gfs_pio_read() attempts to read up to size bytes from the file referenced by gf into the buffer starting at buffer, and returns the number of bytes read to the address pointed by np. On end of file, the number of bytes read is zero.
GFARM_ERR_NO_ERRORThe function terminated successfully.
GFARM_ERR_OPERATION_NOT_PERMITTEDgf does not specify a regular file.
GFARM_ERR_BAD_FILE_DESCRIPTORThe file descripter specified by gf is not a valid or is not open for reading.
GFARM_ERR_NO_FILE_SYSTEM_NODEThere is no available file system node.
GFARM_ERR_NO_MEMORYInsufficient memory was available.
An error except the above occurred. The reason is shown by gfarm_error_string(3).