Re: [PATCH] Linux: Add memfd_create system call wrapper

[Florian Weimer <fweimer at redhat dot com>]

On 11/17/2017 11:41 PM, Joseph Myers wrote:
> On Fri, 17 Nov 2017, Florian Weimer wrote:
>
> > On 11/16/2017 11:34 AM, Adhemerval Zanella wrote:
> > > Linux 4.14 (749df87bd7be) added a new flag MFD_HUGETLB. I think ww should
> > > add
> > > and document it.
> >
> > We currently do not document MAP_HUGETLB, which is closely related and not
> > really simple to describe.  The manual page and kernel documentation do not
> > cover it in detail, either.  The page size selection in particular is missing,
> > and I would have to research how an application can discover supported
> > hugepage sizes.
> >
> > In short, this is not exactly a trivial request, and I would kindly ask you to
> > reconsider.
>
> Maybe say the new flag should at least be added to the header (unless
> automatically visible via an include of a <linux/*.h> UAPI header), absent
> a reason not to do so, but given the difficulties of doing so we might for
> now not document it (generically, for new constants from new Linux kernel
> releases, as opposed to new functions, that's been the practice for a long
> time).

Would it be okay to pretend that the hugepage size selection mechanism 
doesn't exist?

We haven't added that yet for SHM_HUGETLB, either.

Thanks,
Florian