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=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 0591FC433E1 for ; Wed, 12 Aug 2020 13:06:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D51EB207F7 for ; Wed, 12 Aug 2020 13:06:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="aLcEqKgy" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728028AbgHLNGj (ORCPT ); Wed, 12 Aug 2020 09:06:39 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:58899 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726829AbgHLNGh (ORCPT ); Wed, 12 Aug 2020 09:06:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1597237593; 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=4WKj+EyxU40YOue4LK4S3MO6lm+DalQD8muSGHaR5fw=; b=aLcEqKgyd0L9T+S1WoJqHS2KLJkcR3QyAOU7Lh0tWdGa7xrm7dFuqKoEY4wI3k0PraKrsH wfnw0G72tNHwH5T0BslYQxZ03Fp3/J9OUUf5xdNt2PV7LtenZ6fqUZRd5Y0qPLndC5eaL9 P3nmaFFsU2vSiRRnykzzxyVXRZz+lAQ= 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-320-_TjpIsNMMFaXBv8PSKNPhg-1; Wed, 12 Aug 2020 09:06:31 -0400 X-MC-Unique: _TjpIsNMMFaXBv8PSKNPhg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8D391E923; Wed, 12 Aug 2020 13:06:29 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-127.rdu2.redhat.com [10.10.120.127]) by smtp.corp.redhat.com (Postfix) with ESMTP id 553C01001B07; Wed, 12 Aug 2020 13:06:26 +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: <20200811135419.GA1263716@miu.piliscsaba.redhat.com> <52483.1597190733@warthog.procyon.org.uk> <98802.1597220949@warthog.procyon.org.uk> <20200812112825.b52tqeuro2lquxlw@ws.net.home> To: Miklos Szeredi Cc: dhowells@redhat.com, Karel Zak , Steven Whitehouse , Linus Torvalds , linux-fsdevel , Al Viro , Jeff Layton , Miklos Szeredi , Nicolas Dichtel , Christian Brauner , Lennart Poettering , Linux API , Ian Kent , LSM , Linux Kernel Mailing List Subject: Re: file metadata via fs API MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <131357.1597237585.1@warthog.procyon.org.uk> Date: Wed, 12 Aug 2020 14:06:25 +0100 Message-ID: <131358.1597237585@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Miklos Szeredi wrote: > That presumably means the mount ID <-> mount path mapping already > exists, which means it's just possible to use the open(mount_path, > O_PATH) to obtain the base fd. No, you can't. A path more correspond to multiple mounts stacked on top of each other, e.g.: mount -t tmpfs none /mnt mount -t tmpfs none /mnt mount -t tmpfs none /mnt Now you have three co-located mounts and you can't use the path to differentiate them. I think this might be an issue in autofs, but Ian would need to comment on that. David