mufs: optimise memory footprint of write_dirent()

source/fs/mufs/dir.c

@@ -270,9 +270,12 @@ size_t write_dirent(struct mufs_tree *tree,
 {
 	struct mufs *fs = tree->fs;
 	struct flash_dev *dev = fs->dev;
-	char data[1 << dev->log2_block_size];
 	struct mufs_dentry entry;
-	size_t size;
+	size_t block_size = 1 << dev->log2_block_size;
+	uint32_t offset;
+
+	offset = va & ((UINT32_C(1) << dev->log2_block_size) - 1);
+	va = align(va, dev->log2_block_size);
 
 	entry.type = dirent->type;
 	entry.tree.file_size = dirent->tree.file_size;
@@ -280,15 +283,18 @@ size_t write_dirent(struct mufs_tree *tree,
 	entry.tree.depth = dirent->tree.depth;
 	entry.path_len = strlen(dirent->path);
 
-	memcpy(data, &entry, sizeof entry);
-	memcpy(data + sizeof entry, dirent->path, entry.path_len);
-	size = sizeof entry + entry.path_len;
+	if (block_size - offset < sizeof entry + entry.path_len)
+		return 0;
+
+	if (mufs_tree_write(tree, dirent->path, va + offset + sizeof entry,
+		entry.path_len) == 0)
+		return 0;
 
-	if (mufs_tree_write(tree, data, va, size) == 0)
+	if (mufs_tree_write(tree, &entry, va + offset, sizeof entry) == 0)
 		return 0;
 
-	va += sizeof entry + entry.path_len;
-	tree->file_size = max(tree->file_size, va);
+	tree->file_size = max(tree->file_size, va + offset + sizeof entry +
+		entry.path_len);
 
 	if (tree->file_size <= va && mufs_sync_tree(tree) < 0)
 		return 0;