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=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 3E117C43381 for ; Wed, 20 Mar 2019 15:16:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E146E2186A for ; Wed, 20 Mar 2019 15:16:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553094966; bh=Q2uqz0abO13IbpvyBS4N4DFeCsQZY/7NG+N/1M9GJIo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=MjTuhQgdDEwDswEft6T8aNdPyVj7Uxi1ucUrkoarNPDlOSzzZuPTTUdi0l33Mloul JwM8NZu1yocYZ+Wf/ckxen3ZbDcDla+5dKAerpmF/LFOGEDEtvkEOUwGgjku5PRUTp bNSRdfjBv3xB9tehs9gkRV4NisbOanxGo4rSpE78= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726802AbfCTPQF (ORCPT ); Wed, 20 Mar 2019 11:16:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:40818 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726169AbfCTPQF (ORCPT ); Wed, 20 Mar 2019 11:16:05 -0400 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E4F8B2184D; Wed, 20 Mar 2019 15:16:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553094964; bh=Q2uqz0abO13IbpvyBS4N4DFeCsQZY/7NG+N/1M9GJIo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=2tNDJgMnHex4iEG+T/GCfI1RJTZEC60vP3Gm3eTGdjJ2W+YzMBKO07KWK5n5b/pWj X55MCttyl/snF6KukqXoUf0CzF0kFcuXA7Ax4Lqc7gerhoPtDHTHw33aDJGXd0H0Sr R1L7kdAgSR3MLgnnRX72R+wHz0S6Y77v1Scev/RM= Date: Wed, 20 Mar 2019 16:16:01 +0100 From: Greg KH To: Jan Kara Cc: stable@vger.kernel.org, Jens Axboe , linux-block@vger.kernel.org Subject: Re: Revert commit 310ca162d77 Message-ID: <20190320151601.GA31992@kroah.com> References: <20190320125806.GD9485@quack2.suse.cz> <20190320151231.GA31247@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190320151231.GA31247@kroah.com> User-Agent: Mutt/1.11.4 (2019-03-13) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Wed, Mar 20, 2019 at 04:12:31PM +0100, Greg KH wrote: > On Wed, Mar 20, 2019 at 01:58:06PM +0100, Jan Kara wrote: > > Hello, > > > > commit 310ca162d77 "block/loop: Use global lock for ioctl() operation." has > > been pushed to multiple stable trees. This patch is a part of larger series > > that overhauls the locking inside loopback device upstream and for 4.4, > > 4.9, and 4.14 stable trees only this patch from the series is applied. Our > > testing now has shown [1] that the patch alone makes present deadlocks > > inside loopback driver more likely (the openqa test in our infrastructure > > didn't hit the deadlock before whereas with the new kernel it hits it > > reliably every time). So I would suggest we revert 310ca162d77 from 4.4, > > 4.9, and 4.14 kernels. > > Ugh, ok. > > > Another option would be to backport other locking fixes for the loop > > device but honestly I don't think that's a stable material - never heard > > of real users hitting problems, only syzkaller could, and we are still > > fixing up some small glitches resulting from that rework... > > I tried to backport a number of the loop fixes, and odds are I am the > one that grabbed this. There are other loop locking fixes in the stable > releases, I don't know if I can just revert this one, let me check... Nope, does not revert cleanly due to the other loop fixes I added after this one. So either I back out _all_ of the loop patches, or we leave what we have now, or we add the proper fixes to get things working. I'd like to have this all work properly, so why not just have me backport the needed fixes that are upstream? thanks, greg k-h