From patchwork Tue Jul 2 21:02:02 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Benjamin Block X-Patchwork-Id: 11028781 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 587BC13B1 for ; Wed, 3 Jul 2019 00:43:01 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4F6402892A for ; Wed, 3 Jul 2019 00:43:01 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 432842892D; Wed, 3 Jul 2019 00:43:01 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C100D2892A for ; Wed, 3 Jul 2019 00:43:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727093AbfGCAnA (ORCPT ); Tue, 2 Jul 2019 20:43:00 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:35844 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726736AbfGCAnA (ORCPT ); Tue, 2 Jul 2019 20:43:00 -0400 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x62L1ZO2007995 for ; Tue, 2 Jul 2019 17:02:09 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0b-001b2d01.pphosted.com with ESMTP id 2tgax7g97k-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 02 Jul 2019 17:02:09 -0400 Received: from localhost by e06smtp02.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, 2 Jul 2019 22:02:06 +0100 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x62L24fV59965592 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 2 Jul 2019 21:02:04 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 58BE2AE051; Tue, 2 Jul 2019 21:02:04 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4486BAE045; Tue, 2 Jul 2019 21:02:04 +0000 (GMT) Received: from t480-pf1aa2c2 (unknown [9.145.93.34]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Tue, 2 Jul 2019 21:02:04 +0000 (GMT) Received: from bblock by t480-pf1aa2c2 with local (Exim 4.92) (envelope-from ) id 1hiPud-0007zj-Fx; Tue, 02 Jul 2019 23:02:03 +0200 From: Benjamin Block To: "James E.J. Bottomley" , "Martin K. Petersen" Cc: Benjamin Block , Steffen Maier , Fedor Loshakov , Jens Remus , Heiko Carstens , Vasily Gorbik , linux-scsi@vger.kernel.org, linux-s390@vger.kernel.org Subject: [PATCH 3/3] zfcp: fix GCC compiler warning emitted with -Wmaybe-uninitialized Date: Tue, 2 Jul 2019 23:02:02 +0200 X-Mailer: git-send-email 2.20.1 In-Reply-To: References: MIME-Version: 1.0 X-TM-AS-GCONF: 00 x-cbid: 19070221-0008-0000-0000-000002F93B9E X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19070221-0009-0000-0000-00002266865D Message-Id: <8d531fd6170e5dbc4908bddda28f8f80f7312019.1562098940.git.bblock@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-07-02_10:,, 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=946 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1907020233 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP GCC v9 emits this warning: CC drivers/s390/scsi/zfcp_erp.o drivers/s390/scsi/zfcp_erp.c: In function 'zfcp_erp_action_enqueue': drivers/s390/scsi/zfcp_erp.c:217:26: warning: 'erp_action' may be used uninitialized in this function [-Wmaybe-uninitialized] 217 | struct zfcp_erp_action *erp_action; | ^~~~~~~~~~ This is a possible false positive case, as also documented in the GCC documentations: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wmaybe-uninitialized The actual code-sequence is like this: Various callers can invoke the function below with the argument "want" being one of: ZFCP_ERP_ACTION_REOPEN_ADAPTER, ZFCP_ERP_ACTION_REOPEN_PORT_FORCED, ZFCP_ERP_ACTION_REOPEN_PORT, or ZFCP_ERP_ACTION_REOPEN_LUN. zfcp_erp_action_enqueue(want, ...) ... need = zfcp_erp_required_act(want, ...) need = want ... maybe: need = ZFCP_ERP_ACTION_REOPEN_PORT maybe: need = ZFCP_ERP_ACTION_REOPEN_ADAPTER ... return need ... zfcp_erp_setup_act(need, ...) struct zfcp_erp_action *erp_action; // <== line 217 ... switch(need) { case ZFCP_ERP_ACTION_REOPEN_LUN: ... erp_action = &zfcp_sdev->erp_action; WARN_ON_ONCE(erp_action->port != port); // <== access ... break; case ZFCP_ERP_ACTION_REOPEN_PORT: case ZFCP_ERP_ACTION_REOPEN_PORT_FORCED: ... erp_action = &port->erp_action; WARN_ON_ONCE(erp_action->port != port); // <== access ... break; case ZFCP_ERP_ACTION_REOPEN_ADAPTER: ... erp_action = &adapter->erp_action; WARN_ON_ONCE(erp_action->port != NULL); // <== access ... break; } ... WARN_ON_ONCE(erp_action->adapter != adapter); // <== access When zfcp_erp_setup_act() is called, 'need' will never be anything else than one of the 4 possible enumeration-names that are used in the switch-case, and 'erp_action' is initialized for every one of them, before it is used. Thus the warning is a false positive, as documented. We introduce the extra if{} in the beginning to create an extra code-flow, so the compiler can be convinced that the switch-case will never see any other value. BUG_ON()/BUG() is intentionally not used to not crash anything, should this ever happen anyway - right now it's impossible, as argued above; and it doesn't introduce a 'default:' switch-case to retain warnings should 'enum zfcp_erp_act_type' ever be extended and no explicit case be introduced. See also v5.0 commit 399b6c8bc9f7 ("scsi: zfcp: drop old default switch case which might paper over missing case"). Signed-off-by: Benjamin Block Reviewed-by: Jens Remus Reviewed-by: Steffen Maier --- drivers/s390/scsi/zfcp_erp.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/s390/scsi/zfcp_erp.c b/drivers/s390/scsi/zfcp_erp.c index e8fc28dba8df..96f0d34e9459 100644 --- a/drivers/s390/scsi/zfcp_erp.c +++ b/drivers/s390/scsi/zfcp_erp.c @@ -11,6 +11,7 @@ #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt #include +#include #include "zfcp_ext.h" #include "zfcp_reqlist.h" @@ -217,6 +218,12 @@ static struct zfcp_erp_action *zfcp_erp_setup_act(enum zfcp_erp_act_type need, struct zfcp_erp_action *erp_action; struct zfcp_scsi_dev *zfcp_sdev; + if (WARN_ON_ONCE(need != ZFCP_ERP_ACTION_REOPEN_LUN && + need != ZFCP_ERP_ACTION_REOPEN_PORT && + need != ZFCP_ERP_ACTION_REOPEN_PORT_FORCED && + need != ZFCP_ERP_ACTION_REOPEN_ADAPTER)) + return NULL; + switch (need) { case ZFCP_ERP_ACTION_REOPEN_LUN: zfcp_sdev = sdev_to_zfcp(sdev);