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Thu, 3 Oct 2019 14:01:14 +0000 Received: from DM5PR15MB1290.namprd15.prod.outlook.com ([fe80::7931:b386:1db:7e6e]) by DM5PR15MB1290.namprd15.prod.outlook.com ([fe80::7931:b386:1db:7e6e%3]) with mapi id 15.20.2305.023; Thu, 3 Oct 2019 14:01:13 +0000 From: Chris Mason To: Gao Xiang CC: Dave Chinner , "Darrick J. Wong" , xfs , "tj@kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-block@vger.kernel.org" Subject: Re: [5.4-rc1, regression] wb_workfn wakeup oops (was Re: frequent 5.4-rc1 crash?) Thread-Topic: [5.4-rc1, regression] wb_workfn wakeup oops (was Re: frequent 5.4-rc1 crash?) Thread-Index: AQHVebV9yjzYkcmTjkGpczdk1UiqcKdImWgAgABZMoA= Date: Thu, 3 Oct 2019 14:01:13 +0000 Message-ID: <41B90CA7-E093-48FA-BDFD-73BE7EB81FB6@fb.com> References: <20191003015247.GI13108@magnolia> <20191003064022.GX16973@dread.disaster.area> <20191003084149.GA16347@hsiangkao-HP-ZHAN-66-Pro-G1> In-Reply-To: <20191003084149.GA16347@hsiangkao-HP-ZHAN-66-Pro-G1> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: MailMate (1.13r5655) x-clientproxiedby: BN6PR2201CA0007.namprd22.prod.outlook.com (2603:10b6:405:5e::20) To DM5PR15MB1290.namprd15.prod.outlook.com (2603:10b6:3:b8::17) x-ms-exchange-messagesentrepresentingtype: 1 x-originating-ip: [2620:10d:c091:480::38af] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 6d9e79e6-5c2c-4dc3-6d01-08d7480a26e6 x-ms-traffictypediagnostic: DM5PR15MB1273: x-ms-exchange-purlcount: 1 x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:8882; x-forefront-prvs: 01792087B6 x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(376002)(396003)(39860400002)(136003)(366004)(346002)(53754006)(199004)(189003)(33656002)(50226002)(6486002)(6506007)(7736002)(386003)(966005)(66446008)(86362001)(71200400001)(71190400001)(81166006)(25786009)(8676002)(81156014)(8936002)(14454004)(66556008)(6916009)(5660300002)(36756003)(66476007)(66946007)(64756008)(4326008)(99286004)(446003)(11346002)(54906003)(46003)(316002)(486006)(2616005)(476003)(186003)(6116002)(478600001)(76176011)(6436002)(305945005)(14444005)(256004)(53546011)(6306002)(6246003)(6512007)(2906002)(102836004)(229853002)(52116002);DIR:OUT;SFP:1102;SCL:1;SRVR:DM5PR15MB1273;H:DM5PR15MB1290.namprd15.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:1;MX:1; received-spf: None (protection.outlook.com: fb.com does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: O3VaQZG04LlOL3q8Ww1vTyBElfxYXVXNqNnmrbpWYM6IFW9JyTWQJHOEz9kaGY1ol4lcWp3F+WejwljX9J2MeQ28N1awPu8mxX2yd3ZQWZRp3mrGt4dCq28vwMBTRr2awg9p2/ibgnTf2dLceyMK4hV4CfwYbp9eYgsMT8ly1YOZKHGWwc/mJLzh/pyJy7CaSF8n6cLog+XRJoyPC0OwRwjngYFcqu0S0LOir//3dMug8mX+MRYuuGB9LCH2jvFg64hOZIP0CZEmHJduWdJjfecaqS/0BGHSdgdmrfCsOQH33804g5P3P8KQOIjCTO3bYKin50CL95V96rQJfWnWrS61xsnLXmg8HU4NgIyGSFv6CtxBrgn9ap0XSunOX9hpYL+FkdnWDDX/GJugUFEvuxwDvTqVyZ+8XhF4xjJA1kGMWmmmdj9AFTw4wKpBf1DzUJnxzmGII959PhGH+HA0cg== x-ms-exchange-transport-forked: True Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 6d9e79e6-5c2c-4dc3-6d01-08d7480a26e6 X-MS-Exchange-CrossTenant-originalarrivaltime: 03 Oct 2019 14:01:13.8241 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: XSts73a3T5xzGtyUczUhYmzqqsh1j8zN0Cug3sjSdzEaCB9hWPOLRZynBadyDFpe X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR15MB1273 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,1.0.8 definitions=2019-10-03_05:2019-10-03,2019-10-03 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 phishscore=0 suspectscore=0 spamscore=0 impostorscore=0 adultscore=0 priorityscore=1501 lowpriorityscore=0 bulkscore=0 mlxlogscore=876 mlxscore=0 clxscore=1011 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1908290000 definitions=main-1910030132 X-FB-Internal: deliver Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On 3 Oct 2019, at 4:41, Gao Xiang wrote: > Hi, > > On Thu, Oct 03, 2019 at 04:40:22PM +1000, Dave Chinner wrote: >> [cc linux-fsdevel, linux-block, tejun ] >> >> On Wed, Oct 02, 2019 at 06:52:47PM -0700, Darrick J. Wong wrote: >>> Hi everyone, >>> >>> Does anyone /else/ see this crash in generic/299 on a V4 filesystem=20 >>> (tho >>> afaict V5 configs crash too) and a 5.4-rc1 kernel? It seems to pop=20 >>> up >>> on generic/299 though only 80% of the time. >>> > > Just a quick glance, I guess there could is a race between (complete=20 > guess): > > > 160 static void finish_writeback_work(struct bdi_writeback *wb, > 161 struct wb_writeback_work *work) > 162 { > 163 struct wb_completion *done =3D work->done; > 164 > 165 if (work->auto_free) > 166 kfree(work); > 167 if (done && atomic_dec_and_test(&done->cnt)) > > ^^^ here > > 168 wake_up_all(done->waitq); > 169 } > > since new wake_up_all(done->waitq); is completely on-stack, > if (done && atomic_dec_and_test(&done->cnt)) > - wake_up_all(&wb->bdi->wb_waitq); > + wake_up_all(done->waitq); > } > > which could cause use after free if on-stack wb_completion is gone... > (however previous wb->bdi is solid since it is not on-stack) > > see generic on-stack completion which takes a wait_queue spin_lock=20 > between > test and wake_up... > > If I am wrong, ignore me, hmm... It's a good guess ;) Jens should have this queued up already: https://lkml.org/lkml/2019/9/23/972 -chris