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Re: [PATCH] remap_file_pages needs to check for cache coherency

To: willy@linux.intel.com
Subject: Re: [PATCH] remap_file_pages needs to check for cache coherency
From: David Miller <davem@davemloft.net>
Date: Fri, 27 Dec 2013 13:48:14 -0500 (EST)
Cc: linux-mm@kvack.org, sparclinux@vger.kernel.org, linux-parisc@vger.kernel.org, linux-mips@linux-mips.org
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From: Matthew Wilcox <willy@linux.intel.com>
Date: Fri, 27 Dec 2013 13:00:18 -0500

> It seems to me that while (for example) on SPARC, it's not possible to
> create a non-coherent mapping with mmap(), after we've done an mmap,
> we can then use remap_file_pages() to create a mapping that no longer
> aliases in the D-cache.
> 
> I have only compile-tested this patch.  I don't have any SPARC hardware,
> and my PA-RISC hardware hasn't been turned on in six years ... I noticed
> this while wandering around looking at some other stuff.

I suppose this is needed, but only in the case where the mapping is
shared and writable, right?  I don't see you testing those conditions,
but with them I'd be OK with this change.


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