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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef BLK_THROTTLE_H
3#define BLK_THROTTLE_H
4
5#include "blk-cgroup-rwstat.h"
6
7/*
8 * To implement hierarchical throttling, throtl_grps form a tree and bios
9 * are dispatched upwards level by level until they reach the top and get
10 * issued. When dispatching bios from the children and local group at each
11 * level, if the bios are dispatched into a single bio_list, there's a risk
12 * of a local or child group which can queue many bios at once filling up
13 * the list starving others.
14 *
15 * To avoid such starvation, dispatched bios are queued separately
16 * according to where they came from. When they are again dispatched to
17 * the parent, they're popped in round-robin order so that no single source
18 * hogs the dispatch window.
19 *
20 * throtl_qnode is used to keep the queued bios separated by their sources.
21 * Bios are queued to throtl_qnode which in turn is queued to
22 * throtl_service_queue and then dispatched in round-robin order.
23 *
24 * It's also used to track the reference counts on blkg's. A qnode always
25 * belongs to a throtl_grp and gets queued on itself or the parent, so
26 * incrementing the reference of the associated throtl_grp when a qnode is
27 * queued and decrementing when dequeued is enough to keep the whole blkg
28 * tree pinned while bios are in flight.
29 */
30struct throtl_qnode {
31 struct list_head node; /* service_queue->queued[] */
32 struct bio_list bios_bps; /* queued bios for bps limit */
33 struct bio_list bios_iops; /* queued bios for iops limit */
34 struct throtl_grp *tg; /* tg this qnode belongs to */
35};
36
37struct throtl_service_queue {
38 struct throtl_service_queue *parent_sq; /* the parent service_queue */
39
40 /*
41 * Bios queued directly to this service_queue or dispatched from
42 * children throtl_grp's.
43 */
44 struct list_head queued[2]; /* throtl_qnode [READ/WRITE] */
45 unsigned int nr_queued_bps[2]; /* number of queued bps bios */
46 unsigned int nr_queued_iops[2]; /* number of queued iops bios */
47
48 /*
49 * RB tree of active children throtl_grp's, which are sorted by
50 * their ->disptime.
51 */
52 struct rb_root_cached pending_tree; /* RB tree of active tgs */
53 unsigned int nr_pending; /* # queued in the tree */
54 unsigned long first_pending_disptime; /* disptime of the first tg */
55 struct timer_list pending_timer; /* fires on first_pending_disptime */
56};
57
58enum tg_state_flags {
59 THROTL_TG_PENDING = 1 << 0, /* on parent's pending tree */
60 THROTL_TG_WAS_EMPTY = 1 << 1, /* bio_lists[] became non-empty */
61 /*
62 * The sq's iops queue is empty, and a bio is about to be enqueued
63 * to the first qnode's bios_iops list.
64 */
65 THROTL_TG_IOPS_WAS_EMPTY = 1 << 2,
66 THROTL_TG_CANCELING = 1 << 3, /* starts to cancel bio */
67};
68
69struct throtl_grp {
70 /* must be the first member */
71 struct blkg_policy_data pd;
72
73 /* active throtl group service_queue member */
74 struct rb_node rb_node;
75
76 /* throtl_data this group belongs to */
77 struct throtl_data *td;
78
79 /* this group's service queue */
80 struct throtl_service_queue service_queue;
81
82 /*
83 * qnode_on_self is used when bios are directly queued to this
84 * throtl_grp so that local bios compete fairly with bios
85 * dispatched from children. qnode_on_parent is used when bios are
86 * dispatched from this throtl_grp into its parent and will compete
87 * with the sibling qnode_on_parents and the parent's
88 * qnode_on_self.
89 */
90 struct throtl_qnode qnode_on_self[2];
91 struct throtl_qnode qnode_on_parent[2];
92
93 /*
94 * Dispatch time in jiffies. This is the estimated time when group
95 * will unthrottle and is ready to dispatch more bio. It is used as
96 * key to sort active groups in service tree.
97 */
98 unsigned long disptime;
99
100 unsigned int flags;
101
102 /* are there any throtl rules between this group and td? */
103 bool has_rules_bps[2];
104 bool has_rules_iops[2];
105
106 /* bytes per second rate limits */
107 uint64_t bps[2];
108
109 /* IOPS limits */
110 unsigned int iops[2];
111
112 /*
113 * Number of bytes/bio's dispatched in current slice.
114 * When new configuration is submitted while some bios are still throttled,
115 * first calculate the carryover: the amount of bytes/IOs already waited
116 * under the previous configuration. Then, [bytes/io]_disp are represented
117 * as the negative of the carryover, and they will be used to calculate the
118 * wait time under the new configuration.
119 */
120 int64_t bytes_disp[2];
121 int io_disp[2];
122
123 /* When did we start a new slice */
124 unsigned long slice_start[2];
125 unsigned long slice_end[2];
126
127 struct blkg_rwstat stat_bytes;
128 struct blkg_rwstat stat_ios;
129};
130
131extern struct blkcg_policy blkcg_policy_throtl;
132
133static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
134{
135 return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
136}
137
138static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
139{
140 return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
141}
142
143/*
144 * Internal throttling interface
145 */
146#ifndef CONFIG_BLK_DEV_THROTTLING
147static inline void blk_throtl_exit(struct gendisk *disk) { }
148static inline bool blk_throtl_bio(struct bio *bio) { return false; }
149static inline void blk_throtl_cancel_bios(struct gendisk *disk) { }
150#else /* CONFIG_BLK_DEV_THROTTLING */
151void blk_throtl_exit(struct gendisk *disk);
152bool __blk_throtl_bio(struct bio *bio);
153void blk_throtl_cancel_bios(struct gendisk *disk);
154
155static inline bool blk_throtl_activated(struct request_queue *q)
156{
157 /*
158 * q->td guarantees that the blk-throttle module is already loaded,
159 * and the plid of blk-throttle is assigned.
160 * blkcg_policy_enabled() guarantees that the policy is activated
161 * in the request_queue.
162 */
163 return q->td != NULL && blkcg_policy_enabled(q, &blkcg_policy_throtl);
164}
165
166static inline bool blk_should_throtl(struct bio *bio)
167{
168 struct throtl_grp *tg;
169 int rw = bio_data_dir(bio);
170
171 if (!blk_throtl_activated(bio->bi_bdev->bd_queue))
172 return false;
173
174 tg = blkg_to_tg(bio->bi_blkg);
175 if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) {
176 if (!bio_flagged(bio, BIO_CGROUP_ACCT)) {
177 bio_set_flag(bio, BIO_CGROUP_ACCT);
178 blkg_rwstat_add(&tg->stat_bytes, bio->bi_opf,
179 bio->bi_iter.bi_size);
180 }
181 blkg_rwstat_add(&tg->stat_ios, bio->bi_opf, 1);
182 }
183
184 /* iops limit is always counted */
185 if (tg->has_rules_iops[rw])
186 return true;
187
188 if (tg->has_rules_bps[rw] && !bio_flagged(bio, BIO_BPS_THROTTLED))
189 return true;
190
191 return false;
192}
193
194static inline bool blk_throtl_bio(struct bio *bio)
195{
196 /*
197 * block throttling takes effect if the policy is activated
198 * in the bio's request_queue.
199 */
200 if (!blk_should_throtl(bio))
201 return false;
202
203 return __blk_throtl_bio(bio);
204}
205#endif /* CONFIG_BLK_DEV_THROTTLING */
206
207#endif