"segno" is the argument for the function, not "log" and "seg".
Author: Antonin Houska
Discussion: https://postgr.es/m/11863.
1558361020@spoje.net
* Issue appropriate kind of fsync (if any) for an XLOG output file.
*
* 'fd' is a file descriptor for the XLOG file to be fsync'd.
- * 'log' and 'seg' are for error reporting purposes.
+ * 'segno' is for error reporting purposes.
*/
void
issue_xlog_fsync(int fd, XLogSegNo segno)