1 // SPDX-License-Identifier: GPL-2.0
3 * Block rq-qos policy for assigning an I/O priority class to requests.
5 * Using an rq-qos policy for assigning I/O priority class has two advantages
6 * over using the ioprio_set() system call:
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.
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"
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
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.
32 * See also <linux/ioprio.h>.
36 POLICY_PROMOTE_TO_RT
= 1,
37 POLICY_RESTRICT_TO_BE
= 2,
38 POLICY_ALL_TO_IDLE
= 3,
39 POLICY_NONE_TO_RT
= 4,
42 static 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",
50 static struct blkcg_policy ioprio_policy
;
53 * struct ioprio_blkg - Per (cgroup, request queue) data.
54 * @pd: blkg_policy_data structure.
57 struct blkg_policy_data pd
;
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>.
66 struct blkcg_policy_data cpd
;
67 enum prio_policy prio_policy
;
70 static inline struct ioprio_blkg
*pd_to_ioprio(struct blkg_policy_data
*pd
)
72 return pd
? container_of(pd
, struct ioprio_blkg
, pd
) : NULL
;
75 static struct ioprio_blkcg
*blkcg_to_ioprio_blkcg(struct blkcg
*blkcg
)
77 return container_of(blkcg_to_cpd(blkcg
, &ioprio_policy
),
78 struct ioprio_blkcg
, cpd
);
81 static struct ioprio_blkcg
*
82 ioprio_blkcg_from_css(struct cgroup_subsys_state
*css
)
84 return blkcg_to_ioprio_blkcg(css_to_blkcg(css
));
87 static struct ioprio_blkcg
*ioprio_blkcg_from_bio(struct bio
*bio
)
89 struct blkg_policy_data
*pd
= blkg_to_pd(bio
->bi_blkg
, &ioprio_policy
);
94 return blkcg_to_ioprio_blkcg(pd
->blkg
->blkcg
);
97 static int ioprio_show_prio_policy(struct seq_file
*sf
, void *v
)
99 struct ioprio_blkcg
*blkcg
= ioprio_blkcg_from_css(seq_css(sf
));
101 seq_printf(sf
, "%s\n", policy_name
[blkcg
->prio_policy
]);
105 static ssize_t
ioprio_set_prio_policy(struct kernfs_open_file
*of
, char *buf
,
106 size_t nbytes
, loff_t off
)
108 struct ioprio_blkcg
*blkcg
= ioprio_blkcg_from_css(of_css(of
));
113 /* kernfs_fop_write_iter() terminates 'buf' with '\0'. */
114 ret
= sysfs_match_string(policy_name
, buf
);
117 blkcg
->prio_policy
= ret
;
121 static struct blkg_policy_data
*
122 ioprio_alloc_pd(struct gendisk
*disk
, struct blkcg
*blkcg
, gfp_t gfp
)
124 struct ioprio_blkg
*ioprio_blkg
;
126 ioprio_blkg
= kzalloc(sizeof(*ioprio_blkg
), gfp
);
130 return &ioprio_blkg
->pd
;
133 static void ioprio_free_pd(struct blkg_policy_data
*pd
)
135 struct ioprio_blkg
*ioprio_blkg
= pd_to_ioprio(pd
);
140 static struct blkcg_policy_data
*ioprio_alloc_cpd(gfp_t gfp
)
142 struct ioprio_blkcg
*blkcg
;
144 blkcg
= kzalloc(sizeof(*blkcg
), gfp
);
147 blkcg
->prio_policy
= POLICY_NO_CHANGE
;
151 static void ioprio_free_cpd(struct blkcg_policy_data
*cpd
)
153 struct ioprio_blkcg
*blkcg
= container_of(cpd
, typeof(*blkcg
), cpd
);
158 #define IOPRIO_ATTRS \
160 .name = "prio.class", \
161 .seq_show = ioprio_show_prio_policy, \
162 .write = ioprio_set_prio_policy, \
166 /* cgroup v2 attributes */
167 static struct cftype ioprio_files
[] = {
171 /* cgroup v1 attributes */
172 static struct cftype ioprio_legacy_files
[] = {
176 static struct blkcg_policy ioprio_policy
= {
177 .dfl_cftypes
= ioprio_files
,
178 .legacy_cftypes
= ioprio_legacy_files
,
180 .cpd_alloc_fn
= ioprio_alloc_cpd
,
181 .cpd_free_fn
= ioprio_free_cpd
,
183 .pd_alloc_fn
= ioprio_alloc_pd
,
184 .pd_free_fn
= ioprio_free_pd
,
187 void blkcg_set_ioprio(struct bio
*bio
)
189 struct ioprio_blkcg
*blkcg
= ioprio_blkcg_from_bio(bio
);
192 if (!blkcg
|| blkcg
->prio_policy
== POLICY_NO_CHANGE
)
195 if (blkcg
->prio_policy
== POLICY_PROMOTE_TO_RT
||
196 blkcg
->prio_policy
== POLICY_NONE_TO_RT
) {
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()
204 if (IOPRIO_PRIO_CLASS(bio
->bi_ioprio
) != IOPRIO_CLASS_RT
)
205 bio
->bi_ioprio
= IOPRIO_PRIO_VALUE(IOPRIO_CLASS_RT
, 4);
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.
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
;
222 void blk_ioprio_exit(struct gendisk
*disk
)
224 blkcg_deactivate_policy(disk
, &ioprio_policy
);
227 int blk_ioprio_init(struct gendisk
*disk
)
229 return blkcg_activate_policy(disk
, &ioprio_policy
);
232 static int __init
ioprio_init(void)
234 return blkcg_policy_register(&ioprio_policy
);
237 static void __exit
ioprio_exit(void)
239 blkcg_policy_unregister(&ioprio_policy
);
242 module_init(ioprio_init
);
243 module_exit(ioprio_exit
);