linux-kernel - Re: [RFC][PATCH 06/10] cifs: define inode-level cache object and register them

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Message-ID: <20100625182651.36800d06@tlielax.poochiereds.net>
Date:	Fri, 25 Jun 2010 18:26:51 -0400
From:	Jeff Layton <jlayton@...ba.org>
To:	David Howells <dhowells@...hat.com>
Cc:	Suresh Jayaraman <sjayaraman@...e.de>,
	Steve French <smfrench@...il.com>, linux-cifs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	samba-technical@...ts.samba.org
Subject: Re: [RFC][PATCH 06/10] cifs: define inode-level cache object and
 register them

On Fri, 25 Jun 2010 22:46:38 +0100
David Howells <dhowells@...hat.com> wrote:

> Jeff Layton <jlayton@...ba.org> wrote:
> 
> > Looks like it mostly uses the ctime. IMO, the mtime would be a better
> > choice since it changes less frequently, but I don't guess that it
> > matters very much.
> 
> I'd've thought mtime changes more frequently since that's altered when data is
> written.  ctime is changed when attributes are changed.
> 

IIUC, updating mtime for a write is also an attribute change, and that
affects ctime. According to the stat(2) manpage:

       The field st_ctime is changed by writing or by setting  inode  informa-
       tion (i.e., owner, group, link count, mode, etc.).

> Note that Ext4 appears to have a file creation time field in its inode
> (struct ext4_inode::i_crtime[_extra]).  Can Samba be made to use that?
> 

Is it exposed to userspace in any (standard) way? It would be handy to
have that. While we're wishing...it might also be nice to have a
standard way to get at the i_generation from userspace too.

-- 
Jeff Layton <jlayton@...ba.org>
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