Introduce an rq-qos policy that assigns an I/O priority to requests based
on blk-cgroup configuration settings. This policy has the following
advantages over 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.
Cc: Damien Le Moal <damien.lemoal@xxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
Cc: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Cc: Himanshu Madhani <himanshu.madhani@xxxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
Documentation/admin-guide/cgroup-v2.rst | 26 +++
block/Kconfig | 9 +
block/Makefile | 1 +
block/blk-cgroup.c | 5 +
block/blk-ioprio.c | 236 ++++++++++++++++++++++++
block/blk-ioprio.h | 19 ++
block/blk-rq-qos.c | 2 +
block/blk-rq-qos.h | 1 +
8 files changed, 299 insertions(+)
create mode 100644 block/blk-ioprio.c
create mode 100644 block/blk-ioprio.h
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index b1e81aa8598a..cf8c8073b474 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -56,6 +56,7 @@ v1 is available under :ref:`Documentation/admin-guide/cgroup-v1/index.rst <cgrou
5-3-3. IO Latency
5-3-3-1. How IO Latency Throttling Works
5-3-3-2. IO Latency Interface Files
+ 5-3-4. IO Priority
5-4. PID
5-4-1. PID Interface Files
5-5. Cpuset
@@ -1866,6 +1867,31 @@ IO Latency Interface Files
duration of time between evaluation events. Windows only elapse
with IO activity. Idle periods extend the most recent window.
+IO Priority
+~~~~~~~~~~~
+
+A single attribute controls the behavior of the I/O priority cgroup policy,
+namely the blkio.prio.class attribute. The following values are accepted for
+that attribute:
+
+ 0
+ Do not modify the I/O priority class.
+
+ 1
+ For requests that do not have an I/O priority class (IOPRIO_CLASS_NONE),
+ change the I/O priority class into 1 (IOPRIO_CLASS_RT). Do not modify
+ the I/O priority class of other requests.
+
+ 2
+ For requests that do not have an I/O priority class, change the I/O
+ priority class into IOPRIO_CLASS_BE. For requests that have the
+ priority class RT, change it into BE (2). Do not modify
+ the I/O priority class of requests that have priority 3 (IDLE).
+
+ 3
+ Change the I/O priority class of all requests into 3 (IDLE),
+ the lowest I/O priority class.
+
PID
---
diff --git a/block/Kconfig b/block/Kconfig
index 6685578b2a20..319816058298 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -162,6 +162,15 @@ config BLK_CGROUP_IOCOST
distributes IO capacity between different groups based on
their share of the overall weight distribution.
+config BLK_CGROUP_IOPRIO
+ bool "Cgroup I/O controller for assigning I/O priority"
+ depends on BLK_CGROUP
+ help
+ Enable the .prio interface for assigning an I/O priority to requests.
+ The I/O priority affects the order in which an I/O scheduler and block
+ devices process requests. Only some I/O schedulers and some block
+ devices support I/O priorities.
+
config BLK_DEBUG_FS
bool "Block layer debugging information in debugfs"
default y
diff --git a/block/Makefile b/block/Makefile
index 8d841f5f986f..af3d044abaf1 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_BLK_DEV_BSGLIB) += bsg-lib.o
obj-$(CONFIG_BLK_CGROUP) += blk-cgroup.o
obj-$(CONFIG_BLK_CGROUP_RWSTAT) += blk-cgroup-rwstat.o
obj-$(CONFIG_BLK_DEV_THROTTLING) += blk-throttle.o
+obj-$(CONFIG_BLK_CGROUP_IOPRIO) += blk-ioprio.o
obj-$(CONFIG_BLK_CGROUP_IOLATENCY) += blk-iolatency.o
obj-$(CONFIG_BLK_CGROUP_IOCOST) += blk-iocost.o
obj-$(CONFIG_MQ_IOSCHED_DEADLINE) += mq-deadline.o
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 3b0f6efaa2b6..7b06a5fa3cac 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -31,6 +31,7 @@
#include <linux/tracehook.h>
#include <linux/psi.h>
#include "blk.h"
+#include "blk-ioprio.h"
/*
* blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation.
@@ -1187,6 +1188,10 @@ int blkcg_init_queue(struct request_queue *q)
if (ret)
goto err_destroy_all;
+ ret = blk_ioprio_init(q);
+ if (ret)
+ goto err_destroy_all;
+
ret = blk_throtl_init(q);
if (ret)
goto err_destroy_all;
diff --git a/block/blk-ioprio.c b/block/blk-ioprio.c
new file mode 100644
index 000000000000..d7292cdef67d
--- /dev/null
+++ b/block/blk-ioprio.c
@@ -0,0 +1,236 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Block rq-qos policy for assigning an I/O priority to requests.
+ *
+ * Using an rq-qos policy for assigning I/O priority 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-cgroup.h>
+#include <linux/blk-mq.h>
+#include <linux/blk_types.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include "blk-ioprio.h"
+#include "blk-rq-qos.h"
+
+/*
+ * The accepted I/O priority values are 0..IOPRIO_CLASS_MAX(3). 0 (default)
+ * means do not modify the I/O priority. Values 1..3 are used to restrict the
+ * I/O priority for a cgroup to the specified priority. See also
+ * <linux/ioprio.h>.
+ */
+#define IOPRIO_CLASS_MAX IOPRIO_CLASS_IDLE
+
+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_class: One of the IOPRIO_CLASS_* values. See also <linux/ioprio.h>.
