Date: Tue, 13 May 2003 16:56:06 -0700
From: Andrew Morton <akpm@digeo.com>
To: green@namesys.com, jdike@karaya.com, roland@redhat.com,
       linux-kernel@vger.kernel.org,
       user-mode-linux-devel@lists.sourceforge.net
Subject: Re: build problems on architectures where FIXADDR_* stuff is not
 constant
Message-Id: <20030513165606.25212829.akpm@digeo.com>
In-Reply-To: <20030513134620.3dafeaf3.akpm@digeo.com>
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	<20030513134620.3dafeaf3.akpm@digeo.com>
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Andrew Morton <akpm@digeo.com> wrote:
>
> The new code in get_user_pages() is rather rude - it's returning a
> statically allocated VMA which isn't in the VMA tree - the caller (who
> holds mmap_sem()) could reasonably expect that the VMA can be located via
> find_vma(), or removed from the tree or whatever.  But it cannot.
> 
> I think it needs to be redone.  Either by stuffing a VMA into every
> process's mm which describes the fixmap area, or by failing
> get_user_pages() if the caller has passed in a non-NULL `vmas' and is
> requesting access to the fixmap area.

Or by lazily instantiating the fixmap VMA within get_user_pages().  So if
someone happens to want to access the fixmap, that's when the vma which
describes it gets stuffed into the tree.

That'd require that get_user_pages() be called under down_write(mmap_sem).

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