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/genhd.h>
27 #include <linux/delay.h>
28 #include <linux/atomic.h>
29 #include <linux/ctype.h>
30 #include <linux/blk-cgroup.h>
31 #include <linux/tracehook.h>
32 #include <linux/psi.h>
35 #define MAX_KEY_LEN 100
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 static bool blkcg_debug_stats
= false;
58 static struct workqueue_struct
*blkcg_punt_bio_wq
;
60 static bool blkcg_policy_enabled(struct request_queue
*q
,
61 const struct blkcg_policy
*pol
)
63 return pol
&& test_bit(pol
->plid
, q
->blkcg_pols
);
67 * blkg_free - free a blkg
70 * Free @blkg which may be partially allocated.
72 static void blkg_free(struct blkcg_gq
*blkg
)
79 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++)
81 blkcg_policy
[i
]->pd_free_fn(blkg
->pd
[i
]);
83 blkg_rwstat_exit(&blkg
->stat_ios
);
84 blkg_rwstat_exit(&blkg
->stat_bytes
);
85 percpu_ref_exit(&blkg
->refcnt
);
89 static void __blkg_release(struct rcu_head
*rcu
)
91 struct blkcg_gq
*blkg
= container_of(rcu
, struct blkcg_gq
, rcu_head
);
93 WARN_ON(!bio_list_empty(&blkg
->async_bios
));
95 /* release the blkcg and parent blkg refs this blkg has been holding */
96 css_put(&blkg
->blkcg
->css
);
98 blkg_put(blkg
->parent
);
100 wb_congested_put(blkg
->wb_congested
);
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
;
127 /* as long as there are pending bios, @blkg can't go away */
128 spin_lock_bh(&blkg
->async_bio_lock
);
129 bio_list_merge(&bios
, &blkg
->async_bios
);
130 bio_list_init(&blkg
->async_bios
);
131 spin_unlock_bh(&blkg
->async_bio_lock
);
133 while ((bio
= bio_list_pop(&bios
)))
138 * blkg_alloc - allocate a blkg
139 * @blkcg: block cgroup the new blkg is associated with
140 * @q: request_queue the new blkg is associated with
141 * @gfp_mask: allocation mask to use
143 * Allocate a new blkg assocating @blkcg and @q.
145 static struct blkcg_gq
*blkg_alloc(struct blkcg
*blkcg
, struct request_queue
*q
,
148 struct blkcg_gq
*blkg
;
151 /* alloc and init base part */
152 blkg
= kzalloc_node(sizeof(*blkg
), gfp_mask
, q
->node
);
156 if (percpu_ref_init(&blkg
->refcnt
, blkg_release
, 0, gfp_mask
))
159 if (blkg_rwstat_init(&blkg
->stat_bytes
, gfp_mask
) ||
160 blkg_rwstat_init(&blkg
->stat_ios
, gfp_mask
))
164 INIT_LIST_HEAD(&blkg
->q_node
);
165 spin_lock_init(&blkg
->async_bio_lock
);
166 bio_list_init(&blkg
->async_bios
);
167 INIT_WORK(&blkg
->async_bio_work
, blkg_async_bio_workfn
);
170 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
171 struct blkcg_policy
*pol
= blkcg_policy
[i
];
172 struct blkg_policy_data
*pd
;
174 if (!blkcg_policy_enabled(q
, pol
))
177 /* alloc per-policy data and attach it to blkg */
178 pd
= pol
->pd_alloc_fn(gfp_mask
, q
->node
);
194 struct blkcg_gq
*blkg_lookup_slowpath(struct blkcg
*blkcg
,
195 struct request_queue
*q
, bool update_hint
)
197 struct blkcg_gq
*blkg
;
200 * Hint didn't match. Look up from the radix tree. Note that the
201 * hint can only be updated under queue_lock as otherwise @blkg
202 * could have already been removed from blkg_tree. The caller is
203 * responsible for grabbing queue_lock if @update_hint.
205 blkg
= radix_tree_lookup(&blkcg
->blkg_tree
, q
->id
);
206 if (blkg
&& blkg
->q
== q
) {
208 lockdep_assert_held(&q
->queue_lock
);
209 rcu_assign_pointer(blkcg
->blkg_hint
, blkg
);
216 EXPORT_SYMBOL_GPL(blkg_lookup_slowpath
);
219 * If @new_blkg is %NULL, this function tries to allocate a new one as
220 * necessary using %GFP_NOWAIT. @new_blkg is always consumed on return.
222 static struct blkcg_gq
*blkg_create(struct blkcg
*blkcg
,
223 struct request_queue
*q
,
224 struct blkcg_gq
*new_blkg
)
226 struct blkcg_gq
*blkg
;
227 struct bdi_writeback_congested
*wb_congested
;
230 WARN_ON_ONCE(!rcu_read_lock_held());
231 lockdep_assert_held(&q
->queue_lock
);
233 /* request_queue is dying, do not create/recreate a blkg */
234 if (blk_queue_dying(q
)) {
239 /* blkg holds a reference to blkcg */
240 if (!css_tryget_online(&blkcg
->css
)) {
245 wb_congested
= wb_congested_get_create(q
->backing_dev_info
,
247 GFP_NOWAIT
| __GFP_NOWARN
);
255 new_blkg
= blkg_alloc(blkcg
, q
, GFP_NOWAIT
| __GFP_NOWARN
);
256 if (unlikely(!new_blkg
)) {
258 goto err_put_congested
;
262 blkg
->wb_congested
= wb_congested
;
265 if (blkcg_parent(blkcg
)) {
266 blkg
->parent
= __blkg_lookup(blkcg_parent(blkcg
), q
, false);
267 if (WARN_ON_ONCE(!blkg
->parent
)) {
269 goto err_put_congested
;
271 blkg_get(blkg
->parent
);
274 /* invoke per-policy init */
275 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
276 struct blkcg_policy
*pol
= blkcg_policy
[i
];
278 if (blkg
->pd
[i
] && pol
->pd_init_fn
)
279 pol
->pd_init_fn(blkg
->pd
[i
]);
283 spin_lock(&blkcg
->lock
);
284 ret
= radix_tree_insert(&blkcg
->blkg_tree
, q
->id
, blkg
);
286 hlist_add_head_rcu(&blkg
->blkcg_node
, &blkcg
->blkg_list
);
287 list_add(&blkg
->q_node
, &q
->blkg_list
);
289 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
290 struct blkcg_policy
*pol
= blkcg_policy
[i
];
292 if (blkg
->pd
[i
] && pol
->pd_online_fn
)
293 pol
->pd_online_fn(blkg
->pd
[i
]);
297 spin_unlock(&blkcg
->lock
);
302 /* @blkg failed fully initialized, use the usual release path */
307 wb_congested_put(wb_congested
);
309 css_put(&blkcg
->css
);
316 * __blkg_lookup_create - lookup blkg, try to create one if not there
317 * @blkcg: blkcg of interest
318 * @q: request_queue of interest
320 * Lookup blkg for the @blkcg - @q pair. If it doesn't exist, try to
321 * create one. blkg creation is performed recursively from blkcg_root such
322 * that all non-root blkg's have access to the parent blkg. This function
323 * should be called under RCU read lock and @q->queue_lock.
