netdev - [PATCH 4/4] io_uring/net: wire up IORING_CQE_F_SOCK

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Date: Thu,  9 May 2024 12:00:29 -0600
From: Jens Axboe <axboe@...nel.dk>
To: io-uring@...r.kernel.org,
	netdev@...r.kernel.org
Cc: kuba@...nel.org,
	Jens Axboe <axboe@...nel.dk>,
	Norman Maurer <norman_maurer@...le.com>
Subject: [PATCH 4/4] io_uring/net: wire up IORING_CQE_F_SOCK_NONEMPTY for accept

If the given protocol supports passing back whether or not we had more
pending accept post this one, pass back this information to userspace.
This is done by setting IORING_CQE_F_SOCK_NONEMPTY in the CQE flags,
just like we do for recv/recvmsg if there's more data available post
a receive operation.

We can also use this information to be smarter about multishot retry,
as we don't need to do a pointless retry if we know for a fact that
there aren't any more connections to accept.

Suggested-by: Norman Maurer <norman_maurer@...le.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
---
 io_uring/net.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/io_uring/net.c b/io_uring/net.c
index d4d1fc93635c..0a48596429d9 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -1533,6 +1533,7 @@ int io_accept(struct io_kiocb *req, unsigned int issue_flags)
 		.flags = force_nonblock ? O_NONBLOCK : 0,
 	};
 	struct file *file;
+	unsigned cflags;
 	int ret, fd;
 
 	if (!(req->flags & REQ_F_POLLED) &&
@@ -1545,6 +1546,8 @@ int io_accept(struct io_kiocb *req, unsigned int issue_flags)
 		if (unlikely(fd < 0))
 			return fd;
 	}
+	arg.err = 0;
+	arg.is_empty = -1;
 	file = do_accept(req->file, &arg, accept->addr, accept->addr_len,
 			 accept->flags);
 	if (IS_ERR(file)) {
@@ -1573,17 +1576,26 @@ int io_accept(struct io_kiocb *req, unsigned int issue_flags)
 						accept->file_slot);
 	}
 
+	cflags = 0;
+	if (!arg.is_empty)
+		cflags |= IORING_CQE_F_SOCK_NONEMPTY;
+
 	if (!(req->flags & REQ_F_APOLL_MULTISHOT)) {
-		io_req_set_res(req, ret, 0);
+		io_req_set_res(req, ret, cflags);
 		return IOU_OK;
 	}
 
 	if (ret < 0)
 		return ret;
-	if (io_req_post_cqe(req, ret, IORING_CQE_F_MORE))
-		goto retry;
+	if (io_req_post_cqe(req, ret, cflags | IORING_CQE_F_MORE)) {
+		if (cflags & IORING_CQE_F_SOCK_NONEMPTY || arg.is_empty == -1)
+			goto retry;
+		if (issue_flags & IO_URING_F_MULTISHOT)
+			return IOU_ISSUE_SKIP_COMPLETE;
+		return -EAGAIN;
+	}
 
-	io_req_set_res(req, ret, 0);
+	io_req_set_res(req, ret, cflags);
 	return IOU_STOP_MULTISHOT;
 }
 
-- 
2.43.0