From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:52971 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750718AbeAOT2Z (ORCPT ); Mon, 15 Jan 2018 14:28:25 -0500 Date: Mon, 15 Jan 2018 20:26:15 +0100 From: David Sterba To: Anand Jain Cc: "Misono, Tomohiro" , linux-btrfs@vger.kernel.org, David Sterba Subject: Re: [PATCH v4 2/4] btrfs: cleanup btrfs_mount() using btrfs_mount_root() Message-ID: <20180115192615.GF13726@twin.jikos.cz> Reply-To: dsterba@suse.cz References: <7dbb897c-1f1d-b54b-0cea-2a1c6c1d5027@jp.fujitsu.com> <28c4963f-9e87-ce42-7c6a-85d32cd71951@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <28c4963f-9e87-ce42-7c6a-85d32cd71951@oracle.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Fri, Jan 12, 2018 at 06:14:40PM +0800, Anand Jain wrote: > > Misono, > > This change is causing subsequent (subvol) mount to fail when device > option is specified. The simplest eg for failure is .. > mkfs.btrfs -qf /dev/sdc /dev/sdb > mount -o device=/dev/sdb /dev/sdc /btrfs > mount -o device=/dev/sdb /dev/sdc /btrfs1 > mount: /dev/sdc is already mounted or /btrfs1 busy > > Looks like > blkdev_get_by_path() <-- is failing. > btrfs_scan_one_device() > btrfs_parse_early_options() > btrfs_mount() > > Which is due to different holders (viz. btrfs_root_fs_type and > btrfs_fs_type) one is used for vfs_mount and other for scan, > so they form different holders and can't let EXCL open which > is needed for both scan and open. This looks close to what I see in the random test failures. I've reverted your patch "btrfs: optimize move uuid_mutex closer to the critical section" as I bisected to it. The uuid mutex around blkdev_get_path probably protected the concurrent mount and scan so they did not ask for EXCL at the same time. Reverting (or removing the patch from the current misc-next) queue is simpler for me ATM as I want to get to a stable base now, we can add it later if we understand the issue with the mount/scan.