * be retrieved from writeback pages.
1287 .depends_on
= 1 << memory_cgrp_id
,
1290 EXPORT_SYMBOL_GPL(io_cgrp_subsys
);
1293 * blkcg_activate_policy - activate a blkcg policy on a request_queue
1294 * @q: request_queue of interest
1295 * @pol: blkcg policy to activate
1297 * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through
1298 * bypass mode to populate its blkgs with policy_data for @pol.
1300 * Activation happens with @q bypassed, so nobody would be accessing blkgs
1301 * from IO path. Update of each blkg is protected by both queue and blkcg
1302 * locks so that holding either lock and testing blkcg_policy_enabled() is
1303 * always enough for dereferencing policy data.
1305 * The caller is responsible for synchronizing [de]activations and policy
1306 * [un]registerations. Returns 0 on success, -errno on failure.
1308 int blkcg_activate_policy(struct request_queue
*q
,
1309 const struct blkcg_policy
*pol
)
1311 struct blkg_policy_data
*pd_prealloc
= NULL
;
1312 struct blkcg_gq
*blkg
, *pinned_blkg
= NULL
;
1315 if (blkcg_policy_enabled(q
, pol
))
1319 blk_mq_freeze_queue(q
);
1321 spin_lock_irq(&q
->queue_lock
);
1323 /* blkg_list is pushed at the head, reverse walk to allocate parents first */
1324 list_for_each_entry_reverse(blkg
, &q
->blkg_list
, q_node
) {
1325 struct blkg_policy_data
*pd
;
1327 if (blkg
->pd
[pol
->plid
])
1330 /* If prealloc matches, use it; otherwise try GFP_NOWAIT */
1331 if (blkg
== pinned_blkg
) {
1335 pd
= pol
->pd_alloc_fn(GFP_NOWAIT
| __GFP_NOWARN
, q
,
1341 * GFP_NOWAIT failed. Free the existing one and
1342 * prealloc for @blkg w/ GFP_KERNEL.
1345 blkg_put(pinned_blkg
);
1349 spin_unlock_irq(&q
->queue_lock
);
1352 pol
->pd_free_fn(pd_prealloc
);
1353 pd_prealloc
= pol
->pd_alloc_fn(GFP_KERNEL
, q
,
1361 blkg
->pd
[pol
->plid
] = pd
;
1363 pd
->plid
= pol
->plid
;
1366 /* all allocated, init in the same order */
1367 if (pol
->pd_init_fn
)
1368 list_for_each_entry_reverse(blkg
, &q
->blkg_list
, q_node
)
1369 pol
->pd_init_fn(blkg
->pd
[pol
->plid
]);
1371 __set_bit(pol
->plid
, q
->blkcg_pols
);
1374 spin_unlock_irq(&q
->queue_lock
);
1377 blk_mq_unfreeze_queue(q
);
1379 blkg_put(pinned_blkg
);
1381 pol
->pd_free_fn(pd_prealloc
);
1385 /* alloc failed, nothing's initialized yet, free everything */
1386 spin_lock_irq(&q
->queue_lock
);
1387 list_for_each_entry(blkg
, &q
->blkg_list
, q_node
) {
1388 struct blkcg
*blkcg
= blkg
->blkcg
;
1390 spin_lock(&blkcg
->lock
);
1391 if (blkg
->pd
[pol
->plid
]) {
1392 pol
->pd_free_fn(blkg
->pd
[pol
->plid
]);
1393 blkg
->pd
[pol
->plid
] = NULL
;
1395 spin_unlock(&blkcg
->lock
);
1397 spin_unlock_irq(&q
->queue_lock
);
1401 EXPORT_SYMBOL_GPL(blkcg_activate_policy
);
1404 * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
1405 * @q: request_queue of interest
1406 * @pol: blkcg policy to deactivate
1408 * Deactivate @pol on @q. Follows the same synchronization rules as
1409 * blkcg_activate_policy().
