linux-kernel - Re: fuse, get_user_pages, flush_anon_page, aliasing caches and all that again

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Message-ID: <20061222084318.GA5132@flint.arm.linux.org.uk>
Date:	Fri, 22 Dec 2006 08:43:18 +0000
From:	Russell King <rmk+lkml@....linux.org.uk>
To:	Randolph Chung <randolph@...sq.org>
Cc:	Miklos Szeredi <miklos@...redi.hu>, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: fuse, get_user_pages, flush_anon_page, aliasing caches and all that again

On Fri, Dec 22, 2006 at 07:51:34AM +0800, Randolph Chung wrote:
> >I understand now.  I'm not sure how the PARISC implementation can be
> >correct in this light.
> 
> According to cachetlb.txt:
> 
>   void flush_anon_page(struct page *page, unsigned long vmaddr)
>         When the kernel needs to access the contents of an anonymous
>         page, it calls this function (currently only
>         get_user_pages()).  Note: flush_dcache_page() deliberately
>         doesn't work for an anonymous page.  The default
>         implementation is a nop (and should remain so for all coherent
>         architectures).  For incoherent architectures, it should flush
>         the cache of the page at vmaddr in the current user process.
>                                                ^^^^^^^^^^^^^^^^^^^^
> 
> Is the documentation wrong?

Yes.  As I've already explained there is no guarantee that
get_user_pages() is only called to obtain pages for the current
process, and flush_anon_pages() is called irrespective of which
user process is being 'got'.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:
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