Implemented the creation of backing disks

src/entry.c

@@ -237,3 +237,20 @@ uint64_t get_available_space(void) {
 
 	return statbuf.f_bsize * statbuf.f_bavail;
 }
+
+bool reserve_space(uint64_t space) {
+	// While the available space is not enough, delete the oldest entry
+	while (get_available_space() < space) {
+		char* oldest_entry = find_oldest_entry();
+		if (oldest_entry == NULL)
+			return false;
+
+		bool result = delete_entry(oldest_entry);
+		free(oldest_entry);
+
+		if (!result)
+			return false;
+	}
+
+	return true;
+}