linux-kernel - Re: [KJ] [PATCH] is_power_of

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Message-ID: <45D5D47F.3000303@student.ltu.se>
Date:	Fri, 16 Feb 2007 16:57:51 +0100
From:	Richard Knutsson <ricknu-0@...dent.ltu.se>
To:	Andreas Schwab <schwab@...e.de>
CC:	Vignesh Babu BM <vignesh.babu@...ro.com>,
	Kernel Janitors List <kernel-janitors@...ts.osdl.org>,
	linux-mm@...ck.org, tony.luck@...el.com,
	linux-ia64@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [KJ] [PATCH] is_power_of_2 in ia64mm

Andreas Schwab wrote:
> Richard Knutsson <ricknu-0@...dent.ltu.se> writes:
>
>   
>> Vignesh Babu BM wrote:
>>     
>>> @@ -175,7 +176,7 @@ static int __init hugetlb_setup_sz(char *str)
>>>  		tr_pages = 0x15557000UL;
>>>   	size = memparse(str, &str);
>>> -	if (*str || (size & (size-1)) || !(tr_pages & size) ||
>>> +	if (*str || !is_power_of_2(size) || !(tr_pages & size) ||
>>>  		size <= PAGE_SIZE ||
>>>  		size >= (1UL << PAGE_SHIFT << MAX_ORDER)) {
>>>  		printk(KERN_WARNING "Invalid huge page size specified\n");
>>>
>>>   
>>>       
>> As we talked about before; is this really correct? !is_power_of_2(0) ==
>> true while (0 & (0-1)) == 0.
>>     
>
> size == 0 is also covered by the next two conditions, so the overall value
> does not change.
>   
Yes, but is it meant to state that 'size' is not a power of two? 
Otherwise, imho, it should be left as-is.

Richard Knutsson

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