From patchwork Thu Sep 10 19:49:15 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Benjamin Block X-Patchwork-Id: 296786 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=-12.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 D19C1C43461 for ; Thu, 10 Sep 2020 19:50:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 851C7221E2 for ; Thu, 10 Sep 2020 19:50:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="WQv2kH61" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726828AbgIJTuT (ORCPT ); Thu, 10 Sep 2020 15:50:19 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:5760 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726760AbgIJTta (ORCPT ); Thu, 10 Sep 2020 15:49:30 -0400 Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 08AJUibe002714; Thu, 10 Sep 2020 15:49:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : sender; s=pp1; bh=2d010pYJBFiT9ncMmOMK+RtKaeSGGAVRGdxZl9MMv2A=; b=WQv2kH61Z+Mfc/FLijymod/7hI2nQJLTEeN7HZNWCfo5NjoyvDYXDmBlyqfErJsp/2z9 LChG0MyfIQ0igvoYWsO8bKPa6hRhhz4aCuEcVURHSZnN2UVyBFg7HbNCJ2nDXDlhpbS+ rhdXYOWmPTAM6EJWkaY9Q4Yscl1/2FgdAswG4Z0h22A61HU6pwxoZHrmRWNJdceVOKrU F27yrMNvKBuvWRKa1VP55QLGuEhRntIcmATEa8rdksNgGG7T8T/aIMANjns0VpaacX7N P+sqdJd/bpkHOT9WSu0AgO9Zeq2sK2LyHXNSnhzUvrhKPE//pmzF3FBjUz6zwpe0BMQQ 2w== Received: from ppma05fra.de.ibm.com (6c.4a.5195.ip4.static.sl-reverse.com [149.81.74.108]) by mx0b-001b2d01.pphosted.com with ESMTP id 33frwhb8x7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 10 Sep 2020 15:49:25 -0400 Received: from pps.filterd (ppma05fra.de.ibm.com [127.0.0.1]) by ppma05fra.de.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 08AJn2lL003388; Thu, 10 Sep 2020 19:49:23 GMT Received: from b06cxnps4074.portsmouth.uk.ibm.com (d06relay11.portsmouth.uk.ibm.com [9.149.109.196]) by ppma05fra.de.ibm.com with ESMTP id 33f3yrgrem-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 10 Sep 2020 19:49:22 +0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 08AJnJHT15663384 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 10 Sep 2020 19:49:19 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C65774C040; Thu, 10 Sep 2020 19:49:19 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B2C364C044; Thu, 10 Sep 2020 19:49:19 +0000 (GMT) Received: from t480-pf1aa2c2 (unknown [9.145.32.17]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Thu, 10 Sep 2020 19:49:19 +0000 (GMT) Received: from bblock by t480-pf1aa2c2 with local (Exim 4.94) (envelope-from ) id 1kGSZJ-00AFA0-8s; Thu, 10 Sep 2020 21:49:17 +0200 From: Benjamin Block To: "James E.J. Bottomley" , "Martin K. Petersen" Cc: Julian Wiedmann , Benjamin Block , Steffen Maier , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Fedor Loshakov , linux-scsi@vger.kernel.org, linux-s390@vger.kernel.org Subject: [PATCH 1/2] zfcp: use list_first_entry_or_null() in zfcp_erp_thread() Date: Thu, 10 Sep 2020 21:49:15 +0200 Message-Id: X-Mailer: git-send-email 2.26.2 In-Reply-To: References: MIME-Version: 1.0 Organization: IBM Deutschland Research & Development GmbH, Vorsitz. AufsR. Gregor Pillen, Geschaeftsfuehrung Dirk Wittkopp, Sitz der Gesellschaft Boeblingen, Registergericht AmtsG Stuttgart, HRB 243294 X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-09-10_08:2020-09-10,2020-09-10 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 adultscore=0 clxscore=1015 mlxlogscore=991 mlxscore=0 spamscore=0 lowpriorityscore=0 priorityscore=1501 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009100173 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org From: Julian Wiedmann Use the right helper to avoid poking around in the list's internals. Signed-off-by: Julian Wiedmann Reviewed-by: Steffen Maier Reviewed-by: Benjamin Block Signed-off-by: Benjamin Block --- drivers/s390/scsi/zfcp_erp.