Re: [PATCH v11 00/25] mm/gup: track dma-pinned pages: FOLL_PIN

[John Hubbard]

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