1411 void blkcg_deactivate_policy(struct request_queue
*q
,
1412 const struct blkcg_policy
*pol
)
1414 struct blkcg_gq
*blkg
;
1416 if (!blkcg_policy_enabled(q
, pol
))
1420 blk_mq_freeze_queue(q
);
1422 spin_lock_irq(&q
->queue_lock
);
1424 __clear_bit(pol
->plid
, q
->blkcg_pols
);
1426 list_for_each_entry(blkg
, &q
->blkg_list
, q_node
) {
1427 struct blkcg
*blkcg
= blkg
->blkcg
;
1429 spin_lock(&blkcg
->lock
);
1430 if (blkg
->pd
[pol
->plid
]) {
1431 if (pol
->pd_offline_fn
)
1432 pol
->pd_offline_fn(blkg
->pd
[pol
->plid
]);
1433 pol
->pd_free_fn(blkg
->pd
[pol
->plid
]);
1434 blkg
->pd
[pol
->plid
] = NULL
;
1436 spin_unlock(&blkcg
->lock
);
1439 spin_unlock_irq(&q
->queue_lock
);
1442 blk_mq_unfreeze_queue(q
);
1444 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy
);
1447 * blkcg_policy_register - register a blkcg policy
1448 * @pol: blkcg policy to register
1450 * Register @pol with blkcg core. Might sleep and @pol may be modified on
1451 * successful registration. Returns 0 on success and -errno on failure.
1453 int blkcg_policy_register(struct blkcg_policy
*pol
)
1455 struct blkcg
*blkcg
;
1458 mutex_lock(&blkcg_pol_register_mutex
);
1459 mutex_lock(&blkcg_pol_mutex
);
1461 /* find an empty slot */
1463 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++)
1464 if (!blkcg_policy
[i
])
1466 if (i
>= BLKCG_MAX_POLS
) {
1467 pr_warn("blkcg_policy_register: BLKCG_MAX_POLS too small\n");
1471 /* Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs */
1472 if ((!pol
->cpd_alloc_fn
^ !pol
->cpd_free_fn
) ||
1473 (!pol
->pd_alloc_fn
^ !pol
->pd_free_fn
))
1478 blkcg_policy
[pol
->plid
] = pol
;
1480 /* allocate and install cpd's */
1481 if (pol
->cpd_alloc_fn
) {
1482 list_for_each_entry(blkcg
, &all_blkcgs
, all_blkcgs_node
) {
1483 struct blkcg_policy_data
*cpd
;
1485 cpd
= pol
->cpd_alloc_fn(GFP_KERNEL
);
1489 blkcg
->cpd
[pol
->plid
] = cpd
;
1491 cpd
->plid
= pol
->plid
;
1492 if (pol
->cpd_init_fn
)
1493 pol
->cpd_init_fn(cpd
);
1497 mutex_unlock(&blkcg_pol_mutex
);
1499 /* everything is in place, add intf files for the new policy */
1500 if (pol
->dfl_cftypes
)
1501 WARN_ON(cgroup_add_dfl_cftypes(&io_cgrp_subsys
,
1503 if (pol
->legacy_cftypes
)
1504 WARN_ON(cgroup_add_legacy_cftypes(&io_cgrp_subsys
,
1505 pol
->legacy_cftypes
));
1506 mutex_unlock(&blkcg_pol_register_mutex
);
1510 if (pol
->cpd_free_fn
) {
1511 list_for_each_entry(blkcg
, &all_blkcgs
, all_blkcgs_node
) {
1512 if (blkcg
->cpd
[pol
->plid
]) {
1513 pol
->cpd_free_fn(blkcg
->cpd
[pol
->plid
]);
1514 blkcg
->cpd
[pol
->plid
] = NULL
;
1518 blkcg_policy
[pol
->plid
] = NULL
;
1520 mutex_unlock(&blkcg_pol_mutex
);
1521 mutex_unlock(&blkcg_pol_register_mutex
);
1524 EXPORT_SYMBOL_GPL(blkcg_policy_register
);
1527 * blkcg_policy_unregister - unregister a blkcg policy
1528 * @pol: blkcg policy to unregister
1530 * Undo blkcg_policy_register(@pol). Might sleep.
