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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 EFD80C282C3 for ; Tue, 22 Jan 2019 13:22:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C7219217FA for ; Tue, 22 Jan 2019 13:22:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728583AbfAVNWb (ORCPT ); Tue, 22 Jan 2019 08:22:31 -0500 Received: from mx2.suse.de ([195.135.220.15]:40202 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728406AbfAVNWa (ORCPT ); Tue, 22 Jan 2019 08:22:30 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 29C18AFF7; Tue, 22 Jan 2019 13:22:29 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id C8F101E3E20; Tue, 22 Jan 2019 14:22:28 +0100 (CET) Date: Tue, 22 Jan 2019 14:22:28 +0100 From: Jan Kara To: Kevin Weidemann Cc: Jan Kara , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Pali =?iso-8859-1?Q?Roh=E1r?= Subject: Re: udf: Prevent write-unsupported filesystem to be remounted read-write Message-ID: <20190122132228.GF13149@quack2.suse.cz> References: <124cc6ea-ca79-20f2-651e-c2f909729ac0@gmx.de> <8cf39b7c-505b-91e6-849d-e66ba980042f@postn.eu> <20190114103011.GD13316@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190114103011.GD13316@quack2.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Mon 14-01-19 11:30:11, Jan Kara wrote: > On Mon 14-01-19 01:33:30, Kevin Weidemann wrote: > > this is RE the patch 8515b9edf7a0c9dcf1ad218ccc783700db217336 (Upstream > > commit a9ad01bc759df79b0012f43ee52164391e31cd96) in 4.18.20. > > > > I have an issue with UDF. I used to be able to create a UDF fs in a way > > that is very similar to this: > > > > `# mkudffs --label=.... -m dvd -b 512 /dev/mapper/cryptdev1` > > > > I used to proceed mounting it, noticing it got mounted as readonly > > (because the accesstype of the udf fs is readonly (as decided per -m > > dvd)), so I remounted it as rw and then was able to fill it with data.[1] > > > > Now, this doesn't work anymore since the last time I did that. I figured > > out it must have to do with the commit mentioned above. All I get now, > > during a remount-as-rw attempt, is: > > `cannot remount /dev/mapper/cryptdev1 read-write, is write-protected`. > > > > I am not sure if this counts as a regression, because I see the point in > > not only auto-mounting such filesystems as readonly, but also preventing > > remounting as rw, however it breaks my use case. > > > > However, I noticed the following, too: > > case A) when having a "readonly udf" on a readwrite device, the > > filesystem mounts as readonly (old behavior) and also prevents remounting > > as rw (new behavior) > > This works as intended. > > > case B) when having a "readwrite udf" on a readonly device, the > > filesystem mounts as readwrite (!), but the writes end up being invisibly > > discarded > > That's a bug. I'll fix it. Thanks for reporting this! I have checked this and it works for me as designed: (none):~# mount -t udf /dev/ubdb /mnt mount: block device /dev/ubdb is write-protected, mounting read-only UDF-fs: warning (device ubdb): udf_load_vrs: No anchor found UDF-fs: Scanning with blocksize 512 failed UDF-fs: warning (device ubdb): udf_load_vrs: No anchor found UDF-fs: Scanning with blocksize 1024 failed UDF-fs: INFO Mounting volume 'LinuxUDF', timestamp 2017/01/20 10:17 (1000) So if the block device is read-only, you will get only read only mount. Also remount read-write gets prevented: (none):~# mount -o remount,rw /mnt/ mount: block device /dev/ubdb is write-protected, mounting read-only Or with more recent util-linux (2.31.1): (none):/ # mount -t udf /dev/ubdb /mnt UDF-fs: warning (device ubdb): udf_load_vrs: No anchor found UDF-fs: Scanning with blocksize 512 failed UDF-fs: warning (device ubdb): udf_load_vrs: No anchor found UDF-fs: Scanning with blocksize 1024 failed UDF-fs: INFO Mounting volume 'LinuxUDF', timestamp 2017/01/20 10:17 (1000) mount: /mnt: WARNING: device write-protected, mounted read-only. and remount: (none):/ # mount -o remount,rw /mnt mount: /mnt: cannot remount /dev/ubdb read-write, is write-protected. The kernel is 5.0-rc3. What kernel were you testing with? Honza -- Jan Kara SUSE Labs, CR