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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Block rq-qos policy for assigning an I/O priority class to requests.
4 *
5 * Using an rq-qos policy for assigning I/O priority class has two advantages
6 * over using the ioprio_set() system call:
7 *
8 * - This policy is cgroup based so it has all the advantages of cgroups.
9 * - While ioprio_set() does not affect page cache writeback I/O, this rq-qos
10 * controller affects page cache writeback I/O for filesystems that support
11 * assiociating a cgroup with writeback I/O. See also
12 * Documentation/admin-guide/cgroup-v2.rst.
13 */
14
15#include <linux/blk-mq.h>
16#include <linux/blk_types.h>
17#include <linux/kernel.h>
18#include <linux/module.h>
19#include "blk-cgroup.h"
20#include "blk-ioprio.h"
21#include "blk-rq-qos.h"
22
23/**
24 * enum prio_policy - I/O priority class policy.
25 * @POLICY_NO_CHANGE: (default) do not modify the I/O priority class.
26 * @POLICY_NONE_TO_RT: modify IOPRIO_CLASS_NONE into IOPRIO_CLASS_RT.
27 * @POLICY_RESTRICT_TO_BE: modify IOPRIO_CLASS_NONE and IOPRIO_CLASS_RT into
28 * IOPRIO_CLASS_BE.
29 * @POLICY_ALL_TO_IDLE: change the I/O priority class into IOPRIO_CLASS_IDLE.
30 *
31 * See also <linux/ioprio.h>.
32 */
33enum prio_policy {
34 POLICY_NO_CHANGE = 0,
35 POLICY_NONE_TO_RT = 1,
36 POLICY_RESTRICT_TO_BE = 2,
37 POLICY_ALL_TO_IDLE = 3,
38};
39
40static const char *policy_name[] = {
41 [POLICY_NO_CHANGE] = "no-change",
42 [POLICY_NONE_TO_RT] = "none-to-rt",
43 [POLICY_RESTRICT_TO_BE] = "restrict-to-be",
44 [POLICY_ALL_TO_IDLE] = "idle",
45};
46
47static struct blkcg_policy ioprio_policy;
48
49/**
50 * struct ioprio_blkg - Per (cgroup, request queue) data.
51 * @pd: blkg_policy_data structure.
52 */
53struct ioprio_blkg {
54 struct blkg_policy_data pd;
55};
56
57/**
58 * struct ioprio_blkcg - Per cgroup data.
59 * @cpd: blkcg_policy_data structure.
60 * @prio_policy: One of the IOPRIO_CLASS_* values. See also <linux/ioprio.h>.
61 */
62struct ioprio_blkcg {
63 struct blkcg_policy_data cpd;
64 enum prio_policy prio_policy;
65};
66
67static inline struct ioprio_blkg *pd_to_ioprio(struct blkg_policy_data *pd)
68{
69 return pd ? container_of(pd, struct ioprio_blkg, pd) : NULL;
70}
71
72static struct ioprio_blkcg *blkcg_to_ioprio_blkcg(struct blkcg *blkcg)
73{
74 return container_of(blkcg_to_cpd(blkcg, &ioprio_policy),
75 struct ioprio_blkcg, cpd);
76}
77
78static struct ioprio_blkcg *
79ioprio_blkcg_from_css(struct cgroup_subsys_state *css)
80{
81 return blkcg_to_ioprio_blkcg(css_to_blkcg(css));
82}
83
84static struct ioprio_blkcg *ioprio_blkcg_from_bio(struct bio *bio)
85{
86 struct blkg_policy_data *pd = blkg_to_pd(bio->bi_blkg, &ioprio_policy);
87
88 if (!pd)
89 return NULL;
90
91 return blkcg_to_ioprio_blkcg(pd->blkg->blkcg);
92}
93
94static int ioprio_show_prio_policy(struct seq_file *sf, void *v)
95{
96 struct ioprio_blkcg *blkcg = ioprio_blkcg_from_css(seq_css(sf));
97
98 seq_printf(sf, "%s\n", policy_name[blkcg->prio_policy]);
99 return 0;
100}
101
102static ssize_t ioprio_set_prio_policy(struct kernfs_open_file *of, char *buf,
103 size_t nbytes, loff_t off)
104{
105 struct ioprio_blkcg *blkcg = ioprio_blkcg_from_css(of_css(of));
106 int ret;
107
108 if (off != 0)
109 return -EIO;
110 /* kernfs_fop_write_iter() terminates 'buf' with '\0'. */
111 ret = sysfs_match_string(policy_name, buf);
112 if (ret < 0)
