263 lines
6.4 KiB
C
263 lines
6.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Block rq-qos policy for assigning an I/O priority class to requests.
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*
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* Using an rq-qos policy for assigning I/O priority class has two advantages
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* over using the ioprio_set() system call:
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*
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* - This policy is cgroup based so it has all the advantages of cgroups.
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* - While ioprio_set() does not affect page cache writeback I/O, this rq-qos
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* controller affects page cache writeback I/O for filesystems that support
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* assiociating a cgroup with writeback I/O. See also
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* Documentation/admin-guide/cgroup-v2.rst.
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*/
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#include <linux/blk-cgroup.h>
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#include <linux/blk-mq.h>
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#include <linux/blk_types.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include "blk-ioprio.h"
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#include "blk-rq-qos.h"
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/**
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* enum prio_policy - I/O priority class policy.
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* @POLICY_NO_CHANGE: (default) do not modify the I/O priority class.
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* @POLICY_NONE_TO_RT: modify IOPRIO_CLASS_NONE into IOPRIO_CLASS_RT.
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* @POLICY_RESTRICT_TO_BE: modify IOPRIO_CLASS_NONE and IOPRIO_CLASS_RT into
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* IOPRIO_CLASS_BE.
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* @POLICY_ALL_TO_IDLE: change the I/O priority class into IOPRIO_CLASS_IDLE.
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*
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* See also <linux/ioprio.h>.
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*/
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enum prio_policy {
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POLICY_NO_CHANGE = 0,
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POLICY_NONE_TO_RT = 1,
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POLICY_RESTRICT_TO_BE = 2,
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POLICY_ALL_TO_IDLE = 3,
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};
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static const char *policy_name[] = {
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[POLICY_NO_CHANGE] = "no-change",
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[POLICY_NONE_TO_RT] = "none-to-rt",
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[POLICY_RESTRICT_TO_BE] = "restrict-to-be",
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[POLICY_ALL_TO_IDLE] = "idle",
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};
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static struct blkcg_policy ioprio_policy;
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/**
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* struct ioprio_blkg - Per (cgroup, request queue) data.
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* @pd: blkg_policy_data structure.
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*/
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struct ioprio_blkg {
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struct blkg_policy_data pd;
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};
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/**
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* struct ioprio_blkcg - Per cgroup data.
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* @cpd: blkcg_policy_data structure.
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* @prio_policy: One of the IOPRIO_CLASS_* values. See also <linux/ioprio.h>.
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*/
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struct ioprio_blkcg {
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struct blkcg_policy_data cpd;
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enum prio_policy prio_policy;
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};
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static inline struct ioprio_blkg *pd_to_ioprio(struct blkg_policy_data *pd)
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{
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return pd ? container_of(pd, struct ioprio_blkg, pd) : NULL;
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}
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static struct ioprio_blkcg *blkcg_to_ioprio_blkcg(struct blkcg *blkcg)
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{
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return container_of(blkcg_to_cpd(blkcg, &ioprio_policy),
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struct ioprio_blkcg, cpd);
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}
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static struct ioprio_blkcg *
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ioprio_blkcg_from_css(struct cgroup_subsys_state *css)
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{
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return blkcg_to_ioprio_blkcg(css_to_blkcg(css));
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}
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static struct ioprio_blkcg *ioprio_blkcg_from_bio(struct bio *bio)
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{
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struct blkg_policy_data *pd = blkg_to_pd(bio->bi_blkg, &ioprio_policy);
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if (!pd)
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return NULL;
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return blkcg_to_ioprio_blkcg(pd->blkg->blkcg);
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}
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static int ioprio_show_prio_policy(struct seq_file *sf, void *v)
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{
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struct ioprio_blkcg *blkcg = ioprio_blkcg_from_css(seq_css(sf));
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seq_printf(sf, "%s\n", policy_name[blkcg->prio_policy]);
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return 0;
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}
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static ssize_t ioprio_set_prio_policy(struct kernfs_open_file *of, char *buf,
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size_t nbytes, loff_t off)
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{
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struct ioprio_blkcg *blkcg = ioprio_blkcg_from_css(of_css(of));
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int ret;
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if (off != 0)
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return -EIO;
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/* kernfs_fop_write_iter() terminates 'buf' with '\0'. */
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ret = sysfs_match_string(policy_name, buf);
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if (ret < 0)
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return ret;
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blkcg->prio_policy = ret;
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return nbytes;
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}
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static struct blkg_policy_data *
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ioprio_alloc_pd(gfp_t gfp, struct request_queue *q, struct blkcg *blkcg)
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{
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struct ioprio_blkg *ioprio_blkg;
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ioprio_blkg = kzalloc(sizeof(*ioprio_blkg), gfp);
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if (!ioprio_blkg)
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return NULL;
