Re: [RFC PATCH v2 1/3] mm/gup: fix gup_fast with dynamic page table folding

From: Jason Gunthorpe
Date: Thu Sep 10 2020 - 13:21:07 EST

On Thu, Sep 10, 2020 at 07:07:57PM +0200, Gerald Schaefer wrote:

> I might have lost track a bit. Are we still talking about possible
> functional impacts of either our current pagetable walking with s390
> (apart from gup_fast), or the proposed generic change (for s390, or
> others?)?

I'm looking for an more understandable explanation what is wrong with
the S390 implementation.

If the page operations require the invariant I described then it is
quite easy to explain the problem and understand the solution.