David Young <dyoung@pobox.com> writes:

> Here is a patch for NetBSD that adds an ffs_sync to rw->ro transitions.
> It doesn't make any difference for my problem.

this patch isn't the right thing, a couple of quick comments:

  - ffs_sync is not exactly the same as the full device close/open
    that happens on unmount/mount

  - there's already an ffs_flushfiles in that path, which will attempt
    to flush out and reclaim vnodes.  If any are in use, it should
    return EBUSY.  You can turn on the vfs.ffs.busyprt sysctl to see
    what it might be skipping.

Darrin