[PATCH 3/3] /dev/null: add IORING_OP_URING_CMD support

[Paul Moore]

On Mon, Aug 22, 2022 at 7:13 PM Jens Axboe <axboe at kernel.dk> wrote:
> On 8/22/22 5:09 PM, Paul Moore wrote:
> > On Mon, Aug 22, 2022 at 6:36 PM Jens Axboe <axboe at kernel.dk> wrote:
> >> On 8/22/22 3:21 PM, Paul Moore wrote:
> >>> This patch adds support for the io_uring command pass through, aka
> >>> IORING_OP_URING_CMD, to the /dev/null driver.  As with all of the
> >>> /dev/null functionality, the implementation is just a simple sink
> >>> where commands go to die, but it should be useful for developers who
> >>> need a simple IORING_OP_URING_CMD test device that doesn't require
> >>> any special hardware.
> >>>
> >>> Cc: Arnd Bergmann <arnd at arndb.de>
> >>> Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> >>> Signed-off-by: Paul Moore <paul at paul-moore.com>
> >>> ---
> >>>  drivers/char/mem.c |    6 ++++++
> >>>  1 file changed, 6 insertions(+)
> >>>
> >>> diff --git a/drivers/char/mem.c b/drivers/char/mem.c
> >>> index 84ca98ed1dad..32a932a065a6 100644
> >>> --- a/drivers/char/mem.c
> >>> +++ b/drivers/char/mem.c
> >>> @@ -480,6 +480,11 @@ static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out,
> >>>       return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
> >>>  }
> >>>
> >>> +static int uring_cmd_null(struct io_uring_cmd *ioucmd, unsigned int issue_flags)
> >>> +{
> >>> +     return 0;
> >>> +}
> >>
> >> This would be better as:
> >>
> >>         return IOU_OK;
> >>
> >> using the proper return values for the uring_cmd hook.
> >
> > The only problem I see with that is that IOU_OK is defined under
> > io_uring/io_uring.h and not include/linux/io_uring.h so the #include
> > macro is kinda ugly:
> >
> >   #include "../../io_uring/io_uring.h"
> >
> > I'm not sure I want to submit that upstream looking like that.  Are
> > you okay with leaving the return code as 0 for now and changing it at
> > a later date?  I'm trying to keep this patchset relatively small since
> > we are in the -rcX stage, but if you're okay with a simple cut-n-paste
> > of the enum to linux/io_uring.h I can do that.
>
> Ugh yes, that should move into the general domain. Yeah I'm fine with it
> as it is, we can fix that up (and them nvme as well) at a later point.

Okay, sounds good, I'll leave it as-is.  Is it okay to still add your ACK?

-- 
paul-moore.com