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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable 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 530CFC10F05 for ; Wed, 20 Mar 2019 12:58:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2B8C221873 for ; Wed, 20 Mar 2019 12:58:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726362AbfCTM6I (ORCPT ); Wed, 20 Mar 2019 08:58:08 -0400 Received: from mx2.suse.de ([195.135.220.15]:46642 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725996AbfCTM6I (ORCPT ); Wed, 20 Mar 2019 08:58:08 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 18908AC24; Wed, 20 Mar 2019 12:58:07 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id B97971E4255; Wed, 20 Mar 2019 13:58:06 +0100 (CET) Date: Wed, 20 Mar 2019 13:58:06 +0100 From: Jan Kara To: stable@vger.kernel.org Cc: Jens Axboe , linux-block@vger.kernel.org Subject: Revert commit 310ca162d77 Message-ID: <20190320125806.GD9485@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 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. 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... Honza [1] https://bugzilla.suse.com/show_bug.cgi?id=1129739 -- Jan Kara SUSE Labs, CR