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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 62BB6C433E0 for ; Thu, 9 Jul 2020 14:02:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 35D9620708 for ; Thu, 9 Jul 2020 14:02:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fK268Xpm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726617AbgGIOC0 (ORCPT ); Thu, 9 Jul 2020 10:02:26 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:35690 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726353AbgGIOC0 (ORCPT ); Thu, 9 Jul 2020 10:02:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1594303345; 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; bh=l9wiuPF7CNBdgguTw2kU5bfibEmZXIMMNaJ08n51z9k=; b=fK268XpmN7Y9dTX8J+iGj6nBn04jZJ3ml9e3p7sqZfgkJt7iLDRMjm9TzHEc9FcRV0m4/e aDyxqC4e29BEW0yVfedH5RqPAjwqW4qSV9UQABLOWW/vc9R1pHkB9SPE4J9Dz/KUJ/6spR rQLIyQZIo/Q57hSQ5ADXUtJlrDRiXE8= 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-220-dY7_4vx6MmGM8H8__00kHw-1; Thu, 09 Jul 2020 10:02:23 -0400 X-MC-Unique: dY7_4vx6MmGM8H8__00kHw-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 F34505EB; Thu, 9 Jul 2020 14:02:21 +0000 (UTC) Received: from horse.redhat.com (ovpn-115-114.rdu2.redhat.com [10.10.115.114]) by smtp.corp.redhat.com (Postfix) with ESMTP id 750C41001B07; Thu, 9 Jul 2020 14:02:21 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 98527220689; Thu, 9 Jul 2020 10:02:20 -0400 (EDT) Date: Thu, 9 Jul 2020 10:02:20 -0400 From: Vivek Goyal To: Amir Goldstein , Miklos Szeredi Cc: linux-unionfs@vger.kernel.org Subject: [PATCH] overlayfs, doc: Do not allow lower layer recreation with redirect_dir enabled Message-ID: <20200709140220.GC150543@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: linux-unionfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org Currently we seem to support lower layer recreation and re-use with existing upper until and unless "index" or "metadata only copy up" feature is enabled. If redirect_dir feature is enabled then re-creating/modifying lower layers will break things. For example. - mkdir lower lower/foo upper work merged - touch lower/foo/foo-child - mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work,redirect_dir=on none merged - mv merged/foo merged/bar - ls merged/bar/ (this should list foo-child) - umount merged - mv lower/foo lower/baz - mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work,redirect_dir=on none merged - ls merged/bar/ (Now foo-child has disappeared) IOW, modifying lower layers did not crash overlay but it resulted in directory contents being lost and that can be unexpected. So don't support lower layer recreation/modification when redirect_dir is enabled at any point of time. Signed-off-by: Vivek Goyal --- Documentation/filesystems/overlayfs.rst | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/Documentation/filesystems/overlayfs.rst b/Documentation/filesystems/overlayfs.rst index 660dbaf0b9b8..1d1a8da7fdbc 100644 --- a/Documentation/filesystems/overlayfs.rst +++ b/Documentation/filesystems/overlayfs.rst @@ -371,8 +371,8 @@ conflict with metacopy=on, and will result in an error. [*] redirect_dir=follow only conflicts with metacopy=on if upperdir=... is given. -Sharing and copying layers --------------------------- +Sharing, copying and recreating lower layers +-------------------------------------------- Lower layers may be shared among several overlay mounts and that is indeed a very common practice. An overlay mount may use the same lower layer @@ -388,8 +388,12 @@ though it will not result in a crash or deadlock. Mounting an overlay using an upper layer path, where the upper layer path was previously used by another mounted overlay in combination with a -different lower layer path, is allowed, unless the "inodes index" feature -or "metadata only copy up" feature is enabled. +different lower layer path, is allowed, unless any of the following features +is enabled at any point of time. + +- inode index +- metadata only copy up +- redirect_dir With the "inodes index" feature, on the first time mount, an NFS file handle of the lower layer root directory, along with the UUID of the lower -- 2.25.4