Re: [PATCH v4] userfaultfd/shmem: fix MCOPY_ATOMIC_CONTINUE behavior

[Hugh Dickins <hughd@google.com>]

On Wed, 7 Apr 2021, Axel Rasmussen wrote:
> Agreed about taking one direction or the other further.
> 
> I get the sense that Peter prefers the mcopy_atomic_install_ptes()
> version, and would thus prefer to just expose that and let
> shmem_mcopy_atomic_pte() use it.
> 
> But, I get the sense that you (Hugh) slightly prefer the other way -
> just letting shmem_mcopy_atomic_pte() deal with both the VM_SHARED and
> !VM_SHARED cases.

No, either direction seems plausible to me: start from whichever
end you prefer.

> 
> I was planning to write "I prefer option X because (reasons), and
> objections?" but I'm realizing that it isn't really clear to me which
> route would end up being cleaner. I think I have to just pick one,
> write it out, and see where I end up. If it ends up gross, I don't
> mind backtracking and taking the other route. :) To that end, I'll
> proceed by having shmem_mcopy_atomic_pte() call the new
> mcopy_atomic_install_ptes() helper, and see how it looks (unless there
> are objections).

I am pleased to read that: it's exactly how I would approach it -
so it must be right :-)

Hugh