From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753896AbeDIRAq (ORCPT ); Mon, 9 Apr 2018 13:00:46 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:49466 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753463AbeDIRAp (ORCPT ); Mon, 9 Apr 2018 13:00:45 -0400 Date: Mon, 9 Apr 2018 19:00:36 +0200 (CEST) From: Sebastian Ott X-X-Sender: sebott@schleppi To: Kees Cook cc: Sebastian Ott , Linus Torvalds , LKML , Heiko Carstens , Martin Uecker , Ingo Molnar , Miguel Ojeda Subject: Re: [bisected] 3c8ba0d61d04ced9f8d9ff93977995a9e4e96e91 oopses on s390 In-Reply-To: References: User-Agent: Alpine 2.21 (LFD 202 2017-01-01) Organization: =?ISO-8859-15?Q?=22IBM_Deutschland_Research_&_Development_GmbH?= =?ISO-8859-15?Q?_=2F_Vorsitzende_des_Aufsichtsrats=3A_Martina?= =?ISO-8859-15?Q?_Koederitz_Gesch=E4ftsf=FChrung=3A_Dirk_Wittkopp?= =?ISO-8859-15?Q?_Sitz_der_Gesellschaft=3A_B=F6blingen_=2F_Reg?= =?ISO-8859-15?Q?istergericht=3A_Amtsgericht_Stuttgart=2C_HRB_2432?= =?ISO-8859-15?Q?94=22?= MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="-1463805262-326909844-1523293237=:1698" X-TM-AS-GCONF: 00 x-cbid: 18040917-0020-0000-0000-0000040FCD94 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18040917-0021-0000-0000-000042A3EF2E Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-04-09_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=3 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1804090174 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. ---1463805262-326909844-1523293237=:1698 Content-Type: text/plain; charset=US-ASCII On Mon, 9 Apr 2018, Sebastian Ott wrote: > On Fri, 6 Apr 2018, Kees Cook wrote: > > On Fri, Apr 6, 2018 at 2:47 AM, Sebastian Ott wrote: > > > Today's kernel oopsed on s390. Bisect points to: > > > 3c8ba0d61d04 ("kernel.h: Retain constant expression output for max()/min()") > > > > > > [ 1.898277] dasd-eckd 0.0.3304: DASD with 4 KB/block, 21636720 KB total size, 48 KB/track, compatible disk layout > > > [ 1.898308] ------------[ cut here ]------------ > > > [ 1.898310] kernel BUG at block/bio.c:1798! > > > > Well that's extremely bad. :( > > What happened is that the bio build by the partition detection code was > attempted to be split by the block layer because the block queue had a > max_sector setting of 0. blk_queue_max_hw_sectors uses min_not_zero. > > Both of the following return 0 on my machine: > + pr_warn("%u\n", min_not_zero(100, 1000)); > + pr_warn("%u\n", min_not_zero(1000, 100)); > > So, we now know what failed...the question is why? I copied these macros to a userspace program to easily test it on other machines/compilers. ....maybe I did something wrong but min_not_zero did not work - even on fedora on an x86 laptop. 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