linux-kernel - Re: [PATCH 1/9] lib: string_helpers: provide kfree

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Date:   Fri, 25 Sep 2020 11:48:04 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Kent Gibson <warthog618@...il.com>, linux-gpio@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH 1/9] lib: string_helpers: provide kfree_strarray()

On Thu, Sep 24, 2020 at 01:38:34PM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> 
> There's a common pattern of dynamically allocating an array of char
> pointers and then also dynamically allocating each string in this
> array. Provide a helper for freeing such a string array with one call.

For consistency I would like to provide kalloc_strarray(), but it seems a bit
ambiguous. So I'm fine with this going alone.

> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> ---
>  include/linux/string_helpers.h |  2 ++
>  lib/string_helpers.c           | 22 ++++++++++++++++++++++
>  2 files changed, 24 insertions(+)
> 
> diff --git a/include/linux/string_helpers.h b/include/linux/string_helpers.h
> index 86f150c2a6b6..55b25120a1c6 100644
> --- a/include/linux/string_helpers.h
> +++ b/include/linux/string_helpers.h
> @@ -94,4 +94,6 @@ char *kstrdup_quotable(const char *src, gfp_t gfp);
>  char *kstrdup_quotable_cmdline(struct task_struct *task, gfp_t gfp);
>  char *kstrdup_quotable_file(struct file *file, gfp_t gfp);
>  
> +void kfree_strarray(char **str_array, size_t num_str);
> +
>  #endif
> diff --git a/lib/string_helpers.c b/lib/string_helpers.c
> index 963050c0283e..56c01ec8a076 100644
> --- a/lib/string_helpers.c
> +++ b/lib/string_helpers.c
> @@ -649,3 +649,25 @@ char *kstrdup_quotable_file(struct file *file, gfp_t gfp)
>  	return pathname;
>  }
>  EXPORT_SYMBOL_GPL(kstrdup_quotable_file);
> +
> +/**
> + * kfree_strarray - free a number of dynamically allocated strings contained
> + *                  in an array and the array itself
> + *

> + * @str_array: Dynamically allocated array of strings to free. If NULL - the
> + *             function does nothing.
> + * @num_str: Number of strings (starting from the beginning of the array) to
> + *           free.

Can we use same names as done for other string array related functions, i.e.
str_array -> array
num_str -> n

?

(See *match_string() APIs)

> + *
> + * Passing a non-null str_array and num_str == 0 as well as NULL str_array and
> + * num_str == 0 are valid use-cases.

You still may refer to the parameters in the description using @param notation,
like @str_array.

> + */
> +void kfree_strarray(char **str_array, size_t num_str)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < num_str; i++)
> +		kfree(str_array[i]);
> +	kfree(str_array);
> +}
> +EXPORT_SYMBOL_GPL(kfree_strarray);
> -- 
> 2.26.1
> 

-- 
With Best Regards,
Andy Shevchenko