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

[Jens Axboe]

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.

-- 
Jens Axboe