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-rw-r--r--block/blk-ioprio.c243
1 files changed, 243 insertions, 0 deletions
diff --git a/block/blk-ioprio.c b/block/blk-ioprio.c
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+++ b/block/blk-ioprio.c
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+// 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);