Subject: Re: infinite loop? with mmap, nfs, pwrite, O_DIRECT
From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Andrew Morton <akpm@osdl.org>
Cc: theonetruekenny@yahoo.com, cel@citi.umich.edu,
       linux-kernel@vger.kernel.org
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Date: Mon, 21 Nov 2005 19:18:50 -0500
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On Mon, 2005-11-21 at 16:09 -0800, Andrew Morton wrote:
> Trond Myklebust <trond.myklebust@fys.uio.no> wrote:
> >
> > The only difference I can see between the two paths is the call to
> >  unmap_mapping_range(). What effect would that have?
> 
> It shoots down any mapped pagecache over the affected file region.  Because
> the direct-io write is about to make that pagecache out-of-date.  If the
> application tries to use that data again it'll get a major fault and will
> re-read the file contents.

I assume then, that this couldn't be the cause of the
invalidate_inode_pages() failing to complete? Unless there is some
method to prevent applications from faulting in the page while we're
inside generic_file_direct_IO(), then the same race would be able to
occur there.

Cheers,
  Trond

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