zfs, a directory that used to hold lot of files and listing pause

[Pete French]

Have ignored this thread untiul now, but I observed the same behaviour
on mysystems over the last week or so. In my case its an exim spool
directory, which was hugely full as some point (thousands of
files) and now takes an awfully long time to open and list. I delet
and remake them and the problem goes away, but I belive it is the same thing.

I am running 10.3-STABLE, r303832

-pete.