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Subject: Re: [PATCH v11 00/25] mm/gup: track dma-pinned pages: FOLL_PIN
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From:   John Hubbard <jhubbard@nvidia.com>
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On 1/6/20 1:01 AM, Jan Kara wrote:
...
>> Also, looking ahead:
>>
>> a) if the problem disappears with the latest above test, then we likely have
>>     a huge page refcount overflow, and there are a couple of different ways to
>>     fix it.
>>
>> b) if it still reproduces with the above, then it's some other random mistake,
>>     and in that case I'd be inclined to do a sort of guided (or classic, unguided)
>>     git bisect of the series. Because it could be any of several patches.
>>
>>     If that's too much trouble, then I'd have to fall back to submitting a few
>>     patches at a time and working my way up to the tracking patch...
> 
> It could also be that an ordinary page reference is dropped with 'unpin'
> thus underflowing the page refcount...
> 
> 								Honza
> 

Yes.

And, I think I'm about out of time for this release cycle, so I'm probably going to
submit the prerequisite patches (patches 1-10, or more boldly, 1-22), for candidates
for 5.6.


thanks,
-- 
John Hubbard
NVIDIA