gfs_pio_write() writes up to size bytes to the file gf from the buffer starting at buffer. It returns the number of bytes written to the address pointed by np.
The function terminated successfully.
gf does not specify a regular file.
The file descripter specified by gfp is not a valid or is not open for writing.
The file system node has no room to store data
There is no available file system node.
Insufficient memory was available.
An error except the above occurred. The reason is shown by gfarm_error_string(3).