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,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 5204AC433E0 for ; Thu, 13 Aug 2020 01:01:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 17BBF206B2 for ; Thu, 13 Aug 2020 01:01:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=themaw.net header.i=@themaw.net header.b="YsGy5BPC"; dkim=pass (2048-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b="RH5FLj2b" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726600AbgHMBBp (ORCPT ); Wed, 12 Aug 2020 21:01:45 -0400 Received: from wnew2-smtp.messagingengine.com ([64.147.123.27]:60243 "EHLO wnew2-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726078AbgHMBBo (ORCPT ); Wed, 12 Aug 2020 21:01:44 -0400 Received: from compute2.internal (compute2.nyi.internal [10.202.2.42]) by mailnew.west.internal (Postfix) with ESMTP id 2FEF5B4F; Wed, 12 Aug 2020 21:01:42 -0400 (EDT) Received: from mailfrontend1 ([10.202.2.162]) by compute2.internal (MEProxy); Wed, 12 Aug 2020 21:01:43 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=themaw.net; h= message-id:subject:from:to:cc:date:in-reply-to:references :content-type:mime-version:content-transfer-encoding; s=fm3; bh= JG1tgGZ/mQI9+jPnvtxoNjrRjRVSVgKjSvfLuuK+16o=; b=YsGy5BPCab5tRtyn T6XQlYKFThZ2rbXRsDmInqLDn3V+VijsKNYx70VBFA3doBccGyS0GW3fKT/FMT7L CrBLO4cZrRIcshJcwe9IrNnzTbQ68p1q2X2pwGhtlBs5HglthTBZAr9KpLoQjJv2 oi3NcyHfLBdsPSsGxsnMx9SDmhTd4aF9faRx6U0qZeJQ9XTEsd8UeWvulViu7sgz M4BI3M18nX91VCBQwn6GqhfMJyQl+83/+Zgn6d6HB/KuWfm3VcPRTriQhajyAxxV oz3FU48W8KTuaXUBTFi+LZgxdGqB1WmQTFh/FqrIUtfGRkz1Rq0PIghWQmGxto1f lWNgew== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:in-reply-to:message-id:mime-version:references :subject:to:x-me-proxy:x-me-proxy:x-me-sender:x-me-sender :x-sasl-enc; s=fm3; bh=JG1tgGZ/mQI9+jPnvtxoNjrRjRVSVgKjSvfLuuK+1 6o=; b=RH5FLj2bOOLTC4WTSYiN1K8+Bst9j2gJtQjvt1s4rIUBCFWcgvSQNu7mr pitZlBaELSNmB5K6TdX/oxfSa6WSs86X76XCrRuzYGg2ufjODnJNYaqveT/zepbA BndAAner4iGUjtl59qs5PZL69w/6x+vmR9fuAcrwvpaXx0Pv6YYmESh4Ca+Hd43W glFdlaDtbCVVeTgI1kGiVMR0KpGy/bOtopMb+wMeycysNBh0E7KPyqGwmG2Ot6m5 ttCYaDmLSvbz0bSoBlQlaGHIoTzdyFlF/BhEw2Tt8rA7TPEVZbT1nQ1kxycxsFzX /XT9WtixMxBZ6UL5iT3K+hMPRHNtQ== X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeduiedrleefgdegfecutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenuc fjughrpefkuffhvfffjghftggfggfgsehtjeertddtreejnecuhfhrohhmpefkrghnucfm vghnthcuoehrrghvvghnsehthhgvmhgrfidrnhgvtheqnecuggftrfgrthhtvghrnhepfe efteetvdeguddvveefveeftedtffduudehueeihfeuvefgveehffeludeggfejnecukfhp peehkedrjedrvddtfedruddugeenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmh epmhgrihhlfhhrohhmpehrrghvvghnsehthhgvmhgrfidrnhgvth X-ME-Proxy: Received: from mickey.themaw.net (58-7-203-114.dyn.iinet.net.au [58.7.203.114]) by mail.messagingengine.com (Postfix) with ESMTPA id AF46D3280065; Wed, 12 Aug 2020 21:01:35 -0400 (EDT) Message-ID: <989bb93754a4af69c02a9f42b05549f7e72630b3.camel@themaw.net> Subject: Re: file metadata via fs API From: Ian Kent To: David Howells , Miklos Szeredi Cc: Karel Zak , Steven Whitehouse , Linus Torvalds , linux-fsdevel , Al Viro , Jeff Layton , Miklos Szeredi , Nicolas Dichtel , Christian Brauner , Lennart Poettering , Linux API , LSM , Linux Kernel Mailing List Date: Thu, 13 Aug 2020 09:01:31 +0800 In-Reply-To: <131358.1597237585@warthog.procyon.org.uk> References: <20200811135419.GA1263716@miu.piliscsaba.redhat.com> <52483.1597190733@warthog.procyon.org.uk> <98802.1597220949@warthog.procyon.org.uk> <20200812112825.b52tqeuro2lquxlw@ws.net.home> <131358.1597237585@warthog.procyon.org.uk> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.34.4 (3.34.4-1.fc31) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2020-08-12 at 14:06 +0100, David Howells wrote: > 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. It is a problem for autofs, direct mounts in particular, but also for mount ordering at times when umounting a tree of mounts where mounts are covered or at shutdown. Ian