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

From: John Hubbard
Date: Mon Jan 06 2020 - 20:29:19 EST

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...



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.

John Hubbard