io_uring/query: return number of available queries

It's useful to know which query opcodes are available. Extend the
structure and return that. It's a trivial change, and even though it can
be painlessly extended later, it'd still require adding a v2 of the
structure.

Signed-off-by: Pavel Begunkov <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

Author: isilence

include/uapi/linux/io_uring/query.h

@@ -36,6 +36,9 @@ struct io_uring_query_opcode {
 	__u64	enter_flags;
 	/* Bitmask of all supported IOSQE_* flags */
 	__u64	sqe_flags;
+	/* The number of available query opcodes */
+	__u32	nr_query_opcodes;
+	__u32	__pad;
 };
 
 #endif

io_uring/query.c

@@ -20,6 +20,8 @@ static ssize_t io_query_ops(void *data)
 	e->ring_setup_flags = IORING_SETUP_FLAGS;
 	e->enter_flags = IORING_ENTER_FLAGS;
 	e->sqe_flags = SQE_VALID_FLAGS;
+	e->nr_query_opcodes = __IO_URING_QUERY_MAX;
+	e->__pad = 0;
 	return sizeof(*e);
 }