[RFC,V4,5/6] blk-ioprio: make ioprio pluggable and modular

Commit Message

Wang Jianchao Feb. 17, 2022, 3:13 a.m. UTC

Make blk-ioprio pluggable and modular. Then we can close or open
it through /sys/block/xxx/queue/qos and rmmod the module if we don't
need it which can release one blkcg policy slot. The blk-ioprio.h
is removed as we needn't to make blk_ioprio_init() external.

Signed-off-by: Wang Jianchao (Kuaishou) <[e-mail]>
---
 block/Kconfig          |  2 +-
 block/blk-cgroup.c     |  5 -----
 block/blk-ioprio.c     | 51 ++++++++++++++++++++++++++++--------------
 block/blk-ioprio.h     | 19 ----------------
 block/blk-mq-debugfs.c |  4 ----
 block/blk-rq-qos.c     |  2 +-
 block/blk-rq-qos.h     |  2 +-
 7 files changed, 37 insertions(+), 48 deletions(-)
 delete mode 100644 block/blk-ioprio.h

Comments

Christoph Hellwig Feb. 17, 2022, 8:54 a.m. UTC | #1

> +static int blk_ioprio_init(struct request_queue *q);
> +
>  static struct rq_qos_ops blkcg_ioprio_ops = {

Same ordering comment as for the last ones.

Patch

diff --git a/block/Kconfig b/block/Kconfig
index d5d4197b7ed2..9cc8e4688953 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -145,7 +145,7 @@  config BLK_CGROUP_IOCOST
 	their share of the overall weight distribution.
 
 config BLK_CGROUP_IOPRIO
-	bool "Cgroup I/O controller for assigning an I/O priority class"
+	tristate "Cgroup I/O controller for assigning an I/O priority class"
 	depends on BLK_CGROUP
 	help
 	Enable the .prio interface for assigning an I/O priority class to
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 3ae2aa557aef..f617f7ba311d 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -32,7 +32,6 @@ 
 #include <linux/psi.h>
 #include <linux/part_stat.h>
 #include "blk.h"
-#include "blk-ioprio.h"
 #include "blk-throttle.h"
 
 /*
@@ -1195,10 +1194,6 @@  int blkcg_init_queue(struct request_queue *q)
 	if (preloaded)
 		radix_tree_preload_end();
 
-	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
index 2e7f10e1c03f..1ec56f617202 100644
--- a/block/blk-ioprio.c
+++ b/block/blk-ioprio.c
@@ -17,7 +17,6 @@ 
 #include <linux/blk_types.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
-#include "blk-ioprio.h"
 #include "blk-rq-qos.h"
 
 /**
@@ -216,15 +215,24 @@  static void blkcg_ioprio_exit(struct rq_qos *rqos)
 		container_of(rqos, typeof(*blkioprio_blkg), rqos);
 
 	blkcg_deactivate_policy(rqos->q, &ioprio_policy);
+	rq_qos_deactivate(rqos);
 	kfree(blkioprio_blkg);
 }
 
+static int blk_ioprio_init(struct request_queue *q);
+
 static struct rq_qos_ops blkcg_ioprio_ops = {
+#if IS_MODULE(CONFIG_BLK_CGROUP_IOPRIO)
+	.owner	= THIS_MODULE,
+#endif
+	.flags	= RQOS_FLAG_CGRP_POL,
+	.name	= "blk-ioprio",
 	.track	= blkcg_ioprio_track,
 	.exit	= blkcg_ioprio_exit,
+	.init	= blk_ioprio_init,
 };
 
-int blk_ioprio_init(struct request_queue *q)
+static int blk_ioprio_init(struct request_queue *q)
 {
 	struct blk_ioprio *blkioprio_blkg;
 	struct rq_qos *rqos;
@@ -234,36 +242,45 @@  int blk_ioprio_init(struct request_queue *q)
 	if (!blkioprio_blkg)
 		return -ENOMEM;
 
+	/*
+	 * No need to worry ioprio_blkcg_from_css return NULL as
+	 * the queue is frozen right now.
+	 */
+	rqos = &blkioprio_blkg->rqos;
+	rq_qos_activate(q, rqos, &blkcg_ioprio_ops);
+
 	ret = blkcg_activate_policy(q, &ioprio_policy);
 	if (ret) {
+		rq_qos_deactivate(rqos);
 		kfree(blkioprio_blkg);
-		return ret;
 	}
 
-	rqos = &blkioprio_blkg->rqos;
-	rqos->id = RQ_QOS_IOPRIO;
-	rqos->ops = &blkcg_ioprio_ops;
-	rqos->q = q;
-
-	/*
-	 * Registering the rq-qos policy after activating the blk-cgroup
-	 * policy guarantees that ioprio_blkcg_from_bio(bio) != NULL in the
-	 * rq-qos callbacks.
-	 */
-	rq_qos_add(q, rqos);
-
-	return 0;
+	return ret;
 }
 
 static int __init ioprio_init(void)
 {
-	return blkcg_policy_register(&ioprio_policy);
+	int ret;
+
+	ret = rq_qos_register(&blkcg_ioprio_ops);
+	if (ret)
+		return ret;
+
+	ret = blkcg_policy_register(&ioprio_policy);
+	if (ret)
+		rq_qos_unregister(&blkcg_ioprio_ops);
+
+	return ret;
 }
 
 static void __exit ioprio_exit(void)
 {
 	blkcg_policy_unregister(&ioprio_policy);
+	rq_qos_unregister(&blkcg_ioprio_ops);
 }
 
 module_init(ioprio_init);
 module_exit(ioprio_exit);
+MODULE_AUTHOR("Bart Van Assche");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Cgroup I/O controller for assigning an I/O priority class");
diff --git a/block/blk-ioprio.h b/block/blk-ioprio.h
deleted file mode 100644
index a7785c2f1aea..000000000000
--- a/block/blk-ioprio.h
+++ /dev/null
@@ -1,19 +0,0 @@ 
-/* 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-mq-debugfs.c b/block/blk-mq-debugfs.c
index 45da42e9e242..cbbd668029a1 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -825,10 +825,6 @@  void blk_mq_debugfs_unregister_sched(struct request_queue *q)
 
 static const char *rq_qos_id_to_name(enum rq_qos_id id)
 {
-	switch (id) {
-	case RQ_QOS_IOPRIO:
-		return "ioprio";
-	}
 	return "unknown";
 }
 
diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c
index db13581ae878..23cb7a3fa9b2 100644
--- a/block/blk-rq-qos.c
+++ b/block/blk-rq-qos.c
@@ -452,7 +452,7 @@  int rq_qos_register(struct rq_qos_ops *ops)
 		goto out;
 	}
 
-	start = RQ_QOS_IOPRIO + 1;
+	start = 1;
 	ret = ida_simple_get(&rq_qos_ida, start, INT_MAX, GFP_KERNEL);
 	if (ret < 0)
 		goto out;
diff --git a/block/blk-rq-qos.h b/block/blk-rq-qos.h
index 6d691527cb51..bba829bbb461 100644
--- a/block/blk-rq-qos.h
+++ b/block/blk-rq-qos.h
@@ -14,7 +14,7 @@ 
 struct blk_mq_debugfs_attr;
 
 enum rq_qos_id {
-	RQ_QOS_IOPRIO,
+	RQ_QOS_UNUSED,
 };
 
 struct rq_wait {