Re: [RFC PATCH v2 1/4] net: wire up support for file_operations->uring_cmd()

[Stefan Metzmacher <metze@samba.org>]

Am 19.06.23 um 13:20 schrieb Breno Leitao:
> On Wed, Jun 14, 2023 at 08:15:10AM -0700, David Ahern wrote:
>> On 6/14/23 5:07 AM, Breno Leitao wrote:
>> io_uring is just another in-kernel user of sockets. There is no reason
>> for io_uring references to be in core net code. It should be using
>> exposed in-kernel APIs and doing any translation of its op codes in
>> io_uring/  code.
> 
> Thanks for the feedback. If we want to keep the network subsystem
> untouched, then I we can do it using an approach similar to the
> following. Is this a better approach moving forward?

I'd like to keep it passed to socket layer, so that sockets could
implement some extra features in an async fashion.

What about having the function you posted below (and in v3)
as a default implementation if proto_ops->uring_cmd is NULL?

metze

> --
> 
> From: Breno Leitao <leitao@debian.org>
> Date: Mon, 19 Jun 2023 03:37:40 -0700
> Subject: [RFC PATCH v2] io_uring: add initial io_uring_cmd support for sockets
> 
> Enable io_uring command operations on sockets. Create two
> SOCKET_URING_OP commands that will operate on sockets.
> 
> For that, use the file_operations->uring_cmd callback, and map it to a
> uring socket callback, which handles the SOCKET_URING_OP accordingly.
> 
> Signed-off-by: Breno Leitao <leitao@debian.org>
> ---
>   include/linux/io_uring.h      |  6 ++++++
>   include/uapi/linux/io_uring.h |  8 ++++++++
>   io_uring/uring_cmd.c          | 27 +++++++++++++++++++++++++++
>   net/socket.c                  |  2 ++
>   4 files changed, 43 insertions(+)
> 
> diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
> index 7fe31b2cd02f..d1b20e2a9fb0 100644
> --- a/include/linux/io_uring.h
> +++ b/include/linux/io_uring.h
> @@ -71,6 +71,7 @@ static inline void io_uring_free(struct task_struct *tsk)
>   	if (tsk->io_uring)
>   		__io_uring_free(tsk);
>   }
> +int uring_sock_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags);
>   #else
>   static inline int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
>   			      struct iov_iter *iter, void *ioucmd)
> @@ -102,6 +103,11 @@ static inline const char *io_uring_get_opcode(u8 opcode)
>   {
>   	return "";
>   }
> +static inline int uring_sock_cmd(struct io_uring_cmd *cmd,
> +				 unsigned int issue_flags)
> +{
> +	return -EOPNOTSUPP;
> +}
>   #endif
>   
>   #endif
> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> index 0716cb17e436..d93a5ee7d984 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
> @@ -703,6 +703,14 @@ struct io_uring_recvmsg_out {
>   	__u32 flags;
>   };
>   
> +/*
> + * Argument for IORING_OP_URING_CMD when file is a socket
> + */
> +enum {
> +	SOCKET_URING_OP_SIOCINQ         = 0,
> +	SOCKET_URING_OP_SIOCOUTQ,
> +};
> +
>   #ifdef __cplusplus
>   }
>   #endif
> diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
> index 5e32db48696d..dcbe6493b03f 100644
> --- a/io_uring/uring_cmd.c
> +++ b/io_uring/uring_cmd.c
> @@ -7,6 +7,7 @@
>   #include <linux/nospec.h>
>   
>   #include <uapi/linux/io_uring.h>
> +#include <uapi/asm-generic/ioctls.h>
>   
>   #include "io_uring.h"
>   #include "rsrc.h"
> @@ -156,3 +157,29 @@ int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
>   	return io_import_fixed(rw, iter, req->imu, ubuf, len);
>   }
>   EXPORT_SYMBOL_GPL(io_uring_cmd_import_fixed);
> +
> +int uring_sock_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
> +{
> +	struct socket *sock = cmd->file->private_data;
> +	struct sock *sk = sock->sk;
> +	int ret, arg = 0;
> +
> +	if (!sk->sk_prot || !sk->sk_prot->ioctl)
> +		return -EOPNOTSUPP;
> +
> +	switch (cmd->sqe->cmd_op) {
> +	case SOCKET_URING_OP_SIOCINQ:
> +		ret = sk->sk_prot->ioctl(sk, SIOCINQ, &arg);
> +		if (ret)
> +			return ret;
> +		return arg;
> +	case SOCKET_URING_OP_SIOCOUTQ:
> +		ret = sk->sk_prot->ioctl(sk, SIOCOUTQ, &arg);
> +		if (ret)
> +			return ret;
> +		return arg;
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}
> +EXPORT_SYMBOL_GPL(uring_sock_cmd);
> diff --git a/net/socket.c b/net/socket.c
> index b778fc03c6e0..db11e94d2259 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -88,6 +88,7 @@
>   #include <linux/xattr.h>
>   #include <linux/nospec.h>
>   #include <linux/indirect_call_wrapper.h>
> +#include <linux/io_uring.h>
>   
>   #include <linux/uaccess.h>
>   #include <asm/unistd.h>
> @@ -159,6 +160,7 @@ static const struct file_operations socket_file_ops = {
>   #ifdef CONFIG_COMPAT
>   	.compat_ioctl = compat_sock_ioctl,
>   #endif
> +	.uring_cmd =    uring_sock_cmd,
>   	.mmap =		sock_mmap,
>   	.release =	sock_close,
>   	.fasync =	sock_fasync,