zpool import speedup

*** 133,144 ****
--- 133,147 ----
  
  #define DMU_OS_IS_L2COMPRESSIBLE(os)    (zfs_mdcomp_disable == B_FALSE)
  
  /* called from zpl */
  int dmu_objset_hold(const char *name, void *tag, objset_t **osp);
+ int dmu_objset_hold_nolock(const char *name, void *tag, objset_t **osp);
  int dmu_objset_own(const char *name, dmu_objset_type_t type,
      boolean_t readonly, void *tag, objset_t **osp);
+ int dmu_objset_own_nolock(const char *name, dmu_objset_type_t type,
+     boolean_t readonly, void *tag, objset_t **osp);
  void dmu_objset_refresh_ownership(objset_t *os, void *tag);
  void dmu_objset_rele(objset_t *os, void *tag);
  void dmu_objset_disown(objset_t *os, void *tag);
  int dmu_objset_from_ds(struct dsl_dataset *ds, objset_t **osp);