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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1D1A0C77B60 for ; Sun, 30 Apr 2023 16:44:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230525AbjD3Qob (ORCPT ); Sun, 30 Apr 2023 12:44:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34724 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229478AbjD3Qoa (ORCPT ); Sun, 30 Apr 2023 12:44:30 -0400 Received: from outgoing.mit.edu (outgoing-auth-1.mit.edu [18.9.28.11]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E8F5B170A for ; Sun, 30 Apr 2023 09:44:28 -0700 (PDT) Received: from letrec.thunk.org ([76.150.80.181]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 33UGiFwF030379 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sun, 30 Apr 2023 12:44:17 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mit.edu; s=outgoing; t=1682873058; bh=kjFfB0mIP3X+i0mTn18RwHwQZScw1wf5xXbUVXbjOr0=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=YuUZ8zzX+TwdnSmsuk8s1btBU6K4j+5yLydEO1UzbBKePxnWj44zyOBsD7Gand6rN XyHWlZU/ToN/X8AWhlQ+g1UUIN8UQu5uSWml6yk5jZgSpPu62OVUgnmONLbexwqQdo M2WtmG9ZGmgPBTLBXAhHX+RLEmH4zF7RXb32KbaKId5HMSZJu/1aD7Ktf6w/azsNJG CSU1rA3NgGx42bfK2BXCp4Sa7XxNK1jKceDH+DHX1vTzSXO7/LGqCW6EJUBRGqHqxB y1zkoPAcJ427F6O7kdcYK+YoBYtuj1QNi6aJ/KTRSbwpRY8FDQ6bdsruA3GW2eP3j0 uUAN1xUtpDbHw== Received: by letrec.thunk.org (Postfix, from userid 15806) id 537D58C023E; Sun, 30 Apr 2023 12:44:15 -0400 (EDT) Date: Sun, 30 Apr 2023 12:44:15 -0400 From: "Theodore Ts'o" To: Jan Kara Cc: linux-ext4@vger.kernel.org, Christian Brauner , syzbot+aacb82fca60873422114@syzkaller.appspotmail.com, syzbot+6b7df7d5506b32467149@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com Subject: Re: [PATCH] ext4: Fix lockdep warning when enabling MMP Message-ID: References: <20230411121019.21940-1-jack@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Sun, Apr 30, 2023 at 12:34:00PM -0400, Theodore Ts'o wrote: > On Tue, Apr 11, 2023 at 02:10:19PM +0200, Jan Kara wrote: > > When we enable MMP in ext4_multi_mount_protect() during mount or > > remount, we end up calling sb_start_write() from write_mmp_block(). This > > triggers lockdep warning because freeze protection ranks above s_umount > > semaphore we are holding during mount / remount. The problem is harmless > > because we are guaranteed the filesystem is not frozen during mount / > > remount but still let's fix the warning by not grabbing freeze > > protection from ext4_multi_mount_protect(). > > > > Reported-by: syzbot+aacb82fca60873422114@syzkaller.appspotmail.com > > I believe this is the wrong Reported-by. The correct one looks like > it should be: ... By the way, I noticed because I was browsing the syzbot dashboard for the ext4 subsystem, and the Syzbot page for "possible deadlock in sys_quotactl_fd"[1], I saw a discussion link to lore for the patch "[PATCH] ext4: Fix lockdep warning when enabling MMP", and said, "Hmm.... that looks wrong." :-) [1] https://syzkaller.appspot.com/bug?id=1680b22e0e5eb9245a6faff10221ed76b8c5eb81 Anyway, thanks to the Syzbot team for adding Disscusion links to the Syzbot pages. It makes it a lot easier to find discussions related to a particular issue. Note: you can also manually add a thread to the discussions section by simply adding a CC to the Reported-by link for the particular issue (for example, "Cc: syzbot+aacb82fca60873422114@syzkaller.appspotmail.com"). Cheers, - Ted