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

On Thu, Jun 29, 2017 at 06:47:50PM +1000, Balbir Singh wrote:

On Thu, Jun 29, 2017 at 1:41 PM, Eryu Guan [off-list ref] wrote:

quoted

On Thu, Jun 29, 2017 at 03:16:10AM +1000, Balbir Singh wrote:

quoted

On Wed, Jun 28, 2017 at 6:32 PM, Eryu Guan [off-list ref] wrote:

<snip>

quoted

quoted

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@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@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