sysctl: replace child with an enumeration

This is part of the effort to remove the empty element at the end of
ctl_table structs. "child" was a deprecated elem in this struct and was
being used to differentiate between two types of ctl_tables: "normal"
and "permanently emtpy".

What changed?:
* Replace "child" with an enumeration that will have two values: the
  default (0) and the permanently empty (1). The latter is left at zero
  so when struct ctl_table is created with kzalloc or in a local
  context, it will have the zero value by default. We document the
  new enum with kdoc.
* Remove the "empty child" check from sysctl_check_table
* Remove count_subheaders function as there is no longer a need to
  calculate how many headers there are for every child
* Remove the recursive call to unregister_sysctl_table as there is no
  need to traverse down the child tree any longer
* Add a new SYSCTL_PERM_EMPTY_DIR binary flag
* Remove the last remanence of child from partport/procfs.c

Signed-off-by: Joel Granados <j.granados@samsung.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

1 files changed, 12 insertions, 2 deletions

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 653b66c762b1..59d451f455bf 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -137,7 +137,17 @@ struct ctl_table {
 	void *data;
 	int maxlen;
 	umode_t mode;
-	struct ctl_table *child;	/* Deprecated */
+	/**
+	 * enum type - Enumeration to differentiate between ctl target types
+	 * @SYSCTL_TABLE_TYPE_DEFAULT: ctl target with no special considerations
+	 * @SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY: Used to identify a permanently
+	 *                                       empty directory target to serve
+	 *                                       as mount point.
+	 */
+	enum {
+		SYSCTL_TABLE_TYPE_DEFAULT,
+		SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY
+	} type;
 	proc_handler *proc_handler;	/* Callback for text formatting */
 	struct ctl_table_poll *poll;
 	void *extra1;
@@ -229,7 +239,7 @@ extern int unaligned_enabled;
 extern int unaligned_dump_stack;
 extern int no_unaligned_warning;
 
-extern struct ctl_table sysctl_mount_point[];
+#define SYSCTL_PERM_EMPTY_DIR	(1 << 0)
 
 #else /* CONFIG_SYSCTL */