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Date: Mon, 10 Mar 2003 12:07:43 +0000 (GMT)
From: Hugh Dickins <hugh@veritas.com>
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To: Ed Tomlinson <tomlins@cam.org>
cc: Dave McCracken <dmccr@us.ibm.com>, Andrew Morton <akpm@digeo.com>,
       linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] nonlinear oddities
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On Sat, 8 Mar 2003, Ed Tomlinson wrote:
> Dave McCracken wrote:
> > --On Thursday, March 06 2003, Hugh Dickins wrote:
> > 
> >> Now I think about it more, install_page's SetPageAnon is not good at all.
> >> That (unlocked) page may already be mapped into other vmas as a shared
> >> file page, non-zero mapcount, we can't suddenly switch it to Anon
> >> (pte_chained) without doing the work to handle that case.
> > 
> > Ouch.  You're right.  I'll go stare at it for awhile and see if any
> > solutions jump out at me.  I suppose at worst I could write a function to
> > convert an object page to use pte_chains, but it'd be nice if that weren't
> > necessary.
> 
> Does this look like the above happening?  

I very much doubt it.  You'd have to be running an application using Ingo's
new (since 2.5.46) remap_file_pages system call to suffer from Dave's ouch
e.g. something like an experimental version of a major database app.  That
said, I've given no thought to what that ouch might look like in practice.

Hugh

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