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

[Paul Moore]

On Mon, Aug 22, 2022 at 7:25 PM Jens Axboe <axboe at kernel.dk> wrote:
>
> On 8/22/22 5:19 PM, Paul Moore wrote:
> > 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?
>
> Yep, all things considered, for 6.0 I think that's the way to go.

Great, thanks.

-- 
paul-moore.com