linux-kernel - [PATCH 9/9] blk-cgroup: Simplify policy files registration

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Message-ID: <20250304153801.597907-10-mkoutny@suse.com>
Date: Tue,  4 Mar 2025 16:38:01 +0100
From: Michal Koutný <mkoutny@...e.com>
To: cgroups@...r.kernel.org,
	linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Tejun Heo <tj@...nel.org>,
	Josef Bacik <josef@...icpanda.com>,
	Jens Axboe <axboe@...nel.dk>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Koutný <mkoutny@...e.com>,
	Waiman Long <longman@...hat.com>
Subject: [PATCH 9/9] blk-cgroup: Simplify policy files registration

Use one set of files when there is no difference between default and
legacy files, similar to regular subsys files registration. No
functional change.

Signed-off-by: Michal Koutný <mkoutny@...e.com>
---
 block/blk-cgroup.c     |  7 +++++--
 block/blk-ioprio.c     | 23 +++++++----------------
 include/linux/cgroup.h |  1 +
 kernel/cgroup/cgroup.c |  2 +-
 4 files changed, 14 insertions(+), 19 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b77219dd8b061..db6adc8a7ff41 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1771,12 +1771,15 @@ int blkcg_policy_register(struct blkcg_policy *pol)
 	mutex_unlock(&blkcg_pol_mutex);
 
 	/* everything is in place, add intf files for the new policy */
-	if (pol->dfl_cftypes)
+	if (pol->dfl_cftypes == pol->legacy_cftypes) {
+		WARN_ON(cgroup_add_cftypes(&io_cgrp_subsys,
+					   pol->dfl_cftypes));
+	} else {
 		WARN_ON(cgroup_add_dfl_cftypes(&io_cgrp_subsys,
 					       pol->dfl_cftypes));
-	if (pol->legacy_cftypes)
 		WARN_ON(cgroup_add_legacy_cftypes(&io_cgrp_subsys,
 						  pol->legacy_cftypes));
+	}
 	mutex_unlock(&blkcg_pol_register_mutex);
 	return 0;
 
diff --git a/block/blk-ioprio.c b/block/blk-ioprio.c
index 8fff7ccc0ac73..13659dc15c3ff 100644
--- a/block/blk-ioprio.c
+++ b/block/blk-ioprio.c
@@ -113,27 +113,18 @@ static void ioprio_free_cpd(struct blkcg_policy_data *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
+	{
+		.name		= "prio.class",
+		.seq_show	= ioprio_show_prio_policy,
+		.write		= ioprio_set_prio_policy,
+	},
+	{ } /* sentinel */
 };
 
 static struct blkcg_policy ioprio_policy = {
 	.dfl_cftypes	= ioprio_files,
-	.legacy_cftypes = ioprio_legacy_files,
+	.legacy_cftypes = ioprio_files,
 
 	.cpd_alloc_fn	= ioprio_alloc_cpd,
 	.cpd_free_fn	= ioprio_free_cpd,
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index f8ef47f8a634d..8e7415c64ed1d 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -113,6 +113,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
 
 int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
 int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
+int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
 int cgroup_rm_cftypes(struct cftype *cfts);
 void cgroup_file_notify(struct cgroup_file *cfile);
 void cgroup_file_show(struct cgroup_file *cfile, bool show);
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 3a5af0fc544a6..e93b0563a8964 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4447,7 +4447,7 @@ int cgroup_rm_cftypes(struct cftype *cfts)
  * function currently returns 0 as long as @cfts registration is successful
  * even if some file creation attempts on existing cgroups fail.
  */
-static int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
+int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
 {
 	int ret;
 
-- 
2.48.1