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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 02650C433E9 for ; Fri, 5 Mar 2021 13:11:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BCD076501C for ; Fri, 5 Mar 2021 13:11:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229836AbhCENKe (ORCPT ); Fri, 5 Mar 2021 08:10:34 -0500 Received: from mx1.hrz.uni-dortmund.de ([129.217.128.51]:40269 "EHLO unimail.uni-dortmund.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229493AbhCENKP (ORCPT ); Fri, 5 Mar 2021 08:10:15 -0500 Received: from [192.168.111.113] (p4fd97aad.dip0.t-ipconnect.de [79.217.122.173]) (authenticated bits=0) by unimail.uni-dortmund.de (8.16.1/8.16.1) with ESMTPSA id 125DA9IM027367 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NOT); Fri, 5 Mar 2021 14:10:09 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=tu-dortmund.de; s=unimail; t=1614949810; bh=gXsJ1fKl5lxPdzGuegoK8ZfZEm1Ox2xsolt/E9FEeJM=; h=Subject:From:To:References:Date:In-Reply-To; b=RtrzW8vxvWZHsPDtGBFNWMF3veXLstbgvGX+DtKo3uiZFzXKTNPawPey7FjaG/Sa9 V+Q8jBIXjgiMLCp+FTrp2G7cO6cMhPp8NiqGK6XlArTg/bACYmbBfMZzrdZkEIFTn2 k8P6k2nPJTzwKYEYVke58jamPz9RFtl1vZbX+4Zs= Subject: [RFC] inode.i_opflags - Usage of two different locking schemes From: Alexander Lochmann To: Horst Schirmeier , Jan Kara , "Theodore Ts'o" , Jan Kara , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org References: Message-ID: Date: Fri, 5 Mar 2021 14:10:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="qrtpaYptFGrAgmI252USJoKEQABELtY0k" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --qrtpaYptFGrAgmI252USJoKEQABELtY0k Content-Type: multipart/mixed; boundary="FtGpcBLiEc5Gzv1QqGCccAfWVGElCO9UF"; protected-headers="v1" From: Alexander Lochmann To: Horst Schirmeier , Jan Kara , Theodore Ts'o , Jan Kara , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: Subject: [RFC] inode.i_opflags - Usage of two different locking schemes References: In-Reply-To: --FtGpcBLiEc5Gzv1QqGCccAfWVGElCO9UF Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: de-DE Content-Transfer-Encoding: quoted-printable Hi folks, I've stumbled across an interesting locking scheme. It's related to=20 struct inode, more precisely it is an mqueue inode. Our results show that inode:mqueue.i_opflags is read with i_rwsem being=20 hold. In d_flags_for_inode, and do_inode_permission the i_lock is used to read = and write i_opflags. Is this a real locking scheme? Is a lock needed to access i_opflags at al= l? What is the magic behind this contradiction? I've put the report of the counterexamples on our webserver:=20 https://ess.cs.tu-dortmund.de/lockdoc-bugs/cex-inode-mqueue.html. It contains the stacktraces leading to those accesses, and the locks=20 that were actually held. Regards, Alex --=20 Technische Universit=C3=A4t Dortmund Alexander Lochmann PGP key: 0xBC3EF6FD Otto-Hahn-Str. 16 phone: +49.231.7556141 D-44227 Dortmund fax: +49.231.7556116 http://ess.cs.tu-dortmund.de/Staff/al --FtGpcBLiEc5Gzv1QqGCccAfWVGElCO9UF-- --qrtpaYptFGrAgmI252USJoKEQABELtY0k Content-Type: application/pgp-signature; name="OpenPGP_signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="OpenPGP_signature" -----BEGIN PGP SIGNATURE----- wsF5BAABCAAjFiEElhZsUHzVP0dbkjCRWT7tBbw+9v0FAmBCLbEFAwAAAAAACgkQWT7tBbw+9v3x ixAAwAOFV/Y+InVztS7YfL0LBxZlDpU5WAgDgqbi3vRK3nvi5IwSlHPzRTFb1E6nxYLCEWaT3cn5 2e/xX5wdmwkQGMAEnga3oUCBCp/+1212fF71FG23eXxH0QuYEYPDCbs26QOn97OUEa1HH0HcRc9G 7oiN58RbBBrqgHGqqchKI/dl638C0zL0SsRIXBueNw7mC8bOInDt7FHnIcPgKpHBqQkqbEyclkI6 ewh893N/TdRVMbOGsTJgJNJpToX0/DQhN6tghL94Xh2u0lEg/QYu3nO7w9nmMVPL3TgZaXV0/IZh mGp4+uPR09ejkXxpJlj3IiXI8SRCON3TZ3NN6M+ym5afKP3dL+Mjy2BSTRr97KKyNKJ1cTrdQiNS Vwl9/yLok5PaeUOKjqyavCDZYAQ+Hu/yAv993qGlJ3hE/MWkcVooWB2vdTwIg+A7lW4nP9/fYgP9 Ee9RnoC5EDy637EhBO5noIz3zbCy6egsFL0SIK5w9gQOmoh5gugIbxTNjXYgWMTNsOxxTW0E6VW6 G3uNECotVSjjr1ZiM7O/6hEu9GA3FlxXdI840Qfc10MxRHEz5fudG/nqglQ4eJ0jC3ZbDJI2Tuzd 9MrOSSiReoNlHZXUs2cS4XV8VHVr9nqV+10RWYpeHJidM2ypauKBommEPCR6o7kII7JX0UBMGLAb UYA= =BAR3 -----END PGP SIGNATURE----- --qrtpaYptFGrAgmI252USJoKEQABELtY0k--