Re: [PATCH v2 1/1] userfaultfd/sysctl: add vm.unprivileged_userfaultfd

[Xiaoming Ni]

On 2020/5/27 22:21, Peter Xu wrote:
> On Wed, May 27, 2020 at 02:54:13PM +0800, Xiaoming Ni wrote:
> > On Tue, Mar 19, 2019 at 11:07:22AM +0800, Peter Xu wrote:
> > > Add a global sysctl knob "vm.unprivileged_userfaultfd" to control
> > > whether userfaultfd is allowed by unprivileged users.  When this is
> > > set to zero, only privileged users (root user, or users with the
> > > CAP_SYS_PTRACE capability) will be able to use the userfaultfd
> > > syscalls.
> >
> > Hello
>
> Hi, Xiaoming,
>
> > I am a bit confused about this patch, can you help to answer it.
> >
> > Why the sysctl interface of fs/userfaultfd.c belongs to vm_table instead of
> > fs_table ?
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=cefdca0a86be517bc390fc4541e3674b8e7803b0
>
> Because I think it makes more sense to put the new key into where it suites
> better, irrelevant to which directory the variable is declared.  To me,
> unprivileged_userfaultfd is definitely more suitable for vm rather than fs,
> because userfaultfd is really about memory management rather than file system.
>
> Thanks,

Thank you for your answer
Since userfaultfd and vm are more closely related, will there be 
consideration to move fs/userfaultfd.c to the mm directory in the future?

Thanks
Xiaoming Ni