1532 void blkcg_policy_unregister(struct blkcg_policy
*pol
)
1534 struct blkcg
*blkcg
;
1536 mutex_lock(&blkcg_pol_register_mutex
);
1538 if (WARN_ON(blkcg_policy
[pol
->plid
] != pol
))
1541 /* kill the intf files first */
1542 if (pol
->dfl_cftypes
)
1543 cgroup_rm_cftypes(pol
->dfl_cftypes
);
1544 if (pol
->legacy_cftypes
)
1545 cgroup_rm_cftypes(pol
->legacy_cftypes
);
1547 /* remove cpds and unregister */
1548 mutex_lock(&blkcg_pol_mutex
);
1550 if (pol
->cpd_free_fn
) {
1551 list_for_each_entry(blkcg
, &all_blkcgs
, all_blkcgs_node
) {
1552 if (blkcg
->cpd
[pol
->plid
]) {
1553 pol
->cpd_free_fn(blkcg
->cpd
[pol
->plid
]);
1554 blkcg
->cpd
[pol
->plid
] = NULL
;
1558 blkcg_policy
[pol
->plid
] = NULL
;
1560 mutex_unlock(&blkcg_pol_mutex
);
1562 mutex_unlock(&blkcg_pol_register_mutex
);
1564 EXPORT_SYMBOL_GPL(blkcg_policy_unregister
);
1566 bool __blkcg_punt_bio_submit(struct bio
*bio
)
1568 struct blkcg_gq
*blkg
= bio
->bi_blkg
;
1570 /* consume the flag first */
1571 bio
->bi_opf
&= ~REQ_CGROUP_PUNT
;
1573 /* never bounce for the root cgroup */
1577 spin_lock_bh(&blkg
->async_bio_lock
);
1578 bio_list_add(&blkg
->async_bios
, bio
);
1579 spin_unlock_bh(&blkg
->async_bio_lock
);
1581 queue_work(blkcg_punt_bio_wq
, &blkg
->async_bio_work
);
1586 * Scale the accumulated delay based on how long it has been since we updated
1587 * the delay. We only call this when we are adding delay, in case it's been a
1588 * while since we added delay, and when we are checking to see if we need to
1589 * delay a task, to account for any delays that may have occurred.
1591 static void blkcg_scale_delay(struct blkcg_gq
*blkg
, u64 now
)
1593 u64 old
= atomic64_read(&blkg
->delay_start
);
1595 /* negative use_delay means no scaling, see blkcg_set_delay() */
1596 if (atomic_read(&blkg
->use_delay
) < 0)
1600 * We only want to scale down every second. The idea here is that we
1601 * want to delay people for min(delay_nsec, NSEC_PER_SEC) in a certain
1602 * time window. We only want to throttle tasks for recent delay that
1603 * has occurred, in 1 second time windows since that's the maximum
1604 * things can be throttled. We save the current delay window in
1605 * blkg->last_delay so we know what amount is still left to be charged
1606 * to the blkg from this point onward. blkg->last_use keeps track of
1607 * the use_delay counter. The idea is if we're unthrottling the blkg we
1608 * are ok with whatever is happening now, and we can take away more of
1609 * the accumulated delay as we've already throttled enough that
1610 * everybody is happy with their IO latencies.
1612 if (time_before64(old
+ NSEC_PER_SEC
, now
) &&
1613 atomic64_cmpxchg(&blkg
->delay_start
, old
, now
) == old
) {
1614 u64 cur
= atomic64_read(&blkg
->delay_nsec
);
1615 u64 sub
= min_t(u64
, blkg
->last_delay
, now
- old
);
1616 int cur_use
= atomic_read(&blkg
->use_delay
);
1619 * We've been unthrottled, subtract a larger chunk of our
1620 * accumulated delay.
1622 if (cur_use
< blkg
->last_use
)
1623 sub
= max_t(u64
, sub
, blkg
->last_delay
>> 1);
1626 * This shouldn't happen, but handle it anyway. Our delay_nsec
1627 * should only ever be growing except here where we subtract out
1628 * min(last_delay, 1 second), but lord knows bugs happen and I'd
1629 * rather not end up with negative numbers.
1631 if (unlikely(cur
< sub
)) {
1632 atomic64_set(&blkg
->delay_nsec
, 0);
1633 blkg
->last_delay
= 0;
1635 atomic64_sub(sub
, &blkg
->delay_nsec
);
1636 blkg
->last_delay
= cur
- sub
;
1638 blkg
->last_use
= cur_use
;
1643 * This is called when we want to actually walk up the hierarchy and check to
1644 * see if we need to throttle, and then actually throttle if there is some
1645 * accumulated delay. This should only be called upon return to user space so
1646 * we're not holding some lock that would induce a priority inversion.
1648 static void blkcg_maybe_throttle_blkg(struct blkcg_gq
*blkg
, bool use_memdelay
)
1650 unsigned long pflags
;
1652 u64 now
= ktime_to_ns(ktime_get());
1657 while (blkg
->parent
) {
1658 int use_delay
= atomic_read(&blkg
->use_delay
);
1663 blkcg_scale_delay(blkg
, now
);
1664 this_delay
= atomic64_read(&blkg
->delay_nsec
);
1665 if (this_delay
> delay_nsec
) {
1666 delay_nsec
= this_delay
;
1667 clamp
= use_delay
> 0;
1670 blkg
= blkg
->parent
;
1677 * Let's not sleep for all eternity if we've amassed a huge delay.
