Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752996AbbKVXUP (ORCPT ); Sun, 22 Nov 2015 18:20:15 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33952 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752773AbbKVXUN (ORCPT ); Sun, 22 Nov 2015 18:20:13 -0500 Message-ID: <1448234410.8209.3.camel@redhat.com> Subject: Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! From: Mark Salter To: Ming Lei , Laurent Dufour Cc: Michael Ellerman , Christoph Hellwig , "James E. J. Bottomley" , brking , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-block@vger.kernel.org, tom.leiming@gmail.com Date: Sun, 22 Nov 2015 18:20:10 -0500 In-Reply-To: <20151122005635.1b9ffbe1@tom-T450> References: <1447838334.1564.2.camel@ellerman.id.au> <1447855399.3974.24.camel@redhat.com> <1447894964.15206.0.camel@ellerman.id.au> <20151119082325.GA11419@infradead.org> <1448021448.14769.7.camel@ellerman.id.au> <565055C6.5040801@linux.vnet.ibm.com> <20151122005635.1b9ffbe1@tom-T450> Organization: Red Hat, Inc Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2784 Lines: 80 On Sun, 2015-11-22 at 00:56 +0800, Ming Lei wrote: > On Sat, 21 Nov 2015 12:30:14 +0100 > Laurent Dufour wrote: > > > On 20/11/2015 13:10, Michael Ellerman wrote: > > > On Thu, 2015-11-19 at 00:23 -0800, Christoph Hellwig wrote: > > > > > > > It's pretty much guaranteed a block layer bug, most likely in the > > > > merge bios to request infrastucture where we don't obey the merging > > > > limits properly. > > > > > > > > Does either of you have a known good and first known bad kernel? > > > > > > Not me, I've only hit it one or two times. All I can say is I have hit it in > > > 4.4-rc1. > > > > > > Laurent, can you narrow it down at all? > > > > It seems that the panic is triggered by the commit bdced438acd8 ("block: > > setup bi_phys_segments after splitting") which has been pulled by the > > merge d9734e0d1ccf ("Merge branch 'for-4.4/core' of > > git://git.kernel.dk/linux-block"). > > > > My system is panicing promptly when running a kernel built at > > d9734e0d1ccf, while reverting the commit bdced438acd8, it can run hours > > without panicing. > > > > This being said, I can't explain what's going wrong. > > > > May Ming shed some light here ? > > Laurent, looks there is one bug in blk_bio_segment_split(), would you > mind testing the following patch to see if it fixes your issue? > > --- > From 6fc701231dcc000bc8bc4b9105583380d9aa31f4 Mon Sep 17 00:00:00 2001 > From: Ming Lei > Date: Sun, 22 Nov 2015 00:47:13 +0800 > Subject: [PATCH] block: fix segment split > > Inside blk_bio_segment_split(), previous bvec pointer('bvprvp') > always points to the iterator local variable, which is obviously > wrong, so fix it by pointing to the local variable of 'bvprv'. > > Signed-off-by: Ming Lei > --- >  block/blk-merge.c | 4 ++-- >  1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/block/blk-merge.c b/block/blk-merge.c > index de5716d8..f2efe8a 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -98,7 +98,7 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, >   >   seg_size += bv.bv_len; >   bvprv = bv; > - bvprvp = &bv; > + bvprvp = &bvprv; >   sectors += bv.bv_len >> 9; >   continue; >   } > @@ -108,7 +108,7 @@ new_segment: >   >   nsegs++; >   bvprv = bv; > - bvprvp = &bv; > + bvprvp = &bvprv; >   seg_size = bv.bv_len; >   sectors += bv.bv_len >> 9; >   } I'm still hitting the BUG even with this patch applied on top of 4.4-rc1. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/