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

To: Jan Beulich <JBeulich@xxxxxxxxxx>, Olaf Hering <olaf@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 1 of 5] xentrace: fix t_info_pages calculation for the default case
From: Keir Fraser <keir.xen@xxxxxxxxx>
Date: Wed, 23 Mar 2011 10:22:16 +0000
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, George Dunlap <george.dunlap@xxxxxxxxxx>
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Thread-topic: [Xen-devel] [PATCH 1 of 5] xentrace: fix t_info_pages calculation for the default case
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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).

That would make sense to me. The suggested change in the patch series looks

 -- Keir

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