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=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 96DA7ECE587 for ; Tue, 1 Oct 2019 15:08:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 721DD21855 for ; Tue, 1 Oct 2019 15:08:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389377AbfJAPIA (ORCPT ); Tue, 1 Oct 2019 11:08:00 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:6988 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731937AbfJAPH7 (ORCPT ); Tue, 1 Oct 2019 11:07:59 -0400 Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x91F3s1J022204 for ; Tue, 1 Oct 2019 11:07:58 -0400 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0a-001b2d01.pphosted.com with ESMTP id 2vc6t1eaj1-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 01 Oct 2019 11:07:57 -0400 Received: from localhost by e06smtp05.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 1 Oct 2019 16:07:52 +0100 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x91F7MEq29819342 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 1 Oct 2019 15:07:22 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D55EBA4055; Tue, 1 Oct 2019 15:07:50 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8033EA4051; Tue, 1 Oct 2019 15:07:50 +0000 (GMT) Received: from oc4120165700.ibm.com (unknown [9.152.98.61]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 1 Oct 2019 15:07:50 +0000 (GMT) From: Steffen Maier Subject: Re: [PATCH v2] zfcp: fix reaction on bit error theshold notification with adapter close To: Greg KH 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 References: <20191001104949.42810-1-maier@linux.ibm.com> <20191001141408.GB3129841@kroah.com> Date: Tue, 1 Oct 2019 17:07:50 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20191001141408.GB3129841@kroah.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19100115-0020-0000-0000-000003740055 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19100115-0021-0000-0000-000021CA0046 Message-Id: <71b8fc68-23a8-a591-1018-f290d6e3312a@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-10-01_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910010136 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org 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. -- Mit freundlichen Gruessen / Kind regards Steffen Maier Linux on IBM Z Development https://www.ibm.com/privacy/us/en/ IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Matthias Hartmann Geschaeftsfuehrung: Dirk Wittkopp Sitz der Gesellschaft: Boeblingen Registergericht: Amtsgericht Stuttgart, HRB 243294