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Subject: Re: ext4 features
From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Bill Davidsen <davidsen@tmr.com>, Theodore Tso <tytso@mit.edu>,
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       LKML <linux-kernel@vger.kernel.org>
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Date: Wed, 05 Jul 2006 15:33:53 -0400
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On Wed, 2006-07-05 at 08:59 -0400, J. Bruce Fields wrote:
> On Wed, Jul 05, 2006 at 08:24:29AM -0400, Bill Davidsen wrote:
> > Theodore Tso wrote:
> > >Some of the ideas which have been tossed about include:
> > >
> > >	* nanosecond timestamps, and support for time beyond the 2038
> > 
> > The 2nd one is probably more urgent than the first. I can see a general 
> > benefit from timestamp in ms, beyond that seems to be a specialty 
> > requirement best provided at the application level rather than the bits 
> > of a trillion inodes which need no such thing.
> 
> What's urgently needed for NFS (and I suspect for most other
> applications demanding higher timestamps) isn't really nanosecond
> precision so much as something that's guaranteed to increase whenever
> the file changes.

NFS doesn't necessarily require monotonicity either. The only real
requirement that knfsd has is that the timestamp needs to change every
time the file data (mtime+ctime) and/or metadata (ctime only) is
changed.

Applications like 'make' OTOH, probably would be happier if the
timestamps are guaranteed to be monotonic.

Cheers,
  Trond