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Date: Sat, 23 Aug 2003 15:51:27 -0700
From: "David S. Miller" <davem@redhat.com>
To: James Bottomley <James.Bottomley@SteelEye.com>
Cc: hugh@veritas.com, willy@debian.org, linux-kernel@vger.kernel.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 23 Aug 2003 17:21:21 -0500
James Bottomley <James.Bottomley@SteelEye.com> wrote:

> On Sat, 2003-08-23 at 16:43, David S. Miller wrote:
> > On 22 Aug 2003 20:09:30 -0500
> > James Bottomley <James.Bottomley@SteelEye.com> wrote:
> > 
> > >        MAP_PRIVATE
> > >                   Create a private copy-on-write mapping.  Stores
> > >                   to the region do not affect the original  file.
> > >                   It  is  unspecified whether changes made to the
> > >                   file after the mmap call  are  visible  in  the
> > >                   mapped region.
...
> Could you elaborate some more?  I agree that the MAP_PRIVATE mapping may
> not see cpu1's write because of cache incoherencies (but that's what I
> believe is covered by the `unspecified' bit of the MAP_PRIVATE
> definition above).

Ok.  Let me think about this a bit more.

The safest solution for parisc, meanwhile, would be to walk the
non-shared mmap list checking for any instance of the VM_MAYSHARE bit
being set.