// SPDX-License-Identifier: GPL-2.0 /* * Block rq-qos policy for assigning an I/O priority class to requests. * * Using an rq-qos policy for assigning I/O priority class has two advantages * over using the ioprio_set() system call: * * - This policy is cgroup based so it has all the advantages of cgroups. * - While ioprio_set() does not affect page cache writeback I/O, this rq-qos * controller affects page cache writeback I/O for filesystems that support * assiociating a cgroup with writeback I/O. See also * Documentation/admin-guide/cgroup-v2.rst. */ #include <linux/blk-mq.h> #include <linux/blk_types.h> #include <linux/kernel.h> #include <linux/module.h> #include "blk-cgroup.h" #include "blk-ioprio.h" #include "blk-rq-qos.h" /** * enum prio_policy - I/O priority class policy. * @POLICY_NO_CHANGE: (default) do not modify the I/O priority class. * @POLICY_PROMOTE_TO_RT: modify no-IOPRIO_CLASS_RT to IOPRIO_CLASS_RT. * @POLICY_RESTRICT_TO_BE: modify IOPRIO_CLASS_NONE and IOPRIO_CLASS_RT into * IOPRIO_CLASS_BE. * @POLICY_ALL_TO_IDLE: change the I/O priority class into IOPRIO_CLASS_IDLE. * @POLICY_NONE_TO_RT: an alias for POLICY_PROMOTE_TO_RT. * * See also <linux/ioprio.h>. */ enum prio_policy { POLICY_NO_CHANGE = 0, POLICY_PROMOTE_TO_RT = 1, POLICY_RESTRICT_TO_BE = 2, POLICY_ALL_TO_IDLE = 3, POLICY_NONE_TO_RT = 4, }; static const char *policy_name[] = { [POLICY_NO_CHANGE] = "no-change", [POLICY_PROMOTE_TO_RT] = "promote-to-rt", [POLICY_RESTRICT_TO_BE] = "restrict-to-be", [POLICY_ALL_TO_IDLE] = "idle", [POLICY_NONE_TO_RT] = "none-to-rt", }; static struct blkcg_policy ioprio_policy; /** * struct ioprio_blkg - Per (cgroup, request queue) data. * @pd: blkg_policy_data structure. */ struct ioprio_blkg { struct blkg_policy_data pd; }; /** * struct ioprio_blkcg - Per cgroup data. * @cpd: blkcg_policy_data structure. * @prio_policy: One of the IOPRIO_CLASS_* values. See also <linux/ioprio.h>. */ struct ioprio_blkcg { struct blkcg_policy_data cpd; enum prio_policy prio_policy; }; static inline struct ioprio_blkg *pd_to_ioprio(struct blkg_policy_data *pd) { return pd ? container_of(pd, struct ioprio_blkg, pd) : NULL; } static struct ioprio_blkcg *blkcg_to_ioprio_blkcg(struct blkcg *blkcg) { return container_of(blkcg_to_cpd(blkcg, &ioprio_policy), struct ioprio_blkcg, cpd); } static struct ioprio_blkcg * ioprio_blkcg_from_css(struct cgroup_subsys_state *css) { return blkcg_to_ioprio_blkcg(css_to_blkcg(css)); } static struct ioprio_blkcg *ioprio_blkcg_from_bio(struct bio *bio) { struct blkg_policy_data *pd = blkg_to_pd(bio->bi_blkg, &ioprio_policy); if (!pd) return NULL; return blkcg_to_ioprio_blkcg(pd->blkg->blkcg); } static int ioprio_show_prio_policy(struct seq_file *sf, void *v) { struct ioprio_blkcg *blkcg = ioprio_blkcg_from_css(seq_css(sf)); seq_printf(sf, "%s\n", policy_name[blkcg->prio_policy]); return 0; } static ssize_t ioprio_set_prio_policy(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) { struct ioprio_blkcg *blkcg = ioprio_blkcg_from_css(of_css(of)); int