summaryrefslogtreecommitdiff
path: root/include/linux/blk-cgroup.h
blob: a57ebe2f00abd81cf0c94958b1f7a107b600d195 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _BLK_CGROUP_H
#define _BLK_CGROUP_H
/*
 * Common Block IO controller cgroup interface
 *
 * Based on ideas and code from CFQ, CFS and BFQ:
 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
 *
 * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
 *		      Paolo Valente <paolo.valente@unimore.it>
 *
 * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
 * 	              Nauman Rafique <nauman@google.com>
 */

#include <linux/cgroup.h>
#include <linux/percpu.h>
#include <linux/percpu_counter.h>
#include <linux/u64_stats_sync.h>
#include <linux/seq_file.h>
#include <linux/radix-tree.h>
#include <linux/blkdev.h>
#include <linux/atomic.h>
#include <linux/kthread.h>
#include <linux/fs.h>

/* percpu_counter batch for blkg_[rw]stats, per-cpu drift doesn't matter */
#define BLKG_STAT_CPU_BATCH	(INT_MAX / 2)

/* Max limits for throttle policy */
#define THROTL_IOPS_MAX		UINT_MAX

#ifdef CONFIG_BLK_CGROUP

enum blkg_iostat_type {
	BLKG_IOSTAT_READ,
	BLKG_IOSTAT_WRITE,
	BLKG_IOSTAT_DISCARD,

	BLKG_IOSTAT_NR,
};

struct blkcg_gq;

struct blkcg {
	struct cgroup_subsys_state	css;
	spinlock_t			lock;
	refcount_t			online_pin;

	struct radix_tree_root		blkg_tree;
	struct blkcg_gq	__rcu		*blkg_hint;
	struct hlist_head		blkg_list;

	struct blkcg_policy_data	*cpd[BLKCG_MAX_POLS];

	struct list_head		all_blkcgs_node;
#ifdef CONFIG_CGROUP_WRITEBACK
	struct list_head		cgwb_list;
#endif
};

struct blkg_iostat {
	u64				bytes[BLKG_IOSTAT_NR];
	u64				ios[BLKG_IOSTAT_NR];
};

struct blkg_iostat_set {
	struct u64_stats_sync		sync;
	struct blkg_iostat		cur;
	struct blkg_iostat		last;
};

/*
 * A blkcg_gq (blkg) is association between a block cgroup (blkcg) and a
 * request_queue (q).  This is used by blkcg policies which need to track
 * information per blkcg - q pair.
 *
 * There can be multiple active blkcg policies and each blkg:policy pair is
 * represented by a blkg_policy_data which is allocated and freed by each
 * policy's pd_alloc/free_fn() methods.  A policy can allocate private data
 * area by allocating larger data structure which embeds blkg_policy_data
 * at the beginning.
 */
struct blkg_policy_data {
	/* the blkg and policy id this per-policy data belongs to */
	struct blkcg_gq			*blkg;
	int				plid;
};

/*
 * Policies that need to keep per-blkcg data which is independent from any
 * request_queue associated to it should implement cpd_alloc/free_fn()
 * methods.  A policy can allocate private data area by allocating larger
 * data structure which embeds blkcg_policy_data at the beginning.
 * cpd_init() is invoked to let each policy handle per-blkcg data.
 */
struct blkcg_policy_data {
	/* the blkcg and policy id this per-policy data belongs to */
	struct blkcg			*blkcg;
	int				plid;
};

/* association between a blk cgroup and a request queue */
struct blkcg_gq {
	/* Pointer to the associated request_queue */
	struct request_queue		*q;
	struct list_head		q_node;
	struct hlist_node		blkcg_node;
	struct blkcg			*blkcg;

	/*
	 * Each blkg gets congested separately and the congestion state is
	 * propagated to the matching bdi_writeback_congested.
	 */
	struct bdi_writeback_congested	*wb_congested;

	/* all non-root blkcg_gq's are guaranteed to have access to parent */
	struct blkcg_gq			*parent;

	/* reference count */
	struct percpu_ref		refcnt;

