mufs: extend tree in mufs_tree_write() rather than mufs_do_write()

source/fs/mufs/tree.c

@@ -256,9 +256,6 @@ static size_t mufs_do_write(struct mufs_tree *tree,
 	va = align(va, dev->log2_block_size);
 	len = min(len, (UINT32_C(1) << dev->log2_block_size) - offset);
 
-	if (mufs_extend_tree(tree, 1) < 0)
-		return 0;
-
 	if (mufs_alloc_page(tree, &page, va) < 0)
 		return 0;
 
@@ -272,6 +269,9 @@ size_t mufs_tree_write(struct mufs_tree *tree, void *data,
 	uint8_t *buf = data;
 	size_t ret, nbytes = 0;
 
+	if (mufs_extend_tree(tree, 1) < 0)
+		return 0;
+
 	while (len) {
 		if ((ret = mufs_do_write(tree, buf, va, len)) == 0)
 			return nbytes;