1678 * Swapping or metadata IO can accumulate 10's of seconds worth of
1679 * delay, and we want userspace to be able to do _something_ so cap the
1680 * delays at 0.25s. If there's 10's of seconds worth of delay then the
1681 * tasks will be delayed for 0.25 second for every syscall. If
1682 * blkcg_set_delay() was used as indicated by negative use_delay, the
1683 * caller is responsible for regulating the range.
1686 delay_nsec
= min_t(u64
, delay_nsec
, 250 * NSEC_PER_MSEC
);
1689 psi_memstall_enter(&pflags
);
1691 exp
= ktime_add_ns(now
, delay_nsec
);
1692 tok
= io_schedule_prepare();
1694 __set_current_state(TASK_KILLABLE
);
1695 if (!schedule_hrtimeout(&exp
, HRTIMER_MODE_ABS
))
1697 } while (!fatal_signal_pending(current
));
1698 io_schedule_finish(tok
);
1701 psi_memstall_leave(&pflags
);
1705 * blkcg_maybe_throttle_current - throttle the current task if it has been marked
1707 * This is only called if we've been marked with set_notify_resume(). Obviously
1708 * we can be set_notify_resume() for reasons other than blkcg throttling, so we
1709 * check to see if current->throttle_queue is set and if not this doesn't do
1710 * anything. This should only ever be called by the resume code, it's not meant
1711 * to be called by people willy-nilly as it will actually do the work to
1712 * throttle the task if it is setup for throttling.
1714 void blkcg_maybe_throttle_current(void)
1716 struct request_queue
*q
= current
->throttle_queue
;
1717 struct cgroup_subsys_state
*css
;
1718 struct blkcg
*blkcg
;
1719 struct blkcg_gq
*blkg
;
1720 bool use_memdelay
= current
->use_memdelay
;
1725 current
->throttle_queue
= NULL
;
1726 current
->use_memdelay
= false;
1729 css
= kthread_blkcg();
1731 blkcg
= css_to_blkcg(css
);
1733 blkcg
= css_to_blkcg(task_css(current
, io_cgrp_id
));
1737 blkg
= blkg_lookup(blkcg
, q
);
1740 if (!blkg_tryget(blkg
))
1744 blkcg_maybe_throttle_blkg(blkg
, use_memdelay
);
1754 * blkcg_schedule_throttle - this task needs to check for throttling
1755 * @q: the request queue IO was submitted on
1756 * @use_memdelay: do we charge this to memory delay for PSI
1758 * This is called by the IO controller when we know there's delay accumulated
1759 * for the blkg for this task. We do not pass the blkg because there are places
1760 * we call this that may not have that information, the swapping code for
1761 * instance will only have a request_queue at that point. This set's the
1762 * notify_resume for the task to check and see if it requires throttling before
1763 * returning to user space.
1765 * We will only schedule once per syscall. You can call this over and over
1766 * again and it will only do the check once upon return to user space, and only
1767 * throttle once. If the task needs to be throttled again it'll need to be
1768 * re-set at the next time we see the task.
1770 void blkcg_schedule_throttle(struct request_queue
*q
, bool use_memdelay
)
1772 if (unlikely(current
->flags
& PF_KTHREAD
))
1775 if (current
->throttle_queue
!= q
) {
1776 if (!blk_get_queue(q
))
1779 if (current
->throttle_queue
)
1780 blk_put_queue(current
->throttle_queue
);
1781 current
->throttle_queue
= q
;
1785 current
->use_memdelay
= use_memdelay
;
1786 set_notify_resume(current
);
1790 * blkcg_add_delay - add delay to this blkg
1791 * @blkg: blkg of interest
1792 * @now: the current time in nanoseconds
1793 * @delta: how many nanoseconds of delay to add
1795 * Charge @delta to the blkg's current delay accumulation. This is used to
1796 * throttle tasks if an IO controller thinks we need more throttling.
1798 void blkcg_add_delay(struct blkcg_gq
*blkg
, u64 now
, u64 delta
)
1800 if (WARN_ON_ONCE(atomic_read(&blkg
->use_delay
) < 0))
1802 blkcg_scale_delay(blkg
, now
);
1803 atomic64_add(delta
, &blkg
->delay_nsec
);
1807 * blkg_tryget_closest - try and get a blkg ref on the closet blkg
1811 * As the failure mode here is to walk up the blkg tree, this ensure that the
1812 * blkg->parent pointers are always valid. This returns the blkg that it ended
1813 * up taking a reference on or %NULL if no reference was taken.
