sysctl: Remove the now unused ctl_table parent field.

While useful at one time for selinux and the sysctl sanity
checks those users no longer use the parent field and we can
safely remove it.
Inspired-by: Lucian Adrian Grijincu <lucian.grijincu@gmil.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

fs/proc/proc_sysctl.c

@@ -218,16 +218,6 @@ static int sysctl_perm(struct ctl_table_root *root, struct ctl_table *table, int
 	return test_perm(mode, op);
 }
 
-static void sysctl_set_parent(struct ctl_table *parent, struct ctl_table *table)
-{
-	for (; table->procname; table++) {
-		table->parent = parent;
-		if (table->child)
-			sysctl_set_parent(table, table->child);
-	}
-}
-
-
 static struct inode *proc_sys_make_inode(struct super_block *sb,
 		struct ctl_table_header *head, struct ctl_table *table)
 {
@@ -947,10 +937,10 @@ struct ctl_table_header *__register_sysctl_table(
 	header->used = 0;
 	header->unregistering = NULL;
 	header->root = root;
-	sysctl_set_parent(NULL, header->ctl_table);
 	header->count = 1;
 	if (sysctl_check_table(path, table))
 		goto fail;
+
 	spin_lock(&sysctl_lock);
 	header->set = lookup_header_set(root, namespaces);
 	header->attached_by = header->ctl_table;

include/linux/sysctl.h

@@ -1016,7 +1016,6 @@ struct ctl_table
 	int maxlen;
 	umode_t mode;
 	struct ctl_table *child;	/* Deprecated */
-	struct ctl_table *parent;	/* Automatically set */
 	proc_handler *proc_handler;	/* Callback for text formatting */
 	struct ctl_table_poll *poll;
 	void *extra1;