linux-kernel - Re: [PATCH 5/5] tun: vringfd xmit support.

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Message-ID: <6bc632150804181101i701f220an20dddf54389be273@mail.gmail.com>
Date:	Fri, 18 Apr 2008 23:31:29 +0530
From:	"pradeep singh rautela" <rautelap@...il.com>
To:	"Ray Lee" <ray-lk@...rabbit.org>
Cc:	"Rusty Russell" <rusty@...tcorp.com.au>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Max Krasnyansky" <maxk@...lcomm.com>,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH 5/5] tun: vringfd xmit support.

On Fri, Apr 18, 2008 at 7:55 PM, Ray Lee <ray-lk@...rabbit.org> wrote:
> On Fri, Apr 18, 2008 at 4:46 AM, pradeep singh rautela
>  <rautelap@...il.com> wrote:
>  >
>  > On Fri, Apr 18, 2008 at 10:13 AM, Rusty Russell <rusty@...tcorp.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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