[PATCH v8 6/8] x86/resctrl: Move default group file creation to mount

[Babu Moger]

The default resource group and its files are created during kernel
init time. Upcoming changes will make some resctrl files optional
based on a mount parameter. If optional files are to be added to the
default group based on the mount option, then each new file needs to
be created separately and call kernfs_activate() again.

Create all files of the default resource group during resctrl
mount, destroyed during unmount, to avoid scattering resctrl
file addition across two separate code flows.

Suggested-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
 arch/x86/kernel/cpu/resctrl/internal.h |  2 +
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 55 +++++++++++++++-----------
 2 files changed, 33 insertions(+), 24 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index b09e7abd1299..44ad98f8c7af 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -611,5 +611,7 @@ void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
 void __init thread_throttle_mode_init(void);
 void __init mbm_config_rftype_init(const char *config);
 void rdt_staged_configs_clear(void);
+int rdtgroup_setup_root(struct rdt_fs_context *ctx);
+void rdtgroup_destroy_root(void);
 
 #endif /* _ASM_X86_RESCTRL_INTERNAL_H */
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 80a4f76bc34b..98f9f880c30b 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -2516,10 +2516,14 @@ static int rdt_get_tree(struct fs_context *fc)
 		goto out;
 	}
 
-	ret = rdt_enable_ctx(ctx);
+	ret = rdtgroup_setup_root(ctx);
 	if (ret)
 		goto out;
 
+	ret = rdt_enable_ctx(ctx);
+	if (ret)
+		goto out_root;
+
 	ret = schemata_list_create();
 	if (ret) {
 		schemata_list_destroy();
@@ -2528,6 +2532,12 @@ static int rdt_get_tree(struct fs_context *fc)
 
 	closid_init();
 
+	ret = rdtgroup_add_files(rdtgroup_default.kn, RFTYPE_CTRL_BASE);
+	if (ret)
+		goto out_schemata_free;
+
+	kernfs_activate(rdtgroup_default.kn);
+
 	ret = rdtgroup_create_info_dir(rdtgroup_default.kn);
 	if (ret < 0)
 		goto out_schemata_free;
@@ -2584,6 +2594,8 @@ static int rdt_get_tree(struct fs_context *fc)
 	schemata_list_destroy();
 out_ctx:
 	rdt_disable_ctx();
+out_root:
+	rdtgroup_destroy_root();
 out:
 	rdt_last_cmd_clear();
 	mutex_unlock(&rdtgroup_mutex);
@@ -2654,7 +2666,6 @@ static int rdt_init_fs_context(struct fs_context *fc)
 	if (!ctx)
 		return -ENOMEM;
 
-	ctx->kfc.root = rdt_root;
 	ctx->kfc.magic = RDTGROUP_SUPER_MAGIC;
 	fc->fs_private = &ctx->kfc;
 	fc->ops = &rdt_fs_context_ops;
@@ -2824,6 +2835,7 @@ static void rdt_kill_sb(struct super_block *sb)
 	rdt_pseudo_lock_release();
 	rdtgroup_default.mode = RDT_MODE_SHAREABLE;
 	schemata_list_destroy();
+	rdtgroup_destroy_root();
 	static_branch_disable_cpuslocked(&rdt_alloc_enable_key);
 	static_branch_disable_cpuslocked(&rdt_mon_enable_key);
 	static_branch_disable_cpuslocked(&rdt_enable_key);
@@ -3705,10 +3717,8 @@ static struct kernfs_syscall_ops rdtgroup_kf_syscall_ops = {
 	.show_options	= rdtgroup_show_options,
 };
 
-static int __init rdtgroup_setup_root(void)
+int rdtgroup_setup_root(struct rdt_fs_context *ctx)
 {
-	int ret;
-
 	rdt_root = kernfs_create_root(&rdtgroup_kf_syscall_ops,
 				      KERNFS_ROOT_CREATE_DEACTIVATED |
 				      KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
@@ -3716,6 +3726,20 @@ static int __init rdtgroup_setup_root(void)
 	if (IS_ERR(rdt_root))
 		return PTR_ERR(rdt_root);
 
+	ctx->kfc.root = rdt_root;
+	rdtgroup_default.kn = kernfs_root_to_node(rdt_root);
+
+	return 0;
+}
+
+void rdtgroup_destroy_root(void)
+{
+	kernfs_destroy_root(rdt_root);
+	rdtgroup_default.kn = NULL;
+}
+
+static void __init rdtgroup_setup_default(void)
+{
 	mutex_lock(&rdtgroup_mutex);
 
 	rdtgroup_default.closid = 0;
@@ -3725,19 +3749,7 @@ static int __init rdtgroup_setup_root(void)
 
 	list_add(&rdtgroup_default.rdtgroup_list, &rdt_all_groups);
 
-	ret = rdtgroup_add_files(kernfs_root_to_node(rdt_root), RFTYPE_CTRL_BASE);
-	if (ret) {
-		kernfs_destroy_root(rdt_root);
-		goto out;
-	}
-
-	rdtgroup_default.kn = kernfs_root_to_node(rdt_root);
-	kernfs_activate(rdtgroup_default.kn);
-
-out:
 	mutex_unlock(&rdtgroup_mutex);
-
-	return ret;
 }
 
 static void domain_destroy_mon_state(struct rdt_domain *d)
@@ -3859,13 +3871,11 @@ int __init rdtgroup_init(void)
 	seq_buf_init(&last_cmd_status, last_cmd_status_buf,
 		     sizeof(last_cmd_status_buf));
 
-	ret = rdtgroup_setup_root();
-	if (ret)
-		return ret;
+	rdtgroup_setup_default();
 
 	ret = sysfs_create_mount_point(fs_kobj, "resctrl");
 	if (ret)
-		goto cleanup_root;
+		return ret;
 
 	ret = register_filesystem(&rdt_fs_type);
 	if (ret)
@@ -3898,8 +3908,6 @@ int __init rdtgroup_init(void)
 
 cleanup_mountpoint:
 	sysfs_remove_mount_point(fs_kobj, "resctrl");
-cleanup_root:
-	kernfs_destroy_root(rdt_root);
 
 	return ret;
 }
@@ -3909,5 +3917,4 @@ void __exit rdtgroup_exit(void)
 	debugfs_remove_recursive(debugfs_resctrl);
 	unregister_filesystem(&rdt_fs_type);
 	sysfs_remove_mount_point(fs_kobj, "resctrl");
-	kernfs_destroy_root(rdt_root);
 }
-- 
2.34.1