Re: [KJ] [PATCH] is_power_of_2 in ia64mm

Richard Knutsson
2007-02-16T16:40:25Z

Andreas Schwab wrote:
> Richard Knutsson <ricknu-0@student.ltu.se> writes:
>
>> Andreas Schwab wrote:
>>
>>> Richard Knutsson <ricknu-0@student.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()? It has not been implemented (yet?) but
been discussed. It ended by concluding that is_power_of_2() should be
fixed up first and then we can see about it.
And as I stated before; !is_power_of_2(size) != (size & (size-1))! It
may be a bug but then we have to be sure it is suppose to be the power of 2.

Richard Knutsson