325 * Returns the blkg or the closest blkg if blkg_create() fails as it walks
328 struct blkcg_gq
*__blkg_lookup_create(struct blkcg
*blkcg
,
329 struct request_queue
*q
)
331 struct blkcg_gq
*blkg
;
333 WARN_ON_ONCE(!rcu_read_lock_held());
334 lockdep_assert_held(&q
->queue_lock
);
336 blkg
= __blkg_lookup(blkcg
, q
, true);
341 * Create blkgs walking down from blkcg_root to @blkcg, so that all
342 * non-root blkgs have access to their parents. Returns the closest
343 * blkg to the intended blkg should blkg_create() fail.
346 struct blkcg
*pos
= blkcg
;
347 struct blkcg
*parent
= blkcg_parent(blkcg
);
348 struct blkcg_gq
*ret_blkg
= q
->root_blkg
;
351 blkg
= __blkg_lookup(parent
, q
, false);
353 /* remember closest blkg */
358 parent
= blkcg_parent(parent
);
361 blkg
= blkg_create(pos
, q
, NULL
);
370 * blkg_lookup_create - find or create a blkg
371 * @blkcg: target block cgroup
372 * @q: target request_queue
374 * This looks up or creates the blkg representing the unique pair
375 * of the blkcg and the request_queue.
377 struct blkcg_gq
*blkg_lookup_create(struct blkcg
*blkcg
,
378 struct request_queue
*q
)
380 struct blkcg_gq
*blkg
= blkg_lookup(blkcg
, q
);
382 if (unlikely(!blkg
)) {
385 spin_lock_irqsave(&q
->queue_lock
, flags
);
386 blkg
= __blkg_lookup_create(blkcg
, q
);
387 spin_unlock_irqrestore(&q
->queue_lock
, flags
);
393 static void blkg_destroy(struct blkcg_gq
*blkg
)
395 struct blkcg
*blkcg
= blkg
->blkcg
;
396 struct blkcg_gq
*parent
= blkg
->parent
;
399 lockdep_assert_held(&blkg
->q
->queue_lock
);
400 lockdep_assert_held(&blkcg
->lock
);
402 /* Something wrong if we are trying to remove same group twice */
403 WARN_ON_ONCE(list_empty(&blkg
->q_node
));
404 WARN_ON_ONCE(hlist_unhashed(&blkg
->blkcg_node
));
406 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
407 struct blkcg_policy
*pol
= blkcg_policy
[i
];
409 if (blkg
->pd
[i
] && pol
->pd_offline_fn
)
410 pol
->pd_offline_fn(blkg
->pd
[i
]);
414 blkg_rwstat_add_aux(&parent
->stat_bytes
, &blkg
->stat_bytes
);
415 blkg_rwstat_add_aux(&parent
->stat_ios
, &blkg
->stat_ios
);
418 blkg
->online
= false;
420 radix_tree_delete(&blkcg
->blkg_tree
, blkg
->q
->id
);
421 list_del_init(&blkg
->q_node
);
422 hlist_del_init_rcu(&blkg
->blkcg_node
);
425 * Both setting lookup hint to and clearing it from @blkg are done
426 * under queue_lock. If it's not pointing to @blkg now, it never
427 * will. Hint assignment itself can race safely.
429 if (rcu_access_pointer(blkcg
->blkg_hint
) == blkg
)
430 rcu_assign_pointer(blkcg
->blkg_hint
, NULL
);
433 * Put the reference taken at the time of creation so that when all
434 * queues are gone, group can be destroyed.
436 percpu_ref_kill(&blkg
->refcnt
);
440 * blkg_destroy_all - destroy all blkgs associated with a request_queue
441 * @q: request_queue of interest
443 * Destroy all blkgs associated with @q.
445 static void blkg_destroy_all(struct request_queue
*q
)
447 struct blkcg_gq
*blkg
, *n
;
449 spin_lock_irq(&q
->queue_lock
);
450 list_for_each_entry_safe(blkg
, n
, &q
->blkg_list
, q_node
) {
451 struct blkcg
*blkcg
= blkg
->blkcg
;
453 spin_lock(&blkcg
->lock
);
455 spin_unlock(&blkcg
->lock
);
459 spin_unlock_irq(&q
->queue_lock
);
462 static int blkcg_reset_stats(struct cgroup_subsys_state
*css
,
463 struct cftype
*cftype
, u64 val
)
465 struct blkcg
*blkcg
= css_to_blkcg(css
);
466 struct blkcg_gq
*blkg
;
469 mutex_lock(&blkcg_pol_mutex
);
470 spin_lock_irq(&blkcg
->lock
);
473 * Note that stat reset is racy - it doesn't synchronize against
474 * stat updates. This is a debug feature which shouldn't exist
475 * anyway. If you get hit by a race, retry.
477 hlist_for_each_entry(blkg
, &blkcg
->blkg_list
, blkcg_node
) {
478 blkg_rwstat_reset(&blkg
->stat_bytes
);
479 blkg_rwstat_reset(&blkg
->stat_ios
);
481 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
482 struct blkcg_policy
*pol
= blkcg_policy
[i
];
484 if (blkg
->pd
[i
] && pol
->pd_reset_stats_fn
)
485 pol
->pd_reset_stats_fn(blkg
->pd
[i
]);
489 spin_unlock_irq(&blkcg
->lock
);
490 mutex_unlock(&blkcg_pol_mutex
);
494 const char *blkg_dev_name(struct blkcg_gq
*blkg
)
496 /* some drivers (floppy) instantiate a queue w/o disk registered */
497 if (blkg
->q
->backing_dev_info
->dev
)
498 return dev_name(blkg
->q
->backing_dev_info
->dev
);
503 * blkcg_print_blkgs - helper for printing per-blkg data
504 * @sf: seq_file to print to
505 * @blkcg: blkcg of interest
506 * @prfill: fill function to print out a blkg
507 * @pol: policy in question
508 * @data: data to be passed to @prfill
509 * @show_total: to print out sum of prfill return values or not
511 * This function invokes @prfill on each blkg of @blkcg if pd for the
512 * policy specified by @pol exists. @prfill is invoked with @sf, the
513 * policy data and @data and the matching queue lock held. If @show_total
514 * is %true, the sum of the return values from @prfill is printed with
515 * "Total" label at the end.
517 * This is to be used to construct print functions for
518 * cftype->read_seq_string method.
