Re: [PATCH 1/2] configfs: reduce memory consumption by symlinks

[Joel Becker <jlbec@evilplan.org>]

On Mon, Apr 01, 2024 at 11:26:54AM +0300, Dmitry Bogdanov wrote:
> Instead of preallocating PAGE_SIZE for a symlink path, allocate the exact
> size of that path.
> 
> Fixes: e9c03af21cc7 (configfs: calculate the symlink target only once)
> Signed-off-by: Dmitry Bogdanov <d.bogdanov@yadro.com>

Reviewed-by: Joel Becker <jlbec@evilplan.org>

> 
> ---
> I treat this as bugfux due to reducing of enourmous memory consumption.
> ---
>  fs/configfs/symlink.c | 22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/configfs/symlink.c b/fs/configfs/symlink.c
> index 0623c3edcfb9..224c9e4899d4 100644
> --- a/fs/configfs/symlink.c
> +++ b/fs/configfs/symlink.c
> @@ -54,7 +54,7 @@ static void fill_item_path(struct config_item * item, char * buffer, int length)
>  }
>  
>  static int configfs_get_target_path(struct config_item *item,
> -		struct config_item *target, char *path)
> +		struct config_item *target, char **path)
>  {
>  	int depth, size;
>  	char *s;
> @@ -66,11 +66,16 @@ static int configfs_get_target_path(struct config_item *item,
>  
>  	pr_debug("%s: depth = %d, size = %d\n", __func__, depth, size);
>  
> -	for (s = path; depth--; s += 3)
> +	*path = kzalloc(size, GFP_KERNEL);
> +	if (!*path)
> +		return -ENOMEM;
> +
> +
> +	for (s = *path; depth--; s += 3)
>  		strcpy(s,"../");
>  
> -	fill_item_path(target, path, size);
> -	pr_debug("%s: path = '%s'\n", __func__, path);
> +	fill_item_path(target, *path, size);
> +	pr_debug("%s: path = '%s'\n", __func__, *path);
>  	return 0;
>  }
>  
> @@ -79,27 +84,22 @@ static int create_link(struct config_item *parent_item,
>  		       struct dentry *dentry)
>  {
>  	struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata;
> -	char *body;
> +	char *body = NULL;
>  	int ret;
>  
>  	if (!configfs_dirent_is_ready(target_sd))
>  		return -ENOENT;
>  
> -	body = kzalloc(PAGE_SIZE, GFP_KERNEL);
> -	if (!body)
> -		return -ENOMEM;
> -
>  	configfs_get(target_sd);
>  	spin_lock(&configfs_dirent_lock);
>  	if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
>  		spin_unlock(&configfs_dirent_lock);
>  		configfs_put(target_sd);
> -		kfree(body);
>  		return -ENOENT;
>  	}
>  	target_sd->s_links++;
>  	spin_unlock(&configfs_dirent_lock);
> -	ret = configfs_get_target_path(parent_item, item, body);
> +	ret = configfs_get_target_path(parent_item, item, &body);
>  	if (!ret)
>  		ret = configfs_create_link(target_sd, parent_item->ci_dentry,
>  					   dentry, body);
> -- 
> 2.25.1
> 

-- 

"Can any of you seriously say the Bill of Rights could get through
 Congress today?  It wouldn't even get out of committee."
	- F. Lee Bailey

			http://www.jlbec.org/
			jlbec@evilplan.org