Re: [PATCH v1 05/11] mm/sparse-vmemmap: add a pgmap argument to section activation

Dan Williams
2021-05-05T23:14:35Z

On Wed, May 5, 2021 at 3:38 PM Joao Martins <joao.m.martins@oracle.com> wrote:
>
>
>
> On 5/5/21 11:34 PM, Dan Williams wrote:
> > On Thu, Mar 25, 2021 at 4:10 PM Joao Martins <joao.m.martins@oracle.com> wrote:
> >>
> >> @altmap is stored in a dev_pagemap, but it will be repurposed for
> >> hotplug memory for storing the memmap in the hotplugged memory[*] and
> >> reusing the altmap infrastructure to that end. This is to say that
> >> altmap can't be replaced with a @pgmap as it is going to cover more than
> >> dev_pagemap backend altmaps.
> >
> > I was going to say, just pass the pgmap and lookup the altmap from
> > pgmap, but Oscar added a use case for altmap independent of pgmap. So
> > you might refresh this commit message to clarify why passing pgmap by
> > itself is not sufficient.
> >
> Isn't that what I am doing above with that exact paragraph? I even
> reference his series at the end of commit description :) in [*]

Oh, sorry, it didn't hit me explicitly that you were talking about
Oscar's work I thought you were referring to your own changes in this
set. I see it now... at a minimum the tense needs updating since
Oscar's changes are in the past not the future anymore. If it helps,
the following reads more direct to me: "In support of using compound
pages for devmap mappings, plumb the pgmap down to the
vmemmap_populate* implementation. Note that while altmap is
retrievable from pgmap the memory hotplug codes passes altmap without
pgmap, so both need to be independently plumbed."