Re: [KJ] [PATCH] is_power_of_2 in ia64mm

From: Richard Knutsson
Date: Fri Feb 16 2007 - 11:40:46 EST

Andreas Schwab wrote:
Richard Knutsson <ricknu-0@xxxxxxxxxxxxxx> writes:
Andreas Schwab wrote:
Richard Knutsson <ricknu-0@xxxxxxxxxxxxxx> 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

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