io_uring: force multishot CQEs into task context

Multishot are posting CQEs outside of the normal request completion
path, which is usually done from within a task work handler. However, it
might be not the case when it's yet to be polled but has been punted to
io-wq. Make it abide ->task_complete and push it to the polling path
when executed by io-wq.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d7714aaff583096769a0f26e8e747759e556feb1.1670384893.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/net.c

@@ -67,6 +67,19 @@ struct io_sr_msg {
 	struct io_kiocb 		*notif;
 };
 
+static inline bool io_check_multishot(struct io_kiocb *req,
+				      unsigned int issue_flags)
+{
+	/*
+	 * When ->locked_cq is set we only allow to post CQEs from the original
+	 * task context. Usual request completions will be handled in other
+	 * generic paths but multipoll may decide to post extra cqes.
+	 */
+	return !(issue_flags & IO_URING_F_IOWQ) ||
+		!(issue_flags & IO_URING_F_MULTISHOT) ||
+		!req->ctx->task_complete;
+}
+
 int io_shutdown_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	struct io_shutdown *shutdown = io_kiocb_to_cmd(req, struct io_shutdown);
@@ -730,6 +743,9 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
 	    (sr->flags & IORING_RECVSEND_POLL_FIRST))
 		return io_setup_async_msg(req, kmsg, issue_flags);
 
+	if (!io_check_multishot(req, issue_flags))
+		return io_setup_async_msg(req, kmsg, issue_flags);
+
 retry_multishot:
 	if (io_do_buffer_select(req)) {
 		void __user *buf;
@@ -829,6 +845,9 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags)
 	    (sr->flags & IORING_RECVSEND_POLL_FIRST))
 		return -EAGAIN;
 
+	if (!io_check_multishot(req, issue_flags))
+		return -EAGAIN;
+
 	sock = sock_from_file(req->file);
 	if (unlikely(!sock))
 		return -ENOTSOCK;
@@ -1280,6 +1299,8 @@ int io_accept(struct io_kiocb *req, unsigned int issue_flags)
 	struct file *file;
 	int ret, fd;
 
+	if (!io_check_multishot(req, issue_flags))
+		return -EAGAIN;
 retry:
 	if (!fixed) {
 		fd = __get_unused_fd_flags(accept->flags, accept->nofile);