520 void blkcg_print_blkgs(struct seq_file
*sf
, struct blkcg
*blkcg
,
521 u64 (*prfill
)(struct seq_file
*,
522 struct blkg_policy_data
*, int),
523 const struct blkcg_policy
*pol
, int data
,
526 struct blkcg_gq
*blkg
;
530 hlist_for_each_entry_rcu(blkg
, &blkcg
->blkg_list
, blkcg_node
) {
531 spin_lock_irq(&blkg
->q
->queue_lock
);
532 if (blkcg_policy_enabled(blkg
->q
, pol
))
533 total
+= prfill(sf
, blkg
->pd
[pol
->plid
], data
);
534 spin_unlock_irq(&blkg
->q
->queue_lock
);
539 seq_printf(sf
, "Total %llu\n", (unsigned long long)total
);
541 EXPORT_SYMBOL_GPL(blkcg_print_blkgs
);
544 * __blkg_prfill_u64 - prfill helper for a single u64 value
545 * @sf: seq_file to print to
546 * @pd: policy private data of interest
549 * Print @v to @sf for the device assocaited with @pd.
551 u64
__blkg_prfill_u64(struct seq_file
*sf
, struct blkg_policy_data
*pd
, u64 v
)
553 const char *dname
= blkg_dev_name(pd
->blkg
);
558 seq_printf(sf
, "%s %llu\n", dname
, (unsigned long long)v
);
561 EXPORT_SYMBOL_GPL(__blkg_prfill_u64
);
564 * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
565 * @sf: seq_file to print to
566 * @pd: policy private data of interest
567 * @rwstat: rwstat to print
569 * Print @rwstat to @sf for the device assocaited with @pd.
571 u64
__blkg_prfill_rwstat(struct seq_file
*sf
, struct blkg_policy_data
*pd
,
572 const struct blkg_rwstat_sample
*rwstat
)
574 static const char *rwstr
[] = {
575 [BLKG_RWSTAT_READ
] = "Read",
576 [BLKG_RWSTAT_WRITE
] = "Write",
577 [BLKG_RWSTAT_SYNC
] = "Sync",
578 [BLKG_RWSTAT_ASYNC
] = "Async",
579 [BLKG_RWSTAT_DISCARD
] = "Discard",
581 const char *dname
= blkg_dev_name(pd
->blkg
);
588 for (i
= 0; i
< BLKG_RWSTAT_NR
; i
++)
589 seq_printf(sf
, "%s %s %llu\n", dname
, rwstr
[i
],
592 v
= rwstat
->cnt
[BLKG_RWSTAT_READ
] +
593 rwstat
->cnt
[BLKG_RWSTAT_WRITE
] +
594 rwstat
->cnt
[BLKG_RWSTAT_DISCARD
];
595 seq_printf(sf
, "%s Total %llu\n", dname
, v
);
598 EXPORT_SYMBOL_GPL(__blkg_prfill_rwstat
);
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
,
611 struct blkg_rwstat_sample rwstat
= { };
613 blkg_rwstat_read((void *)pd
+ off
, &rwstat
);
614 return __blkg_prfill_rwstat(sf
, pd
, &rwstat
);
616 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat
);
618 static u64
blkg_prfill_rwstat_field(struct seq_file
*sf
,
619 struct blkg_policy_data
*pd
, int off
)
621 struct blkg_rwstat_sample rwstat
= { };
623 blkg_rwstat_read((void *)pd
->blkg
+ off
, &rwstat
);
624 return __blkg_prfill_rwstat(sf
, pd
, &rwstat
);
628 * blkg_print_stat_bytes - seq_show callback for blkg->stat_bytes
629 * @sf: seq_file to print to
632 * To be used as cftype->seq_show to print blkg->stat_bytes.
633 * cftype->private must be set to the blkcg_policy.
635 int blkg_print_stat_bytes(struct seq_file
*sf
, void *v
)
637 blkcg_print_blkgs(sf
, css_to_blkcg(seq_css(sf
)),
638 blkg_prfill_rwstat_field
, (void *)seq_cft(sf
)->private,
639 offsetof(struct blkcg_gq
, stat_bytes
), true);
642 EXPORT_SYMBOL_GPL(blkg_print_stat_bytes
);
645 * blkg_print_stat_bytes - seq_show callback for blkg->stat_ios
646 * @sf: seq_file to print to
649 * To be used as cftype->seq_show to print blkg->stat_ios. cftype->private
650 * must be set to the blkcg_policy.
652 int blkg_print_stat_ios(struct seq_file
*sf
, void *v
)
654 blkcg_print_blkgs(sf
, css_to_blkcg(seq_css(sf
)),
655 blkg_prfill_rwstat_field
, (void *)seq_cft(sf
)->private,
656 offsetof(struct blkcg_gq
, stat_ios
), true);
659 EXPORT_SYMBOL_GPL(blkg_print_stat_ios
);
661 static u64
blkg_prfill_rwstat_field_recursive(struct seq_file
*sf
,
662 struct blkg_policy_data
*pd
,
665 struct blkg_rwstat_sample rwstat
;
667 blkg_rwstat_recursive_sum(pd
->blkg
, NULL
, off
, &rwstat
);
668 return __blkg_prfill_rwstat(sf
, pd
, &rwstat
);
672 * blkg_print_stat_bytes_recursive - recursive version of blkg_print_stat_bytes
673 * @sf: seq_file to print to
676 int blkg_print_stat_bytes_recursive(struct seq_file
*sf
, void *v
)
678 blkcg_print_blkgs(sf
, css_to_blkcg(seq_css(sf
)),
679 blkg_prfill_rwstat_field_recursive
,
680 (void *)seq_cft(sf
)->private,
681 offsetof(struct blkcg_gq
, stat_bytes
), true);
684 EXPORT_SYMBOL_GPL(blkg_print_stat_bytes_recursive
);
687 * blkg_print_stat_ios_recursive - recursive version of blkg_print_stat_ios
688 * @sf: seq_file to print to
691 int blkg_print_stat_ios_recursive(struct seq_file
*sf
, void *v
)
693 blkcg_print_blkgs(sf
, css_to_blkcg(seq_css(sf
)),
694 blkg_prfill_rwstat_field_recursive
,
695 (void *)seq_cft(sf
)->private,
696 offsetof(struct blkcg_gq
, stat_ios
), true);
699 EXPORT_SYMBOL_GPL(blkg_print_stat_ios_recursive
);
702 * blkg_rwstat_recursive_sum - collect hierarchical blkg_rwstat
703 * @blkg: blkg of interest
704 * @pol: blkcg_policy which contains the blkg_rwstat
705 * @off: offset to the blkg_rwstat in blkg_policy_data or @blkg
706 * @sum: blkg_rwstat_sample structure containing the results
708 * Collect the blkg_rwstat specified by @blkg, @pol and @off and all its
709 * online descendants and their aux counts. The caller must be holding the
710 * queue lock for online tests.