113 return ret;
114 blkcg->prio_policy = ret;
115 return nbytes;
116}
117
118static struct blkg_policy_data *
119ioprio_alloc_pd(gfp_t gfp, struct request_queue *q, struct blkcg *blkcg)
120{
121 struct ioprio_blkg *ioprio_blkg;
122
123 ioprio_blkg = kzalloc(sizeof(*ioprio_blkg), gfp);
124 if (!ioprio_blkg)
125 return NULL;
126
127 return &ioprio_blkg->pd;
128}
129
130static void ioprio_free_pd(struct blkg_policy_data *pd)
131{
132 struct ioprio_blkg *ioprio_blkg = pd_to_ioprio(pd);
133
134 kfree(ioprio_blkg);
135}
136
137static struct blkcg_policy_data *ioprio_alloc_cpd(gfp_t gfp)
138{
139 struct ioprio_blkcg *blkcg;
140
141 blkcg = kzalloc(sizeof(*blkcg), gfp);
142 if (!blkcg)
143 return NULL;
144 blkcg->prio_policy = POLICY_NO_CHANGE;
145 return &blkcg->cpd;
146}
147
148static void ioprio_free_cpd(struct blkcg_policy_data *cpd)
149{
150 struct ioprio_blkcg *blkcg = container_of(cpd, typeof(*blkcg), cpd);
151
152 kfree(blkcg);
153}
154
155#define IOPRIO_ATTRS \
156 { \
157 .name = "prio.class", \
158 .seq_show = ioprio_show_prio_policy, \
159 .write = ioprio_set_prio_policy, \
160 }, \
161 { } /* sentinel */
162
163/* cgroup v2 attributes */
164static struct cftype ioprio_files[] = {
165 IOPRIO_ATTRS
166};
167
168/* cgroup v1 attributes */
169static struct cftype ioprio_legacy_files[] = {
170 IOPRIO_ATTRS
171};
172
173static struct blkcg_policy ioprio_policy = {
174 .dfl_cftypes = ioprio_files,
175 .legacy_cftypes = ioprio_legacy_files,
176
177 .cpd_alloc_fn = ioprio_alloc_cpd,
178 .cpd_free_fn = ioprio_free_cpd,
179
180 .pd_alloc_fn = ioprio_alloc_pd,
181 .pd_free_fn = ioprio_free_pd,
182};
183
184void blkcg_set_ioprio(struct bio *bio)
185{
186 struct ioprio_blkcg *blkcg = ioprio_blkcg_from_bio(bio);
187 u16 prio;
188
189 if (!blkcg || blkcg->prio_policy == POLICY_NO_CHANGE)
190 return;
191
192 /*
193 * Except for IOPRIO_CLASS_NONE, higher I/O priority numbers
194 * correspond to a lower priority. Hence, the max_t() below selects
195 * the lower priority of bi_ioprio and the cgroup I/O priority class.
196 * If the bio I/O priority equals IOPRIO_CLASS_NONE, the cgroup I/O
197 * priority is assigned to the bio.
198 */
199 prio = max_t(u16, bio->bi_ioprio,
200 IOPRIO_PRIO_VALUE(blkcg->prio_policy, 0));
201 if (prio > bio->bi_ioprio)
202 bio->bi_ioprio = prio;
203}
204
205void blk_ioprio_exit(struct gendisk *disk)
206{
207 blkcg_deactivate_policy(disk->queue, &ioprio_policy);
208}
209
210int blk_ioprio_init(struct gendisk *disk)
211{
212 return blkcg_activate_policy(disk->queue, &ioprio_policy);
213}
214
215static int __init ioprio_init(void)
216{
217 return blkcg_policy_register(&ioprio_policy);
218}
219
220static void __exit ioprio_exit(void)
221{
222 blkcg_policy_unregister(&ioprio_policy);
223}
224
225module_init(ioprio_init);
226module_exit(ioprio_exit);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Block rq-qos policy for assigning an I/O priority class to requests.
4 *
5 * Using an rq-qos policy for assigning I/O priority class has two advantages
6 * over using the ioprio_set() system call:
7 *
8 * - This policy is cgroup based so it has all the advantages of cgroups.
9 * - While ioprio_set() does not affect page cache writeback I/O, this rq-qos
10 * controller affects page cache writeback I/O for filesystems that support
11 * assiociating a cgroup with writeback I/O. See also
12 * Documentation/admin-guide/cgroup-v2.rst.
