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Subject: [PATCH v5 7/8] x86/resctrl: Move default control group creation
 during mount
From:   Babu Moger <babu.moger@amd.com>
To:     <corbet@lwn.net>, <reinette.chatre@intel.com>,
        <tglx@linutronix.de>, <mingo@redhat.com>, <bp@alien8.de>
CC:     <fenghua.yu@intel.com>, <dave.hansen@linux.intel.com>,
        <x86@kernel.org>, <hpa@zytor.com>, <paulmck@kernel.org>,
        <akpm@linux-foundation.org>, <quic_neeraju@quicinc.com>,
        <rdunlap@infradead.org>, <damien.lemoal@opensource.wdc.com>,
        <songmuchun@bytedance.com>, <peterz@infradead.org>,
        <jpoimboe@kernel.org>, <pbonzini@redhat.com>, <babu.moger@amd.com>,
        <chang.seok.bae@intel.com>, <pawan.kumar.gupta@linux.intel.com>,
        <jmattson@google.com>, <daniel.sneddon@linux.intel.com>,
        <sandipan.das@amd.com>, <tony.luck@intel.com>,
        <james.morse@arm.com>, <linux-doc@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <bagasdotme@gmail.com>,
        <eranian@google.com>, <christophe.leroy@csgroup.eu>,
        <pawan.kumar.gupta@linux.intel.com>, <jarkko@kernel.org>,
        <adrian.hunter@intel.com>, <quic_jiles@quicinc.com>,
        <peternewman@google.com>, <babu.moger@amd.com>
Date:   Thu, 1 Jun 2023 14:02:01 -0500
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Currently, the resctrl default control group is created during kernel=0A=
init time and rest of the files are added during mount. If the new=0A=
files are to be added to the default group during the mount then it=0A=
has to be done separately again.=0A=
=0A=
This can avoided if all the files are created during the mount and=0A=
destroyed during the umount. Move the default group creation in=0A=
rdt_get_tree and removal in rdt_kill_sb.=0A=
=0A=
Suggested-by: Reinette Chatre <reinette.chatre@intel.com>=0A=
Signed-off-by: Babu Moger <babu.moger@amd.com>=0A=
---=0A=
 arch/x86/kernel/cpu/resctrl/rdtgroup.c |   59 ++++++++++++++++------------=
----=0A=
 1 file changed, 30 insertions(+), 29 deletions(-)=0A=
=0A=
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/r=
esctrl/rdtgroup.c=0A=
index 2f5cdc638607..e03cb01c4742 100644=0A=
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c=0A=
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c=0A=
@@ -57,6 +57,7 @@ static char last_cmd_status_buf[512];=0A=
 struct dentry *debugfs_resctrl;=0A=
 =0A=
 static bool resctrl_debug;=0A=
+static int rdtgroup_setup_root(void);=0A=
 =0A=
 void rdt_last_cmd_clear(void)=0A=
 {=0A=
@@ -2515,13 +2516,6 @@ static int rdt_get_tree(struct fs_context *fc)=0A=
 =0A=
 	cpus_read_lock();=0A=
 	mutex_lock(&rdtgroup_mutex);=0A=
-	/*=0A=
-	 * resctrl file system can only be mounted once.=0A=
-	 */=0A=
-	if (static_branch_unlikely(&rdt_enable_key)) {=0A=
-		ret =3D -EBUSY;=0A=
-		goto out;=0A=
-	}=0A=
 =0A=
 	ret =3D rdt_enable_ctx(ctx);=0A=
 	if (ret < 0)=0A=
@@ -2535,9 +2529,15 @@ static int rdt_get_tree(struct fs_context *fc)=0A=
 =0A=
 	closid_init();=0A=
 =0A=
+	ret =3D rdtgroup_add_files(rdtgroup_default.kn, RFTYPE_CTRL_BASE);=0A=
+	if (ret)=0A=
+		goto out_schemata_free;=0A=
+=0A=
+	kernfs_activate(rdtgroup_default.kn);=0A=
+=0A=
 	ret =3D rdtgroup_create_info_dir(rdtgroup_default.kn);=0A=
 	if (ret < 0)=0A=
-		goto out_schemata_free;=0A=
+		goto out_default;=0A=
 =0A=
 	if (rdt_mon_capable) {=0A=
 		ret =3D mongroup_create_dir(rdtgroup_default.kn,=0A=
