Re: [PATCH v17 00/10] mm: introduce memfd_secret system call to create "secret" memory areas

Mike Rapoport
2021-02-08T21:14:05Z

On Mon, Feb 08, 2021 at 10:27:18AM +0100, David Hildenbrand wrote:
> On 08.02.21 09:49, Mike Rapoport wrote:
>
> Some questions (and request to document the answers) as we now allow to have
> unmovable allocations all over the place and I don't see a single comment
> regarding that in the cover letter:
>
> 1. How will the issue of plenty of unmovable allocations for user space be
> tackled in the future?
>
> 2. How has this issue been documented? E.g., interaction with ZONE_MOVABLE
> and CMA, alloc_conig_range()/alloc_contig_pages?.

Secretmem sets the mappings gfp mask to GFP_HIGHUSER, so it does not
allocate movable pages at the first place.

> 3. How are the plans to support migration in the future and which interface
> changes will be required? (Michal mentioned some good points to make this
> configurable via the interface, we should plan ahead and document)

The only interface change required is an addition of bit value for syscall
flags, I really think it can be documented with the addition of migration
or any other feature for that sake.

--
Sincerely yours,
Mike.