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=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_NEOMUTT autolearn=unavailable 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 88872C282D9 for ; Wed, 30 Jan 2019 17:43:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 608D221473 for ; Wed, 30 Jan 2019 17:43:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732639AbfA3RnO (ORCPT ); Wed, 30 Jan 2019 12:43:14 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59882 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732541AbfA3RnN (ORCPT ); Wed, 30 Jan 2019 12:43:13 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8BEEAC7912; Wed, 30 Jan 2019 17:43:13 +0000 (UTC) Received: from ws.net.home (ovpn-117-196.ams2.redhat.com [10.36.117.196]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 17921608C8; Wed, 30 Jan 2019 17:43:10 +0000 (UTC) Date: Wed, 30 Jan 2019 18:43:06 +0100 From: Karel Zak To: David Howells Cc: "Eric W. Biederman" , linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Al Viro , Miklos Szeredi , Linus Torvalds , util-linux@vger.kernel.org, Andy Lutomirski Subject: Re: [RFD] A mount api that notices previous mounts Message-ID: <20190130174306.4nbrh2m53re35qch@ws.net.home> References: <20190130120654.q5zqcexquca7u337@ws.net.home> <87va2716mh.fsf@xmission.com> <9871.1548853314@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9871.1548853314@warthog.procyon.org.uk> User-Agent: NeoMutt/20180716-1023-ca4e12 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Wed, 30 Jan 2019 17:43:13 +0000 (UTC) Sender: util-linux-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: util-linux@vger.kernel.org On Wed, Jan 30, 2019 at 01:01:54PM +0000, David Howells wrote: > Karel Zak wrote: > > > It seems more elegant is to ask for Nth option as expected by fsinfo(). > > More elegant yes, but there's an issue with atomiticity[*]. I'm in the > process of switching to something that returns you a single buffer with all > the options in, but each key and each value is preceded by a length count. Sounds good, for me is important to avoid all the split/join operations with the strings. > The reasons for not using separator characters are: > > (1) There's no separator char that cannot validly occur within an option[**]. Yes, it's pretty common for selinux mount options where "," is used within an option, so mount options string looks like 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec' and I have doubts all the parses in userspace are compatible with this use case... > (2) Makes it possible to return binary values if we need to. Yes. > [**] Oh, and look at cifs where you can *change* the separator char during > option parsing ("sep="). No comment :-) Karel -- Karel Zak http://karelzak.blogspot.com