Re: [PATCH v10 06/10] x86/resctrl: Move default group file creation to mount

[Ilpo Järvinen]

On Fri, 15 Sep 2023, Babu Moger wrote:

> 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>
> Reviewed-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
> Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> ---
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 58 +++++++++++++++-----------
>  1 file changed, 34 insertions(+), 24 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 3ea874c80c22..a34657f0bd0c 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -54,6 +54,9 @@ static struct kernfs_node *kn_mondata;
>  static struct seq_buf last_cmd_status;
>  static char last_cmd_status_buf[512];
>  
> +static int rdtgroup_setup_root(struct rdt_fs_context *ctx);
> +static void rdtgroup_destroy_root(void);
> +
>  struct dentry *debugfs_resctrl;
>  
>  void rdt_last_cmd_clear(void)
> @@ -2511,10 +2514,14 @@ 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();
> @@ -2523,6 +2530,12 @@ 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;
> @@ -2579,6 +2592,8 @@ 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);
> @@ -2649,7 +2664,6 @@ 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;
> @@ -2819,6 +2833,7 @@ 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);
> @@ -3700,10 +3715,8 @@ static struct kernfs_syscall_ops rdtgroup_kf_syscall_ops = {
>  	.show_options	= rdtgroup_show_options,
>  };
>  
> -static int __init rdtgroup_setup_root(void)
> +static 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,
> @@ -3711,6 +3724,20 @@ 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;
> +}
> +
> +static 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;
> @@ -3720,19 +3747,7 @@ 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)
> @@ -3854,13 +3869,11 @@ 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)
> @@ -3893,8 +3906,6 @@ int __init rdtgroup_init(void)
>  
>  cleanup_mountpoint:
>  	sysfs_remove_mount_point(fs_kobj, "resctrl");
> -cleanup_root:
> -	kernfs_destroy_root(rdt_root);
>  
>  	return ret;
>  }
> @@ -3904,5 +3915,4 @@ 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);
>  }
> 

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>

-- 
 i.