mufs: optimise memory footprint of read_dirent()

source/fs/mufs/dir.c

@@ -225,31 +225,32 @@ size_t read_dirent(struct mufs *fs, struct mufs_tree *tree,
 	struct mufs_dirent *dirent, uint32_t va)
 {
 	struct flash_dev *dev = fs->dev;
-	char data[1 << dev->log2_block_size];
-	struct mufs_dentry *entry;
+	struct mufs_dentry entry;
+	size_t len, 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);
 
-	if (mufs_tree_read(tree, data, va, 1 << dev->log2_block_size) == 0)
+	if (block_size - offset < sizeof entry)
 		return 0;
 
-	if (offset + sizeof *entry > (UINT32_C(1) << dev->log2_block_size))
+	if (mufs_tree_read(tree, &entry, va + offset, sizeof entry) == 0)
 		return 0;
 
-	entry = (struct mufs_dentry *)(data + offset);
-
-	if (!entry->type)
+	if (!entry.type)
 		return 0;
 
-	if (offset + sizeof *entry + entry->path_len >
-		(UINT32_C(1) << dev->log2_block_size))
+	if (block_size - offset < sizeof entry + entry.path_len)
 		return 0;
 
-	memcpy(dirent->path, data + offset + sizeof *entry, entry->path_len);
-	dirent->path[entry->path_len] = '\0';
-	dirent->type = entry->type;
+	len = min(entry.path_len, sizeof dirent->path - 1);
+
+	if (mufs_tree_read(tree, dirent->path, va + offset + sizeof entry,
+		len) == 0)
+		return 0;
+	dirent->path[len] = '\0';
+	dirent->type = entry.type;
 
 	if (mufs_lookup_page(tree, &dirent->tree.va, va) < 0)
 		return 0;
@@ -257,11 +258,11 @@ size_t read_dirent(struct mufs *fs, struct mufs_tree *tree,
 	dirent->tree.fs = fs;
 	dirent->tree.va = (dirent->tree.va << dev->log2_block_size) + offset +
 		offsetof(struct mufs_dentry, tree);
-	dirent->tree.file_size = entry->tree.file_size;
-	dirent->tree.root = entry->tree.root;
-	dirent->tree.depth = entry->tree.depth;
+	dirent->tree.file_size = entry.tree.file_size;
+	dirent->tree.root = entry.tree.root;
+	dirent->tree.depth = entry.tree.depth;
 
-	return sizeof *entry + entry->path_len;
+	return sizeof entry + entry.path_len;
 }
 
 size_t write_dirent(struct mufs_tree *tree,