Re: [PATCH v5 10/10] io_uring: add support for IORING_OP_MKNODAT

[Dmitry Kadashev <dkadashev@gmail.com>]

On Tue, Jun 22, 2021 at 6:52 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>
> On 6/3/21 6:18 AM, Dmitry Kadashev wrote:
> > IORING_OP_MKNODAT behaves like mknodat(2) and takes the same flags and
> > arguments.
> >
> > Suggested-by: Christian Brauner <christian.brauner@ubuntu.com>
> > Link: https://lore.kernel.org/io-uring/20210514145259.wtl4xcsp52woi6ab@wittgenstein/
> > Signed-off-by: Dmitry Kadashev <dkadashev@gmail.com>
> > ---
> >  fs/internal.h                 |  2 ++
> >  fs/io_uring.c                 | 56 +++++++++++++++++++++++++++++++++++
> >  fs/namei.c                    |  2 +-
> >  include/uapi/linux/io_uring.h |  2 ++
> >  4 files changed, 61 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/internal.h b/fs/internal.h
> > index 15a7d210cc67..c6fb9974006f 100644
>
> [...]
>
> >  static bool io_disarm_next(struct io_kiocb *req);
> > @@ -3687,6 +3697,44 @@ static int io_linkat(struct io_kiocb *req, int issue_flags)
> >       io_req_complete(req, ret);
> >       return 0;
> >  }
> > +static int io_mknodat_prep(struct io_kiocb *req,
> > +                         const struct io_uring_sqe *sqe)
> > +{
> > +     struct io_mknod *mkn = &req->mknod;
> > +     const char __user *fname;
> > +
> > +     if (unlikely(req->flags & REQ_F_FIXED_FILE))
> > +             return -EBADF;
>
> IOPOLL won't support it, and the check is missing.
> Probably for other opcodes as well.
>
> if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
>         return -EINVAL;

This change is based on some other similar opcodes (unlinkat, renameat) that
were added a while ago. Those lack the check as well. I guess I'll just prepare
a patch that adds the checks to all of them. Thanks, Pavel.

Jens, separately it's my understanding that you do not want the MKNODAT opcode
at all, should I drop this from the subsequent series?

-- 
Dmitry Kadashev