The function gfs_pio_datasync copies data on
memory of the gf, and waits for the I/O
to complete before returning. It does nod update metadtata stat
information, while another function
gfs_pio_sync updates the metadata in addition to
the contents.
RETURN VALUES
NULL
The function terminated successfully.
GFARM_ERR_NO_MEMORY
Insufficient memory was available.
Others
An error except the above occurred. The reason is shown by its
pointed strings.