zfs dataset and hanging getdirentries() on it

[Eugene M. Zheganin]

Hi.

I have a funny zfs dataset on a recent stable, which listing takes 
several minutes. In the same time

- it runs last available pool version with all available feature flags 
enabled (however, problem manifested itself on a one year old stable)
- it's an old /tmp directory
- it used to hold 2.5 millions of files (operational error from nagios)
- now it's empty
- zpool status shows no errors
- scrub found no errors
- ktrace shows it's getdirentries() that is waiting for something
- ps shows zio->io_(trimmed)wchan state

Does someone take a look into this, in case this is some kind of rare 
bug (and I suppose it is) ?
If not, I will just delete it - I've already recreated /tmp and renamed 
old one.

Eugene.