Registration and Superblocks

deactivate_locked_super — drop an active reference to superblock
deactivate_super — drop an active reference to superblock
generic_shutdown_super — common helper for ->kill_sb
sget_userns — find or create a superblock
sget — find or create a superblock
iterate_supers_type — call function for superblocks of given type
get_super — get the superblock of a device
get_super_thawed — get thawed superblock of a device
freeze_super — lock the filesystem and force it into a consistent state
thaw_super — - unlock filesystem