linux-kernel - Re: [PATCH] x86: fix ref-counting bug in change_page

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Message-Id: <47624F26.76E4.0078.0@novell.com>
Date:	Fri, 14 Dec 2007 08:38:46 +0000
From:	"Jan Beulich" <jbeulich@...ell.com>
To:	"Jeremy Fitzhardinge" <jeremy@...p.org>
Cc:	<tglx@...utronix.de>, <mingo@...hat.com>,
	"Andi Kleen" <ak@...e.de>, <linux-kernel@...r.kernel.org>,
	<hpa@...or.com>
Subject: Re: [PATCH] x86: fix ref-counting bug in change_page_attr()

>>> Jeremy Fitzhardinge <jeremy@...p.org> 14.12.07 08:12 >>>
>Jan Beulich wrote:
>> When either calling change_page_attr() with the default attributes
>> pages in the direct mapping have and a page's attributes already were
>> set to the default or when changing the attributes from one non-default
>> value to another, the reference counting broke, leading to either
>> premature restoration of a large page or missing the opportunity to do
>> so.
>>
>> At the same time, make __PHYSICAL_MASK_SHIFT on 64-bits the value it
>> architecturally ought to have.
>>   
>
>Could you put this in a separate patch?  I have a bunch of page*.h and
>pgtable*.h refactoring patches which will conflict with this.

I doesn't seem logical to do so: The patch needs to introduce the definitions
for 32-bits (in order to define pte_pgprot()), and not doing the adjustment
for 64-bits here means (a) becoming inconsistent and (b) the pte_pgprot()
there would be incorrect. So such a split out patch would need to be a pre-
requisite to the one here, which wouldn't help avoiding the collisions with
your unification patches.

Jan

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