linux-kernel - Re: [PATCH 1/2] mm/zswap: make type and compressor const

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Message-ID: <CALZtOND9r9gz8cUPYfRN7Wjaowcx1uHnqQbNw8Qxo8pRSgJwcw@mail.gmail.com>
Date:   Mon, 8 Jan 2018 14:22:13 -0500
From:   Dan Streetman <ddstreet@...e.org>
To:     Joey Pabalinas <joeypabalinas@...il.com>
Cc:     Linux-MM <linux-mm@...ck.org>, Seth Jennings <sjenning@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] mm/zswap: make type and compressor const

On Tue, Jan 2, 2018 at 5:03 AM, Joey Pabalinas <joeypabalinas@...il.com> wrote:
> The characters pointed to by `zswap_compressor`, `type`, and `compressor`
> aren't ever modified. Add const to the static variable and both parameters in
> `zswap_pool_find_get()`, `zswap_pool_create()`, and `__zswap_param_set()`
>
> Signed-off-by: Joey Pabalinas <joeypabalinas@...il.com>

Nak.

Those variables are not const; they are updated in
__zswap_param_set().  They aren't modified in pool_find_get() or
pool_create(), but they certainly aren't globally const.

>
>  1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index d39581a076c3aed1e9..a4f2dfaf9131694265 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -90,7 +90,7 @@ module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644);
>
>  /* Crypto compressor to use */
>  #define ZSWAP_COMPRESSOR_DEFAULT "lzo"
> -static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
> +static const char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
>  static int zswap_compressor_param_set(const char *,
>                                       const struct kernel_param *);
>  static struct kernel_param_ops zswap_compressor_param_ops = {
> @@ -475,7 +475,8 @@ static struct zswap_pool *zswap_pool_last_get(void)
>  }
>
>  /* type and compressor must be null-terminated */
> -static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
> +static struct zswap_pool *zswap_pool_find_get(const char *type,
> +                                             const char *compressor)
>  {
>         struct zswap_pool *pool;
>
> @@ -495,7 +496,8 @@ static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
>         return NULL;
>  }
>
> -static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
> +static struct zswap_pool *zswap_pool_create(const char *type,
> +                                           const char *compressor)
>  {
>         struct zswap_pool *pool;
>         char name[38]; /* 'zswap' + 32 char (max) num + \0 */
> @@ -658,7 +660,7 @@ static void zswap_pool_put(struct zswap_pool *pool)
>
>  /* val must be a null-terminated string */
>  static int __zswap_param_set(const char *val, const struct kernel_param *kp,
> -                            char *type, char *compressor)
> +                            const char *type, const char *compressor)
>  {
>         struct zswap_pool *pool, *put_pool = NULL;
>         char *s = strstrip((char *)val);
> --
> 2.15.1
>