@@ -2587,6 +2587,8 @@ static int rdt_get_tree(struct fs_context *fc)=0A=
 		kernfs_remove(kn_mongrp);=0A=
 out_info:=0A=
 	kernfs_remove(kn_info);=0A=
+out_default:=0A=
+	kernfs_remove(rdtgroup_default.kn);=0A=
 out_schemata_free:=0A=
 	schemata_list_destroy();=0A=
 out_mba:=0A=
@@ -2664,10 +2666,23 @@ static const struct fs_context_operations rdt_fs_co=
ntext_ops =3D {=0A=
 static int rdt_init_fs_context(struct fs_context *fc)=0A=
 {=0A=
 	struct rdt_fs_context *ctx;=0A=
+	int ret;=0A=
+=0A=
+	/*=0A=
+	 * resctrl file system can only be mounted once.=0A=
+	 */=0A=
+	if (static_branch_unlikely(&rdt_enable_key))=0A=
+		return -EBUSY;=0A=
+=0A=
+	ret =3D rdtgroup_setup_root();=0A=
+	if (ret)=0A=
+		return ret;=0A=
 =0A=
 	ctx =3D kzalloc(sizeof(struct rdt_fs_context), GFP_KERNEL);=0A=
-	if (!ctx)=0A=
+	if (!ctx) {=0A=
+		kernfs_destroy_root(rdt_root);=0A=
 		return -ENOMEM;=0A=
+	}=0A=
 =0A=
 	ctx->kfc.root =3D rdt_root;=0A=
 	ctx->kfc.magic =3D RDTGROUP_SUPER_MAGIC;=0A=
@@ -2845,6 +2860,9 @@ static void rdt_kill_sb(struct super_block *sb)=0A=
 	static_branch_disable_cpuslocked(&rdt_alloc_enable_key);=0A=
 	static_branch_disable_cpuslocked(&rdt_mon_enable_key);=0A=
 	static_branch_disable_cpuslocked(&rdt_enable_key);=0A=
+	/* Remove the default group and cleanup the root */=0A=
+	list_del(&rdtgroup_default.rdtgroup_list);=0A=
+	kernfs_destroy_root(rdt_root);=0A=
 	kernfs_kill_sb(sb);=0A=
 	mutex_unlock(&rdtgroup_mutex);=0A=
 	cpus_read_unlock();=0A=
@@ -3598,10 +3616,8 @@ static struct kernfs_syscall_ops rdtgroup_kf_syscall=
_ops =3D {=0A=
 	.show_options	=3D rdtgroup_show_options,=0A=
 };=0A=
 =0A=
-static int __init rdtgroup_setup_root(void)=0A=
+static int rdtgroup_setup_root(void)=0A=
 {=0A=
-	int ret;=0A=
-=0A=
 	rdt_root =3D kernfs_create_root(&rdtgroup_kf_syscall_ops,=0A=
 				      KERNFS_ROOT_CREATE_DEACTIVATED |=0A=
 				      KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,=0A=
@@ -3618,19 +3634,11 @@ static int __init rdtgroup_setup_root(void)=0A=
 =0A=
 	list_add(&rdtgroup_default.rdtgroup_list, &rdt_all_groups);=0A=
 =0A=
-	ret =3D rdtgroup_add_files(kernfs_root_to_node(rdt_root), RFTYPE_CTRL_BAS=
E);=0A=
-	if (ret) {=0A=
-		kernfs_destroy_root(rdt_root);=0A=
-		goto out;=0A=
-	}=0A=
-=0A=
 	rdtgroup_default.kn =3D kernfs_root_to_node(rdt_root);=0A=
-	kernfs_activate(rdtgroup_default.kn);=0A=
 =0A=
-out:=0A=
 	mutex_unlock(&rdtgroup_mutex);=0A=
 =0A=
-	return ret;=0A=
+	return 0;=0A=
 }=0A=
 =0A=
 static void domain_destroy_mon_state(struct rdt_domain *d)=0A=
@@ -3752,13 +3760,9 @@ int __init rdtgroup_init(void)=0A=
 	seq_buf_init(&last_cmd_status, last_cmd_status_buf,=0A=
 		     sizeof(last_cmd_status_buf));=0A=
 =0A=
-	ret =3D rdtgroup_setup_root();=0A=
-	if (ret)=0A=
-		return ret;=0A=
-=0A=
 	ret =3D sysfs_create_mount_point(fs_kobj, "resctrl");=0A=
 	if (ret)=0A=
-		goto cleanup_root;=0A=
+		return ret;=0A=
 =0A=
 	ret =3D register_filesystem(&rdt_fs_type);=0A=
 	if (ret)=0A=
@@ -3791,8 +3795,6 @@ int __init rdtgroup_init(void)=0A=
 =0A=
 cleanup_mountpoint:=0A=
 	sysfs_remove_mount_point(fs_kobj, "resctrl");=0A=
-cleanup_root:=0A=
-	kernfs_destroy_root(rdt_root);=0A=
 =0A=
 	return ret;=0A=
 }=0A=
@@ -3802,5 +3804,4 @@ void __exit rdtgroup_exit(void)=0A=
 	debugfs_remove_recursive(debugfs_resctrl);=0A=
 	unregister_filesystem(&rdt_fs_type);=0A=
 	sysfs_remove_mount_point(fs_kobj, "resctrl");=0A=
-	kernfs_destroy_root(rdt_root);=0A=
 }=0A=
=0A=