Date: Mon, 21 Nov 2005 16:09:13 -0800
From: Andrew Morton <akpm@osdl.org>
To: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: theonetruekenny@yahoo.com, cel@citi.umich.edu,
       linux-kernel@vger.kernel.org
Subject: Re: infinite loop? with mmap, nfs, pwrite, O_DIRECT
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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the direct-io write is about to make that pagecache out-of-date.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.

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