linux-kernel - Re: [PATCH 3/3] proc: use kzalloc instead of kmalloc and memset

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Message-ID: <50454EDC.7050101@gmail.com>
Date:	Tue, 04 Sep 2012 10:44:12 +1000
From:	Ryan Mallon <rmallon@...il.com>
To:	yan <clouds.yan@...il.com>
CC:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] proc: use kzalloc instead of kmalloc and memset

On 04/09/12 00:14, yan wrote:
> Signed-off-by: yan <clouds.yan@...il.com>
> ---
>  fs/proc/generic.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/proc/generic.c b/fs/proc/generic.c
> index 9e8f631..38de015 100644
> --- a/fs/proc/generic.c
> +++ b/fs/proc/generic.c
> @@ -616,10 +616,9 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
>  
>  	len = strlen(fn);
>  
> -	ent = kmalloc(sizeof(struct proc_dir_entry) + len + 1, GFP_KERNEL);
> +	ent = kzalloc(sizeof(struct proc_dir_entry) + len + 1, GFP_KERNEL);
>  	if (!ent) goto out;
>  
> -	memset(ent, 0, sizeof(struct proc_dir_entry));
>  	memcpy(ent->name, fn, len + 1);
>  	ent->namelen = len;
>  	ent->mode = mode;

Note that this change results in slightly different behaviour. Before
your change only sizeof(struct proc_dir_entry) is zero'ed by memset, and
then the name is filled in (the len + 1 part). After your change the
structure and the name field are both zeroed, so the name field is being
written to twice. The cost is probably negligible though.

~Ryan


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