Processes freeze when they try to access particular ZFS directory

[Chris Stankevitz]

I have a FreeBSD 10.1-RELEASE-p13 machine on an air-gapped network. 
When I perform an 'ls -l' on a particular directory (with ~5 files), the 
ls process freezes and does not return.  kill -9 and closing the shell 
doesn't make the process go away either.

Samba has some of these files open and I suspect the samba processes are 
stuck too.

Something similar happened a month ago that required a "pull the plug" 
reboot as the FS was in such a state that it would not unmount.

Please [quickly -- i'll probably have to reboot soon] let me know if you 
would like to see any debug output.

Last line of 'truss ls -l' (before the freeze) is:

lpathconf(...) = 1 (0x1)

The frozen 'ls -l' process is in the DX+ state.

zpool status is happy

The pool has a 24 TB capacity.  The problem FS is using 1TB with ~1.5 
million files.

Chris