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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 6F33FC47404 for ; Fri, 4 Oct 2019 11:02:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 42BD820867 for ; Fri, 4 Oct 2019 11:02:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730394AbfJDLCD (ORCPT ); Fri, 4 Oct 2019 07:02:03 -0400 Received: from mga09.intel.com ([134.134.136.24]:54953 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725788AbfJDLCD (ORCPT ); Fri, 4 Oct 2019 07:02:03 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Oct 2019 04:01:55 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,256,1566889200"; d="scan'208";a="205829698" Received: from lahna.fi.intel.com (HELO lahna) ([10.237.72.157]) by fmsmga001.fm.intel.com with SMTP; 04 Oct 2019 04:01:52 -0700 Received: by lahna (sSMTP sendmail emulation); Fri, 04 Oct 2019 14:01:51 +0300 Date: Fri, 4 Oct 2019 14:01:51 +0300 From: Mika Westerberg To: "Rafael J. Wysocki" Cc: Tejun Heo , "Rafael J. Wysocki" , AceLan Kao , Jens Axboe , Jan Kara , Greg Kroah-Hartman , linux-kernel@vger.kernel.org Subject: Re: System hangs if NVMe/SSD is removed during suspend Message-ID: <20191004110151.GH2819@lahna.fi.intel.com> References: <20191002122136.GD2819@lahna.fi.intel.com> <20191003165033.GC3247445@devbig004.ftw2.facebook.com> <20191004080340.GB2819@lahna.fi.intel.com> <2367934.HCQFgJ56tP@kreacher> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2367934.HCQFgJ56tP@kreacher> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 04, 2019 at 11:59:26AM +0200, Rafael J. Wysocki wrote: > On Friday, October 4, 2019 10:03:40 AM CEST Mika Westerberg wrote: > > On Thu, Oct 03, 2019 at 09:50:33AM -0700, Tejun Heo wrote: > > > Hello, Mika. > > > > > > On Wed, Oct 02, 2019 at 03:21:36PM +0300, Mika Westerberg wrote: > > > > but from that discussion I don't see more generic solution to be > > > > implemented. > > > > > > > > Any ideas we should fix this properly? > > > > > > Yeah, the only fix I can think of is not using freezable wq. It's > > > just not a good idea and not all that difficult to avoid using. > > > > OK, thanks. > > > > In that case I will just make a patch that removes WQ_FREEZABLE from > > bdi_wq and see what people think about it :) > > I guess that depends on why WQ_FREEZABLE was added to it in the first place. :-) > > The reason might be to avoid writes to persistent storage after creating an > image during hibernation, since wqs remain frozen throughout the entire > hibernation including the image saving phase. Good point. > Arguably, making the wq freezable is kind of a sledgehammer approach to that > particular issue, but in principle it may prevent data corruption from > occurring, so be careful there. I tried to find the commit that introduced the "freezing" and I think it is this one: 03ba3782e8dc writeback: switch to per-bdi threads for flushing data Unfortunately from that commit it is not clear (at least to me) why it calls set_freezable() for the bdi task. It does not look like it has anything to do with blocking writes to storage while entering hibernation but I may be mistaken.