712 * If @pol is NULL, blkg_rwstat is at @off bytes into @blkg; otherwise, it
713 * is at @off bytes into @blkg's blkg_policy_data of the policy.
715 void blkg_rwstat_recursive_sum(struct blkcg_gq
*blkg
, struct blkcg_policy
*pol
,
716 int off
, struct blkg_rwstat_sample
*sum
)
718 struct blkcg_gq
*pos_blkg
;
719 struct cgroup_subsys_state
*pos_css
;
722 lockdep_assert_held(&blkg
->q
->queue_lock
);
725 blkg_for_each_descendant_pre(pos_blkg
, pos_css
, blkg
) {
726 struct blkg_rwstat
*rwstat
;
728 if (!pos_blkg
->online
)
732 rwstat
= (void *)blkg_to_pd(pos_blkg
, pol
) + off
;
734 rwstat
= (void *)pos_blkg
+ off
;
736 for (i
= 0; i
< BLKG_RWSTAT_NR
; i
++)
737 sum
->cnt
[i
] = blkg_rwstat_read_counter(rwstat
, i
);
741 EXPORT_SYMBOL_GPL(blkg_rwstat_recursive_sum
);
743 /* Performs queue bypass and policy enabled checks then looks up blkg. */
744 static struct blkcg_gq
*blkg_lookup_check(struct blkcg
*blkcg
,
745 const struct blkcg_policy
*pol
,
746 struct request_queue
*q
)
748 WARN_ON_ONCE(!rcu_read_lock_held());
749 lockdep_assert_held(&q
->queue_lock
);
751 if (!blkcg_policy_enabled(q
, pol
))
752 return ERR_PTR(-EOPNOTSUPP
);
753 return __blkg_lookup(blkcg
, q
, true /* update_hint */);
757 * blkg_conf_prep - parse and prepare for per-blkg config update
758 * @blkcg: target block cgroup
759 * @pol: target policy
760 * @input: input string
761 * @ctx: blkg_conf_ctx to be filled
763 * Parse per-blkg config update from @input and initialize @ctx with the
764 * result. @ctx->blkg points to the blkg to be updated and @ctx->body the
765 * part of @input following MAJ:MIN. This function returns with RCU read
766 * lock and queue lock held and must be paired with blkg_conf_finish().
768 int blkg_conf_prep(struct blkcg
*blkcg
, const struct blkcg_policy
*pol
,
769 char *input
, struct blkg_conf_ctx
*ctx
)
770 __acquires(rcu
) __acquires(&disk
->queue
->queue_lock
)
772 struct gendisk
*disk
;
773 struct request_queue
*q
;
774 struct blkcg_gq
*blkg
;
775 unsigned int major
, minor
;
776 int key_len
, part
, ret
;
779 if (sscanf(input
, "%u:%u%n", &major
, &minor
, &key_len
) != 2)
782 body
= input
+ key_len
;
785 body
= skip_spaces(body
);
787 disk
= get_gendisk(MKDEV(major
, minor
), &part
);
798 spin_lock_irq(&q
->queue_lock
);
800 blkg
= blkg_lookup_check(blkcg
, pol
, q
);
810 * Create blkgs walking down from blkcg_root to @blkcg, so that all
811 * non-root blkgs have access to their parents.
814 struct blkcg
*pos
= blkcg
;
815 struct blkcg
*parent
;
816 struct blkcg_gq
*new_blkg
;
818 parent
= blkcg_parent(blkcg
);
819 while (parent
&& !__blkg_lookup(parent
, q
, false)) {
821 parent
= blkcg_parent(parent
);
824 /* Drop locks to do new blkg allocation with GFP_KERNEL. */
825 spin_unlock_irq(&q
->queue_lock
);
828 new_blkg
= blkg_alloc(pos
, q
, GFP_KERNEL
);
829 if (unlikely(!new_blkg
)) {
835 spin_lock_irq(&q
->queue_lock
);
837 blkg
= blkg_lookup_check(pos
, pol
, q
);
846 blkg
= blkg_create(pos
, q
, new_blkg
);
863 spin_unlock_irq(&q
->queue_lock
);
866 put_disk_and_module(disk
);
868 * If queue was bypassing, we should retry. Do so after a
869 * short msleep(). It isn't strictly necessary but queue
870 * can be bypassing for some time and it's always nice to
871 * avoid busy looping.
875 ret
= restart_syscall();
881 * blkg_conf_finish - finish up per-blkg config update
882 * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
884 * Finish up after per-blkg config update. This function must be paired
885 * with blkg_conf_prep().
887 void blkg_conf_finish(struct blkg_conf_ctx
*ctx
)
888 __releases(&ctx
->disk
->queue
->queue_lock
) __releases(rcu
)
890 spin_unlock_irq(&ctx
->disk
->queue
->queue_lock
);
892 put_disk_and_module(ctx
->disk
);
895 static int blkcg_print_stat(struct seq_file
*sf
, void *v
)
897 struct blkcg
*blkcg
= css_to_blkcg(seq_css(sf
));
898 struct blkcg_gq
*blkg
;
902 hlist_for_each_entry_rcu(blkg
, &blkcg
->blkg_list
, blkcg_node
) {
905 struct blkg_rwstat_sample rwstat
;
906 u64 rbytes
, wbytes
, rios
, wios
, dbytes
, dios
;
907 size_t size
= seq_get_buf(sf
, &buf
), off
= 0;
909 bool has_stats
= false;
911 dname
= blkg_dev_name(blkg
);
916 * Hooray string manipulation, count is the size written NOT
917 * INCLUDING THE \0, so size is now count+1 less than what we
918 * had before, but we want to start writing the next bit from
919 * the \0 so we only add count to buf.
