kern/57632: O_RSYNC|O_DSYNC mismatch what posix says

[yamt9999%gmail.com@localhost]

>Number:         57632
>Category:       kern
>Synopsis:       O_RSYNC|O_DSYNC mismatch what posix says
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Sep 27 05:20:00 +0000 2023
>Originator:     YAMAMOTO Takashi
>Release:        trunk source code around 2023-09
>Organization:
>Environment:
>Description:
posix says:

> If both O_DSYNC and O_RSYNC are set in oflag, all I/O operations
> on the file descriptor shall complete as defined by synchronized
> I/O data integrity completion.

and "Synchronized I/O Data Integrity Completion" should:

> For read, ..... If there were any pending write requests affecting
> the data to be read at the time that the synchronized read
> operation was requested, these write requests are successfully
> transferred prior to reading the data.

netbsd open(2) says:

> Combining O_RSYNC with O_DSYNC only, or specifying it
> without any other synchronized I/O integrity comple-
> tion flag set, has no further effect.

glancing ffs code, it seems to match what the man page says.

>How-To-Repeat:
read doc and code.
>Fix: