[PATCH 12/13] sysctl: add helper to register empty subdir

[Luis Chamberlain <mcgrof@kernel.org>]

The way to create a subdirectory from the base set of directories
is a bit obscure, so provide a helper which makes this clear, and
also helps remove boiler plate code required to do this work.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
 include/linux/sysctl.h |  7 +++++++
 kernel/sysctl.c        | 16 +++++++++++++---
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 33a471b56345..89c92390e6de 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -208,6 +208,8 @@ extern void register_sysctl_init(const char *path, struct ctl_table *table,
 extern struct ctl_table_header *register_sysctl_subdir(const char *base,
 						       const char *subdir,
 						       struct ctl_table *table);
+extern void register_sysctl_empty_subdir(const char *base, const char *subdir);
+
 void do_sysctl_args(void);
 
 extern int pwrsw_enabled;
@@ -231,6 +233,11 @@ inline struct ctl_table_header *register_sysctl_subdir(const char *base,
 	return NULL;
 }
 
+static inline void register_sysctl_empty_subdir(const char *base,
+						const char *subdir)
+{
+}
+
 static inline struct ctl_table_header *register_sysctl_paths(
 			const struct ctl_path *path, struct ctl_table *table)
 {
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index f9a35325d5d5..460532cd5ac8 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -3188,13 +3188,17 @@ struct ctl_table_header *register_sysctl_subdir(const char *base,
 		{ }
 	};
 
-	if (!table->procname)
+	if (table != sysctl_mount_point && !table->procname)
 		goto out;
 
 	hdr = register_sysctl_table(base_table);
 	if (unlikely(!hdr)) {
-		pr_err("failed when creating subdirectory sysctl %s/%s/%s\n",
-		       base, subdir, table->procname);
+		if (table != sysctl_mount_point)
+			pr_err("failed when creating subdirectory sysctl %s/%s/%s\n",
+			       base, subdir, table->procname);
+		else
+			pr_err("failed when creating empty subddirectory %s/%s\n",
+			       base, subdir);
 		goto out;
 	}
 	kmemleak_not_leak(hdr);
@@ -3202,6 +3206,12 @@ struct ctl_table_header *register_sysctl_subdir(const char *base,
 	return hdr;
 }
 EXPORT_SYMBOL_GPL(register_sysctl_subdir);
+
+void register_sysctl_empty_subdir(const char *base,
+				  const char *subdir)
+{
+	register_sysctl_subdir(base, subdir, sysctl_mount_point);
+}
 #endif /* CONFIG_SYSCTL */
 /*
  * No sense putting this after each symbol definition, twice,
-- 
2.26.2