1815 static inline struct blkcg_gq
*blkg_tryget_closest(struct bio
*bio
,
1816 struct cgroup_subsys_state
*css
)
1818 struct blkcg_gq
*blkg
, *ret_blkg
= NULL
;
1821 blkg
= blkg_lookup_create(css_to_blkcg(css
),
1822 bdev_get_queue(bio
->bi_bdev
));
1824 if (blkg_tryget(blkg
)) {
1828 blkg
= blkg
->parent
;
1836 * bio_associate_blkg_from_css - associate a bio with a specified css
1840 * Associate @bio with the blkg found by combining the css's blkg and the
1841 * request_queue of the @bio. An association failure is handled by walking up
1842 * the blkg tree. Therefore, the blkg associated can be anything between @blkg
1843 * and q->root_blkg. This situation only happens when a cgroup is dying and
1844 * then the remaining bios will spill to the closest alive blkg.
1846 * A reference will be taken on the blkg and will be released when @bio is
1849 void bio_associate_blkg_from_css(struct bio
*bio
,
1850 struct cgroup_subsys_state
*css
)
1853 blkg_put(bio
->bi_blkg
);
1855 if (css
&& css
->parent
) {
1856 bio
->bi_blkg
= blkg_tryget_closest(bio
, css
);
1858 blkg_get(bdev_get_queue(bio
->bi_bdev
)->root_blkg
);
1859 bio
->bi_blkg
= bdev_get_queue(bio
->bi_bdev
)->root_blkg
;
1862 EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css
);
1865 * bio_associate_blkg - associate a bio with a blkg
1868 * Associate @bio with the blkg found from the bio's css and request_queue.
1869 * If one is not found, bio_lookup_blkg() creates the blkg. If a blkg is
1870 * already associated, the css is reused and association redone as the
1871 * request_queue may have changed.
1873 void bio_associate_blkg(struct bio
*bio
)
1875 struct cgroup_subsys_state
*css
;
1880 css
= &bio_blkcg(bio
)->css
;
1884 bio_associate_blkg_from_css(bio
, css
);
1888 EXPORT_SYMBOL_GPL(bio_associate_blkg
);
1891 * bio_clone_blkg_association - clone blkg association from src to dst bio
1892 * @dst: destination bio
1895 void bio_clone_blkg_association(struct bio
*dst
, struct bio
*src
)
1899 blkg_put(dst
->bi_blkg
);
1900 blkg_get(src
->bi_blkg
);
1901 dst
->bi_blkg
= src
->bi_blkg
;
1904 EXPORT_SYMBOL_GPL(bio_clone_blkg_association
);
1906 static int blk_cgroup_io_type(struct bio
*bio
)
1908 if (op_is_discard(bio
->bi_opf
))
1909 return BLKG_IOSTAT_DISCARD
;
1910 if (op_is_write(bio
->bi_opf
))
1911 return BLKG_IOSTAT_WRITE
;
1912 return BLKG_IOSTAT_READ
;
1915 void blk_cgroup_bio_start(struct bio
*bio
)
1917 int rwd
= blk_cgroup_io_type(bio
), cpu
;
1918 struct blkg_iostat_set
*bis
;
1919 unsigned long flags
;
1922 bis
= per_cpu_ptr(bio
->bi_blkg
->iostat_cpu
, cpu
);
1923 flags
= u64_stats_update_begin_irqsave(&bis
->sync
);
1926 * If the bio is flagged with BIO_CGROUP_ACCT it means this is a split
1927 * bio and we would have already accounted for the size of the bio.
1929 if (!bio_flagged(bio
, BIO_CGROUP_ACCT
)) {
1930 bio_set_flag(bio
, BIO_CGROUP_ACCT
);
1931 bis
->cur
.bytes
[rwd
] += bio
->bi_iter
.bi_size
;
1933 bis
->cur
.ios
[rwd
]++;
1935 u64_stats_update_end_irqrestore(&bis
->sync
, flags
);
1936 if (cgroup_subsys_on_dfl(io_cgrp_subsys
))
1937 cgroup_rstat_updated(bio
->bi_blkg
->blkcg
->css
.cgroup
, cpu
);
1941 static int __init
blkcg_init(void)
1943 blkcg_punt_bio_wq
= alloc_workqueue("blkcg_punt_bio",
1944 WQ_MEM_RECLAIM
| WQ_FREEZABLE
|
1945 WQ_UNBOUND
| WQ_SYSFS
, 0);
1946 if (!blkcg_punt_bio_wq
)
1950 subsys_initcall(blkcg_init
);
1952 module_param(blkcg_debug_stats
, bool, 0644);
1953 MODULE_PARM_DESC(blkcg_debug_stats
, "True if you want debug stats, false if not");