Re: [PATCH v2 2/6] userfaultfd: add /dev/userfaultfd for fine grained access control

[Axel Rasmussen]

You're right, [1] says _IO is appropriate for ioctls which only take
an integer argument. I'll send a v3 with this fix, although I might
wait a bit for any other review comments before doing so. Thanks for
taking a look!

https://www.kernel.org/doc/html/latest/driver-api/ioctl.html

On Mon, Apr 25, 2022 at 1:32 PM Dmitry V. Levin <ldv@xxxxxxxxxxxx> wrote:
>
> On Fri, Apr 22, 2022 at 02:29:41PM -0700, Axel Rasmussen wrote:
> [...]
> > --- a/include/uapi/linux/userfaultfd.h
> > +++ b/include/uapi/linux/userfaultfd.h
> > @@ -12,6 +12,10 @@
> >
> >  #include <linux/types.h>
> >
> > +/* ioctls for /dev/userfaultfd */
> > +#define USERFAULTFD_IOC 0xAA
> > +#define USERFAULTFD_IOC_NEW _IOWR(USERFAULTFD_IOC, 0x00, int)
>
> Why this new ioctl is defined using _IOWR()?  Since it neither reads from
> user memory nor writes into user memory, it should rather be defined using
> _IO(), shouldn't it?
>
>
> --
> ldv