proc_sysctl: move helper which creates required subdirectories

Move the code which creates the subdirectories for a ctl table
into a helper routine so to make it easier to review. Document
the goal.

This creates no functional changes.
Reviewed-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

fs/proc/proc_sysctl.c

@@ -1283,6 +1283,35 @@ static int insert_links(struct ctl_table_header *head)
 	return err;
 }
 
+/* Find the directory for the ctl_table. If one is not found create it. */
+static struct ctl_dir *sysctl_mkdir_p(struct ctl_dir *dir, const char *path)
+{
+	const char *name, *nextname;
+
+	for (name = path; name; name = nextname) {
+		int namelen;
+		nextname = strchr(name, '/');
+		if (nextname) {
+			namelen = nextname - name;
+			nextname++;
+		} else {
+			namelen = strlen(name);
+		}
+		if (namelen == 0)
+			continue;
+
+		/*
+		 * namelen ensures if name is "foo/bar/yay" only foo is
+		 * registered first. We traverse as if using mkdir -p and
+		 * return a ctl_dir for the last directory entry.
+		 */
+		dir = get_subdir(dir, name, namelen);
+		if (IS_ERR(dir))
+			break;
+	}
+	return dir;
+}
+
 /**
  * __register_sysctl_table - register a leaf sysctl table
  * @set: Sysctl tree to register on
@@ -1334,7 +1363,6 @@ struct ctl_table_header *__register_sysctl_table(
 {
 	struct ctl_table_root *root = set->dir.header.root;
 	struct ctl_table_header *header;
-	const char *name, *nextname;
 	struct ctl_dir *dir;
 	struct ctl_table *entry;
 	struct ctl_node *node;
@@ -1359,29 +1387,9 @@ struct ctl_table_header *__register_sysctl_table(
 	dir->header.nreg++;
 	spin_unlock(&sysctl_lock);
 
-	/* Find the directory for the ctl_table */
-	for (name = path; name; name = nextname) {
-		int namelen;
-		nextname = strchr(name, '/');
-		if (nextname) {
-			namelen = nextname - name;
-			nextname++;
-		} else {
-			namelen = strlen(name);
-		}
-		if (namelen == 0)
-			continue;
-
-		/*
-		 * namelen ensures if name is "foo/bar/yay" only foo is
-		 * registered first. We traverse as if using mkdir -p and
-		 * return a ctl_dir for the last directory entry.
-		 */
-		dir = get_subdir(dir, name, namelen);
-		if (IS_ERR(dir))
-			goto fail;
-	}
-
+	dir = sysctl_mkdir_p(dir, path);
+	if (IS_ERR(dir))
+		goto fail;
 	spin_lock(&sysctl_lock);
 	if (insert_header(dir, header))
 		goto fail_put_dir_locked;