When changing file ownership mdt_attr_set() should add MDS_INODELOCK_LAYOUT to the ibits (MDS_INODELOCK_UPDATE or MDS_INODELOCK_UPDATE | MDS_INODELOCK_LOOKUP | MDS_INODELOCK_PERM). Semantically it only needs a PR layout lock but I believe that acquiring two separate locks on an object in the same handler is a bad idea.