From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from youngberry.canonical.com (youngberry.canonical.com [91.189.89.112]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 104D11A0100 for ; Sun, 22 Nov 2015 03:57:30 +1100 (AEDT) Date: Sun, 22 Nov 2015 00:56:35 +0800 From: Ming Lei To: Laurent Dufour Cc: Michael Ellerman , Christoph Hellwig , Mark Salter , "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 Subject: Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Message-ID: <20151122005635.1b9ffbe1@tom-T450> In-Reply-To: <565055C6.5040801@linux.vnet.ibm.com> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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: > >=20 > >> 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? > >=20 > > Not me, I've only hit it one or two times. All I can say is I have hit = it in > > 4.4-rc1. > >=20 > > Laurent, can you narrow it down at all? >=20 > 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"). >=20 > My system is panicing promptly when running a kernel built at > d9734e0d1ccf, while reverting the commit bdced438acd8, it can run hours > without panicing. >=20 > This being said, I can't explain what's going wrong. >=20 > 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? --- =46rom 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_q= ueue *q, =20 seg_size +=3D bv.bv_len; bvprv =3D bv; - bvprvp =3D &bv; + bvprvp =3D &bvprv; sectors +=3D bv.bv_len >> 9; continue; } @@ -108,7 +108,7 @@ new_segment: =20 nsegs++; bvprv =3D bv; - bvprvp =3D &bv; + bvprvp =3D &bvprv; seg_size =3D bv.bv_len; sectors +=3D bv.bv_len >> 9; } --=20 1.9.1 Thanks, Ming