linux-kernel - Re: [PATCH -mm] relayfs: support larger relay buffer take 3

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Date:	Wed, 16 Apr 2008 17:00:08 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	penberg@...helsinki.fi, zanussi@...cast.net, dwilder@...ibm.com,
	systemtap@...rces.redhat.com, linux-kernel@...r.kernel.org,
	tzanussi@...il.com
Subject: Re: [PATCH -mm] relayfs: support larger relay buffer take 3

Hi Andrew,

Andrew Morton wrote:
> On Wed, 16 Apr 2008 15:51:56 -0400
> Masami Hiramatsu <mhiramat@...hat.com> wrote:
> 
>> +static struct page **relay_alloc_page_array(unsigned int n_pages)
>> +{
>> +	struct page **array;
>> +	unsigned int pa_size = n_pages * sizeof(struct page *);
>> +
>> +	if (pa_size > PAGE_SIZE) {
>> +		array = vmalloc(pa_size);
>> +		if (array)
>> +			memset(array, 0, pa_size);
>> +	} else {
>> +		array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
>> +	}
>> +	return array;
>> +}
> 
> It's a bit odd to multiply n_pages*sizeof() and to then call kcalloc(),
> which needs to do the same multiplication.
> 
> The compiler will presumably optimise that away, but still, how about this?

Sure, it looks good to me.
Thank you so much,

Acked-by: Masami Hiramatsu <mhiramat@...hat.com>

> 
> --- a/kernel/relay.c~relayfs-support-larger-relay-buffer-take-3-cleanup
> +++ a/kernel/relay.c
> @@ -71,14 +71,14 @@ static struct vm_operations_struct relay
>  static struct page **relay_alloc_page_array(unsigned int n_pages)
>  {
>  	struct page **array;
> -	unsigned int pa_size = n_pages * sizeof(struct page *);
> +	size_t pa_size = n_pages * sizeof(struct page *);
>  
>  	if (pa_size > PAGE_SIZE) {
>  		array = vmalloc(pa_size);
>  		if (array)
>  			memset(array, 0, pa_size);
>  	} else {
> -		array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
> +		array = kzalloc(pa_size, GFP_KERNEL);
>  	}
>  	return array;
>  }
> _
> 
> 
> size_t is strictly the correct type for pa_size here.  Even though
> vmalloc() takes a ulong.

Thanks for the advice,


-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com

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