linux-kernel - Re: [PATCH] fs/proc/vmcore.c: Put if tests in the top of the while loop to reduce duplication

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Date:	Fri, 08 Feb 2013 06:25:39 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Zhang Yanfei <zhangyanfei.yes@...il.com>, benh@...nel.crashing.org,
	mahesh@...ux.vnet.ibm.com, zhangyanfei@...fujitsu.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs/proc/vmcore.c: Put if tests in the top of the while loop to reduce duplication

Andrew Morton <akpm@...ux-foundation.org> writes:

> On Sun, 03 Feb 2013 21:13:36 +0800
> Zhang Yanfei <zhangyanfei.yes@...il.com> wrote:
>
>> From: Zhang Yanfei <zhangyanfei@...fujitsu.com>
>> 
>> In function read_vmcore, two if tests are duplicate. Change the position
>> of them could reduce the duplication. This change does not affect
>> the behaviour of the function.

> While we're there, let's squish that assignment-in-a-if pestilence and
> use max_t().

min_t please.  Or do you mean to change the behavior of the code?

> --- a/fs/proc/vmcore.c~fs-proc-vmcorec-put-if-tests-in-the-top-of-the-while-loop-to-reduce-duplication-fix
> +++ a/fs/proc/vmcore.c
> @@ -178,8 +178,7 @@ static ssize_t read_vmcore(struct file *
>          	return -EINVAL;
>  
>  	while (buflen) {
> -		if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
> -			tsz = buflen;
> +		tsz = max_t(size_t, buflen, PAGE_SIZE - (start & ~PAGE_MASK));
>  
>  		/* Calculate left bytes in current memory segment. */
>  		nr_bytes = (curr_m->size - (start - curr_m->paddr));
> _
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