[PATCH liburing] add another helper for probing existing opcodes

[Glauber Costa <glauber@scylladb.com>]

There are situations where one does not have a ring initialized yet, and
yet they may want to know which opcodes are supported before doing so.

We have recently introduced io_uring_get_probe(io_uring*) to do a
similar task when the ring already exists. Because this was committed
recently and this hasn't seen a release, I thought I would just go ahead
and change that to io_uring_get_probe_ring(io_uring*), because I suck at
finding another meaningful name for this case (io_uring_get_probe_noring
sounded way too ugly to me)

A minimal ring is initialized and torn down inside the function.

Signed-off-by: Glauber Costa <glauber@scylladb.com>
---
 src/include/liburing.h |  4 +++-
 src/liburing.map       |  1 +
 src/setup.c            | 15 ++++++++++++++-
 test/probe.c           |  2 +-
 4 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/include/liburing.h b/src/include/liburing.h
index 39db902..aa11282 100644
--- a/src/include/liburing.h
+++ b/src/include/liburing.h
@@ -77,7 +77,9 @@ struct io_uring {
  * return an allocated io_uring_probe structure, or NULL if probe fails (for
  * example, if it is not available). The caller is responsible for freeing it
  */
-extern struct io_uring_probe *io_uring_get_probe(struct io_uring *ring);
+extern struct io_uring_probe *io_uring_get_probe_ring(struct io_uring *ring);
+/* same as io_uring_get_probe_ring, but takes care of ring init and teardown */
+extern struct io_uring_probe *io_uring_get_probe();
 
 static inline int io_uring_opcode_supported(struct io_uring_probe *p, int op)
 {
diff --git a/src/liburing.map b/src/liburing.map
index ac8288a..8daa432 100644
--- a/src/liburing.map
+++ b/src/liburing.map
@@ -73,4 +73,5 @@ LIBURING_0.4 {
 		io_uring_register_personality;
 		io_uring_unregister_personality;
 		io_uring_get_probe;
+		io_uring_get_probe_ring;
 } LIBURING_0.3;
diff --git a/src/setup.c b/src/setup.c
index c03274c..4fc35ea 100644
--- a/src/setup.c
+++ b/src/setup.c
@@ -169,7 +169,7 @@ void io_uring_queue_exit(struct io_uring *ring)
 	close(ring->ring_fd);
 }
 
-struct io_uring_probe *io_uring_get_probe(struct io_uring *ring)
+struct io_uring_probe *io_uring_get_probe_ring(struct io_uring *ring)
 {
 	struct io_uring_probe *probe;
 	int r;
@@ -186,3 +186,16 @@ fail:
 	free(probe);
 	return NULL;
 }
+
+struct io_uring_probe *io_uring_get_probe() {
+	struct io_uring ring;
+	struct io_uring_probe* probe = NULL;
+
+	int r = io_uring_queue_init(2, &ring, 0);
+	if (r < 0)
+		return NULL;
+
+	probe = io_uring_get_probe_ring(&ring);
+	io_uring_queue_exit(&ring);
+	return probe;
+}
diff --git a/test/probe.c b/test/probe.c
index 34f2028..b85b089 100644
--- a/test/probe.c
+++ b/test/probe.c
@@ -45,7 +45,7 @@ static int test_probe_helper(struct io_uring *ring)
 {
 	struct io_uring_probe *p;
 
-	p = io_uring_get_probe(ring);
+	p = io_uring_get_probe_ring(ring);
 	if (!p) {
 		fprintf(stderr, "Failed getting probe data\n");
 		return 1;
-- 
2.20.1