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To: Gregory Giguashvili <Gregoryg@ParadigmGeo.com>
Cc: "'Jesse Pollard'" <pollard@tomcat.admin.navo.hpc.mil>,
       "Linux Kernel (E-mail)" <linux-kernel@vger.kernel.org>
Subject: Re: O_SYNC option doesn't work (2.4.18-3)
References: <EE83E551E08D1D43AD52D50B9F511092E114E4@ntserver2>
From: Trond Myklebust <trond.myklebust@fys.uio.no>
Date: 08 Aug 2002 15:42:30 +0200
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>>>>> " " == Gregory Giguashvili <Gregoryg@ParadigmGeo.com> writes:

     > When the writer closes the file, how do you make the readers
     > see the latest changes (assuming that you always open/close
     > files per transaction type).

There is a convention amongst NFS clients that each client will always
flush *all* changes to the server upon close(), and it will always
check the file attributes upon a call to open() (and if the mtime or
file size have changed, one flushes the page cache).
This suffices to guarantee file cache consistency *provided* that only
one client opens the file at any given time.

If locking is used, all changes are flushed to the server upon
taking/releasing a lock, and the page cache is guaranteed to get
flushed upon taking a lock.

Cheers,
  Trond
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