mufs: add mufs_extend_tree() to extend the depth of a file tree

source/fs/mufs/tree.c

@@ -95,3 +95,24 @@ void mufs_free_page(struct mufs *fs, struct mufs_tree *tree, uint32_t va)
 {
 	mufs_do_free_page(fs, tree->root, tree->depth, va);
 }
+
+int mufs_extend_tree(struct mufs *fs, struct mufs_tree *tree, uint8_t depth)
+{
+	uint32_t root;
+
+	for (; tree->depth < depth; ++tree->depth) {
+		if (mufs_alloc_block(fs, &root) < 0)
+			return -1;
+
+		if (!root)
+			continue;
+
+		if (flash_write(fs->dev, root << fs->dev->log2_block_size, &tree->root,
+			sizeof tree->root) == 0) {
+			mufs_free_block(fs, root);
+			return -1;
+		}
+	}
+
+	return 0;
+}

source/fs/mufs/tree.h

@@ -5,3 +5,4 @@ int mufs_lookup_page(struct mufs *fs, struct mufs_tree *tree, uint32_t *page,
 int mufs_alloc_page(struct mufs *fs, struct mufs_tree *tree, uint32_t *page,
 	uint32_t va);
 void mufs_free_page(struct mufs *fs, struct mufs_tree *tree, uint32_t va);
+int mufs_extend_tree(struct mufs *fs, struct mufs_tree *tree, uint8_t depth);