SUNRPC: Add a /sys/kernel/debug/fail_sunrpc/ directory

This directory will contain a set of administrative controls for
enabling error injection for kernel RPC consumers.

Signed-off-by: Chuck Lever <[e-mail]>

lib/Kconfig.debug

···
 	  and to test how the mmc host driver handles retries from
 	  the block device.
 
+config FAIL_SUNRPC
+	bool "Fault-injection capability for SunRPC"
+	depends on FAULT_INJECTION_DEBUG_FS && SUNRPC_DEBUG
+	help
+	  Provide fault-injection capability for SunRPC and
+	  its consumers.
+
 config FAULT_INJECTION_STACKTRACE_FILTER
 	bool "stacktrace filter for fault-injection capabilities"
 	depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT

net/sunrpc/debugfs.c

···
 #include <linux/debugfs.h>
 #include <linux/sunrpc/sched.h>
 #include <linux/sunrpc/clnt.h>
+
 #include "netns.h"
+#include "fail.h"
 
 static struct dentry *topdir;
 static struct dentry *rpc_clnt_dir;
···
 	.release	= fault_release,
 };
 
+#if IS_ENABLED(CONFIG_FAIL_SUNRPC)
+struct fail_sunrpc_attr fail_sunrpc = {
+	.attr			= FAULT_ATTR_INITIALIZER,
+};
+EXPORT_SYMBOL_GPL(fail_sunrpc);
+#endif
+
 void __exit
 sunrpc_debugfs_exit(void)
 {
···
 
 	debugfs_create_file("disconnect", S_IFREG | 0400, rpc_fault_dir, NULL,
 			    &fault_disconnect_fops);
+
+#if IS_ENABLED(CONFIG_FAIL_SUNRPC)
+	fault_create_debugfs_attr("fail_sunrpc", NULL,
+				  &fail_sunrpc.attr);
+#endif
 }

net/sunrpc/fail.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2021, Oracle. All rights reserved.
+ */
+
+#ifndef _NET_SUNRPC_FAIL_H_
+#define _NET_SUNRPC_FAIL_H_
+
+#include <linux/fault-inject.h>
+
+#if IS_ENABLED(CONFIG_FAULT_INJECTION)
+
+struct fail_sunrpc_attr {
+	struct fault_attr	attr;
+};
+
+extern struct fail_sunrpc_attr fail_sunrpc;
+
+#endif /* CONFIG_FAULT_INJECTION */
+
+#endif /* _NET_SUNRPC_FAIL_H_ */