staging: lustre: mdt: race between open and migrate

staging: lustre: mdt: race between open and migrate

During intent open, it was found that if the parent has
been migrated to another MDT, it should retry the open
request with the new object, so it needs to keep the
old object in the orphan list, which will be cleanup
during next recovery. Note: if the client still using
the old FID after next recovery, it will return -ENOENT
for the application. Also enqueue the lease lock of
the migrating file, then compare the lease before
migration to make sure no other clients open the file
at the same time.

Signed-off-by: wang di <di.wang@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6475
Reviewed-on: http://review.whamcloud.com/14497
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>