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

Joao Martins
2021-05-06T10:24:45Z

On 5/6/21 12:14 AM, Dan Williams wrote:
> 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.

/me nods

> 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."
>
Let me use this one instead, definitely better than my strange english :)