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From: Daniel Phillips <phillips@arcor.de>
To: <imran.badr@cavium.com>, "'Andrew Morton'" <akpm@digeo.com>
Subject: Re: Calculating kernel logical address ..
Date: Mon, 9 Sep 2002 21:06:18 +0200
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On Monday 09 September 2002 20:49, Imran Badr wrote:
> > You can obtain this info by walking the user's pagetables with
> > get_user_pages().  That give `struct page' pointers, with which
> > all things are possible.
> 
> >As long as you can be sure they won't spontaneously vanish on you.
> 
> >--
> >Daniel
> >-
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> 
> down(&current->mm->mmap_sem) would help.

Not for anon pages, and how do you know whether it's anon or not before
looking at the page, which may be free by the time you look at it?
In other words, mm->page_table_lock is the one, because it's required
for unmapping a pte, and any mapped page will be forced to hold a count
increment until it gets past that lock.  Without this lock, the results
of pte_page are unstable.

-- 
Daniel
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