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SubjectRe: [PATCH 5/5] tun: vringfd xmit support.
On Fri, Apr 18, 2008 at 7:55 PM, Ray Lee <ray-lk@madrabbit.org> wrote:
> On Fri, Apr 18, 2008 at 4:46 AM, pradeep singh rautela
> <rautelap@gmail.com> wrote:
> >
> > On Fri, Apr 18, 2008 at 10:13 AM, Rusty Russell <rusty@rustcorp.com.au> wrote:
>
> > > + /* How many pages will this take? */
> > > + npages = 1 + (base + len - 1)/PAGE_SIZE - base/PAGE_SIZE;
> >
> > Hi Rusty,
> > A trivial suggestion, how about
> > npages = 1+(len -1)/PAGE_SIZE ?
>
> That's not the same. In particular, his version accounts for the
> fractional page at the beginning, while yours doesn't.

Oh thanks for correcting me Ray. :)
>
> While it's tempting to use algebra to simplify things, it's not safe
> to do so when the expression involves division over the integers. The
> only care-free integer math in a computer is subtraction and ++.

I stand corrected.

Sorry for noise.

Thanks,
--
Pradeep Singh Rautela
http://eagain.wordpress.com
http://emptydomain.googlepages.com


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