NEX-9200 Improve the scalability of attribute locking in zfs_zget
Reviewed by: Joyce McIntosh <joyce.mcintosh@nexenta.com>
Reviewed by: Sanjay Nadkarni <sanjay.nadkarni@nexenta.com>

*** 245,257 ****
          } \
  
  /*
   * Macros for dealing with dmu_buf_hold
   */
! #define ZFS_OBJ_HASH(obj_num)   ((obj_num) & (ZFS_OBJ_MTX_SZ - 1))
  #define ZFS_OBJ_MUTEX(zfsvfs, obj_num)  \
!         (&(zfsvfs)->z_hold_mtx[ZFS_OBJ_HASH(obj_num)])
  #define ZFS_OBJ_HOLD_ENTER(zfsvfs, obj_num) \
          mutex_enter(ZFS_OBJ_MUTEX((zfsvfs), (obj_num)))
  #define ZFS_OBJ_HOLD_TRYENTER(zfsvfs, obj_num) \
          mutex_tryenter(ZFS_OBJ_MUTEX((zfsvfs), (obj_num)))
  #define ZFS_OBJ_HOLD_EXIT(zfsvfs, obj_num) \
--- 245,257 ----
          } \
  
  /*
   * Macros for dealing with dmu_buf_hold
   */
! #define ZFS_OBJ_HASH(obj_num, table_sz) ((obj_num) & (table_sz - 1))
  #define ZFS_OBJ_MUTEX(zfsvfs, obj_num)  \
!         (&(zfsvfs)->z_hold_mtx[ZFS_OBJ_HASH(obj_num, (zfsvfs)->z_hold_mtx_sz)])
  #define ZFS_OBJ_HOLD_ENTER(zfsvfs, obj_num) \
          mutex_enter(ZFS_OBJ_MUTEX((zfsvfs), (obj_num)))
  #define ZFS_OBJ_HOLD_TRYENTER(zfsvfs, obj_num) \
          mutex_tryenter(ZFS_OBJ_MUTEX((zfsvfs), (obj_num)))
  #define ZFS_OBJ_HOLD_EXIT(zfsvfs, obj_num) \