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

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Message-ID: <jeire2nnik.fsf@sykes.suse.de>
Date:	Fri, 16 Feb 2007 16:13:55 +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:

> 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.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@...e.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."
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