13 */
14
15#include <linux/blk-mq.h>
16#include <linux/blk_types.h>
17#include <linux/kernel.h>
18#include <linux/module.h>
19#include "blk-cgroup.h"
20#include "blk-ioprio.h"
21#include "blk-rq-qos.h"
22
23/**
24 * enum prio_policy - I/O priority class policy.
25 * @POLICY_NO_CHANGE: (default) do not modify the I/O priority class.
26 * @POLICY_PROMOTE_TO_RT: modify no-IOPRIO_CLASS_RT to IOPRIO_CLASS_RT.
27 * @POLICY_RESTRICT_TO_BE: modify IOPRIO_CLASS_NONE and IOPRIO_CLASS_RT into
28 * IOPRIO_CLASS_BE.
29 * @POLICY_ALL_TO_IDLE: change the I/O priority class into IOPRIO_CLASS_IDLE.
30 * @POLICY_NONE_TO_RT: an alias for POLICY_PROMOTE_TO_RT.
31 *
32 * See also <linux/ioprio.h>.
33 */
34enum prio_policy {
35 POLICY_NO_CHANGE = 0,
36 POLICY_PROMOTE_TO_RT = 1,
37 POLICY_RESTRICT_TO_BE = 2,
38 POLICY_ALL_TO_IDLE = 3,
39 POLICY_NONE_TO_RT = 4,
40};
41
42static const char *policy_name[] = {
43 [POLICY_NO_CHANGE] = "no-change",
44 [POLICY_PROMOTE_TO_RT] = "promote-to-rt",
45 [POLICY_RESTRICT_TO_BE] = "restrict-to-be",
46 [POLICY_ALL_TO_IDLE] = "idle",
47 [POLICY_NONE_TO_RT] = "none-to-rt",
48};
49
50static struct blkcg_policy ioprio_policy;
51
52/**
53 * struct ioprio_blkg - Per (cgroup, request queue) data.
54 * @pd: blkg_policy_data structure.
55 */
56struct ioprio_blkg {
57 struct blkg_policy_data pd;
58};
59
60/**
61 * struct ioprio_blkcg - Per cgroup data.
62 * @cpd: blkcg_policy_data structure.
63 * @prio_policy: One of the IOPRIO_CLASS_* values. See also <linux/ioprio.h>.
64 */
65struct ioprio_blkcg {
66 struct blkcg_policy_data cpd;
67 enum prio_policy prio_policy;
68};
69
70static inline struct ioprio_blkg *pd_to_ioprio(struct blkg_policy_data *pd)
71{
72 return pd ? container_of(pd, struct ioprio_blkg, pd) : NULL;
73}
74
75static struct ioprio_blkcg *blkcg_to_ioprio_blkcg(struct blkcg *blkcg)
76{
77 return container_of(blkcg_to_cpd(blkcg, &ioprio_policy),
78 struct ioprio_blkcg, cpd);
79}
80
81static struct ioprio_blkcg *
82ioprio_blkcg_from_css(struct cgroup_subsys_state *css)
83{
84 return blkcg_to_ioprio_blkcg(css_to_blkcg(css));
85}
86
87static struct ioprio_blkcg *ioprio_blkcg_from_bio(struct bio *bio)
88{
89 struct blkg_policy_data *pd = blkg_to_pd(bio->bi_blkg, &ioprio_policy);
90
91 if (!pd)
92 return NULL;
93
94 return blkcg_to_ioprio_blkcg(pd->blkg->blkcg);
95}
96
97static int ioprio_show_prio_policy(struct seq_file *sf, void *v)
98{
99 struct ioprio_blkcg *blkcg = ioprio_blkcg_from_css(seq_css(sf));
100
101 seq_printf(sf, "%s\n", policy_name[blkcg->prio_policy]);
102 return 0;
103}
104
105static ssize_t ioprio_set_prio_policy(struct kernfs_open_file *of, char *buf,
106 size_t nbytes, loff_t off)
107{
108 struct ioprio_blkcg *blkcg = ioprio_blkcg_from_css(of_css(of));
109 int ret;
110
111 if (off != 0)
112 return -EIO;
113 /* kernfs_fop_write_iter() terminates 'buf' with '\0'. */
114 ret = sysfs_match_string(policy_name, buf);
115 if (ret < 0)
116 return ret;
117 blkcg->prio_policy = ret;
118 return nbytes;
119}
120
121static struct blkg_policy_data *
122ioprio_alloc_pd(struct gendisk *disk, struct blkcg *blkcg, gfp_t gfp)
123{
124 struct ioprio_blkg *ioprio_blkg;
