Re: [PATCH v17 00/10] mm: introduce memfd_secret system call to create "secret" memory areas
Am 08.02.2021 um 22:13 schrieb Mike Rapoport
<rppt(a)kernel.org>:
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.
That is not the point. Secretmem cannot go on CMA / ZONE_MOVABLE memory and behaves like
long-term pinnings in that sense. This is a real issue when using a lot of sectremem.
Please have a look at what Pavel documents regarding long term pinnings and ZONE_MOVABLE
in his patches currently on the list.