linux-kernel - Re: [PATCH] bitops: use the same mechanism for get_count_order[

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Date:   Tue, 26 May 2020 21:57:20 +0000
From:   Wei Yang <richard.weiyang@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Wei Yang <richard.weiyang@...il.com>, akpm@...ux-foundation.org,
        christian.brauner@...ntu.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bitops: use the same mechanism for get_count_order[_long]

On Tue, May 26, 2020 at 10:04:57AM +0300, Andy Shevchenko wrote:
>On Mon, May 25, 2020 at 09:59:58PM +0000, Wei Yang wrote:
>> These two functions share the same logic.
>
>So, same comment. Please, add test first, make sure it works on current kernel,
>then after your patch applied, and send it as a series, thanks!
>
>P.S. W/o test code looks good, but based on my experience I'm very suspicious
>about "small" changes that may lead to big issues. Hope you understand my point.
>

Sure, I see your point.

>> Signed-off-by: Wei Yang <richard.weiyang@...il.com>
>> ---
>>  include/linux/bitops.h | 8 +++-----
>>  1 file changed, 3 insertions(+), 5 deletions(-)
>> 
>> diff --git a/include/linux/bitops.h b/include/linux/bitops.h
>> index 5b5609e81a84..80703ef27aee 100644
>> --- a/include/linux/bitops.h
>> +++ b/include/linux/bitops.h
>> @@ -188,12 +188,10 @@ static inline unsigned fls_long(unsigned long l)
>>  
>>  static inline int get_count_order(unsigned int count)
>>  {
>> -	int order;
>> +	if (count == 0)
>> +		return -1;
>>  
>> -	order = fls(count) - 1;
>> -	if (count & (count - 1))
>> -		order++;
>> -	return order;
>> +	return fls(--count);
>>  }
>>  
>>  /**
>> -- 
>> 2.23.0
>> 
>
>-- 
>With Best Regards,
>Andy Shevchenko
>

-- 
Wei Yang
Help you, Help me