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/drivers/s390/scsi/zfcp_erp.c b/drivers/s390/scsi/zfcp_erp.c index 59e662df5774..78d52a4c55f5 100644 --- a/drivers/s390/scsi/zfcp_erp.c +++ b/drivers/s390/scsi/zfcp_erp.c @@ -1607,7 +1607,6 @@ static enum zfcp_erp_act_result zfcp_erp_strategy( static int zfcp_erp_thread(void *data) { struct zfcp_adapter *adapter = (struct zfcp_adapter *) data; - struct list_head *next; struct zfcp_erp_action *act; unsigned long flags; @@ -1620,12 +1619,11 @@ static int zfcp_erp_thread(void *data) break; write_lock_irqsave(&adapter->erp_lock, flags); - next = adapter->erp_ready_head.next; + act = list_first_entry_or_null(&adapter->erp_ready_head, + struct zfcp_erp_action, list); write_unlock_irqrestore(&adapter->erp_lock, flags); - if (next != &adapter->erp_ready_head) { - act = list_entry(next, struct zfcp_erp_action, list); - + if (act) { /* there is more to come after dismission, no notify */ if (zfcp_erp_strategy(act) != ZFCP_ERP_DISMISSED) zfcp_erp_wakeup(adapter); From patchwork Thu Sep 10 19:49:16 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Benjamin Block X-Patchwork-Id: 257668 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=-12.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 29B47C2D0A7 for ; Thu, 10 Sep 2020 19:50:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E5FDC21D81 for ; Thu, 10 Sep 2020 19:50:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="ikuJDct3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726384AbgIJTuR (ORCPT ); Thu, 10 Sep 2020 15:50:17 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:50446 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726847AbgIJTta (ORCPT ); Thu, 10 Sep 2020 15:49:30 -0400 Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 08AJUs5L122237; Thu, 10 Sep 2020 15:49:23 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : sender; s=pp1; bh=i7JBPvdd60neM6rxo1EKqoMekpXsXBVik7L2XppxG1Q=; b=ikuJDct3ysKrb2mciuEJ//WpQuEpAo3o9o5yQTM5OvoelLzgdok9bS8MfIMlP32fFGTY seq2XZB+0fqKDKbgDTjrXPcssBLvVXpxE9soKUHinSBCEBF9t+JTvPctRzlpDcw/cmXB GYIy1p90Od0AbmGszGC9onu/QZe89I6r/v+Mye2g2iLKtdPYEokfKH4V5W5G3p87q9IA U/3utru3zVKMzlnW5bodPk0Gn19D6T2bKrFBuhkNjQDTA4hgiNkPmOCjRf59XrzkyU2V bnRrar9AmlyhNEuSkckyOPhMwtuGJomV6IZStxjWJ/KUn+uBqO8k1pi0jpTxCmfS1kHr NA== Received: from ppma03ams.nl.ibm.com (62.31.33a9.ip4.static.sl-reverse.com [169.51.49.98]) by mx0b-001b2d01.pphosted.com with ESMTP id 33fqts5mbt-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 10 Sep 2020 15:49:23 -0400 Received: from pps.filterd (ppma03ams.nl.ibm.com [127.0.0.1]) by ppma03ams.nl.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 08AJm3Um007401; Thu, 10 Sep 2020 19:49:21 GMT Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by ppma03ams.nl.ibm.com with ESMTP id 33c2a86df4-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 10 Sep 2020 19:49:21 +0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 08AJnIfo30736648 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 10 Sep 2020 19:49:18 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A29B6A4064; Thu, 10 Sep 2020 19:49:18 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8DF38A4054; Thu, 10 Sep 2020 19:49:18 +0000 (GMT) Received: from t480-pf1aa2c2 (unknown [9.145.32.17]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Thu, 10 Sep 2020 19:49:18 +0000 (GMT) Received: from bblock by t480-pf1aa2c2 with local (Exim 4.94) (envelope-from ) id 1kGSZJ-00AFA2-Hz; Thu, 10 Sep 2020 21:49:17 +0200 From: Benjamin Block To: "James E.J. Bottomley" , "Martin K. Petersen" Cc: Julian Wiedmann , Benjamin Block , Steffen Maier , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Fedor Loshakov , linux-scsi@vger.kernel.org, linux-s390@vger.kernel.org Subject: [PATCH 2/2] zfcp: clarify access to erp_action in zfcp_fsf_req_complete() Date: Thu, 10 Sep 2020 21:49:16 +0200 Message-Id: X-Mailer: git-send-email 2.26.2 In-Reply-To: References: MIME-Version: 1.0 Organization: IBM Deutschland Research & Development GmbH, Vorsitz. AufsR. Gregor Pillen, Geschaeftsfuehrung Dirk Wittkopp, Sitz der Gesellschaft Boeblingen, Registergericht AmtsG Stuttgart, HRB 243294 X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-09-10_08:2020-09-10,2020-09-10 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 phishscore=0 mlxlogscore=999 suspectscore=2 clxscore=1015 malwarescore=0 adultscore=0 lowpriorityscore=0 priorityscore=1501 impostorscore=0 bulkscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009100173 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org From: Julian Wiedmann While reviewing commit 936e6b85da04 ("scsi: zfcp: Fix panic on ERP timeout for previously dismissed ERP action"), I stumbled over zfcp_fsf_req_complete() and wondered whether it has similar issues wrt concurrent modification of req->erp_action by zfcp_erp_strategy_check_fsfreq(). But a closer look shows that both its two callers [zfcp_fsf_reqid_check(), zfcp_fsf_req_dismiss_all()] remove the request from the adapter's req_list under the req_list's lock. Hence we can trust that if zfcp_erp_strategy_check_fsfreq() concurrently looks up the corresponding req_id, it won't find this request and is thus unable to modify it while it's being processed by zfcp_fsf_req_complete(). Add a code comment that hopefully makes this easier for future readers, and condense the two accesses to ->erp_action that made me trip over this code path in the first place. Signed-off-by: Julian Wiedmann Reviewed-by: Steffen Maier Reviewed-by: Benjamin Block Signed-off-by: Benjamin Block --- drivers/s390/scsi/zfcp_fsf.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/s390/scsi/zfcp_fsf.c b/drivers/s390/scsi/zfcp_fsf.c index c795f22249d8..d9de26157da2 100644 --- a/drivers/s390/scsi/zfcp_fsf.c +++ b/drivers/s390/scsi/zfcp_fsf.c @@ -426,9 +426,14 @@ static void zfcp_fsf_protstatus_eval(struct zfcp_fsf_req *req) * or it has been dismissed due to a queue shutdown, this function * is called to process the completion status and trigger further * events related to the FSF request. + * Caller must ensure that the request has been removed from + * adapter->req_list, to protect against concurrent modification + * by zfcp_erp_strategy_check_fsfreq(). */ static void zfcp_fsf_req_complete(struct zfcp_fsf_req *req) { + struct zfcp_erp_action *erp_action; + if (unlikely(zfcp_fsf_req_is_status_read_buffer(req))) { zfcp_fsf_status_read_handler(req); return; @@ -439,8 +444,9 @@ static void zfcp_fsf_req_complete(struct zfcp_fsf_req *req) zfcp_fsf_fsfstatus_eval(req); req->handler(req); - if (req->erp_action) - zfcp_erp_notify(req->erp_action, 0); + erp_action = req->erp_action; + if (erp_action) + zfcp_erp_notify(erp_action, 0); if (likely(req->status & ZFCP_STATUS_FSFREQ_CLEANUP)) zfcp_fsf_req_free(req);