Re: bcache: for-next unable to handle kernel NULL pointer dereference at 0000000000000019

Stefan Priebe - Profihost AG
2017-10-23T13:16:35Z

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: [<ffffffffc04ef62e>] 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.

Greets,
Stefan