921 off
+= scnprintf(buf
+off
, size
-off
, "%s ", dname
);
923 spin_lock_irq(&blkg
->q
->queue_lock
);
925 blkg_rwstat_recursive_sum(blkg
, NULL
,
926 offsetof(struct blkcg_gq
, stat_bytes
), &rwstat
);
927 rbytes
= rwstat
.cnt
[BLKG_RWSTAT_READ
];
928 wbytes
= rwstat
.cnt
[BLKG_RWSTAT_WRITE
];
929 dbytes
= rwstat
.cnt
[BLKG_RWSTAT_DISCARD
];
931 blkg_rwstat_recursive_sum(blkg
, NULL
,
932 offsetof(struct blkcg_gq
, stat_ios
), &rwstat
);
933 rios
= rwstat
.cnt
[BLKG_RWSTAT_READ
];
934 wios
= rwstat
.cnt
[BLKG_RWSTAT_WRITE
];
935 dios
= rwstat
.cnt
[BLKG_RWSTAT_DISCARD
];
937 spin_unlock_irq(&blkg
->q
->queue_lock
);
939 if (rbytes
|| wbytes
|| rios
|| wios
) {
941 off
+= scnprintf(buf
+off
, size
-off
,
942 "rbytes=%llu wbytes=%llu rios=%llu wios=%llu dbytes=%llu dios=%llu",
943 rbytes
, wbytes
, rios
, wios
,
947 if (!blkcg_debug_stats
)
950 if (atomic_read(&blkg
->use_delay
)) {
952 off
+= scnprintf(buf
+off
, size
-off
,
953 " use_delay=%d delay_nsec=%llu",
954 atomic_read(&blkg
->use_delay
),
955 (unsigned long long)atomic64_read(&blkg
->delay_nsec
));
958 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
959 struct blkcg_policy
*pol
= blkcg_policy
[i
];
962 if (!blkg
->pd
[i
] || !pol
->pd_stat_fn
)
965 written
= pol
->pd_stat_fn(blkg
->pd
[i
], buf
+off
, size
-off
);
972 if (off
< size
- 1) {
973 off
+= scnprintf(buf
+off
, size
-off
, "\n");
985 static struct cftype blkcg_files
[] = {
988 .flags
= CFTYPE_NOT_ON_ROOT
,
989 .seq_show
= blkcg_print_stat
,
994 static struct cftype blkcg_legacy_files
[] = {
996 .name
= "reset_stats",
997 .write_u64
= blkcg_reset_stats
,
1003 * blkcg destruction is a three-stage process.
1005 * 1. Destruction starts. The blkcg_css_offline() callback is invoked
1006 * which offlines writeback. Here we tie the next stage of blkg destruction
1007 * to the completion of writeback associated with the blkcg. This lets us
1008 * avoid punting potentially large amounts of outstanding writeback to root
1009 * while maintaining any ongoing policies. The next stage is triggered when
1010 * the nr_cgwbs count goes to zero.
1012 * 2. When the nr_cgwbs count goes to zero, blkcg_destroy_blkgs() is called
1013 * and handles the destruction of blkgs. Here the css reference held by
1014 * the blkg is put back eventually allowing blkcg_css_free() to be called.
1015 * This work may occur in cgwb_release_workfn() on the cgwb_release
1016 * workqueue. Any submitted ios that fail to get the blkg ref will be
1017 * punted to the root_blkg.
1019 * 3. Once the blkcg ref count goes to zero, blkcg_css_free() is called.
1020 * This finally frees the blkcg.
1024 * blkcg_css_offline - cgroup css_offline callback
1025 * @css: css of interest
1027 * This function is called when @css is about to go away. Here the cgwbs are
1028 * offlined first and only once writeback associated with the blkcg has
1029 * finished do we start step 2 (see above).
1031 static void blkcg_css_offline(struct cgroup_subsys_state
*css
)
1033 struct blkcg
*blkcg
= css_to_blkcg(css
);
1035 /* this prevents anyone from attaching or migrating to this blkcg */
1036 wb_blkcg_offline(blkcg
);
1038 /* put the base cgwb reference allowing step 2 to be triggered */
1039 blkcg_cgwb_put(blkcg
);
1043 * blkcg_destroy_blkgs - responsible for shooting down blkgs
1044 * @blkcg: blkcg of interest
1046 * blkgs should be removed while holding both q and blkcg locks. As blkcg lock
1047 * is nested inside q lock, this function performs reverse double lock dancing.
1048 * Destroying the blkgs releases the reference held on the blkcg's css allowing
1049 * blkcg_css_free to eventually be called.
1051 * This is the blkcg counterpart of ioc_release_fn().
1053 void blkcg_destroy_blkgs(struct blkcg
*blkcg
)
1055 spin_lock_irq(&blkcg
->lock
);
1057 while (!hlist_empty(&blkcg
->blkg_list
)) {
1058 struct blkcg_gq
*blkg
= hlist_entry(blkcg
->blkg_list
.first
,
1059 struct blkcg_gq
, blkcg_node
);
1060 struct request_queue
*q
= blkg
->q
;
1062 if (spin_trylock(&q
->queue_lock
)) {
1064 spin_unlock(&q
->queue_lock
);
1066 spin_unlock_irq(&blkcg
->lock
);
1068 spin_lock_irq(&blkcg
->lock
);
1072 spin_unlock_irq(&blkcg
->lock
);
1075 static void blkcg_css_free(struct cgroup_subsys_state
*css
)
1077 struct blkcg
*blkcg
= css_to_blkcg(css
);
1080 mutex_lock(&blkcg_pol_mutex
);
1082 list_del(&blkcg
->all_blkcgs_node
);
1084 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++)
1086 blkcg_policy
[i
]->cpd_free_fn(blkcg
->cpd
[i
]);
1088 mutex_unlock(&blkcg_pol_mutex
);
1093 static struct cgroup_subsys_state
*
1094 blkcg_css_alloc(struct cgroup_subsys_state
*parent_css
)
1096 struct blkcg
*blkcg
;
1097 struct cgroup_subsys_state
*ret
;
1100 mutex_lock(&blkcg_pol_mutex
);
1103 blkcg
= &blkcg_root
;
1105 blkcg
= kzalloc(sizeof(*blkcg
), GFP_KERNEL
);
1107 ret
= ERR_PTR(-ENOMEM
);
1112 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
1113 struct blkcg_policy
*pol
= blkcg_policy
[i
];
1114 struct blkcg_policy_data
*cpd
;
1117 * If the policy hasn't been attached yet, wait for it
1118 * to be attached before doing anything else. Otherwise,
1119 * check if the policy requires any specific per-cgroup
1120 * data: if it does, allocate and initialize it.
1122 if (!pol
|| !pol
->cpd_alloc_fn
)
1125 cpd
= pol
->cpd_alloc_fn(GFP_KERNEL
);
1127 ret
= ERR_PTR(-ENOMEM
);
1130 blkcg
->cpd
[i
] = cpd
;
1133 if (pol
->cpd_init_fn
)
1134 pol
->cpd_init_fn(cpd
);
1137 spin_lock_init(&blkcg
->lock
);
1138 INIT_RADIX_TREE(&blkcg
->blkg_tree
, GFP_NOWAIT
| __GFP_NOWARN
);
1139 INIT_HLIST_HEAD(&blkcg
->blkg_list
);
1140 #ifdef CONFIG_CGROUP_WRITEBACK
1141 INIT_LIST_HEAD(&blkcg
->cgwb_list
);
1142 refcount_set(&blkcg
->cgwb_refcnt
, 1);
1144 list_add_tail(&blkcg
->all_blkcgs_node
, &all_blkcgs
);
1146 mutex_unlock(&blkcg_pol_mutex
);
1150 for (i
--; i
>= 0; i
--)
1152 blkcg_policy
[i
]->cpd_free_fn(blkcg
->cpd
[i
]);
1154 if (blkcg
!= &blkcg_root
)
1157 mutex_unlock(&blkcg_pol_mutex
);
1162 * blkcg_init_queue - initialize blkcg part of request queue
1163 * @q: request_queue to initialize
1165 * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
1166 * part of new request_queue @q.