ret; if (off != 0) return -EIO; /* kernfs_fop_write_iter() terminates 'buf' with '\0'. */ ret = sysfs_match_string(policy_name, buf); if (ret < 0) return ret; blkcg->prio_policy = ret; return nbytes; } static struct blkg_policy_data * ioprio_alloc_pd(struct gendisk *disk, struct blkcg *blkcg, gfp_t gfp) { struct ioprio_blkg *ioprio_blkg; ioprio_blkg = kzalloc(sizeof(*ioprio_blkg), gfp); if (!ioprio_blkg) return NULL; return &ioprio_blkg->pd; } static void ioprio_free_pd(struct blkg_policy_data *pd) { struct ioprio_blkg *ioprio_blkg = pd_to_ioprio(pd); kfree(ioprio_blkg); } static struct blkcg_policy_data *ioprio_alloc_cpd(gfp_t gfp) { struct ioprio_blkcg *blkcg; blkcg = kzalloc(sizeof(*blkcg), gfp); if (!blkcg) return NULL; blkcg->prio_policy = POLICY_NO_CHANGE; return &blkcg->cpd; } static void ioprio_free_cpd(struct blkcg_policy_data *cpd) { struct ioprio_blkcg *blkcg = container_of(cpd, typeof(*blkcg), cpd); kfree(blkcg); } #define IOPRIO_ATTRS \ { \ .name = "prio.class", \ .seq_show = ioprio_show_prio_policy, \ .write = ioprio_set_prio_policy, \ }, \ { } /* sentinel */ /* cgroup v2 attributes */ static struct cftype ioprio_files[] = { IOPRIO_ATTRS }; /* cgroup v1 attributes */ static struct cftype ioprio_legacy_files[] = { IOPRIO_ATTRS }; static struct blkcg_policy ioprio_policy = { .dfl_cftypes = ioprio_files, .legacy_cftypes = ioprio_legacy_files, .cpd_alloc_fn = ioprio_alloc_cpd, .cpd_free_fn = ioprio_free_cpd, .pd_alloc_fn = ioprio_alloc_pd, .pd_free_fn = ioprio_free_pd, }; void blkcg_set_ioprio(struct bio *bio) { struct ioprio_blkcg *blkcg = ioprio_blkcg_from_bio(bio); u16 prio; if (!blkcg || blkcg->prio_policy == POLICY_NO_CHANGE) return; if (blkcg->prio_policy == POLICY_PROMOTE_TO_RT || blkcg->prio_policy == POLICY_NONE_TO_RT) { /* * For RT threads, the default priority level is 4 because * task_nice is 0. By promoting non-RT io-priority to RT-class * and default level 4, those requests that are already * RT-class but need a higher io-priority can use ioprio_set() * to achieve this. */ if (IOPRIO_PRIO_CLASS(bio->bi_ioprio) != IOPRIO_CLASS_RT) bio->bi_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_RT, 4); return; } /* * Except for IOPRIO_CLASS_NONE, higher I/O priority numbers * correspond to a lower priority. Hence, the max_t() below selects * the lower priority of bi_ioprio and the cgroup I/O priority class. * If the bio I/O priority equals IOPRIO_CLASS_NONE, the cgroup I/O * priority is assigned to the bio. */ prio = max_t(u16, bio->bi_ioprio, IOPRIO_PRIO_VALUE(blkcg->prio_policy, 0)); if (prio > bio->bi_ioprio) bio->bi_ioprio = prio; } void blk_ioprio_exit(struct gendisk *disk) { blkcg_deactivate_policy(disk, &ioprio_policy); } int blk_ioprio_init(struct gendisk *disk) { return blkcg_activate_policy(disk, &ioprio_policy); } static int __init ioprio_init(void) { return blkcg_policy_register(&ioprio_policy); } static void __exit ioprio_exit(void) { blkcg_policy_unregister(&ioprio_policy); } module_init(ioprio_init); module_exit(ioprio_exit);