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

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Message-ID: <Pine.LNX.4.64.0702161157450.32716@CPE00045a9c397f-CM001225dbafb6>
Date:	Fri, 16 Feb 2007 11:58:57 -0500 (EST)
From:	"Robert P. J. Day" <rpjday@...dspring.com>
To:	Richard Knutsson <ricknu-0@...dent.ltu.se>
cc:	Andreas Schwab <schwab@...e.de>,
	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

On Fri, 16 Feb 2007, Richard Knutsson wrote:

> 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.

i think the above change is fine.  as long as the final, overall
semantics of the condition are identical, then there's no problem.

rday

-- 
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Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

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