[v4.12-rc1 regression] mount ext4 fs results in kernel crash on PPC64le host

[Eryu Guan]

On Thu, Jun 29, 2017 at 06:47:50PM +1000, Balbir Singh wrote:
> On Thu, Jun 29, 2017 at 1:41 PM, Eryu Guan <eguan at redhat.com> wrote:
> > On Thu, Jun 29, 2017 at 03:16:10AM +1000, Balbir Singh wrote:
> >> On Wed, Jun 28, 2017 at 6:32 PM, Eryu Guan <eguan at redhat.com> wrote:
> <snip>
> >> Thanks for the excellent bug report, I am a little lost on the stack
> >> trace, it shows a bad page access that we think is triggered by the
> >> mmap changes? The patch changed the return type to integrate the call
> >> into trace-cmd. Could you point me to the tests that can help
> >> reproduce the crash. Could you also suggest how long to try the test
> >> cases for?
> >
> > Sorry, I should have provided it in the first place. It's as simple as
> > mounting an ext4 filesystem on my test ppc64le host, i.e.
> >
> > mkdir -p /mnt/ext4
> > mkfs -t ext4 -F /dev/sda5
> > mount /dev/sda5 /mnt/ext4
> >
> 
> I tried this test a few times with the kernel and could not reproduce it.

Yes, it's not reproduced on every host, I'm not sure what makes my test
host so unique yet.

> Could you please share the config and compiler details, I'll retry with -rc7.

[root at ibm-p8-03-lp6 ~]# gcc --version
gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-16)
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is
NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE.

[root at ibm-p8-03-lp6 ~]# rpm -q gcc
gcc-4.8.5-16.el7.ppc64le

I attached kernel config file.

> 
> In the meanwhile, does enabling kmemleak, DEBUG_PAGE_ALLOC,
> slub/slab debug, list corruption, etc catch anything at the time of the
> corruption?

OK, I'll retry with a debug kernel and report back.

Thanks,
Eryu
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