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=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 4015BC433DF for ; Tue, 11 Aug 2020 15:30:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0F605206DC for ; Tue, 11 Aug 2020 15:30:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=szeredi.hu header.i=@szeredi.hu header.b="UHuiqJr7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728951AbgHKPat (ORCPT ); Tue, 11 Aug 2020 11:30:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60278 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728883AbgHKPaq (ORCPT ); Tue, 11 Aug 2020 11:30:46 -0400 Received: from mail-ej1-x642.google.com (mail-ej1-x642.google.com [IPv6:2a00:1450:4864:20::642]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 588A2C06178A for ; Tue, 11 Aug 2020 08:30:45 -0700 (PDT) Received: by mail-ej1-x642.google.com with SMTP id qc22so13554026ejb.4 for ; Tue, 11 Aug 2020 08:30:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=szeredi.hu; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=2+Iq2qCHUHVaNAKHuF0ZSvBIxw9aZEr5eRrwEH0pyDM=; b=UHuiqJr7X2atxIGSHLT+svSK5gdNsubwckkEdoLhXVa0P5T2fMneByo6aZKzG8LldX T1q+WwMY0FUEt+jhdI91DgqUpJ4E3NQyPft4lnwP2z3OP679ywggUOEnwc9ZpPQSZeqm UJZcOolg7KSv4Nk5wS9SsRafbH+gx/jq+8o2c= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=2+Iq2qCHUHVaNAKHuF0ZSvBIxw9aZEr5eRrwEH0pyDM=; b=GYvZ2uB15Bosq+kEHER5V00iq4/urE14ucHykZQKo/sg1MpS58umlY+3/7H8LREl0N eR0HfL4j1tcTh1IN2reHsB4NnNZdjCp1zirpap1RhSvC7Qjx9XUTEKi2RAdgxlinmVtG 3kQv3uY20B7SQah5ohViW9z2dMFzxeiZTPXua0q9J5C5f2pb/3LK4INhvTE9TN51QrJX SLBlV4l+S488ykX9SvWeU9IHllqFNNQAWJ1tuH7Ys7zA8XgpBRMpQQmy5NPfuCglRy7K sVow6iZ9PhSqG/2V+mQSCURO2E0/t55kBQTG0ik+nFQv92EkfuG1Ydmacd3jylrbMmDU rGYw== X-Gm-Message-State: AOAM531S0IQIw1Aba9qlEt9KQKlh/pumguiGI/Jppt44/Fgo5fEHNQSQ QRsik09u9fuywDgGeUmhUfiNzuNIPUn0G//RG1p/PQ== X-Google-Smtp-Source: ABdhPJzBzum8mnm+vTGkWQzIaTCUoEszBkoemTUzdbDb+99lWLtwfHPa77uVvxYBE8u6HRWpehJ7Yt8BQd5fvoZKDLs= X-Received: by 2002:a17:907:94ca:: with SMTP id dn10mr26676759ejc.110.1597159843363; Tue, 11 Aug 2020 08:30:43 -0700 (PDT) MIME-Version: 1.0 References: <1842689.1596468469@warthog.procyon.org.uk> <1845353.1596469795@warthog.procyon.org.uk> <20200811135419.GA1263716@miu.piliscsaba.redhat.com> In-Reply-To: From: Miklos Szeredi Date: Tue, 11 Aug 2020 17:30:32 +0200 Message-ID: Subject: Re: file metadata via fs API (was: [GIT PULL] Filesystem Information) To: Linus Torvalds Cc: linux-fsdevel , David Howells , Al Viro , Karel Zak , Jeff Layton , Miklos Szeredi , Nicolas Dichtel , Christian Brauner , Lennart Poettering , Linux API , Ian Kent , LSM , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 11, 2020 at 5:20 PM Linus Torvalds wrote: > > [ I missed the beginning of this discussion, so maybe this was already > suggested ] > > On Tue, Aug 11, 2020 at 6:54 AM Miklos Szeredi wrote: > > > > > > > > E.g. > > > openat(AT_FDCWD, "foo/bar//mnt/info", O_RDONLY | O_ALT); > > > > Proof of concept patch and test program below. > > I don't think this works for the reasons Al says, but a slight > modification might. > > IOW, if you do something more along the lines of > > fd = open(""foo/bar", O_PATH); > metadatafd = openat(fd, "metadataname", O_ALT); > > it might be workable. That would have been my backup suggestion, in case the unified namespace doesn't work out. I wouldn't think the normal lookup rules really get in the way if we explicitly enable alternative path lookup with a flag. The rules just need to be documented. What's the disadvantage of doing it with a single lookup WITH an enabling flag? It's definitely not going to break anything, so no backward compatibility issues whatsoever. Thanks, Miklos