From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kent Overstreet Subject: Re: md-raid5 with bcache member devices => kernel panic Date: Thu, 5 Dec 2013 15:15:47 -0800 Message-ID: <20131205231547.GB4054@kmo> References: <20131205212913.GE1848@teapot> <20131205225234.GA4054@kmo> <20131205230813.GF1848@teapot> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-pb0-f49.google.com ([209.85.160.49]:54551 "EHLO mail-pb0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755267Ab3LEXPv (ORCPT ); Thu, 5 Dec 2013 18:15:51 -0500 Received: by mail-pb0-f49.google.com with SMTP id jt11so26815023pbb.22 for ; Thu, 05 Dec 2013 15:15:50 -0800 (PST) Content-Disposition: inline In-Reply-To: <20131205230813.GF1848@teapot> Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: Matthias Ferdinand Cc: nks@daterainc.com, linux-bcache@vger.kernel.org On Fri, Dec 06, 2013 at 12:08:13AM +0100, Matthias Ferdinand wrote: > On Thu, Dec 05, 2013 at 02:52:34PM -0800, Kent Overstreet wrote: > > On Thu, Dec 05, 2013 at 10:29:13PM +0100, Matthias Ferdinand wrote: > > Erk. I thought I was done with these bugs. Nick, do you think you could try and > > track this down? > > > > Looking at this: > > http://dl.mfedv.net/md5raid_on_bcache_panic/mdraid5_on_bcache_panic_3.12.2.txt > > > > that's a null pointer deref; if Matthias could get the exact line number it > I have no idea how to do that - can you help me out on that? > > > Matthias - I'm running bcache on top of a raid6 at home and I've never seen > I only get panics when I use md-raid on top of bcaches: > > LVM > | > md-raid5 > / | \ > bcache0 bcache1 bcache2 > | | | > sdb6 sdc6 sdd6 > > (probably an unusual setup; just playing around...) Yeah, that is unusual. Very odd though, that setup I would definitely expect to work. You mentioned it's faster with bcache higher in the stack - do you have any issues with your preferred setup? If the bug isn't actually affecting real/preferred use cases then I'll be a lot less concerned about it - I'm reworking how all this crap works in mainline, maybe by 3.14 generic_make_request() will be accepting arbitrary size bios and the code that's probably buggy here will be gone.