	/* is this blkg online? protected by both blkcg and q locks */
	bool				online;

	struct blkg_iostat_set __percpu	*iostat_cpu;
	struct blkg_iostat_set		iostat;

	struct blkg_policy_data		*pd[BLKCG_MAX_POLS];

	spinlock_t			async_bio_lock;
	struct bio_list			async_bios;
	struct work_struct		async_bio_work;

	atomic_t			use_delay;
	atomic64_t			delay_nsec;
	atomic64_t			delay_start;
	u64				last_delay;
	int				last_use;

	struct rcu_head			rcu_head;
};

typedef struct blkcg_policy_data *(blkcg_pol_alloc_cpd_fn)(gfp_t gfp);
typedef void (blkcg_pol_init_cpd_fn)(struct blkcg_policy_data *cpd);
typedef void (blkcg_pol_free_cpd_fn)(struct blkcg_policy_data *cpd);
typedef void (blkcg_pol_bind_cpd_fn)(struct blkcg_policy_data *cpd);
typedef struct blkg_policy_data *(blkcg_pol_alloc_pd_fn)(gfp_t gfp,
				struct request_queue *q, struct blkcg *blkcg);
typedef void (blkcg_pol_init_pd_fn)(struct blkg_policy_data *pd);
typedef void (blkcg_pol_online_pd_fn)(struct blkg_policy_data *pd);
typedef void (blkcg_pol_offline_pd_fn)(struct blkg_policy_data *pd);
typedef void (blkcg_pol_free_pd_fn)(struct blkg_policy_data *pd);
typedef void (blkcg_pol_reset_pd_stats_fn)(struct blkg_policy_data *pd);
typedef size_t (blkcg_pol_stat_pd_fn)(struct blkg_policy_data *pd, char *buf,
				      size_t size);

struct blkcg_policy {
	int				plid;
	/* cgroup files for the policy */
	struct cftype			*dfl_cftypes;
	struct cftype			*legacy_cftypes;

	/* operations */
	blkcg_pol_alloc_cpd_fn		*cpd_alloc_fn;
	blkcg_pol_init_cpd_fn		*cpd_init_fn;
	blkcg_pol_free_cpd_fn		*cpd_free_fn;
	blkcg_pol_bind_cpd_fn		*cpd_bind_fn;

	blkcg_pol_alloc_pd_fn		*pd_alloc_fn;
	blkcg_pol_init_pd_fn		*pd_init_fn;
	blkcg_pol_online_pd_fn		*pd_online_fn;
	blkcg_pol_offline_pd_fn		*pd_offline_fn;
	blkcg_pol_free_pd_fn		*pd_free_fn;
	blkcg_pol_reset_pd_stats_fn	*pd_reset_stats_fn;
	blkcg_pol_stat_pd_fn		*pd_stat_fn;
};

extern struct blkcg blkcg_root;
extern struct cgroup_subsys_state * const blkcg_root_css;
extern bool blkcg_debug_stats;

struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
				      struct request_queue *q, bool update_hint);
struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
				      struct request_queue *q);
struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
				    struct request_queue *q);
int blkcg_init_queue(struct request_queue *q);
void blkcg_exit_queue(struct request_queue *q);

/* Blkio controller policy registration */
int blkcg_policy_register(struct blkcg_policy *pol);
void blkcg_policy_unregister(struct blkcg_policy *pol);
int blkcg_activate_policy(struct request_queue *q,
			  const struct blkcg_policy *pol);
void blkcg_deactivate_policy(struct request_queue *q,
			     const struct blkcg_policy *pol);

const char *blkg_dev_name(struct blkcg_gq *blkg);
void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
		       u64 (*prfill)(struct seq_file *,
				     struct blkg_policy_data *, int),
		       const struct blkcg_policy *pol, int data,
		       bool show_total);
u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v);

struct blkg_conf_ctx {
	struct gendisk			*disk;
	struct blkcg_gq			*blkg;
	char				*body;
};

struct gendisk *blkcg_conf_get_disk(char **inputp);
int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
		   char *input, struct blkg_conf_ctx *ctx);
void blkg_conf_finish(struct blkg_conf_ctx *ctx);

/**
 * blkcg_css - find the current css
 *
 * Find the css associated with either the kthread or the current task.
 * This may return a dying css, so it is up to the caller to use tryget logic
 * to confirm it is alive and well.
 */
static inline struct cgroup_subsys_state *blkcg_css(void)
{
	struct cgroup_subsys_state *css;

	css = kthread_blkcg();
	if (css)
		return css;
	return task_css(current, io_cgrp_id);
}

static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
{
	return css ? container_of(css, struct blkcg, css) : NULL;
}

