kern/41015: vnd driver does not implement DIOCCACHESYNC

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>Number:         41015
>Category:       kern
>Synopsis:       vnd driver does not implement DIOCCACHESYNC
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Mar 14 15:05:00 +0000 2009
>Originator:     Alan Barrett
>Release:        NetBSD 5.99.7
>Organization:
Not much
>Environment:
System: NetBSD 5.99.7 i386
>Description:
        The DIOCCACHESYNC ioctl is undocumented, but wapbl(4) relies on
        it to flush the disk cache.  The vnd driver does not implement
        this ioctl, so crashes while writing to a file system on a vnd
        are likely to encounter more corruptioon than they should.
>How-To-Repeat:
        Code inspection
>Fix:
        A DIOCCACHESYNC at the vnd level should become an fsync(2),
        fdatasync(2), or fsync_range(2), on the underlying file,
        with the FDISKSYNC flag set.