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

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Message-ID: <20071217132802.GD1870@elte.hu>
Date:	Mon, 17 Dec 2007 14:28:02 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jan Beulich <jbeulich@...ell.com>
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	Andi Kleen <ak@...e.de>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] x86: fix ref-counting bug in change_page_attr()


* Jan Beulich <jbeulich@...ell.com> 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.

hm, does this patch fix any real bug seen live? (if yes then do you have 
links to it, etc?) It would be a v2.6.24 fix in theory but it looks too 
dangerous for that. So i've queued it up for v2.6.25, for the time 
being.

	Ingo
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