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-cgroup.h>
16 #include <linux/blk-mq.h>
17 #include <linux/blk_types.h>
18 #include <linux/kernel.h>
19 #include <linux/module.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_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
29 * @POLICY_ALL_TO_IDLE: change the I/O priority class into IOPRIO_CLASS_IDLE.
31 * See also <linux/ioprio.h>.
35 POLICY_NONE_TO_RT
= 1,
36 POLICY_RESTRICT_TO_BE
= 2,
37 POLICY_ALL_TO_IDLE
= 3,
40 static 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",
47 static struct blkcg_policy ioprio_policy
;
50 * struct ioprio_blkg - Per (cgroup, request queue) data.
51 * @pd: blkg_policy_data structure.
54 struct blkg_policy_data pd
;
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>.
63 struct blkcg_policy_data cpd
;
64 enum prio_policy prio_policy
;
67 static inline struct ioprio_blkg
*pd_to_ioprio(struct blkg_policy_data
*pd
)
69 return pd
? container_of(pd
, struct ioprio_blkg
, pd
) : NULL
;
72 static struct ioprio_blkcg
*blkcg_to_ioprio_blkcg(struct blkcg
*blkcg
)
74 return container_of(blkcg_to_cpd(blkcg
, &ioprio_policy
),
75 struct ioprio_blkcg
, cpd
);
78 static struct ioprio_blkcg
*
79 ioprio_blkcg_from_css(struct cgroup_subsys_state
*css
)
81 return blkcg_to_ioprio_blkcg(css_to_blkcg(css
));
84 static struct ioprio_blkcg
*ioprio_blkcg_from_bio(struct bio
*bio
)
86 struct blkg_policy_data
*pd
= blkg_to_pd(bio
->bi_blkg
, &ioprio_policy
);
91 return blkcg_to_ioprio_blkcg(pd
->blkg
->blkcg
);
94 static int ioprio_show_prio_policy(struct seq_file
*sf
, void *v
)
96 struct ioprio_blkcg
*blkcg
= ioprio_blkcg_from_css(seq_css(sf
));
98 seq_printf(sf
, "%s\n", policy_name
[blkcg
->prio_policy
]);
102 static ssize_t
ioprio_set_prio_policy(struct kernfs_open_file
*of
, char *buf
,
103 size_t nbytes
, loff_t off
)
105 struct ioprio_blkcg
*blkcg
= ioprio_blkcg_from_css(of_css(of
));
110 /* kernfs_fop_write_iter() terminates 'buf' with '\0'. */
111 ret
= sysfs_match_string(policy_name
, buf
);
114 blkcg
->prio_policy
= ret
;
119 static struct blkg_policy_data
*
120 ioprio_alloc_pd(gfp_t gfp
, struct request_queue
*q
, struct blkcg
*blkcg
)
122 struct ioprio_blkg
*ioprio_blkg
;
124 ioprio_blkg
= kzalloc(sizeof(*ioprio_blkg
), gfp
);
128 return &ioprio_blkg
->pd
;
131 static void ioprio_free_pd(struct blkg_policy_data
*pd
)
133 struct ioprio_blkg
*ioprio_blkg
= pd_to_ioprio(pd
);
138 static struct blkcg_policy_data
*ioprio_alloc_cpd(gfp_t gfp
)
140 struct ioprio_blkcg
*blkcg
;
142 blkcg
= kzalloc(sizeof(*blkcg
), gfp
);
145 blkcg
->prio_policy
= POLICY_NO_CHANGE
;
149 static void ioprio_free_cpd(struct blkcg_policy_data
*cpd
)
151 struct ioprio_blkcg
*blkcg
= container_of(cpd
, typeof(*blkcg
), cpd
);
156 #define IOPRIO_ATTRS \
158 .name = "prio.class", \
159 .seq_show = ioprio_show_prio_policy, \
160 .write = ioprio_set_prio_policy, \
164 /* cgroup v2 attributes */
165 static struct cftype ioprio_files
[] = {
169 /* cgroup v1 attributes */
170 static struct cftype ioprio_legacy_files
[] = {
174 static struct blkcg_policy ioprio_policy
= {
175 .dfl_cftypes
= ioprio_files
,
176 .legacy_cftypes
= ioprio_legacy_files
,
178 .cpd_alloc_fn
= ioprio_alloc_cpd
,
179 .cpd_free_fn
= ioprio_free_cpd
,
181 .pd_alloc_fn
= ioprio_alloc_pd
,
182 .pd_free_fn
= ioprio_free_pd
,
189 static void blkcg_ioprio_track(struct rq_qos
*rqos
, struct request
*rq
,
192 struct ioprio_blkcg
*blkcg
= ioprio_blkcg_from_bio(bio
);
195 * Except for IOPRIO_CLASS_NONE, higher I/O priority numbers
196 * correspond to a lower priority. Hence, the max_t() below selects
197 * the lower priority of bi_ioprio and the cgroup I/O priority class.
198 * If the cgroup policy has been set to POLICY_NO_CHANGE == 0, the
199 * bio I/O priority is not modified. If the bio I/O priority equals
200 * IOPRIO_CLASS_NONE, the cgroup I/O priority is assigned to the bio.
202 bio
->bi_ioprio
= max_t(u16
, bio
->bi_ioprio
,
203 IOPRIO_PRIO_VALUE(blkcg
->prio_policy
, 0));
206 static void blkcg_ioprio_exit(struct rq_qos
*rqos
)
208 struct blk_ioprio
*blkioprio_blkg
=
209 container_of(rqos
, typeof(*blkioprio_blkg
), rqos
);
211 blkcg_deactivate_policy(rqos
->q
, &ioprio_policy
);
212 kfree(blkioprio_blkg
);
215 static struct rq_qos_ops blkcg_ioprio_ops
= {
216 .track
= blkcg_ioprio_track
,
217 .exit
= blkcg_ioprio_exit
,
220 int blk_ioprio_init(struct request_queue
*q
)
222 struct blk_ioprio
*blkioprio_blkg
;
226 blkioprio_blkg
= kzalloc(sizeof(*blkioprio_blkg
), GFP_KERNEL
);
230 ret
= blkcg_activate_policy(q
, &ioprio_policy
);
232 kfree(blkioprio_blkg
);
236 rqos
= &blkioprio_blkg
->rqos
;
237 rqos
->id
= RQ_QOS_IOPRIO
;
238 rqos
->ops
= &blkcg_ioprio_ops
;
242 * Registering the rq-qos policy after activating the blk-cgroup
243 * policy guarantees that ioprio_blkcg_from_bio(bio) != NULL in the
251 static int __init
ioprio_init(void)
253 return blkcg_policy_register(&ioprio_policy
);
256 static void __exit
ioprio_exit(void)
258 blkcg_policy_unregister(&ioprio_policy
);
261 module_init(ioprio_init
);
262 module_exit(ioprio_exit
);