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    SubjectRe: [PATCH v17 07/10] mm: introduce memfd_secret system call to create "secret" memory areas
    On Sun 14-02-21 11:21:02, James Bottomley wrote:
    > On Sun, 2021-02-14 at 10:58 +0100, David Hildenbrand wrote:
    > [...]
    > > > And here we come to the question "what are the differences that
    > > > justify a new system call?" and the answer to this is very
    > > > subjective. And as such we can continue bikeshedding forever.
    > >
    > > I think this fits into the existing memfd_create() syscall just fine,
    > > and I heard no compelling argument why it shouldn‘t. That‘s all I can
    > > say.
    >
    > OK, so let's review history. In the first two incarnations of the
    > patch, it was an extension of memfd_create(). The specific objection
    > by Kirill Shutemov was that it doesn't share any code in common with
    > memfd and so should be a separate system call:
    >
    > https://lore.kernel.org/linux-api/20200713105812.dnwtdhsuyj3xbh4f@box/

    Thanks for the pointer. But this argument hasn't been challenged at all.
    It hasn't been brought up that the overlap would be considerable higher
    by the hugetlb/sealing support. And so far nobody has claimed those
    combinations as unviable.

    > The other objection raised offlist is that if we do use memfd_create,
    > then we have to add all the secret memory flags as an additional ioctl,
    > whereas they can be specified on open if we do a separate system call.
    > The container people violently objected to the ioctl because it can't
    > be properly analysed by seccomp and much preferred the syscall version.
    >
    > Since we're dumping the uncached variant, the ioctl problem disappears
    > but so does the possibility of ever adding it back if we take on the
    > container peoples' objection. This argues for a separate syscall
    > because we can add additional features and extend the API with flags
    > without causing anti-ioctl riots.

    I am sorry but I do not understand this argument. What kind of flags are
    we talking about and why would that be a problem with memfd_create
    interface? Could you be more specific please?
    --
    Michal Hocko
    SUSE Labs

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