From owner-freebsd-hackers@FreeBSD.ORG Mon Sep 8 17:09:09 2014 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 19DBDDB3; Mon, 8 Sep 2014 17:09:09 +0000 (UTC) Received: from bigwig.baldwin.cx (bigwig.baldwin.cx [IPv6:2001:470:1f11:75::1]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id E2B531BD8; Mon, 8 Sep 2014 17:09:08 +0000 (UTC) Received: from ralph.baldwin.cx (pool-173-70-85-31.nwrknj.fios.verizon.net [173.70.85.31]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id B11E6B962; Mon, 8 Sep 2014 13:09:07 -0400 (EDT) From: John Baldwin To: freebsd-hackers@freebsd.org Subject: Re: O_XATTR support in FreeBSD? Date: Mon, 08 Sep 2014 11:52:50 -0400 Message-ID: <14246348.Ehh2xp5iLB@ralph.baldwin.cx> User-Agent: KMail/4.10.5 (FreeBSD/10.0-STABLE; KDE/4.10.5; amd64; ; ) In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (bigwig.baldwin.cx); Mon, 08 Sep 2014 13:09:07 -0400 (EDT) Cc: Rick Macklem , Cedric Blancher , Richard Yao , Pedro Giffuni , Lionel Cons , Jordan Hubbard X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 08 Sep 2014 17:09:09 -0000 On Friday, September 05, 2014 04:24:02 PM Lionel Cons wrote: > On 1 December 2013 23:05, Lionel Cons wrote: > > On 27 November 2013 05:52, Tim Kientzle wrote: > >> On Nov 26, 2013, at 1:51 AM, Cedric Blancher wrote: > >>> 5. Support for tar and pax is already there. Its described in > >>> Solaris's fsattr man page, they use a extended header with filename > >>> /dev/null (to prevent older tar versions from tripping over the new > >>> headers) and then have a named attribute header which describes the > >>> attributes names and flags. > >> > >> There are quite a few alternative approaches for storing > >> extended attributes in tar and pax files. > > > > But this discussion is *not* about extended attributes, this > > discussion is about Alternate Data Streams. Unfortunately the O_XATTR > > discussion somehow started to cover the Linux "extended attribute > > system", which is utterly useless in the intended use cases (as said, > > no access through normal POSIX read(), write(), mmap(), no unlimited > > size, no sparse data support (aka SEEK_HOLE, SEEK_DATA) etc etc). > > > > Lionel > > What is the status of O_XATTR (alias alternate data stream support) in > FreeBSD? We run more and more into the trouble that these kind of > streams are in use but cannot be accessed or processed on FreeBSD. I don't think anyone is even looking at it. I didn't quite follow the earlier mail about this and some concrete examples probably would help. Can you do 'open("/path/to/foo@forkname", O_XATTR)' to open the "forkname" fork of the "/path/to/foo" file? -- John Baldwin