generic_shutdown_super — 
     common helper for ->kill_sb
 
| void generic_shutdown_super ( | struct super_block * sb ); | 
   generic_shutdown_super does all fs-independent work on superblock
   shutdown.  Typical ->kill_sb should pick all fs-specific objects
   that need destruction out of superblock, call generic_shutdown_super
   and release aforementioned objects.  Note: dentries and inodes _are_
   taken care of and do not need specific handling.
   
Upon calling this function, the filesystem may no longer alter or rearrange the set of dentries belonging to this super_block, nor may it change the attachments of dentries to inodes.