Re: Regression: x86/mm: new _PTE_SWP_SOFT_DIRTY bit conflicts withexisting use

From: Cyrill Gorcunov
Date: Wed Aug 21 2013 - 14:17:41 EST


On Wed, Aug 21, 2013 at 09:25:47PM +0400, Cyrill Gorcunov wrote:
> >
> > However, I do find the use of PTE bits in this way somewhat fragile.
> > What other potential corner cases might still remain that will require
> > further games with PTE bits?
>
> OK, so this is not a bug finally. The problem is that 2 level pte is
> quite small and 7th bit is the only one spare I can use for soft dirty
> tracking when page get swapped out. And swap engine is very depending
> on pte being non-present, so we are on a safe side.

To make it clear: I'm working on patch that won't use pse bit for dirty
page tracking, just give some time to cook it and test.
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