[PATCHv5 1/4] liburing: provide uring_cmd prep function

[Keith Busch <kbusch@meta.com>]

From: Keith Busch <kbusch@kernel.org>

The rw prep doesn't clear __pad1, which is a reserved field for
uring_cmd. If a prior submission in that entry did use that field, the
uring_cmd will fail the kernel's checks.

Also, the nvme uring_cmd tests had a couple places setting the sqe addr
and length, which are unused fields for the nvme uring_cmds, so they
shouldn't have been doing that, though had been checking these, so it
didn't cause any errors.

Provide a helper function specific to the uring_cmd preparation.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 src/include/liburing.h      | 19 +++++++++++++++----
 test/io_uring_passthrough.c | 14 ++++----------
 2 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/src/include/liburing.h b/src/include/liburing.h
index c80bffd3..f7af20aa 100644
--- a/src/include/liburing.h
+++ b/src/include/liburing.h
@@ -1517,6 +1517,19 @@ IOURINGINLINE void io_uring_prep_socket_direct_alloc(struct io_uring_sqe *sqe,
 	__io_uring_set_target_fixed_file(sqe, IORING_FILE_INDEX_ALLOC - 1);
 }
 
+IOURINGINLINE void io_uring_prep_uring_cmd(struct io_uring_sqe *sqe,
+					   int cmd_op,
+					   int fd)
+	LIBURING_NOEXCEPT
+{
+	sqe->opcode = (__u8) IORING_OP_URING_CMD;
+	sqe->fd = fd;
+	sqe->cmd_op = cmd_op;
+	sqe->__pad1 = 0;
+	sqe->addr = 0ul;
+	sqe->len = 0;
+}
+
 /*
  * Prepare commands for sockets
  */
@@ -1529,11 +1542,10 @@ IOURINGINLINE void io_uring_prep_cmd_sock(struct io_uring_sqe *sqe,
 					  int optlen)
 	LIBURING_NOEXCEPT
 {
-	io_uring_prep_rw(IORING_OP_URING_CMD, sqe, fd, NULL, 0, 0);
+	io_uring_prep_uring_cmd(sqe, cmd_op, fd);
 	sqe->optval = (unsigned long) (uintptr_t) optval;
 	sqe->optname = optname;
 	sqe->optlen = optlen;
-	sqe->cmd_op = cmd_op;
 	sqe->level = level;
 }
 
@@ -1607,8 +1619,7 @@ IOURINGINLINE void io_uring_prep_cmd_discard(struct io_uring_sqe *sqe,
 					     uint64_t offset, uint64_t nbytes)
 	LIBURING_NOEXCEPT
 {
-	io_uring_prep_rw(IORING_OP_URING_CMD, sqe, fd, 0, 0, 0);
-	sqe->cmd_op = BLOCK_URING_CMD_DISCARD;
+	io_uring_prep_uring_cmd(sqe, BLOCK_URING_CMD_DISCARD, fd);
 	sqe->addr = offset;
 	sqe->addr3 = nbytes;
 }
diff --git a/test/io_uring_passthrough.c b/test/io_uring_passthrough.c
index beaa81ad..26051710 100644
--- a/test/io_uring_passthrough.c
+++ b/test/io_uring_passthrough.c
@@ -148,11 +148,9 @@ static int __test_io(const char *file, struct io_uring *ring, int tc, int read,
 		if (async)
 			sqe->flags |= IOSQE_ASYNC;
 		if (nonvec)
-			sqe->cmd_op = NVME_URING_CMD_IO;
+			io_uring_prep_uring_cmd(sqe, NVME_URING_CMD_IO, use_fd);
 		else
-			sqe->cmd_op = NVME_URING_CMD_IO_VEC;
-		sqe->fd = use_fd;
-		sqe->opcode = IORING_OP_URING_CMD;
+			io_uring_prep_uring_cmd(sqe, NVME_URING_CMD_IO_VEC, use_fd);
 		if (do_fixed)
 			sqe->uring_cmd_flags |= IORING_URING_CMD_FIXED;
 		sqe->user_data = ((uint64_t)offset << 32) | i;
@@ -328,9 +326,7 @@ static int test_invalid_passthru_submit(const char *file)
 	}
 
 	sqe = io_uring_get_sqe(&ring);
-	io_uring_prep_read(sqe, fd, vecs[0].iov_base, vecs[0].iov_len, 0);
-	sqe->cmd_op = NVME_URING_CMD_IO;
-	sqe->opcode = IORING_OP_URING_CMD;
+	io_uring_prep_uring_cmd(sqe, NVME_URING_CMD_IO, fd);
 	sqe->user_data = 1;
 	cmd = (struct nvme_uring_cmd *)sqe->cmd;
 	memset(cmd, 0, sizeof(struct nvme_uring_cmd));
@@ -401,10 +397,8 @@ static int test_io_uring_submit_enters(const char *file)
 		__u32 nlb;
 
 		sqe = io_uring_get_sqe(&ring);
-		io_uring_prep_readv(sqe, fd, &vecs[i], 1, offset);
+		io_uring_prep_uring_cmd(sqe, NVME_URING_CMD_IO, fd);
 		sqe->user_data = i;
-		sqe->opcode = IORING_OP_URING_CMD;
-		sqe->cmd_op = NVME_URING_CMD_IO;
 		cmd = (struct nvme_uring_cmd *)sqe->cmd;
 		memset(cmd, 0, sizeof(struct nvme_uring_cmd));
 
-- 
2.47.3