接口实现问题

简单搭建了下，
有些接口如chmod没有实现，修改权限没法使用；
在leveldb里有些数据没有存，对应到fuse挂载时会出现文件的元数据变更；
类似 echo "12" > 1.txt 无法使用；

Start by reproducing the reported chmod failure, missing LevelDB data, FUSE metadata changes, and shell redirection failure. Trace the affected interface implementations and the LevelDB/FUSE paths to determine which behaviors are incomplete. Done means these reported operations work correctly and metadata remains consistent when mounted through FUSE.

Written by the indexing model from the issue text.