[PATCH] io_uring: add IORING_OP_NOP_FAIL

[Ming Lei <ming.lei@redhat.com>]

Add IORING_OP_NOP_FAIL so that it is easy to inject failure from
userspace.

Like IORING_OP_NOP, the main use case is test, and it is very helpful
for covering failure handling code in io_uring core change.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 include/uapi/linux/io_uring.h |  2 ++
 io_uring/nop.c                | 27 +++++++++++++++++++++++++++
 io_uring/nop.h                |  3 +++
 io_uring/opdef.c              |  9 +++++++++
 4 files changed, 41 insertions(+)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 922f29b07ccc..18e58477e0f0 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -72,6 +72,7 @@ struct io_uring_sqe {
 		__u32		waitid_flags;
 		__u32		futex_flags;
 		__u32		install_fd_flags;
+		__s32		nop_fail_res;
 	};
 	__u64	user_data;	/* data to be passed back at completion time */
 	/* pack this to avoid bogus arm OABI complaints */
@@ -259,6 +260,7 @@ enum io_uring_op {
 	IORING_OP_FUTEX_WAITV,
 	IORING_OP_FIXED_FD_INSTALL,
 	IORING_OP_FTRUNCATE,
+	IORING_OP_NOP_FAIL,
 
 	/* this goes last, obviously */
 	IORING_OP_LAST,
diff --git a/io_uring/nop.c b/io_uring/nop.c
index d956599a3c1b..c30547e53b5c 100644
--- a/io_uring/nop.c
+++ b/io_uring/nop.c
@@ -10,6 +10,12 @@
 #include "io_uring.h"
 #include "nop.h"
 
+struct io_nop_fail {
+	/* NOTE: kiocb has the file as the first member, so don't do it here */
+	struct file	*file;
+	int		res;
+};
+
 int io_nop_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	return 0;
@@ -23,3 +29,24 @@ int io_nop(struct io_kiocb *req, unsigned int issue_flags)
 	io_req_set_res(req, 0, 0);
 	return IOU_OK;
 }
+
+int io_nop_fail_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_nop_fail *nf = io_kiocb_to_cmd(req, struct io_nop_fail);
+
+	nf->res = READ_ONCE(sqe->nop_fail_res);
+	return 0;
+}
+
+/*
+ * IORING_OP_NOP just posts a completion event, nothing else.
+ */
+int io_nop_fail(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_nop_fail *nf = io_kiocb_to_cmd(req, struct io_nop_fail);
+
+	if (nf->res < 0)
+		req_set_fail(req);
+	io_req_set_res(req, nf->res, 0);
+	return IOU_OK;
+}
diff --git a/io_uring/nop.h b/io_uring/nop.h
index 97f1535c9dec..ef40d3b15899 100644
--- a/io_uring/nop.h
+++ b/io_uring/nop.h
@@ -2,3 +2,6 @@
 
 int io_nop_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 int io_nop(struct io_kiocb *req, unsigned int issue_flags);
+
+int io_nop_fail_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_nop_fail(struct io_kiocb *req, unsigned int issue_flags);
diff --git a/io_uring/opdef.c b/io_uring/opdef.c
index 92b657a063a0..eadc5a12ee06 100644
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c
@@ -56,6 +56,12 @@ const struct io_issue_def io_issue_defs[] = {
 		.prep			= io_nop_prep,
 		.issue			= io_nop,
 	},
+	[IORING_OP_NOP_FAIL] = {
+		.audit_skip		= 1,
+		.iopoll			= 1,
+		.prep			= io_nop_fail_prep,
+		.issue			= io_nop_fail,
+	},
 	[IORING_OP_READV] = {
 		.needs_file		= 1,
 		.unbound_nonreg_file	= 1,
@@ -506,6 +512,9 @@ const struct io_cold_def io_cold_defs[] = {
 	[IORING_OP_NOP] = {
 		.name			= "NOP",
 	},
+	[IORING_OP_NOP_FAIL] = {
+		.name			= "NOP_FAIL",
+	},
 	[IORING_OP_READV] = {
 		.name			= "READV",
 		.cleanup		= io_readv_writev_cleanup,
-- 
2.44.0