From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e06smtp13.uk.ibm.com (e06smtp13.uk.ibm.com [195.75.94.109]) (using TLSv1 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 6ADD71A2A7C for ; Tue, 24 Nov 2015 00:57:38 +1100 (AEDT) Received: from localhost by e06smtp13.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 23 Nov 2015 13:57:34 -0000 Received: from b06cxnps4075.portsmouth.uk.ibm.com (d06relay12.portsmouth.uk.ibm.com [9.149.109.197]) by d06dlp03.portsmouth.uk.ibm.com (Postfix) with ESMTP id 870BC1B0806E for ; Mon, 23 Nov 2015 13:57:43 +0000 (GMT) Received: from d06av05.portsmouth.uk.ibm.com (d06av05.portsmouth.uk.ibm.com [9.149.37.229]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id tANDvLFj8651010 for ; Mon, 23 Nov 2015 13:57:21 GMT Received: from d06av05.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av05.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id tANDvKWP009109 for ; Mon, 23 Nov 2015 06:57:21 -0700 Subject: Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! To: Mark Salter , Ming Lei 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> <1448234410.8209.3.camel@redhat.com> Cc: linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, "James E. J. Bottomley" , linux-kernel@vger.kernel.org, Christoph Hellwig , brking , tom.leiming@gmail.com, linuxppc-dev@lists.ozlabs.org From: Laurent Dufour Message-ID: <56531B3F.60503@linux.vnet.ibm.com> Date: Mon, 23 Nov 2015 14:57:19 +0100 MIME-Version: 1.0 In-Reply-To: <1448234410.8209.3.camel@redhat.com> Content-Type: text/plain; charset=utf-8 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 23/11/2015 00:20, Mark Salter wrote: > 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. On my side, with the patch applied on top of 4.4-rc1, I can't get the panic anymore.