From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02C44C433E0 for ; Wed, 12 Aug 2020 11:18:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C885320829 for ; Wed, 12 Aug 2020 11:18:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="AjXU0dKU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726804AbgHLLSe (ORCPT ); Wed, 12 Aug 2020 07:18:34 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:38000 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726453AbgHLLSe (ORCPT ); Wed, 12 Aug 2020 07:18:34 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1597231112; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=lIL3ax7iw1V6MyxTB5cpVVoVwdT1FeuIF4S7J1ukeaA=; b=AjXU0dKUwa7uuVzZTsSRq1UjW6gg5IswckIwUNEI37YvZ+3+YEeyIg+a0UY4gO1aIa9kJB aS9RfG7S3h2KMvCmC4GxqFRNpll9jL83VPKzIojikIQd5i9DFOYHVJq9izuG/45eOO7YOF WB0P312uVSZxA4+DVypmOjv32tkxzhM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-323-wzC31UisNfqafbJe0IwR3Q-1; Wed, 12 Aug 2020 07:18:28 -0400 X-MC-Unique: wzC31UisNfqafbJe0IwR3Q-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9A67180183C; Wed, 12 Aug 2020 11:18:27 +0000 (UTC) Received: from work-vm (ovpn-113-233.ams2.redhat.com [10.36.113.233]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E8DBF5D9D3; Wed, 12 Aug 2020 11:18:21 +0000 (UTC) Date: Wed, 12 Aug 2020 12:18:19 +0100 From: "Dr. David Alan Gilbert" To: Christian Schoenebeck Cc: Greg Kurz , linux-fsdevel@vger.kernel.org, stefanha@redhat.com, mszeredi@redhat.com, vgoyal@redhat.com, gscrivan@redhat.com, dwalsh@redhat.com, chirantan@chromium.org Subject: Re: xattr names for unprivileged stacking? Message-ID: <20200812111819.GE2810@work-vm> References: <20200728105503.GE2699@work-vm> <2071310.X8v6e1yvPo@silver> <20200804112801.GA2659@work-vm> <2627251.EZXEZLLarb@silver> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2627251.EZXEZLLarb@silver> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org * Christian Schoenebeck (qemu_oss@crudebyte.com) wrote: > On Dienstag, 4. August 2020 13:28:01 CEST Dr. David Alan Gilbert wrote: > > > Well, depends on how large you draw the scope here. For instance Samba has > > > a bunch VFS modules which also uses and hence prohibits certain xattrs. > > > For instance for supporting (NTFS) alternate data streams (a.k.a. > > > resource forks) of Windows clients it uses user.DosStream.*: > > > > > > https://www.samba.org/samba/docs/current/man-html/vfs_streams_xattr.8.html > > > > > > as well as "user.DOSATTRIB". > > > > > > And as macOS heavily relies on resource forks (i.e. macOS doesn't work > > > without them), there are a bunch of xattr remappings in the dedicated > > > Apple VFS module, like "aapl_*": > > > > > > https://www.samba.org/samba/docs/current/man-html/vfs_fruit.8.html > > > https://github.com/samba-team/samba/blob/master/source3/modules/vfs_fruit. > > > c > > > > Thanks; what I've added to virtiofsd at the moment is a generic > > remapping thing that lets me add any prefix and block/drop any xattr. > > Right, makes absolutely sense to make it configurable. There are too many use > cases for xattrs, and the precise xattr names are often configurable as well, > like with the mentioned Samba VFS modules. > > > The other samba-ism I found was mvxattr(1) which lets you rename xattr's > > ona directory tree; which is quite useful. > > Haven't seen that before, interesting. > > BTW, I have plans for adding support for file forks [1] (a.k.a. alternate > streams, a.k.a. resource forks) on Linux kernel side, so I will probably come > up with an RFC in couple weeks to see whether there would be acceptance for > that at all and if yes in which form. > > That would open a similar problematic to virtiofsd on the long term, as file > forks have a namespace on their own. Yeh I'm sure that'll need wiring into lots of things in weird ways! I guess the main difference between an extended attribute and a file-fork is that you can access the fork using an fd and it feels more like a file? Dave > [1] https://en.wikipedia.org/wiki/Fork_(file_system) > > Best regards, > Christian Schoenebeck > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK