orangefs: add orangefs_revalidate_mapping

This is modeled after NFS, except our method is different.  We use a
simple timer to determine whether to invalidate the page cache.  This
is bound to perform.

This addes a sysfs parameter cache_timeout_msecs which controls the time
between page cache invalidations.

Signed-off-by: Martin Brandenburg <[email protected]>
Signed-off-by: Mike Marshall <[email protected]>
5 files changed