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 78354C83F2D for ; Sun, 3 Sep 2023 18:01:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238740AbjICSBg (ORCPT ); Sun, 3 Sep 2023 14:01:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60080 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229665AbjICSBg (ORCPT ); Sun, 3 Sep 2023 14:01:36 -0400 Received: from zeniv.linux.org.uk (zeniv.linux.org.uk [IPv6:2a03:a000:7:0:5054:ff:fe1c:15ff]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42346D9; Sun, 3 Sep 2023 11:01:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=linux.org.uk; s=zeniv-20220401; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=S9Vu6m4/BeTB9HCncSagEJ1QKniB6AXPYafpsvd+t/Y=; b=Hz8Rmv8O0J2BQeSNcabh+Masdo 83vXuhpL/rmZRAyGK/sdDLMDWcoPLWqjyjoTZVq2EK9MHu5USNzF07SWBN//D9CoRrK4EfXj6HiOu rIbcpi8cYA6CCGFrzL8EkiILQfT9h/ix/FIKmyDT7SPteIyYOtNnPW48R6jEv10NLDQ4OYuW9KlVt fPnTxHMbCgwiTmYAyCxgCjczVVZUBzuyWMwXAqh7vyvittDtBpTMBpsxXuHDMjItIU7/pPhIY5t+J dmaUY/ekdwOg31wUNKABWQA8QzDpTJvjIlyALWnL3MpWLvJKPuilp2Lip1LFj3/N3jVAF6KaYecJs MflbsOrw==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.96 #2 (Red Hat Linux)) id 1qcrPa-0037Rq-20; Sun, 03 Sep 2023 18:01:26 +0000 Date: Sun, 3 Sep 2023 19:01:26 +0100 From: Al Viro To: Mateusz Guzik Cc: Dave Chinner , syzbot , brauner@kernel.org, djwong@kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, llvm@lists.linux.dev, nathan@kernel.org, ndesaulniers@google.com, syzkaller-bugs@googlegroups.com, trix@redhat.com Subject: Re: [syzbot] [xfs?] INFO: task hung in __fdget_pos (4) Message-ID: <20230903180126.GL3390869@ZenIV> References: <000000000000e6432a06046c96a5@google.com> <20230903083357.75mq5l43gakuc2z7@f> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230903083357.75mq5l43gakuc2z7@f> Sender: Al Viro Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Sun, Sep 03, 2023 at 10:33:57AM +0200, Mateusz Guzik wrote: > On Sun, Sep 03, 2023 at 03:25:28PM +1000, Dave Chinner wrote: > > On Sat, Sep 02, 2023 at 09:11:34PM -0700, syzbot wrote: > > > Hello, > > > > > > syzbot found the following issue on: > > > > > > HEAD commit: b97d64c72259 Merge tag '6.6-rc-smb3-client-fixes-part1' of.. > > > git tree: upstream > > > console output: https://syzkaller.appspot.com/x/log.txt?x=14136d8fa80000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=958c1fdc38118172 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=e245f0516ee625aaa412 > > > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > > > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > Been happening for months, apparently, yet for some reason it now > > thinks a locking hang in __fdget_pos() is an XFS issue? > > > > #syz set subsystems: fs > > > > The report does not have info necessary to figure this out -- no > backtrace for whichever thread which holds f_pos_lock. I clicked on a > bunch of other reports and it is the same story. > > Can the kernel be configured to dump backtraces from *all* threads? > > If there is no feature like that I can hack it up. t over serial console, or echo t >/proc/sysrq-trigger would do it... "Locking hang in __fdget_pos()" would mean either something stuck inside ->read/->write/->read_iter/->write_iter/->llseek instance, making any further syscalls in that bunch on the same open file to block, or a lost fdput_pos() somewhere; AFAICS, we don't have anything of the latter variety, but the former is too wide to tell anything useful.