nfs and cifs on Linux currently have a mount parameter "actimeo" to
control metadata (attribute) caching but cifs does not have additional
mount parameters to allow distinguishing between caching directory
metadata (e.g. needed to revalidate paths) and that for files.

Add new mount parameter "acdirmax" to allow caching metadata for
directories more loosely than file data.  NFS adjusts metadata
caching from acdirmin to acdirmax (and another two mount parms
for files) but to reduce complexity, it is safer to just introduce
the one mount parm to allow caching directories longer (30 seconds
vs. the 1 second default for file metadata) which is still more
conservative than other Linux filesystems (e.g. NFS sets acdirmax
to 60 seconds)

-- 
Thanks,

Steve