1 From: Mingming Cao <mcao@us.ibm.com>
2 Subject: Re: [RFC][PATCH 06/10] cifs: define inode-level cache object and
4 Date: Fri, 25 Jun 2010 17:52:24 -0700
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14 Cc: linux-cifs@vger.kernel.org, Jeff Layton <jlayton@redhat.com>,
15 samba-technical@lists.samba.org, linux-kernel@vger.kernel.org,
16 David Howells <dhowells@redhat.com>, linux-fsdevel@vger.kernel.org,
17 "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
18 To: Steve French <smfrench@gmail.com>
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83 Steve French <smfrench@gmail.com> wrote on 06/25/2010 04:05:30 PM:
85 > Steve French <smfrench@gmail.com>
90 > Jeff Layton <jlayton@samba.org>, "Aneesh Kumar K.V"
91 > <aneesh.kumar@linux.vnet.ibm.com>, Mingming Cao/Beaverton/IBM@IBMUS
95 > David Howells <dhowells@redhat.com>, Suresh Jayaraman
96 > <sjayaraman@suse.de>, linux-cifs@vger.kernel.org, linux-
97 > fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, samba-
98 > technical@lists.samba.org, Jeff Layton <jlayton@redhat.com>
102 > Re: [RFC][PATCH 06/10] cifs: define inode-level cache object and
105 > On Fri, Jun 25, 2010 at 5:26 PM, Jeff Layton <jlayton@samba.org> wrot=
108 > > On Fri, 25 Jun 2010 22:46:38 +0100
109 > > David Howells <dhowells@redhat.com> wrote:
111 > > > Jeff Layton <jlayton@samba.org> wrote:
113 > > > > Looks like it mostly uses the ctime. IMO, the mtime would be a
115 > > > > choice since it changes less frequently, but I don't guess that=
117 > > > > matters very much.
119 > > > I'd've thought mtime changes more frequently since that's
120 > altered when data is
121 > > > written. =A0ctime is changed when attributes are changed.
124 > > IIUC, updating mtime for a write is also an attribute change, and t=
126 > > affects ctime. According to the stat(2) manpage:
128 > > =A0 =A0 =A0 The field st_ctime is changed by writing or by setting
129 > =A0inode =A0informa-
130 > > =A0 =A0 =A0 tion (i.e., owner, group, link count, mode, etc.).
132 > > > Note that Ext4 appears to have a file creation time field in its
134 > > > (struct ext4_inode::i_crtime[_extra]). =A0Can Samba be made to us=
139 > > Is it exposed to userspace in any (standard) way? It would be handy=
141 > > have that. While we're wishing...it might also be nice to have a
142 > > standard way to get at the i_generation from userspace too.
145 > Yes - I have talked with MingMing and Aneesh about those (NFS may
146 > someday be able to use those too).=A0 An obstacle in the past had bee=
148 > that samba server stores its own fake creation time in an ndr encoded=
150 > xattr which complicates things.
153 > Xattr or other way to get at birth time?
158 The ext4 file creation time only accesable from the kernel at the mome=
160 There were discussion
161 to make this information avaliable via xattr before, but was rejected,
163 agree that making this info avalibele via stat() is more standard. Howe=
165 modifying stat() would imply
166 big interface change. thus no action has been taken yet.