smb 3.1.1 client dir lease performance

[Steve French]

Bharath,
I noticed that with your patch we are caching directories (when server
supports directory leases) well for successive readdirs which is a
great perf improvement but I also noticed that they time out at 30
seconds from when the first readdir was issued (when the dir lease was
first acquired) and not delayed if the directory is requeried every
few seconds.

Thoughts about bumping the timeout on a directory lease
experimentation to when it was last accessed instead of when it was
acquired?

I also noticed that when we hit the limit on max_cached_dirs (16 by
default) instead of evicting the oldest entries in the cache to use
the newest dir leases we give up adding cached_dir for that
when we hit the limit, even though some of the older dir leases in the
cache may be about to expire?  Maybe we should replace the oldest
entry in dir cache with one from newest dir lease

Thoughts?
-- 
Thanks,

Steve