Re: infinite loop? with mmap, nfs, pwrite, O_DIRECT

From: Andrew Morton
Date: Mon Nov 21 2005 - 19:09:00 EST

Trond Myklebust <trond.myklebust@xxxxxxxxxx> 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the direct-io write is about to make that pagecache out-of-date.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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