[PATCH] io_uring: disable multishot recvmsg

[PATCH] io_uring: disable multishot recvmsg

[Dylan Yudaken]

recvmsg has semantics that do not make it trivial to extend to
multishot. Specifically it has user pointers and returns data in the
original parameter. In order to make this API useful these will need to be
somehow included with the provided buffers.

For now remove multishot for recvmsg as it is not useful.

Signed-off-by: Dylan Yudaken <dylany@fb.com>
---
 io_uring/net.c | 29 ++++++++++-------------------
 1 file changed, 10 insertions(+), 19 deletions(-)

diff --git a/io_uring/net.c b/io_uring/net.c
index cb08a4b62840..6679069eeef1 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -409,6 +409,8 @@ int io_recvmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	if (sr->msg_flags & MSG_ERRQUEUE)
 		req->flags |= REQ_F_CLEAR_POLLIN;
 	if (sr->flags & IORING_RECV_MULTISHOT) {
+		if (req->opcode == IORING_OP_RECVMSG)
+			return -EINVAL;
 		if (!(req->flags & REQ_F_BUFFER_SELECT))
 			return -EINVAL;
 		if (sr->msg_flags & MSG_WAITALL)
@@ -435,7 +437,7 @@ static inline void io_recv_prep_retry(struct io_kiocb *req)
 }
 
 /*
- * Finishes io_recv and io_recvmsg.
+ * Finishes io_recv
  *
  * Returns true if it is actually finished, or false if it should run
  * again (for multishot).
@@ -477,7 +479,6 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
 	unsigned flags;
 	int ret, min_ret = 0;
 	bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
-	size_t len = sr->len;
 
 	sock = sock_from_file(req->file);
 	if (unlikely(!sock))
@@ -496,17 +497,16 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
 	    (sr->flags & IORING_RECVSEND_POLL_FIRST))
 		return io_setup_async_msg(req, kmsg);
 
-retry_multishot:
 	if (io_do_buffer_select(req)) {
 		void __user *buf;
 
-		buf = io_buffer_select(req, &len, issue_flags);
+		buf = io_buffer_select(req, &sr->len, issue_flags);
 		if (!buf)
 			return -ENOBUFS;
 		kmsg->fast_iov[0].iov_base = buf;
-		kmsg->fast_iov[0].iov_len = len;
+		kmsg->fast_iov[0].iov_len = sr->len;
 		iov_iter_init(&kmsg->msg.msg_iter, READ, kmsg->fast_iov, 1,
-				len);
+				sr->len);
 	}
 
 	flags = sr->msg_flags;
@@ -518,15 +518,8 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
 	kmsg->msg.msg_get_inq = 1;
 	ret = __sys_recvmsg_sock(sock, &kmsg->msg, sr->umsg, kmsg->uaddr, flags);
 	if (ret < min_ret) {
-		if (ret == -EAGAIN && force_nonblock) {
-			ret = io_setup_async_msg(req, kmsg);
-			if (ret == -EAGAIN && (req->flags & IO_APOLL_MULTI_POLLED) ==
-					       IO_APOLL_MULTI_POLLED) {
-				io_kbuf_recycle(req, issue_flags);
-				return IOU_ISSUE_SKIP_COMPLETE;
-			}
-			return ret;
-		}
+		if (ret == -EAGAIN && force_nonblock)
+			return io_setup_async_msg(req, kmsg);
 		if (ret == -ERESTARTSYS)
 			ret = -EINTR;
 		if (ret > 0 && io_net_retry(sock, flags)) {
@@ -554,10 +547,8 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
 	if (kmsg->msg.msg_inq)
 		cflags |= IORING_CQE_F_SOCK_NONEMPTY;
 
-	if (!io_recv_finish(req, &ret, cflags))
-		goto retry_multishot;
-
-	return ret;
+	io_req_set_res(req, ret, cflags);
+	return IOU_OK;
 }
 
 int io_recv(struct io_kiocb *req, unsigned int issue_flags)

base-commit: d641b3a4a25e8c471d0240dcb6c78efebd12f366
-- 
2.30.2

Re: [PATCH] io_uring: disable multishot recvmsg

[Jens Axboe]

On Mon, 4 Jul 2022 07:01:06 -0700, Dylan Yudaken wrote:
> recvmsg has semantics that do not make it trivial to extend to
> multishot. Specifically it has user pointers and returns data in the
> original parameter. In order to make this API useful these will need to be
> somehow included with the provided buffers.
> 
> For now remove multishot for recvmsg as it is not useful.
> 
> [...]

Applied, thanks!

[1/1] io_uring: disable multishot recvmsg
      commit: abbbc92e2a398a6f8d50ed39f8a9efbd87edfdff

Best regards,
-- 
Jens Axboe