Fdatasync is similar to fsync(), but does not flush modified metadata unless that metadata is needed in order to allow a subsequent data retrieval to be correctly handled.

IsDirWriteable checks if dir is writable by writing and removing a file to dir.

Preallocate tries to allocate the space for given file.

ReadDir returns the filenames in the given directory in sorted order.

TouchDirAll is similar to os.MkdirAll.