Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762439Ab0HGCmq (ORCPT ); Fri, 6 Aug 2010 22:42:46 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:65170 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752766Ab0HGCmm convert rfc822-to-8bit (ORCPT ); Fri, 6 Aug 2010 22:42:42 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=mpU5jFedN0WYrPJOp+ZN+kBs7wQZ+zB66zEzHHYe3QVoTQqXKnM7/W3PBVyoEK5eX5 p5K6Wcfd1h5L2oQHZ04z4DgZ+52DTfh2meXG6V5LjF/SoIXNf24Inby1tBYLeajgsNWf E8Fu11l3yiF9ERvG1Ah65G3+7QURZP94RiXks= MIME-Version: 1.0 In-Reply-To: <20100807102901.6a0b53e7@notabene> References: <20100715021709.5544.64506.stgit@warthog.procyon.org.uk> <20100715021712.5544.44845.stgit@warthog.procyon.org.uk> <30448.1279800887@redhat.com> <1280524978.2452.9.camel@segv.aura.of.mankind> <20100801092529.5e6ba0e0@corrin.poochiereds.net> <20100805235218.GB31233@jeremy-laptop> <20100806133836.49757af9@notabene> <20100807093057.7683bedd@notabene> <20100807102901.6a0b53e7@notabene> Date: Fri, 6 Aug 2010 21:42:41 -0500 Message-ID: Subject: Re: [PATCH 02/18] xstat: Add a pair of system calls to make extended file stats available [ver #6] From: Steve French To: Neil Brown Cc: Jeremy Allison , Jeff Layton , utz lehmann , Linus Torvalds , Volker.Lendecke@sernet.de, David Howells , Jan Engelhardt , linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org, samba-technical@lists.samba.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, linux-fsde@jasper.es Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4249 Lines: 87 On Fri, Aug 6, 2010 at 7:29 PM, Neil Brown wrote: > On Fri, 6 Aug 2010 18:58:42 -0500 > Steve French wrote: > >> On Fri, Aug 6, 2010 at 6:30 PM, Neil Brown wrote: >> > On Thu, 5 Aug 2010 22:55:06 -0500 >> > Steve French wrote: >> > >> >> On Thu, Aug 5, 2010 at 10:38 PM, Neil Brown wrote: >> >> > On Thu, 5 Aug 2010 16:52:18 -0700 >> >> > Jeremy Allison wrote: >> >> >> >> >> Don't add it as an EA. It's *not* an EA, it's a timestamp. >> >> > >> >> > I'm curious. ?Why do you particularly care what interface the kernel uses to >> >> > provide you with access to this attribute? >> >> > >> >> > And given that it is an attribute that is not part of 'POSIX' or "UNIX", it >> >> > would seem to be an extension - an extended attribute. >> >> > As the Linux kernel does virtually nothing with this attribute except provide >> >> > access, it seems to be a very different class of thing to other timestamps. >> >> > Surely it is simply some storage associated with a file which is capable of >> >> > storing a timestamp, which can be set or retrieved by an application, and >> >> > which happens to be initialised to the current time when a file is created. >> >> > >> >> > Yes, to you it is a timestamp. ?But to Linux it is a few bytes of >> >> > user-settable metadata. ?Sounds like an EA to me. >> >> > >> >> > Or do you really want something like BSD's 'btime' which as I understand it >> >> > cannot be set. ?Would that be really useful to you? >> >> >> >> Obviously the cifs and SMB2 protocols which ?Samba server support can >> >> ask the server to set the create time of a file (this is handled >> >> through xattrs today along with the "dos attribute" flags such as >> >> archive/hidden/system), but certainly it is much more common (and >> >> important) to read the creation time of an existing file. >> >> >> > >> > Just a point of clarification - when you say it is common and important to be >> > able to read the creation time on an existing file, and you still talking in >> > the context of cifs/smb windows compatibility, or are you talking in the >> > broader context? >> > If you are referring to a broader context could be please give more details >> > because I have not heard any mention of any real value of creation-time out >> > side of window interoperability - have such a use clearly documented would >> > assist the conversation I think. >> > >> > If on the other hand you are just referring the the windows interoperability >> > context ... given that you have to read an EA if the create-time has been >> > changed, you will always have to read and EA so having something else is >> > pointless ... or I'm missing something. >> >> There are other cases, less common than cifs and smb2. ? One >> that comes to mind is NFS version 4, but there are a few other >> cases that I have heard of (backup/archive applications). >> The RFC recommends that servers return attribute 50 (creation >> time). ?See below text: >> >> ? ?time_create ? ? ? ? 50 ? nfstime4 ? ? ? R/W ? ? ?The time of creation >> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? of the object. ?This >> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? attribute does not >> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? have any relation to >> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? the traditional UNIX >> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? file attribute >> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? "ctime" or "change >> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? time". > > I really don't think NFSv4 is a separate justification. ?I'm fairly sure > that attribute was only including in NFSv4 for enhanced Windows > compatibility (windows interoperation was a big issue during the protocol > development). Perhaps also useful for MacOS (and other BSD), not just Windows, although MacOS may use cifs more often than nfs. -- Thanks, Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/