1169 * 0 on success, -errno on failure.
1171 int blkcg_init_queue(struct request_queue
*q
)
1173 struct blkcg_gq
*new_blkg
, *blkg
;
1177 new_blkg
= blkg_alloc(&blkcg_root
, q
, GFP_KERNEL
);
1181 preloaded
= !radix_tree_preload(GFP_KERNEL
);
1183 /* Make sure the root blkg exists. */
1185 spin_lock_irq(&q
->queue_lock
);
1186 blkg
= blkg_create(&blkcg_root
, q
, new_blkg
);
1189 q
->root_blkg
= blkg
;
1190 spin_unlock_irq(&q
->queue_lock
);
1194 radix_tree_preload_end();
1196 ret
= blk_iolatency_init(q
);
1198 goto err_destroy_all
;
1200 ret
= blk_throtl_init(q
);
1202 goto err_destroy_all
;
1206 blkg_destroy_all(q
);
1209 spin_unlock_irq(&q
->queue_lock
);
1212 radix_tree_preload_end();
1213 return PTR_ERR(blkg
);
1217 * blkcg_drain_queue - drain blkcg part of request_queue
1218 * @q: request_queue to drain
1220 * Called from blk_drain_queue(). Responsible for draining blkcg part.
1222 void blkcg_drain_queue(struct request_queue
*q
)
1224 lockdep_assert_held(&q
->queue_lock
);
1227 * @q could be exiting and already have destroyed all blkgs as
1228 * indicated by NULL root_blkg. If so, don't confuse policies.
1233 blk_throtl_drain(q
);
1237 * blkcg_exit_queue - exit and release blkcg part of request_queue
1238 * @q: request_queue being released
1240 * Called from blk_exit_queue(). Responsible for exiting blkcg part.
1242 void blkcg_exit_queue(struct request_queue
*q
)
1244 blkg_destroy_all(q
);
1249 * We cannot support shared io contexts, as we have no mean to support
1250 * two tasks with the same ioc in two different groups without major rework
1251 * of the main cic data structures. For now we allow a task to change
1252 * its cgroup only if it's the only owner of its ioc.
1254 static int blkcg_can_attach(struct cgroup_taskset
*tset
)
1256 struct task_struct
*task
;
1257 struct cgroup_subsys_state
*dst_css
;
1258 struct io_context
*ioc
;
1261 /* task_lock() is needed to avoid races with exit_io_context() */
1262 cgroup_taskset_for_each(task
, dst_css
, tset
) {
1264 ioc
= task
->io_context
;
1265 if (ioc
&& atomic_read(&ioc
->nr_tasks
) > 1)
1274 static void blkcg_bind(struct cgroup_subsys_state
*root_css
)
1278 mutex_lock(&blkcg_pol_mutex
);
1280 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++) {
1281 struct blkcg_policy
*pol
= blkcg_policy
[i
];
1282 struct blkcg
*blkcg
;
1284 if (!pol
|| !pol
->cpd_bind_fn
)
1287 list_for_each_entry(blkcg
, &all_blkcgs
, all_blkcgs_node
)
1288 if (blkcg
->cpd
[pol
->plid
])
1289 pol
->cpd_bind_fn(blkcg
->cpd
[pol
->plid
]);
1291 mutex_unlock(&blkcg_pol_mutex
);
1294 static void blkcg_exit(struct task_struct
*tsk
)
1296 if (tsk
->throttle_queue
)
1297 blk_put_queue(tsk
->throttle_queue
);
1298 tsk
->throttle_queue
= NULL
;
1301 struct cgroup_subsys io_cgrp_subsys
= {
1302 .css_alloc
= blkcg_css_alloc
,
1303 .css_offline
= blkcg_css_offline
,
1304 .css_free
= blkcg_css_free
,
1305 .can_attach
= blkcg_can_attach
,
1307 .dfl_cftypes
= blkcg_files
,
1308 .legacy_cftypes
= blkcg_legacy_files
,
1309 .legacy_name
= "blkio",
1313 * This ensures that, if available, memcg is automatically enabled
1314 * together on the default hierarchy so that the owner cgroup can
1315 * be retrieved from writeback pages.
1317 .depends_on
= 1 << memory_cgrp_id
,
1320 EXPORT_SYMBOL_GPL(io_cgrp_subsys
);
1323 * blkcg_activate_policy - activate a blkcg policy on a request_queue
1324 * @q: request_queue of interest
1325 * @pol: blkcg policy to activate
1327 * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through
1328 * bypass mode to populate its blkgs with policy_data for @pol.
1330 * Activation happens with @q bypassed, so nobody would be accessing blkgs
1331 * from IO path. Update of each blkg is protected by both queue and blkcg
1332 * locks so that holding either lock and testing blkcg_policy_enabled() is
1333 * always enough for dereferencing policy data.
1335 * The caller is responsible for synchronizing [de]activations and policy
1336 * [un]registerations. Returns 0 on success, -errno on failure.
1338 int blkcg_activate_policy(struct request_queue
*q
,
1339 const struct blkcg_policy
*pol
)
1341 struct blkg_policy_data
*pd_prealloc
= NULL
;
1342 struct blkcg_gq
*blkg
;
1345 if (blkcg_policy_enabled(q
, pol
))
1349 blk_mq_freeze_queue(q
);
1352 pd_prealloc
= pol
->pd_alloc_fn(GFP_KERNEL
, q
->node
);
1355 goto out_bypass_end
;
1359 spin_lock_irq(&q
->queue_lock
);
1361 /* blkg_list is pushed at the head, reverse walk to init parents first */
1362 list_for_each_entry_reverse(blkg
, &q
->blkg_list
, q_node
) {
1363 struct blkg_policy_data
*pd
;
1365 if (blkg
->pd
[pol
->plid
])
1368 pd
= pol
->pd_alloc_fn(GFP_NOWAIT
| __GFP_NOWARN
, q
->node
);
1370 swap(pd
, pd_prealloc
);
1372 spin_unlock_irq(&q
->queue_lock
);
1376 blkg
->pd
[pol
->plid
] = pd
;
1378 pd
->plid
= pol
->plid
;
1379 if (pol
->pd_init_fn
)
1380 pol
->pd_init_fn(pd
);
1383 __set_bit(pol
->plid
, q
->blkcg_pols
);
1386 spin_unlock_irq(&q
->queue_lock
);
1389 blk_mq_unfreeze_queue(q
);
1391 pol
->pd_free_fn(pd_prealloc
);
1394 EXPORT_SYMBOL_GPL(blkcg_activate_policy
);
1397 * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
1398 * @q: request_queue of interest
1399 * @pol: blkcg policy to deactivate
1401 * Deactivate @pol on @q. Follows the same synchronization rules as
1402 * blkcg_activate_policy().
