Write file is a little bit tricky to implement in fuse. you can`t get source file name in fuse, but only source bytes. so a temp file is needed to be an mediator.
- statfs to confirm disk free size is avaiable
- create
normally create a file with open function, differs from open api in fuse interface which opens an existing file - getattr mainly check permission, and other file info
- write will be called multipal times, write source bytes to remote
- flush will be called once kk- release will be called once
just for myself reference