Re: A crash on ARM64 in move_freepages_block due to uninitialized pages in reserved memory

On Thu, 23 Aug 2018, Pasha Tatashin wrote:

On 8/23/18 7:23 AM, Michal Hocko wrote:

quoted

On Thu 23-08-18 07:16:34, Mikulas Patocka wrote:

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On Thu, 23 Aug 2018, Michal Hocko wrote:

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On Thu 23-08-18 07:02:37, Mikulas Patocka wrote:
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This crash is not from -ENOENT. It crashes because page->compound_head is 
0xffffffffffffffff (see below).

If I enable CONFIG_DEBUG_VM, I also get VM_BUG.

This smells like the struct page is not initialized properly. How is
this memory range added? I mean is it brought up by the memory hotplug
or during the boot?

I believe it is due to uninitialized struct pages. Mikulas, could you
please provide config file, and also the full console output.

Please make sure that you have:
CONFIG_DEBUG_VM=y
CONFIG_ARCH_HAS_DEBUG_VIRTUAL=y

I wonder what kind of struct page memory layout is used, and also if
deferred struct pages are enabled or not.

I uploaded configs and console logs (for the real hardware and for the 
virtual machine) here: 
http://people.redhat.com/~mpatocka/testcases/arm64-config/

The virtual machine was running the lvm2 testsuite while the crash 
happened.

Have you tried bisecting the problem?

I may try some old kernel in the virtual machine to test if the bug 
happens on it.

Thank you,
Pavel

Mikulas