xfs freeze/umount problem

[David Greaves <david@dgreaves.com>]

David Chinner wrote:
 > FWIW, I'm on record stating that "sync" is not sufficient to quiesce an XFS
 > filesystem for a suspend/resume to work safely and have argued that the only
 > safe thing to do is freeze the filesystem before suspend and thaw it after
 > resume.

Whilst testing a potential bug in another thread I accidentally found that 
unmounting a filesystem that I'd just frozen would hang.

As the saying goes: "Well, duh!!"

I could eventually run an unfreeze but the mount was still hung. This lead to an 
unclean shutdown.

OK, it may not be bright but it seems like this shouldn't happen; umount should 
either unfreeze and work or fail ("Attempt to umount a frozen filesystem.") if 
the fs is frozen.

Is this a kernel bug/misfeature or a (u)mount one?
Suggestions as to the best place to report it if not in the cc's?

David