Fragment Caching

I'm using regular expressions in expire_fragment function. Using it
this way appears to stat EVERY single file in the entire cache
directory. I thought that it was only expiring fragments from the
controller it was called from, this appears not to be the case. This
of course leads to SIGNIFICANT performance issues once you get a
sizable number of files in your cache directory and could potentially
expire fragments from another controller that you would not want to
without realizing it. From looking at the source from cache.rb it
looks trivial to build a plugin to take a controller as an option and
only stat files from that path. I'm a relative newbie however and just
wanted to make sure I was using it right way and not missing some rails
convention for specifying the path that the regular expression applies
to. Any insight would be appreciated!