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Re: [Xen-devel] [PATCH 1 of 5] xentrace: fix t_info_pages calculation fo

To: Keir Fraser <keir.xen@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 1 of 5] xentrace: fix t_info_pages calculation for the default case
From: Olaf Hering <olaf@xxxxxxxxx>
Date: Wed, 23 Mar 2011 12:20:40 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, George Dunlap <george.dunlap@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>
Delivery-date: Wed, 23 Mar 2011 04:21:21 -0700
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On Wed, Mar 23, Keir Fraser wrote:

> On 23/03/2011 10:12, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
> >>      t_info_pages /= PAGE_SIZE;
> >> -    if ( t_info_pages % PAGE_SIZE )
> >> +    if ( t_info_pages % PAGE_SIZE || t_info_pages == 0 )
> > 
> > While certainly not having a significant effect, to the unsuspecting
> > reader this looks like a bug - is it really meant to be a remainder
> > operation on the *result* of a division (rather than on the original
> > dividend)? Couldn't you just (ab)use PFN_UP() here?
> By which you mean to replace the division and subsequent if statement with
> t_info_pages = PFN_UP(t_info_pages).

I did not know about PFN_UP() until now, using it would work as well.


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