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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 D2B33C352AA for ; Tue, 1 Oct 2019 15:42:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AA6F821855 for ; Tue, 1 Oct 2019 15:42:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1569944532; bh=k0W7e2si2Vcx0gzomk1QiHlnoTpUZarg+lyFE5CNArg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=af4dPzgBhLhf82dltpzcLwQTD45ZbjCu2x+c84UvKQYM5vSG5izHwQoTFNQdBujIW slP5ntlUJDShN8nMAzhWGYWnxSrugu8VmbRLO34xqFmdNo5vIBUSiqO2m/qayLBMYE JlbusI3KvKgTuqNvSnV6mbyVzplnjDpOWVURfxqU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389468AbfJAPmM (ORCPT ); Tue, 1 Oct 2019 11:42:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:58916 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727302AbfJAPmL (ORCPT ); Tue, 1 Oct 2019 11:42:11 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.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 B00352086A; Tue, 1 Oct 2019 15:42:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1569944531; bh=k0W7e2si2Vcx0gzomk1QiHlnoTpUZarg+lyFE5CNArg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QEeD2au9hZKSmGTMJEvCv0/W91JbZIahSo/L5PKLMeNcK9Vk8Ov0I6pzy/rEOS5v/ 5Jshb/XjslEJTsZJRrx+g+XQN3oVFKa+w0hldEW3rOZyK80e9p2bDksdq8+MPoB17x N5LHM94n5hxWVo+ggHILwM07rhYla7CPMxgJQddM= Date: Tue, 1 Oct 2019 17:42:08 +0200 From: Greg KH To: Steffen Maier Cc: "James E . J . Bottomley" , "Martin K . Petersen" , linux-scsi@vger.kernel.org, linux-s390@vger.kernel.org, Benjamin Block , Heiko Carstens , Vasily Gorbik , stable@vger.kernel.org Subject: Re: [PATCH v2] zfcp: fix reaction on bit error theshold notification with adapter close Message-ID: <20191001154208.GB3523275@kroah.com> References: <20191001104949.42810-1-maier@linux.ibm.com> <20191001141408.GB3129841@kroah.com> <71b8fc68-23a8-a591-1018-f290d6e3312a@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <71b8fc68-23a8-a591-1018-f290d6e3312a@linux.ibm.com> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On Tue, Oct 01, 2019 at 05:07:50PM +0200, Steffen Maier wrote: > On 10/1/19 4:14 PM, Greg KH wrote: > > On Tue, Oct 01, 2019 at 12:49:49PM +0200, Steffen Maier wrote: > > > On excessive bit errors for the FCP channel ingress fibre path, the channel > > > notifies us. Previously, we only emitted a kernel message and a trace record. > > > Since performance can become suboptimal with I/O timeouts due to > > > bit errors, we now stop using an FCP device by default on channel > > > notification so multipath on top can timely failover to other paths. > > > A new module parameter zfcp.ber_stop can be used to get zfcp old behavior. > > > > Ugh, module parameters? This isn't the 1990's anymore :( > > > > Why not just make this a dynamic sysfs variable, that way you properly > > can set this on whatever device you want, not just "all or nothing"? > > Since we can see many more (virtual) FCP devices than we want to actually > use, we defer probing. It means, we only start allocating structures and > sysfs entries on setting an FCP "online" for the first time. Setting online > works through another sysfs attribute owned by our ccw bus code component > called "cio". IIRC, setting online does not emit a uevent. On setting > online, the (add) uevent of hot-/coldplug of an FCP device had already > happened, so we could not easily have end users craft udev rules to > automatically/persistently configure a new sysfs attribute (which is > FCP-device-specific and appears late) to disable the new code behavior. > > Not sure if that could ever become a problem for end users: Even if we were > to write into a new sysfs attribute, the attribute only appears during > setting online so this might race with starting to actually use the FCP > device with the new default behavior and could potentially disable I/O paths > before the sysfs attribute write could become effective to disable the new > behavor. Ok, then why make this a module option that you will have to support for the next 20+ years anyway if you feel this fix is the correct way that it should be done instead? module options are tough to manage and support, only add them as a very last thing, when all other options have been ruled out. thanks, greg k-h