Re: [PATCH] mm: swapfile: avoid split_swap_cluster() NULL pointer dereference

[Huang, Ying]

Rafael Aquini <aquini@xxxxxxxxxx> writes:
>> Or, can you help to run the test with a debug kernel based on upstream
>> kernel.  I can provide some debug patch.
>> 
>
> Sure, I can set your patches to run with the test cases we have that tend to 
> reproduce the issue with some degree of success.

Thanks!

I found a race condition.  During THP splitting, "head" may be unlocked
before calling split_swap_cluster(), because head != page during
deferred splitting.  So we should call split_swap_cluster() before
unlocking.  The debug patch to do that is as below.  Can you help to
test it?

Best Regards,
Huang, Ying

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