/**
 * __bio_blkcg - internal, inconsistent version to get blkcg
 *
 * DO NOT USE.
 * This function is inconsistent and consequently is dangerous to use.  The
 * first part of the function returns a blkcg where a reference is owned by the
 * bio.  This means it does not need to be rcu protected as it cannot go away
 * with the bio owning a reference to it.  However, the latter potentially gets
 * it from task_css().  This can race against task migration and the cgroup
 * dying.  It is also semantically different as it must be called rcu protected
 * and is susceptible to failure when trying to get a reference to it.
 * Therefore, it is not ok to assume that *_get() will always succeed on the
 * blkcg returned here.
 */
static inline struct blkcg *__bio_blkcg(struct bio *bio)
{
	if (bio && bio->bi_blkg)
		return bio->bi_blkg->blkcg;
	return css_to_blkcg(blkcg_css());
}

/**
 * bio_blkcg - grab the blkcg associated with a bio
 * @bio: target bio
 *
 * This returns the blkcg associated with a bio, %NULL if not associated.
 * Callers are expected to either handle %NULL or know association has been
 * done prior to calling this.
 */
static inline struct blkcg *bio_blkcg(struct bio *bio)
{
	if (bio && bio->bi_blkg)
		return bio->bi_blkg->blkcg;
	return NULL;
}

static inline bool blk_cgroup_congested(void)
{
	struct cgroup_subsys_state *css;
	bool ret = false;

	rcu_read_lock();
	css = kthread_blkcg();
	if (!css)
		css = task_css(current, io_cgrp_id);
	while (css) {
		if (atomic_read(&css->cgroup->congestion_count)) {
			ret = true;
			break;
		}
		css = css->parent;
	}
	rcu_read_unlock();
	return ret;
}

/**
 * bio_issue_as_root_blkg - see if this bio needs to be issued as root blkg
 * @return: true if this bio needs to be submitted with the root blkg context.
 *
 * In order to avoid priority inversions we sometimes need to issue a bio as if
 * it were attached to the root blkg, and then backcharge to the actual owning
 * blkg.  The idea is we do bio_blkcg() to look up the actual context for the
 * bio and attach the appropriate blkg to the bio.  Then we call this helper and
 * if it is true run with the root blkg for that queue and then do any
 * backcharging to the originating cgroup once the io is complete.
 */
static inline bool bio_issue_as_root_blkg(struct bio *bio)
{
	return (bio->bi_opf & (REQ_META | REQ_SWAP)) != 0;
}

/**
 * blkcg_parent - get the parent of a blkcg
 * @blkcg: blkcg of interest
 *
 * Return the parent blkcg of @blkcg.  Can be called anytime.
 */
static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
{
	return css_to_blkcg(blkcg->css.parent);
}

/**
 * __blkg_lookup - internal version of blkg_lookup()
 * @blkcg: blkcg of interest
 * @q: request_queue of interest
 * @update_hint: whether to update lookup hint with the result or not
 *
 * This is internal version and shouldn't be used by policy
 * implementations.  Looks up blkgs for the @blkcg - @q pair regardless of
 * @q's bypass state.  If @update_hint is %true, the caller should be
 * holding @q->queue_lock and lookup hint is updated on success.
 */
static inline struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg,
					     struct request_queue *q,
					     bool update_hint)
{
	struct blkcg_gq *blkg;

	if (blkcg == &blkcg_root)
		return q->root_blkg;

	blkg = rcu_dereference(blkcg->blkg_hint);
	if (blkg && blkg->q == q)
		return blkg;

	return blkg_lookup_slowpath(blkcg, q, update_hint);
}

/**
 * blkg_lookup - lookup blkg for the specified blkcg - q pair
 * @blkcg: blkcg of interest
 * @q: request_queue of interest
 *
 * Lookup blkg for the @blkcg - @q pair.  This function should be called
 * under RCU read lock.
 */
static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg,
					   struct request_queue *q)
{
	WARN_ON_ONCE(!rcu_read_lock_held());
	return __blkg_lookup(blkcg, q, false);
}

/**
 * blk_queue_root_blkg - return blkg for the (blkcg_root, @q) pair
 * @q: request_queue of interest
 *
 * Lookup blkg for @q at the root level. See also blkg_lookup().
 */
static inline struct blkcg_gq *blk_queue_root_blkg(struct request_queue *q)
{
	return q->root_blkg;
}

