From: Trond Myklebust <trond.myklebust@fys.uio.no>
Subject: RE: mtime not updated in client cache?
Date: Fri, 09 Dec 2005 11:10:36 -0500
Message-ID: <1134144637.8007.56.camel@lade.trondhjem.org>
References: <044B81DE141D7443BCE91E8F44B3C1E201332862@exsvl02.hq.netapp.com>
Mime-Version: 1.0
Content-Type: text/plain
Cc: Peter Staubach <staubach@redhat.com>,
	Vince Busam <vbusam@google.com>, nfs@lists.sourceforge.net
To: "Lever, Charles" <Charles.Lever@netapp.com>
In-Reply-To: <044B81DE141D7443BCE91E8F44B3C1E201332862@exsvl02.hq.netapp.com>
Sender: nfs-admin@lists.sourceforge.net
Errors-To: nfs-admin@lists.sourceforge.net

On Fri, 2005-12-09 at 07:56 -0800, Lever, Charles wrote:
> do you need to prevent writes *during* the stat() call?  or do you just
> want to make sure that any writes that happened *before* the stat() call
> have the intended side-effects on the file size and mtime?  that might
> be worth a comment or two.

I cannot see that we would want strict serialisation of stat() and
write(). That would give rise to an even worse performance hit.
If someone calls write() while we're in stat() then the outcome should
be indeterminate, just as it is for local filesystems.

> are you flushing dirty mmap'd data too?  or can this be skipped until
> msync() time?

There appears to be no SuS requirement to do so: the description of
msync() says that you are only required to update m/ctime if writes are
actually initiated.

  http://www.opengroup.org/onlinepubs/009695399/toc.htm

> and now that you have added a "flush but don't commit" flag to
> nfs_sync_file, maybe we might consider using that (optionally) at file
> close() time, like some other NFS client implementations do.  :^)

Nope.

Cheers,
  Trond


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