+ */
+struct ioprio_blkcg {
+ struct blkcg_policy_data cpd;
+ u8 prio_class;
+};
+
+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 *
+ioprio_blkcg_from_css(struct cgroup_subsys_state *css)
+{
+ struct blkcg *blkcg = css_to_blkcg(css);
+ struct blkcg_policy_data *cpd = blkcg_to_cpd(blkcg, &ioprio_policy);
+
+ return container_of(cpd, struct ioprio_blkcg, cpd);
+}
+
+static struct ioprio_blkcg *ioprio_blkcg_from_bio(struct bio *bio)
+{
+ struct blkg_policy_data *pd;
+
+ pd = blkg_to_pd(bio->bi_blkg, &ioprio_policy);
+ if (!pd)
+ return NULL;
+
+ return container_of(blkcg_to_cpd(pd->blkg->blkcg, &ioprio_policy),
+ struct ioprio_blkcg, cpd);
+}
+
+static u64 ioprio_show_prio_class(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ struct ioprio_blkcg *blkcg = ioprio_blkcg_from_css(css);
+
+ return blkcg->prio_class;
+}
+
+static int ioprio_set_prio_class(struct cgroup_subsys_state *css,
+ struct cftype *cft, u64 val)
+{
+ struct ioprio_blkcg *blkcg = ioprio_blkcg_from_css(css);
+
+ if (val > IOPRIO_CLASS_MAX)
+ return -EINVAL;
+
+ blkcg->prio_class = val;
+ return 0;
+}
+
+static struct blkg_policy_data *ioprio_alloc_pd(gfp_t gfp,
+ struct request_queue *q,
+ struct blkcg *blkcg)
+{
+ 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_class = IOPRIO_CLASS_NONE;
+ 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", \
+ .read_u64 = ioprio_show_prio_class, \
+ .write_u64 = ioprio_set_prio_class, \
+ }, \
+ { } /* 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,
+};
+
+struct blk_ioprio {
+ struct rq_qos rqos;
+};
+
+static void blkcg_ioprio_track(struct rq_qos *rqos, struct request *rq,
+ struct bio *bio)
+{
+ struct ioprio_blkcg *blkcg = ioprio_blkcg_from_bio(bio);
+
+ /*
+ * 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 cgroup priority has been set to IOPRIO_CLASS_NONE == 0, the
+ * bio I/O priority is not modified. If the bio I/O priority equals
+ * IOPRIO_CLASS_NONE, the cgroup I/O priority is assigned to the bio.
+ */
+ bio->bi_ioprio = max_t(u16, bio->bi_ioprio,
+ IOPRIO_PRIO_VALUE(blkcg->prio_class, 0));
+}
+
+static void blkcg_ioprio_exit(struct rq_qos *rqos)
+{
+ struct blk_ioprio *blkioprio_blkg =
+ container_of(rqos, typeof(*blkioprio_blkg), rqos);
+
+ blkcg_deactivate_policy(rqos->q, &ioprio_policy);
+ kfree(blkioprio_blkg);
+}
+
+static struct rq_qos_ops blkcg_ioprio_ops = {
+ .track = blkcg_ioprio_track,
+ .exit = blkcg_ioprio_exit,
+};
+
+int blk_ioprio_init(struct request_queue *q)
+{
+ struct blk_ioprio *blkioprio_blkg;
+ struct rq_qos *rqos;
+ int ret;
+
+ blkioprio_blkg = kzalloc(sizeof(*blkioprio_blkg), GFP_KERNEL);
+ if (!blkioprio_blkg)
+ return -ENOMEM;
+
+ ret = blkcg_activate_policy(q, &ioprio_policy);
+ if (ret) {
+ kfree(blkioprio_blkg);
+ return ret;
+ }
+
+ rqos = &blkioprio_blkg->rqos;
+ rqos->id = RQ_QOS_IOPRIO;
+ rqos->ops = &blkcg_ioprio_ops;
+ rqos->q = q;
+
+ rq_qos_add(q, rqos);
+
+ return 0;
+}
+
+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);
diff --git a/block/blk-ioprio.h b/block/blk-ioprio.h
new file mode 100644
index 000000000000..a7785c2f1aea
--- /dev/null
+++ b/block/blk-ioprio.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _BLK_IOPRIO_H_
+#define _BLK_IOPRIO_H_
+
+#include <linux/kconfig.h>
+
+struct request_queue;
+
+#ifdef CONFIG_BLK_CGROUP_IOPRIO
+int blk_ioprio_init(struct request_queue *q);
+#else
+static inline int blk_ioprio_init(struct request_queue *q)
+{
+ return 0;
+}
+#endif
+
+#endif /* _BLK_IOPRIO_H_ */
diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c
index 61dccf584c68..3a5400b11af7 100644
--- a/block/blk-rq-qos.c
+++ b/block/blk-rq-qos.c
@@ -11,6 +11,8 @@ const char *rq_qos_id_to_name(enum rq_qos_id id)
return "latency";
case RQ_QOS_COST:
return "cost";
+ case RQ_QOS_IOPRIO:
+ return "ioprio";
}
return "unknown";
}
diff --git a/block/blk-rq-qos.h b/block/blk-rq-qos.h
index 6b5f9ae69883..1d4c6e951aa6 100644
--- a/block/blk-rq-qos.h
+++ b/block/blk-rq-qos.h
@@ -16,6 +16,7 @@ enum rq_qos_id {
RQ_QOS_WBT,
RQ_QOS_LATENCY,
RQ_QOS_COST,
+ RQ_QOS_IOPRIO,
};
struct rq_wait {
