linux-kernel - Re: [PATCH 02/11] proc_sysctl: move helper which creates required subdirectories

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Date:   Thu, 2 Mar 2023 14:56:21 -0800
From:   John Johansen <john.johansen@...onical.com>
To:     Luis Chamberlain <mcgrof@...nel.org>, ebiederm@...ssion.com,
        keescook@...omium.org, yzaikin@...gle.com, paul@...l-moore.com,
        jmorris@...ei.org, serge@...lyn.com, luto@...capital.net,
        wad@...omium.org, dverkamp@...omium.org, paulmck@...nel.org,
        baihaowen@...zu.com, frederic@...nel.org, jeffxu@...gle.com,
        ebiggers@...nel.org, tytso@....edu, guoren@...nel.org
Cc:     j.granados@...sung.com, zhangpeng362@...wei.com,
        tangmeng@...ontech.com, willy@...radead.org, nixiaoming@...wei.com,
        sujiaxun@...ontech.com, patches@...ts.linux.dev,
        linux-fsdevel@...r.kernel.org, apparmor@...ts.ubuntu.com,
        linux-security-module@...r.kernel.org, linux-csky@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/11] proc_sysctl: move helper which creates required
 subdirectories

On 3/2/23 12:28, Luis Chamberlain wrote:
> Move the code which creates the subdirectories for a ctl table
> into a helper routine so to make it easier to review. Document
> the goal.
> 
> This creates no functional changes.
> 
> Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>

Reviewed-by: John Johansen <john.johansen@...onical.com>

> ---
>   fs/proc/proc_sysctl.c | 56 ++++++++++++++++++++++++-------------------
>   1 file changed, 32 insertions(+), 24 deletions(-)
> 
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index 1df0beb50dbe..6b9b2694d430 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -1283,6 +1283,35 @@ static int insert_links(struct ctl_table_header *head)
>   	return err;
>   }
>   
> +/* Find the directory for the ctl_table. If one is not found create it. */
> +static struct ctl_dir *sysctl_mkdir_p(struct ctl_dir *dir, const char *path)
> +{
> +	const char *name, *nextname;
> +
> +	for (name = path; name; name = nextname) {
> +		int namelen;
> +		nextname = strchr(name, '/');
> +		if (nextname) {
> +			namelen = nextname - name;
> +			nextname++;
> +		} else {
> +			namelen = strlen(name);
> +		}
> +		if (namelen == 0)
> +			continue;
> +
> +		/*
> +		 * namelen ensures if name is "foo/bar/yay" only foo is
> +		 * registered first. We traverse as if using mkdir -p and
> +		 * return a ctl_dir for the last directory entry.
> +		 */
> +		dir = get_subdir(dir, name, namelen);
> +		if (IS_ERR(dir))
> +			break;
> +	}
> +	return dir;
> +}
> +
>   /**
>    * __register_sysctl_table - register a leaf sysctl table
>    * @set: Sysctl tree to register on
> @@ -1334,7 +1363,6 @@ struct ctl_table_header *__register_sysctl_table(
>   {
>   	struct ctl_table_root *root = set->dir.header.root;
>   	struct ctl_table_header *header;
> -	const char *name, *nextname;
>   	struct ctl_dir *dir;
>   	struct ctl_table *entry;
>   	struct ctl_node *node;
> @@ -1359,29 +1387,9 @@ struct ctl_table_header *__register_sysctl_table(
>   	dir->header.nreg++;
>   	spin_unlock(&sysctl_lock);
>   
> -	/* Find the directory for the ctl_table */
> -	for (name = path; name; name = nextname) {
> -		int namelen;
> -		nextname = strchr(name, '/');
> -		if (nextname) {
> -			namelen = nextname - name;
> -			nextname++;
> -		} else {
> -			namelen = strlen(name);
> -		}
> -		if (namelen == 0)
> -			continue;
> -
> -		/*
> -		 * namelen ensures if name is "foo/bar/yay" only foo is
> -		 * registered first. We traverse as if using mkdir -p and
> -		 * return a ctl_dir for the last directory entry.
> -		 */
> -		dir = get_subdir(dir, name, namelen);
> -		if (IS_ERR(dir))
> -			goto fail;
> -	}
> -
> +	dir = sysctl_mkdir_p(dir, path);
> +	if (IS_ERR(dir))
> +		goto fail;
>   	spin_lock(&sysctl_lock);
>   	if (insert_header(dir, header))
>   		goto fail_put_dir_locked;