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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 053DDECDFB1 for ; Tue, 17 Jul 2018 09:40:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A78B320C0A for ; Tue, 17 Jul 2018 09:40:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A78B320C0A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730215AbeGQKM2 convert rfc822-to-8bit (ORCPT ); Tue, 17 Jul 2018 06:12:28 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:45644 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728610AbeGQKM2 (ORCPT ); Tue, 17 Jul 2018 06:12:28 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 48AC9814F0B7; Tue, 17 Jul 2018 09:40:43 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-116.rdu2.redhat.com [10.10.120.116]) by smtp.corp.redhat.com (Postfix) with ESMTP id AE0B67C3E; Tue, 17 Jul 2018 09:40:41 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <153126248868.14533.9751473662727327569.stgit@warthog.procyon.org.uk> <153126264966.14533.3388004240803696769.stgit@warthog.procyon.org.uk> <686E805C-81F3-43D0-A096-50C644C57EE3@amacapital.net> <22370.1531293761@warthog.procyon.org.uk> <7002.1531407244@warthog.procyon.org.uk> <338BC3C4-F3E7-48F0-A82E-2C7295B6640E@amacapital.net> <17749.1531429218@warthog.procyon.org.uk> <21131.1531488422@warthog.procyon.org.uk> To: Andy Lutomirski Cc: dhowells@redhat.com, Linus Torvalds , Andrew Lutomirski , Al Viro , Linux API , linux-fsdevel , Linux Kernel Mailing List , Jann Horn , Tycho Andersen Subject: Re: [PATCH 24/32] vfs: syscall: Add fsopen() to prepare for superblock creation [ver #9] MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Date: Tue, 17 Jul 2018 10:40:41 +0100 Message-ID: <11586.1531820441@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.8]); Tue, 17 Jul 2018 09:40:43 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.8]); Tue, 17 Jul 2018 09:40:43 +0000 (UTC) for IP:'10.11.54.5' DOMAIN:'int-mx05.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'dhowells@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andy Lutomirski wrote: > > Whilst I'm at it, do we want the option of doing the equivalent of > > mountat()? I.e. offering the option to open all the device files used by > > a superblock with dfd and AT_* flags in combination with the filename? > > > > Isn’t that more or less what I was suggesting? I suggested dfd and path and I also suggested just an fd and letting the caller open the file itself. Do we need AT_* flags? There are three that we could use: AT_SYMLINK_NOFOLLOW AT_NO_AUTOMOUNT AT_EMPTY_PATH AT_EMPTY_PATH I can see, but I don't see it as likely that we'd want to use the other two for selecting a source? Note that we can always do: fsfd = fsopen("ext4"); sfd = open("/dev/", O_PATH); fsconfig(fsfd, fsconfig_set_path, "journal_path", "sda1", sfd); or: fsfd = fsopen("ext4"); sfd = open("/dev/sda1", O_PATH); fsconfig(fsfd, fsconfig_set_path_empty, "journal_path", "", sfd); or: fsfd = fsopen("ext4"); jfd = open("/dev/sda1", O_RDWR); fsconfig(fsfd, fsconfig_set_fd, "journal_path", NULL, jfd); assuming the open on the latter doesn't exclude the use by the filesystem. This way I don't need a second syscall or a 6-arg syscall to handle path specification. David