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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 339E5C433DF for ; Fri, 15 May 2020 17:41:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 184CC2070A for ; Fri, 15 May 2020 17:41:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726197AbgEORll (ORCPT ); Fri, 15 May 2020 13:41:41 -0400 Received: from mx2.suse.de ([195.135.220.15]:52096 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726144AbgEORll (ORCPT ); Fri, 15 May 2020 13:41:41 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 9EC72B03C; Fri, 15 May 2020 17:41:42 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 7738EDA732; Fri, 15 May 2020 19:40:47 +0200 (CEST) Date: Fri, 15 May 2020 19:40:47 +0200 From: David Sterba To: Anand Jain Cc: linux-btrfs@vger.kernel.org, dsterba@suse.com Subject: Re: [PATCH] btrfs: fix lockdep warning chunk_mutex vs device_list_mutex Message-ID: <20200515174047.GN18421@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Anand Jain , linux-btrfs@vger.kernel.org, dsterba@suse.com References: <52b6ff4c2da5838393f5bd754310cfa6abcfcc7b3efb3c63c8d95824cb163d6d.dsterba@suse.com> <20200513194659.34493-1-anand.jain@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200513194659.34493-1-anand.jain@oracle.com> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Thu, May 14, 2020 at 03:46:59AM +0800, Anand Jain wrote: > A full list of tests just started. > > fs/btrfs/volumes.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > index 60ab41c12e50..ebc8565d0f73 100644 > --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -984,7 +984,6 @@ static struct btrfs_fs_devices *clone_fs_devices(struct btrfs_fs_devices *orig) > if (IS_ERR(fs_devices)) > return fs_devices; > So now here's the device_list_mutex taken by a caller but inside clone_fs_devices there's fs_devices = alloc_fs_devices(orig->fsid, NULL); just before this line and it does a GFP_KERNEL allocation. This could deadlock through the allocator trying to flush data and then superblock write locking the device_list_mutex again. > - mutex_lock(&orig->device_list_mutex); > fs_devices->total_devices = orig->total_devices; > > list_for_each_entry(orig_dev, &orig->devices, dev_list) {