This isn't really an i386 issue, but this is the only list I'm subscribed
to.

I think sys_sync should sync the file systems in the reverse order they were
mounted in, just as vfs_unmountall unmounts them in the reverse order, and
for pretty much the same reason.  That is, you might have one file system
(say, afs) stacked on top of another one (say, ffs).  Does this seem
reasonable?