Re: [PATCH v2 2/3] userfaultfd: UFFDIO_REMAP uABI

Lokesh Gidra
2023-10-03T23:39:45Z

On Tue, Oct 3, 2023 at 11:26 PM Suren Baghdasaryan <surenb@google.com> wrote:
>
> On Tue, Oct 3, 2023 at 2:21 PM Peter Xu <peterx@redhat.com> wrote:
> >
> > On Tue, Oct 03, 2023 at 11:08:07PM +0200, David Hildenbrand wrote:
> > > Sorry I have to ask: has this ever been discussed on the list? I don't see
> > > any pointers. If not, then probably the number of people that know about the
> > > history can be counted with my two hands and that shouldn't be the basis for
> > > making decisions.
> >
> > For example:
> >
> > https://lore.kernel.org/all/1425575884-2574-21-git-send-email-aarcange@redhat.com/
>
> There was another submission in 2019:
> https://lore.kernel.org/all/cover.1547251023.git.blake.caldwell@colorado.edu/
>
> Though both times it did not generate much discussion. I don't have a
> strong preference though MOVE sounds more generic to me TBH (it
> specifies the operation rather than REMAP which hints on how that
> operation is carried out). But again, I'm fine either way.

That's a good point. IMHO, if in future we want to have the fallback
implemented, then MOVE would be a more appropriate name than REMAP.

> As for UFFDIO_MOVE_ZERO_COPY_ONLY vs UFFDIO_MOVE_MODE_ALLOW_COPY, I
> find it weird that the default (the most efficient/desired) mode of
> operation needs a flag. I would prefer to have no flag initially and
> add UFFDIO_MOVE_MODE_ALLOW_COPY or whatever name is more appropriate
> when/if we ever need it. Makes sense?

Agreed!
>
> >
> > --
> > Peter Xu
> >
> > --
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> >