125
126 ioprio_blkg = kzalloc(sizeof(*ioprio_blkg), gfp);
127 if (!ioprio_blkg)
128 return NULL;
129
130 return &ioprio_blkg->pd;
131}
132
133static void ioprio_free_pd(struct blkg_policy_data *pd)
134{
135 struct ioprio_blkg *ioprio_blkg = pd_to_ioprio(pd);
136
137 kfree(ioprio_blkg);
138}
139
140static struct blkcg_policy_data *ioprio_alloc_cpd(gfp_t gfp)
141{
142 struct ioprio_blkcg *blkcg;
143
144 blkcg = kzalloc(sizeof(*blkcg), gfp);
145 if (!blkcg)
146 return NULL;
147 blkcg->prio_policy = POLICY_NO_CHANGE;
148 return &blkcg->cpd;
149}
150
151static void ioprio_free_cpd(struct blkcg_policy_data *cpd)
152{
153 struct ioprio_blkcg *blkcg = container_of(cpd, typeof(*blkcg), cpd);
154
155 kfree(blkcg);
156}
157
158#define IOPRIO_ATTRS \
159 { \
160 .name = "prio.class", \
161 .seq_show = ioprio_show_prio_policy, \
162 .write = ioprio_set_prio_policy, \
163 }, \
164 { } /* sentinel */
165
166/* cgroup v2 attributes */
167static struct cftype ioprio_files[] = {
168 IOPRIO_ATTRS
169};
170
171/* cgroup v1 attributes */
172static struct cftype ioprio_legacy_files[] = {
173 IOPRIO_ATTRS
174};
175
176static struct blkcg_policy ioprio_policy = {
177 .dfl_cftypes = ioprio_files,
178 .legacy_cftypes = ioprio_legacy_files,
179
180 .cpd_alloc_fn = ioprio_alloc_cpd,
181 .cpd_free_fn = ioprio_free_cpd,
182
183 .pd_alloc_fn = ioprio_alloc_pd,
184 .pd_free_fn = ioprio_free_pd,
185};
186
187void blkcg_set_ioprio(struct bio *bio)
188{
189 struct ioprio_blkcg *blkcg = ioprio_blkcg_from_bio(bio);
190 u16 prio;
191
192 if (!blkcg || blkcg->prio_policy == POLICY_NO_CHANGE)
193 return;
194
195 if (blkcg->prio_policy == POLICY_PROMOTE_TO_RT ||
196 blkcg->prio_policy == POLICY_NONE_TO_RT) {
197 /*
198 * For RT threads, the default priority level is 4 because
199 * task_nice is 0. By promoting non-RT io-priority to RT-class
200 * and default level 4, those requests that are already
201 * RT-class but need a higher io-priority can use ioprio_set()
202 * to achieve this.
203 */
204 if (IOPRIO_PRIO_CLASS(bio->bi_ioprio) != IOPRIO_CLASS_RT)
205 bio->bi_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_RT, 4);
206 return;
207 }
208
209 /*
210 * Except for IOPRIO_CLASS_NONE, higher I/O priority numbers
211 * correspond to a lower priority. Hence, the max_t() below selects
212 * the lower priority of bi_ioprio and the cgroup I/O priority class.
213 * If the bio I/O priority equals IOPRIO_CLASS_NONE, the cgroup I/O
214 * priority is assigned to the bio.
215 */
216 prio = max_t(u16, bio->bi_ioprio,
217 IOPRIO_PRIO_VALUE(blkcg->prio_policy, 0));
218 if (prio > bio->bi_ioprio)
219 bio->bi_ioprio = prio;
220}
221
222void blk_ioprio_exit(struct gendisk *disk)
223{
224 blkcg_deactivate_policy(disk, &ioprio_policy);
225}
226
227int blk_ioprio_init(struct gendisk *disk)
228{
229 return blkcg_activate_policy(disk, &ioprio_policy);
230}
231
232static int __init ioprio_init(void)
233{
234 return blkcg_policy_register(&ioprio_policy);
235}
236
237static void __exit ioprio_exit(void)
238{
239 blkcg_policy_unregister(&ioprio_policy);
240}
241
242module_init(ioprio_init);
243module_exit(ioprio_exit);