Re: [PATCH] io_uring/net: use REQ_F_IMPORT_BUFFER for send_zc

[Pavel Begunkov]

On 3/24/25 15:11, Caleb Sander Mateos wrote:
> Instead of a bool field in struct io_sr_msg, use REQ_F_IMPORT_BUFFER to
> track whether io_send_zc() has already imported the buffer. This flag
> already serves a similar purpose for sendmsg_zc and {read,write}v_fixed.
>
> Signed-off-by: Caleb Sander Mateos <csander@xxxxxxxxxxxxxxx>
> Suggested-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
> ---
>   include/linux/io_uring_types.h | 5 ++++-
>   io_uring/net.c                 | 8 +++-----
>   2 files changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
> index c17d2eedf478..699e2c0895ae 100644
> --- a/include/linux/io_uring_types.h
> +++ b/include/linux/io_uring_types.h
> @@ -583,11 +583,14 @@ enum {
>   	REQ_F_BUFFERS_COMMIT	= IO_REQ_FLAG(REQ_F_BUFFERS_COMMIT_BIT),
>   	/* buf node is valid */
>   	REQ_F_BUF_NODE		= IO_REQ_FLAG(REQ_F_BUF_NODE_BIT),
>   	/* request has read/write metadata assigned */
>   	REQ_F_HAS_METADATA	= IO_REQ_FLAG(REQ_F_HAS_METADATA_BIT),
> -	/* resolve padded iovec to registered buffers */
> +	/*
> +	 * For vectored fixed buffers, resolve iovec to registered buffers.
> +	 * For SEND_ZC, whether to import buffers (i.e. the first issue).
> +	 */
>   	REQ_F_IMPORT_BUFFER	= IO_REQ_FLAG(REQ_F_IMPORT_BUFFER_BIT),
>   };
>   
>   typedef void (*io_req_tw_func_t)(struct io_kiocb *req, io_tw_token_t tw);
>   
> diff --git a/io_uring/net.c b/io_uring/net.c
> index c87af980b98e..b221abe2600e 100644
> --- a/io_uring/net.c
> +++ b/io_uring/net.c
> @@ -75,11 +75,10 @@ struct io_sr_msg {
>   	unsigned			nr_multishot_loops;
>   	u16				flags;
>   	/* initialised and used only by !msg send variants */
>   	u16				buf_group;
>   	bool				retry;
> -	bool				imported; /* only for io_send_zc */
>   	void __user			*msg_control;
>   	/* used only for send zerocopy */
>   	struct io_kiocb 		*notif;
>   };
>   
> @@ -1305,12 +1304,11 @@ int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>   	struct io_ring_ctx *ctx = req->ctx;
>   	struct io_kiocb *notif;
>   
>   	zc->done_io = 0;
>   	zc->retry = false;
> -	zc->imported = false;
> -	req->flags |= REQ_F_POLL_NO_LAZY;
> +	req->flags |= REQ_F_POLL_NO_LAZY | REQ_F_IMPORT_BUFFER;

This function is shared with sendmsg_zc, so if we set it here,
it'll trigger io_import_reg_vec() in io_sendmsg_zc() even for
non register buffer request.

>   
>   	if (unlikely(READ_ONCE(sqe->__pad2[0]) || READ_ONCE(sqe->addr3)))
>   		return -EINVAL;
>   	/* we don't support IOSQE_CQE_SKIP_SUCCESS just yet */
>   	if (req->flags & REQ_F_CQE_SKIP)
> @@ -1447,12 +1445,12 @@ int io_send_zc(struct io_kiocb *req, unsigned int issue_flags)
>   	if (unlikely(!sock))
>   		return -ENOTSOCK;
>   	if (!test_bit(SOCK_SUPPORT_ZC, &sock->flags))
>   		return -EOPNOTSUPP;
>   
> -	if (!zc->imported) {
> -		zc->imported = true;
> +	if (req->flags & REQ_F_IMPORT_BUFFER) {
> +		req->flags &= ~REQ_F_IMPORT_BUFFER;
>   		ret = io_send_zc_import(req, issue_flags);
>   		if (unlikely(ret))
>   			return ret;
>   	}
>   

--
Pavel Begunkov