Add io_uring_submit_and_wait()

Works just like io_uring_submit(), but also allows retrieving events
(or waiting/polling for them) in the same call.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

3 files changed, 31 insertions, 3 deletions

diff --git a/src/liburing.h b/src/liburing.h
index d7aec73..1b4884a 100644
--- a/src/liburing.h
+++ b/src/liburing.h
@@ -74,6 +74,7 @@ extern int io_uring_peek_cqe(struct io_uring *ring,
 extern int io_uring_wait_cqe(struct io_uring *ring,
 	struct io_uring_cqe **cqe_ptr);
 extern int io_uring_submit(struct io_uring *ring);
+extern int io_uring_submit_and_wait(struct io_uring *ring, unsigned wait_nr);
 extern struct io_uring_sqe *io_uring_get_sqe(struct io_uring *ring);
 
 extern int io_uring_register_buffers(struct io_uring *ring, struct iovec *iovecs,
diff --git a/src/liburing.map b/src/liburing.map
index d940da2..302443c 100644
--- a/src/liburing.map
+++ b/src/liburing.map
@@ -6,6 +6,7 @@ LIBURING_0.1 {
 		io_uring_peek_cqe;
 		io_uring_wait_cqe;
 		io_uring_submit;
+		io_uring_submit_and_wait;
 		io_uring_get_sqe;
 		io_uring_register;
 		io_uring_setup;
diff --git a/src/queue.c b/src/queue.c
index d10fbaf..20d8910 100644
--- a/src/queue.c
+++ b/src/queue.c
@@ -78,7 +78,7 @@ static inline int sq_ring_needs_enter(struct io_uring *ring)
  *
  * Returns number of sqes submitted
  */
-int io_uring_submit(struct io_uring *ring)
+static int __io_uring_submit(struct io_uring *ring, unsigned wait_nr)
 {
 	struct io_uring_sq *sq = &ring->sq;
 	const unsigned mask = *sq->kring_mask;
@@ -124,13 +124,19 @@ int io_uring_submit(struct io_uring *ring)
 		write_barrier();
 	}
 
-	if (sq_ring_needs_enter(ring)) {
+	if (wait_nr || sq_ring_needs_enter(ring)) {
 		unsigned flags = 0;
 
 		if ((*ring->sq.kflags & IORING_SQ_NEED_WAKEUP))
 			flags |= IORING_ENTER_SQ_WAKEUP;
+		if (wait_nr) {
+			if (wait_nr > submitted)
+				wait_nr = submitted;
+			flags |= IORING_ENTER_GETEVENTS;
+		}
 
-		ret = io_uring_enter(ring->ring_fd, submitted, 0, flags, NULL);
+		ret = io_uring_enter(ring->ring_fd, submitted, wait_nr, flags,
+					NULL);
 		if (ret < 0)
 			return -errno;
 	} else
@@ -140,6 +146,26 @@ int io_uring_submit(struct io_uring *ring)
 }
 
 /*
+ * Submit sqes acquired from io_uring_get_sqe() to the kernel.
+ *
+ * Returns number of sqes submitted
+ */
+int io_uring_submit(struct io_uring *ring)
+{
+	return __io_uring_submit(ring, 0);
+}
+
+/*
+ * Like io_uring_submit(), but allows waiting for events as well.
+ *
+ * Returns number of sqes submitted
+ */
+int io_uring_submit_and_wait(struct io_uring *ring, unsigned wait_nr)
+{
+	return __io_uring_submit(ring, wait_nr);
+}
+
+/*
  * Return an sqe to fill. Application must later call io_uring_submit()
  * when it's ready to tell the kernel about it. The caller may call this
  * function multiple times before calling io_uring_submit().