/**
 * blkg_to_pdata - get policy private data
 * @blkg: blkg of interest
 * @pol: policy of interest
 *
 * Return pointer to private data associated with the @blkg-@pol pair.
 */
static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
						  struct blkcg_policy *pol)
{
	return blkg ? blkg->pd[pol->plid] : NULL;
}

static inline struct blkcg_policy_data *blkcg_to_cpd(struct blkcg *blkcg,
						     struct blkcg_policy *pol)
{
	return blkcg ? blkcg->cpd[pol->plid] : NULL;
}

/**
 * pdata_to_blkg - get blkg associated with policy private data
 * @pd: policy private data of interest
 *
 * @pd is policy private data.  Determine the blkg it's associated with.
 */
static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd)
{
	return pd ? pd->blkg : NULL;
}

static inline struct blkcg *cpd_to_blkcg(struct blkcg_policy_data *cpd)
{
	return cpd ? cpd->blkcg : NULL;
}

extern void blkcg_destroy_blkgs(struct blkcg *blkcg);

/**
 * blkcg_pin_online - pin online state
 * @blkcg: blkcg of interest
 *
 * While pinned, a blkcg is kept online.  This is primarily used to
 * impedance-match blkg and cgwb lifetimes so that blkg doesn't go offline
 * while an associated cgwb is still active.
 */
static inline void blkcg_pin_online(struct blkcg *blkcg)
{
	refcount_inc(&blkcg->online_pin);
}

/**
 * blkcg_unpin_online - unpin online state
 * @blkcg: blkcg of interest
 *
 * This is primarily used to impedance-match blkg and cgwb lifetimes so
 * that blkg doesn't go offline while an associated cgwb is still active.
 * When this count goes to zero, all active cgwbs have finished so the
 * blkcg can continue destruction by calling blkcg_destroy_blkgs().
 */
static inline void blkcg_unpin_online(struct blkcg *blkcg)
{
	do {
		if (!refcount_dec_and_test(&blkcg->online_pin))
			break;
		blkcg_destroy_blkgs(blkcg);
		blkcg = blkcg_parent(blkcg);
	} while (blkcg);
}

/**
 * blkg_path - format cgroup path of blkg
 * @blkg: blkg of interest
 * @buf: target buffer
 * @buflen: target buffer length
 *
 * Format the path of the cgroup of @blkg into @buf.
 */
static inline int blkg_path(struct blkcg_gq *blkg, char *buf, int buflen)
{
	return cgroup_path(blkg->blkcg->css.cgroup, buf, buflen);
}

/**
 * blkg_get - get a blkg reference
 * @blkg: blkg to get
 *
 * The caller should be holding an existing reference.
 */
static inline void blkg_get(struct blkcg_gq *blkg)
{
	percpu_ref_get(&blkg->refcnt);
}

/**
 * blkg_tryget - try and get a blkg reference
 * @blkg: blkg to get
 *
 * This is for use when doing an RCU lookup of the blkg.  We may be in the midst
 * of freeing this blkg, so we can only use it if the refcnt is not zero.
 */
static inline bool blkg_tryget(struct blkcg_gq *blkg)
{
	return blkg && percpu_ref_tryget(&blkg->refcnt);
}

/**
 * blkg_tryget_closest - try and get a blkg ref on the closet blkg
 * @blkg: blkg to get
 *
 * This needs to be called rcu protected.  As the failure mode here is to walk
 * up the blkg tree, this ensure that the blkg->parent pointers are always
 * valid.  This returns the blkg that it ended up taking a reference on or %NULL
 * if no reference was taken.
 */
static inline struct blkcg_gq *blkg_tryget_closest(struct blkcg_gq *blkg)
{
	struct blkcg_gq *ret_blkg = NULL;

	WARN_ON_ONCE(!rcu_read_lock_held());

	while (blkg) {
		if (blkg_tryget(blkg)) {
			ret_blkg = blkg;
			break;
		}
		blkg = blkg->parent;
	}

	return ret_blkg;
}

/**
 * blkg_put - put a blkg reference
 * @blkg: blkg to put
 */
static inline void blkg_put(struct blkcg_gq *blkg)
{
	percpu_ref_put(&blkg->refcnt);
}

