linux-kernel - Re: [PATCH 3/4] add replace_page(): change the page pte is pointing to.

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Date:	Tue, 14 Apr 2009 15:09:25 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Izik Eidus <ieidus@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	linux-mm@...ck.org, avi@...hat.com, aarcange@...hat.com,
	chrisw@...hat.com, mtosatti@...hat.com, hugh@...itas.com,
	kamezawa.hiroyu@...fujitsu.com, ieidus@...hat.com
Subject: Re: [PATCH 3/4] add replace_page(): change the page pte is pointing
 to.

On Thu,  9 Apr 2009 06:58:40 +0300
Izik Eidus <ieidus@...hat.com> wrote:

> replace_page() allow changing the mapping of pte from one physical page
> into diffrent physical page.

At a high level, this is very similar to what page migration does.  Yet
this implementation shares nothing with the page migration code.

Can this situation be improved?

> this function is working by removing oldpage from the rmap and calling
> put_page on it, and by setting the pte to point into newpage and by
> inserting it to the rmap using page_add_file_rmap().
> 
> note: newpage must be non anonymous page, the reason for this is:
> replace_page() is built to allow mapping one page into more than one
> virtual addresses, the mapping of this page can happen in diffrent
> offsets inside each vma, and therefore we cannot trust the page->index
> anymore.
> 
> the side effect of this issue is that newpage cannot be anything but
> kernel allocated page that is not swappable.
> 

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