From patchwork Sat Nov 21 16:56:35 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 547244 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 13359140281 for ; Sun, 22 Nov 2015 09:10:03 +1100 (AEDT) Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id E7C271A038D for ; Sun, 22 Nov 2015 09:10:02 +1100 (AEDT) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org 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) Received: from [103.192.227.7] (helo=tom-T450) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.76) (envelope-from ) id 1a0BTJ-00047S-4O; Sat, 21 Nov 2015 16:57:09 +0000 Date: Sun, 22 Nov 2015 00:56:35 +0800 From: Ming Lei To: Laurent Dufour 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> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.23; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-Mailman-Approved-At: Sun, 22 Nov 2015 09:09:07 +1100 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-block@vger.kernel.org, tom.leiming@gmail.com, linux-scsi@vger.kernel.org, "James E. J. Bottomley" , linux-kernel@vger.kernel.org, Christoph Hellwig , brking , Mark Salter , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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; }