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Date:   Mon, 8 Feb 2021 23:13:26 +0200
From:   Mike Rapoport <rppt@kernel.org>
To:     David Hildenbrand <david@redhat.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Andy Lutomirski <luto@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Christopher Lameter <cl@linux.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Elena Reshetova <elena.reshetova@intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        James Bottomley <jejb@linux.ibm.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Matthew Wilcox <willy@infradead.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Michal Hocko <mhocko@suse.com>,
        Mike Rapoport <rppt@linux.ibm.com>,
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Subject: Re: [PATCH v17 00/10] mm: introduce memfd_secret system call to
 create "secret" memory areas
Message-ID: <20210208211326.GV242749@kernel.org>
References: <20210208084920.2884-1-rppt@kernel.org>
 <4996348d-5710-d77d-bb14-d84e370b4a5c@redhat.com>
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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.