Re: [PATCH] io_uring: Add io_uring command support for sockets

[Breno Leitao <leitao@debian.org>]

On Thu, Jun 22, 2023 at 07:03:04PM +0200, Greg Kroah-Hartman wrote:
> On Thu, Jun 22, 2023 at 09:38:15AM -0700, Breno Leitao wrote:
> > On Thu, Jun 22, 2023 at 06:10:00PM +0200, Greg Kroah-Hartman wrote:
> > > On Thu, Jun 22, 2023 at 08:02:37AM -0700, Breno Leitao wrote:
> > > > On Thu, Jun 22, 2023 at 07:20:48AM +0200, Greg Kroah-Hartman wrote:
> > > > > On Wed, Jun 21, 2023 at 04:21:26PM -0700, Breno Leitao wrote:
> > > > > > --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
> > > > > > +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
> > > > > > @@ -361,6 +361,7 @@ Code  Seq#    Include File                                           Comments
> > > > > >  0xCB  00-1F                                                          CBM serial IEC bus in development:
> > > > > >                                                                       <mailto:michael.klein@puffin.lb.shuttle.de>
> > > > > >  0xCC  00-0F  drivers/misc/ibmvmc.h                                   pseries VMC driver
> > > > > > +0xCC  A0-BF  uapi/linux/io_uring.h                                   io_uring cmd subsystem
> > > > > 
> > > > > This change is nice, but not totally related to this specific one,
> > > > > shouldn't it be separate?
> > > > 
> > > > This is related to this patch, since I am using it below, in the
> > > > following part:
> > > > 
> > > > 	+#define SOCKET_URING_OP_SIOCINQ _IOR(0xcc, 0xa0, int)
> > > > 	+#define SOCKET_URING_OP_SIOCOUTQ _IOR(0xcc, 0xa1, int)
> > > > 
> > > > Should I have a different patch, even if they are related?
> > > 
> > > Yes, as you are not using the 0xa2-0xbf range that you just carved out
> > > here, right?  Where did those numbers come from?
> > 
> > Correct. For now we are just using 0xa0 and 0xa1, and eventually we
> > might need more ioctls numbers.
> > 
> > I got these numbers finding a unused block and having some room for
> > expansion, as suggested by Documentation/userspace-api/ioctl/ioctl-number.rst,
> > that says:
> > 
> > 	If you are writing a driver for a new device and need a letter, pick an
> > 	unused block with enough room for expansion: 32 to 256 ioctl commands.
> 
> So is this the first io_uring ioctl?  If so, why is this an ioctl and
> not just a "normal" io_uring call?

This is a way to pass a generic command to file. This is not a ioctl per
se (not called through ioctl). I am leveraging the ioctl to embedded the
"direction" and "size" information in the command itself.

I can defintely do something as the following, if it is a better
implementation:

	#define SOCKET_URING_OP_SIOCINQ 0
	#define SOCKET_URING_OP_SIOCOUTQ 1