/**
 * blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants
 * @d_blkg: loop cursor pointing to the current descendant
 * @pos_css: used for iteration
 * @p_blkg: target blkg to walk descendants of
 *
 * Walk @c_blkg through the descendants of @p_blkg.  Must be used with RCU
 * read locked.  If called under either blkcg or queue lock, the iteration
 * is guaranteed to include all and only online blkgs.  The caller may
 * update @pos_css by calling css_rightmost_descendant() to skip subtree.
 * @p_blkg is included in the iteration and the first node to be visited.
 */
#define blkg_for_each_descendant_pre(d_blkg, pos_css, p_blkg)		\
	css_for_each_descendant_pre((pos_css), &(p_blkg)->blkcg->css)	\
		if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css),	\
					      (p_blkg)->q, false)))

/**
 * blkg_for_each_descendant_post - post-order walk of a blkg's descendants
 * @d_blkg: loop cursor pointing to the current descendant
 * @pos_css: used for iteration
 * @p_blkg: target blkg to walk descendants of
 *
 * Similar to blkg_for_each_descendant_pre() but performs post-order
 * traversal instead.  Synchronization rules are the same.  @p_blkg is
 * included in the iteration and the last node to be visited.
 */
#define blkg_for_each_descendant_post(d_blkg, pos_css, p_blkg)		\
	css_for_each_descendant_post((pos_css), &(p_blkg)->blkcg->css)	\
		if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css),	\
					      (p_blkg)->q, false)))

#ifdef CONFIG_BLK_DEV_THROTTLING
extern bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
			   struct bio *bio);
#else
static inline bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
				  struct bio *bio) { return false; }
#endif

bool __blkcg_punt_bio_submit(struct bio *bio);

static inline bool blkcg_punt_bio_submit(struct bio *bio)
{
	if (bio->bi_opf & REQ_CGROUP_PUNT)
		return __blkcg_punt_bio_submit(bio);
	else
		return false;
}

static inline void blkcg_bio_issue_init(struct bio *bio)
{
	bio_issue_init(&bio->bi_issue, bio_sectors(bio));
}

static inline bool blkcg_bio_issue_check(struct request_queue *q,
					 struct bio *bio)
{
	struct blkcg_gq *blkg;
	bool throtl = false;

	rcu_read_lock();

	if (!bio->bi_blkg) {
		char b[BDEVNAME_SIZE];

		WARN_ONCE(1,
			  "no blkg associated for bio on block-device: %s\n",
			  bio_devname(bio, b));
		bio_associate_blkg(bio);
	}

	blkg = bio->bi_blkg;

	throtl = blk_throtl_bio(q, blkg, bio);

	if (!throtl) {
		struct blkg_iostat_set *bis;
		int rwd, cpu;

		if (op_is_discard(bio->bi_opf))
			rwd = BLKG_IOSTAT_DISCARD;
		else if (op_is_write(bio->bi_opf))
			rwd = BLKG_IOSTAT_WRITE;
		else
			rwd = BLKG_IOSTAT_READ;

		cpu = get_cpu();
		bis = per_cpu_ptr(blkg->iostat_cpu, cpu);
		u64_stats_update_begin(&bis->sync);

		/*
		 * If the bio is flagged with BIO_CGROUP_ACCT it means this is a
		 * split bio and we would have already accounted for the size of
		 * the bio.
		 */
		if (!bio_flagged(bio, BIO_CGROUP_ACCT)) {
			bio_set_flag(bio, BIO_CGROUP_ACCT);
			bis->cur.bytes[rwd] += bio->bi_iter.bi_size;
		}
		bis->cur.ios[rwd]++;

		u64_stats_update_end(&bis->sync);
		if (cgroup_subsys_on_dfl(io_cgrp_subsys))
			cgroup_rstat_updated(blkg->blkcg->css.cgroup, cpu);
		put_cpu();
	}

	blkcg_bio_issue_init(bio);

	rcu_read_unlock();
	return !throtl;
}

static inline void blkcg_use_delay(struct blkcg_gq *blkg)
{
	if (WARN_ON_ONCE(atomic_read(&blkg->use_delay) < 0))
		return;
	if (atomic_add_return(1, &blkg->use_delay) == 1)
		atomic_inc(&blkg->blkcg->css.cgroup->congestion_count);
}

static inline int blkcg_unuse_delay(struct blkcg_gq *blkg)
{
	int old = atomic_read(&blkg->use_delay);

	if (WARN_ON_ONCE(old < 0))
		return 0;
	if (old == 0)
		return 0;