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return &ioprio_blkg->pd;
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}
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static void ioprio_free_pd(struct blkg_policy_data *pd)
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{
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struct ioprio_blkg *ioprio_blkg = pd_to_ioprio(pd);
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kfree(ioprio_blkg);
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}
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static struct blkcg_policy_data *ioprio_alloc_cpd(gfp_t gfp)
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{
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struct ioprio_blkcg *blkcg;
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blkcg = kzalloc(sizeof(*blkcg), gfp);
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if (!blkcg)
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return NULL;
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blkcg->prio_policy = POLICY_NO_CHANGE;
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return &blkcg->cpd;
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}
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static void ioprio_free_cpd(struct blkcg_policy_data *cpd)
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{
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struct ioprio_blkcg *blkcg = container_of(cpd, typeof(*blkcg), cpd);
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kfree(blkcg);
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}
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#define IOPRIO_ATTRS \
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{ \
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.name = "prio.class", \
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.seq_show = ioprio_show_prio_policy, \
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.write = ioprio_set_prio_policy, \
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}, \
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{ } /* sentinel */
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/* cgroup v2 attributes */
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static struct cftype ioprio_files[] = {
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IOPRIO_ATTRS
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};
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/* cgroup v1 attributes */
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static struct cftype ioprio_legacy_files[] = {
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IOPRIO_ATTRS
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};
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static struct blkcg_policy ioprio_policy = {
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.dfl_cftypes = ioprio_files,
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.legacy_cftypes = ioprio_legacy_files,
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.cpd_alloc_fn = ioprio_alloc_cpd,
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.cpd_free_fn = ioprio_free_cpd,
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.pd_alloc_fn = ioprio_alloc_pd,
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.pd_free_fn = ioprio_free_pd,
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};
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struct blk_ioprio {
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struct rq_qos rqos;
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};
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static void blkcg_ioprio_track(struct rq_qos *rqos, struct request *rq,
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struct bio *bio)
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{
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struct ioprio_blkcg *blkcg = ioprio_blkcg_from_bio(bio);
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/*
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* Except for IOPRIO_CLASS_NONE, higher I/O priority numbers
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* correspond to a lower priority. Hence, the max_t() below selects
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* the lower priority of bi_ioprio and the cgroup I/O priority class.
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* If the cgroup policy has been set to POLICY_NO_CHANGE == 0, the
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* bio I/O priority is not modified. If the bio I/O priority equals
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* IOPRIO_CLASS_NONE, the cgroup I/O priority is assigned to the bio.
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*/
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bio->bi_ioprio = max_t(u16, bio->bi_ioprio,
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IOPRIO_PRIO_VALUE(blkcg->prio_policy, 0));
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}
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static void blkcg_ioprio_exit(struct rq_qos *rqos)
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{
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struct blk_ioprio *blkioprio_blkg =
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container_of(rqos, typeof(*blkioprio_blkg), rqos);
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blkcg_deactivate_policy(rqos->q, &ioprio_policy);
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kfree(blkioprio_blkg);
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}
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static struct rq_qos_ops blkcg_ioprio_ops = {
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.track = blkcg_ioprio_track,
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.exit = blkcg_ioprio_exit,
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};
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int blk_ioprio_init(struct request_queue *q)
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{
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struct blk_ioprio *blkioprio_blkg;
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struct rq_qos *rqos;
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int ret;
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blkioprio_blkg = kzalloc(sizeof(*blkioprio_blkg), GFP_KERNEL);
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if (!blkioprio_blkg)
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return -ENOMEM;
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ret = blkcg_activate_policy(q, &ioprio_policy);
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if (ret) {
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kfree(blkioprio_blkg);
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return ret;
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}
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rqos = &blkioprio_blkg->rqos;
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rqos->id = RQ_QOS_IOPRIO;
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rqos->ops = &blkcg_ioprio_ops;
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rqos->q = q;
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/*
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* Registering the rq-qos policy after activating the blk-cgroup
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* policy guarantees that ioprio_blkcg_from_bio(bio) != NULL in the
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* rq-qos callbacks.
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*/
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rq_qos_add(q, rqos);
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return 0;
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}
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static int __init ioprio_init(void)
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{
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return blkcg_policy_register(&ioprio_policy);
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}
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static void __exit ioprio_exit(void)
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{
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blkcg_policy_unregister(&ioprio_policy);
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}
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module_init(ioprio_init);
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module_exit(ioprio_exit);
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