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

[Jens Axboe]

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.

-- 
Jens Axboe