Building with the attached random configuration file,

warning: (HWPOISON_INJECT && MEM_SOFT_DIRTY && IDLE_PAGE_TRACKING)
selects PROC_PAGE_MONITOR which has unmet direct dependencies (PROC_FS
&& MMU)

mm/built-in.o: In function `page_ext_init_flatmem':
(.init.text+0x30ef): undefined reference to `page_idle_ops'
mm/built-in.o: In function `page_ext_init_flatmem':
(.init.text+0x3172): undefined reference to `page_idle_ops'