	/*
	 * We do this song and dance because we can race with somebody else
	 * adding or removing delay.  If we just did an atomic_dec we'd end up
	 * negative and we'd already be in trouble.  We need to subtract 1 and
	 * then check to see if we were the last delay so we can drop the
	 * congestion count on the cgroup.
	 */
	while (old) {
		int cur = atomic_cmpxchg(&blkg->use_delay, old, old - 1);
		if (cur == old)
			break;
		old = cur;
	}

	if (old == 0)
		return 0;
	if (old == 1)
		atomic_dec(&blkg->blkcg->css.cgroup->congestion_count);
	return 1;
}

/**
 * blkcg_set_delay - Enable allocator delay mechanism with the specified delay amount
 * @blkg: target blkg
 * @delay: delay duration in nsecs
 *
 * When enabled with this function, the delay is not decayed and must be
 * explicitly cleared with blkcg_clear_delay(). Must not be mixed with
 * blkcg_[un]use_delay() and blkcg_add_delay() usages.
 */
static inline void blkcg_set_delay(struct blkcg_gq *blkg, u64 delay)
{
	int old = atomic_read(&blkg->use_delay);

	/* We only want 1 person setting the congestion count for this blkg. */
	if (!old && atomic_cmpxchg(&blkg->use_delay, old, -1) == old)
		atomic_inc(&blkg->blkcg->css.cgroup->congestion_count);

	atomic64_set(&blkg->delay_nsec, delay);
}

/**
 * blkcg_clear_delay - Disable allocator delay mechanism
 * @blkg: target blkg
 *
 * Disable use_delay mechanism. See blkcg_set_delay().
 */
static inline void blkcg_clear_delay(struct blkcg_gq *blkg)
{
	int old = atomic_read(&blkg->use_delay);

	/* We only want 1 person clearing the congestion count for this blkg. */
	if (old && atomic_cmpxchg(&blkg->use_delay, old, 0) == old)
		atomic_dec(&blkg->blkcg->css.cgroup->congestion_count);
}

void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta);
void blkcg_schedule_throttle(struct request_queue *q, bool use_memdelay);
void blkcg_maybe_throttle_current(void);
#else	/* CONFIG_BLK_CGROUP */

struct blkcg {
};

struct blkg_policy_data {
};

struct blkcg_policy_data {
};

struct blkcg_gq {
};

struct blkcg_policy {
};

#define blkcg_root_css	((struct cgroup_subsys_state *)ERR_PTR(-EINVAL))

static inline void blkcg_maybe_throttle_current(void) { }
static inline bool blk_cgroup_congested(void) { return false; }

#ifdef CONFIG_BLOCK

static inline void blkcg_schedule_throttle(struct request_queue *q, bool use_memdelay) { }

static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }
static inline struct blkcg_gq *blk_queue_root_blkg(struct request_queue *q)
{ return NULL; }
static inline int blkcg_init_queue(struct request_queue *q) { return 0; }
static inline void blkcg_exit_queue(struct request_queue *q) { }
static inline int blkcg_policy_register(struct blkcg_policy *pol) { return 0; }
static inline void blkcg_policy_unregister(struct blkcg_policy *pol) { }
static inline int blkcg_activate_policy(struct request_queue *q,
					const struct blkcg_policy *pol) { return 0; }
static inline void blkcg_deactivate_policy(struct request_queue *q,
					   const struct blkcg_policy *pol) { }

static inline struct blkcg *__bio_blkcg(struct bio *bio) { return NULL; }
static inline struct blkcg *bio_blkcg(struct bio *bio) { return NULL; }

static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
						  struct blkcg_policy *pol) { return NULL; }
static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd) { return NULL; }
static inline char *blkg_path(struct blkcg_gq *blkg) { return NULL; }
static inline void blkg_get(struct blkcg_gq *blkg) { }
static inline void blkg_put(struct blkcg_gq *blkg) { }

static inline bool blkcg_punt_bio_submit(struct bio *bio) { return false; }
static inline void blkcg_bio_issue_init(struct bio *bio) { }
static inline bool blkcg_bio_issue_check(struct request_queue *q,
					 struct bio *bio) { return true; }

#define blk_queue_for_each_rl(rl, q)	\
	for ((rl) = &(q)->root_rl; (rl); (rl) = NULL)

#endif	/* CONFIG_BLOCK */
#endif	/* CONFIG_BLK_CGROUP */
#endif	/* _BLK_CGROUP_H */