Re: [PATCH V4 1/2] io_uring: retain top 8bits of uring_cmd flags for kernel internal use

[Gabriel Krisman Bertazi <krisman@suse.de>]

Ming Lei <ming.lei@redhat.com> writes:

> Retain top 8bits of uring_cmd flags for kernel internal use, so that we
> can move IORING_URING_CMD_POLLED out of uapi header.

Feel free to add:

Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de>

>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  include/linux/io_uring.h      | 3 +++
>  include/uapi/linux/io_uring.h | 5 ++---
>  io_uring/io_uring.c           | 3 +++
>  io_uring/uring_cmd.c          | 2 +-
>  4 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
> index 106cdc55ff3b..ae08d6f66e62 100644
> --- a/include/linux/io_uring.h
> +++ b/include/linux/io_uring.h
> @@ -22,6 +22,9 @@ enum io_uring_cmd_flags {
>  	IO_URING_F_IOPOLL		= (1 << 10),
>  };
>  
> +/* only top 8 bits of sqe->uring_cmd_flags for kernel internal use */
> +#define IORING_URING_CMD_POLLED		(1U << 31)
> +
>  struct io_uring_cmd {
>  	struct file	*file;
>  	const struct io_uring_sqe *sqe;
> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> index 8e61f8b7c2ce..de77ad08b123 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
> @@ -246,13 +246,12 @@ enum io_uring_op {
>  };
>  
>  /*
> - * sqe->uring_cmd_flags
> + * sqe->uring_cmd_flags		top 8bits aren't available for userspace
>   * IORING_URING_CMD_FIXED	use registered buffer; pass this flag
>   *				along with setting sqe->buf_index.
> - * IORING_URING_CMD_POLLED	driver use only
>   */
>  #define IORING_URING_CMD_FIXED	(1U << 0)
> -#define IORING_URING_CMD_POLLED	(1U << 31)
> +#define IORING_URING_CMD_MASK	IORING_URING_CMD_FIXED
>  
>  
>  /*
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index 783ed0fff71b..9aedb7202403 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -4666,6 +4666,9 @@ static int __init io_uring_init(void)
>  
>  	BUILD_BUG_ON(sizeof(atomic_t) != sizeof(u32));
>  
> +	/* top 8bits are for internal use */
> +	BUILD_BUG_ON((IORING_URING_CMD_MASK & 0xff000000) != 0);
> +
>  	io_uring_optable_init();
>  
>  	/*
> diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
> index 537795fddc87..a0b0ec5473bf 100644
> --- a/io_uring/uring_cmd.c
> +++ b/io_uring/uring_cmd.c
> @@ -91,7 +91,7 @@ int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>  		return -EINVAL;
>  
>  	ioucmd->flags = READ_ONCE(sqe->uring_cmd_flags);
> -	if (ioucmd->flags & ~IORING_URING_CMD_FIXED)
> +	if (ioucmd->flags & ~IORING_URING_CMD_MASK)
>  		return -EINVAL;
>  
>  	if (ioucmd->flags & IORING_URING_CMD_FIXED) {

-- 
Gabriel Krisman Bertazi