Re: [PATCH 3/5] io_uring: add support for getdents

[Hao Xu <hao.xu@linux.dev>]

On 7/18/23 21:21, Hao Xu wrote:
> From: Hao Xu <howeyxu@tencent.com>
> 
> This add support for getdents64 to io_uring, acting exactly like the
> syscall: the directory is iterated from it's current's position as
> stored in the file struct, and the file's position is updated exactly as
> if getdents64 had been called.
> 
> For filesystems that support NOWAIT in iterate_shared(), try to use it
> first; if a user already knows the filesystem they use do not support
> nowait they can force async through IOSQE_ASYNC in the sqe flags,
> avoiding the need to bounce back through a useless EAGAIN return.
> 
> Co-developed-by: Dominique Martinet <asmadeus@codewreck.org>
> Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
> Signed-off-by: Hao Xu <howeyxu@tencent.com>
> ---
>   include/uapi/linux/io_uring.h |  7 +++++
>   io_uring/fs.c                 | 55 +++++++++++++++++++++++++++++++++++
>   io_uring/fs.h                 |  3 ++
>   io_uring/opdef.c              |  8 +++++
>   4 files changed, 73 insertions(+)
> 
> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> index 36f9c73082de..b200b2600622 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
> @@ -65,6 +65,7 @@ struct io_uring_sqe {
>   		__u32		xattr_flags;
>   		__u32		msg_ring_flags;
>   		__u32		uring_cmd_flags;
> +		__u32		getdents_flags;

Looks this is not needed anymore, I'll remove this in next version.

>   	};
>   	__u64	user_data;	/* data to be passed back at completion time */
>   	/* pack this to avoid bogus arm OABI complaints */
> @@ -235,6 +236,7 @@ enum io_uring_op {
>   	IORING_OP_URING_CMD,
>   	IORING_OP_SEND_ZC,
>   	IORING_OP_SENDMSG_ZC,
> +	IORING_OP_GETDENTS,
>   
>   	/* this goes last, obviously */
>   	IORING_OP_LAST,
> @@ -273,6 +275,11 @@ enum io_uring_op {
>    */
>   #define SPLICE_F_FD_IN_FIXED	(1U << 31) /* the last bit of __u32 */
>   
> +/*
> + * sqe->getdents_flags
> + */
> +#define IORING_GETDENTS_REWIND	(1U << 0)

ditto

> +
>   /*
>    * POLL_ADD flags. Note that since sqe->poll_events is the flag space, the
>    * command flags for POLL_ADD are stored in sqe->len.
> diff --git a/io_uring/fs.c b/io_uring/fs.c
> index f6a69a549fd4..480f25677fed 100644
> --- a/io_uring/fs.c
> +++ b/io_uring/fs.c
> @@ -47,6 +47,13 @@ struct io_link {
>   	int				flags;
>   };
>   
> +struct io_getdents {
> +	struct file			*file;
> +	struct linux_dirent64 __user	*dirent;
> +	unsigned int			count;
> +	int				flags;

ditto