[PATCHv6 1/6] liburing: provide uring_cmd prep function

[Keith Busch <kbusch@meta.com>]

From: Keith Busch <kbusch@kernel.org>

The uring_cmd needs to ensure __pad1 is clear, which is a reserved field
for opcode. If a prior submission for a different opcode at that same
entry did use that field, the command would fail the kernel's checks if
the caller didn't explicity clear it. Provide an init helper for this
opcode.

Also, the nvme uring_cmd tests had a couple places setting the sqe addr
and length, which are unused fields, so they shouldn't have been doing
that, though it had been harmless to do so since the kernel isn't
checking these fields.

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 | 18 ++++++------------
 2 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/src/include/liburing.h b/src/include/liburing.h
index c80bffd3..757c3057 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,
+					   __u32 cmd_op,
+					   int fd)
+	LIBURING_NOEXCEPT
+{
+	sqe->opcode = 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..0442b3a3 100644
--- a/test/io_uring_passthrough.c
+++ b/test/io_uring_passthrough.c
@@ -141,18 +141,16 @@ static int __test_io(const char *file, struct io_uring *ring, int tc, int read,
 
 		if (sqthread)
 			use_fd = 0;
+		if (nonvec)
+			io_uring_prep_uring_cmd(sqe, NVME_URING_CMD_IO, use_fd);
+		else
+			io_uring_prep_uring_cmd(sqe, NVME_URING_CMD_IO_VEC, use_fd);
 		if (fixed && (i & 1))
 			do_fixed = 0;
 		if (do_fixed)
 			sqe->buf_index = 0;
 		if (async)
 			sqe->flags |= IOSQE_ASYNC;
-		if (nonvec)
-			sqe->cmd_op = NVME_URING_CMD_IO;
-		else
-			sqe->cmd_op = NVME_URING_CMD_IO_VEC;
-		sqe->fd = use_fd;
-		sqe->opcode = IORING_OP_URING_CMD;
 		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