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Subject: [PATCH v6 6/8] 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:   Wed, 19 Jul 2023 18:22:11 -0500
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In-Reply-To: <168980872063.1619861.420806535295905172.stgit@bmoger-ubuntu>
References: <168980872063.1619861.420806535295905172.stgit@bmoger-ubuntu>
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The resctrl default control group is created during kernel init time. If=0A=
the new files are to be added to the default group during the mount based=
=0A=
on the mount option, then each file needs to be created separately and=0A=
call kernfs_activate.=0A=
=0A=
This can avoided if all the files are created during the mount and=0A=
destroyed during the umount. Move the root and default group creation=0A=
in 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/internal.h |    1 +=0A=
 arch/x86/kernel/cpu/resctrl/rdtgroup.c |   51 ++++++++++++++--------------=
----=0A=
 2 files changed, 24 insertions(+), 28 deletions(-)=0A=
=0A=
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/r=
esctrl/internal.h=0A=
index 783c3e36633c..885b656d1088 100644=0A=
--- a/arch/x86/kernel/cpu/resctrl/internal.h=0A=
+++ b/arch/x86/kernel/cpu/resctrl/internal.h=0A=
@@ -601,5 +601,6 @@ void rdt_domain_reconfigure_cdp(struct rdt_resource *r)=
;=0A=
 void __init thread_throttle_mode_init(void);=0A=
 void __init mbm_config_rftype_init(const char *config);=0A=
 void rdt_staged_configs_clear(void);=0A=
+int rdtgroup_setup_root(void);=0A=
 =0A=
 #endif /* _ASM_X86_RESCTRL_INTERNAL_H */=0A=
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/r=
esctrl/rdtgroup.c=0A=
index 9a7204f71d2d..e0570bce76a2 100644=0A=
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c=0A=
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c=0A=
@@ -2512,10 +2512,16 @@ static int rdt_get_tree(struct fs_context *fc)=0A=
 		goto out;=0A=
 	}=0A=
 =0A=
-	ret =3D rdt_enable_ctx(ctx);=0A=
+	ret =3D rdtgroup_setup_root();=0A=
 	if (ret)=0A=
 		goto out;=0A=
 =0A=
+	ctx->kfc.root =3D rdt_root;=0A=
+=0A=
+	ret =3D rdt_enable_ctx(ctx);=0A=
+	if (ret)=0A=
+		goto out_root;=0A=
+=0A=
 	ret =3D schemata_list_create();=0A=
 	if (ret) {=0A=
 		schemata_list_destroy();=0A=
@@ -2524,6 +2530,12 @@ 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=
@@ -2582,6 +2594,9 @@ static int rdt_get_tree(struct fs_context *fc)=0A=
 	if (ctx->enable_mba_mbps)=0A=
 		set_mba_sc(false);=0A=
 	cdp_disable_all();=0A=
+out_root:=0A=
+	list_del(&rdtgroup_default.rdtgroup_list);=0A=
+	kernfs_destroy_root(rdt_root);=0A=
 out:=0A=
 	rdt_last_cmd_clear();=0A=
 	mutex_unlock(&rdtgroup_mutex);=0A=
@@ -2652,7 +2667,6 @@ static int rdt_init_fs_context(struct fs_context *fc)=
=0A=
 	if (!ctx)=0A=
 		return -ENOMEM;=0A=
 =0A=
-	ctx->kfc.root =3D rdt_root;=0A=
 	ctx->kfc.magic =3D RDTGROUP_SUPER_MAGIC;=0A=
 	fc->fs_private =3D &ctx->kfc;=0A=
 	fc->ops =3D &rdt_fs_context_ops;=0A=
@@ -2821,7 +2835,9 @@ static void rdt_kill_sb(struct super_block *sb)=0A=
 	cdp_disable_all();=0A=
 	rmdir_all_sub();=0A=
 	rdt_pseudo_lock_release();=0A=
-	rdtgroup_default.mode =3D RDT_MODE_SHAREABLE;=0A=
+	/* Remove the default group and cleanup the root */=0A=
+	list_del(&rdtgroup_default.rdtgroup_list);=0A=
+	kernfs_destroy_root(rdt_root);=0A=
 	schemata_list_destroy();=0A=
 	static_branch_disable_cpuslocked(&rdt_alloc_enable_key);=0A=
 	static_branch_disable_cpuslocked(&rdt_mon_enable_key);=0A=
@@ -3704,10 +3720,8 @@ 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=
+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=
@@ -3715,28 +3729,17 @@ static int __init rdtgroup_setup_root(void)=0A=
 	if (IS_ERR(rdt_root))=0A=
 		return PTR_ERR(rdt_root);=0A=
 =0A=
-	mutex_lock(&rdtgroup_mutex);=0A=
-=0A=
 	rdtgroup_default.closid =3D 0;=0A=
 	rdtgroup_default.mon.rmid =3D 0;=0A=
 	rdtgroup_default.type =3D RDTCTRL_GROUP;=0A=
+	rdtgroup_default.mode =3D RDT_MODE_SHAREABLE;=0A=
 	INIT_LIST_HEAD(&rdtgroup_default.mon.crdtgrp_list);=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=
@@ -3858,13 +3861,9 @@ 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=
@@ -3897,9 +3896,6 @@ 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=
 =0A=
@@ -3908,5 +3904,4 @@ 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=