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=-5.3 required=3.0 tests=BAYES_00, 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 0C44EC2D0E4 for ; Mon, 23 Nov 2020 16:52:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C69AC20717 for ; Mon, 23 Nov 2020 16:52:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732512AbgKWQw3 (ORCPT ); Mon, 23 Nov 2020 11:52:29 -0500 Received: from mx2.suse.de ([195.135.220.15]:52326 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726417AbgKWQw3 (ORCPT ); Mon, 23 Nov 2020 11:52:29 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id A9945ACBD; Mon, 23 Nov 2020 16:52:28 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 60A08DA818; Mon, 23 Nov 2020 17:50:40 +0100 (CET) Date: Mon, 23 Nov 2020 17:50:40 +0100 From: David Sterba To: Boris Burkov Cc: linux-btrfs@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH v7 01/12] btrfs: lift rw mount setup from mount and remount Message-ID: <20201123165040.GF8669@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Boris Burkov , linux-btrfs@vger.kernel.org, kernel-team@fb.com References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Wed, Nov 18, 2020 at 03:06:16PM -0800, Boris Burkov wrote: > Mounting rw and remounting from ro to rw naturally share invariants and > functionality which result in a correctly setup rw filesystem. Luckily, > there is even a strong unity in the code which implements them. In > mount's open_ctree, these operations mostly happen after an early return > for ro file systems, and in remount, they happen in a section devoted to > remounting ro->rw, after some remount specific validation passes. > > However, there are unfortunately a few differences. There are small > deviations in the order of some of the operations, remount does not > cleanup orphan inodes in root_tree or fs_tree, remount does not create > the free space tree, and remount does not handle "one-shot" mount > options like clear_cache and uuid tree rescan. > > Since we want to add building the free space tree to remount, and since > it is possible to leak orphans on a filesystem mounted as ro then > remounted rw The statement is not specific if the orphans are files or roots. But I don't agree that a leak is possible, or need a proof of the claim above. The mount-time orphan cleanup will start early, but otherwise orphan cleanup is checked and started on dentry lookups (btrfs_lookup_dentry). Deleted but not clened tree roorts are all found and removed, regardless of rw or ro->rw mount. So I wonder if you claim there's a leak just by lack of an explicit call on the remount path.