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1// SPDX-License-Identifier: GPL-2.02/*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 advantages6 * 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-qos10 * controller affects page cache writeback I/O for filesystems that support11 * assiociating a cgroup with writeback I/O. See also12 * 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 into28 * 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_blkcg - Per cgroup data.54 * @cpd: blkcg_policy_data structure.55 * @prio_policy: One of the IOPRIO_CLASS_* values. See also <linux/ioprio.h>.56 */57struct ioprio_blkcg {58 struct blkcg_policy_data cpd;59 enum prio_policy prio_policy;60};61 62static struct ioprio_blkcg *blkcg_to_ioprio_blkcg(struct blkcg *blkcg)63{64 return container_of(blkcg_to_cpd(blkcg, &ioprio_policy),65 struct ioprio_blkcg, cpd);66}67 68static struct ioprio_blkcg *69ioprio_blkcg_from_css(struct cgroup_subsys_state *css)70{71 return blkcg_to_ioprio_blkcg(css_to_blkcg(css));72}73 74static int ioprio_show_prio_policy(struct seq_file *sf, void *v)75{76 struct ioprio_blkcg *blkcg = ioprio_blkcg_from_css(seq_css(sf));77 78 seq_printf(sf, "%s\n", policy_name[blkcg->prio_policy]);79 return 0;80}81 82static ssize_t ioprio_set_prio_policy(struct kernfs_open_file *of, char *buf,83 size_t nbytes, loff_t off)84{85 struct ioprio_blkcg *blkcg = ioprio_blkcg_from_css(of_css(of));86 int ret;87 88 if (off != 0)89 return -EIO;90 /* kernfs_fop_write_iter() terminates 'buf' with '\0'. */91 ret = sysfs_match_string(policy_name, buf);92 if (ret < 0)93 return ret;94 blkcg->prio_policy = ret;95 return nbytes;96}97 98static struct blkcg_policy_data *ioprio_alloc_cpd(gfp_t gfp)99{100 struct ioprio_blkcg *blkcg;101 102 blkcg = kzalloc(sizeof(*blkcg), gfp);103 if (!blkcg)104 return NULL;105 blkcg->prio_policy = POLICY_NO_CHANGE;106 return &blkcg->cpd;107}108 109static void ioprio_free_cpd(struct blkcg_policy_data *cpd)110{111 struct ioprio_blkcg *blkcg = container_of(cpd, typeof(*blkcg), cpd);112 113 kfree(blkcg);114}115 116#define IOPRIO_ATTRS \117 { \118 .name = "prio.class", \119 .seq_show = ioprio_show_prio_policy, \120 .write = ioprio_set_prio_policy, \121 }, \122 { } /* sentinel */123 124/* cgroup v2 attributes */125static struct cftype ioprio_files[] = {126 IOPRIO_ATTRS127};128 129/* cgroup v1 attributes */130static struct cftype ioprio_legacy_files[] = {131 IOPRIO_ATTRS132};133 134static struct blkcg_policy ioprio_policy = {135 .dfl_cftypes = ioprio_files,136 .legacy_cftypes = ioprio_legacy_files,137 138 .cpd_alloc_fn = ioprio_alloc_cpd,139 .cpd_free_fn = ioprio_free_cpd,140};141 142void blkcg_set_ioprio(struct bio *bio)143{144 struct ioprio_blkcg *blkcg = blkcg_to_ioprio_blkcg(bio->bi_blkg->blkcg);145 u16 prio;146 147 if (!blkcg || blkcg->prio_policy == POLICY_NO_CHANGE)148 return;149 150 if (blkcg->prio_policy == POLICY_PROMOTE_TO_RT ||151 blkcg->prio_policy == POLICY_NONE_TO_RT) {152 /*153 * For RT threads, the default priority level is 4 because154 * task_nice is 0. By promoting non-RT io-priority to RT-class155 * and default level 4, those requests that are already156 * RT-class but need a higher io-priority can use ioprio_set()157 * to achieve this.158 */159 if (IOPRIO_PRIO_CLASS(bio->bi_ioprio) != IOPRIO_CLASS_RT)160 bio->bi_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_RT, 4);161 return;162 }163 164 /*165 * Except for IOPRIO_CLASS_NONE, higher I/O priority numbers166 * correspond to a lower priority. Hence, the max_t() below selects167 * the lower priority of bi_ioprio and the cgroup I/O priority class.168 * If the bio I/O priority equals IOPRIO_CLASS_NONE, the cgroup I/O169 * priority is assigned to the bio.170 */171 prio = max_t(u16, bio->bi_ioprio,172 IOPRIO_PRIO_VALUE(blkcg->prio_policy, 0));173 if (prio > bio->bi_ioprio)174 bio->bi_ioprio = prio;175}176 177static int __init ioprio_init(void)178{179 return blkcg_policy_register(&ioprio_policy);180}181 182static void __exit ioprio_exit(void)183{184 blkcg_policy_unregister(&ioprio_policy);185}186 187module_init(ioprio_init);188module_exit(ioprio_exit);189