1404 void blkcg_deactivate_policy(struct request_queue
*q
,
1405 const struct blkcg_policy
*pol
)
1407 struct blkcg_gq
*blkg
;
1409 if (!blkcg_policy_enabled(q
, pol
))
1413 blk_mq_freeze_queue(q
);
1415 spin_lock_irq(&q
->queue_lock
);
1417 __clear_bit(pol
->plid
, q
->blkcg_pols
);
1419 list_for_each_entry(blkg
, &q
->blkg_list
, q_node
) {
1420 if (blkg
->pd
[pol
->plid
]) {
1421 if (pol
->pd_offline_fn
)
1422 pol
->pd_offline_fn(blkg
->pd
[pol
->plid
]);
1423 pol
->pd_free_fn(blkg
->pd
[pol
->plid
]);
1424 blkg
->pd
[pol
->plid
] = NULL
;
1428 spin_unlock_irq(&q
->queue_lock
);
1431 blk_mq_unfreeze_queue(q
);
1433 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy
);
1436 * blkcg_policy_register - register a blkcg policy
1437 * @pol: blkcg policy to register
1439 * Register @pol with blkcg core. Might sleep and @pol may be modified on
1440 * successful registration. Returns 0 on success and -errno on failure.
1442 int blkcg_policy_register(struct blkcg_policy
*pol
)
1444 struct blkcg
*blkcg
;
1447 mutex_lock(&blkcg_pol_register_mutex
);
1448 mutex_lock(&blkcg_pol_mutex
);
1450 /* find an empty slot */
1452 for (i
= 0; i
< BLKCG_MAX_POLS
; i
++)
1453 if (!blkcg_policy
[i
])
1455 if (i
>= BLKCG_MAX_POLS
) {
1456 pr_warn("blkcg_policy_register: BLKCG_MAX_POLS too small\n");
1460 /* Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs */
1461 if ((!pol
->cpd_alloc_fn
^ !pol
->cpd_free_fn
) ||
1462 (!pol
->pd_alloc_fn
^ !pol
->pd_free_fn
))
1467 blkcg_policy
[pol
->plid
] = pol
;
1469 /* allocate and install cpd's */
1470 if (pol
->cpd_alloc_fn
) {
1471 list_for_each_entry(blkcg
, &all_blkcgs
, all_blkcgs_node
) {
1472 struct blkcg_policy_data
*cpd
;
1474 cpd
= pol
->cpd_alloc_fn(GFP_KERNEL
);
1478 blkcg
->cpd
[pol
->plid
] = cpd
;
1480 cpd
->plid
= pol
->plid
;
1481 pol
->cpd_init_fn(cpd
);
1485 mutex_unlock(&blkcg_pol_mutex
);
1487 /* everything is in place, add intf files for the new policy */
1488 if (pol
->dfl_cftypes
)
1489 WARN_ON(cgroup_add_dfl_cftypes(&io_cgrp_subsys
,
1491 if (pol
->legacy_cftypes
)
1492 WARN_ON(cgroup_add_legacy_cftypes(&io_cgrp_subsys
,
1493 pol
->legacy_cftypes
));
1494 mutex_unlock(&blkcg_pol_register_mutex
);
1498 if (pol
->cpd_free_fn
) {
1499 list_for_each_entry(blkcg
, &all_blkcgs
, all_blkcgs_node
) {
1500 if (blkcg
->cpd
[pol
->plid
]) {
1501 pol
->cpd_free_fn(blkcg
->cpd
[pol
->plid
]);
1502 blkcg
->cpd
[pol
->plid
] = NULL
;
1506 blkcg_policy
[pol
->plid
] = NULL
;
1508 mutex_unlock(&blkcg_pol_mutex
);
1509 mutex_unlock(&blkcg_pol_register_mutex
);
1512 EXPORT_SYMBOL_GPL(blkcg_policy_register
);
1515 * blkcg_policy_unregister - unregister a blkcg policy
1516 * @pol: blkcg policy to unregister
1518 * Undo blkcg_policy_register(@pol). Might sleep.
1520 void blkcg_policy_unregister(struct blkcg_policy
*pol
)
1522 struct blkcg
*blkcg
;
1524 mutex_lock(&blkcg_pol_register_mutex
);
1526 if (WARN_ON(blkcg_policy
[pol
->plid
] != pol
))
1529 /* kill the intf files first */
1530 if (pol
->dfl_cftypes
)
1531 cgroup_rm_cftypes(pol
->dfl_cftypes
);
1532 if (pol
->legacy_cftypes
)
1533 cgroup_rm_cftypes(pol
->legacy_cftypes
);
1535 /* remove cpds and unregister */
1536 mutex_lock(&blkcg_pol_mutex
);
1538 if (pol
->cpd_free_fn
) {
1539 list_for_each_entry(blkcg
, &all_blkcgs
, all_blkcgs_node
) {
1540 if (blkcg
->cpd
[pol
->plid
]) {
1541 pol
->cpd_free_fn(blkcg
->cpd
[pol
->plid
]);
1542 blkcg
->cpd
[pol
->plid
] = NULL
;
1546 blkcg_policy
[pol
->plid
] = NULL
;
1548 mutex_unlock(&blkcg_pol_mutex
);
1550 mutex_unlock(&blkcg_pol_register_mutex
);
1552 EXPORT_SYMBOL_GPL(blkcg_policy_unregister
);
1554 bool __blkcg_punt_bio_submit(struct bio
*bio
)
1556 struct blkcg_gq
*blkg
= bio
->bi_blkg
;
1558 /* consume the flag first */
1559 bio
->bi_opf
&= ~REQ_CGROUP_PUNT
;
1561 /* never bounce for the root cgroup */
1565 spin_lock_bh(&blkg
->async_bio_lock
);
1566 bio_list_add(&blkg
->async_bios
, bio
);
1567 spin_unlock_bh(&blkg
->async_bio_lock
);
1569 queue_work(blkcg_punt_bio_wq
, &blkg
->async_bio_work
);
1574 * Scale the accumulated delay based on how long it has been since we updated
1575 * the delay. We only call this when we are adding delay, in case it's been a
1576 * while since we added delay, and when we are checking to see if we need to
1577 * delay a task, to account for any delays that may have occurred.
1579 static void blkcg_scale_delay(struct blkcg_gq
*blkg
, u64 now
)
1581 u64 old
= atomic64_read(&blkg
->delay_start
);
1584 * We only want to scale down every second. The idea here is that we
1585 * want to delay people for min(delay_nsec, NSEC_PER_SEC) in a certain
1586 * time window. We only want to throttle tasks for recent delay that
1587 * has occurred, in 1 second time windows since that's the maximum
1588 * things can be throttled. We save the current delay window in
1589 * blkg->last_delay so we know what amount is still left to be charged
1590 * to the blkg from this point onward. blkg->last_use keeps track of
1591 * the use_delay counter. The idea is if we're unthrottling the blkg we
1592 * are ok with whatever is happening now, and we can take away more of
1593 * the accumulated delay as we've already throttled enough that
1594 * everybody is happy with their IO latencies.
