From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Priebe - Profihost AG Subject: Re: bcache: for-next unable to handle kernel NULL pointer dereference at 0000000000000019 Date: Wed, 25 Oct 2017 15:26:06 +0200 Message-ID: References: <5cd9d4e9-88b2-c24b-f6ed-dad3f8b21283@profihost.ag> <4f1c616f-2e86-2cd3-162c-4ee7a3a02bf4@coly.li> <08c770ef-eb09-ed55-a7bb-31b1b97a88d9@coly.li> <26bed6fb-d433-bcb7-4428-ed7b771f2def@profihost.ag> <8416a91c-d340-85ed-fef9-41d732e0e2be@coly.li> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Received: from cloud1-vm154.de-nserver.de ([178.250.10.56]:60219 "EHLO cloud1-vm154.de-nserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750952AbdJYN0I (ORCPT ); Wed, 25 Oct 2017 09:26:08 -0400 In-Reply-To: <8416a91c-d340-85ed-fef9-41d732e0e2be@coly.li> Content-Language: de-DE Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: Coly Li , linux-bcache@vger.kernel.org Cc: Michael Lyle Am 23.10.2017 um 16:39 schrieb Coly Li: > On 2017/10/23 下午10:26, Stefan Priebe - Profihost AG wrote: >> Hi, >> Am 23.10.2017 um 16:00 schrieb Coly Li: >>> On 2017/10/23 下午9:16, Stefan Priebe - Profihost AG wrote: >>>> Hi, >>>> >>>> Am 23.10.2017 um 15:05 schrieb Coly Li: >>>>> On 2017/10/23 下午8:59, Stefan Priebe - Profihost AG wrote: >>>>>> Hi Coly, >>>>>> >>>>>> >>>>>> Am 23.10.2017 um 14:56 schrieb Coly Li: >>>>>>> On 2017/10/23 下午7:42, Stefan Priebe - Profihost AG wrote: >>>>>>>> Hello, >>>>>>>> >>>>>>>> i picked all bcache patches from for-next to my 4.4 kernel to test the >>>>>>>> new controller. >>>>>>>> >>>>>>>> After doing so i see random kernel panics with the following trace: >>>>>>> >>>>>>> Hi Stefan, >>>>>>> >>>>>>> Thanks for the report. This is the 3rd report I see recently for NULL >>>>>>> pointer dereference, maybe they are related (or maybe not). Is it a >>>>>>> panic when bcache starts to run, or during heavy workload ? >>>>>> >>>>>> It's during heavy / normal workload. >>>>>> >>>>>>> If I may have chance to trigger similar oops on my server, that will be >>>>>>> much easier. So far I cannot reproduce any oops, neither by rebooting >>>>>>> and assemble bcache device by udev rules, nor compose bcache device and >>>>>>> run it by bash scripts... >>>>>> >>>>>> Do you need the line where this happens? It should be possible to get >>>>>> the line from the IP: [] output? >>>>>> >>>>> This is very helpful. >>>> >>>> May be i'm too stupid but it does not print anything useful: >>>> >>>> # addr2line -f -e >>>> /usr/lib/debug/lib/modules/4.4.92+534-ph/kernel/drivers/md/bcache/bcache.ko >>>> ffffffffc04ef62e closure_sub >>>> ?? >>>> ??:0 >>>> bch_inc_gen >>>> ??:? >>>> >>>>> Is it possible to get a kdump crash for the kernel >>>>> oops, that will be much more informative :-) >>>> >>>> no idea how to archieve this for a remote Server. >>> >>> Hi Stefan, >>> >>> In code path of closure_wake_up(), I remember there are two patches in >>> last run, >>> - commit a5f3d8a5eaaf ("bcache: use llist_for_each_entry_safe() in >>> __closure_wake_up()") >>> - commit 09b3efec81de ("bcache: Don't reinvent the wheel but use >>> existing llist API") >>> >>> Can you check whether you have all of these patches ? Or can we try to >>> revoke these two patches and see whether oops still happens. >> >> It seems i'm missing a5f3d8a5eaaf but i have 09b3efec81de. >> >> I missed it because >> git log ..linux-block/for-next -- drivers/md/bcache/ >> >> does not show it. It seems linux-block/for-next does not contain it? >> Which branch should i use? >> >> Only those contain the mentioned commit: >> remotes/linux-block/for-linus >> remotes/linux-block/master >> remotes/linux-block/wbt-odirect >> > > Hi Stefan, > > These 2 patches are in 4.14 mainline kernel already. This is my fault to > make commit 09b3efec81de buggy, and fix it in commit a5f3d8a5eaaf. > > Could you please try again with the fixing patch ? > > (And I guess maybe other 2 reports may also miss this fix). OK indeed it seems it fixed it. Sorry about that. Greets, Stefan > Thanks. > > Coly Li >