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

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Message-ID: <jeps8am4sr.fsf@sykes.suse.de>
Date:	Fri, 16 Feb 2007 17:43:32 +0100
From:	Andreas Schwab <schwab@...e.de>
To:	Richard Knutsson <ricknu-0@...dent.ltu.se>
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

Richard Knutsson <ricknu-0@...dent.ltu.se> writes:

> Andreas Schwab wrote:
>> Richard Knutsson <ricknu-0@...dent.ltu.se> writes:
>>   
>>> 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?
>>>     
>>
>> What else can it mean?
>>   
> What about !one_or_less_bit()?

Obviously not.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@...e.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
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