[PATCH 02/18] xstat: Add a pair of system calls to make extended file stats available [ver #6]

J. Bruce Fields bfields at fieldses.org
Fri Jul 30 12:38:19 MDT 2010

On Thu, Jul 29, 2010 at 09:04:01AM +1000, Neil Brown wrote:
> On Wed, 28 Jul 2010 18:28:02 +0100
> David Howells <dhowells at redhat.com> wrote:
> > Neil Brown <neilb at suse.de> wrote:
> > 
> > > ctime and mtime have real cache-coherence semantics which require them being
> > > updated by the kernel (whether the cache is on an NFS client, in a backup
> > > archive, or in a .o translation of a .c file).
> > 
> > So does creation time, at least for CIFS caching.  Creation time has potential
> > for spotting when the object at a pathname has changed for something else,
> > given the lack of inode number and inode generation from windows servers.
> > Creation time gives us one more datum to use.
> This justifies for me why a CIFS client would want to extract the
> creation-time from the CIFS protocol, but not why you want to expose it via a
> generic interface.
> The kernel/filesystem doesn't need to maintain creation-time to meet this
> need, only the CIFS server needs to maintain it

For what it's worth, the NFSv4 server would also export creation time if
we had it.


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