1596 if (time_before64(old
+ NSEC_PER_SEC
, now
) &&
1597 atomic64_cmpxchg(&blkg
->delay_start
, old
, now
) == old
) {
1598 u64 cur
= atomic64_read(&blkg
->delay_nsec
);
1599 u64 sub
= min_t(u64
, blkg
->last_delay
, now
- old
);
1600 int cur_use
= atomic_read(&blkg
->use_delay
);
1603 * We've been unthrottled, subtract a larger chunk of our
1604 * accumulated delay.
1606 if (cur_use
< blkg
->last_use
)
1607 sub
= max_t(u64
, sub
, blkg
->last_delay
>> 1);
1610 * This shouldn't happen, but handle it anyway. Our delay_nsec
1611 * should only ever be growing except here where we subtract out
1612 * min(last_delay, 1 second), but lord knows bugs happen and I'd
1613 * rather not end up with negative numbers.
1615 if (unlikely(cur
< sub
)) {
1616 atomic64_set(&blkg
->delay_nsec
, 0);
1617 blkg
->last_delay
= 0;
1619 atomic64_sub(sub
, &blkg
->delay_nsec
);
1620 blkg
->last_delay
= cur
- sub
;
1622 blkg
->last_use
= cur_use
;
1627 * This is called when we want to actually walk up the hierarchy and check to
1628 * see if we need to throttle, and then actually throttle if there is some
1629 * accumulated delay. This should only be called upon return to user space so
1630 * we're not holding some lock that would induce a priority inversion.
1632 static void blkcg_maybe_throttle_blkg(struct blkcg_gq
*blkg
, bool use_memdelay
)
1634 unsigned long pflags
;
1635 u64 now
= ktime_to_ns(ktime_get());
1640 while (blkg
->parent
) {
1641 if (atomic_read(&blkg
->use_delay
)) {
1642 blkcg_scale_delay(blkg
, now
);
1643 delay_nsec
= max_t(u64
, delay_nsec
,
1644 atomic64_read(&blkg
->delay_nsec
));
1646 blkg
= blkg
->parent
;
1653 * Let's not sleep for all eternity if we've amassed a huge delay.
1654 * Swapping or metadata IO can accumulate 10's of seconds worth of
1655 * delay, and we want userspace to be able to do _something_ so cap the
1656 * delays at 1 second. If there's 10's of seconds worth of delay then
1657 * the tasks will be delayed for 1 second for every syscall.
1659 delay_nsec
= min_t(u64
, delay_nsec
, 250 * NSEC_PER_MSEC
);
1662 psi_memstall_enter(&pflags
);
1664 exp
= ktime_add_ns(now
, delay_nsec
);
1665 tok
= io_schedule_prepare();
1667 __set_current_state(TASK_KILLABLE
);
1668 if (!schedule_hrtimeout(&exp
, HRTIMER_MODE_ABS
))
1670 } while (!fatal_signal_pending(current
));
1671 io_schedule_finish(tok
);
1674 psi_memstall_leave(&pflags
);
1678 * blkcg_maybe_throttle_current - throttle the current task if it has been marked
1680 * This is only called if we've been marked with set_notify_resume(). Obviously
1681 * we can be set_notify_resume() for reasons other than blkcg throttling, so we
1682 * check to see if current->throttle_queue is set and if not this doesn't do
1683 * anything. This should only ever be called by the resume code, it's not meant
1684 * to be called by people willy-nilly as it will actually do the work to
1685 * throttle the task if it is setup for throttling.
1687 void blkcg_maybe_throttle_current(void)
1689 struct request_queue
*q
= current
->throttle_queue
;
1690 struct cgroup_subsys_state
*css
;
1691 struct blkcg
*blkcg
;
1692 struct blkcg_gq
*blkg
;
1693 bool use_memdelay
= current
->use_memdelay
;
1698 current
->throttle_queue
= NULL
;
1699 current
->use_memdelay
= false;
1702 css
= kthread_blkcg();
1704 blkcg
= css_to_blkcg(css
);
1706 blkcg
= css_to_blkcg(task_css(current
, io_cgrp_id
));
1710 blkg
= blkg_lookup(blkcg
, q
);
1713 if (!blkg_tryget(blkg
))
1717 blkcg_maybe_throttle_blkg(blkg
, use_memdelay
);
1727 * blkcg_schedule_throttle - this task needs to check for throttling
1728 * @q: the request queue IO was submitted on
1729 * @use_memdelay: do we charge this to memory delay for PSI
1731 * This is called by the IO controller when we know there's delay accumulated
1732 * for the blkg for this task. We do not pass the blkg because there are places
1733 * we call this that may not have that information, the swapping code for
1734 * instance will only have a request_queue at that point. This set's the
1735 * notify_resume for the task to check and see if it requires throttling before
1736 * returning to user space.
1738 * We will only schedule once per syscall. You can call this over and over
1739 * again and it will only do the check once upon return to user space, and only
1740 * throttle once. If the task needs to be throttled again it'll need to be
1741 * re-set at the next time we see the task.
1743 void blkcg_schedule_throttle(struct request_queue
*q
, bool use_memdelay
)
1745 if (unlikely(current
->flags
& PF_KTHREAD
))
1748 if (!blk_get_queue(q
))
1751 if (current
->throttle_queue
)
1752 blk_put_queue(current
->throttle_queue
);
1753 current
->throttle_queue
= q
;
1755 current
->use_memdelay
= use_memdelay
;
1756 set_notify_resume(current
);
1760 * blkcg_add_delay - add delay to this blkg
1761 * @blkg: blkg of interest
1762 * @now: the current time in nanoseconds
1763 * @delta: how many nanoseconds of delay to add
1765 * Charge @delta to the blkg's current delay accumulation. This is used to
1766 * throttle tasks if an IO controller thinks we need more throttling.
1768 void blkcg_add_delay(struct blkcg_gq
*blkg
, u64 now
, u64 delta
)
1770 blkcg_scale_delay(blkg
, now
);
1771 atomic64_add(delta
, &blkg
->delay_nsec
);
1774 static int __init
blkcg_init(void)
1776 blkcg_punt_bio_wq
= alloc_workqueue("blkcg_punt_bio",
1777 WQ_MEM_RECLAIM
| WQ_FREEZABLE
|
1778 WQ_UNBOUND
| WQ_SYSFS
, 0);
1779 if (!blkcg_punt_bio_wq
)
1783 subsys_initcall(blkcg_init
);
1785 module_param(blkcg_debug_stats
, bool, 0644);
1786 MODULE_PARM_DESC(blkcg_debug_stats
, "True if you want debug stats, false if not");