root@u2:/usr/src/linux~# LANG=C make
  CHK     include/linux/version.h
  CHK     include/generated/utsrelease.h
  CALL    scripts/checksyscalls.sh
  CHK     include/generated/compile.h
  CC      mm/migrate.o
mm/migrate.c: In function 'unmap_and_move_huge_page':
mm/migrate.c:838: error: implicit declaration of function 'drop_anon_vma'
make[1]: *** [mm/migrate.o] Error 1
make: *** [mm] Error 2