linux-kernel - Re: [PATCH] include: mman: Use bool instead of int for the return value of arch_validate

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Message-ID: <57852093.1090909@emindsoft.com.cn>
Date:	Wed, 13 Jul 2016 00:53:39 +0800
From:	Chen Gang <chengang@...ndsoft.com.cn>
To:	Michael Ellerman <mpe@...erman.id.au>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	akpm@...ux-foundation.org, benh@...nel.crashing.org,
	paulus@...ba.org
CC:	tglx@...utronix.de, mingo@...nel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	Chen Gang <gang.chen.5i5j@...il.com>
Subject: Re: [PATCH] include: mman: Use bool instead of int for the return
 value of arch_validate_prot

On 7/12/16 12:20, Michael Ellerman wrote:
> Chen Gang <chengang@...ndsoft.com.cn> writes:
> 
>> On 7/11/16 07:47, Dave Hansen wrote:
>>> On 07/09/2016 09:29 AM, chengang@...ndsoft.com.cn wrote:
>>>> -static inline int arch_validate_prot(unsigned long prot)
>>>> +static inline bool arch_validate_prot(unsigned long prot)
>>>>  {
>>>>  	if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM | PROT_SAO))
>>>> -		return 0;
>>>> -	if ((prot & PROT_SAO) && !cpu_has_feature(CPU_FTR_SAO))
>>>> -		return 0;
>>>> -	return 1;
>>>> +		return false;
>>>> +	return (prot & PROT_SAO) == 0 || cpu_has_feature(CPU_FTR_SAO);
>>>>  }
>>>>  #define arch_validate_prot(prot) arch_validate_prot(prot)
>>>
>>> Please don't do things like this.  They're not obviously correct and
>>> also have no obvious benefit.  You also don't mention why you bothered
>>> to alter the logical structure of these checks.
>>>
>>
>> For all cases, bool is equal or a little better than int, and they are
>> equal in our case (2 final outputs are same). So for me, it may belong
>> to trivial patch, which can be skipped by the normal patch maintainers.
>>
>> As a 'trivial' patch:
>>
>>  - For a pure Boolean function, bool return value is more readable than
>>    int.
> 
> Agreed.
> 
> Please send a patch that does that and only that.
> 

OK, thanks.

After check the assembly output, for some cases, merging 3 lines to 1
line may be a little more readable, but compiler will generate a little
bad output code.

I shall send patch v2 for it within this weekend.

Thanks.
-- 
Chen Gang (陈刚)

Managing Natural Environments is the Duty of Human Beings.