Hi Olga,
Currently the source's export is mounted and unmounted on every
inter-server copy operation. This causes unnecessary overhead
for each copy.
This patch series is an enhancement to allow the export to remain
mounted for a configurable period (default to 15 minutes). If the
export is not being used for the configured time it will be unmounted
by a delayed task. If it's used again then its expiration time is
extended for another period.
Since mount and unmount are no longer done on each copy request,
this overhead is no longer used to decide whether the copy should
be done with inter-server copy or generic copy. The threshold is
now a module configuration parameter, default to 16MB.
-Dai
v2: fix compiler warning of missing prototype.
v3: remove the used of semaphore.
eliminated all RPC calls for subsequence mount by allowing
all exports from one server to share one vfsmount.
make inter-server threshold a module configuration parameter.
