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Date: Fri, 22 Aug 2003 10:36:34 -0700
From: "David S. Miller" <davem@redhat.com>
To: Matthew Wilcox <willy@debian.org>
Cc: willy@debian.org, James.Bottomley@SteelEye.com,
       linux-kernel@vger.kernel.org, parisc-linux@lists.parisc-linux.org,
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Subject: Re: [parisc-linux] Re: Problems with kernel mmap (failing
 tst-mmap-eofsync in glibc on parisc)
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On Fri, 22 Aug 2003 18:41:03 +0100
Matthew Wilcox <willy@debian.org> wrote:

> Uhm.  So what happens when the user has stored into the page and now
> the kernel wants to read from it?  There's still data in the cache for
> the user mapping that's non-coherent with the kernel mapping.

I see.  This causes the page cache read flush_dcache_page() call
not to trigger.

I was very confused by the fact that this bug was explained by
saying that "the shared mmap list that flush_dcache_page() checks".

So the idea is that VM_SHARED should be set based upon whether
we mmap() the thing writable _not_ whether the open() was done
with write permission enabled.

Yes, I agree with that.